Coherent fading noise suppression method in distributed optical fiber measurement of optical frequency domain reflectometer

Abstract

The invention discloses a coherent fading noise suppression method in distributed optical fiber measurement of an optical frequency domain reflectometer. The method comprises the steps that a laser generates high-coherence linear frequency sweeping laser under feedback control of an optical phase-locked loop module; high-coherence linear frequency sweeping laser is divided into two parts through a first polarization-maintaining coupler, one part of light with high energy enters a second polarization-maintaining coupler and is divided into two paths of optical signals, one path of optical signals generates N paths of echo signals, the N paths of echo signals and N paths of reference signals divided by the other path of optical signals interfere with each other through a third polarization-maintaining coupler, and beam combination is performed to generate optical beat signals; the beam-combined light beat signal is converted into an electric signal through a balanced receiver; acquiring electric signal data by using a synchronous acquisition card and converting the electric signal data into digital signals; performing vector weighted average processing on the digital signal to obtain a measurement signal of which the coherent fading noise is suppressed; according to the method, coherent fading noise is effectively suppressed, and the optical fiber distributed vibration measurement capability based on optical frequency domain reflectometer phase demodulation is improved.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, in particular to a method for suppressing coherent fading noise in distributed optical fiber measurement by an optical frequency domain reflectometer. Background technique [0002] The distributed optical fiber measurement technology based on optical frequency domain reflectometry (OFDR) phase measurement is a distributed real-time sensing system with both spatial distribution positioning and time change perception, which can realize the continuous measurement of the field spatial distribution of physical quantities along the optical fiber. ; Among them, long-distance, high-resolution, high-sensitivity and high-precision distributed measurement and perception capabilities are the core technical indicators of the system; its applications in hydrological monitoring, earthquake early warning, aerospace, smart cities, etc. Many areas of people's livelihood security have broad applicatio...

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Problems solved by technology

[0005] Another method is to carry out vector weighted average of non-correlated echo signals to achieve the purpose of suppressing coherent fading noise; using the characteristics of Rayleigh scattering related to the wavelength of the probe light, using different frequency sweeping light sources for measurement or Divide a frequency-sweeping light source into multiple sub-sweep frequency segments with different starting frequencies during data processing, so as to obtain multiple sets of Rayleigh echo signals with different amplitude statistical characteristics for vector addition; this method needs to sacrifice system complexity or spatial resolution, constraining system performance

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