Inspection of axial stress and refractive index distribution in polarization-maintaining fiber with tomographic methods

An experimental method is given for determination of three-dimensional axial stress distribution in polarization-maintaining optical fibers. The method relies on using phase-shifting digital photoelasticity for gathering several integrated retardation maps for multiple angular position of object and using them as input data for tomographic procedure. The experimental data obtained for panda-type fiber show the regions of high stress in the core and stress member areas of the fiber cladding. The obtained results are in good agreement with the theoretical values known from literature. Also measurement of refractive index distribution in the fiber was done by means of microinterferometric tomography. Interesting correlation between the stress and refractive index distributions is shown and explained.