The non-Hermitian symmetric optical orthogonal frequency division multiplexing (NHS-OFDM) system exhibits lower hardware implementation complexity and power consumption as maintaining the same bandwidth granularity, compared to the conventional Hermitian symmetric optical OFDM (HS-OFDM) system. Also, NHS-OFDM can obtain a similar peak-to-average power ratio as well as bit error rate (BER) performance. It is expected to be a new candidate for the next-generation passive optical network. In the asynchronous NHS-OFDM system, the sampling clocks for the analog to digital converter in the receiver and the digital to analog converter in the transmitter generated from different sources and their frequencies always have a certain degree of deviation, i.e., sampling frequency offset (SFO). It may significantly deteriorate the receiver performance. Besides, the imperfect frequency response of the optical/electrical devices is another factor for the degraded BER performance. In this work, we experimentally investigate the digital interpolation (DI)-based SFO compensation in a short-reach NHS-OFDM transmission system. The orthogonal circulant matrix transform (OCT) precoding technique is employed to equalize the signal-to-noise ratio over data-carrying subcarriers and then improve the BER performance. The experimental results indicate that, with the help of the 4-th order DI, the SFO up to 200 ppm can be well compensated without power penalties in comparison with the SFO-free case. Furthermore, the receiver sensitivity of the NHS-OFDM enabled by OCT precoding can be improved by more than 2 dB at the BER of 1e-3 after 20 km standard single-mode fiber transmission.

与传统的厄米对称光正交频分复用 (NHS-OFDM) 系统相比，非厄米对称光正交频分复用 (NHS-OFDM) 系统在保持相同带宽粒度的情况下表现出更低的硬件实现复杂度和功耗。此外，NHS-OFDM 可以获得类似的峰均功率比以及误码率 (BER) 性能。有望成为下一代无源光网络的新候选者。在异步NHS-OFDM系统中，接收机中模数转换器和发射机中的数模转换器的采样时钟由不同来源产生，其频率总是存在一定程度的偏差，即采样频率偏移（ SFO）。它可能会显着降低接收器的性能。除了，光/电设备的不完美频率响应是降低 BER 性能的另一个因素。在这项工作中，我们通过实验研究了短距离 NHS-OFDM 传输系统中基于数字内插 (DI) 的 SFO 补偿。采用正交循环矩阵变换 (OCT) 预编码技术来均衡承载数据的子载波的信噪比，进而提高误码率性能。实验结果表明，在四阶 DI 的帮助下，与无 SFO 的情况相比，可以很好地补偿高达 200 ppm 的 SFO，而不会产生功率损失。此外，在 20 公里标准单模光纤传输后，在 1e-3 BER 下，通过 OCT 预编码启用的 NHS-OFDM 的接收器灵敏度可以提高 2 dB 以上。