Characteristics of magneto-optic fiber Bragg gratings for use in optical signal processing

The characteristics of photonic bandgaps and the transmission/reflection of guided optical waves in the magneto-optic fiber Bragg grating (MFBG) are theoretically investigated for the first time. The polarization-mode conversion resulting from the Faraday effect may change the width of the pure bandgap, or even lead to a couple of photonic semitransparent frequency band (STB) for sufficiently large magneto-optical-to-grating coupling ratio (MGR). Within the STBs, the transmittivity and reflectivity are equal and then the MFBG can serve as a 3 dB light beam splitter. Based on the sensitivity of MFBG spectral lines to the magneto-optic (MO) coupling coefficient, a novel high-resolution magnetic field sensor capable of up to 0.01 nm/(kA/m) is predicted. According to the dependency of nonlinear transmission or reflection on the MO effects, a new class of MFBG-based nonlinear optical switches under an appropriate MO bias may also be achieved with applications to flexible and controllable optical signal processing.