Analysis of magneto-optic nonreciprocal phase shift in asymmetric fibers for all-fiber isolators by variational vector-wave mode-matching method

Magneto-optic nonreciprocal phase shift in fibers with rare-earth doped asymmetric cores is accurately characterized by a variational approach with the required vector fields obtained from the mode-matching method. Implemented in an equivalent transmission-line network, this method can be readily applied to arbitrary channel waveguide structures. Results of the nonreciprocal phase shift for two configurations of magneto-optic asymmetric fibers are presented and the effect is optimized with respects to the structural parameters of fibers. It is shown that an all-fiber isolator could be constructed with fibers with reasonable lengths in an applied magnetic field of 1 kOe.