Abstract

Erbium-doped fiber amplifiers (EDFAs) are going to be installed in practical communication systems as a postamplifier, an in-line amplifier or a preamplifier owing to their excellent gain and noise performance.^1,2 However, when a conventional EDFA is used in an optical communication system, the optical-domain reflectometry (OTDR) technique—an effective technique widely used to locate breaks and to determine the loss distribution along a fiber—and bidirectional amplification can not be utilized because the isolators used in the EDFA to avoid oscillation block the backscattered (or uplink) light.

© 1992 Optical Society of America