Flexible TWDM-RoF system with good dispersion tolerance for downlink and uplink based on additional SCS.

A high-efficiency full-duplex radio-over-fiber (RoF) system incorporating time- and wavelength-division multiplexing technology is proposed in this paper, which is more flexible for the wavelength assignment based on an additional subcentral station (SCS). The periodic power fading effect resulting from a radio frequency signal transmitted over an optical fiber is effectively eliminated for the downlink and uplink. Colorless base stations are achieved by a centralized allocation strategy of upstream light sources. At the SCS, an optical cross-connect unit is employed to enhance the utilization of light sources and the flexibility of the proposed RoF system. Simultaneously, the requirements of high-bandwidth modulators and photodetectors are significantly reduced with a centralized optical carrier suppressed modulation and an all-optical frequency downconversion at the SCS. On the basis of the additional SCS, a 26 GHz full-duplex experiment system is demonstrated, and two 1.25 Gbps baseband data signals for downlink and uplink are successfully transmitted over a 40 km standard single-mode fiber.