The induced cladding modes of a superstructure fiber grating

The induced cladding-mode phenomenon in a superstructure fiber grating is experimentally investigated, which is based on the phase matching of both the FBG and LPG wave vectors with the forward core mode. We have demonstrated that when the narrow-band loss peaks created by short periods are located at wide-band loss notches, the strength and central wavelength of induced cladding-modes depend on the loss depth and the left/right sides (positive/negative sides) of wide-band loss notches. This characteristic can obviously be observed in a superstructure fiber grating and may be used for a multi-function fiber sensor.