Distributed gain measurements in Er-doped fibers with high resolution and accuracy using an optical frequency domain reflectometer

For critical Erbium-doped fiber amplifier (EDFA) design, e.g., gain tilt op timization in WDM booster amplifiers, knowledge of the gain distribution wi thin the active fiber can present a valuable information. Among the differe nt techniques to evaluate the distributed gain in active fibers, the techni que of optical frequency domain reflectometry seems most promising as it is a nondestructive measurement method well matched to the task due to its dy namic range, resolution, and range, Moreover, background light from ASE or residual pump light is strongly rejected due to the coherent detection sche me employed. Using different Erbium-doped fibers with strongly varying dopi ng levels and confinements, we demonstrate the excellent accuracy and repro ducibility of the technique.