Abstract:
The birefringence of an optical fiber resulting from
an asymmetry of the index profile is numerically evaluated using
a finite-element method with a full-vectorial formulation. Such
asymmetric index profiles, assumed to vary exponentially across
the fiber core, could be induced during the writing of fiber Bragg
gratings with UV side-exposure techniques. The results reveal
that the birefringence is a quadratic function of the effective index
change. An asymmetry coefficient near 0.4 m 1 maximizes
the birefringence. The calculated photo-induced birefringence is
negligible if the index change is lower than 5 10 4. However,
the birefringence can reach 5 10 6 for large values of index
change. The numerical method presented could be applied to the
modeling of other asymmetric index profiles.
