COMPARISON BETWEEN OPTICAL SCM SYSTEMS USING SEMICONDUCTOR-LASER DIODE OR INTENSITY EXTERNAL MODULATOR AT THE TRANSMITTER

A comparison is presented concerning the use of a semiconductor laser or intensity external modulator at the transmitter of hybrid AM/QAM su bcarrier multiplexed optical transmission systems. In the first case, several effects are considered, which give rise to different distortio n phenomena: intrinsic ''dynamic'' distortions due to the interaction of photons and electrons in a semiconductor laser, clipping impulsive noise, an AM-FM conversion effect due to the joint action of semicondu ctor laser chirping fiber chromatic dispersion, and nonlinear distorti ons due to the Kerr effect. In the case of an external intensity modul ator, the distortion noise due to its intrinsic nonlinear response is analyzed. The analysis provides useful information about the design an d the performance evaluation of SCM-based optical access networks. (C) 1998 John Wiley & Sons, Inc.