NONLINEAR DISTORTIONS AND COMPENSATIONS OF DFB LASER-DIODE IN AM-VSB LIGHTWAVE CATV APPLICATIONS

The nonlinear distortions of direct modulated laser diode applying to AM-VSB lightwave CATV systems are studied from the viewpoint of rate e quations, A simple method for calculating composite second-order disto rtion (CSO) is proposed, which is denoted as the quasidynamic approach . The attribution of nonlinearity from fiber dispersion and laser chir ping are also concerned. The dependences on the variations of paramete rs of rate equations are intensively investigated to figure out the do minant factor for CSO degradation. This approach explains quite well t he experimental results and gives a clue of constructing the predistor tion circuit with at least 10 dB improvement.