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Pilot-frequency dual-pulse COTDR (Coherent Optical Time Domain Reflectometry) sensing device and method

A sensing device and double-pulse technology, applied in measuring devices, instruments, measuring ultrasonic/sonic/infrasonic waves, etc., can solve the problem of limiting the scope of application of COTDR technology, affecting the stability of COTDR sensing signal-to-noise ratio and applicable environmental range, phase Noise COTDR signal phase interference and other problems, achieve the effect of stable return optical signal intensity, eliminate phase change at no vibration, and improve robustness

Active Publication Date: 2018-11-16
TIANJIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Because COTDR technology uses local reference light and back Rayleigh scattered signal light for mixed amplification, the phase noise of the light source and the reference light path are subject to external vibrations, which will cause the phase of the COTDR signal to be disturbed
This directly affects the COTDR sensing signal-to-noise ratio, the stability and applicable environmental range in practical engineering applications, and limits the scope of application of COTDR technology in practical engineering applications.

Method used

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  • Pilot-frequency dual-pulse COTDR (Coherent Optical Time Domain Reflectometry) sensing device and method
  • Pilot-frequency dual-pulse COTDR (Coherent Optical Time Domain Reflectometry) sensing device and method
  • Pilot-frequency dual-pulse COTDR (Coherent Optical Time Domain Reflectometry) sensing device and method

Examples

Experimental program
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Effect test

Embodiment 1

[0040] Example 1: A COTDR sensing device with different frequency and double pulses

[0041] Such as figure 1 As shown, light source 1 emits frequency f 0 The continuous laser light passes through the 1×2 coupler 2, and is divided into two paths of local reference light and signal light: the signal light passes through the frequency-shift pulse modulator 4 controlled by the modulation signal generating device 3, and the frequency of the modulated light is f 0 +f 1 and f 0 +f 2 , with a width of W 1 and W 2 , interval W 0 The different frequency double pulse, where f 1 , f 2 are the frequency shift frequencies of the two pulses respectively; the double pulses with different frequencies are amplified by the erbium-doped fiber amplifier 5, transmitted by the optical fiber circulator 6, and injected into the sensing fiber 7, and the double pulses with different frequencies are transmitted along the sensing fiber 7, and Backward Rayleigh scattering is generated sequentiall...

Embodiment 2

[0052] Example 2: A COTDR sensing method with different frequency and double pulses

[0053] Such as figure 1 As shown, the light source emits frequency f 0 The continuous laser light is divided into two paths of local reference light and signal light through a 1x2 coupler; the signal light is modulated into optical frequencies f 0 +f 1 and f 0 +f 2 , with a width of W 1 and W 2 , interval W 0 The different frequency double pulse, where f 1 , f 2 are the shift frequencies of the two pulses, respectively. Wherein, the modulation signal of the modulation signal generating device is as follows figure 2 The change shown, in each repetition period T, contains 2 pulse signals, each with a width of W 1 and W 2 , the pulse interval is W 0 . The different-frequency double pulses are amplified by the erbium-doped fiber amplifier and the circulator successively, and then injected into the sensing fiber. Demodulated phase information φ 1(t) , the light frequency is f 0 +...

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Abstract

The invention discloses a pilot-frequency dual-pulse COTDR (Coherent Optical Time Domain Reflectometry) sensing device. The characteristics are that the device comprises a light source (1), a 1*2 coupler (2), a modulation signal generating device (3), frequency shift pulse modulator (4), an erbium-doped optical fiber amplifier (5), an optical fiber circulator (6), a sensing optical fiber (7), an optical mixer (8), a first photoelectric device (9), a second photoelectric device (10) and a signal acquisition and demodulation device (11), pilot-frequency dual pulses are injected into the sensingoptical fiber, returned signal light carrying phase information of each detection point is mixed with local reference light, the phase information is obtained through demodulation, and vibration information at each part in the sensing optical fiber is obtained. Compared with the prior art, the phase change caused by phase noise of the light source at a non-vibration position is eliminated throughthe phase difference of two pulses, the signal-to-noise ratio of the COTDR vibration sensing is improved, the sensing noise caused when a reference light path is subjected to external vibration is eliminated, and the robustness of the COTDR and the stability in practical engineering application are improved.

Description

technical field [0001] The present invention relates to the technical field of coherent optical time domain reflection and signal demodulation, in particular to a Background technique [0002] Coherent Optical Time Domain Reflectometry (COTDR) sensing technology has a wide range of applications and demands in building structure health monitoring, mineral detection, submarine optical cable monitoring, and underwater monitoring. COTDR sensing technology mixes and amplifies the local reference light and the Rayleigh scattered light signal injected into the optical fiber, and demodulates to obtain the optical phase information of the sensing optical fiber, so as to detect the phase of the optical fiber caused by external vibration and acoustic signals in real time Changes, and then realize the identification and positioning of vibration sources and sound sources. For example, in terms of safety monitoring along oil and gas pipelines, the COTDR device can monitor pipeline leaks ...

Claims

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Application Information

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IPC IPC(8): G01H9/00
CPCG01H9/004
Inventor 刘铁根江俊峰陈文杰刘琨王双马喆张学智
Owner TIANJIN UNIV
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