Studies The Effects Of Electrical Parasitics On Modulation Characteristics Of Semiconductor Lasers

Compared with external modulated semiconductor lasers, directly modulated lasers(DML) are smaller, lower power consumption and less device complexity. They are widely used in short-distance fiber-optic communication systems such as optical access networks and optical interconnection. With the increase of data traffic, in order to meet the demand of next-generation optical access networks, it has become a research focus in the semiconductor laser technology to achieve high-speed DML. In recent years, with the rapid development of chip manufacturing technology, the intrinsic response rate of semiconductor lasers has been greatly improved, while the electrical parasitics introduced during packaging has become an important factor affecting the modulation rate. In this paper, effects of electrical parasitics on modulation characteristics of semiconductor lasers are investigated both in theory and experiment. The main contents are organized as follows:(1) According to the equivalent circuit model, electrical parasitics and driving circuits can easily be included into the laser models to achieve a more realistic simulation in ADS software. The simulation results show that there is a potential 3d B bandwidth limit point caused by parasitic circuit. If the parasitic effects can not be improved, the laser modulation rate is difficult to be enhanced by the high-speed chip design. Sometimes the performance of the lasers may even be improved by optimizing the design of the drive circuit.(2) By combining an equivalent circuit laser model and a transmission-line laser model(TLLM), both the electrical parasitics and the inhomogeneous effects of the laser can be simulated.(3) A technique is described for readily extracting values of the rate equation parameters using measurements of the P-I characteristics and intensity response of the laser and the transmission characteristic of a dispersion fiber. After that, we used ADS software to extract the parasitic parameters from the scattering parameters with optimization fitting method.