Investigation On Demodulation And Transmission Characteristic Of DPSK Signals

As a novel optical modulation format, differential phase-shift keying (DPSK) has become a hot topic in the large-capacity and long-haul optical communication technologies. Under the support of the Program for New Century Excellent Talents in University of Ministry of Education, the demodulation technology and the transmision characterictic of DPSK is investigated theoretically and experimentally, and tunable DPSK demodulator using the Mach-Zehnder interferometer is invented. The studies are carried out as the followings:(1) The research signification of DPSK is discussed, and the survey of DPSK transmission research and the methods of demodulation are summarized.(2) The theory of DPSK modulation is analyzed, and the formulas of NRZ-DPSK, RZ-DPSK, and CSRZ-DPSK are educed. Via the numerical simulation, the waveform and spectrum of DPSK is simulated, and compared with on-off keying (OOK).(3) The theory of DPSK modulation is analyzed, and the transmission matrix of Mach-Zehnder interferometer (MZI) is educed. Via the simulation using the software, the influence of the MZI parameters to DPSK demodulation is analyzed.(4) Tunable DPSK demodulator based on fiber MZI is investigated. The temperature of the fiber arm is set by the temperature control system of the demodulator. 40Gbit/s DPSK signal was demodulated successfully in the experiment. The experimental results have a long-time stability and can be switched between constructive interference and destructive one.(5) The tolerance of nonlinear effect and dispersion in DPSK is analyzed, and three schemes of dispersion compensation are compared in DPSK transmission. The experiments of 40Gbit/s back-to-back and long-haul transmission are accomplished. The performance of different bit rate signals is measured, and the transmission characteristic is compared between DPSK and OOK.