Multicore optical fiber with a core and a common cladding having a higher refractive index than the core, fiber Bragg grating, and method for manufacturing fiber Bragg grating

摘要

The present embodiment relates to an MCF and the like suitable for fabricating an FBG with improved ripple characteristics. The MCF is mainly composed of silica glass, and comprises a plurality of light guiding structures and a common cladding. Each of the light guiding structures includes a core, a first cladding, and a second cladding. The refractive index of the second cladding is higher than that of the first cladding and is lower than those of the core and the common cladding. Further, at least a part of an inner cladding region, constituted by the first cladding and the second cladding, contains a photosensitive material having photosensitivity of changing a refractive index of a glass region containing the photosensitive material in response to irradiation of light with a specific wavelength.