Soliton propagation in twin-core fiber rocking filters

We investigate nonlinear pulse propagation in a twin-core fiber whose birefhingent axes have been periodically rocked at the beat length of the cores. We find that the four coupled-mode equations that describe this system can be reduced to a pair of coupled nonlinear Schrödinger equations under suitable conditions. Consequently we find two new types of compound soliton: one that propagates down both cores of the fiber simultaneously and another that couples completely between the cores of this structure without degradation. These solitons typically have a peak power of ~1 W and a length of ~10 ps.