Simulation of distortion in multi-carrier subcarrier multiplexed optical communication systems employing direct intensity modulation of semiconductor lasers

Abstract

Direct intensity modulation of semiconductor lasers in subcarrier multiplexed (SCM) optical fibre communication systems is of interest because of its simplicity and the possibility of integration of the drive electronics with the laser diode. Direct modulation also produces distortion which degrades system performance. In this paper, we extend a static numerical simulation method for multi-carrier SCM systems to a dynamic simulation employing rate equations. We first show that the results of our simulation agree with analytical results for multi-carrier SCM systems obtained from perturbation theory in the absence of optical reflection into the semiconductor laser. We proceed with the calculation of distortion in the presence of weak reflections. We show that the distortion is lower than what is expected from previous analytical considerations for two subcarriers. Our simulation can also take into account the effect of overmodulation in a dynamic manner. However, our simulation does not take into account the distortion due to device imperfections.