Distributed optical fiber vibration sensors based on unbalanced Michelson interferometer and PGC demodulation
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RESEARCH ARTICLE
Distributed optical fiber vibration sensors based on unbalanced Michelson interferometer and PGC demodulation Zhihua Yu1,2 • Abdi Karim A. Dahir1,2 • Haolong Dai1,2 • Yuansheng Luo1,2 Guang Qi1,2 • Zhihua Li1,2
•
Received: 19 July 2019 / Accepted: 13 July 2020 Ó The Optical Society of India 2020
Abstract In this paper, we propose a distributed optical fiber vibration sensing system based on U-OTDR and Michelson interferometer. It can detect multiple vibrations simultaneously along a sensing fiber, and the vibration waveform, frequency, position and amplitude could be demodulated correctly using our proposed PGC demodulation algorithm. The experimental results show, a SNR of 34.86 dB is achieved with the background noise level of - 37 dB at the 1000 m, and the SNR is 28.09 dB with the background noise level of - 32 dB at the 6000 m. Keywords Distributed optic fiber sensors Phase sensitivity optical time domain reflectometer (U-OTDR) Phase generated carrier (PGC) Demodulation algorithm
Introduction Distributed optical fiber sensing is a technology using optical fiber as the sensing medium and carries on remote and real-time monitoring of the target along the sensing fiber. It is widely used in long-range safety monitoring (i.e., pipeline monitoring of natural gas and oil) or health monitoring of civil structures (i.e., bridge and high building) [1–4]. Up to now, distributed optical fiber vibration sensing based on interferometry and backscattering technology (Rayleigh or Brillouin scattering) has been deeply & Zhihua Yu [email protected] 1
School of Automation, China University of Geosciences, Wuhan, Hubei, China
2
Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems, Wuhan, Hubei, China
researched by worldwide scholars [5–8]. The frequency response of interferometries is very high, but the signal demodulation method needs to be further simplified and the spatial resolution should be improved, and more importantly, distributed vibration sensing systems based on interferometries have poor capability of multiple vibration points location and detection simultaneously [9]. On the other hand, the frequency response of vibration sensing based on Brillouin scattering is relatively low [10]. Rayleigh scattering-based OTDR technology owns the following merits: high spatial resolution, multipoint detection and simple signal processing [11, 12]. However, due to the weak intensity of Rayleigh backscattering light, the averaging method is adopted in signal processing which results in the frequency response sharply decreasing. Therefore, we propose a composite sensing scheme combining the interferometry and Rayleigh backscattering technology to achieve distributed vibration measurement with high spatial resolution and high frequency response simultaneously.
Principle The principle of self-interference of Rayleigh backscattering The basic principle of phase sensitivity optical time domain reflectometer (U-OTDR) is the measurement of the phase shift induced by the
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