High-SFDR 100.8km ROF link with optical homodyne detection and genetic-algorithm-assisted digital demodulation

Radio-over-fiber (ROF) link based on phase modulation and coherent detection has been widely proposed for linear transmission. Nowadays, there are increasing demands for long-distance analog radio-frequency (RF) signal transmission, as radars and broadcast systems. In this paper, a high spurious-free-dynamic-range (SFDR) analog coherent ROF link based on optical homodyne detection and genetic-algorithm-assisted digital demodulation is proposed and experimentally investigated. The ROF link is designed for transmitting RF signals ranging from 500 kHz to 100 MHz over a long-distance fiber under the environment of wide temperature. We test the link performance by transmitting different groups of two-tone signals (580 kHz and 600 kHz, 9 MHz and 10 MHz, 49 MHz and 50 MHz, 99 MHz and 100 MHz) over a 100.8-km single-mode fiber (SMF) under the temperature varying from -40°C to 70°C, the shot-noise-limited SFDR of the link are measured to be greater than 122 dB·Hz 2/3 .