Effect of fiber properties and dispersion management on distortions associated with two subcarriers modulation of laser diode in radio over fiber systems

Abstract

We present numerical modeling and simulation on the effects of standard single-mode fiber (SSMF) properties and different dispersion management approaches on the distortions of laser diode. These distortions are associated with the two-tone modulation of laser diode for use in radio over fiber systems. The fiber properties include attenuation and dispersion. The dispersion management approaches include the use of nonzero dispersion-shifted fiber (NZ-DSF), fiber Brag grating (FBG), and dispersion-compensating fiber (DCF). The laser is directly modulated with two analog frequencies of 25 and 25.1 GHz at different modulation depths (m). The modulated laser signals are then propagated through SSMF at different lengths (L). The investigated laser signal distortions include the 2nd harmonic distortion (HD2), and the 2nd and 3rd intermodulation distortions (IMD2 and IMD3, respectively). The results reveal that all laser distortions are exacerbated as the fiber length increases, which is mainly due to the chromatic dispersion, while fiber attenuation has no effect. The use of dispersion management approaches gives almost similar effects on the reduction of IMD3 when L = 1 km, regardless of the value of m. Up to m = 0.3, DCF is the most effective approach for reducing all distortions over the entire fiber length range, while NZ-DSF is the least. When L = 2 km, FBG is the most effective approach for reducing both IMD2 and HD2 when m ≥ 0.4, whereas when L is increased to 6 km, DCF is the most effective approach up to m = 0.5.Graphical abstractSimulation setup of RoF system for two-tone direct modulation of laser diode using different dispersion management approaches