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 0.18 μm 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 13 dB to 75 dB. The AGC loop bandwidth is 3.3 GHz, with a power consumption of 101 mW and a low noise current of 1.45 μA, and the eye diagram of the receiver is also good.