LONG PERIOD OPTICAL FIBER GRATING FILTER DEVICE

摘要

There is provided a long period optical fiber grating filter device. Th e long period optical fiber grating filter device includes a core having long period optical fiber gratings formed therein at every predetermined periods, a cladding surrounding the core, a coating covering a cladding portion free from the lo ng period optical fiber gratings, a recoating covering a cladding portion havin g the long period optical fiber gratings, a core/cladding refractive index changin g portion where a coupling wavelength has a negative wavelength shift range wi th respect to a temperature change according to the amount of a dopant added to the core, and a cladding/recoating refractive index changing portion where a refractive index decreases at an increased temperature and a coupling wavelength logs a positive wavelength shift range. Therefore, the core shows a negative coupling wavelength shift by the amount of a positive coupling wavelength shift in the recoating material the refractive index of which decreases at an increased temperature.