Abstract

1.48-μm or 0.98-μm laser diode pumped erbium-doped fiber amplifiers (EDFAs) are very important in 1.5-μm optical transmission systems. Compact EDFAs having short EDFs can be constructed by using high erbium concentration EDFs. However, several studies have reported that the gain of high concentration EDFAs falls considerably as the erbium concentration increases [1] due to cooperative upconversion [2], [3], [4] and exited-state absorption at 1.48 μm [5]. Moreover, theoretical studies predict that the noise figure (NF) of the EDFAs increases with Er concentration [2], [3], [4], Unfortunately, no experimental study on the NF increase has been reported to our knowledge.

© 1995 Optical Society of America