Progress in Erbium Doped Fiber Amplifiers,

Erbium fiber amplifiers are entering a fourth year of development with six commercial offerings now available, the result of rapid improvements in pump lasers, wavelength division multiplexers, isolators and doped fiber designs. A number of challenges remain however to improve the performance and ensure reliability in field applications. Improvements in the rare earth doped fiber, itself, remain a challenge. Rare earth doped fiber fabrication has been dominated by variations on traditional low loss telecommunications fiber using GeO 2, Al 2 0 3, and P 2 0 5 co- dopants yielding fiber which is fusion splice compatible with telecommunications fiber 1. It has long been realized that alternate host compositions may improve the efficiency and gain-bandwidth products at the expense of compatibility with telecommunications fiber. Host materials of compound glasses, phosphates, fluorophosphates and others have recently been reported 2,3,4,5. The incorporation of Ca in a GO2-Al2O3-SiO2 or Al 2 0 3 -SiO 2 host has, for example, also been shown to improve the efficiency of 813 nm pumping 3.