A 64-Gb/s 1.4-pJ/b NRZ Optical Receiver Data-Path in 14-nm CMOS FinFET

A 64-Gb/s high-sensitivity non-return to zero receiver (RX) data-path is demonstrated in the 14-nm-bulk FinFET CMOS technology. To achieve high sensitivity, the RX incorporates a transimpedance amplifier whose gain and bandwidth are co-optimized with a 1-tap decision feedback equalization (DFE). The DFE, which operates at quarter-rate, features a look-ahead speculation to relax DFE timing to 4 unit-interval. The analog front end includes a transadmittance transimpedance inductorless variable gain amplifier, resulting in a low power and compact front end. The RX, wirebonded to a discrete GaAs photodiode, achieves an energy efficiency of 1.4 pJ/bit and -5-dBm optical modulation amplitude while recovering PRBS-7 data (bit-error-rate < 10⁻¹²) modulated by a VCSEL driver with a 2-tap feed forward equalization (FFE) (main + precursor) over 7 m of graded-index 50/125-μm multimode fiber. The measured sensitivities at 56 and 32 Gb/s are -9- and -13-dBm optical modulation amplitude, respectively.