| 摘要 |
An optical fiber grating device 1 is a device in which a long period grating 14 is formed in a core region 11 of an optical fiber 10 consisting of the core region 11 having a refractive index n1 and an outside diameter 2a, a first cladding region 12 surrounding the core region 11 and having a refractive index n2 and an outside diameter 2b, and a second cladding region 13 surrounding the first cladding region 12 and having a refractive index n3 and an outside diameter 2c. There is a magnitude relation of n1>n2>n3 among the refractive index n1 of the core region 11, the refractive index n2 of the first cladding region 12, and the refractive index n3 of the second cladding region 13, a relative refractive index difference DELTAn2 of the first cladding region 12 to the second cladding region 13 is not less than 0.5%, and a thickness (c-b) of the second cladding region 13 with respect to a transmission loss peak wavelength lambd is in a range of not less than lambd nor more than 10lambd.
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