Abstract

The gain compression factor e is one of fundamental parameters of semiconductor lasers, which is phenomenologically introduced in the frame of the rate equations taking account of the gain saturation effects such as the spectral hole burning and the carrier heating.¹ Because the gain saturation effect determines the performance of the high bit-rate optical communication system, it is important to measure the e-value of semiconductor lasers. In this letter, we propose a novel method for determining the e-value of semiconductor lasers by observing only pulse spectra under the gain-switching (pulse oscillation) condition. The proposed method is based on the pulseshape distortion occurring in proportion with increasing the modulation amplitude. If the gain saturation is negligible under the gain-switching condition, the pulseshape always maintains the sech²-type.² On the contrary, when the gain saturation exists in the laser, the oscillation pulse has a long lasting tail part and this distortion becomes remarkable with increasing the modulation amplitude. Thus, the gain saturation effect apparently influences the pulseshape. Therefore, it is understood that the e-value can be related to the pulseshape distortion.

© 1995 IEEE