Sensitivity-Improved and Dispersion-Tolerant Lite-Coherent Hybrid Receiver for Digital-Analog Radio-Over-Fiber Mobile Fronthaul

Mobile fronthaul, generally based on fiber-optics, plays a significant role for next-generation radio access network. When addressing fronthaul utilizing intensity modulation direct detection (IM-DD) systems, inherent challenges such as dispersion and low sensitivity pose significant hurdles. Meanwhile, coherent optics, while offering advantages of improved sensitivity, are encumbered by the complexity and prohibitive costs associated with receivers. In this article, we propose sensitivity-improved and dispersion-tolerant optical mobile fronthaul solution based on the lite-coherent hybrid receiver, which adaptively combines the IM-DD and simplified coherent optics at receiver-side. A maximum-ratio combined algorithm is applied in this adaptive receiver. Namely, we demonstrate the maximum-ratio combined lite-coherent hybrid receiver (MRC-LCRX) in the digital-analog radio-over-fiber link. Based on proposed scheme, we experimentally demonstrate in the successful transmission of a 540-Gb/s CPRI-equivalent rate 256-QAM signal over 30-kilometers standard single-mode fiber at −4.8-dBm received optical power. Remarkably, our system demonstrates a significant improvement in sensitivity, outperforming the IM-DD counterpart by 10.4 dB at the 256-QAM EVM threshold. This paradigm, characterized by its cost-effectiveness, elevated sensitivity, and tolerance to dispersion, holds considerable promise for future mobile fronthaul links.