Adiabatic breakdown in a fiber ring resonator

I consider a topological transition resulting in an abrupt change by pi of the geometric (Berry's) phase occurring in an optical modulator based on a fiber ring resonator. The topological transition, induced by modifying the birefringence along the ring, manifests itself in a narrow resonance in the transmission of the optical modulator. Contrary to the adiabatic case, the condition of critical coupling is not essential to obtain deep modulation of the transmission. Moreover, broadening of the resonance due to the finite linewidth of the optical input is also discussed. (c) 2006 Optical Society of America.