A Compact 112-Gbaud PAM-4 Silicon Photonics Transceiver for Short-Reach Interconnects

For next generation highly integrated transceivers, silicon photonics (SiP) has attracted widespread interest in using mature CMOS production processes to manufacture high-yield, low-cost photonic integrated circuits (PIC) with the potential for integration with CMOS electronics. SiP now routinely integrate GeSi electroabsorption modulators (EAM) and GeSi waveguide photodiodes which have high responsivity and possess 3-dB electro-optic bandwidth of over 65 GHz. Their ultra-compact dimensions make it possible for multi-channel transceivers to be realized on a small chip area. In this paper, we demonstrate the high-speed capability of these devices incorporated with optimized digital signal processing (DSP) for 100 Gbaud+ PAM-4 signaling. Using integrated GeSi-EAM and GeSi-photodiode fabricated at a commercial foundry, we carried out intensity modulation and direct detection (IM-DD) transmission experiments in C-band using PAM-4, for both back-to-back and SSMF transmission at 1 km and 1.5 km. Under a 6-dB system bandwidth of ~43GHz we attained, with the help of DSP equalization, a record 112 Gbaud (224 Gb/s), 108 Gbaud (216 Gb/s) and 100 Gbaud (200 Gb/s) are achieved over back-to-back, 1 km and 1.5 km SSMF transmission respectively, with a bit-error-rate (BER) below the hard-decision forward-error-correction (HD-FEC) threshold of 3.8E-3.