Abstract

A single core-offset Mach-Zehnder interferometer (MZI) coated with polyvinyl alcohol (PVA) for simultaneous measurement of relative humidity (RH) and temperature is proposed in this paper. The sensing structure is fabricated by splicing dispersion compensating fiber (DCF) and no-core fiber (NCF) and splicing two single-mode fibers (SMF) at both ends, where the core-offset is located at the splicing of SMF and DCF. A part of the cladding of DCF is etched to excite the high-order cladding mode (LP10), and PVA is coated on the etched area. The refractive index of PVA varies due to the adsorption of water molecules. Therefore, when the ambient relative humidity and temperature change, the change of MZI phase difference causes the wavelength of the resonant dip to shift. The experimental results indicate that the proposed sensor has a sensitivity of 0.256 nm/RH% for RH range of 30%-95%, and a sensitivity of 0.153 nm/℃ for temperature range of 20℃-80℃, respectively. The simultaneous measurement of RH and temperature can be achieved by demodulating the sensitivity coefficient matrix. The proposed sensor has the characteristics of good repeatability, high sensitivity, and good stability, which make it potentially applications for the detection of RH and temperature measurement.

© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

1. Introduction

The real environment is complex and diverse, and a detailed understanding of the environment requires investigation and research of multiple physical quantities. Common physical quantities used to describe the external environment are relative humidity (RH) and temperature, which can profoundly affect human comfort in life. Meanwhile, RH is affected by the temperature in the environment. Therefore, it is necessary to simultaneously measure RH and temperature, which have a pivotal position in biochemistry, agriculture, electronics, instrument manufacturing, food processing, medical care and other fields. Traditional electronic RH and temperature sensors are difficult to be applied in complex environments, such as strong corrosive substances, strong electromagnetic interference and long distances. Optical fiber sensors have excellent characteristics, such as remote sensing, anti-electromagnetic interference, and high sensitivity [1]. Optical fiber sensors are regarded as strong candidates in the field of sensing and have been widely studied and applied, such as temperature [2], RH [3], refractive index [4,5], displacement [6], gas [7], strain [8], etc. Nowadays, for measuring RH and temperature, optical fiber sensors are constantly being presented and manufactured, mainly including Mach-Zehnder interferometer [25], Sagnac interferometer [9], long period gratings [10], Michelson interferometer [11], fiber Bragg gratings (FBG) [12], Fabry-Perot interferometer (FPI) [13], surface plasmon resonance [14], etc.

The main component of optical fiber is silicon dioxide, which has poor sensitivity to RH and temperature. Therefore, coating sensitive materials can effectively improve the detection sensitivity of the optical fiber sensor, such as graphene oxide [3,1416], polyvinyl alcohol (PVA) [1720], GQDs- PVA [10,21], graphene oxide and polyvinyl alcohol (GO-PVA) [22,23], calcium alginate hydrogel [24,25], carbon-nanotube and polyvinyl alcohol [26], SnO2 [27], polyimide [28], chitosan [29], polymethyl methacrylate [30], and Norland optical adhesive (NOA) [31]. The hygroscopic material produces a physical or chemical reaction after adsorbing water molecules, which in turn modulates the light signal. Studies have shown that PVA is a strong hydrophilic material and has good film-forming properties, which make it can be well coated on the surface of the optical fiber with good stability [17]. Therefore, PVA and mixtures containing PVA are widely used in RH sensors [10,1721,22,23,26].

The thermo-optical effect and thermal expansion coefficient of optical fiber is affected by temperature, which cause measurement errors of the optical fiber humidity sensor. To guarantee the accuracy of the sensor, simultaneous measurement of RH and temperature is significant. At present, the commonly used measurement method is to cascade multiple interferometers, or FBG [31,32]. This method is not conducive to distinguishing spectral information and complex production [32]. In this paper, a sensitivity coefficient matrix is gained by tracking the shifts of two resonant dips. Through dual-wavelength matrix demodulation, the sensitivity coefficient matrix is demodulated to implement simultaneous measurement of RH and temperature. This method is always used for multi-parameter measurement [3234].

In this paper, we propose a single core-offset structure MZI coated with PVA to implement simultaneous measurement of RH and temperature. The symmetry of the dual-core offset structure is difficult to grasp during the process of splicing, which will increase the difficulty of production. Therefore, this paper uses a single core-offset structure to avoid this problem. The MZI is fabricated by splicing dispersion compensation fiber (DCF), no-core fiber (NCF) and single-mode fiber (SMF) with the sequence of SMF-DCF-NCF-SMF. Among them, the core-offset occurred at the fusion joint of SMF-DCF. A part of the cladding layer of the DCF is corroded by the hydrofluoric acid solution, and then the higher-order cladding mode is excited. PVA is attached on the corroded cladding layer by a natural deposition method. PVA is a hydrophilic material, which means the adsorption of water molecules can change the refractive index (RI) of the PVA. As a result, the optical fiber field will be affected, and the resonance wavelengths of the MZI shifts. For studying the performance of different materials, GO is also used as a comparison. The experimental results demonstrate that the GO-coated sensor has a sensitivity of 0.122 nm/RH% in RH range of 35%-95%, and a sensitivity of 0.069 nm/℃ in temperature range of 30℃-80℃. The PVA-coated sensor has a sensitivity of 0.256 nm/RH% in RH range of 30%-95%, and a sensitivity of 0.153 nm/℃ in temperature range of 20℃-80℃. The sensitivities of the PVA-coated sensor are twice of that of the GO-coated senor. The simultaneous measurement of RH and temperature can be achieved by measuring the shifts of two resonant dips.

2. Sensing structure and principle

The structure of the sensor proposed in this paper is shown in Fig. 1(a), which is consisted of two segments of SMF, one segment of DCF, and one segment of NCF spliced together. The core-offset splice is located at the fusion joint between SMF and DCF. The core and cladding diameters of SMF and DCF are 9 μm/125 μm and 4.5 μm/110 μm, respectively. The incident light is input from the SMF and is separated by the core-offset. Part of the beam propagates in the core of the DCF, and the other part propagates in the cladding of the DCF. A part of the cladding layer of the DCF is corroded by the hydrofluoric acid solution, so higher-order cladding modes can be excited better. Generally, there is only one dominant higher-order cladding mode [35], which has a smaller RI and more sensitive to external environment [3]. When the surrounding environment varies, the effective RI of core mode remains unchanged, but the effective RI of the cladding modes changes. As a result, a phase difference between core mode and cladding modes has been produced. Therefore, the interference happens when two beams of light propagate to the NCF. Based on the above analysis, COMSOL Multiphysics simulation software is used for the numerical simulation analysis of the proposed sensing structure. In the simulation, the length of NCF and DCF are 10mm and 2mm, respectively. As shown in Fig. 1(b), it can be found that the beam separation and coupling occur at the core-offset and at the NCF, respectively.

 figure: Fig. 1.

Fig. 1. (a) Sensing structure sketch. (b) Simulated result of the mode field distribution.

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Based on the principle of double beam interference, the proposed sensor can be considered as MZI. As mentioned above, the interference occurs at the NCF, and the interference light intensity can be expressed as [24,36]:

$$I = Ico + Icl + 2\sqrt {IcoIcl} \cos \varphi ,$$
here, Ico and Icl represent the light intensity of the core mode and mainly higher-order cladding mode, respectively. φ is phase difference, which can be expressed as:
$$\varphi = \displaystyle{{2\pi (nco-ncl)} \over \lambda } = \displaystyle{{2\pi \Delta n_{eff}} \over \lambda }L,$$

λ is the center wavelength of the incident light, nco and ncl represent the effective RI of the core modes and mainly higher-order cladding modes of DCF, and Δneff represents the difference between them, L is the length of the DCF. When φ=(2k+1)π, k represents the order of resonance dip. The resonant wavelengths of dips can be expressed as:

$$\lambda dip = \frac{2}{{2k + 1}}\Delta n_{eff}L({k = 1,2,3\ldots .} ).$$

Usually, the interference spectrum has a certain periodicity, and this characteristic is usually described by the free spectral range (FSR):

$$\textrm{FSR} \approx \frac{{{\lambda ^2}}}{{\Delta n_{eff}L}}.$$

According Eq. (3) and Eq. (4), we know that Δneff and L are the main parameters that affect the FSR and the wavelengths of the resonant dips. In this paper, a PVA film was adhered to the surface of the corroded DCF. PVA molecular structure contains a large number of hydrophilic hydroxyl groups, which are extremely sensitive to water molecules, so the breaking and recombination of hydrogen bonds can quickly adsorb and desorb water molecules. The process of adsorbing water molecules is shown in the Fig. 2.

 figure: Fig. 2.

Fig. 2. The mechanism of PVA adsorbing water molecules

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The relationship between the RI and the mass fraction of the PVA can be expressed as [37]:

$$\textrm{y} = 0.0018x + 1.332,$$
where y and x are the RI and mass fraction of the PVA, respectively. When the environmental humidity changes, the PVA film coated on the DCF adsorbs or desorbs water molecules, so that the mass fraction of PVA decreases or increases. As a result, the RI of the PVA film decreases or increases accordingly, and the effective RI of the cladding modes (ncl) decreases or increases. So, the resonant dips will shift due to Δneff changing. The RH can be gained by measuring the shift of the resonant dips.

The shifts of the resonant dips can also be used to measure the relative change of ambient temperature (ΔT), which is expressed as [38]:

$$\frac{{\Delta \lambda }}{\lambda }\textrm{ = }\left( {\frac{{{\xi_{co}} - {\xi_{cl}}}}{{{n_{co}} - {n_{cl}}}} + {\alpha_x}} \right) + \Delta T,$$
where ax is the thermal expansion coefficient, $\xi $co and $\xi $cl are the thermo-optical coefficient of the core and cladding of the DCF. λ is the wavelength of resonant dip, and Δλ the shift of resonant dip.

By measuring the shift of multiple resonant dips, RH and temperature can be measured simultaneously, which is expressed as [6,31]

$$\Delta \lambda dip1 = A\Delta RH + B\Delta T,$$
$$\Delta \lambda dip2 = C\Delta RH + D\Delta T,$$
where ΔRH and ΔT represent the relative change of RH and temperature, respectively. Δλdip1 and Δλdip2 represent the relative shifts of the two resonant dip, respectively. A and C, B and D are the RH and temperature sensitivities coefficients of λdip1 and λdip2, respectively. The relationship between the above parameters can be expressed by a matrix:
$$\left({\begin{array}{l}{\Delta \lambda dip1} \\ {\Delta \lambda dip2} \end{array}} \right) = \left( {\begin{array}{ll} A&B\\ C&D \end{array}} \right)\left({\begin{array}{l}{\Delta RH} \\ {\Delta T } \end{array}}\right),$$
when the RH and temperature change, the sensitivity coefficient matrix of Eq. (9) can be demodulated. As a result, the change of the RH and temperature can be obtained, which can be expressed as:
$$\left( {\begin{array}{ll}{\Delta RH} \\ {\Delta T}\end{array}} \right) = \displaystyle{1 \over {\left| M \right|}}\left( {\begin{array}{ll} D&-B\\ -C&A \end{array}} \right)\left( {\begin{array}{ll}{\Delta \lambda dip1} \\ {\Delta \lambda dip2} \end{array}}\right),$$
the matrix coefficient M can be expressed as:
$$|M |= DA - BC.$$

So, the RH and temperature can be measured simultaneously.

3. Sensing structure manufacturing

3.1 Selection of sensor structure parameters

The sensor structure is composed of SMF, DCF, and NCF. The single core-offset is spliced by manual fusion of the fusion splicer (FITEL S178), the manufacturing process is shown in Fig. 3(a) and (b). Through Fig. 3(c), we can see that the core-offset distance is 9.4 μm.

 figure: Fig. 3.

Fig. 3. (a) Before performing splicing. (b) After performing splicing. (c) SEM image of the core-offset.

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To verify the rationality of the proposed sensor, the output sprecta of different structures are shown in Fig. 4(a). One is that the DCF is spliced between two SMFs without core-offset, the second is that the DCF is spliced between two SMFs with one core-offset, and the last is the structure proposed in this paper. The results indicate that an uniform transmission spectrum with high extinction ratio can be achieved with the structure of SMF + DCF + NCF + SMF.

 figure: Fig. 4.

Fig. 4. (a) Transmission spectra of different structures. (b) FFT of different structures

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Generally, the higher-order cladding modes have higher differential modal group index (Δmeff) due to the lower effective refractive index [39]:

$$\Delta m_{eff} = \Delta n_{eff}-\lambda 0\displaystyle{\partial \over {\partial \lambda }}\Delta n_{eff},$$
when the input center wavelength λ0 is determined, the spatial frequency $\xi $ has the following relationship with Δmeff and interferometer length L, as shown in Eq. (13):
$$\xi = \displaystyle{1 \over {\lambda 0^2}}\Delta m_{eff}L,$$
it can be seen that when λ0 and L are constant, $\xi $ and Δmeff are positively correlated. As shown in Fig. 4(b), the Fast Fourier transform (FFT) of the three structures are analyzed. The sensor proposed in this paper can excite more and higher high-order cladding modes with a higher intensity. By Eq. (3) and Eq. (13), the length of the DCF can affect the FSR of transmission spectrum and the high-order modes excited.Generally, it is relatively appropriate to have 3-5 periods of interference dips in the transmission spectrum [3]. The wavelength range used in this paper is 70 nm, so FSR is 14-22 nm. Figure 5 shows the the transmission spectra under different DCF lengths. As we can see that an uniform spectrum with obvious contrast can be achieved when the DCF length is 10 mm, which has been used in the following experiments. Meanwhile, the corresponding FSR is suitable to measure the shift of resonant dips.

