Optimum parameters controlling distortion and noise of semiconductor laser under analog multichannel modulation

Abstract

This paper presents a comprehensive modelling and simulation study on the optimum parameters that control the distortion and noise of semiconductor lasers (SLs) subject to multichannel modulation for use in analog cable television (CATV) fibre links. The study is based on numerical integration of the rate equation model of the semiconductor laser. The parameters comprise the modulation index per channel (m / ch), number of loaded channels (N) and fibre length $$(L_{F})$$ . The signal distortions include the composite second-order (CSO) and composite triple beat (CTB) distortions. The noise is assessed in terms of the relative intensity noise (RIN) and carrier-to-noise ratio (CNR). In order to achieve acceptable CNR values for SL, m / ch should be less than 7.5 and 2% when loading 12 and 80 channels, respectively. For the CATV fibre link with $$L_{F} = 10 \hbox { km}$$ , the increase in the number of channels from 12 to 80 corresponds to lowering the optimum value of m / ch from 7 to 1%. The increase of $$L_{F}$$ to 50 km limits the optimum value of m / ch between 1.4 and 1%, which corresponds to loading between 12 and 17 channels only.