Performance Investigation Of Coherent Optical Orthogonal Frequency Division Multiplexing Transmission System In SSMF

Coherent opitcal orthogonal-frequency-division-multiplexing (CO-OFDM) is combinedwith coherent technology and OFDM technology. CO-OFDM systems can make use of hugebandwidth of optical fiber fully, increase transmission capacity, and transmission rates.Besides, it can be compatible with the existing network, and in the existing infrastructure, canbe upgrade easily and be expanded conveniently. It can be against nonlinear disturbanceeffectivly, has very good tolerance to polarization mode dispersion (PMD), and it has highspectrum efficiency, good signal-to-noise ratio, so in recent years has attracted much attentionand research.In this paper, the CO-OFDM single-mode optical fiber system is constructed by theMatlab coupled with the Optisystem. In the simulation,10Gb/s CO-OFDM transmissionsystems has been achieved in standard single mode fiber (SSMF). The channel estimationalgorithm in CO-OFDM systems is researched and has got the system performance based inthe LS algorithm and LMMSE improved algorithm. Besides, in the transmitter and thereceiver the fluence of laser to the phase noise is researched. We optimize hybrid mitigationalgorithm approach to high phase noise and low phase noise environment, and a hybridhalf-blind phase noise compensation algorithm is proposed and simulated.This work was supported by the Tianjin Science Foundation (No.11JCYBJC00100). Themainly works are expressed as follows:1. The key technologies of OFDM technology and its advantages and disadvantages areexplained. With reference to the light OFDM system model, the principle and thestructure model are discussed, and the whole signal process is researched in detail.2. Pilot design and selection, LS algorithm and improved LMMSE algorithm in theCO-OFDM systems are studied. The subcarrier interpolation algorithm is describedwhich will be used in the channel estimation. The The CO-OFDM single-mode opticalfiber system is constructed by the Matlab coupled with the Optisystem. And theinfluence of different channel algorithm on the receiver of system is researched. Thesimulation experiment of10Gb/s CO-OFDM transmission over640km standard singlemode fiber (SSMF), the performance of optical signal to noise ratio(OSNR) and bit errorrate(BER) have been analyzed. Compared with LS algorithm, the required receiverOSNR is reduced by about1dB using improved LMMSE algorithm at bit-error-rate(BER)=10-4in the intermediate frequency (IF) architecture CO-OFDM single-modeoptical fiber system. While in the direct conversion architecture, the required receiver OSNR is reduced by about1.5dB using improved LMMSE algorithm, which is betterthan IF architecture, but the direct conversion architecture CO-OFDM system costshigher price.3. The channel estimation is researched under the compensation of the phase noise,considering that different laser linewidth has diferent influence to the system noises.hybrid mitigation algorithm approach to high phase noise and low phase noiseenvironment is optimized, and a hybrid half-blind phase noise compensation algorithmis proposed. We simulate the CO-OFDM transmission over B2B and800km standardsingle mode fiber (SSMF), the performance of the system has been analyzed. A newalgorithm between high noise and low noise phase compensation is derived which canbe flexible to switch the laser linewidth conditions by adjusting the weighted value ofcompensation. The improved phase algorithm’s performance is better than matrix phasecompensation algorithm’s. With high linewidth conditions for16QAM modulation, a1dB improvement of OSNR penalty is obtained.