The dependence of carrier lifetime on spectral width in multimode semiconductor lasers

Comprehensive measurements of the dependence of the carrier lifetime, eye pattern, and power penalty on the spectral width in multimode semiconductor lasers for a gigabit lightwave transmission system are presented. The results show that the carrier lifetime, eye pattern, and power penalty caused by mode partition noise (MPN) are strongly dependent on the source spectral width. The lasers with shorter carrier lifetimes exhibit a narrow spectral width, and hence show less MPN, a better eye opening, and a lower power penalty. A theoretical calculation of the MPN-induced power penalty is in good agreement with the measured system penalties. The likely cause for narrow spectral width with shorter carrier lifetime of the lasers is due to the smaller linewidth enhancement factor a caused by a higher doping concentration in the lasers.