Expand this Topic clickable element to expand a topic
Skip to content
Optica Publishing Group
Journal Home About Issues in Progress Current Issue All Issues Feature Issues

Fiber Bragg-grating strain sensor interrogation using laser radio-frequency modulation

G. Gagliardi, M. Salza, P. Ferraro, and P. De Natale

Open Access Open Access

Abstract

We demonstrate the possibility of using radio-frequency modulation spectroscopic techniques for interrogation of fiber Bragg-grating (FBG) structures. Sidebands at 2 GHz are superimposed onto the output spectrum of a 1560-nm DFB diode laser. The power reflected by an FBG is demodulated at multiples of the sideband frequency. The sideband-to-carrier beat signal is shown to be extremely sensitive to Bragg wavelength shifts due to mechanical stress. Using this method, both static and dynamic strain measurements can be performed, with a noise-equivalent sensitivity of the order of 150 nε/√Hz, in the quasi-static domain (2 Hz), and 1.6 nε/√Hz at higher frequencies (1 kHz). The measured frequency response is presently limited at 20 kHz only by the test device bandwidth. A long-term reproducibility in strain measurements within 100 nε is estimated from laser frequency drift referred to molecular absorption lines.

©2005 Optical Society of America

Full Article  |  PDF Article
More Like This
DFB fiber laser static strain sensor based on beat frequency interrogation with a reference fiber laser locked to a FBG resonator

Wenzhu Huang, Shengwen Feng, Wentao Zhang, and Fang Li
Opt. Express 24(11) 12321-12329 (2016)

Interrogation of fiber Bragg-grating resonators by polarization-spectroscopy laser-frequency locking

G. Gagliardi, S. De Nicola, P. Ferraro, and P. De Natale
Opt. Express 15(7) 3715-3728 (2007)

Highly sensitive dynamic strain measurements by locking lasers to fiber Bragg gratings

B. Lissak, A. Arie, and M. Tur
Opt. Lett. 23(24) 1930-1932 (1998)

View More...

Cited By

Optica participates in Crossref's Cited-By Linking service. Citing articles from Optica Publishing Group journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (7)
Fig. 1.
Fig. 1. Sketch of the experimental setup. F-P stands for Fabry-Pèrot, BS for beam-splitter, OI for optical isolator, BT for bias-tee, DBM for double-balanced mixer and PD for photodiode.

Download Full Size | PDF

Fig. 2.
Fig. 2. Example of the signal obtained by high-frequency mixer demodulation upon FBG reflection (maximum at 1560.778 nm). The lower trace corresponds to the transmission of a 1-GHz free-spectral-range Fabry-Pérot interferometer, where RF sidebands at 2.2 GHz are visible.

Download Full Size | PDF

Fig. 3.
Fig. 3. Response of the LRFM system to static deformations directly applied to the 50-% FBG by the PZT. The dashed line corresponds to a weighted linear fit. Vertical bars are standard errors of mean FBG shifts deriving from 10 measured values.

Download Full Size | PDF

Fig. 4.
Fig. 4. FFT amplitude spectrum of the sensor output measured by a spectrum analyzer (resolution bandwidth of 50 mHz). The high peak corresponds to excitation of the PZT by a sine wave at 2 Hz with a strain-equivalent amplitude of 3 µε. The red line represents the background when the PZT is off.

Download Full Size | PDF

Fig. 5.
Fig. 5. Spectrum given by a 3-µε deformation applied to the FBG at higher acoustic frequencies (1 kHz). In this case, the resolution bandwidth is 50 Hz.

Download Full Size | PDF

Fig. 6.
Fig. 6. LRFM-system time response to excitation of an acoustic wave at 1100 Hz with 20-µε peak-to-peak amplitude (80-% FBG), compared to the output of an electrical strain gauge with 1-µε sensitivity (upper trace).

Download Full Size | PDF

Fig. 7.
Fig. 7. Static strain values measured by the laser sensor are plotted vs. the electrical probe values. A weighted linear fit is also represented. The error bars represent the maximum uncertainty due to the electrical gauge reading.

Download Full Size | PDF

Select as filters
Select Topics Cancel
Top
       
© Copyright 2024 | Optica Publishing Group. All rights reserved, including rights for text and data mining and training of artificial technologies or similar technologies.
Privacy | Terms of Use