Determination of monomode fiber buffer properties from bend-loss measurements

Bend loss in monomode optical fibers exhibits oscillations as a function of wavelength due to a whispering gallery mode. The period of these oscillations has been used to measure the mean refractive index and thickness of the buffer material on two optical fibers in situ. The mean refractive index of the buffer material was measured to an accuracy of ±0.0025, which is sufficient to distinguish two nominally identical fibers with buffer surface cures of 86% and 96%.