3.2 Chemical etching process

For optical fiber sensors, the chemical etching process can increase sensitivity, which is mainly reflected in two aspects. One is to increase the leakage of the evanescent wave, and the other is to stimulate the higher-order cladding mode. So, a part of the cladding of the DCF is corroded by hydrofluoric acid (HF, Sigma-Aldrich (Shanghai) Trading Co.Ltd.).

 figure: Fig. 5.

Fig. 5. Comparison chart of DCF transmission spectra of different lengths.

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The DCF was fixed on the polytetrafluoroethylene plate board, and then a dropper was used to suck and drop 100 µL of 40% HF on the middle of the DCF, as shown in Fig. 6. After 10 minutes of corrosion, the DCF was rinsed with alcohol and deionized water repeatedly, and was left in air to dry for 1 h. As show in Fig. 7(a), we can see that the extinction ratio and FSR become larger, which is due to the higher order cladding modes being excited. The diameter of the corroded DCF was obtained by the scanning electron microscopy (SEM). It can be seen from Fig. 8(a) that its diameter is 96.45 µm.

 figure: Fig. 6.

Fig. 6. Schematic diagram of optical fiber cladding corrosion process

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 figure: Fig. 7.

Fig. 7. (a) Transmission spectrum before and after corrosion. (b) FFT before and after corrosion

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 figure: Fig. 8.

Fig. 8. (a) SEM image of the DCF after corrosion. (b) SEM image of GO coating morphology. (c) SEM image of the DCF after PVA coating. (d) SEM image of PVA coating morphology.

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Figure 7(b) shows the corresponding the FFT. The spatial frequencies of the dominant cladding mode before and after corrosion are 0.04999 nm-1 and 0.05999 nm-1, respectively. The software OptiFiber has been used to calculate the corresponding Δmeff between different LP01 and high-order cladding modes, as shown in Table 1. The wavelength λ0 is 1550 nm, L is 10 mm, by Eq. (13), it can be calculated that Δmeff is 0.0144125975. It is approximately closed to the Δmeff of LP10. The results indicate that the sensor can inspire higher-order cladding modes.

Tables Icon

Table 1. the simulated value of Δmeff corresponding to different high-order cladding modes

3.3 Preparation and coating of PVA or GO

For the preparation and coating of PVA (P816862, Shanghai Macklin Biochemical Co., Ltd.), 5 g PVA particles were immersed in 100 mL deionized water at 70℃ for 1 h, until the solid particles were fully dissolved. The PVA solution was centrifuged at 6800 rpm/min for 3 h until a uniform and stable 0.05 g/mL PVA solution was obtained. For the coating of PVA, the surface of DCF was cleaned with alcohol, then the DCF was suspended horizontally for about 3 mm, and the prepared PVA was evenly coated on the corrosion area of DCF. Finally, it had been left in air at 25℃ for 48 h to evaporate naturally. For the preparation and coating of GO (XF020, Nanjing XFNANO Materials Tech. Co., Ltd.), the density of GO dispersion was 0.1 mg/mL. The coating method of GO was the same as that of PVA. After standing in air for 24 h at a room temperature of 25℃, a GO film was evenly deposited on the surface of DCF.

The surface morphology of DCF coated with GO/PVA is shown in Fig. 8. It can be seen that the GO/PVA is successfully deposited uniformly on the surface of the DCF. The MZI transmission spectra coated with GO/PVA are shown in Fig. 9. The spectra changes indicate that the effective RI of cladding modes varies due to the coating material.

 figure: Fig. 9.

Fig. 9. Spectral comparison chart before and after coating.

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4. Experimental research and analysis

The experimental platform used in this paper is shown in Fig. 10, which mainly includes MZI sensor, optical spectrum analyzer (OSA, AQQ6370, YOKOGAWA), constant temperature and humidity chamber (CTHC, J-TOPH-22-B, JieXin Testing Equipment Co. Ltd.) and broadband source (BBS, ASE-C + L module, Shanghai Huiya Communication Technology Co. Ltd.). The resolution of OSA is 0.02 nm. The MZI 1 is coated with 0.1 mg/mL GO and the MZI 2 is coated with 0.05 g/mL PVA.

 figure: Fig. 10.

Fig. 10. The dual parameter measurement system for RH and temperature

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4.1 MZI sensor coated with GO measures RH and temperature

In the RH measurement experiment, the MZI 1 was placed in CTHC keeping constant temperature at 25℃, and the RH was increased from 35% to 95%. Figure 11(a) shows the RH measurement results of MZI 1. It can be seen that as the RH increases, the dips shift to short wavelength. This is because after adsorbing water molecules, the RI of GO decreases [3]. The relationship between the wavelength of resonant dips and RH is shown in Fig. 11(b). The linear fitting results indicate that in the RH range of 35%-95%, the linear sensitivity of dip A, dip B and dip C are 0.072 nm/RH%, 0.095 nm/RH% and 0.122 nm/RH%, respectively. The corresponding linear fitting values are 97%, 98% and 99%, respectively.

 figure: Fig. 11.

Fig. 11. (a) RH measurement results of MZI 1. (b) The linear fitting graph of RH and the wavelengths of the resonant dip A, dip B, dip C.

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For the tempearture characteristics measurement, the MZI 1 was placed in CTHC keeping constant RH at 60%, and the temperature changed from 30℃ to 80℃. Figure 12(a) shows that when the temperature increases the resonant dips are shifted to the long wavelength. As shown in Fig. 12 (b), the linear sensitivity of dip A, dipB and dip C are 0.052 nm/℃, 0.062 nm/℃ and 0.069 nm/℃, respectively. The corresponding linear fitting values are 93%, 95% and 94%, respectively.

 figure: Fig. 12.

Fig. 12. (a) Temperature measurement results of MZI 1. (b) The linear fitting graph of temperature and the wavelengths of the resonant dip A, dip B, dip C.

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Stability is also an important indicator for evaluating sensor performance. For the RH stability, keeping the temperature at 25℃ and the RH at 55% or 75% for 1 h; For the temperature stability, keeping the RH at 60% and the temperature at 30℃ or 70℃ for 1 h, we measured the spectra per 10 min to gain the dip wavelength, as shown in Fig. 13. When the RH is 55%, the maximum fluctuations of the wavelengths of resonant dip A, B and C are 0.15 nm, 0.12 nm and 0.15 nm, respectively. When the RH is 75%, the maximum fluctuations are 0.13 nm, 0.12 nm and 0.16 nm, respectively. When the temperature is 30℃, the maximum fluctuations of dip A, B and C are 0.13 nm, 0.14 nm and 0.13 nm, respectively. And when the temperature is 70℃, the maximum fluctuations are 0.14 nm, 0.15 nm and 0.14 nm, respectively.

 figure: Fig. 13.

Fig. 13. (a) The RH stability of the MZI 1. (b) The temperature stability of the MZI 1.

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4.2 MZI sensor coated with PVA measures RH and temperature

In the RH measurement experiment, The MZI 2 was also placed in CTHC keeping constant temperature at 25℃, and RH was increased from 30% to 95%.

PVA has a certain swelling property, so the RI of PVA will decrease as the mass fraction of PVA decreases. As a result, ncl decreases, and Δneff increases. As expected, as the RH increases, the resonant dips shift to long wavelength, the dip A shifted from 1542 nm to 1557.86 nm (15.86 nm), the dip B shifted from 1556.52 nm to 1572.18 nm (15.66 nm), as shown in Fig. 14(a). The relationship between resonant dips wavelength and RH is shown in Fig. 14(b). The linear fitting resluts indicate that within the RH range of 30%-95%, the RH linear sensitivity of dip A and dip B are 0.256 nm/RH% and 0.248 nm/RH%, and the corresponding R2 values are 99% and 99%, respectively.

 figure: Fig. 14.

Fig. 14. (a) RH measurement results of 0.05 g/mL PVA. (b) The linear fitting graph of temperature and the wavelengths of the resonant dip A dip B.

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The performance of the sensor coated with different concentrations of PVA was tested. We experimentally verified the sensor performance of PVA coated with 0.04 g/mL, 0.05 g/mL and 0.06 g/mL concentrations, respectively. The experimental results are shown in Fig. 15(a) and (b) and Fig. 14(a), respectively. Figure 15(a) and (b) show that the dip shifts is less than 3 nm when the RH increases from 30% to 70%, which is small than that of the sensor coated with 0.05 g/mL PVA solution (Fig. 14(a)). This is because the surface morphology of the PVA film will affect its ability to adsorb water molecules. The surface morphology of the 0.05 g/mL PVA shown in Fig. 8(d) is uniform and rough, which is benefitted for the adsorption and desorption of a large number of water molecules.

 figure: Fig. 15.

Fig. 15. (a) RH measurement results of 0.04 g/mL PVA. (b) RH measurement results of 0.06 g/mL PVA.

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For temperature measurement, the MZI 2 was placed in the CTHC keeping constant RH at 60%. The measurement result of MZI 2 is shown in Fig. 16. The resonant dip A and dip B shift to the long wavelength when the temperature inceases from 20℃ to 80℃. The corresponding sensitivities are 0.153 nm/℃ and 0.154 nm/℃, and the R2 values are 99% and 99%, respectively.

 figure: Fig. 16.

Fig. 16. (a) Temperature measurement result of MZI 2. (b) The linear fitting graph of temperature and the wavelengths of the resonant dip A, dip B.

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The method used for the stability test of MZI 2 is the same as the method that of MZI 1. For RH measurement stability, keeping the temperature at 25℃ and the RH at 50% or 70% for 1 h; For temperature measurement stability, keeping the RH at 60% and the temperature at 30℃ or 70℃ for 1 h, we had also measured the spectra to gain the dips wavelength, as shown in Fig. 17. When the RHs are 55% and 75%, the maximum fluctuations of resonant dip A are 0.08 nm and 0.11 nm, respectively; for the resonant dip B, the maximum fluctuations are 0.09 nm and 0.12 nm, respectively. When the temperatures are 30℃ and 70℃, for the resonance dip A, the maximum fluctuations are 0.1 nm and 0.11 nm, respectively; for the resonance dip B, the maximum fluctuations are 0.12 nm and 0.13 nm, respectively. The wavelength fluctuation may be caused by machine vibration in the CTHC. Compared with MZI 1, the RH and temperature sensitivities of MZI 2 coated with PVA are increased by 2 times and the corresponding linearity are also relatively good. Therefore, this paper uses MZI 2 to measure RH and temperature simultaneously.

 figure: Fig. 17.

Fig. 17. (a) The RH stability of the MZI 2. (b)The temperature stability of the MZI 2.

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Repeatability is an important indicator for evaluating sensor performance. After one month, the same method as above has been used to test the MZI 2 sensor again. The measurement results are shown in Fig. 18. For RH measurement, the maximum error rates of dip A and dip B are 0.15% and 0.07%, respectively. For temperature measurement, the maximum error rates of dip A and dip B are 0.068% and 0.08%, respectively. The result indicate that the sensor has a good repeatability.

 figure: Fig. 18.

Fig. 18. (a) RH repeatability test. (b) Temperature repeatability test.

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According to the sensitivities of RH and temperature of dip A and B, Eq. (11) can be rewritten as:

$$\left( \begin{array}{l} \Delta RH\\ \Delta T \end{array} \right) = \left( {\begin{array}{cc} {104.054}&{ - 103.3784}\\ { - 167.5676}&{172.973} \end{array}} \right)\left( \begin{array}{l} \Delta \lambda dipA\\ \Delta \lambda dipB \end{array} \right),$$
so, RH and temperature can be measured simultaneously by measuring the shift of the resonant dip A and dip B.

Table 2 shows the performance of sensors proposed in reported work and in this paper. By comparison, the sensor proposed in this paper has the characteristics of high sensitivity and large measurement range.

Tables Icon

Table 2. Comparison of optical fiber RH and temperature sensor performance.

5. Conclusion

The single core-offset MZI RH and temperature sensor coated with PVA was proposed and demonstrated. The method of chemical etching and coating of PVA film enhances the sensitivity of the sensor to the external environment. In the RH range of 30%-95%, a RH sensitivity of 0.256 nm/RH% can be achieved with a linear coefficient of 99%. While in the temperature range of 20℃-80℃, the temperature sensitivity of 0.153 nm/℃ can be achieved with a linear coefficient of 99%. The sensor has characteristics such as good stability, low cost, high sensitivity and repeatability, which has potential application in the complex environment of multiple fields.

Funding

National Natural Science Foundation of China (11674109, 61774062); Natural Science Foundation of Guangdong Province (2016A030313443); Science and Technology Planning Project of Guangdong Province (2017A020219007).

Disclosures

The authors declare no conflicts of interest.

Data Availability

Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.

