Phase-sensitive optical time domain reflection device and method based on frequency modulation

Abstract

The invention provides a phase-sensitive optical time domain reflection device and method based on frequency modulation. The method comprises the following steps: dividing laser into two paths, carrying out the synchronous modulation and output of an intensity modulator, obtaining a multi-frequency optical pulse sequence, wherein each optical pulse spectrum is composed of a fixed single frequency and a linear chirp with a non-overlapping frequency band; enabling the sequence to generate backward Rayleigh scattering signals with mutually separated frequency bands in a sensing optical fiber, and obtaining a Rayleigh scattering pattern of each multi-frequency optical pulse by using digital band-pass filters with different frequency bands; and sequentially carrying out related processing on the Rayleigh scattering patterns obtained in sequence, and finally obtaining a disturbance position and a disturbance size thereof. According to the phase-sensitive optical time domain reflection device and method based on frequency modulation provided by the invention, the problem of signal aliasing caused by the fact that a plurality of pulses are hit in a repetition period in a traditional device is solved, the detection interval time is shortened, the measurement speed is greatly improved, and the broadband large-vibration measurement capability of the system is improved.

Description

technical field [0001] The present invention relates to the technical field of optical fiber sensing, and more specifically, to a frequency modulation-based phase-sensitive optical time-domain reflection device and method. Background technique [0002] Phase Sensitive Optical Time Domain Reflectometer - OTDR is a distributed optical fiber sensing technology that enables vibration measurement. When the output light of the laser light source is modulated by the modulator into pulsed light and injected into the sensing fiber, the light is scattered to Rayleigh after being detected by the detector, and the information at the position of the corresponding fiber is obtained according to the time delay of receiving the scattered light. because - OTDR uses a narrow linewidth light source, so what the detector receives is the result of mutual interference and superposition of back Rayleigh scattered light within the pulse width. When the external disturbance acts on the optical ...

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Problems solved by technology

For example, the optical frequency division multiplexing phase-sensitive optical time domain reflectometer (CN201210124995.3) proposed by Zhou Jun and Cai Haiwen of Shanghai Jiaotong University in 2012 realized the detection of high-frequency vibrations, but it had to increase the pulse width to Avoids spectral aliasing during the measurement, which loses positioning accuracy

In addition, in 2016, the distributed optical fiber sensing system and its vibration detection and positioning method (CN201610719172.3) proposed by He Zuyuan and Liu Qingwen of Shanghai Jiaotong University used sweeping pulses in a coherent structure to achieve multi-channel frequency division multiplexing, although It overcomes the problems of low response bandwidth and positioning accuracy, but its system complexity has also increased a lot

At present, due to the phenomenon of mutual interference in a single pulse and between multiple pulses, the existing chirped pulse and direct detection type -OTDR system can not meet the condition of frequency division multiplexing

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