Probabilistic Shaping Technique Based Wavelength Division Multiplexing Passive Optical Network

The upcoming services,such as cloud storage,4k/8k video application,augmented reality,are urgent for access network with high capacity and data rate.Wavelength division multiplexing passive optical network(WDM-PON)with high capacity and low latency is considered as a promising candidate for next-generation heterogeneous access networks.Probabilistic shaping(PS)is a particularly promising technology in WDM-PON due to its high SE,large capacity and low computation complexity.PS has been adopted in high level modulation to achieve enhanced received power sensitivity(RPS).Combined with several coding techniques such as LDPC,the PS scheme is able to achieve higher spectral efficiency(SE)at the expense of computing complexity.In this thesis,a WDM-PON employing PS scheme and preequalization is investigated.And the thesis is stated as following:1.The system performance by introducing a blind adaptive pre-equalization based on the joint applications of constant modulus algorithm and decision-directed least-mean-square error algorithm,which can accurately compensate for the signal high frequency loss caused by the electro-optical components such as digital-to-analog converter,optical modulators and electrical drivers at the OLT,is also experimentally investigated.And the pre-equalization based on a reference signal is also investigated and practically utilized in WDM-PON employing 16 QAM for a better compensation.2.A wavelength-division-multiplexing passive optical network(WDM-PON)employing probabilistic shaping 4-level pulse amplitude modulation(PS-PAM4)with direct detection is proposed and experimentally demonstrated.Each optical carrier at the optical line terminal(OLT)carries a 25-Gbaud PS-PAM4 signal based on MaxwellBoltzmann distribution.By employing PS-PAM4,the receiver power sensitivity(RPS)and fiber nonlinear effect tolerance of the system can be significantly improved and enhanced compared with the unshaped one,which can provide abundant system loss budget for the legacy optical distribution networks.3.The WDM-PON employing low-density parity-check(LDPC)coded PS PAM8 signals over 20-km standard single-mode fiber(SSMF)with direct detection is proposed and experimentally demonstrated.The transmitted signal are shaped based on a designed Maxwell-Boltzmann distribution.A LDPC-based bit-interleaved coded modulation scheme with iterative decoding(BICM-ID)is utilized to identify the inherently overlapped symbols in the PS mapping method.Additionally,the discreteFourier-transform spread(DFT-spread)discrete multi-tone wavelength division multiplexing passive optical network(DMT-WDM-PON)employing probabilistic shaping 16-ary quadrature amplitude modulation(PS-16QAM)is experimentally demonstrated.Compatible with the forward error correction(FEC)implemented in most of the optical transponders today,an optimized bit-interleaved coded modulation iterative decoding(BICM-ID)system based on LDPC coding is proposed to encode the probabilistically shaped signal without any extra shaping codes or overheads.Then the labeling optimization with the assistance of extrinsic information transfer(EXIT)chart is investigated,in which the extrinsic messages are transferred between the PS demapper and the LDPC decoder for retrieving the PS signal.