Brillouin power spectrum analysis for partially uniformly strained

Authors: Dan Zhang a, HongzhongXu b, BinShi a, HaiboSui a, GuangqingWei a
a Center for Engineering Monitoring with Opto-Electronic Sensing (CEMOES), Nanjing University, 210093 Nanjing, China
b College of Civil Engineering, Nanjing University of Technology,210009 Nanjing, China

Source: Optics and Lasers in Engineering, Volume 47, Issue 9, September 2009, Pages 976-981

 Abstract: Due to the restriction of the spatial resolution, about 1 m for current commercially available system, strain distribution measured by Brillouin optical time domain reflectometer (BOTDR) is slightly different from the actual one. In this paper, the equation of the Brillouin power spectrum for partially uniformly strained fiber within the spatial resolution is theoretically derived. Based on the derived results, investigation has been made on the shape characteristics of the superposed Brillouin power spectrum, as well as the dependence of the calculated strain of BOTDR on the actual strain of the fiber. It was found that the difference between the calculated strain and the actual strain depends mainly on the strain value of the fiber and the strained length within the spatial resolution for the given distributed sensing system.

Keywords: BOTDR; Spatial resolution; Power spectrum; Strain measurement; Superposition

Article Outline:
1. Introduction
2. Brillouin backscattered light
3. Superposition of Brillouin power spectrum
4. Analysis of the superposed Brillouin power spectrum
4.1. Brillouin spectrum when r is equal to 0.5
4.2. Brillouin power spectrum when r is less than 0.5
4.3. Brillouin power spectrum when r is larger than 0.5
4.4. Discussion
5. Conclusions
Acknowledgements
References

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