Research Of Carrier Phase Recovery For Optical QAM Signal Coherent Detection

With the development of the broadband information network, the traditional Intensity modulation/Direct detection(IM/DD) optical fiber communication system can not meet the requirements of higher-capacity of data transmission in the future, how to upgrade the capacity of the optical communication system has become the focus in the development of optical communication. Optical coherent communication, based on advanced modulation format, coherent detection and digital signal processing has been considered as one of the most competitive technology for next generation high-speed optical communication systems due to the ability to not only achieve high speed transmission, but also compensation for impairments in electric field.Under this background, the key technology of carrier phase recovery in the coherent optical communication system is systematically studied, and the main work has been completed is by the following:1.The principle of traditional carrier phase recovery, Mth-power carrier phase estimation algorithm, is introduced, and a40Gb/s DQPSK coherent optical communication system is performed to simulate the performance of the system with different laser linewidths, and the impacts of the parameters involved in the algorithm on the performance of phase estimation are simulated and analyzed. The relationship between laser linewidths and the optimal parameter N is obtained. And the influence of the dispersion on carrier phase estimation is simulated and analyzed.2.In view of the higher order modulation format, the theoretical fundamental of a novel approach for star16-ary quadrature amplitude modulation (16-QAM) generation based on two parallel dual electrical Mach-Zehnder modulators (DeMZMs) driven by binary drive signals is explained. And the feasibility of this generation scheme is verified by simulation. This generation scheme can simplify the structure. In addition, it is directly driven by four binary signals without differential encoding. The star16QAM optical signal with2.41amplitude ratio of the outer ring and inner ring is generated.3. The16QAM carrier phase recovery algorithms in coherent optical communication system are studied. The classic carrier phase recovery algorithms for high-order modulation, such as Blind phase search algorithm(BPS), Improved blind phase search algorithm and QPSK partitioning and maximum likelihood detection, are introduced. Based on the star16QAM signal generation scheme, a100Gb/s star 16QAM coherent optical communication system is implemented. And the influence of the dispersion on carrier phase estimation is simulated and analyzed. In the case of complete dispersion compensation, the performance of the system with carrier phase estimation and without carrier phase estimation is compared. The impacts of the number of detection phases on the performance of carrier phase estimation are also simulated and analyzed.