420 Gb/s WDM Hybrid FSO-Fiber Communication System Based On Tunable Optical Frequency Comb Sources

A novel tunable optical frequency comb (OFC) source is numerically proposed and demonstrated, for high capacity 420 Gb/s WDM hybrid FSO-fiber communication system. The OFC is constructed based on a cascaded frequency modulator (FM) and a Lithium Niobate Mach-Zehnder modulator (LiNb-MZM). Seven flat comb lines with spacing of 100 GHz are generated within a bandwidth of 0.6 THz. The center wavelength of the generated OFC can be tuned at various wavelengths. 42 channels with a data rate of 10 Gb/s are transmitted by using six OFC sources. The WDM hybrid FSO-fiber system is investigated under three environmental phenomena, such as clear, rain and haze with attenuation losses of 0.2 dB/km, 6.27 dB/km and 20.68 dB/km, respectively. The OFC is tested through the system in terms of BER and Q-factor. At communication condition, the proposed system achieved maximum transmission distances of 9.1 km, 2.2 km and 1 km for environmental phenomena of clear, rain and haze, respectively. These distances are increased with fiber-to-the-home (FTTH) approach, by using a 0.5 km of single mode fiber (SMF) in each channel. The proposed OFC is qualified to use as a source for WDM hybrid FSO-fiber system, due to its simplicity and efficiency.