DC-Coupled Stacked-Differential Optical Receiver for IM-DD

Differential sensing in intensity modulation/direct detection (IM-DD) theoretically offers sensitivity advantages. However, the need for reverse bias restricts photodiodes (PD) to AC coupling with differential TIAs, causing noise, bandwidth degradation, and baseline wander, compromising the advantage of differential sensing. This paper introduces the CMOS stacked-differential optical receiver architecture that employs DC coupling to connect the PD cathode and anode, enabling differential signal reception and reverse bias without AC coupling’s drawbacks. Fabricated in a standard 180-nm CMOS process and coupled with a PIN PD, the receiver achieves a differential-mode OMA sensitivity of -18.5 dBm. Comparative single-ended measurements were also performed, demonstrating a 1.3 dB sensitivity advantage from differential signaling which closely aligns with theoretical predictions. Operating at a 3.3 V power supply voltage compatible with optical devices, the receiver consumes 89.1 mW, with 86.5 mW utilized by the signal channels, resulting in a power efficiency of 97%.