Simultaneous Generation of Centralized Lightwaves and Double/Single Sideband Optical Millimeter-Wave Requiring Only Low-Frequency Local Oscillator Signals for Radio-Over-Fiber Systems

We have designed and experimentally demonstrated radio-over-fiber (ROF) systems to simultaneously generate optical millimeter-wave (mm-wave) and centralized lightwaves using one low-bandwidth intensity modulator (IM) with low-frequency local oscillator (LO) signals while simplifying the transmission design and reducing the cost of the base station (BS). The techniques based on double-sideband (DSB) and single-sideband (SSB) signals for ROF systems are discussed in detail in terms of architecture efficiency, bandwidth requirement, and fiber transmission performance. The repetitive frequency of the optical mm-wave carriers are four times of that of the LO in central office (CO) by using DSB scheme. Full-duplex transmission services have been successfully realized over 20-km single-mode fiber (SMF) based on wavelength-reuse technique. In order to mitigate chromatic dispersion, the SSB technique has also been investigated in this paper. We had realized an ROF system that attained dispersion-free transmission and a negative power penalty by using SSB generation. We also quantified the optical carrier-to-sideband ratio (CSR) of downstream transmission in this ROF link and established that the performance of ROF system can be significantly improved when the optical signals are transmitted at a CSR value of 0 dB. The proposed architectures require much less bandwidth of the modulators, receiver sensitivity, system operation efficiency, and reliability.