Optical fiber length measuring method and measuring device

Abstract

The invention relates to an optical fiber length measuring method and device and belongs to the technical field of optical measuring. The method includes: modulating microwave signal strength in a continuous optical carrier to generate a modulated optical signal; using the modulated optical signal as the probe light, injecting the modulated optical signal from one end of a to-be-measured optical fiber, and receiving the reflecting optical signal of the second end of the to-be-measured optical fiber from the first end of the to-be-measured optical fiber; converting the reflecting optical signalinto an electric signal, extracting a base-frequency signal from the electric signal, and measuring the phase change of base-frequency signal relative to the microwave signal; acquiring the length ofoptical fiber according to the phase change. Compared with the prior art, the optical fiber length measuring method and device can perform high-precision measuring on large-range optical fiber length.

Description

technical field [0001] The invention relates to a method for measuring the length of an optical fiber and a measuring device, belonging to the technical field of optical measurement. Background technique [0002] The commonly used optical fiber length measurement methods mainly include backscattering method, pulse method and phase shift method. The backscattering method uses the backscattered light generated by Rayleigh scattering and Fresnel reflection when light is transmitted in the optical fiber. To measure the length of optical fiber, the optical time domain reflectometer developed by using this principle has been widely used in the construction and maintenance of optical fiber communication links. There are many unavoidable errors in this method, such as instrument resolution error, fiber group delay and backscattering loss coefficient, etc. Therefore, the measurement accuracy of the optical time domain reflectometer is only on the order of meters, and as the length o...

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Problems solved by technology

[0004] In summary, the prior art has the following disadvantages: (1) the measurement accuracy of the optical time domain reflectometer (OTDR) is not high, and can only reach the meter level; while the measurement range of the optical coherent domain reflectometer (OCDR) is too small, Unable to perform long-distance optical fiber measurement, and has high requirements on the light source

(2) The high-precision optical fiber length measurement system proposed by Liang Jian et al. is to measure the round-trip time difference in the optical fiber under test by adding a Faraday rotating mirror, which reduces the measurement dynamic range of the system. In addition, the system requires an external modulator Adding a polarization controller to control the polarization state of the optical signal greatly affects the measurement repeatability and stability of the system

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