An optical receiver with automatic gain control for radio-over-fiber system

An optical receiver circuit with automatic gain control (AGC) for radio-over-fiber (RoF) system is presented. The AGC optical receiver is designed on the standard 0.18µm CMOS technology. The proposed circuit uses a differential variable gain amplifier (VGA), implemented by a Gilbert cell and provides an exponential function circuit for the dB linearity of the gain voltage. A large dynamic range of the receiver is from 13dB to 75dB. The AGC loop bandwidth is 3.3GHz, with a power consumption of 101mW and a low noise current of 1.45µA, and the eye diagram of the receiver is also good.