Performance Analysis And Architecture Optimization Of Optical OFDM System

Optical Orthogonal Frequency Division Multiplexing(OFDM)technology became a hotspot to improve the information transmission rate and system capacity since its high frequency efficiency,diverse carrier modulation schemes and the convenience of digital signal processing.This paper mainly studied on optical OFDM areas,and the main work was reflected in the following aspects:Analyzed the practicability of using Multiple-Input Multiple-Output(MIMO)techniques for channel estimation in Polarization-division Multiplexed(PDM)optical OFDM system.Comparatively analyzed the principle of using an improved orthogonal training sequences and conventional training sequences for polarization multiplexing 2×2 MIMO channel estimation,and accordingly built the Quadrature Phase Shift Keying(QPSK)PDM-DDO-OFDM simulation system.The simulation results showed that when transmitting for 500km in the ordinary single-mode fiber,the OSNR was 12.5dBm and the optical launch power is-6dB,the improved conventional quadrature orthogonal training sequences could improve system's-log(BER)value of about 5.51%compared with the conventional training sequences,which indicated that the improved orthogonal training sequence was better than conventional training sequence training sequence when used for orthogonal polarization multiplexed system's channel estimation.Analyzed the principle of Polarization Multiplexing Coherent Optical Orthogonal Frequency Division Multiplexing(PDM-CO-OFDM)system.A scheme of adding blank guard interval besides two sides of Pilot was proposed,which could improve the quality of channel estimation and carrier-phase estimation meanwhile ensuring the same information transmission rate.According to the analysis,16 Quadrature Amplitude Modulation(QAM)PDM-CO-OFDM simulation platform was set up.The simulation result showed that when transmitting 500km in ordinary single-mode fiber,using the pilot scheme with four pairs of guard subcarriers could reduce the value of system's BER for about 7.52%.