Full-duplex link with a unified optical OFDM signal for wired and millimeter-wave wireless accesses based on direct detection

This paper proposes a full-duplex link with a downlink unified optical orthogonal frequency division multiplexing (OFDM) signal, to support wired and 60 GHz band wireless accesses alternatively based on direct detection. At the optical line terminal (OLT), the downlink unified optical signal is produced via LiNbO3 Mach-Zehnder modulators (MZMs) and an interleaver. At hybrid optical network unit (HONU), it is detected by a high-speed photoelectric diode (PD) to generate a 10 GHz IF-OFDM and a 60 GHz RF-OFDM signals as well as an additional RF clock at 50 GHz. Since the uplink optical carrier is abstracted from downlink, the HONU is free from the light source; and because part of the 50 GHz RF clock is abstracted and used as the wireless uplink local RF carrier, the wireless terminal is free from the RF source. This reduces the system complexity and cost. Moreover, only one tone of the downlink unified optical signal carries the OFDM signal, which makes it suffers little from the fiber chromatic dispersion and laser phase noise. A proof-of-concept full-duplex access link over 25 km fiber is conducted by simulation to demonstrate the feasibility of our proposed scheme and the link performance are assessed.