Research And Design Of OFDM PON Receiver Based On FPGA

Orthogonal Frequency Division Multiplexing(OFDM)Passive Optical Network(PON)has the advantages of high spectral efficiency,anti-dispersion and flexible resource allocation.However,due to PON's low cost requirements and point-to-multipoint structure,the high Peak to Average Power Ratio(PAPR)of OFDM and the sensitivity to synchronization offset are more prominent.In this paper,considering the real-time and low-cost Intensity Modulation/Direct Detection(IM/DD)OFDM PON structure and characteristics,the above two problems are studied.The specific work is as follows:In the aspect of PAPR suppression,aiming at the problem of high complexity of Selected Mapping(SLM)algorithm,a novel binary sequence cyclic shift strategy is proposed.Simulation and optical fiber transmission experiments show that this algorithm has PAPR suppression and bit error rate performance similar to SLM algorithm while reducing the complexity.In terms of synchronization,the calculation result of the cross-correlation Symbol Timing Synchronization(STS)algorithm is affected by the received power and requires a lot of multiplication operations.A proportional Symbol bit cross-correlation STS algorithm is proposed to solve above two problems.Simulation and optical fiber transmission experiments show that,in the presence of Sampling Clock Offset(SCO),the starting position of each OFDM symbol can still be accurately found according to the set constant detection threshold.In addition,SCO estimation and frequency compensation strategies for the system are analyzed.Finally,the Field Programmable Gate Array(FPGA)is used to design the core part of OFDM PON baseband receiver,which further verifies the effectiveness of the algorithms at the hardware level.In this paper,the existing schemes of synchronization and PAPR suppression in optical OFDM are improved,and the applicability of the proposed algorithm to low-cost and real-time OFDM PON is illustrated from three aspects,including numerical simulation,optical fiber offline transmission experiment and FPGA hardware design.