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9. L. P. Sun, J. Li, L. Jin, Y. Ran, and B. O. Guan, “High-birefringence microfiber Sagnac interferometer based humidity sensor,” Sensors and Actuators B: Chemical 231, 696–700 (2016). [CrossRef]  

10. H. Y. Chen, Z. T. Gu, and K. Gao, “Humidity sensor based on cascaded chirped long-period fiber gratings coated with TiO2/SnO2 composite films,” Sensors and Actuators B: Chemical 196, 18–22 (2014). [CrossRef]  

11. P. P. Wang, K. Ni, B. W. Wang, Q. F. Ma, and W. J. Tian, “Methylcellulose Coated Humidity Sensor Based on Michelson Interferometer with Thin-core Fiber,” Sensors and Actuators A: Physical 288, 75–78 (2019). [CrossRef]  

12. G. Woyessa, A. Fasano, C. Markos, H. K. Rasmussen, and O. Bang, “Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing,” IEEE Photonics Technol. Lett. 29(7), 575–578 (2017). [CrossRef]  

13. Y. Zhao, R. J. Tong, M. Q. Chen, and F. Xia, “Relative Humidity sensor based on Hollow Core Fiber Filled with GQDs-PVA,” Sensors and Actuators B: Chemical 284, 96–102 (2019). [CrossRef]  

14. Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018). [CrossRef]  

15. S. Deng, H. Meng, X. Wang, X. Fan, Q. Wang, M. Zhou, X. Guo, Z. Wei, F. Wang, C. Tan, and X. Huang, “Graphene oxide-film-coated splitting ratio-adjustable Mach-Zehnder interferometer for relative humidity sensing,” Opt. Express 27(6), 9232–9240 (2019). [CrossRef]  

16. Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer coated with graphene oxide,” Sensors and Actuators B: Chemical 234, 503–509 (2016). [CrossRef]  

17. Y. Zhao, Y. Peng, M. Q. Chen, and R. J. Tong, “Humidity sensor based on unsymmetrical U-shaped microfiber with a polyvinyl alcohol overlay,” Sensors and Actuators B: Chemical 263, 312–318 (2018). [CrossRef]  

18. D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013). [CrossRef]  

19. T. Li, X. Y. Dong, C. C. Chan, C. L. Zhao, and P. Zu, “Humidity sensor based on multimode-fiber taper coated with polyvinyl alcohol interacting with a fibe Bragg grating,” IEEE Sens. J. 12(6), 2205–2208 (2012). [CrossRef]  

20. W.C. Wong, C.C. Chan, L.H. Chen, T. Li, K.X. Lee, and K.C. Leong, “Polyvinyl alcohol coated photonic crystal optical fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 174, 563–569 (2012). [CrossRef]  

21. R. J. Tong, Y. Zhao, M. Q. Chen, and Y. Peng, “Multimode interferometer based on no-core fiber with GQDs-PVA composite coating for relative humidity sensing,” Opt. Fiber Technol. 48, 242–247 (2019). [CrossRef]  

22. Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Fiber optic humidity sensor based on the graphene oxide/PVA composite film,” Opt. Commun. 372, 229–234 (2016). [CrossRef]  

23. J. Wang, “Numerical simulation and optimal design of photonic crystal fiber hygrometer coated with PVA/GO composite film,” Opt. Fiber Technol. 63, 102491 (2021). [CrossRef]  

24. C. Bian, Y. F. Cheng, W. H. Zhu, R. X. Tong, M. L. Hu, and T. T. Gang, “A Novel Optical Fiber Mach-Zehnder Interferometer Based on the Calcium Alginate Hydrogel Film for Humidity Sensing,” IEEE Sens. J. 20(11), 5759–5765 (2020). [CrossRef]  

25. C. Bian, J. Wang, X. H. Bai, M. L. Hu, and T. T. Gang, “Optical fiber based on humidity sensor with improved sensitivity for monitoring applications,” Opt. Laser Technol. 130, 106342 (2020). [CrossRef]  

26. Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018). [CrossRef]  

27. J. Ascorbe, J. M. Corres, I. R. Matias, and F. J. Arregui, “High sensitivity humidity sensor based on cladding-etched optical fiber and lossy mode resonances,” Sensors and Actuators B: Chemical 233, 7–16 (2016). [CrossRef]  

28. J. Wang, C. Bian, T. T. Gang, and M. L. Hu, “High-sensitive Mach-Zehnder interferometer for humidity measurements based on concatenating single-mode concave cone and core-offset,” Optik 208, 164465 (2020). [CrossRef]  

29. L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012). [CrossRef]  

30. N. Irawati, H. A. Rahman, M. Yasin, S. Al-Askari, B. A. Hamida, H. Ahmad, and S. W. Harun, “Relative humidity sensing using a PMMA doped agarose gel microfiber,” J. Lightwave Technol. 35(18), 3940–3944 (2017). [CrossRef]  

31. C. L. Lee, Y. W. You, J. H. Dai, J. M. Hsu, and J. S. Horng, “Hygroscopic polymer microcavity fiber Fizeau interferometer incorporating a fiber Bragg grating for simultaneously sensing humidity and temperature,” Sensors and Actuators B: Chemical 222, 339–346 (2016). [CrossRef]  

32. R. J. Tong, Y. Zhao, H. K. Zheng, and F. Xia, “Simultaneous measurement of temperature and relative humidity by compact Mach-Zehnder interferometer and Fabry-Perot interferometer,” Measurement 155, 107499 (2020). [CrossRef]  

33. A. Urrutia, J. Goicoechea, A. L. Ricchiuti, D. Barrera, S. Sales, and F. J. Arregui, “Simultaneous measurement of humidity and temperature based on a partially coated optical fiber long period grating,” Sensors and Actuators B: Chemical 227, 135–141 (2016). [CrossRef]  

34. J. N. Cheng, “In-fiber Mach-Zehnder interferometer based on multi-core microfiber for humidity and temperature sensing,” Appl. Opt. 59(3), 756–763 (2020). [CrossRef]  

35. L.V. Nguyen, D. Hwang, S. Moon, D.S. Moon, and Y. Chung, “High temperature fiber sensor with high sensitivity based on core diameter mismatch,” Opt. Express 16(15), 11369–11375 (2008). [CrossRef]  

36. S. Liu, H. Y . Meng, S. Y . Deng, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Fiber humidity sensor based on a graphene-coated core-offset Mach-Zehnder interferometer,” IEEE Sens. Lett. 2(3), 1–4 (2018). [CrossRef]  

37. N. Chen, X. Zhou, and X. G. Li, “Highly Sensitive Humidity Sensor With Low-Temperature Cross-Sensitivity Based on a Polyvinyl Alcohol Coating Tapered Fiber,” IEEE Trans. Instrum. Meas. 70, 9503308 (2021). [CrossRef]  

38. Y. M. Zhong, Z. R. Tong, W. H. Zhang, J. Qin, and W. L Gao, “Humidity and temperature sensor based on a Mach-Zehnder interferometer with a pokal taper and peanut taper,” Appl. Opt. 58(29), 7981–7986 (2019). [CrossRef]  

39. H. Y. Choi, M. J. Kim, and B. H. Lee, “All-fiber Mach-Zehnder type interferometers formed in photonic crystal fiber,” Opt. Express 15(9), 5711–5720 (2007). [CrossRef]  

40. S. N. Wu, G. F. Yan, Z. G. Lian, X. Chen, B. Zhou, and S. L. He, “An open-cavity Fabry-Perot interferometer with PVA coating for simultaneous measurement of relative humidity and temperature,” Sensors and Actuators A: Physical 225, 50–56 (2016). [CrossRef]  

41. J. T. Zhang, Z. R. Tong, W. H. Zhang, Y. M. Zhao, and J. X. Li, “Research on simultaneous temperature and relative humidity measurement based on tapered PCF Mach-Zehnder interferometer,” Opt. Fiber Technol. 61, 102408 (2021). [CrossRef]  

42. L. Liang, H. Sun, N. Liu, H. Luo, T. T. Gang, Q. Z. Rong, X. G. Qiao, and M. L. Hu, “High-sensitivity optical fiber relative humidity probe with temperature calibration ability,” Appl. Opt. 57(4), 872–876 (2018). [CrossRef]  

43. Y. T. Bai, Y. P. Miao, H. M. Zhang, and J. Q. Yao, “Simultaneous measurement of relative humidity and temperature using a microfiber coupler coated with molybdenum disulfide nanosheets,” Opt. Mater Express 9(7), 2846–2858 (2019). [CrossRef]  

44. H. W. Fu, Y. H. Jiang, J. J. Ding, and Z. L. Zhang, “Low Temperature Cross-Sensitivity Humidity Sensor Based on a U-Shaped Microfiber Interferometer,” IEEE Sens. J. 17(3), 644–649 (2017). [CrossRef]  

References

  • View by:

