Radio-over-fiber systems for WLAN based on CMOS-compatible Si-avalanche photodetectors

We demonstrate radio-over-fiber (RoF) systems for IEEE 802.11a wireless local area network (WLAN) using Si avalanche photodetectors (APDs) fabricated in 0.18 μm standard complementary metal-oxide-semiconductor (CMOS) process. In order to achieve high optic-to-electric conversion efficiency and low-noise characteristics, the APD bias voltage is optimized with the evaluation of error vector magnitude (EVM). Downlink data transmission of 20 Mb/s, 16 quadrature amplitude modulation data at 5.805 GHz with a wireless link is successfully performed.