Abstract

For externally modulated analog lightwave transmitters, chromatic dispersion at 1550 nm in standard fiber has not been considered to be a significant effect for typical transmission distances. This is in contrast to systems using directly modulated laser diodes in which significant CSO (composite-second order) distortion is generated by dispersion interacting with laser frequency chirp[l]. The CSO distortion in the directly modulated case arises from the conversion of the incidental frequency modulation to intensity modulation by the chromatic dispersion. Because most of the cable television (CATV) industry in the U.S. has deployed standard fiber with the dispersion zero at 13 10 nm, commercial CATV transmitters are either directly modulated 13 1 O-nm DFB lasers, extemally modulated 13 1 O solid-state lasers, or externally modulated 1550-nm DFB laser diodes. The CSO distortion for an externally modulated single-mode source is predicted in [l] to be well below the specification for most CATV systems (-65 dBc). Here we consider a transmission system using an externally modulated multimode laser source.

© 1996 Optical Society of America