Resolution model for measurement of optical fibre preforms by focused laser transverse illumination technique

A model has been developed to describe the spatial resolution function of a focussed laser transverse illumination technique for the measurement of the refractive index profile of an optical fibre preform. The resolution function is shown to have similar Gaussian characteristics to that of the sampling beam at the centre plane of the preform, and this has been tested by measurements made on different preforms and with different beam diameters. The results show that the model predicts both the quantitative and qualitative behaviour of the resolution function correctly, which enables the comparison of the resolutions of different preform profiling techniques, as well as assisting in the study of measurement anomalies.