A 60-GHz 4-Gb/s Fully Integrated NRZ-to-QPSK Fiber-Wireless Modulator

A fully integrated optical-to-wireless modulator for low-cost fiber-optical backhaul links is presented in this paper. In the receiver, a CMOS photodetector with a bandwidth of 0.5 GHz is integrated to perform optical-to-electrical conversion. A gain-boosted inverter based transimpedance amplifier achieves a high gain-bandwidth product without using inductive peaking. The two-stage equalizer compensates the photodetector bandwidth and extends the operation data rate to 4 Gb/s. The wireless modulator directly up-converts and modulates the baseband I/Q NRZ data to a QPSK signal centered at 60 GHz. Realized in 65-nm CMOS, the optical front-end achieves -3-dBm optical input sensitivity at 4 Gb/s with 10 -12 BER. The modulator produces -7.2-dBm output power with -12-dB EVM at a bit efficiency of 19.6 pJ/b. This design demonstrates that a small form factor and low cost optical-to-millimeter-wave modulator can be realized to support future fiber-wireless networks.