The Simulation And Optimization Of Wavelength Shift-based Single-fiber Bidirectional System

According to the new Moore’s Law, the network traffic of communication system is double it of the previous year. Compared to conventional single-fiber unidirectional system, bidirectional transmission system improves the utilization of the fiber, reduces costs of communications and consumptions of resource. At the same time it can smoothly upgrade the current WDM system. It is an effective program to expand the transmission capacity of communication system.This article set up a simulation model for wavelength shift-based bidirectional WDM transmission system and proposes some programs to reduce dispersion and nonlinear effects of it. Firstly, the paper makes some research on the development of domestic and foreign bidirectional transmission system and analyzes the linear and nonlinear transmission characteristics of optical fiber communication system. Then the paper propose the wavelength-shift technology to reduce the impact of Rayleigh back scattering on the system and finally set up a simulation model for DQPSK modulation-based bidirectional WDM transmission system with optical circulator in Optisystem simulation software, which has eight channels with 40 Gbit/s for each one. When the transmission capacity is equal, the Q factor of the bidirectional WDM transmission system is improved mostly with 14.9 dB compared with unidirectional WDM transmission system. To further improve the performance of bidirectional system, this article proposes the program to reduce the dispersion and FWM of the bidirectional transmission system with step compensation, non-uniform channel spacing and non-uniform dispersion management. And the Q factor can be improved with 11 dB by the control of dispersion and FWM. Finally, the paper proposes a DP-16 PSK modulation-based bidirectional high-speed WDM transmission system, which has high spectrum efficiency and eight channels with 112 Gbit/s for each one. The constellation diagram is very clear and can be decoded correctly, which shows that the noise of system is small, and the sixteen phase points of demodulated signals are independent with each other. These programs provide an implementation for the next generation of commercial communication systems with 400 G or even higher bit rate.