Transmission characteristics of fiber Bragg gratings written in holey fibers corresponding to air-hole size and their application

Transmission characteristics of fiber Bragg gratings (FBGs) written in holey fibers with different air-hole size are investigated. The cladding mode coupling of FBGs inscribed on holey fibers is remarkably suppressed due to air holes inside of the silica cladding. The wavelength spacing between the main peak due to the core mode coupling and side peak due to the first-order cladding mode coupling increases as the air-hole size increases because the reduction of the effective index of cladding mode depends on the air-hole size within the fiber. The strain and temperature sensitivities of FBGs are also investigated corresponding to air-hole size of holey fibers. The temperature sensitivities of holey-fiber-based FBGs are similar regardless of air-hole size of holey fibers (~1.9%), but their strain sensitivities are enhanced (~28.4%) as the air-hole size increases