Composite optical fiber vibration sensing system based on phi-OTDR

A vibration sensing system and composite optical fiber technology, applied in measuring devices, instruments, measuring ultrasonic/sonic/infrasonic waves, etc., can solve the problems of insensitivity of detection distance, insufficient sensing distance, and inability to measure front-end disturbance signals. The effect of high nonlinear threshold level, high scattered light capture rate, and simple technical solution

CN112432696APending Publication Date: 2021-03-02SHANGHAI UNIV OF ENG SCI
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2021-03-02

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Abstract

The invention relates to a composite optical fiber vibration sensing system, which realizes optical fiber remote sensitivity by using a multimode optical fiber and a single-mode optical fiber as sensitive elements on the basis of taking the single-mode optical fiber as a sensing medium. According to a sensing process, high-power laser pulses are incident to the multimode optical fiber through thecirculator and then flow into the single-mode optical fiber through the mode converter, so that the sensing medium effectively prevents high-power detection pulses from directly flowing into the single-mode optical fiber to cause unstable modulation, stimulated Brillouin effect and other non-linear effects to cause insensitivity of the detection distance; in addition, insensitivity of a front endarea of the front end of the detection distance due to saturation of the photoelectric detector can be avoided, short transmission distance due to the fact that only the multimode optical fiber is used is avoided, and 30km remote sensitivity is achieved based on the composite multimode-single mode optical fiber.
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Description

technical field

[0001] The present invention relates to the technical field of distributed reflective sensing, in particular to a composite optical fiber vibration sensing system. Background technique

[0002] Compared with other sensing technologies, distributed optical fiber sensors have the advantages of long detection distance, high sensitivity and fast response speed. Therefore, it is widely used in perimeter security, oil and gas pipeline monitoring, rail transit and many other fields, and has become an ideal non-destructive testing technology for large-scale facilities.

[0003] At present, the most widely used distributed optical fiber sensing technology is mainly phase-sensitive optical time domain reflectometer, which uses the Rayleigh scattered light of the detection pulse in the optical fiber for distributed sensing. Perturbation signals are sensed by detecting the phase change of scattered light, which has been applied in distributed vibration sensing. Howev...

Examples

Embodiment

[0029] The present invention relates to a A composite optical fiber vibration sensing system, which uses the change of the Rayleigh backscattered light returned by the detection pulse through the sensing optical fiber to determine the position of the disturbance point. Such as figure 1 As shown, the system includes a narrow linewidth laser (DFB (Distributed Feedback Laser) laser) 1, an acousto-optic modulator (AOM, acousto-optic modulator) 2, two erbium-doped fiber amplifiers (EDFA, Erbium Doped Fiber Application Amplifier) ​​3 , 11, two attenuators (OA) 4, 12, two filters (OF) 5, 13, multimode fiber circulator (OC) 6, multimode fiber (MFM) 7, two mode converters (MC ) 8, 10, single-mode optical fiber (SFM) 9, balanced photodetector (PD) 14, data acquisition card (DAQ) 15 and industrial computer (IPC) 16.

[0030] A narrow linewidth laser 1, an acousto-optic modulator 2, a first erbium-doped fiber amplifier 3, a first attenuator 4, and a first filter 5 are connected in sequ...