Patent ID: 6487340
Filing Date: 2002-11-26
Classification: G02B

Abstract:
An optical fiber grating element, comprising:a multi-mode optical fiber having a cutoff wavelength regarding LP02-mode light on the longer wavelength side than a wavelength band in use, said multi-mode optical fiber having a first core region of a refractive index n1 extending along a predetermined axis, a second core region provided on a periphery of said first core region and having a refractive index n2 lower than that of said first core region, and a cladding region provided on a periphery of said second core region and having a refractive index n3 lower than that of said second core region; and a grating provided in a predetermined region of said first core region and selectively coupling fundamental LP01-mode light of a predetermined wavelength within the wavelength band in use to LP0m (m&gE;2)-mode light, wherein said optical fiber grating element satisfies the following relation: n1>Neff01>n2>Neff0m>n3 where Neff01 is an effective refractive index with respect to the fundamental LP01-mode light and Neff0m an effective refractive index with respect to the LP0m (m&gE;2)-mode light.