Coherent optical time domain reflectometer based on phase conjugation double wavelets

Abstract

The invention provides a coherent optical time domain reflectometer based on a phase conjugation double wavelets. The reflectometer comprises a laser, a 1*2 optical coupler, an acoustic optical modulator, an optical circulator, an OTDR data processing module, a polarization multiplexing modulator and a polarization multiplexing coherent detector. The polarization multiplexing modulator is used for modulating two paths of phase conjugation COTDR detection electric signals on detection optical pulses and carrying out polarization beam combination on two paths of orthogonal modulated information so as to form detection optical signals transmitted on optical fibers. The polarization multiplexing detector is used for decomposing optical signals from detection light input ends into two paths of orthogonal signals, and mixing the orthogonal signals with local oscillation light from local oscillation input ends so as to carry out coherent detection. At last, the two paths of optical signals after the coherent detection are superposed and then output. According to the invention, the dynamic range of the coherent optical time domain reflectometer (COTDR) is expanded and the coherent optical time domain reflectometer is suitable for line detection of long distance optical fiber transmission.

Description

technical field [0001] The invention relates to optical fiber sensing technology, in particular to light detection technology. Background technique [0002] Optical time domain reflectometer OTDR is a kind of optical fiber detection instrument, which is mainly used for the measurement of optical fiber length, optical fiber transmission attenuation, joint attenuation and fault location. The optical time domain reflectometer OTDR detects the Rayleigh scattering generated when the optical pulse is transmitted in the optical fiber and the Fresnel reflection at the fiber break, where the backscattered light returns to the transmitting end after being scattered and reflected, and is captured by the OTDR. The detection pulse used by traditional OTDR is generally a single pulse with a certain width, and the detection method adopts non-coherent detection, which is generally used for the test of short-distance communication lines. However, in thousands or even tens of thousands of ki...

AI Technical Summary

Problems solved by technology

When the frequency of the detection light changes, the heterodyne intermediate frequency between it and the reference light will change. Once the heterodyne intermediate frequency signal falls outside the bandpass filter bandwidth of the system, the power of the signal will be lost, which will increase the slope of the detection curve.

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