Abstract

Most of the currently used point to point optical transmission systems are based on direct modulation of semiconductor laser diodes. Laser diodes have large modulation bandwidths allowing digital modulation rates in the Gbit/s range. However, transmission using semiconductor lasers is often hindered by the chirp associated with direct modulation. The use of erbium doped fiber amplifiers (EDFAs) can extend the distance of optical transmission considerably, and consequently, the limiting factor can be the dispersion in optical fibers.¹ One way of reducing the penalty associated with transmission in dispersive fibers is to reduce the chirp of the transmitter by using external modulation. External bulk LiNbO₃ modulators have been used successfully to demonstrate substantial improvement² in transmission distances.

© 1994 Optical Society of America