Optical Switching devices using Nonlinear fiber optic grating coupler

Spectral response of a nonlinear fiber-optic grating is discussed from theoretical and experimental viewpoints of its application to all-optical switch. Fiber Bragg gratings (FBGs) have been used as a key element of add/drop multiplexers that multi-plex/demultiplex signal light with specific wavelengths to/from WDM signals. When high pump laser light is incident on the fiber written with Bragg gratings, optical Kerr effects are induced in the grating region and the spectral characteristics of fiber gratings are modified depending on incident power. The resultant index change of FBG in fiber coupler results in all-optical switching of signal (probe) light by intense pump light. In other words, the optical switch is due to the cross-phase modulation (XPM) that in-tense pump pulse induces on the signal light propagating in the grating of fiber coupler. We successfully fabricated a fiber-optic grating coupler (FGC) and demonstrated the operation of all-optical switches. The effect of polarization state between pump and signal light is also investigated, which is confirmed by the experiment