| 摘要 |
<p>An optical fiber grating element, production method thereof, and optical fiber filter containing the element. The optical fiber grating element comprises a first core region with a refractive index of n1, a second core with a refractive index of n2, provided on the outer periphery of the first core region, and a clad region with a refractive index of n3, provided on the outer periphery of the second core; and contains a multi-mode optical fiber having a cutoff wavelength of an LP02 mode light on a longer wavelength side of a using wavelength band. In a specified area in the first core region, a long-frequency grating for coupling selectively a ground LP01 mode light having a specified wavelength within the using wavelength band with LP0m (m≥2) mode light is provided. The optical fiber grating element satisfies a relation, n1>Neff01>n2>Neff0m⊃n3, where effective refractive index of ground LP01 mode light is Neff01, and effective refractive index of LP0m (m≥2) mode light Neff0m.</p> |