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    [Crossref]
  2. Q. Z. Wang, H. Y. Meng, X. F. Fan, M. Q. Zhou, F. X. Liu, C. Y. Liu, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structur,” Rev. Sci. Instrum. 91(1), 015006 (2020).
    [Crossref]
  3. X Fan, Q Wang, M Zhou, F. Liu, H. Shen, Z. Wei, F. Wang, C. Tan, and H. Meng, “Humidity sensor based on a graphene oxide-coated few-mode fiber Mach-Zehnder interferometer,” Opt. Express 28(17), 24682–24692 (2020).
    [Crossref]
  4. R. Xiong, H. Y. Meng, Q. Q. Yao, B. Huang, Y. M. Liu, H. C. Xue, C. H. Tan, and X. G. Huang, “Simultaneous Measurement of Refractive Index and Temperature Based on Modal Interference,” IEEE Sens. J. 14(8), 2524–2528 (2014).
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  5. Q. Q. Yao, H. Y. Meng, W. Wang, H. C. Xue, R. Xiong, B. Huang, C. H. Tan, and X. G. Huang, “Simultaneous measurement of refractive index and temperature based on a core-offset Mach-Zehnder interferometer combined with a fiber Bragg grating,” Sensors and Actuators A: Physical 209, 73–77 (2014).
    [Crossref]
  6. Q. Z. Rong, X. G. Qiao, J. Zhang, R. H. Wang, M. L. Hu, and Z.Y. Feng, “Simultaneous Measurement for Displacement and Temperature Using Fiber Bragg Grating Cladding Mode Based on Core Diameter Mismatch,” J. Lightwave Technol. 30(11), 1645–1650 (2012).
    [Crossref]
  7. G. J. Huang, Y. J. Li, C. Chen, Z. Z. Yue, W. Zhai, M. D. Li, and B. Yang, “Hydrogen Sulfide Gas Sensor Based on Titanium Dioxide/Amino-Functionalized Graphene Quantum Dots Coated Photonic Crystal Fiber,” J. Phys. D: Appl. Phys. 53(32), 325102 (2020).
    [Crossref]
  8. X. D. Zhang, C. Y. Liu, J. P. Liu, and J. R. Yang, “Single Modal Interference-Based Fiber-Optic Sensor for Simultaneous Measurement of Curvature and Strain With Dual-Differential Temperature Compensation,” IEEE Sens. J. 18(20), 8375–8380 (2018).
    [Crossref]
  9. L. P. Sun, J. Li, L. Jin, Y. Ran, and B. O. Guan, “High-birefringence microfiber Sagnac interferometer based humidity sensor,” Sensors and Actuators B: Chemical 231, 696–700 (2016).
    [Crossref]
  10. H. Y. Chen, Z. T. Gu, and K. Gao, “Humidity sensor based on cascaded chirped long-period fiber gratings coated with TiO2/SnO2 composite films,” Sensors and Actuators B: Chemical 196, 18–22 (2014).
    [Crossref]
  11. P. P. Wang, K. Ni, B. W. Wang, Q. F. Ma, and W. J. Tian, “Methylcellulose Coated Humidity Sensor Based on Michelson Interferometer with Thin-core Fiber,” Sensors and Actuators A: Physical 288, 75–78 (2019).
    [Crossref]
  12. G. Woyessa, A. Fasano, C. Markos, H. K. Rasmussen, and O. Bang, “Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing,” IEEE Photonics Technol. Lett. 29(7), 575–578 (2017).
    [Crossref]
  13. Y. Zhao, R. J. Tong, M. Q. Chen, and F. Xia, “Relative Humidity sensor based on Hollow Core Fiber Filled with GQDs-PVA,” Sensors and Actuators B: Chemical 284, 96–102 (2019).
    [Crossref]
  14. Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
    [Crossref]
  15. S. Deng, H. Meng, X. Wang, X. Fan, Q. Wang, M. Zhou, X. Guo, Z. Wei, F. Wang, C. Tan, and X. Huang, “Graphene oxide-film-coated splitting ratio-adjustable Mach-Zehnder interferometer for relative humidity sensing,” Opt. Express 27(6), 9232–9240 (2019).
    [Crossref]
  16. Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer coated with graphene oxide,” Sensors and Actuators B: Chemical 234, 503–509 (2016).
    [Crossref]
  17. Y. Zhao, Y. Peng, M. Q. Chen, and R. J. Tong, “Humidity sensor based on unsymmetrical U-shaped microfiber with a polyvinyl alcohol overlay,” Sensors and Actuators B: Chemical 263, 312–318 (2018).
    [Crossref]
  18. D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
    [Crossref]
  19. T. Li, X. Y. Dong, C. C. Chan, C. L. Zhao, and P. Zu, “Humidity sensor based on multimode-fiber taper coated with polyvinyl alcohol interacting with a fibe Bragg grating,” IEEE Sens. J. 12(6), 2205–2208 (2012).
    [Crossref]
  20. W.C. Wong, C.C. Chan, L.H. Chen, T. Li, K.X. Lee, and K.C. Leong, “Polyvinyl alcohol coated photonic crystal optical fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 174, 563–569 (2012).
    [Crossref]
  21. R. J. Tong, Y. Zhao, M. Q. Chen, and Y. Peng, “Multimode interferometer based on no-core fiber with GQDs-PVA composite coating for relative humidity sensing,” Opt. Fiber Technol. 48, 242–247 (2019).
    [Crossref]
  22. Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Fiber optic humidity sensor based on the graphene oxide/PVA composite film,” Opt. Commun. 372, 229–234 (2016).
    [Crossref]
  23. J. Wang, “Numerical simulation and optimal design of photonic crystal fiber hygrometer coated with PVA/GO composite film,” Opt. Fiber Technol. 63, 102491 (2021).
    [Crossref]
  24. C. Bian, Y. F. Cheng, W. H. Zhu, R. X. Tong, M. L. Hu, and T. T. Gang, “A Novel Optical Fiber Mach-Zehnder Interferometer Based on the Calcium Alginate Hydrogel Film for Humidity Sensing,” IEEE Sens. J. 20(11), 5759–5765 (2020).
    [Crossref]
  25. C. Bian, J. Wang, X. H. Bai, M. L. Hu, and T. T. Gang, “Optical fiber based on humidity sensor with improved sensitivity for monitoring applications,” Opt. Laser Technol. 130, 106342 (2020).
    [Crossref]
  26. Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
    [Crossref]
  27. J. Ascorbe, J. M. Corres, I. R. Matias, and F. J. Arregui, “High sensitivity humidity sensor based on cladding-etched optical fiber and lossy mode resonances,” Sensors and Actuators B: Chemical 233, 7–16 (2016).
    [Crossref]
  28. J. Wang, C. Bian, T. T. Gang, and M. L. Hu, “High-sensitive Mach-Zehnder interferometer for humidity measurements based on concatenating single-mode concave cone and core-offset,” Optik 208, 164465 (2020).
    [Crossref]
  29. L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
    [Crossref]
  30. N. Irawati, H. A. Rahman, M. Yasin, S. Al-Askari, B. A. Hamida, H. Ahmad, and S. W. Harun, “Relative humidity sensing using a PMMA doped agarose gel microfiber,” J. Lightwave Technol. 35(18), 3940–3944 (2017).
    [Crossref]
  31. C. L. Lee, Y. W. You, J. H. Dai, J. M. Hsu, and J. S. Horng, “Hygroscopic polymer microcavity fiber Fizeau interferometer incorporating a fiber Bragg grating for simultaneously sensing humidity and temperature,” Sensors and Actuators B: Chemical 222, 339–346 (2016).
    [Crossref]
  32. R. J. Tong, Y. Zhao, H. K. Zheng, and F. Xia, “Simultaneous measurement of temperature and relative humidity by compact Mach-Zehnder interferometer and Fabry-Perot interferometer,” Measurement 155, 107499 (2020).
    [Crossref]
  33. A. Urrutia, J. Goicoechea, A. L. Ricchiuti, D. Barrera, S. Sales, and F. J. Arregui, “Simultaneous measurement of humidity and temperature based on a partially coated optical fiber long period grating,” Sensors and Actuators B: Chemical 227, 135–141 (2016).
    [Crossref]
  34. J. N. Cheng, “In-fiber Mach-Zehnder interferometer based on multi-core microfiber for humidity and temperature sensing,” Appl. Opt. 59(3), 756–763 (2020).
    [Crossref]
  35. L.V. Nguyen, D. Hwang, S. Moon, D.S. Moon, and Y. Chung, “High temperature fiber sensor with high sensitivity based on core diameter mismatch,” Opt. Express 16(15), 11369–11375 (2008).
    [Crossref]
  36. S. Liu, H. Y . Meng, S. Y . Deng, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Fiber humidity sensor based on a graphene-coated core-offset Mach-Zehnder interferometer,” IEEE Sens. Lett. 2(3), 1–4 (2018).
    [Crossref]
  37. N. Chen, X. Zhou, and X. G. Li, “Highly Sensitive Humidity Sensor With Low-Temperature Cross-Sensitivity Based on a Polyvinyl Alcohol Coating Tapered Fiber,” IEEE Trans. Instrum. Meas. 70, 9503308 (2021).
    [Crossref]
  38. Y. M. Zhong, Z. R. Tong, W. H. Zhang, J. Qin, and W. L Gao, “Humidity and temperature sensor based on a Mach-Zehnder interferometer with a pokal taper and peanut taper,” Appl. Opt. 58(29), 7981–7986 (2019).
    [Crossref]
  39. H. Y. Choi, M. J. Kim, and B. H. Lee, “All-fiber Mach-Zehnder type interferometers formed in photonic crystal fiber,” Opt. Express 15(9), 5711–5720 (2007).
    [Crossref]
  40. S. N. Wu, G. F. Yan, Z. G. Lian, X. Chen, B. Zhou, and S. L. He, “An open-cavity Fabry-Perot interferometer with PVA coating for simultaneous measurement of relative humidity and temperature,” Sensors and Actuators A: Physical 225, 50–56 (2016).
    [Crossref]
  41. J. T. Zhang, Z. R. Tong, W. H. Zhang, Y. M. Zhao, and J. X. Li, “Research on simultaneous temperature and relative humidity measurement based on tapered PCF Mach-Zehnder interferometer,” Opt. Fiber Technol. 61, 102408 (2021).
    [Crossref]
  42. L. Liang, H. Sun, N. Liu, H. Luo, T. T. Gang, Q. Z. Rong, X. G. Qiao, and M. L. Hu, “High-sensitivity optical fiber relative humidity probe with temperature calibration ability,” Appl. Opt. 57(4), 872–876 (2018).
    [Crossref]
  43. Y. T. Bai, Y. P. Miao, H. M. Zhang, and J. Q. Yao, “Simultaneous measurement of relative humidity and temperature using a microfiber coupler coated with molybdenum disulfide nanosheets,” Opt. Mater Express 9(7), 2846–2858 (2019).
    [Crossref]
  44. H. W. Fu, Y. H. Jiang, J. J. Ding, and Z. L. Zhang, “Low Temperature Cross-Sensitivity Humidity Sensor Based on a U-Shaped Microfiber Interferometer,” IEEE Sens. J. 17(3), 644–649 (2017).
    [Crossref]

2021 (3)

J. Wang, “Numerical simulation and optimal design of photonic crystal fiber hygrometer coated with PVA/GO composite film,” Opt. Fiber Technol. 63, 102491 (2021).
[Crossref]

N. Chen, X. Zhou, and X. G. Li, “Highly Sensitive Humidity Sensor With Low-Temperature Cross-Sensitivity Based on a Polyvinyl Alcohol Coating Tapered Fiber,” IEEE Trans. Instrum. Meas. 70, 9503308 (2021).
[Crossref]

J. T. Zhang, Z. R. Tong, W. H. Zhang, Y. M. Zhao, and J. X. Li, “Research on simultaneous temperature and relative humidity measurement based on tapered PCF Mach-Zehnder interferometer,” Opt. Fiber Technol. 61, 102408 (2021).
[Crossref]

2020 (8)

C. Bian, Y. F. Cheng, W. H. Zhu, R. X. Tong, M. L. Hu, and T. T. Gang, “A Novel Optical Fiber Mach-Zehnder Interferometer Based on the Calcium Alginate Hydrogel Film for Humidity Sensing,” IEEE Sens. J. 20(11), 5759–5765 (2020).
[Crossref]

C. Bian, J. Wang, X. H. Bai, M. L. Hu, and T. T. Gang, “Optical fiber based on humidity sensor with improved sensitivity for monitoring applications,” Opt. Laser Technol. 130, 106342 (2020).
[Crossref]

J. Wang, C. Bian, T. T. Gang, and M. L. Hu, “High-sensitive Mach-Zehnder interferometer for humidity measurements based on concatenating single-mode concave cone and core-offset,” Optik 208, 164465 (2020).
[Crossref]

R. J. Tong, Y. Zhao, H. K. Zheng, and F. Xia, “Simultaneous measurement of temperature and relative humidity by compact Mach-Zehnder interferometer and Fabry-Perot interferometer,” Measurement 155, 107499 (2020).
[Crossref]

J. N. Cheng, “In-fiber Mach-Zehnder interferometer based on multi-core microfiber for humidity and temperature sensing,” Appl. Opt. 59(3), 756–763 (2020).
[Crossref]

Q. Z. Wang, H. Y. Meng, X. F. Fan, M. Q. Zhou, F. X. Liu, C. Y. Liu, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structur,” Rev. Sci. Instrum. 91(1), 015006 (2020).
[Crossref]

X Fan, Q Wang, M Zhou, F. Liu, H. Shen, Z. Wei, F. Wang, C. Tan, and H. Meng, “Humidity sensor based on a graphene oxide-coated few-mode fiber Mach-Zehnder interferometer,” Opt. Express 28(17), 24682–24692 (2020).
[Crossref]

G. J. Huang, Y. J. Li, C. Chen, Z. Z. Yue, W. Zhai, M. D. Li, and B. Yang, “Hydrogen Sulfide Gas Sensor Based on Titanium Dioxide/Amino-Functionalized Graphene Quantum Dots Coated Photonic Crystal Fiber,” J. Phys. D: Appl. Phys. 53(32), 325102 (2020).
[Crossref]

2019 (6)

P. P. Wang, K. Ni, B. W. Wang, Q. F. Ma, and W. J. Tian, “Methylcellulose Coated Humidity Sensor Based on Michelson Interferometer with Thin-core Fiber,” Sensors and Actuators A: Physical 288, 75–78 (2019).
[Crossref]

Y. Zhao, R. J. Tong, M. Q. Chen, and F. Xia, “Relative Humidity sensor based on Hollow Core Fiber Filled with GQDs-PVA,” Sensors and Actuators B: Chemical 284, 96–102 (2019).
[Crossref]

S. Deng, H. Meng, X. Wang, X. Fan, Q. Wang, M. Zhou, X. Guo, Z. Wei, F. Wang, C. Tan, and X. Huang, “Graphene oxide-film-coated splitting ratio-adjustable Mach-Zehnder interferometer for relative humidity sensing,” Opt. Express 27(6), 9232–9240 (2019).
[Crossref]

R. J. Tong, Y. Zhao, M. Q. Chen, and Y. Peng, “Multimode interferometer based on no-core fiber with GQDs-PVA composite coating for relative humidity sensing,” Opt. Fiber Technol. 48, 242–247 (2019).
[Crossref]

Y. T. Bai, Y. P. Miao, H. M. Zhang, and J. Q. Yao, “Simultaneous measurement of relative humidity and temperature using a microfiber coupler coated with molybdenum disulfide nanosheets,” Opt. Mater Express 9(7), 2846–2858 (2019).
[Crossref]

Y. M. Zhong, Z. R. Tong, W. H. Zhang, J. Qin, and W. L Gao, “Humidity and temperature sensor based on a Mach-Zehnder interferometer with a pokal taper and peanut taper,” Appl. Opt. 58(29), 7981–7986 (2019).
[Crossref]

2018 (6)

S. Liu, H. Y . Meng, S. Y . Deng, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Fiber humidity sensor based on a graphene-coated core-offset Mach-Zehnder interferometer,” IEEE Sens. Lett. 2(3), 1–4 (2018).
[Crossref]

L. Liang, H. Sun, N. Liu, H. Luo, T. T. Gang, Q. Z. Rong, X. G. Qiao, and M. L. Hu, “High-sensitivity optical fiber relative humidity probe with temperature calibration ability,” Appl. Opt. 57(4), 872–876 (2018).
[Crossref]

Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
[Crossref]

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Y. Zhao, Y. Peng, M. Q. Chen, and R. J. Tong, “Humidity sensor based on unsymmetrical U-shaped microfiber with a polyvinyl alcohol overlay,” Sensors and Actuators B: Chemical 263, 312–318 (2018).
[Crossref]

X. D. Zhang, C. Y. Liu, J. P. Liu, and J. R. Yang, “Single Modal Interference-Based Fiber-Optic Sensor for Simultaneous Measurement of Curvature and Strain With Dual-Differential Temperature Compensation,” IEEE Sens. J. 18(20), 8375–8380 (2018).
[Crossref]

2017 (3)

G. Woyessa, A. Fasano, C. Markos, H. K. Rasmussen, and O. Bang, “Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing,” IEEE Photonics Technol. Lett. 29(7), 575–578 (2017).
[Crossref]

N. Irawati, H. A. Rahman, M. Yasin, S. Al-Askari, B. A. Hamida, H. Ahmad, and S. W. Harun, “Relative humidity sensing using a PMMA doped agarose gel microfiber,” J. Lightwave Technol. 35(18), 3940–3944 (2017).
[Crossref]

