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针对相干光正交频分复用(CO-OFDM)系统中光纤的色散和信号传输过程中噪声对系统可靠性的降低,提出了信道的冲激响应加窗(IRM,impulse response processed with window)算法,在最小二乘(LS)算法的基础上,通过时域加窗将信道冲激响应长度以外的噪声滤除,保证了信道冲激响应长度在OFDM保护间隔之内。在算法复杂度提高并不大的前提下,IRW算法系统误码率(BER)比LS算法降低了近1个数量级。仿真结果表明,在256个子载波的CO-OFDM系统中,BER为10-4时,IRW算法对系统信噪比(SNR)的要求比LS算法低了近2.5dB,而只比线性最小均方误差(LMMSE)算法高0.7dB;并且,IRW算法的复乘次数仅比LS算法高8倍,而比LMMSE算法的复乘次数低32倍。
Aiming at the dispersion of optical fiber in coherent optical orthogonal frequency division multiplexing (CO-OFDM) system and the reduction of system reliability caused by noise during signal transmission, impulse response processed with window (IRM) Based on the least-squares (LS) algorithm, the noise outside the channel impulse response length is filtered by windowing in the time domain to ensure that the channel impulse response length is within the OFDM guard interval. Under the condition that the complexity of the algorithm is not greatly improved, the system error rate (BER) of the IRW algorithm is reduced by nearly one order of magnitude compared with the LS algorithm. The simulation results show that the SNR of the IRW algorithm is about 2.5dB lower than that of the LS algorithm when the BER is 10-4 in a CO-OFDM system with 256 sub-carriers. However, it is only lower than the linear minimum mean square The error (LMMSE) algorithm is 0.7 dB higher; and the IRW algorithm multiplies only 8 times more than the LS algorithm and 32 times more complex than the LMMSE algorithm.