All-SMF Arrays for Co-Packaged Optics: Optimizing Cost, Complexity and Performance

This work addresses the high cost and complexity associated with polarization-maintaining fiber (PMF) arrays in co-packaged optics systems (CPO), particularly between external laser sources (ELS) and optical transmitters. We propose the use of single-mode fiber (SMF) as a cost-effective alternative to PMF, while maintaining system performance. However, SMFs introduce a drift in state-of-polarization (SOP), which can impair coupling efficiency in polarization-sensitive silicon-photonic integrated circuits. To mitigate this issue, we integrate an active polarization tracking circuit on the SiPh PIC to stabilize the SOP at the OTX input. Experimental results demonstrate the feasibility of this solution, with an analysis of cost, performance, and overhead penalties, suggesting that SMF-based systems with active polarization tracking offer a viable, cost-effective alternative to PMF arrays in CPO systems. Specifically, the packaging cost can be by approximately 2.7 times, while incurring an additional insertion loss of 0.74 dB and an energy efficiency penalty of 0.17 $\text{pJ} / \mathrm{b}$ at $200 ~\text{Gb} / \mathrm{s}$ with comparable baseline.