H. W. Fu, Y. H. Jiang, J. J. Ding, and Z. L. Zhang, “Low Temperature Cross-Sensitivity Humidity Sensor Based on a U-Shaped Microfiber Interferometer,” IEEE Sens. J. 17(3), 644–649 (2017).
[Crossref]

2016 (7)

S. N. Wu, G. F. Yan, Z. G. Lian, X. Chen, B. Zhou, and S. L. He, “An open-cavity Fabry-Perot interferometer with PVA coating for simultaneous measurement of relative humidity and temperature,” Sensors and Actuators A: Physical 225, 50–56 (2016).
[Crossref]

C. L. Lee, Y. W. You, J. H. Dai, J. M. Hsu, and J. S. Horng, “Hygroscopic polymer microcavity fiber Fizeau interferometer incorporating a fiber Bragg grating for simultaneously sensing humidity and temperature,” Sensors and Actuators B: Chemical 222, 339–346 (2016).
[Crossref]

A. Urrutia, J. Goicoechea, A. L. Ricchiuti, D. Barrera, S. Sales, and F. J. Arregui, “Simultaneous measurement of humidity and temperature based on a partially coated optical fiber long period grating,” Sensors and Actuators B: Chemical 227, 135–141 (2016).
[Crossref]

J. Ascorbe, J. M. Corres, I. R. Matias, and F. J. Arregui, “High sensitivity humidity sensor based on cladding-etched optical fiber and lossy mode resonances,” Sensors and Actuators B: Chemical 233, 7–16 (2016).
[Crossref]

Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Fiber optic humidity sensor based on the graphene oxide/PVA composite film,” Opt. Commun. 372, 229–234 (2016).
[Crossref]

Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer coated with graphene oxide,” Sensors and Actuators B: Chemical 234, 503–509 (2016).
[Crossref]

L. P. Sun, J. Li, L. Jin, Y. Ran, and B. O. Guan, “High-birefringence microfiber Sagnac interferometer based humidity sensor,” Sensors and Actuators B: Chemical 231, 696–700 (2016).
[Crossref]

2014 (3)

H. Y. Chen, Z. T. Gu, and K. Gao, “Humidity sensor based on cascaded chirped long-period fiber gratings coated with TiO2/SnO2 composite films,” Sensors and Actuators B: Chemical 196, 18–22 (2014).
[Crossref]

R. Xiong, H. Y. Meng, Q. Q. Yao, B. Huang, Y. M. Liu, H. C. Xue, C. H. Tan, and X. G. Huang, “Simultaneous Measurement of Refractive Index and Temperature Based on Modal Interference,” IEEE Sens. J. 14(8), 2524–2528 (2014).
[Crossref]

Q. Q. Yao, H. Y. Meng, W. Wang, H. C. Xue, R. Xiong, B. Huang, C. H. Tan, and X. G. Huang, “Simultaneous measurement of refractive index and temperature based on a core-offset Mach-Zehnder interferometer combined with a fiber Bragg grating,” Sensors and Actuators A: Physical 209, 73–77 (2014).
[Crossref]

2013 (2)

D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
[Crossref]

L. Alwis, T. Sun, and K. T. V. Grattan, “Optical fibre-based sensor technology for humidity and moisture measurement: review of recent progress,” Measurement 46(10), 4052–4074 (2013).
[Crossref]

2012 (4)

T. Li, X. Y. Dong, C. C. Chan, C. L. Zhao, and P. Zu, “Humidity sensor based on multimode-fiber taper coated with polyvinyl alcohol interacting with a fibe Bragg grating,” IEEE Sens. J. 12(6), 2205–2208 (2012).
[Crossref]

W.C. Wong, C.C. Chan, L.H. Chen, T. Li, K.X. Lee, and K.C. Leong, “Polyvinyl alcohol coated photonic crystal optical fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 174, 563–569 (2012).
[Crossref]

Q. Z. Rong, X. G. Qiao, J. Zhang, R. H. Wang, M. L. Hu, and Z.Y. Feng, “Simultaneous Measurement for Displacement and Temperature Using Fiber Bragg Grating Cladding Mode Based on Core Diameter Mismatch,” J. Lightwave Technol. 30(11), 1645–1650 (2012).
[Crossref]

L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
[Crossref]

2008 (1)

2007 (1)

Ahmad, H.

Al-Askari, S.

Alwis, L.

L. Alwis, T. Sun, and K. T. V. Grattan, “Optical fibre-based sensor technology for humidity and moisture measurement: review of recent progress,” Measurement 46(10), 4052–4074 (2013).
[Crossref]

Ang, X. M.

L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
[Crossref]

Arregui, F. J.

A. Urrutia, J. Goicoechea, A. L. Ricchiuti, D. Barrera, S. Sales, and F. J. Arregui, “Simultaneous measurement of humidity and temperature based on a partially coated optical fiber long period grating,” Sensors and Actuators B: Chemical 227, 135–141 (2016).
[Crossref]

J. Ascorbe, J. M. Corres, I. R. Matias, and F. J. Arregui, “High sensitivity humidity sensor based on cladding-etched optical fiber and lossy mode resonances,” Sensors and Actuators B: Chemical 233, 7–16 (2016).
[Crossref]

Ascorbe, J.

J. Ascorbe, J. M. Corres, I. R. Matias, and F. J. Arregui, “High sensitivity humidity sensor based on cladding-etched optical fiber and lossy mode resonances,” Sensors and Actuators B: Chemical 233, 7–16 (2016).
[Crossref]

Bai, X. H.

C. Bian, J. Wang, X. H. Bai, M. L. Hu, and T. T. Gang, “Optical fiber based on humidity sensor with improved sensitivity for monitoring applications,” Opt. Laser Technol. 130, 106342 (2020).
[Crossref]

Bai, Y. T.

Y. T. Bai, Y. P. Miao, H. M. Zhang, and J. Q. Yao, “Simultaneous measurement of relative humidity and temperature using a microfiber coupler coated with molybdenum disulfide nanosheets,” Opt. Mater Express 9(7), 2846–2858 (2019).
[Crossref]

Bai, Z. Y .

D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
[Crossref]

Balamurali, P .

L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
[Crossref]

Bang, O.

G. Woyessa, A. Fasano, C. Markos, H. K. Rasmussen, and O. Bang, “Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing,” IEEE Photonics Technol. Lett. 29(7), 575–578 (2017).
[Crossref]

Barrera, D.

A. Urrutia, J. Goicoechea, A. L. Ricchiuti, D. Barrera, S. Sales, and F. J. Arregui, “Simultaneous measurement of humidity and temperature based on a partially coated optical fiber long period grating,” Sensors and Actuators B: Chemical 227, 135–141 (2016).
[Crossref]

Bian, C.

J. Wang, C. Bian, T. T. Gang, and M. L. Hu, “High-sensitive Mach-Zehnder interferometer for humidity measurements based on concatenating single-mode concave cone and core-offset,” Optik 208, 164465 (2020).
[Crossref]

C. Bian, J. Wang, X. H. Bai, M. L. Hu, and T. T. Gang, “Optical fiber based on humidity sensor with improved sensitivity for monitoring applications,” Opt. Laser Technol. 130, 106342 (2020).
[Crossref]

C. Bian, Y. F. Cheng, W. H. Zhu, R. X. Tong, M. L. Hu, and T. T. Gang, “A Novel Optical Fiber Mach-Zehnder Interferometer Based on the Calcium Alginate Hydrogel Film for Humidity Sensing,” IEEE Sens. J. 20(11), 5759–5765 (2020).
[Crossref]

Chan, C. C.

Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
[Crossref]

L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
[Crossref]

T. Li, X. Y. Dong, C. C. Chan, C. L. Zhao, and P. Zu, “Humidity sensor based on multimode-fiber taper coated with polyvinyl alcohol interacting with a fibe Bragg grating,” IEEE Sens. J. 12(6), 2205–2208 (2012).
[Crossref]

Chan, C.C.

W.C. Wong, C.C. Chan, L.H. Chen, T. Li, K.X. Lee, and K.C. Leong, “Polyvinyl alcohol coated photonic crystal optical fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 174, 563–569 (2012).
[Crossref]

Chen, C.

G. J. Huang, Y. J. Li, C. Chen, Z. Z. Yue, W. Zhai, M. D. Li, and B. Yang, “Hydrogen Sulfide Gas Sensor Based on Titanium Dioxide/Amino-Functionalized Graphene Quantum Dots Coated Photonic Crystal Fiber,” J. Phys. D: Appl. Phys. 53(32), 325102 (2020).
[Crossref]

Chen, G. L.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Chen, H. Y.

H. Y. Chen, Z. T. Gu, and K. Gao, “Humidity sensor based on cascaded chirped long-period fiber gratings coated with TiO2/SnO2 composite films,” Sensors and Actuators B: Chemical 196, 18–22 (2014).
[Crossref]

Chen, L. H.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
[Crossref]

Chen, L.H.

W.C. Wong, C.C. Chan, L.H. Chen, T. Li, K.X. Lee, and K.C. Leong, “Polyvinyl alcohol coated photonic crystal optical fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 174, 563–569 (2012).
[Crossref]

Chen, M. Q.

R. J. Tong, Y. Zhao, M. Q. Chen, and Y. Peng, “Multimode interferometer based on no-core fiber with GQDs-PVA composite coating for relative humidity sensing,” Opt. Fiber Technol. 48, 242–247 (2019).
[Crossref]

Y. Zhao, R. J. Tong, M. Q. Chen, and F. Xia, “Relative Humidity sensor based on Hollow Core Fiber Filled with GQDs-PVA,” Sensors and Actuators B: Chemical 284, 96–102 (2019).
[Crossref]

Y. Zhao, Y. Peng, M. Q. Chen, and R. J. Tong, “Humidity sensor based on unsymmetrical U-shaped microfiber with a polyvinyl alcohol overlay,” Sensors and Actuators B: Chemical 263, 312–318 (2018).
[Crossref]

Chen, N.

N. Chen, X. Zhou, and X. G. Li, “Highly Sensitive Humidity Sensor With Low-Temperature Cross-Sensitivity Based on a Polyvinyl Alcohol Coating Tapered Fiber,” IEEE Trans. Instrum. Meas. 70, 9503308 (2021).
[Crossref]

Chen, X.

S. N. Wu, G. F. Yan, Z. G. Lian, X. Chen, B. Zhou, and S. L. He, “An open-cavity Fabry-Perot interferometer with PVA coating for simultaneous measurement of relative humidity and temperature,” Sensors and Actuators A: Physical 225, 50–56 (2016).
[Crossref]

Chen, Z.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Cheng, J. N.

Cheng, Y. F.

C. Bian, Y. F. Cheng, W. H. Zhu, R. X. Tong, M. L. Hu, and T. T. Gang, “A Novel Optical Fiber Mach-Zehnder Interferometer Based on the Calcium Alginate Hydrogel Film for Humidity Sensing,” IEEE Sens. J. 20(11), 5759–5765 (2020).
[Crossref]

Choi, H. Y.

Chung, Y.

Corres, J. M.

J. Ascorbe, J. M. Corres, I. R. Matias, and F. J. Arregui, “High sensitivity humidity sensor based on cladding-etched optical fiber and lossy mode resonances,” Sensors and Actuators B: Chemical 233, 7–16 (2016).
[Crossref]

Dai, J. H.

C. L. Lee, Y. W. You, J. H. Dai, J. M. Hsu, and J. S. Horng, “Hygroscopic polymer microcavity fiber Fizeau interferometer incorporating a fiber Bragg grating for simultaneously sensing humidity and temperature,” Sensors and Actuators B: Chemical 222, 339–346 (2016).
[Crossref]

Deng, S.

Deng, S. Y .

S. Liu, H. Y . Meng, S. Y . Deng, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Fiber humidity sensor based on a graphene-coated core-offset Mach-Zehnder interferometer,” IEEE Sens. Lett. 2(3), 1–4 (2018).
[Crossref]

Ding, J. J.

H. W. Fu, Y. H. Jiang, J. J. Ding, and Z. L. Zhang, “Low Temperature Cross-Sensitivity Humidity Sensor Based on a U-Shaped Microfiber Interferometer,” IEEE Sens. J. 17(3), 644–649 (2017).
[Crossref]

Dong, H. Z.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Dong, X. Y.

Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
[Crossref]

T. Li, X. Y. Dong, C. C. Chan, C. L. Zhao, and P. Zu, “Humidity sensor based on multimode-fiber taper coated with polyvinyl alcohol interacting with a fibe Bragg grating,” IEEE Sens. J. 12(6), 2205–2208 (2012).
[Crossref]

Du, Y . Y .

D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
[Crossref]

Fan, X

Fan, X.

Fan, X. F.

Q. Z. Wang, H. Y. Meng, X. F. Fan, M. Q. Zhou, F. X. Liu, C. Y. Liu, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structur,” Rev. Sci. Instrum. 91(1), 015006 (2020).
[Crossref]

Fang, W. X.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Fasano, A.

G. Woyessa, A. Fasano, C. Markos, H. K. Rasmussen, and O. Bang, “Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing,” IEEE Photonics Technol. Lett. 29(7), 575–578 (2017).
[Crossref]

Feng, D. Y .

