Optical frequency division multiplexing phase-sensitive optical time domain reflectometer

Abstract

The invention discloses an optical frequency division multiplexing phase-sensitive optical time domain reflectometer which comprises a narrow line width laser, an optical fiber coupler, a phase modulator, a scrambler, an erbium-doped optical fiber amplifier, an acoustic optical modulator, an optical fiber circulator, a signal generator module, a trigger source, a double balance detector, a low pass filter, a data acquisition card, a computer and a long-distance sensing optical fiber. According to the optical frequency division multiplexing phase-sensitive optical time domain reflectometer, the fundamental contradictions between the measuring distance and sampling rate in a distributed sensing system can be solved, and remoter or higher-frequency vibration is detected; and moreover, due to amplitude and phase information, the characteristics of a vibration source are judged at the first time, and the early warning can be provided immediately.

Description

technical field [0001] The invention relates to an optical time domain reflectometer, in particular to an optical frequency division multiplexing phase-sensitive optical time domain reflectometer. Background technique [0002] Phase sensitive optical time domain reflectometry (Phase-OTDR) is a new type of distributed optical fiber sensor based on Rayleigh scattering, which can remotely monitor the external dynamic physical quantities along the optical fiber line. real-time monitoring. Different from conventional optical time domain reflectometry (OTDR for short), Phase-OTDR uses a laser with a narrow linewidth (about KHz) and a very small frequency drift as a light source, by detecting Various characteristic physical quantities (amplitude, frequency, phase, etc.) at the disturbance position are obtained by the interference signal of the Rayleigh backscattered light, and the event is located by the echo time. Therefore, in addition to many characteristics of conventional di...

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Problems solved by technology

However, it is only limited to qualitative measurement of the amplitude and frequency information of the disturbance signal, and has not quantitatively obtained the phase information of the optical fiber link and the disturbance position.

On the other hand, due to the restriction of the sampling rate, the highest detectable disturbance frequency is less than 1KHz, and the spatial resolution is about 5m, and the disturbance information of higher frequency cannot be measured

This greatly limits the scope of application of this new type of sensing technology, such as ultrasonic monitoring with a disturbance frequency above MHz, which cannot reflect the advancement and superiority of this technology to a certain extent.

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