Full-duplex WiFi analog signal transmission with digital downlink in a radio-over-fiber system employing RSOA-based WDM-PON architecture

We experimentally demonstrate, for the first time, bidirectional analog WiFi signal transmission in a digital wavelength division multiplexed passive optical network (WDM-PON) system. Our solution is compatible with a single optical feeder fiber and customer premises units employing reflective semiconductor optical amplifiers (RSOAs). The downlink optical carrier is modulated which both baseband 1 Gb/s On-Off-Keying (OOK) data and a WiFi signal in the 2.4 GHz band. The optical signal is split, with part going to reception and part reflected by the RSOA and modulated with an uplink WiFi signal. The uplink WiFi signal is in the 2.4 GHz band (no frequency translation), although the RSOA 3 dB response is limited to 1.2 GHz. At the bit-error-rate (BER) threshold of 2×10^-3 before forward error correction (FEC), we achieve the transmission link up to 20 km (64-QAM), 30 km (16-QAM), and 40 km (QPSK). In all cases, the 1 Gb/s digital downlink signal is error-free.