Abstract

A coiled fiber-optic chemical sensor has proven to be effective for the remote detection of volatile organic compounds, such as trichloroethylene (TCE), 1,1-dichloroethylene (DCE), and gasoline, in aqueous solutions. The analyte diffuses into the hydrophobic cladding and evanescent wave absorption spectra are measured in the near-infrared (1600-1850 nm) without the presence of the water absorption bands. In order for fiber-optic chemical sensors to operate effectively in remote environments, the influence of temperature on the sensor response must be known. The C-H bonds of the polysiloxane cladding material also have absorption bands in the near-infrared (NIR). Changes in temperature will change the density (i.e., concentration of C-H bonds) and refractive index of the cladding. Due to these effects, a temperature change of only 3°C from the reference has been shown to significantly alter the background absorbance. The temperature-dependent background absorption is found to be linear with the slope, and the values are proportional to the absorption coefficient of the cladding material. The intercept of the absorbance vs. temperature plot is found to follow the first derivative of the fiber sensor transmission spectrum. Evanescent wave absorption spectra of TCE solutions have been corrected for temperature.

Cladless optical fiber sensor based on evanescent wave absorption for monitoring methylene blue induced water pollution

Kenza Azil, Kouider Ferria, and Said Bouzid
J. Opt. Soc. Am. B 37(11) A253-A258 (2020)

Fiber-optic evanescent wave sensor with a segmented structure

Jun Lou, Hong-zhi Xu, Ben Xu, Jie Huang, Ben-chong Li, and Wei-min Shen
Appl. Opt. 53(19) 4200-4205 (2014)

Determination of bacterial activity by use of an evanescent-wave fiber-optic sensor

M. Shelly John, Anil Kishen, Lim Chu Sing, and Anand Asundi
Appl. Opt. 41(34) 7334-7338 (2002)

Effects of surface roughness on optical properties and sensitivity of fiber-optic evanescent wave sensors

Nianbing Zhong, Xun Zhu, Qiang Liao, Yongzhong Wang, Rong Chen, and Yahui Sun
Appl. Opt. 52(17) 3937-3945 (2013)

Fiber-optic evanescent wave sensor for gas detection

A. Messica, A. Greenstein, A. Katzir, U. Schiessl, and M. Tacke
Opt. Lett. 19(15) 1167-1169 (1994)