In-band full-duplex multiband mobile fronthaul network based on analog radio-over-fiber and tandem SSB modulation

An in-band full-duplex multiband mobile fronthaul network is proposed based on analog radio-over-fiber and tandem single-sideband (TSSB) modulation. Two optical carriers with a wavelength spacing of 50 GHz in accordance with international telecommunication union dense wavelength division multiplexing (DWDM) standards are employed in each distributed unit (DU): one is used to carry two different radio frequency (RF) vector signals at 3 and 10 GHz, while the other is used to carry a vector signal at 15 GHz and a single-tone signal at 15 GHz. At the DU, a parallel TSSB modulation is applied, which eliminates the cross talk of TSSB modulation through two dual-polarization binary phase-shift keying (DP-BPSK) modulators. This allows the two vector signals carrying different data to be distributed on both sides of the optical carrier. At the active antenna unit (AAU), different RF vector signals centered at 3, 30, and 60 GHz, each carrying distinct information, can be generated by selecting either one DWDM channel or two adjacent DWDM channels in a group. By utilizing the spacing between the two DWDM optical carriers, millimeter-wave signals can be generated without the need for additional electronic upconversion devices in the AAU. In the uplink, a DP-BPSK modulator is used to receive the signal of interest while canceling self-interference. Simulation results demonstrate the performance of the proposed system. After transmitting 25 km through single-mode fiber and compensating for dispersion using corresponding dispersion-compensating fiber, the downlink and uplink achieve error vector magnitudes of less than 9% and 2%, respectively, when the receiving optical power is 6 dBm.