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A coherent optical time domain reflectometer based on quadrature phase modulation of local oscillator light

A technology of time domain reflectometer and quadrature phase, which is applied in the field of optoelectronics, can solve the problems of small transimpedance of detection circuit, limit system measurement distance and positioning accuracy, limit system signal-to-noise ratio and sensitivity, etc., and improve the receiving signal-to-noise ratio and sensitivity, lower bandwidth requirements, and less thermal noise

Active Publication Date: 2021-03-26
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The main disadvantage of traditional OTDR is: the Rayleigh scattered light is very weak, and the signal-to-noise ratio obtained by direct photoelectric detection is not high, which limits the measurement distance and positioning accuracy of the entire system
Compared with direct detection, this method improves the signal-to-noise ratio and sensitivity of the system through the heterodyne method. However, due to the large frequency difference between the signal light and the local oscillator light (generally 100MHz ~ 200MHz, here is 200MHz ), it is necessary to use a photodetector with a large bandwidth, so that the transresistance in the detection circuit is small and the thermal noise is strong, thus limiting the system signal-to-noise ratio and sensitivity

Method used

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  • A coherent optical time domain reflectometer based on quadrature phase modulation of local oscillator light
  • A coherent optical time domain reflectometer based on quadrature phase modulation of local oscillator light
  • A coherent optical time domain reflectometer based on quadrature phase modulation of local oscillator light

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Embodiment 1

[0025] like figure 1 As shown, it is a schematic structural diagram of a coherent optical time-domain reflectometer based on local oscillator optical quadrature phase modulation provided in Embodiment 1 of the present invention; wherein, the narrow linewidth linearly polarized laser 1 adopts the ETH series narrow linewidth linearly polarized laser from Ethernal Corporation of the United States For fiber lasers, the linewidth can reach within 400Hz. The narrow-linewidth linearly polarized laser 1 outputs a narrow-linewidth laser beam of 1550nm, which is divided into two beams by the optical beam splitter 2, one of which enters the optical intensity modulator 3, and generates pulsed laser light through modulation. The pulsed laser input port of the device 4 is input; then through the duplex port of the optical fiber circulator 4, the polarization maintaining sensing fiber 5-1 is input, and the echo light signal generated by scattering in the polarization maintaining sensing fibe...

Embodiment 2

[0032] like Figure 5 As shown, it is a schematic structural diagram of a coherent optical time-domain reflectometer based on local oscillator optical quadrature phase modulation provided in Embodiment 2 of the present invention; in Embodiment 2, the polarization-maintaining sensing fiber 5-1 in Embodiment 1 Replace it with a single-mode sensing fiber 5-2, and add a fiber polarization controller 11 between the signal light output port of the fiber circulator and the input port of the polarization-maintaining fiber coupler. The polarization direction of the signal light input to the polarization-maintaining fiber coupler 7 is adjusted by the fiber polarization controller 11, so that the polarization directions of the local oscillator light and the signal light are consistent, and the signal light intensity can be correctly demodulated at this time, and the single-mode Sensing fiber 5-2 can significantly reduce system cost.

[0033] In the coherent optical time-domain reflectom...

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Abstract

The invention relates to a coherent optical time domain reflectometer based on local vibration light quadrature phase modulation and belongs to the technical field of photoelectron. The coherent optical time domain reflectometer comprises a narrow linewidth linear polarization laser, an optical beam splitter, a light intensity modulator, an optical fiber circulator, a polarization-maintaining sensing optical fiber, an optical-phase modulator, a polarization-maintaining optical fiber coupler, a balance detector, a signal processing circuit and a square signal generator; the square signal generator generates a period square signal and inputs the period square signal to the optical-phase modulator, so that the phase of local vibration light is modulated through phase shift keying, under the effect of the square signal generator, the signal processing circuit identifies signals obtained at different additional phases by the balance detector through delaying, and accordingly signal processing is conducted. The demand of the coherent optical time domain reflectometer on a photoelectric detection circuit is greatly reduced, the photoelectric detection circuit is large in transimpedance and small in hot noise, the reception signal to noise ratio of the system is effectively increased, and the flexibility of the system is effectively improved.

Description

technical field [0001] The invention belongs to the technical field of optoelectronics, and in particular relates to a coherent optical time domain reflectometer based on local oscillator optical quadrature phase modulation. Background technique [0002] Optical time domain reflectometer (OTDR) is based on the principle of Rayleigh scattering and Fresnel reflection of light, and uses the backscattering and reflection light generated when light propagates in the optical fiber to obtain relevant optical information of the device under test. , can be used to measure fiber attenuation, joint loss, locate fiber fault points, etc., and be used for sensing parameters such as fiber temperature, vibration and stress. It is a powerful tool for fiber construction, maintenance and monitoring. This technology was first proposed by Barnoski et al. in 1976. So far, optical time domain reflection technology using Rayleigh scattering, Raman scattering and Brillouin scattering has received ex...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01D5/353
CPCG01D5/353
Inventor 王云祥李天鹏郭键聪邱琪廖云史双瑾苏君王智勇
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA