90 Gb/s NRZ Optical Receiver in Silicon using a Fully-Differential Transimpedance Amplifier

We present the design and implementation of a 90 -Gb/s non-return-to-zero (NRZ) direct detection optical receiver that consists of a low-noise transimpedance amplifier (TIA), fabricated in a 55-nm SiGe BiCMOS technology, and a Ge photodiode integrated into a Silicon Photonic integrated circuit. Low-noise broadband operation is achieved using a fully differential TIA that provides the photodiode reverse bias. 50-, 56-, and 64-Gb/s NRZ operation is demonstrated at bit-error ratios (BERs) below $10^{-12}$ at sensitivities of $-$ 12.3-, $-$ 11.2-, and $-$ 11.1-dBm optical modulation amplitude (OMA) while consuming 128, 141, and 157 mW, respectively. Furthermore, a BER below $10^{-12}$ is achieved at 80 Gb/s with a sensitivity of $-$ 6.1 dBm (OMA) at 165 mW, and operation below KP4-FEC $({2.4 times {10}^{-4}})$ is demonstrated up to 90 Gb/s with a sensitivity of $-$ 7.1 dBm (OMA) while consuming 222 mW. All BERs were measured in real time and without DSP or equalization to compensate the receiver. The presented receiver achieves the best reported sensitivities up to 90 Gb/s, at the second-lowest power consumption, and is the first reported integrated optical RX up to 90 Gb/s that is tested in real time without any equalization or DSP to compensate the receiver. The presented optical receiver is ideally suited for upcoming short-reach applications.