Time-domain model for signal transformation in semiconductor optical amplifiers for bit error rate estimation in communication lines

Subject of study. The study focuses on a fiber-optic communication line incorporating semiconductor optical amplifiers, specifically spontaneous emission and the nonlinear effects in the amplifiers that lead to digital signal transmission errors. Aim of study. The aim of this study was to develop a model of a fiber-optic communication line with integrated semiconductor optical amplifiers, taking into account distortion sources for both weak and strong signals, namely, spontaneous emission and nonlinear effects in the active medium of the amplifiers. Method. The study was conducted using numerical simulations. The model accounted for the propagation of radiation along a 100-km optical fiber span, during which extensive dispersive spreading and absorption occur. The average power of the laser radiation after this span determined the amplifier’s quasi-stationary operating mode, including the power of spontaneous radiation in it. In this operating mode, the transformation of a quadrature-modulated signal within the semiconductor amplifier was calculated. Main results. A numerical model of a fiber-optic communication line with integrated semiconductor optical amplifiers has been developed. This model has been used to analyze information loss in a quadrature-modulated signal; this information loss is attributed to gain dispersion, gain saturation, and spontaneous emission in the active medium of the amplifiers. When the laser pulse duration is 12 ps or longer, the amplifier’s input power dynamic range exceeds 20 dBm (from −37.5dBm to −17.5dBm). Within this range, compensation for amplifier-induced distortion is not required. Practical significance. The results obtained in this study can be used to increase data transmission rates in fiber-optic communication lines over distances ranging from hundreds to thousands of kilometers.