Design And Realization Of Dpsk Modulation And Demodulation In Dwdm Network

With the rapid growth of voice business and fast development of IP broadband network technology, the technology of dense wavelength division multiplexing (DWDM) in optical fiber communication system has been from10Gbps rate to40Gbps rate, and gradually transition to100Gbps rate. Due to the increase of transmission capacity and transmission instance in optical fiber communication system, the chromatic dispersion(CD), polarization mode dispersion (PMD) and nonlinear effect generated by the signal transmitted in the optical link has also increased as a consequence, which seriously affected the performance of optical fiber transmission system. For the problems of signal impairment in high-speed DWDM transmission systems, the article mainly focused on the designs and realizations of DPSK modulation and demodulation system from the aspect of novel modulation format. On the basics of that, we studied the modulation of differential quadrature phase-shift keying (DQPSK) and polarization division multiplexing-differential quadrature phase-shift keying (PDM-DQPSK) applied to the system with40Gbps or higher transmission rate. The artice put emphasics on the working principle of polarization de-multiplexing system, designed the polarization de-multiplexing system based on the RF power detection and verified the effect of polarization de-multiplexing system through the experiment. In addition, we realized the tunable wavelength light source, which can be used in the transmitting terminal of DWDM system. According to the proposed solution, the research works in the dissertation are summarized as follows:(?) The basic principles of DPSK modulation and demodulation are introduced in detail, the simulation platform of10Gbps DPSK modulation and demodulation system is built with the optisystem software. Besides, the performance parameters of post-demodulated signal’s waveform, eye diagram and spectrum utilization are observed.(?) The10Gbps DPSK modulation system are researched and developed, including hardware design and software realization of the system. The key modules, such as differential encoding, driving amplifer, are tested and verified. The DPSK demodulated signals are also analyzed at the same time.(?) The tunable wavelength light source used in the DWDM network is designed and realized, including hardware design and software realization. In the novel modulation format, such as the DPSK, the tunable wavelength light source not only used as the light source at the transmitting terminal, but also as a vibration source at the receival terminal, has many advantages, such as easy to operate, high emission power and narrow linewidth.(?) The modulation of differential quadrature phase-shift keying(DQPSK) and polarization division multiplexing-differential quadrature phase-shift keying (PDM-DQPSK) applied for40Gbps or higher DWDM transmission system are introduced. Some simulations about DQPSK modulation and demodulation are also conducted.(?) The techniques of polarization de-multiplexing in a polarization multiplexing system are studied, and the polarization de-multiplexing system based on the RF power detection is designed, including the design and testing of the hardware. Meanwhile, the search algorithm named of particle swarm optimization (PSO) is studied, and parts of logical control program based on FPGA are also realized. The effect of the method towards polarization de-multiplexing is verified through the experiment of polarization multiplexing system based on BPSK modulation. The innovation points of this article are summarized as below:(?) The real-time adjustment towards the gain point and the crosspoint of eye diagram as the situation of channel varies are realized. This is the key point that differs from other DPSK realizations.(?) The setting of the wavelength in a tunable wavelength light source is no longer dependent on the attached software with the laser. They can be set directly through the keys and displaying of LCD, which makes custom easier to use.(?) The polarization de-multiplexing system based on the RF power detection is designed, the logical algorithm and control are realized by the FPGA. The algorithm of PSO is used to search and track the global optimum value, to improve the response speed of the system as well.