OPTICAL FIBER GRATING DEVICE

摘要

An optical fiber grating device (1) comprising an optical fiber (10) that ha s a core region (11) having an index of refraction n1 and an outside diameter 2a and having a long-period grating (14), a first clad region (12) surrounding the core region (11) and having an index of refraction n2 and an outside diameter 2b, and a second clad region (13) surrounding the first clad region (12) and having an index of refraction n3 and an outside diameter 2c. The relationship among the indexes of refraction n1, n2, n3 is n1>n2>n3. T he relative refractive-index difference .DELTA.n2 of the first clad region (12) with respect to the second clad region (13) is 0.5 % or more. The thickness (c- b) of the second clad region (13) with respect to the cutoff peak wavelength .lambda. ranges from .lambda. to 10.lambda..