Long-Period Fiber Gratings (LPFGs) which have a periodic structure in the refractive index in the longitudinal direction of the fiber with a period of about 0.5 mm, convert incident light in the fundamental LP01 mode into higher-order LP0m modes through mode coupling. Because the higher-order modes cannot propagate in a single-mode fiber but are lost outside the fiber, an LPFG works as an attenuator. LPFGs with different Bragg wavelengths were fabricated by using the point exposure method in which the period was freely changed. Just after excimer laser light exposure, transmission spectra of LPFGs were measured. Furthermore, compared to the simulation, the higher-order modes of peaks in the transmission spectra of experimentally fabricated LPFGs were identified.
