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

[1] H. Ohno, H. Naruse, M. Kihara and A. Shimada, Industrial application of the BOTDR optical fiber strain sensor, Opt Fiber Technol 7 (2001), pp. 45–64.

[2] H. Murayama, K. Kageyama, H. Naruse and A. Shimada, Distributed strain sensing from damaged composite materials based on shape variation of the Brillouin spectrum, J Intel Mater Syst Struct 15 (2004), pp. 17–25.

[3] Vorster TEB, Soga K, Mair RJ, Bennett PJ, Klar A, Choy CK. The use of fibre optic sensors to monitor pipeline response to tunneling, In: Proc GeoCongress: Geotechnical Engineering in the Information Technology Age, Atlanta, USA: 2006.

[4] H. Naruse and M. Tateda, Trade-off between the spatial and the frequency resolutions in measuring the power spectrum of the Brillouin backscattered light in an optical fiber, Appl Opt 38 (1999), pp. 6516–6521.

[5] H. Naruse and M. Tateda, Launched pulse-shape dependence of the power spectrum of the spontaneous Brillouin backscattered light in an optical fiber, Appl Opt 39 (2000), pp. 6376–6384.

[6] F. Ravet, X. Bao, Y. Li, Q. Yu, A. Yale, V.P. Kalosha and L. Chen, Signal processing technique for distributed Brillouin sensing at centimetre spatial resolution, J Lightwave Technol 25 (2007), pp. 3610–3618.

[7] R. Bernini, A. Minardo and L. Zeni, Reconstruction technique for stimulated Brillouin scattering distributed fiber-optic sensors, Opt Eng 41 (2002), pp. 2186–2194.

[8] H. Naruse, M. Tateda, H. Ohno and A. Shimada, Dependence of the Brillouin gain spectrum on linear strain distribution for optical time-domain reflectometer-type strain sensors, Appl Opt 34 (2002), pp. 7212–7217.

[9] H. Naruse, M. Tateda, H. Ohno and A. Shimada, Deformation of the Brillouin gain spectrum caused by parabolic strain distribution and resulting measurement error in BOTDR strain measurement system, IEICE Trans Electron 10 (2003), pp. 2111–2121.

[10] A. Brown, M. DeMerchant, X.Y. Bao and T. Bremner, Spatial resolution enhancement of a Brillouin-distributed sensor using a novel signal processing method, J Lightwave Technol 7 (1999), pp. 1179–1183.

[11] M. Ohsaki, M. Tateda, T. Omatsu and H. Ohno, Spatial resolution enhancement of distributed strain measurement using BOTDR by partially cluing optical fiber, IEICE Trans Commun 8 (2002), pp. 1636–1639.

[12] N. Nitta, M. Tateda and T. Omatsu, Spatial resolution enhancement in BOTDR by spectrum separation method, Opt Rev 2 (2002), pp. 49–53.

[13] F. Ravet, X. Bao, Q. Yu and L. Chen, Criterion for sub-pulse-length resolution and minimum frequency shift in distributed Brillouin sensors, IEEE Photonics Technol Lett 7 (2005), pp. 1504–1506. 

[14] D. Zhang, B. Shi, H.L. Cui and H.Z. Xu, Improvement of spatial resolution of Brillouin optical time domain reflectometer using spectral decomposition, Opt Appl 2 (2004), pp. 291–301.

[15] Thévenaz L, Mafang SF. Distributed fiber sensing using Brillouin echoes, In: Proc SPIE 2008; 7004:70043N.

[16] Mizuno Y, He Z, Hotate K. Brillouin optical correlation-domain reflectometry with 13-mm spatial resolution and 50-Hz sampling rate, In: Conf Quantum Electron Laser Sci Conf Lasers Electro-Opt. CLEO/QELS(2008)1–2.

[17] T. Horiguchi, K. Shimizu, T. Kurashima, M. Tateda and Y. Koyamada, Development of a distributed sensing technique using brillouin scattering, J Lightwave Technol 7 (1995), pp. 1296–1302.

[18] Murayama H, Kageyama K, Shimada A, Nishiyama A. Improvement of spatial resolution for strain measurements by analyzing Brillouin gain spectrum, In: Proc. SPIE 5855, 2005. p. 551–4.