Study On Distributed Optical Fiber Sensing Technology Based On Coding

Distributed optical fiber sensing technology has attracted attention in recent years.A huge market potential will emerge and the technology will be widely used in the fieldof pipeline, bridge, dam, cable, etc.The basic principles of Rayleigh scattering, Brillouin scattering and Ramanscattering occurred in optical fiber are introduced in this thesis. The principles of thethree kinds of distributed optical fiber sensing system based on these scattering arediscussed in detail.Distributed optical fiber sensing system based on Golay complementary sequencesare studied in this paper. The traditional conclusion has been revised. The traditionalconclusion is that the coding gain is proportional to the square of the code length.However, the results suggest that the traditional conclusion is correct only when the shotnoise power is much smaller than the thermal noise power. It is just suitable for weaksignals. Nevertheless, the increasing speed of the shot noise power is faster than thethermal noise power. So, the increasing speed of coding gain will decrease with thecode length increase. According to the theory, Distributed optical fiber sensing systembased on Golay complementary codes is simulated.Distributed optical fiber sensing system based on coding has been established inthis thesis. A detailed description of the working process of the system is proposed andthe structure diagram of experimental system is presented. Parameterized module basedon FPGA has been designed and it can produce unipolar Golay complementary codes.The pulse width, code length and cycle of these codes can be adjusted. The systemstructure and key technology of the High-performance distributed optical fiber sensingsystem are discoursed in detail. The Rayleigh scattering curve of the distributed opticalfiber sensing system based on coding is successfully detected. The starting position, tailend and breakpoint disrupted at10-kilometer position of optical fiber are also detected.Lastly, the experimental results show that Golay complementary sequences can beapplied to the distributed optical fiber sensing system and the sequences can improvesignal to noise ratio of the system without sacrificing the spatial resolution of distributeoptical fiber sensing system.