Noise reduction method based on timed frequency hopping in long distance optical fiber sensing system

The coherent optical time domain reflectometry (COTDR) based on Rayleigh scattering is an important technique for the monitoring of long distance fiber link, for its high dynamic range and high sensitivity. However, there are many kinds of fading noises which will disturb the extraction of effective signals in the COTDR system and will limit the performance of COTDR system in long distance monitoring environment. In order to remove the effect of coherent Rayleigh noise, a noise reduction method based on timed frequency hopping was proposed in this paper. The method of laser frequency controlled by software was proposed and then the application in long distance transmission line monitoring was discussed, the effectiveness of the described model and method was verified by experiments. The experiment results showed that the proposed methods could suppress the noise in the COTDR system effectively and improve the long distance optical fiber sensing performance significantly.