Research On Channel Estimation And Polarization Division Multiplexing For DDO-OFDM Systems

The orthogonal frequency division multiplexing(OFDM)technology has received a lot of attentions and actively investigated in optical communications due to its high spectrum efficiency,flexible spectrum allocation and anti-interference ability.The OOFDM system based on the direct detection(DDO-OFDM)is very easy to beimplemented and has the merits of low cost and stability operation.This paper focuses on DDO-OFDM system as a reference for the study of OFDM systems by three parts.The first part focuses on the relevant aspects of the peak-to-average power ratio of suppression,the second part focused on the improvment of the LS channel estimation algorithm from two aspects,the third part is building a polarization division multiplexed optical OFDM system and related simulation.Firstly,after the optical OFDM system and chaotic system a brief introduction,the article introduces the DDO-OFDM and CO-OFDM system.Combined Optisystem simulation software and Matlab simulation software to build the DDO-OFDM system simulation model for the study of the text as a platform.The main work and innovation of this paper include the following aspects:(1)By analyzing the Trellis coded modulation algorithm(TCM)and linear companding transform algorithm(LCT),get a hybrid algorithm for optical OFDM system.And through various comparison,hybrid algorithm can get a good result for reducing the PAPR there.But also found that the hybrid algorithm will rise the system BER,which is the main drawback of hybrid algorithm.(2)For the pilot-based channel estimation algorithm features,we proposed improvements of LS channel estimation form both secrecy and accuracy.By analyzing the time domain averaging algorithm(TDA)and intra-symbol frequency averaging algorithm(ISFA)proposed a hybrid algorithm.It is proved that the new with hybrid algorithm more efficient than conventional DFT channel estimation algorithm.And combine chaotic systems with pilot to enhance the OFDM system secrecy.The simulation,does achieve the desired results.(3)Based on the idea of polarization division multiplexing building a PDM-DDO-OFDM system and analysis the difference of channel transmission betweent traditional system and the system with polarization division multiplexing,and through simulation experiments,to obtain a clear constellation.And through the analysis,to further improve the bandwidth efficiency polarization division multiplexing system,proposed a impoved pilot model.Finally,based on CO-OFDM system build the PDM-CO-OFDM system.