D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
[Crossref]

Feng, Z. Y.

D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
[Crossref]

Feng, Z.Y.

Fu, H. W.

H. W. Fu, Y. H. Jiang, J. J. Ding, and Z. L. Zhang, “Low Temperature Cross-Sensitivity Humidity Sensor Based on a U-Shaped Microfiber Interferometer,” IEEE Sens. J. 17(3), 644–649 (2017).
[Crossref]

Gang, T. T.

J. Wang, C. Bian, T. T. Gang, and M. L. Hu, “High-sensitive Mach-Zehnder interferometer for humidity measurements based on concatenating single-mode concave cone and core-offset,” Optik 208, 164465 (2020).
[Crossref]

C. Bian, Y. F. Cheng, W. H. Zhu, R. X. Tong, M. L. Hu, and T. T. Gang, “A Novel Optical Fiber Mach-Zehnder Interferometer Based on the Calcium Alginate Hydrogel Film for Humidity Sensing,” IEEE Sens. J. 20(11), 5759–5765 (2020).
[Crossref]

C. Bian, J. Wang, X. H. Bai, M. L. Hu, and T. T. Gang, “Optical fiber based on humidity sensor with improved sensitivity for monitoring applications,” Opt. Laser Technol. 130, 106342 (2020).
[Crossref]

L. Liang, H. Sun, N. Liu, H. Luo, T. T. Gang, Q. Z. Rong, X. G. Qiao, and M. L. Hu, “High-sensitivity optical fiber relative humidity probe with temperature calibration ability,” Appl. Opt. 57(4), 872–876 (2018).
[Crossref]

Gao, K.

H. Y. Chen, Z. T. Gu, and K. Gao, “Humidity sensor based on cascaded chirped long-period fiber gratings coated with TiO2/SnO2 composite films,” Sensors and Actuators B: Chemical 196, 18–22 (2014).
[Crossref]

Gao, W. L

Goicoechea, J.

A. Urrutia, J. Goicoechea, A. L. Ricchiuti, D. Barrera, S. Sales, and F. J. Arregui, “Simultaneous measurement of humidity and temperature based on a partially coated optical fiber long period grating,” Sensors and Actuators B: Chemical 227, 135–141 (2016).
[Crossref]

Grattan, K. T. V.

L. Alwis, T. Sun, and K. T. V. Grattan, “Optical fibre-based sensor technology for humidity and moisture measurement: review of recent progress,” Measurement 46(10), 4052–4074 (2013).
[Crossref]

Gu, Z. T.

H. Y. Chen, Z. T. Gu, and K. Gao, “Humidity sensor based on cascaded chirped long-period fiber gratings coated with TiO2/SnO2 composite films,” Sensors and Actuators B: Chemical 196, 18–22 (2014).
[Crossref]

Guan, B. O.

L. P. Sun, J. Li, L. Jin, Y. Ran, and B. O. Guan, “High-birefringence microfiber Sagnac interferometer based humidity sensor,” Sensors and Actuators B: Chemical 231, 696–700 (2016).
[Crossref]

Guan, H. Y.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Guan, J. W.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Guo, X.

Hamida, B. A.

Harun, S. W.

He, S. L.

S. N. Wu, G. F. Yan, Z. G. Lian, X. Chen, B. Zhou, and S. L. He, “An open-cavity Fabry-Perot interferometer with PVA coating for simultaneous measurement of relative humidity and temperature,” Sensors and Actuators A: Physical 225, 50–56 (2016).
[Crossref]

Horng, J. S.

C. L. Lee, Y. W. You, J. H. Dai, J. M. Hsu, and J. S. Horng, “Hygroscopic polymer microcavity fiber Fizeau interferometer incorporating a fiber Bragg grating for simultaneously sensing humidity and temperature,” Sensors and Actuators B: Chemical 222, 339–346 (2016).
[Crossref]

Hsu, J. M.

C. L. Lee, Y. W. You, J. H. Dai, J. M. Hsu, and J. S. Horng, “Hygroscopic polymer microcavity fiber Fizeau interferometer incorporating a fiber Bragg grating for simultaneously sensing humidity and temperature,” Sensors and Actuators B: Chemical 222, 339–346 (2016).
[Crossref]

Hu, M. L.

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Liu, F. X.

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X. D. Zhang, C. Y. Liu, J. P. Liu, and J. R. Yang, “Single Modal Interference-Based Fiber-Optic Sensor for Simultaneous Measurement of Curvature and Strain With Dual-Differential Temperature Compensation,” IEEE Sens. J. 18(20), 8375–8380 (2018).
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Liu, S.

S. Liu, H. Y . Meng, S. Y . Deng, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Fiber humidity sensor based on a graphene-coated core-offset Mach-Zehnder interferometer,” IEEE Sens. Lett. 2(3), 1–4 (2018).
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Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
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Liu, Y. M.

R. Xiong, H. Y. Meng, Q. Q. Yao, B. Huang, Y. M. Liu, H. C. Xue, C. H. Tan, and X. G. Huang, “Simultaneous Measurement of Refractive Index and Temperature Based on Modal Interference,” IEEE Sens. J. 14(8), 2524–2528 (2014).
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Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer coated with graphene oxide,” Sensors and Actuators B: Chemical 234, 503–509 (2016).
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Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Fiber optic humidity sensor based on the graphene oxide/PVA composite film,” Opt. Commun. 372, 229–234 (2016).
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Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
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Luo, H.

Ma, Q. F.

P. P. Wang, K. Ni, B. W. Wang, Q. F. Ma, and W. J. Tian, “Methylcellulose Coated Humidity Sensor Based on Michelson Interferometer with Thin-core Fiber,” Sensors and Actuators A: Physical 288, 75–78 (2019).
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Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
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G. Woyessa, A. Fasano, C. Markos, H. K. Rasmussen, and O. Bang, “Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing,” IEEE Photonics Technol. Lett. 29(7), 575–578 (2017).
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Meng, H. Y .

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Q. Z. Wang, H. Y. Meng, X. F. Fan, M. Q. Zhou, F. X. Liu, C. Y. Liu, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structur,” Rev. Sci. Instrum. 91(1), 015006 (2020).
[Crossref]

R. Xiong, H. Y. Meng, Q. Q. Yao, B. Huang, Y. M. Liu, H. C. Xue, C. H. Tan, and X. G. Huang, “Simultaneous Measurement of Refractive Index and Temperature Based on Modal Interference,” IEEE Sens. J. 14(8), 2524–2528 (2014).
[Crossref]

Q. Q. Yao, H. Y. Meng, W. Wang, H. C. Xue, R. Xiong, B. Huang, C. H. Tan, and X. G. Huang, “Simultaneous measurement of refractive index and temperature based on a core-offset Mach-Zehnder interferometer combined with a fiber Bragg grating,” Sensors and Actuators A: Physical 209, 73–77 (2014).
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Menon, R.

L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
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Y. T. Bai, Y. P. Miao, H. M. Zhang, and J. Q. Yao, “Simultaneous measurement of relative humidity and temperature using a microfiber coupler coated with molybdenum disulfide nanosheets,” Opt. Mater Express 9(7), 2846–2858 (2019).
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Moon, S.

Neu, B.

L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
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Nguyen, L.V.

Ni, K.

P. P. Wang, K. Ni, B. W. Wang, Q. F. Ma, and W. J. Tian, “Methylcellulose Coated Humidity Sensor Based on Michelson Interferometer with Thin-core Fiber,” Sensors and Actuators A: Physical 288, 75–78 (2019).
[Crossref]

Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
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Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
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Peng, Y.

R. J. Tong, Y. Zhao, M. Q. Chen, and Y. Peng, “Multimode interferometer based on no-core fiber with GQDs-PVA composite coating for relative humidity sensing,” Opt. Fiber Technol. 48, 242–247 (2019).
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Y. Zhao, Y. Peng, M. Q. Chen, and R. J. Tong, “Humidity sensor based on unsymmetrical U-shaped microfiber with a polyvinyl alcohol overlay,” Sensors and Actuators B: Chemical 263, 312–318 (2018).
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Qiao, X. G.

Qin, J.

Rahman, H. A.

Ran, Y.

L. P. Sun, J. Li, L. Jin, Y. Ran, and B. O. Guan, “High-birefringence microfiber Sagnac interferometer based humidity sensor,” Sensors and Actuators B: Chemical 231, 696–700 (2016).
[Crossref]

Rasmussen, H. K.

G. Woyessa, A. Fasano, C. Markos, H. K. Rasmussen, and O. Bang, “Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing,” IEEE Photonics Technol. Lett. 29(7), 575–578 (2017).
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Sales, S.

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L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
[Crossref]

Shen, C. Y.

Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Fiber optic humidity sensor based on the graphene oxide/PVA composite film,” Opt. Commun. 372, 229–234 (2016).
[Crossref]

Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer coated with graphene oxide,” Sensors and Actuators B: Chemical 234, 503–509 (2016).
[Crossref]

Shen, H.

Shentu, F. Y.

Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Fiber optic humidity sensor based on the graphene oxide/PVA composite film,” Opt. Commun. 372, 229–234 (2016).
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Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer coated with graphene oxide,” Sensors and Actuators B: Chemical 234, 503–509 (2016).
[Crossref]

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Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
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D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
[Crossref]

Sun, H.

L. Liang, H. Sun, N. Liu, H. Luo, T. T. Gang, Q. Z. Rong, X. G. Qiao, and M. L. Hu, “High-sensitivity optical fiber relative humidity probe with temperature calibration ability,” Appl. Opt. 57(4), 872–876 (2018).
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D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
[Crossref]

Sun, L. P.

L. P. Sun, J. Li, L. Jin, Y. Ran, and B. O. Guan, “High-birefringence microfiber Sagnac interferometer based humidity sensor,” Sensors and Actuators B: Chemical 231, 696–700 (2016).
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L. Alwis, T. Sun, and K. T. V. Grattan, “Optical fibre-based sensor technology for humidity and moisture measurement: review of recent progress,” Measurement 46(10), 4052–4074 (2013).
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Tan, C.

Tan, C. H.

Q. Z. Wang, H. Y. Meng, X. F. Fan, M. Q. Zhou, F. X. Liu, C. Y. Liu, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structur,” Rev. Sci. Instrum. 91(1), 015006 (2020).
[Crossref]

S. Liu, H. Y . Meng, S. Y . Deng, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Fiber humidity sensor based on a graphene-coated core-offset Mach-Zehnder interferometer,” IEEE Sens. Lett. 2(3), 1–4 (2018).
[Crossref]

Q. Q. Yao, H. Y. Meng, W. Wang, H. C. Xue, R. Xiong, B. Huang, C. H. Tan, and X. G. Huang, “Simultaneous measurement of refractive index and temperature based on a core-offset Mach-Zehnder interferometer combined with a fiber Bragg grating,” Sensors and Actuators A: Physical 209, 73–77 (2014).
[Crossref]

R. Xiong, H. Y. Meng, Q. Q. Yao, B. Huang, Y. M. Liu, H. C. Xue, C. H. Tan, and X. G. Huang, “Simultaneous Measurement of Refractive Index and Temperature Based on Modal Interference,” IEEE Sens. J. 14(8), 2524–2528 (2014).
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Tang, J. Y.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Tian, W. J.

P. P. Wang, K. Ni, B. W. Wang, Q. F. Ma, and W. J. Tian, “Methylcellulose Coated Humidity Sensor Based on Michelson Interferometer with Thin-core Fiber,” Sensors and Actuators A: Physical 288, 75–78 (2019).
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Tong, R. J.

R. J. Tong, Y. Zhao, H. K. Zheng, and F. Xia, “Simultaneous measurement of temperature and relative humidity by compact Mach-Zehnder interferometer and Fabry-Perot interferometer,” Measurement 155, 107499 (2020).
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Y. Zhao, R. J. Tong, M. Q. Chen, and F. Xia, “Relative Humidity sensor based on Hollow Core Fiber Filled with GQDs-PVA,” Sensors and Actuators B: Chemical 284, 96–102 (2019).
[Crossref]

R. J. Tong, Y. Zhao, M. Q. Chen, and Y. Peng, “Multimode interferometer based on no-core fiber with GQDs-PVA composite coating for relative humidity sensing,” Opt. Fiber Technol. 48, 242–247 (2019).
[Crossref]

Y. Zhao, Y. Peng, M. Q. Chen, and R. J. Tong, “Humidity sensor based on unsymmetrical U-shaped microfiber with a polyvinyl alcohol overlay,” Sensors and Actuators B: Chemical 263, 312–318 (2018).
[Crossref]

Tong, R. X.

C. Bian, Y. F. Cheng, W. H. Zhu, R. X. Tong, M. L. Hu, and T. T. Gang, “A Novel Optical Fiber Mach-Zehnder Interferometer Based on the Calcium Alginate Hydrogel Film for Humidity Sensing,” IEEE Sens. J. 20(11), 5759–5765 (2020).
[Crossref]

Tong, Z. R.

