Fabry-Perot resonator composed of a photoinduced birefringent fiber grating

The periodic mode coupling between the x- and y-polarization modes that is induced by a photoinduced birefringent fiber grating is analyzed through the use of the coupled-mode theory. A novel Fabry-Perot resonator composed of a photoinduced birefringent fiber grating is proposed and theoretically investigated. In the ideal case, the x- and y-polarization resonances of the resonator coincide with each other because of the polarization power exchange by the photoinduced birefringent grating, which results in the total resonator output's being polarization independent. However, if there are some external perturbations (e.g., temperature change or strain), the phase matching is detuned, which could destroy the coincidence between the two polarization resonances, which can further result in the total output resonance's having two peaks. The separation between these two resonant peaks depends on perturbations of the environment (temperature changes or strain).