Electrical Modeling of Semiconductor Laser Diode for Heterodyne RoF System Simulation

The increasing use of optoelectronic devices in high data rate communication systems drives the need of precise electrical circuit modeling that allows the study of important parameters on link performances such as nonlinearity and noise level. In 60-GHz band radio over fiber system, the millimeter-wave signal generation offers simple configuration for the base station. Various techniques have been proposed such as optical heterodyning where the frequency difference between two optical carriers mixed in a photodetector generates the desired electrical carrier. Phase noise and linewidth of the optical sources determine the purity of the generated signal. In this paper, the optical phase noise is integrated into an electrical equivalent model of the laser diode to simulate radio over fiber systems in an electrical simulator. The laser output is represented here in the optical field with both intensity and phase noises. The influence of optoelectronic devices on the modulated analog or complex digital signals can be also analyzed. Two uncorrelated laser diodes are used to generate a millimeter-wave signal. Physical parameters of these lasers are determined from static response and relative intensity noise measurements. Phase noise contribution of individual lasers to the millimeter-wave signal is performed and compared with theoretical expectations.