J. T. Zhang, Z. R. Tong, W. H. Zhang, Y. M. Zhao, and J. X. Li, “Research on simultaneous temperature and relative humidity measurement based on tapered PCF Mach-Zehnder interferometer,” Opt. Fiber Technol. 61, 102408 (2021).
[Crossref]

Y. M. Zhong, Z. R. Tong, W. H. Zhang, J. Qin, and W. L Gao, “Humidity and temperature sensor based on a Mach-Zehnder interferometer with a pokal taper and peanut taper,” Appl. Opt. 58(29), 7981–7986 (2019).
[Crossref]

Tou, Z. Q.

Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
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Urrutia, A.

A. Urrutia, J. Goicoechea, A. L. Ricchiuti, D. Barrera, S. Sales, and F. J. Arregui, “Simultaneous measurement of humidity and temperature based on a partially coated optical fiber long period grating,” Sensors and Actuators B: Chemical 227, 135–141 (2016).
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Wang, B. W.

P. P. Wang, K. Ni, B. W. Wang, Q. F. Ma, and W. J. Tian, “Methylcellulose Coated Humidity Sensor Based on Michelson Interferometer with Thin-core Fiber,” Sensors and Actuators A: Physical 288, 75–78 (2019).
[Crossref]

Wang, F.

Wang, F. Q.

Q. Z. Wang, H. Y. Meng, X. F. Fan, M. Q. Zhou, F. X. Liu, C. Y. Liu, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structur,” Rev. Sci. Instrum. 91(1), 015006 (2020).
[Crossref]

S. Liu, H. Y . Meng, S. Y . Deng, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Fiber humidity sensor based on a graphene-coated core-offset Mach-Zehnder interferometer,” IEEE Sens. Lett. 2(3), 1–4 (2018).
[Crossref]

Wang, H. C.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Wang, J.

J. Wang, “Numerical simulation and optimal design of photonic crystal fiber hygrometer coated with PVA/GO composite film,” Opt. Fiber Technol. 63, 102491 (2021).
[Crossref]

C. Bian, J. Wang, X. H. Bai, M. L. Hu, and T. T. Gang, “Optical fiber based on humidity sensor with improved sensitivity for monitoring applications,” Opt. Laser Technol. 130, 106342 (2020).
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J. Wang, C. Bian, T. T. Gang, and M. L. Hu, “High-sensitive Mach-Zehnder interferometer for humidity measurements based on concatenating single-mode concave cone and core-offset,” Optik 208, 164465 (2020).
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Wang, P. P.

P. P. Wang, K. Ni, B. W. Wang, Q. F. Ma, and W. J. Tian, “Methylcellulose Coated Humidity Sensor Based on Michelson Interferometer with Thin-core Fiber,” Sensors and Actuators A: Physical 288, 75–78 (2019).
[Crossref]

Wang, Q

Wang, Q.

Wang, Q. Z.

Q. Z. Wang, H. Y. Meng, X. F. Fan, M. Q. Zhou, F. X. Liu, C. Y. Liu, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structur,” Rev. Sci. Instrum. 91(1), 015006 (2020).
[Crossref]

Wang, R. H.

Wang, W.

Q. Q. Yao, H. Y. Meng, W. Wang, H. C. Xue, R. Xiong, B. Huang, C. H. Tan, and X. G. Huang, “Simultaneous measurement of refractive index and temperature based on a core-offset Mach-Zehnder interferometer combined with a fiber Bragg grating,” Sensors and Actuators A: Physical 209, 73–77 (2014).
[Crossref]

Wang, X.

Wang, Y . P.

D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
[Crossref]

Wang, Y. Q.

Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Fiber optic humidity sensor based on the graphene oxide/PVA composite film,” Opt. Commun. 372, 229–234 (2016).
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Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer coated with graphene oxide,” Sensors and Actuators B: Chemical 234, 503–509 (2016).
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Wang, Y. R.

Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
[Crossref]

Wei, Z.

Wei, Z. C.

Q. Z. Wang, H. Y. Meng, X. F. Fan, M. Q. Zhou, F. X. Liu, C. Y. Liu, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structur,” Rev. Sci. Instrum. 91(1), 015006 (2020).
[Crossref]

S. Liu, H. Y . Meng, S. Y . Deng, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Fiber humidity sensor based on a graphene-coated core-offset Mach-Zehnder interferometer,” IEEE Sens. Lett. 2(3), 1–4 (2018).
[Crossref]

Wong, W. C.

L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
[Crossref]

Wong, W.C.

W.C. Wong, C.C. Chan, L.H. Chen, T. Li, K.X. Lee, and K.C. Leong, “Polyvinyl alcohol coated photonic crystal optical fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 174, 563–569 (2012).
[Crossref]

Woyessa, G.

G. Woyessa, A. Fasano, C. Markos, H. K. Rasmussen, and O. Bang, “Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing,” IEEE Photonics Technol. Lett. 29(7), 575–578 (2017).
[Crossref]

Wu, S. N.

S. N. Wu, G. F. Yan, Z. G. Lian, X. Chen, B. Zhou, and S. L. He, “An open-cavity Fabry-Perot interferometer with PVA coating for simultaneous measurement of relative humidity and temperature,” Sensors and Actuators A: Physical 225, 50–56 (2016).
[Crossref]

Xia, F.

R. J. Tong, Y. Zhao, H. K. Zheng, and F. Xia, “Simultaneous measurement of temperature and relative humidity by compact Mach-Zehnder interferometer and Fabry-Perot interferometer,” Measurement 155, 107499 (2020).
[Crossref]

Y. Zhao, R. J. Tong, M. Q. Chen, and F. Xia, “Relative Humidity sensor based on Hollow Core Fiber Filled with GQDs-PVA,” Sensors and Actuators B: Chemical 284, 96–102 (2019).
[Crossref]

Xiao, Y.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Xiong, R.

Q. Q. Yao, H. Y. Meng, W. Wang, H. C. Xue, R. Xiong, B. Huang, C. H. Tan, and X. G. Huang, “Simultaneous measurement of refractive index and temperature based on a core-offset Mach-Zehnder interferometer combined with a fiber Bragg grating,” Sensors and Actuators A: Physical 209, 73–77 (2014).
[Crossref]

R. Xiong, H. Y. Meng, Q. Q. Yao, B. Huang, Y. M. Liu, H. C. Xue, C. H. Tan, and X. G. Huang, “Simultaneous Measurement of Refractive Index and Temperature Based on Modal Interference,” IEEE Sens. J. 14(8), 2524–2528 (2014).
[Crossref]

Xue, H. C.

R. Xiong, H. Y. Meng, Q. Q. Yao, B. Huang, Y. M. Liu, H. C. Xue, C. H. Tan, and X. G. Huang, “Simultaneous Measurement of Refractive Index and Temperature Based on Modal Interference,” IEEE Sens. J. 14(8), 2524–2528 (2014).
[Crossref]

Q. Q. Yao, H. Y. Meng, W. Wang, H. C. Xue, R. Xiong, B. Huang, C. H. Tan, and X. G. Huang, “Simultaneous measurement of refractive index and temperature based on a core-offset Mach-Zehnder interferometer combined with a fiber Bragg grating,” Sensors and Actuators A: Physical 209, 73–77 (2014).
[Crossref]

Yan, G. F.

S. N. Wu, G. F. Yan, Z. G. Lian, X. Chen, B. Zhou, and S. L. He, “An open-cavity Fabry-Perot interferometer with PVA coating for simultaneous measurement of relative humidity and temperature,” Sensors and Actuators A: Physical 225, 50–56 (2016).
[Crossref]

Yang, B.

G. J. Huang, Y. J. Li, C. Chen, Z. Z. Yue, W. Zhai, M. D. Li, and B. Yang, “Hydrogen Sulfide Gas Sensor Based on Titanium Dioxide/Amino-Functionalized Graphene Quantum Dots Coated Photonic Crystal Fiber,” J. Phys. D: Appl. Phys. 53(32), 325102 (2020).
[Crossref]

Yang, J. R.

X. D. Zhang, C. Y. Liu, J. P. Liu, and J. R. Yang, “Single Modal Interference-Based Fiber-Optic Sensor for Simultaneous Measurement of Curvature and Strain With Dual-Differential Temperature Compensation,” IEEE Sens. J. 18(20), 8375–8380 (2018).
[Crossref]

Yao, J. Q.

Y. T. Bai, Y. P. Miao, H. M. Zhang, and J. Q. Yao, “Simultaneous measurement of relative humidity and temperature using a microfiber coupler coated with molybdenum disulfide nanosheets,” Opt. Mater Express 9(7), 2846–2858 (2019).
[Crossref]

Yao, Q. Q.

Q. Q. Yao, H. Y. Meng, W. Wang, H. C. Xue, R. Xiong, B. Huang, C. H. Tan, and X. G. Huang, “Simultaneous measurement of refractive index and temperature based on a core-offset Mach-Zehnder interferometer combined with a fiber Bragg grating,” Sensors and Actuators A: Physical 209, 73–77 (2014).
[Crossref]

R. Xiong, H. Y. Meng, Q. Q. Yao, B. Huang, Y. M. Liu, H. C. Xue, C. H. Tan, and X. G. Huang, “Simultaneous Measurement of Refractive Index and Temperature Based on Modal Interference,” IEEE Sens. J. 14(8), 2524–2528 (2014).
[Crossref]

Yasin, M.

You, Y. W.

C. L. Lee, Y. W. You, J. H. Dai, J. M. Hsu, and J. S. Horng, “Hygroscopic polymer microcavity fiber Fizeau interferometer incorporating a fiber Bragg grating for simultaneously sensing humidity and temperature,” Sensors and Actuators B: Chemical 222, 339–346 (2016).
[Crossref]

Yu, J. H.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Yue, Z. Z.

G. J. Huang, Y. J. Li, C. Chen, Z. Z. Yue, W. Zhai, M. D. Li, and B. Yang, “Hydrogen Sulfide Gas Sensor Based on Titanium Dioxide/Amino-Functionalized Graphene Quantum Dots Coated Photonic Crystal Fiber,” J. Phys. D: Appl. Phys. 53(32), 325102 (2020).
[Crossref]

Zhai, W.

G. J. Huang, Y. J. Li, C. Chen, Z. Z. Yue, W. Zhai, M. D. Li, and B. Yang, “Hydrogen Sulfide Gas Sensor Based on Titanium Dioxide/Amino-Functionalized Graphene Quantum Dots Coated Photonic Crystal Fiber,” J. Phys. D: Appl. Phys. 53(32), 325102 (2020).
[Crossref]

Zhang, H. M.

Y. T. Bai, Y. P. Miao, H. M. Zhang, and J. Q. Yao, “Simultaneous measurement of relative humidity and temperature using a microfiber coupler coated with molybdenum disulfide nanosheets,” Opt. Mater Express 9(7), 2846–2858 (2019).
[Crossref]

Zhang, J.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
[Crossref]

Q. Z. Rong, X. G. Qiao, J. Zhang, R. H. Wang, M. L. Hu, and Z.Y. Feng, “Simultaneous Measurement for Displacement and Temperature Using Fiber Bragg Grating Cladding Mode Based on Core Diameter Mismatch,” J. Lightwave Technol. 30(11), 1645–1650 (2012).
[Crossref]

Zhang, J. T.

J. T. Zhang, Z. R. Tong, W. H. Zhang, Y. M. Zhao, and J. X. Li, “Research on simultaneous temperature and relative humidity measurement based on tapered PCF Mach-Zehnder interferometer,” Opt. Fiber Technol. 61, 102408 (2021).
[Crossref]

Zhang, W. H.

J. T. Zhang, Z. R. Tong, W. H. Zhang, Y. M. Zhao, and J. X. Li, “Research on simultaneous temperature and relative humidity measurement based on tapered PCF Mach-Zehnder interferometer,” Opt. Fiber Technol. 61, 102408 (2021).
[Crossref]

Y. M. Zhong, Z. R. Tong, W. H. Zhang, J. Qin, and W. L Gao, “Humidity and temperature sensor based on a Mach-Zehnder interferometer with a pokal taper and peanut taper,” Appl. Opt. 58(29), 7981–7986 (2019).
[Crossref]

Zhang, X. D.

X. D. Zhang, C. Y. Liu, J. P. Liu, and J. R. Yang, “Single Modal Interference-Based Fiber-Optic Sensor for Simultaneous Measurement of Curvature and Strain With Dual-Differential Temperature Compensation,” IEEE Sens. J. 18(20), 8375–8380 (2018).
[Crossref]

Zhang, Z. L.

H. W. Fu, Y. H. Jiang, J. J. Ding, and Z. L. Zhang, “Low Temperature Cross-Sensitivity Humidity Sensor Based on a U-Shaped Microfiber Interferometer,” IEEE Sens. J. 17(3), 644–649 (2017).
[Crossref]

Zhao, C. L.

T. Li, X. Y. Dong, C. C. Chan, C. L. Zhao, and P. Zu, “Humidity sensor based on multimode-fiber taper coated with polyvinyl alcohol interacting with a fibe Bragg grating,” IEEE Sens. J. 12(6), 2205–2208 (2012).
[Crossref]

Zhao, Y.

