Saunders M J, Gardner W B
Appl Opt. 1977 Sep 1;16(9):2368-71. doi: 10.1364/AO.16.002368.
It is shown that interferograms generated by passing light perpendicular to the axis of a fiber can be used to obtain the maximum refractive index difference and the index profile shape to better than +/-10% accuracy in regions of the core where alpha is constant. This technique avoids the time consuming sample preparation required for the slab method, the propagation problems associated with the near-field technique, and the surface quality problem associated with the reflection technique.
