We present a selective mode-launching technique to determine the confinement of erbium in optical fibers. The loss per meter, αlm, of the individual LPlm modes (LP01 and LP11 at 980 nm) is measured, and the ratio γ = α01/α11 is related to the concentration of erbium in the core. We assume a Gaussian diffusion profile for erbium and relate the dependence of γ on erbium confinement by using exact mode profiles. This technique uses only two sets of measurements and is independent of erbium concentration.
© 1992 Optical Society of America
Ashish M. Vengsarkar, David J. DiGiovanni, W. A. Reed, K. W. Quoi, and K. L. Walker, "Measurement of erbium confinement in optical fibers: a differential mode-launching technique," Opt. Lett. 17, 1277-1279 (1992)