IMDD OFDM无源光网中的非线性分析和信号失真消除

提出一种子载波演化方法分析基于强度调制直接探测的正交频分复用无源光网络中的非线性。该无源光网络中的非线性主要来源于调制过程中的子载波混合干扰和啁啾。传输过程的光纤色散会导致调制时的各子载波最佳相位匹配条件不能维持，进一步导致信号恶化。设计了一种新的Volterra数字滤波器除信号失真。修正的Volterra数字滤波器不仅包含相同的采样点，还包括了不同的采样点。通过实验验证了该滤波器去除信号失真的效果；在FEC为10-3的情况下，实验结果与已经报道的结果相比提升3 dB了功率效益；传输25 km光纤与背对背相比，FEC为10-3时的功率亏损小于0.5 dB；系统的数据传输速率达到24.5 Gbps，频谱效率达到7 bits/s/Hz。实验结果表明提出的方法可以有效地消除信号的线性和非线性失真，能够有效地恢复信号。

Nonlinearity analysis and signal distortion cancelation in IMDD OFDM PON

A novel method of subcarrier evolution was proposed to analyze the nonlinearity of an intensity-modulation direct-detection(IMDD) orthogonal frequency division multiplexing(OFDM) passive optical networks(PON). The nonlinearity was mainly caused by the subcarrier-to-subcarrier intermixing interference(SSⅡ) and the chirp from the modulation. The fiber disperssion results in that the optical subcarrier can not keep the best initial phase matching condition which exacerbates the signal distortion. A new modified Volterra digital filter was also proposed to cancel the signal distortion of the IMDD OFDM PON. The modified Volterra digital filter included not only the same samples but also the different samples. The corresponding experiments had been carried out to verify the effectiveness of the proposed signal distortion cancelation method. The proposed modified Volterra filter could bring about 3 dB power benefits than the previous work to meet the forward error correction(FEC) limit of 10-3. The transmission penalty over 25 km at the FEC limit of 10-3 was lower than 0.5 dB. Finally, the system can reach a data rate of 24.5 Gbps, and the spectrum efficiency can achieve up to 7 bitss-1Hz-1. These experimental results prove that the modified Volterra filter can effectively compensate the linear and nonlinear distortion and therefore it can recover the signal at optical network unit (ONU).