DETERMINATION OF MONOMODE FIBER BUFFER PROPERTIES

Observations of oscillations in bending loss as a function of illumina ting wavelength in monomode optical fibers are presented. A model is d eveloped based on the interference between the core-guided mode, and a ''whispering gallery'' (WG) mode established by reflection at the buf fer-air interface. It is shown that the relative phase of the modes is a function of the dimensions and refractive index of the buffer coati ng. The phase is determined in experiments where the bend radius and w avelength of illumination are varied, allowing the buffer diameter and refractive index to be determined by a best fit to experimental data. The practicality of this method for the characterisation of buffer pr operties is discussed.