The Research Of The Transmission Performance Of DQPSK In The High-speed Optical Communication Systems

With the rapid growth of40Gb/s dense wavelength division multiplexing(DWDM) fiber-optic transmission system. The system facing some typical problems such as group velocity dispersion(GVD),nonlinear and polarization mode dispersion(PMD). These problems become the main factors which influence the effect of fiber-optic transmission system. Advanced modulation formats is the key technology for the transmission system which can reduce the transmission damage in order to improve the spectral efficiency and system transmission capacity.This paper analyzes the characteristics of optical signal propagation, focus on the40Gb/s optical fiber communication system and some simulations for the DQPSK, including the following areas:1. Research the core technology of the high-speed optical communication system, analysis of amplitude, phase and polarization modulation of the three kinds of modulation and demodulation principle, for the DQPSK modulation, a simulation model was created, as a result, the frequency spectrum and eye diagram of DQPSK were generated.2. Established a modulation format of DQPSK with shifting distance simulation model used in the transmission distance. Two ways are used in the transmission simulation. Simulation found that CS-RZ-DQPSK modulation provides a better performance than both NRZ-DQPSK and RZ-DQPSK.3. Established a modulation format of DQPSK with dispersion resistance simulation model. This model calculated the dispersion properties for different modulation formats. Simulation found that33%CS-RZ-DQPSK modulation format is the best choice in dispersion resistance.4. Established a modulation format of DQPSK with non-linear effect resistance simulation model. The simulation compared the nonlinear effects resistance for different modulation formats. Simulation shows a conclusion that33%CS-RZ-DQPSK has the maximum tolerance to nonlinear effect.