Abstract

Increasing demand has caused substantial interest in high bit rate (> 5 Gbit/s) telephony systems, as reflected in emerging use of dispersion-shifted fibers for 1550 nm transmission in new system installations. However, the upgrading of existing standard single-mode 1310 nm optimized optical fiber routes to higher capacities is also of great concern to long-haul telecommunication providers with large embedded fiber systems. Ideally, the upgrade method would provide for both increased data rates and longer span capability, so that the existing fiber could carry more data with a minimum amount of new equipment. In the 1550 nm wavelength window, erbium-doped fiber amplifiers (EDFAs) can reduce loss limitations. Unfortunately, for typical silica step-index fibers, chromatic dispersion has limited production-grade intensity modulated direct detection (IMDD) transmission systems to, for example, about 100 km between regeneration sites at 2.5 Gbit/s, resulting in a bit-rate-distance product of 250 Gbit-km/s.

© 1992 Optical Society of America