Abstract

In this work, full-duplex 60GHz DWDM star tree architecture for radio-over-fiber systems is investigated. New approach by using DWDM with the channel spacing of 25 GHz for the first time is proposed to improve the spectral efficiency. The demonstration system consists of 1 central station and 3 base stations as an example. In addition, the remote light source technique is utilized to simplify the architecture of base station (BS) and the external modulation technique is adopted to overcome the fiber chromatic dispersion. Especially, the MZ modulator, configured to generate optical single sideband (OSSB) signal, is adopted in the central station and modulates the optical carrier with the lower sideband (LSB) and upper sideband (USB) subcarriers simultaneously with different data and the EA modulator is adopted in the base station for implementing the maintenance-free BS in the future. The error-free transmission via the 25 km uplink and downlink fiber with the data rate of 155.52 Mbps is performed. The impact of the laser linewidth and the bandwidth of the electrical bandpass filter are investigated. It concludes that the system performance is limited by the laser phase noise for considered DPSK signal and the bandwidth of electrical bandpass filter is much larger than the 3-dB bandwidth. The trade-off has to be made when optimizing the laser linewidth and the bandwidth of the bandpass filter.