Enhanced performance in coherent BOTDA sensor with reduced effect of chromatic dispersion

Significance Statement

Brillouin optical time-domain analysis (BOTDA) sensors can realize temperature and strain sensing along many tens of kilometers with spatial resolutions in the meter or even centimeter scale, which promotes their applications in structural health monitoring, geotechnical engineering and leakage detection along pipelines, etc. The key of this technique is that the frequency corresponding to peak power of the Brillouin gain spectrum (BGS) is linearly related to the temperature and strain applied to the sensing fiber. Because the Brillouin gain or loss signal that used for BGS reconstruction is usually very weak, thus, one of the most important research topics for BOTDA sensors is to improve the signal-to-noise ratio (SNR). Several advanced techniques have been proposed to realize this goal, such as distributed Raman amplification, optical pulse coding, and different signal processing.

Recently, coherent detection method is employed in BOTDA sensors, resulting in several-dB or even more than 10-dB SNR improvement. Our group (led by Prof. Lianshan Yan at the Southwest Jiaotong University, China) is interested in this method, and plenty works for optimizing coherent-detection BOTDA sensors have been carried out, such as reducing the noise caused by multiple sidebands, reducing the effect of phase jitter caused by optical fiber link transmission (Opt. Express, 23(23), 23(12), 2015; 24(5), 2016). We theoretically analyze and experimentally demonstrate the effect of chromatic dispersion (CD) on coherent-detection BOTDA sensors that based on double-sideband (DSB) phase modulated probe (PMP). In which, BGS can’t be extracted correctly through the difference value between the total PM-IM conversion and CD induced PM-IM conversion, where total PM-IM conversion is contributed by both Brillouin gain and CD. However, BGS can be fully recovered by this difference value by using DSB intensity modulated probe (IMP), meanwhile system stability is enhanced, i.e., measured BGS under different probe powers and extinction ratios are almost the same. Besides, sensor performance can be further improved by using single-sideband (SSB) IMP instead of DSB-IMP, which is independent of the sensing fiber length and modulation frequencies as demonstrated by our newest published paper (PJ, vol. 8 (1), 6800908 (2016)). Until now, a spatial resolution of 2m along 40-km sensing fiber with a temperature resolution of 0.97°C has been realized by our group.

Enhanced performance in coherent BOTDA sensor with reduced effect of chromatic dispersion.Advances in Engineering

About the author

Zonglei Li received the degree of electrical & information engineering from the southwest jiaotong university (SWJTU), China, in 2011. He is currently working towards the Ph.D. degree in SWJTU and his research topics include microwave photonics and Brillouin distributed fiber sensors. 

 

About the author

Lianshan Yan received B.E. and Ph.D. degree from Zhejiang University and the University of Southern California (USC, Los Angeles), respectively. He is currently a full professor and the director of Center for Information Photonics & Communications (CIPC) at Southwest Jiaotong University, Chengdu, Sichuan, China. His research interests include high-speed optical fiber communications, optical signal processing, nano-photonics, microwave photonic, fiber sensors, etc.

He has worked on solid state laser in North China Research Institute of Optoelectronics from 1994 to 1999, and has been with General Photonics Corp. (Chino, California) as the Chief Scientist and manager of Engineering from 2005 to 2007.

Prof. Yan is the author and co-author of more than 380 papers published in prestigious journals and conference proceedings, including seven invited journal papers and more than thirty invited talks. He also authored two book chapters. He holds thirteen issued U.S. patents and more than thirty China patents.

Prof. Yan is a senior member of the IEEE and a member of OSA. He is the Chair of Optical Fiber Technology Technical Group of Optical Society of America (OSA). He received the IEEE Photonics Society Distinguished Lecturer Award in 2011 (2011-2013). He is one of the recipients of IEEE LEOS Graduate Fellowship in 2002, and the co-chair or TPC member of more than thirty international conferences, including OFC (2013-2015), ECOC (2013-), FiO’09-12, PHO’08-11, ACP’10-12, etc. He was an associate editor of IEEE Photonics Journal (2009-2015).

Journal Reference

Opt Express. 2015 Nov 16;23(23):30483-90.

Li Z, Yan L, Shao L, Pan W, Luo B.

Center for Information Photonics & Communications, School of Information Science & Technology, Southwest JiaoTong University, Chengdu, Sichuan,610031, China

Abstract

An approach for reducing chromatic dispersion (CD) induced Brillouin gain spectrum (BGS) distortion and measurement instabilities in coherent Brillouin optical time domain analysis (BOTDA) sensing systems is proposed and experimentally demonstrated. By utilizing intensity modulated probe (IMP) instead of phase modulated probe (PMP), sensing performance is obviously improved. Reduction of ~6-MHz decoding error caused by the CD induced BGS distortion is achieved in the measurement of Brillouin frequency shift (BFS) along the whole 40-km sensing distance. Enhanced system stabilities are demonstrated by testing the BGS under different conditions.

Go To Optics Express. 

 

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