Effect of laser temperature control on Brillouin optical correlation-domain reflectometry

Abstract

We show that 1-°C drift of laser temperature yields a strain error of ~8 με in Brillouin optical correlation-domain reflectometry. Under the assumption that the strain measurement accuracy is +/-20 με (severe requirement), +/-2.5-°C drift of the laser temperature can be permitted for proper system operation. We prove this prediction by performing distributed strain measurements at different laser temperatures. Our results indicate that, if we allow a strain measurement accuracy of approximately +/-100 με (or more), we can even remove the thermal control of the laser, leading to cost reduction and downsizing of the system. Distributed strain and temperature sensors are key tools for monitoring the conditions of various civil infrastructures. In particular, distributed sensing techniques based on Brillouin scattering in optical fibers have been the focus of attention because of their ability to detect sub-centimeter strained or heated sections along long optical fibers. 1) Based on the configurations of light injection to sensing fibers, Brillouin sensors can be divided into twoend-access "analysis" and one-end-access "reflectometry". The former includes Brillouin optical time-, frequency-, and correlation-domain analysis (BOTDA, 2-5) BOFDA, [6][7][8] and BOCDA), [9][10][11][12][13] whereas the latter includes Brillouin optical time-, frequency-, and correlationdomain reflectometry (BOTDR, [14][15][16] BOFDR,17) and BOCDR). [18][19][20][21][22][23][24][25] In general, analysis systems exhibit higher signal-to-noise ratios (SNRs) due to the use of stimulated Brillouin scattering. However, despite their lower SNRs, reflectometers based on spontaneous Brillouin scattering have higher degrees of freedom in embedding the sensing fibers into structures; in addition, measurements can be continued even when the sensing fibers are broken. Needless to say, each reflectometry has its own merits and demerits, and here, we focus on BOCDR.

Spatial Resolution Enhancement of Brillouin Optical Correlation-Domain Reflectometry Using Convolutional Neural Network: Proof of Concept

“…This study focuses on Brillouin optical correlationdomain reflectometry (BOCDR) [7], which operates on the basis of correlation control of continuous light waves in a self-heterodyne scheme. BOCDR offers operation by single-FUT-end light injection, high spatial resolution [9,10], high sampling rate [11,12], random accessibility [7], cost efficiency [13,14], and some others [15,16].…”

Recent progress in slope-assisted Brillouin optical correlation-domain reflectometry

“…By scanning the correlation peak along the FUT and observing the BGS at every point, distributed measurement of Brillouin frequency shift (BFS), which gives the information of strain and temperature, can be performed. To date, we have drastically improved the performance of BOCDR, including enhancement of spatial resolution [44][45][46], extension of measurement range [47][48][49], improvement of measurement stability [50][51][52][53], widening of the strain dynamic range [54], simplification of the system setup [55][56][57], reduction of implementation cost [58,59], and use of polymer optical fibers (POFs) [52,53,57,60]. The operation speed is also the target of performance improvement.…”

Total spectral power-based method for estimating Brillouin frequency shift in optical fibers

“…[1][2][3] Typical configurations include Brillouin optical time-domain reflectometry/analysis (BOTDR/BOTDA), [4][5][6][7][8][9][10] Brillouin optical frequency-domain reflectometry/analysis (BOFDR/BOFDA), [11][12][13][14] and Brillouin optical correlationdomain reflectometry/analysis (BOCDR/BOCDA). [15][16][17][18][19][20][21][22][23] These configurations have their own merits and demerits, and here we focus on BOCDR, 20,21) which is known as a unique technique with operation by single-fiber-end light injection, high spatial resolution of up to millimeter order, and random accessibility to measuring positions.…”