Optical fiber vibration sensing system of single light source pulse and sensing method thereof

A technology of pulse coding and optical fiber vibration, which is used in measurement devices, instruments, and ultrasonic/sonic/infrasonic waves. It can solve the problems of high system complexity, limited dynamic range, weak return light intensity, etc. The effect of high accuracy and low noise level

Inactive Publication Date: 2015-04-29
TIANJIN UNIV
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Problems solved by technology

At the same time, because the spatial resolution is related to the pulse length, very narrow pulses are often used for spatial resolution, usually tens to hundreds of nanoseconds, so the return light intensity is weak, and the signal resolution is low after long-distance transmission , limiting the dynamic r

Method used

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  • Optical fiber vibration sensing system of single light source pulse and sensing method thereof
  • Optical fiber vibration sensing system of single light source pulse and sensing method thereof
  • Optical fiber vibration sensing system of single light source pulse and sensing method thereof

Examples

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Embodiment 1

[0030] A fiber-optic vibration sensing system with single light source pulse encoding, see figure 1 The optical fiber vibration sensing system consists of a laser light source 1, a 1:99 coupler 2, a first multiple coupler 3, an acousto-optic modulator group 4 with different control frequencies, a second multiple coupler 5, and a fiber circulator 6. , Sensing fiber 7, 1:1 coupler 8, photodetector 9, band-pass filter circuit 10, mixer 11, signal generator 12, low-pass filter circuit 13, signal acquisition and conditioning module 14, host computer 15 and FPGA16 constitutes.

[0031] The laser light source 1 generates continuous light with a narrow line width, and generates probe light and local oscillator light through a 1:99 coupler 2. The probe light is divided into N channels of detection light through the first multiple coupler 3, and each path of detection light passes through the sound The light modulator group 4 forms a multi-channel pulsed light, in which the acousto-optic ...

Embodiment 2

[0034] A distributed optical fiber vibration sensing method based on pulse code modulation principle, heterodyne detection principle and phase sensitive OTDR principle, see figure 1 , The method includes the following processes:

[0035] 101: The host computer 15 controls N acousto-optic modulator groups 4 (AOM) with different control frequencies through FPGA16, and N*1 coupler 5 makes N mutually delayed short pulses form code length N, pulse The coded pulse light with a width of N*τ is injected into the sensing fiber 7 through the fiber circulator 6;

[0036] Lay a sensing fiber 7 in the range where vibration needs to be detected, and use the sensing fiber 7 as a sensor and signal transmission medium to realize vibration detection and monitoring. Select the encoding matrix S, the size of which is N*N, and select each row (length N) of the encoding matrix S as the encoding, then the host computer 15 controls N different control frequencies through the FPGA16 (the control frequenci...

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Abstract

The invention discloses an optical fiber vibration sensing system of a single light source pulse and a sensing method of the optical fiber vibration sensing system of the single light source pulse. Under the control of FPGA, a code is formed by an optical pulse, coded pulsed light is formed through a coupler, a sensing optical fiber is injected through an optical fiber circulator, interference is generated by backward propagation scattered light generated in the process of the propagation of the sensing optical fiber, the interference enters into the coupler through the optical fiber circulator to be interfered with local oscillating light, and beat frequency signals are generated; the beat frequency signals are converted into electrical signals by a photoelectric detector, difference frequency components are filtered through a band-pass filter circuit, the reduction of beat frequency is achieved through a frequency mixer, at last the signals are collected and amplified by a collection card, in an upper computer, the respective amplitude modulation and demodulation of each control frequency are achieved, and decoding and location processing are carried out. The optical fiber vibration sensing system of the single light source pulse has the advantages, peculiar to a distributed optical fiber detecting and monitoring system, of being distributed and subject to small external disturbance such as electromagnetism, the installation is convenient, and various vibration detecting and monitoring application, especially for long distance pipeline monitoring and perimeter security, can be met well.

Description

Technical field [0001] The invention relates to the field of optical fiber sensing, in particular to a single-light source pulse encoding optical fiber vibration sensing system and a sensing method thereof. Background technique [0002] Due to its high sensitivity, immunity to electromagnetic interference, wide detection range, and low cost, distributed optical fiber sensing systems are widely used in long-distance oil and gas pipeline monitoring, perimeter security, building structure health monitoring and other fields. Research hotspots. [0003] The Mach-Zehnder / Sagnac interferometer distributed optical fiber sensing system uses the detection of the phase difference changes caused by external disturbances in the two sensing optical paths, and locates through the method of related time delay estimation, which can have a good sense of vibration. However, due to the difficulty of determining the time delay by the relevant time delay estimation method, the positioning accuracy of t...

Claims

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Application Information

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IPC IPC(8): G01H9/00
Inventor 封皓施羿严雪莹曾周末靳世久
Owner TIANJIN UNIV
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