Analysis of a rectangular waveguide isolator

Isolator conditions are derived for a rectangular waveguide in which magneto-optical and anisotropic dielectric crystals are integrated for reciprocal and nonreciprocal
E^{x}-E^{y}
mode conversion functions, respectively. Relations between structural parameters are derived by perturbation analysis, and design examples of single-mode isolators with 3.6-, 4.6-, and 6.6-μm square cores are given at the 1.55-μm wavelength. Tolerances in the structural parameter deviations are investigated analytically and numerically. Isolation of more than 20 dB is feasible without any parameter adjustment even when there is a 9- percent deviation in the core dimension.