Study Of Modulation And Demodulation Methods Of Sensor Signal Based On The Fiber Optic Communication Networks

In recent years, fiber optic communication has developped so fast and been used so widely that it has been the important stanchion and played a significant part in modern communication. The domestic and foreign fiber optic communication signals and the fiber optic sensing signals all run in the respective network, creating the numerous repeating constructions, redundant manpowers and the physical resource waste. Therefore, the combine of the optical fiber sensing network and the fiber optic communications network has the broad application prospect and the huge economic efficiency. This article mainly studies modulation and demodulation methods of sensing signals based on optical fiber communications networks.This article has analyzed the modulation and demodulation methods and the principle of digital communication, and has designed one kind of sensing signal modulation and the demodulation system based on the fiber optic communications system transmiting the digital and the simulated signals together. The system is divided into two parts, one is QAM, the other is SCM. QAM system consists of signal generating device, phase inverter, RSOA, electro-optical detector, integral decision and so on. SCM system consists of AM modulation demodulation, the power mixer, the shunt, the filter and so on.It has constructed the simulation model in the OPTISYSTEM software to analyse the performance. It analyzes the QAM modulation principle of digital baseband signal, subcarrier modulation and the demodulation principle of the sensing signal under the simulation platform, and made the analysis of the input and output wave shape, Q factor and eye chart parameters and so on. It does not make use of the traditional modulator but RSOA to modulate the digital baseband signal, at the same time to realize the purpose of signal modulation and enlargement. And it also has It increased the frequency band utilization making use of QAM to modulate and demodulate the digital baseband signal. When both simulation sensing signal and digital baseband signal pass the SCM system, it can make the digital-analog composite signals transmission possible into one fiber at the same time and has bigger flexibility.Through the observation and the analysis of the simulation results, it has proven system feasibility on the physical level, it develops the potential of light access network, raises the light access network efficiency and has realized the modulation and the demodulation of combine signal making use of optical fiber access network. And it has the important guiding sense to the new fiber optic communications and the sensing network application.