Electronic–Photonic Integration of Quasi-Coherent Optical Receivers: Toward Efficient and Scalable Passive Optical Networks

This work presents a monolithically integrated, analog-based quasi-coherent optical receiver, targeting the demands for increased efficiency in next-generation Passive Optical Networks (PONs). The receiver features an optical front-end including light coupling and combining structures, paired with balanced germanium (Ge) waveguide photodetectors. The electrical front-end is based on a common-base shunt-feedback linear transimpedance amplifier (TIA) and a high-speed envelope detector. Facilitated by the electronic-photonic integration, the optical and electrical front-ends are co-optimized, demonstrating a bandpass opto-electrical (O/E) bandwidth of 5–57 GHz with a TIA gain above 74 dBΩ. Performance is reported at a setup-limited bitrate of 25 Gbps, achieving –31.5 dBm receiver sensitivity at a bit error rate (BER) of 1×10−3]. By operating the receiver in single-sideband (SSB) mode, a sensitivity of –19 dBm (BER = 1×10−3) is demonstrated for a 25 km standard single-mode fiber (SSMF) transmission. The reported performance represents an improvement over hybrid quasi-coherent receiver implementations, and validates the proposed receiver as a suitable upgrade to realize the full potential of existing PON deployments.