Research On The Transceiver And Transmission Performance Of New Modulation Formats In Broadband Optical Access Systems

Recently,with the continuous development of new technologies and the rise of interactive multimedia,e-commerce,intelligent transportation and other new services in communication networks,the global internet traffic is increasing.The demand for network access bandwidth is also increasing dramatically,which puts forward the requirements of large capacity and low latency for the development of broadband access system.Considering that while improving the bandwidth capacity of broadband optical access system,it is must be ensured that the transceiver performance of access signals does not decline as well as possible.Therefore,the generation,reception and transmission models of several new modulation formats are modified in the broadband access system to be suitable for practical applications.In addition,the broadband access signal formed by the improved new modulation format can not only improve the system bandwidth utilization,but also optimize the configuration of related photoelectric devices,so it also has a very important theoretical value and practical significance.In this paper,the transceiver performance of a few novel modulation formats in the broadband optical access system are studied.Firstly,the application characteristics of broadband optical access systems?including optical fiber access system,free-space optical?FSO?access system,and radio over fiber?RoF?access system?are described through analyzing research status at home and abroad.And then,the modulation and demodulation principles of several new modulation formats?including duobinary?DB?,pulse amplitude modulation?PAM?,quadrature amplitude modulation?QAM?and orthogonal frequency division multiplexing?OFDM??are analyzed.Finally,the new modulation format is improved and the simulation or experimental research is carried out on the reception and transmission performance of access signals in the broadband optical access system.A duobinary downlink access system scheme using a low pass filter is proposed and proved,and we have successfully realized the transmission process over 20 km single-mode fiber?SMF?.A 10Gb/s DP-DB optical fiber converged FSO channel access system scheme is also designed and proved,and the characteristic of signals transmissions are analyzed and compared by using three transmission modes?back-to-back,50 km SMF,and 50 km SMF converged 100 m FSO channel?.The DP-DB FSO access system with different amplification schemes?pre-amplification,hybrid-amplification and post-amplification?is studied.By the comparative analysis of the received eye diagrams and bit error rate?BER?of DP-DB signal in different amplification schemes to analyze the transmission performance difference.A scheme of optical fiber access system using 8PAM optical signal is designed and proved,and the experiment on the generation and transmission of 8PAM signal is carried out.The experimental results show that the 8PAM signal can not only effectively improve the frequency band utilization of access signal,but also the receiver sensitivity value is-16.5dBm when the BER is 10^-3.A new scheme of 32QAM-OFDM-PON access system is presented and proved,and the 5Gb/s 32QAM-OFDM downlink signal with different numbers of sub-carriers has successfully transmitted over 42 km SMF.The experiment results show that the 32QAM-OFDM signal with 128 subcarriers has higher spectral efficiency than a 32QAM-OFDM signal with 64 subcarriers,and the peak-to-average ratio?PAPR?and computational complexity are lower than those of a 32QAM-OFDM signal with 256 sub-carriers,which is more suitable for practical application.