Real-Time Q-Band OFDM-RoF Systems With Optical Heterodyning and Envelope Detection for Downlink Transmission

We experimentally demonstrate a real-time optical heterodyning and envelope detection-enabled orthogonal frequency-division-multiplexing-based Q-band radio-over-fiber (OFDM-RoF) system. Envelope-detector-based down-conversion is applied to the mobile terminal (MT), which makes MT insensitive to the phase noise of the beating millimeter wave signal and enables the generation of RoF signals using two free-running non-narrow line-width distributed feedback lasers in the central office. The error-free transmission real-time Reed-Solomon- coded 16-quadrature-amplitude modulation(16-QAM)-OFDM-RoF signals with a net bit rate of 1.2 Gb/s at 35/40 GHz over 4.5-km single-mode fiber (SMF) and 0.8-m wireless distance is reported in this paper. Additionally, the transmission performance of the signals at 35 GHz with the net bit rate from 1.5 to 5.9 Gb/s is also investigated by offline digital signal processing approaches. It indicates that the BER of the signal with the net rate up to 4.4 Gb/s after the SMF and wireless link transmission is below a 7% hard-decision forward error correction (FEC) threshold of 3.8 × 10
^-3
.