Soliton switch using birefringent optical fibers

The use of solitons is proposed for interferometric switching in birefringent optical fibers. Pulse propagation in the fiber is modeled by the coupled nonlinear Schrödinger equation, in which the ratio between the self-coupling and cross-coupling terms depends on the ellipticity of the fiber eigenmodes. It is shown that shadows occur unless the self-coupling and the cross-coupling are equal and that these shadows seriously affect the contrast ratio attainable by a switch. These two couplings become equal at an ellipticity angle θ ≈ 35°, and, within a tolerance of θ = ± 5°, a contrast ratio of 10 or more can be achieved.