Optical fiber vibration sensing system and using method thereof based on double Mach-Zehnder interferometers

Abstract

The invention discloses an optical fiber vibration sensing system and a using method thereof based on double Mach-Zehnder interferometers. An end A machine and a end B machine of the system are arranged at two ends of the interferometer, a control module of each end machine is connected with a light source as well as a detecting collection and communication module, the end A machine is further provided with a time synchronization module. A communication fiber is connected with the communication modules of the end A machine and the end B machine. The light source module of the end A machine and the end B machine is connected with the detecting collection module of an opposite end machine through a sensing optical fiber and an optical coupler to form double interferometers. The using method of the system comprises the following steps of: setting a threshold value by the control module of the end A machine, respectively outputting the interference information of optical signals of the end A machine and the end B machine to the opposite end machine; sending a collection triggering signal by the control module of the end A machine and starting to collect data by a second end machine when the sensing optical fiber influenced by vibrating to interfere in the information reaches the threshold value; determining the position of interfering on the sensing optical fiber by the control module of the end A machine according to two-path collecting data and the time synchronization information. The invention has double light sources, low loss of optical power, longer monitoring distance and higher sensitivity.

Description

(1) Technical field [0001] The invention relates to optical fiber sensing technology, in particular to an optical fiber vibration sensing system based on a double Mach-Zehnder interferometer and a method for using it. (2) Background technology [0002] In terms of long-distance security monitoring of pipelines, communication lines, and border lines, conventional sensing technologies such as infrared and cameras have encountered major technical bottlenecks. Due to the limited detection distance of a single sensing unit used in these methods, many sensing units need to be used to form a sensing network to increase the sensing distance, resulting in problems such as complex system structure and high construction and maintenance costs in long-distance detection. [0003] Distributed optical fiber sensing technology can continuously measure the environmental parameters (including vibration, shock, temperature, etc.) distributed along the sensing optical fiber in real time. Compa...

AI Technical Summary

Problems solved by technology

The main disadvantage of this structure is that it uses a signal return fiber that is as long as the sensing fiber, and additional optical passive devices are introduced in the optical path, which increases the optical power loss on the optical path, that is, the loss of transmission Sense of length

Secondly, all the optical signals transmitted on the interferometer are related, and the reflected light generated by any optical coupler will participate in the interference of the signal light, which will cause the degradation of the optical signal and affect the detection sensitivity and positioning accuracy of the sensor.

On the other hand, the optical signal of the light source sent from the communication optical fiber to the opposite end and the interference optical signal brought back are transmitted in the form of analog signals, which can easily cause optical signal distortion and also lead to a decrease in detection sensitivity

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