Performance investigation of W-band millimeter-wave radio-over-fiber system employing optical heterodyne generation and self-homodyne detection

Abstract

In this paper, a W-band millimeter wave (mm-wave) radio-over-fiber (RoF) system is proposed and investigated. Two different schemes of optical heterodyning techniques are employed, that is the optical double sideband (ODSB) and the optical single sideband (OSSB) schemes. For the first scheme, two laser frequencies are combined and modulated using a 64-quadrature amplitude modulation - orthogonal frequency division multiplexing (64 QAM-OFDM) baseband data through a Mach–Zehnder Modulator (MZM). The two optical frequencies are then transmitted from the central station (CS) to the base station (BS) using a single-mode fiber (SMF). The mm-wave carrier frequency results from the beating of the two laser signals at the photodetector (PD). After the PD, a phase noise-free baseband data can be extracted by self-homodyning the generated mm-wave carrier. In the second scheme, one laser is modulated and combined with the other one after the MZM modulator. In order to mitigate the power fading effect due to possible destructive interference between the two sidebands of the modulated signal, a phase shift of 90°is introduced in the second arm of the MZM to suppress one sideband. The proposed architecture based on optical heterodyne generation and self-homodyne detection can avoid phase/frequency locking, high-speed modulators and local-oscillators at CS and BSs. The simulation results prove that the desired baseband signal can perfectly recovered at the BS. Furthermore, the OSSB scheme can greatly reduce the effect of the fiber chromatic dispersion, and thus extend the transmission distance. An error vector magnitude (EVM) value within the forward error correction (FEC) limit is achieved over 30 km SMF fiber for the ODSB scheme and 50 km for OSSB scheme. The two schemes under consideration can support up to 120 Gbps data rates over long distance. The system has the potential to be compatible with the IMT2020 mobile fronthaul transmission technology.