Challenges and Advances of SDM-PON

This paper presents the advances and challenges of design, integration, and performance evaluation of a space-division multiplexing passive optical network (SDM-PON) system based on newly developed 7-core weakly-coupled multicore fiber (WC-MCF). A long-wavelength vertical cavity surface emitting laser (VCSEL) array, customized for O-band operation, was developed and experimentally characterized. To address optical alignment challenges, both expanded beam coupling and adaptive coupling using spatial light modulators were examined. Meanwhile, experimental results under low-crosstalk conditions demonstrated that simplified single-input-single-output (SISO) digital signal processing (DSP) offers comparable performance to multiple-input-multiple-output (MIMO) DSP in the proposed SDM transmission system, enabling reduced complexity and power consumption. Our proposed SDM-PON architecture also delivers performance comparable to standard single-mode fiber (SMF) configurations, with the potential for increased capacity and reduced fiber deployment costs. The scope is then broadened to investigate the scalability of general WC-MCF-based SDM links toward higher core counts. The study also mentioned key design trade-offs and technical challenges at the device and system levels, including limitations in VCSEL bandwidth, coupling efficiency and laser chirp. Overall, the proposed SDM-PON architecture demonstrates strong potential for cost-effective and energy-efficient deployment in future access networks.