A 4 × 50 Gb/s 2.9-pJ/b NRZ VCSEL-Based Co-Packaged Optical Link With Fiber Termination

A four-channel vertical cavity surface-emitting laser (VCSEL)-based co-packaged optical (CPO) transceiver (TRX) is demonstrated, integrating a photodiode (PD) array, a trans-impedance amplifier front-end integrated circuit (TIA-FE IC), an electrical receiver (RX) IC, and optical fiber termination on a single package on the receive side. The transmitter (TX) counterpart incorporates a VCSEL array, a VCSEL driver IC, and an electrical TX IC, all on a single package. To mitigate the group delay (GD) distortion caused by packaging parasitics, an input matching network is introduced in the TIA-FE IC. Several bandwidth extension techniques are employed, along with a two-tap Cherry–Hooper-based FIR feedforward equalizer (FFE) in the electrical RX IC, to compensate for inter-symbol interference (ISI) and a low-noise double-tail latch. When modulated by its VCSEL-based optical TX counterpart, the RX achieves an aggregate four-channel data rate of 200 Gb/s non-return-to-zero (NRZ) at 1.5 pJ/b, with a bit error rate of less than $10^{-12}$ and a sensitivity of −6 dBm.