Fundamental limitation on large-signal modulation of semiconductor lasers and its implications for lightwave transmission

The performance of single-mode semiconductor lasers under large signal modulation is found to be limited by intraband gain saturation occurring when the on-state output power becomes comparable to the saturation level. The main effect of intraband gain saturation is to increase the fall time associated with the optical pulse. At high bit rates the pulse stretches over several neighbouring bits, thereby affecting the system performance. In the case of 1.55 mu m InGaAsP laser operating at bit rates approximately 10 Gbit/s intraband gain saturation limits the average power in the range approximately 10-20 mW for an acceptable system performance.