MODELING HIGH-SPEED OPTICAL-TRANSMISSION SYSTEMS

Computer simulation of a 2.5 Gb/s intensity modulated/direct detected (IM/DD) optical system with high path dispersion is described. This simulation, based on single-mode laser diode rate equations, includes transmit and receiver circuit filtering, receiver circuit noise, APD noise, fiber dispersion, and laser chirp. The rate equations are sufficiently general to model mode-offset DFB laser diodes. The system power penalty, due to laser chirp and fiber dispersion, is calculated using Gaussian quadrature numerical integration. By simulating a population of some 12800 laser diodes and correlating the performance of each laser in a transmission system with its spectral characteristics, it is possible to deduce laser specifications that will assure satisfactory operation in long-span links. These results are used to study a laser diode specification under consideration by CCITT and, by studying the simulated laser line shapes, some modifications to the CCITT specification are considered.