A 56-GBaud Linear Optical Receiver Hybrid Integrated with InGaAs PIN PDs

This letter presents a 56-GBaud linear optical receiver (ORX) hybrid integrated with InGaAs PIN photodiodes (PDs) and fully-differential SiGe BiCMOS transimpedance amplifier (TIA) for high-speed optical links. The ORX achieves peaking-free transmission from the intrinsic PD current to the TIA input by employing a two-stage transimpedance (TI) topology of a common-base (CB) input stage and a shunt-feedback (SFB) amplification stage. The topology also generates a high-frequency peaking and effectively expands the bandwidth (BW) of the overall ORX despite the large PD capacitance. The optical/electrical (O/E) measurement results show that the proposed ORX achieves 41-GHz -3-dB BW at the maximum gain setting. With the pseudo-random bit sequence (PRBS) length of 2 ³¹ -1, the proposed ORX exhibits -10-dBm optical modulation amplitude (OMA) sensitivity at 1E-6 bit error rate (BER) for 56-Gb/s NRZ transmission, -2.9-dBm OMA sensitivity at 2.4E-4 BER (KP4-FEC) and 4-dBm OMA overload below KP4-FEC for 56-GBaud (112-Gb/s) PAM4 transmission, resulting in an input OMA dynamic range > 6.9 dB. The ORX dissipates 330 mW from a 3.3-V voltage supply and occupies 1.5-mm ² die area.