Optical fiber vibration sensing system based on dual modulation Mach-Zehnder interferometer

Abstract

The invention discloses an optical fiber vibration sensing system based on a dual modulation Mach-Zehnder interferometer. The system comprises a Mach-Zehnder interferometer, a host computer and a slave computer arranged at both ends of the interferometer, two coupler, four optical circulators, two phase modulators and two sensing optical fibers. The optical fiber vibration sensing system based on the dual modulation Mach-Zehnder interferometer loads modulating signals sent by the host computer and the slave computer at both ends of the optical fiber interferometer to the phase modulator of the interferometer to realize dual modulation, after modulated signals are coherent, signal sampling and demodulation are realized at an opposite end of a light source, the modulating signals are delayed as demodulating signals in a process of realizing demodulation, so that time delay that the modulated signals reaches a demodulating module through transmission and circuit relay is counteracted, thereby solving the disadvantage that since phase difference between the modulating and demodulating signals is too large, a demodulating result is severely distorted, and further enabling the phase difference between the modulating signals and the demodulating signals of the host computer and the slave computer ends to be greatly reduced, thereby achieving relatively high positioning precision.

Description

technical field [0001] The invention relates to optical fiber sensing technology, in particular to an optical fiber vibration sensing system based on a double-modulated Mach-Zehnder interferometer. Background technique [0002] For places with high security requirements such as pipelines, communication lines, especially military communication lines, and border lines, distributed optical fiber sensing is generally used to achieve non-blind zone protection for the entire line. At present, the optical path of more mature products for optical fiber sensing generally adopts the Sagnac ring method. Due to the use of the Sagnac ring method to achieve protection, the positioning error increases with the protection distance. Increases increase proportionally, so it is not suitable for long-distance protection. If many Sagnac (Sagnac) rings are used to form sensing units to form a sensing network to increase the sensing distance, it will increase the complexity of the entire system a...

AI Technical Summary

Problems solved by technology

The situation is completely different for the side far away from the modulation signal end and the side close to the modulation signal. When the modulation signal is loaded on the optical path, the phase of the signal arriving at the demodulation module after hundreds of kilometers of long-distance transmission, photoelectric conversion, and circuit delay is unknown. Yes, if it is directly multiplied by the demodulated signal to achieve demodulation, the phase difference between the modulated signal and the demodulated signal is random, and this random phase may be π, π / 2, or 0 to For any value in the range of 2π, if the phase difference is π, it will directly cause the vibration signal to be demodulated, thus making it impossible to locate

This defect directly limits the practical application of Mach-Zehnder interferometer

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