Bi-Directional 25G/50G TDM-PON With Extended Power Budget Using 25G APD and Coherent Detection

In this paper, we experimentally report on cost-effective asymmetric high serial rate time-division-multiplexed passive optical networks (TDM-PON) with single carrier 25-Gb/s upstream and 50-Gb/s downstream. The 50-Gb/s downstream is based on duobinary detection using a commercial 25G APD-based receiver. To increase the power budget for the 25-Gb/s upstream, we employed a simplified coherent detection scheme at the optical line termination. The coherent detection scheme is based on a simple 3 × 3 fiber splitter and detection of a nonreturn-to-zero on-off-keyed signal. No complex digital signal processing is required and there is no need for phase and frequency locking of the local oscillator. For the upstream, we achieved a receiver sensitivity of -35 dBm at 25G, enabling a 40-dB optical power budget. Burst mode operation in the context of TDM-PON was also demonstrated. The system is, therefore, compatible with commonly deployed high-loss power splitting TDM-PON.