Real-Time Generation and Reception of OFDM Signals for $x$-Band RoF Uplink with Heterodyne Detection

A field-programmable gate arrays-based real-time orthogonal frequency-division multiplexing (OFDM) transceiver is implemented for the uplink of an $X$-band radio-over-fiber (RoF) system with heterodyne detection for the first time. Digital intermediate-frequency $I/Q$ modulation and demodulation, and forward error correction are applied. Minn's timing synchronization method is slightly modified with reduced implementation complexity for the proposed OFDM-RoF system. By using Reed-Solomon code with symbol interleaving technique, the real-time transmission of the $X$-band 16-ary quadrature amplitude modulation OFDM-RoF signal over 10-m wireless and 2.26-km single mode fiber link is successfully achieved with a post-FEC bit error rate below $1\times 10^{-9}$.