High-Capacity IM-DD Transmission in O-Band Using Advanced Maximum Likelihood Sequence Estimation Methods

We propose advanced maximum likelihood sequence estimation (MLSE) methods for increasing the capacity of short-reach intensity-modulated direct detection (IM-DD) transmissions for economically realizing next generation Ethernet such as 800 GbE or 1.6 TbE. It is particularly important to conquer the traffic growth in data center networks, which has become a major issue. In this article, we introduce a method for reducing the complexity of the Viterbi algorithm, which is a problem in the actual implementation of MLSE, by using a penalty-less truncated trellis diagram with temporal decision results. Next, we introduce a method for improving the demodulation performance by precisely emulating the nonlinear response of the transmission system with low-cost devices using a nonlinear filter. Finally, we introduce a method for reducing the computational complexity with a decision feedback function. Transmission experiments in the O-band with transmission rates of 200 Gbps/lane or higher using each of the proposed methods are also presented. Finally, we present a 200 Gbps/lane 4-LAN-WDM 800 G 2 km transmission experiment using a 4-channel LAN-WDM TOSA designed for 400 G transmission.