Polarized light time domain reflectometer based on three-polarization-state time division multiplexing and detection method

Abstract

The invention discloses a polarized light time domain reflectometer based on three-polarization-state time division multiplexing. The polarized light time domain reflectometer comprises a light source, a polarization state generator, a pulse modulator, a circulator, a sensing optical fiber, a dual-polarization state detection device, a photoelectric detector, a signal acquisition card and a processor, wherein the processor is connected with the polarization state generator; the polarization state output by the polarization state generator is controlled to be switched among the three polarization states perpendicular to one another; and polarization detection is achieved through the double-polarization-state detection device, so that under the condition that depolarization is not considered, the phenomenon of traditional POTDR signal fading is completely eliminated, and the effect of improving system positioning and event recognition stability is achieved.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, and more specifically relates to a polarized light time-domain reflectometer based on time-division multiplexing of three polarization states. Background technique [0002] Limited by the inherent properties of the polarization state, in fiber optic polarization sensing, it can be divided into polarization insensitivity at the sensing point (the change of the polarization state of light caused by external disturbances is small) and polarization insensitivity at the detection end (optical detector). Sensitive (on the Poincare sphere, the change track of the polarization state is perpendicular to the analyzer). For example, the patent of Chinese Invention Patent Publication No. CN107328462A proposes to use a dual polarization analyzer to analyze the polarization of two components with different polarization angles, so that the cost of the optical fiber sensing system is not significan...

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Problems solved by technology

[0003] However, there are problems in the above scheme: 1. Due to the failure to fully analyze the input polarization state of the optical signal and the polarization state sensitivity of the detection end, the dual polarization state analysis with an included angle of 45 degrees can only alleviate or improve the insensitivity of the detection end polarization analysis The problem is that the change direction of the polarization state at some sensing points is perpendicular to the two analyzers at the same time, so that the weak change of the light intensity after the analysis cannot be observed on the two analyzers; 2. Single polarization state In the optical signal input, because the polarization sensitivity of the optical signal changes with the phase change of the polarized optical signal, there are still some sensing points on the sensing fiber in the insensitive area, and there is still the problem of insensitivity of the sensing point

Although light waves of different wavelengths can obtain different polarization states in the rotation axis at the output end of the polarization-maintaining fiber through the polarization-maintaining fiber, these light waves cannot maintain the correlation of the polarization state during the transmission of the single-mode fiber used for sensing. Furthermore, the complementarity of its final sensitivity cannot be maintained, and the insensitive position cannot be completely eliminated. The detection end of this patent uses a single polarization analyzer (N different directions) for each wavelength of light wave. The change direction of the polarization state on the point and the problem that the two analyzers are perpendicular at the same time

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