基于符号映射分析的CO-OFDM系统信道估计研究

Channel estimation based on analysis of symbol mapping for CO-OFDM system

针对相干光正交频分复用(CO-OFDM)系统中光纤信道快变对系统可靠性和有效性的降低,设计了一种符号映射分析(ASM,analysis of symbols mapping)算法,通过对接收到的OFDM符号星座图进行分析,不断地对由信道估计得到的传递函数进行修正,在不需要大量导频的情况下能快速跟踪信道的变化。仿真结果表明:在40Gb/s的快变光纤信道CO-OFDM系统中,信噪比(SNR)为10dB,在误码率(BER)为10-3时ASM算法比常规的迫零估计(ZFE,zero forcing estima-tion)算法需要的导频间隔减小了1/2;在导频间隔为10、BER为10-3时,ASM算法比常规的ZFE算法有约3.5dB的SNR改善。

To reduce the influence of fast-varying fiber channel on reliability and validity of coherent optical orthogonal frequency division multiplexing （CO-OFDM） system, we present a new channel estimation method based on analysis of symbols mapping （ASM） applied to this fast-varying fiber channel. This method analyzes the constellation diagram of the received OFDM symbol, and then the channel＇s transfer function is modified constantly. That is to say this method can fast track the change of fast-varying fiber channel,and at the same time, this way doesnr t need a large number of pilots for channel estimation. Through simulation, we can show that in 40 Gbit/s fast-varying fiber channel CO-OFDM system, while the signal-to-noise ratio （SNR） is 10 dB and systemrs bit error rate （BER） is 10^-3 ,the pilot interval of ASM algorithm is reduced half compared with the conventional zero forcing estimation （ZFE） algorithm. While the pilot interval is 10 （every ten OFDM symbols inset one pilot） and system＇s BER is 10^-3 , compared with conventional ZFE algorithm, ASM algorithm has 3.5 dB SNR improvement.