EXPERIMENTAL INVESTIGATION OF THE GAIN FLATNESS CHARACTERISTICS FOR 1.55 MU-M ERBIUM-DOPED FLUORIDE FIBER AMPLIFIERS

The flat gain over a broad spectral width offered by fluoride-based Er bium-Doped Fiber Amplifiers (EDFA) appears very attractive for wavelen gth-multiplex systems operating near 1550 nm. The relevant parameters (input pump and signal powers, fiber length) that determine the gain f latness characteristics of fluoride-based EDFA have been experimentall y investigated. It is found that flat gain operation requires an optim al, though not critical, population inversion within the doped fiber, which is somewhat lower than the maximum population inversion achievab le with 1.48 mum-pumping. Implications on the design and operating con ditions of fluoride-based EDFA are discussed.