Design Considerations for Energy Efficient DWDM PAM4 Transceivers Employing Avalanche Photodiodes

Abstract

An effective approach to increase per‐fiber bandwidth is to combine per‐wavelength four‐level pulse amplitude modulation (PAM4) with dense wavelength division multiplexing (DWDM). Silicon photonic transceivers based on microring resonator modulators and drop filters can allow for an efficient realization of this. Utilizing avalanche photodiodes (APDs) in the receiver front‐ends of these transceivers can significantly improve sensitivity, allowing for reduced source laser power and overall improved power efficiency. This paper analyzes the optical‐modulation amplitude (OMA) sensitivity of these APD‐based PAM4 receivers in a silicon photonic DWDM link. A comprehensive link budget is considered that takes into account various system losses and relevant noise sources. Modeling with a developed APD that has a maximum 230 GHz gain‐bandwidth product predicts sensitivity improvements at 32 to 64 Gb s−1 PAM4 ranging from 9.8 to 12 dB relative to a conventional p‐i‐n photodiode. Scaling the APD gain‐bandwidth to 310 GHz allows support of 112 Gb s−1 with −13.2 dBm OMA sensitivity at a BER of 2.4×10−4 with an APD gain of 10. Utilizing the presented architecture, link budget analysis predicts a 9.5x reduction in laser power with APDs and that 38 mW source laser optical power can support a four‐channel DWDM link operating at an aggregate 448 Gb s−1 data rate.

High-speed Si-Ge avalanche photodiodes

“…The link budget and power budget become harder to satisfy while increasing the bandwidth density in optical interconnects. High-sensitivity receivers are required for further increase in bandwidth [40,41]. However, conventional p-i-n photodiodes are challenging to meet the demands in an optical interconnect system.…”