Algorithm Research Of Received Signal Processing In High-speed Direct Detection Optical Communication

Optical direct detection communication system is the first choice for short distance transmission because of its low cost and complexity.Direct detection optical communication has played a large part in optical communication between DC?data centers?and inter-DC.In this thesis,we mainly study and discuss the optical direct detection system through single-polarization system and dual-polarization system.Kramers-Kronig?KK?receiver is very popular in direct detection system to recovery the signal field,meanwhile it avoids the Signal-to-Signal Beating Interference?SSBI?and the frequency gap between carrier and signal.The research of single polarization direct detection focuses on the algorithm and the selection of scheme in KK receiver system:?1?To solve the problem of the signal up-sampling before KK receiver,an improved KK algorithm without up-sampling is proposed by us.We analyze the error of the proposed algorithm and compare it with existing algorithm.It is proved that our algorithm is more precise.Our improved KK algorithm in Single-Side-Band?SSB?system is verified by experiments and the performance of the traditional KK algorithm and proposed KK algorithm expanded to 1^st,2^nd,3^rd order is tested under different transmitting power and distance.It is found that when the transmission distance is more than 640 km,the performance of 2^nd order proposed algorithm is almost the same with traditional KK algorithm.?2?To choose a better dispersion compensation scheme of KK receiver system,the compensation in transmitter and receiver is compared by simulations and experiment.Results showed compensation in transmitter has higher robustness to dispersion under different Carrier-to-Signal-Power-Ratio?CSPR?,while compensation in receiver has lower BER.The dual polarization system has become the research hotspot to further increase the system capacity of the optical direct detection system.We studied the dual polarization system with Stokes receiver:To solve the problem of dispersion effect on de-polarization,a scheme with dispersion affected training sequence is proposed and its feasibility is verified by theoretical and simulation.And we simulate three kinds of system namely dispersion compensation in transmitter scheme,dispersion affected training sequence scheme,and API scheme in two different dual polarization system.It is concluded that API scheme needs no training sequence meanwhile requires lower CSPR and has lower BER in the same situation.So API scheme is the most recommended.