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US 10,677,616 B2Granted
Distributed dynamic strain fiber optics measurement by Brillouin optical time-domain reflectometry
AssigneeThe Regents of the University of California
InventorsKenichi Soga, Bo Li, Jize Yan, Linqing Luo, Yifei Yu
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Abstract
A system and method for distributed dynamic strain measurement using optical fiber that is based on Brillouin optical time-domain reflectometry (BOTDR) with stimulated Brillouin scattering (SBS). A short-time Fourier transform (STFT) is used to rebuild the Brillouin frequency shift (BFS) of the SBS scattered signal to perform the dynamic strain measurement.
Claims26
A method for performing Brillouin optical time-domain reflectometry for distributed dynamic strain measurements of a structure, the method comprising:
- splitting a continuous-wave laser output into a first and second branch;
- modulating the first signal branch using electro optic modulation controlled by received pulses into a stimulated Brillouin scattered (SBS) signal;
- wherein the continuous-wave laser output from said second branch comprises a continuous wave reference signal;
- applying the stimulated Brillouin scattered (SBS) signal to an optical fiber attached or embedded in a structure;
- simultaneously detecting the SBS signal from the structure and coupling this with the continuous-wave reference signal to a photodetector to produce an output signal;
- processing the output signal using Brillouin optical time-domain reflectometry (BOTDR) comprising a small gain SBS based short-time Fourier transform (STFT) configured to provide a desired spatial sampling resolution along said optical fiber;
- and
- measuring a distribution of the Brillouin frequency shifts (BFS) along the structure to calculate one or more of an applied strain or temperature change on the structure.
5 more elements
A Brillouin optical time-domain reflectometry (BOTDR) based distributed dynamic strain sensor, comprising:
- (a) a continuous-wave light source configured for outputting an optical signal to a first and second branch, and a signal generator coupled to an electro optic modulator (EOM) configured for modulating the optical signal in said first branch into a stimulated Brillouin scattered (SBS) signal, and wherein the optical signal in said second branch comprises a continuous wave reference signal;
- (b) applying the stimulated Brillouin scattered (SBS) signal to an optical fiber attached or embedded in a structure;
- (c) a detector configured for simultaneously detecting the SBS signal from the structure and coupling this with the continuous-wave reference signal to a photodetector to produce an output signal;
- (d) a processor for processing the output signal;
- and
- (e) a non-transitory memory storing instructions executable by the processor;
- (f) wherein said instructions, when executed by the processor, perform steps comprising:
- (i) measuring a distribution of the Brillouin frequency shifts (BFS) along the structure by using Brillouin optical time-domain reflectometry (BOTDR) comprising a small gain SBS based short-time Fourier transform (STFT) configured to provide a desired spatial sampling resolution along said optical fiber;
- (ii) calculating one or more of an applied strain or temperature change on the structure from the measured BFS distribution.
6 more elements
An apparatus for performing Brillouin optical time-domain reflectometry for distributed dynamic strain measurements of a structure, the apparatus comprising:
- (a) a continuous-wave light source configured for outputting an optical signal to a first branch and to a second branch, wherein the optical signals in said second branch comprises a continuous-wave reference signal;
- (b) a signal generator and modulator configured for manipulating the optical signal in said first branch into a stimulated small-gain Brillouin scattered (SBS) signal directed into an optical fiber attached or embedded in a structure;
- (c) a detector configured for simultaneously detecting the SBS signal from the structure and the continuous-wave reference signal to produce an electrical output signal;
- (d) a processor for processing the electrical output signal;
- and
- (e) a non-transitory memory storing instructions executable by the processor;
- (f) wherein said instructions, when executed by the processor, perform steps comprising:
- (i) measuring a distribution of the Brillouin frequency shifts (BFS) along the structure by using Brillouin optical time-domain reflectometry (BOTDR) comprising a small gain SBS based short-time Fourier transform (STFT) configured to provide a desired spatial sampling resolution along said optical fiber;
- (ii) calculating one or more of an applied strain or temperature change on the structure from the measured BFS distribution, by rebuilding of the Brillouin frequency shift (BFS) with short-time Fourier transform (STFT).
6 more elements
Dependencies are inferred from the claim text.