Linear Hybrid Receiver for 400-Gb/λ Intra-Datacenter-Interconnects

Driven by the escalating demand for ultra-high data rates in next-generation data centers (DCs), massive high-speed optical interconnects operating at 400 Gb/s and beyond are highly desired. However, the conventional intensity-modulation with direct detection (IM-DD) solution imposes stringent requirement on the electrical bandwidth due to its 1-dimensional modulation. In this work, we propose and experimentally demonstrate a novel linear hybrid receiver (LHR) scheme for ultra-high-speed subcarrier multiplexed (SCM) signal reception. The LHR reduces the required receiver bandwidth to half that of the transmitter and eliminates the use of additional wavelength-sensitive filters. The inner and outer subcarriers are received by the direct-detection (DD) and the coherent-lite (Coh.) branches, respectively. Moreover, the outer subcarrier can be linearly extracted in the digital domain without signal-signal beating interference (SSBI), leading to power-efficient signal recovery. We first conduct a comprehensive numerical study to investigate various factors affecting the performance of the LHR, including a detailed analysis of two receiver digital signal processing (DSP) configurations, and a comparison of two digital pilot insertion methods. In addition, we experimentally demonstrate subcarrier-multiplexed probabilistic shaping 64-ary quadrature amplitude modulation (PS-64-QAM) signal reception over 500-m standard single-mode fiber (SSMF), achieving a line rate of 416.5 Gb/s with a received optical power (ROP) sensitivity of -3 dBm. This scheme offers a high-speed, cost-efficient, and scalable solution for next-generation data-center interconnect (DCI) Ethernet interfaces beyond 400 Gbps/λ.