Abstract

Narrow linewidths of semiconductor laser transmitters may be achieved either with AR-coated laser diodes with a large feedback from a relatively short external cavity or with uncoated lasers with long external cavities and low feedback levels. Both approaches yield linewidths of below 100 kHz. Especially the second approach is very easy to realize when using an external fiber resonator with a fiber grating.¹ It will be shown to what extent such an approach is useful for differential phase shift-keying (DPSK) systems.

© 1987 Optical Society of America