A linearly interpolated blind ICI suppressionalgorithmfor CO-OFDM system
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摘要: 本文提出一种高性能的基于线性插值的子载波间串扰盲抑制算法（LI-BL-ICI）。算法首先盲估计出次符号间相噪差值，而后进行线性插值拟合以获得更加精确的相噪估计，并将插值获得的相噪用于载波相位补偿，从而实现对子载波间串扰（ICI）的盲抑制，最后利用少量导频对残余的共同相位噪声进行估计和补偿。我们推导了算法的数学模型，通过蒙特卡洛仿真分别分析了算法在背靠背和320 km光纤传输后系统的性能，并与传统的共同相位噪声抑制算法（CPEC）和改进前的盲估计算法（BL-ICI）进行了横行对比。数值仿真结果表明，基于线性插值的算法能有效地抑制光相位噪声，其光源线宽的容忍度相比BL-ICI得到进一步的提升。此外，相比于BL-ICI，改进后的算法允许将次符号切割成任意块数，且在获取观测矩阵的过程中无需任何的角度相关运算。研究结果表明，算法存在一个适中的次符号切割块数，使得算法既能兼顾复杂度又能保证一定的系统性能。该算法对于相干光正交频分复用（CO-OFDM）技术在采用廉价光源和采用高阶调制格式的光接入/光城域网中的应用具有重要的意义。
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Abstract: We propose a high-performance blind ICI suppression algorithm, LI-BL-ICI, for CO-OFDM system based on linear interpolation. In the proposed algorithm, the difference of averaged optical phase noise between sub-symbols are estimated blindly, which are then linearly interpolated to get a more accurate estimation of the optical phase noise. The carrier phase is partially recovered with the linearly interpolated sub-symbol phase noise estimation, by which the inter-carrier-interference (ICI) is suppressed blindly. After ICI suppression, the common phase error of the residual optical phase noise is compensated with only a few pilot subcarriers. We present the theoretical derivation of the proposed algorithm and investigate the performanceof the proposed algorithm in CO-OFDM systems for both back-to-back and 320 km fiber transmission scenarios through Monte-Carlo simulations. The numerical results show that the linear interpolation based algorithm can effectively mitigate the impact of optical phase noise, and offers a larger laser linewidth tolerance than that of the BL-ICI algorithm.Compared with BL-ICI, the proposed algorithm also supports an arbitrary number of sub-symbols and does not need any angle-related operations when obtaining the observation-based matrix. The simulation results also verify that there exists a moderate number of sub-symbols for the proposed algorithm to balance the performance and complexity. The proposed algorithm is of great importance for the application of CO-OFDM in optical access/metro networks with low-cost laser sources and high-order modulation formats.-
Keywords:
- sub-symbol
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