We present a coherent ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON) with enhanced spectral efficiency. The benefit of using Gaussian or Nyquist pulse-shaping filters at the transmitter is evaluated through numerical simulations and experiments. The transmitters consist of directly phase modulated distributed feedback (DFB) lasers through beat signals whose duty-cycle and amplitude are digitally adjusted. The results show that transmitting a Nyquist-shaped signal achieves a 25% spectral saving allowing to place 2.5 Gb/s/user data in 6.25 GHz channels. Furthermore, the proposed transmitter tolerates differential link-losses of 15 dB at Rx sensitivity of ‒44 dBm at BER=10^‒3 with intradyne detection.

我们提出了一种具有增强频谱效率的相干超密集波分复用无源光网络（UDWDM-PON）。通过数值模拟和实验评估了在发射机处使用高斯或奈奎斯特脉冲整形滤波器的好处。发射器包括直接通过拍频信号进行相位调制的分布式反馈（DFB）激光器，该拍频信号的占空比和幅度都经过数字调整。结果表明，发射奈奎斯特形状的信号可以节省25％的频谱，从而可以在6.25 GHz信道中放置2.5 Gb / s /用户数据。此外，在内部差压检测下，在BER = 10 ^‒3时，Rx灵敏度为‒44 dBm时，建议的发射机在Rx灵敏度为‒44 dBm时可承受15 dB的差分链路损耗。