An 8Gbps Adaptive Receiver for RF over FSO in 28nm CMOS

This paper presents a fully integrated high-bandwidth receiver for RF-over-free-space optics (RoFSO). Using subcarrier intensity modulation (SIM) and direct detection scheme, high data rate optical communication is supported in a high-loss atmospheric channel. For proof-of-concept demonstration, an 8Gbps input data via differential phase shift keying (DPSK) modulation and with 10GHz of RF bandwidth is employed. The link performance is assessed by exposing the system to more than 26dB of optical loss equivalent to 3.5km of free space distance under moderate visibility conditions. The receiver chip uses adaptive control loops to compensate for the atmospheric effects and extends the dynamic range. It has been designed and implemented in 28nm CMOS process and achieves 58dB of gain and 18GHz of bandwidth.