Optical time domain reflectometer based on double acoustic-optical modulators and common-mode rejection method of optical time domain reflectometer

Abstract

The invention discloses an optical time domain reflectometer based on double acoustic-optical modulators and a common-mode rejection method of the optical time domain reflectometer. The method includes the following steps that a laser device outputs an optical signal; the optical signal is divided into two routes of optical signal bodies, and the optical signal bodies are modulated; direct frequency beating is conducted on the two routes of optical signal bodies so that frequency noise of the laser device can be eliminated and a reference signal can be generated; the first route of optical signal bodies enter a sensing optical fiber after being amplified, and a measurement signal is obtained after frequency beating is conducted on the back scattered light of the sensing optical fiber and the second route of optical signal bodies; the measurement signal and the reference signal are collected, phase demodulating is conducted, and phase comparison is conducted on the reference signal and the measurement signal to obtain a signal to be measured. The two acoustic-optical modulators are adopted, and by means of the method of conducting common-mode rejection by introducing the reference signal, influences of frequency noise of the laser device in the phase sensitive optical time domain reflectometer and frequency noise of the acoustic-optical modulators on the measurement result are reduced.

Description

technical field [0001] The invention relates to an optical time domain reflectometer, in particular to an optical time domain reflectometer based on a dual acousto-optic modulator and a common-mode suppression method thereof. Background technique [0002] Phase-sensitive optical time domain reflectometer (hereinafter referred to as Phase-OTDR) is a distributed optical fiber sensor based on Rayleigh scattering, which can remotely monitor the external dynamic physical quantities along the sensing optical fiber. Phase-OTDR needs to use a laser with a narrow linewidth (less than 10KHz) and a very small frequency drift as a light source, and obtains the environmental parameters at the disturbance position by detecting the change of the interference signal of the Rayleigh scattered light in the optical fiber in the region of the optical pulse width information (temperature, pressure, vibration, sound, etc.) and locate events by measuring the return time of light pulses. In additi...

AI Technical Summary

Problems solved by technology

The patented technical solution uses a phase modulator to generate multiple frequency components for multiplexing measurement, and uses an acousto-optic modulator for frequency shifting and optical pulse generation. For data acquisition and signal post-processing sampling rate and data parallel processing hardware performance indicators The requirements are high, and the sampling rate of the acquisition card needs to be as high as 500MHz or more, which puts forward very strict requirements on the design of the hardware circuit, which is not conducive to the noise suppression of the phase measurement system

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