R. J. Tong, Y. Zhao, H. K. Zheng, and F. Xia, “Simultaneous measurement of temperature and relative humidity by compact Mach-Zehnder interferometer and Fabry-Perot interferometer,” Measurement 155, 107499 (2020).
[Crossref]

R. J. Tong, Y. Zhao, M. Q. Chen, and Y. Peng, “Multimode interferometer based on no-core fiber with GQDs-PVA composite coating for relative humidity sensing,” Opt. Fiber Technol. 48, 242–247 (2019).
[Crossref]

Y. Zhao, R. J. Tong, M. Q. Chen, and F. Xia, “Relative Humidity sensor based on Hollow Core Fiber Filled with GQDs-PVA,” Sensors and Actuators B: Chemical 284, 96–102 (2019).
[Crossref]

Y. Zhao, Y. Peng, M. Q. Chen, and R. J. Tong, “Humidity sensor based on unsymmetrical U-shaped microfiber with a polyvinyl alcohol overlay,” Sensors and Actuators B: Chemical 263, 312–318 (2018).
[Crossref]

Zhao, Y. M.

J. T. Zhang, Z. R. Tong, W. H. Zhang, Y. M. Zhao, and J. X. Li, “Research on simultaneous temperature and relative humidity measurement based on tapered PCF Mach-Zehnder interferometer,” Opt. Fiber Technol. 61, 102408 (2021).
[Crossref]

Zheng, H. K.

R. J. Tong, Y. Zhao, H. K. Zheng, and F. Xia, “Simultaneous measurement of temperature and relative humidity by compact Mach-Zehnder interferometer and Fabry-Perot interferometer,” Measurement 155, 107499 (2020).
[Crossref]

Zhong, Y. M.

Zhou, B.

S. N. Wu, G. F. Yan, Z. G. Lian, X. Chen, B. Zhou, and S. L. He, “An open-cavity Fabry-Perot interferometer with PVA coating for simultaneous measurement of relative humidity and temperature,” Sensors and Actuators A: Physical 225, 50–56 (2016).
[Crossref]

Zhou, J. J.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Zhou, M

Zhou, M.

Zhou, M. H.

Q. F. Ma, Z. Q. Tou, K. Ni, Y. Y. Lim, Y. F. Lin, Y. R. Wang, M. H. Zhou, F. F. Shi, L. Niu, X. Y. Dong, and C. C. Chan, “Carbon-nanotube/Polyvinyl alcohol coated thin core fiber sensor for humidity measurement,” Sensors and Actuators B: Chemical 257, 800–806 (2018).
[Crossref]

Zhou, M. Q.

Q. Z. Wang, H. Y. Meng, X. F. Fan, M. Q. Zhou, F. X. Liu, C. Y. Liu, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structur,” Rev. Sci. Instrum. 91(1), 015006 (2020).
[Crossref]

Zhou, X.

N. Chen, X. Zhou, and X. G. Li, “Highly Sensitive Humidity Sensor With Low-Temperature Cross-Sensitivity Based on a Polyvinyl Alcohol Coating Tapered Fiber,” IEEE Trans. Instrum. Meas. 70, 9503308 (2021).
[Crossref]

Zhu, W. G.

Y. M. Huang, W. G. Zhu, Z. B. Li, G. L. Chen, L. H. Chen, J. J. Zhou, H. Lin, J. W. Guan, W. X. Fang, X. Liu, H. Z. Dong, J. Y. Tang, H. Y. Guan, H. H. Lu, Y. Xiao, J. Zhang, H. C. Wang, Z. Chen, and J. H. Yu, “High-performance fibre-optic humidity sensor based on a side-polished fibre wavelength selectively coupled with graphene oxide film,” Sensors and Actuators B: Chemical 255, 57–69 (2018).
[Crossref]

Zhu, W. H.

C. Bian, Y. F. Cheng, W. H. Zhu, R. X. Tong, M. L. Hu, and T. T. Gang, “A Novel Optical Fiber Mach-Zehnder Interferometer Based on the Calcium Alginate Hydrogel Film for Humidity Sensing,” IEEE Sens. J. 20(11), 5759–5765 (2020).
[Crossref]

Zu, P .

L. H. Chen, T. Li, C. C. Chan, R. Menon, P . Balamurali, M. Shaillender, B. Neu, X. M. Ang, P . Zu, W. C. Wong, and K. C. Leong, “Chitosan based fiber-optic Fabry-Perot humidity sensor,” Sensors and Actuators B: Chemical 169, 167–172 (2012).
[Crossref]

Zu, P.

T. Li, X. Y. Dong, C. C. Chan, C. L. Zhao, and P. Zu, “Humidity sensor based on multimode-fiber taper coated with polyvinyl alcohol interacting with a fibe Bragg grating,” IEEE Sens. J. 12(6), 2205–2208 (2012).
[Crossref]

Appl. Opt. (3)

IEEE Photonics Technol. Lett. (1)

G. Woyessa, A. Fasano, C. Markos, H. K. Rasmussen, and O. Bang, “Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing,” IEEE Photonics Technol. Lett. 29(7), 575–578 (2017).
[Crossref]

IEEE Sens. J. (5)

T. Li, X. Y. Dong, C. C. Chan, C. L. Zhao, and P. Zu, “Humidity sensor based on multimode-fiber taper coated with polyvinyl alcohol interacting with a fibe Bragg grating,” IEEE Sens. J. 12(6), 2205–2208 (2012).
[Crossref]

R. Xiong, H. Y. Meng, Q. Q. Yao, B. Huang, Y. M. Liu, H. C. Xue, C. H. Tan, and X. G. Huang, “Simultaneous Measurement of Refractive Index and Temperature Based on Modal Interference,” IEEE Sens. J. 14(8), 2524–2528 (2014).
[Crossref]

X. D. Zhang, C. Y. Liu, J. P. Liu, and J. R. Yang, “Single Modal Interference-Based Fiber-Optic Sensor for Simultaneous Measurement of Curvature and Strain With Dual-Differential Temperature Compensation,” IEEE Sens. J. 18(20), 8375–8380 (2018).
[Crossref]

C. Bian, Y. F. Cheng, W. H. Zhu, R. X. Tong, M. L. Hu, and T. T. Gang, “A Novel Optical Fiber Mach-Zehnder Interferometer Based on the Calcium Alginate Hydrogel Film for Humidity Sensing,” IEEE Sens. J. 20(11), 5759–5765 (2020).
[Crossref]

H. W. Fu, Y. H. Jiang, J. J. Ding, and Z. L. Zhang, “Low Temperature Cross-Sensitivity Humidity Sensor Based on a U-Shaped Microfiber Interferometer,” IEEE Sens. J. 17(3), 644–649 (2017).
[Crossref]

IEEE Sens. Lett. (1)

S. Liu, H. Y . Meng, S. Y . Deng, Z. C. Wei, F. Q. Wang, and C. H. Tan, “Fiber humidity sensor based on a graphene-coated core-offset Mach-Zehnder interferometer,” IEEE Sens. Lett. 2(3), 1–4 (2018).
[Crossref]

IEEE Trans. Instrum. Meas. (1)

N. Chen, X. Zhou, and X. G. Li, “Highly Sensitive Humidity Sensor With Low-Temperature Cross-Sensitivity Based on a Polyvinyl Alcohol Coating Tapered Fiber,” IEEE Trans. Instrum. Meas. 70, 9503308 (2021).
[Crossref]

J. Lightwave Technol. (2)

J. Phys. D: Appl. Phys. (1)

G. J. Huang, Y. J. Li, C. Chen, Z. Z. Yue, W. Zhai, M. D. Li, and B. Yang, “Hydrogen Sulfide Gas Sensor Based on Titanium Dioxide/Amino-Functionalized Graphene Quantum Dots Coated Photonic Crystal Fiber,” J. Phys. D: Appl. Phys. 53(32), 325102 (2020).
[Crossref]

Measurement (2)

L. Alwis, T. Sun, and K. T. V. Grattan, “Optical fibre-based sensor technology for humidity and moisture measurement: review of recent progress,” Measurement 46(10), 4052–4074 (2013).
[Crossref]

R. J. Tong, Y. Zhao, H. K. Zheng, and F. Xia, “Simultaneous measurement of temperature and relative humidity by compact Mach-Zehnder interferometer and Fabry-Perot interferometer,” Measurement 155, 107499 (2020).
[Crossref]

Opt. Commun. (2)

D. Su, X. G. Qiao, Q. Z. Rong, H. Sun, J. Zhang, Z. Y . Bai, Y . Y . Du, D. Y . Feng, Y . P. Wang, M. L. Hu, and Z. Y. Feng, “A fiber Fabry-Perot interferometer based on a PVA coating for humidity measurement,” Opt. Commun. 311, 107–110 (2013).
[Crossref]

Y. Q. Wang, C. Y. Shen, W. M. Lou, and F. Y. Shentu, “Fiber optic humidity sensor based on the graphene oxide/PVA composite film,” Opt. Commun. 372, 229–234 (2016).
[Crossref]

Opt. Express (4)

Opt. Fiber Technol. (3)

J. T. Zhang, Z. R. Tong, W. H. Zhang, Y. M. Zhao, and J. X. Li, “Research on simultaneous temperature and relative humidity measurement based on tapered PCF Mach-Zehnder interferometer,” Opt. Fiber Technol. 61, 102408 (2021).
[Crossref]

J. Wang, “Numerical simulation and optimal design of photonic crystal fiber hygrometer coated with PVA/GO composite film,” Opt. Fiber Technol. 63, 102491 (2021).
[Crossref]

R. J. Tong, Y. Zhao, M. Q. Chen, and Y. Peng, “Multimode interferometer based on no-core fiber with GQDs-PVA composite coating for relative humidity sensing,” Opt. Fiber Technol. 48, 242–247 (2019).
[Crossref]

Opt. Laser Technol. (1)

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Data Availability

Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.

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Figures (18)

Fig. 1.
Fig. 1. (a) Sensing structure sketch. (b) Simulated result of the mode field distribution.
Fig. 2.
Fig. 2. The mechanism of PVA adsorbing water molecules
Fig. 3.
Fig. 3. (a) Before performing splicing. (b) After performing splicing. (c) SEM image of the core-offset.
Fig. 4.
Fig. 4. (a) Transmission spectra of different structures. (b) FFT of different structures
Fig. 5.
Fig. 5. Comparison chart of DCF transmission spectra of different lengths.
Fig. 6.
Fig. 6. Schematic diagram of optical fiber cladding corrosion process
Fig. 7.
Fig. 7. (a) Transmission spectrum before and after corrosion. (b) FFT before and after corrosion
Fig. 8.
Fig. 8. (a) SEM image of the DCF after corrosion. (b) SEM image of GO coating morphology. (c) SEM image of the DCF after PVA coating. (d) SEM image of PVA coating morphology.
Fig. 9.
Fig. 9. Spectral comparison chart before and after coating.
Fig. 10.
Fig. 10. The dual parameter measurement system for RH and temperature
Fig. 11.
Fig. 11. (a) RH measurement results of MZI 1. (b) The linear fitting graph of RH and the wavelengths of the resonant dip A, dip B, dip C.
Fig. 12.
Fig. 12. (a) Temperature measurement results of MZI 1. (b) The linear fitting graph of temperature and the wavelengths of the resonant dip A, dip B, dip C.
Fig. 13.
Fig. 13. (a) The RH stability of the MZI 1. (b) The temperature stability of the MZI 1.
Fig. 14.
Fig. 14. (a) RH measurement results of 0.05 g/mL PVA. (b) The linear fitting graph of temperature and the wavelengths of the resonant dip A dip B.
Fig. 15.
Fig. 15. (a) RH measurement results of 0.04 g/mL PVA. (b) RH measurement results of 0.06 g/mL PVA.
Fig. 16.
Fig. 16. (a) Temperature measurement result of MZI 2. (b) The linear fitting graph of temperature and the wavelengths of the resonant dip A, dip B.
Fig. 17.
Fig. 17. (a) The RH stability of the MZI 2. (b)The temperature stability of the MZI 2.
Fig. 18.
Fig. 18. (a) RH repeatability test. (b) Temperature repeatability test.

Tables (2)

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Table 1. the simulated value of Δmeff corresponding to different high-order cladding modes

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Table 2. Comparison of optical fiber RH and temperature sensor performance.

Equations (14)

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I = I c o + I c l + 2 I c o I c l cos φ ,
φ = 2 π ( n c o n c l ) λ = 2 π Δ n e f f λ L ,
λ d i p = 2 2 k + 1 Δ n e f f L ( k = 1 , 2 , 3 . ) .
FSR λ 2 Δ n e f f L .
y = 0.0018 x + 1.332 ,
Δ λ λ  =  ( ξ c o ξ c l n c o n c l + α x ) + Δ T ,
Δ λ d i p 1 = A Δ R H + B Δ T ,
Δ λ d i p 2 = C Δ R H + D Δ T ,
( Δ λ d i p 1 Δ λ d i p 2 ) = ( A B C D ) ( Δ R H Δ T ) ,
( Δ R H Δ T ) = 1 | M | ( D B C A ) ( Δ λ d i p 1 Δ λ d i p 2 ) ,
| M | = D A B C .
Δ m e f f = Δ n e f f λ 0 λ Δ n e f f ,
ξ = 1 λ 0 2 Δ m e f f L ,
( Δ R H Δ T ) = ( 104.054 103.3784 167.5676 172.973 ) ( Δ λ d i p A Δ λ d i p B ) ,

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