Fujikura Limited

Masaaki Sudo

Satoshi Okude

Akira Sakamoto

Kenji Nishide

Tomosada Inada

Atuhiko Niwa

Reiko Kojima

Photosensitivity of an inner core which is disposed in a central portion of a core is low. Photosensitivity of an outer core which is disposed close to a cladding is high. In the cladding, photosensitivity of the inner cladding which is close to the core is high and photosensitivity of an outer cladding which is outside of the inner cladding is low. A plurality of slant optical fiber grating having different optical characteristics by using the optical fiber having such photosensitivity so as to form a gain equalizing optical filter. By doing this, it is possible to provide an optical filter having a slant optical fiber grating which can maintain a filtering characteristics in a narrow bandwidth and enlarge loss area.

Optical fiber, slanted optical fiber grating, band rejection optical filter, gain equalizing optical filter for optical amplifier, and optical amplifier module

There is provided a slant short-period grating which is obtainable by irradiating light onto an optical fiber whose core is formed from quartz glass to which has been doped a photosensitive dopant that changes a refractive index of the quartz glass by light irradiation, and whose clad has one or two or more layers with at least the layer that is adjacent to the core being a photosensitive layer formed from quartz glass to which has been doped a photosensitive dopant that changes a refractive index of the quartz glass by light irradiation. In this slant short-period grating a grating portion is formed by changing the refractive index of the photosensitive layer of the clad and the core at a predetermined grating period along a longitudinal direction of the optical fiber by a predetermined slant angle. The diameter of the core is set to 5 &mgr;m or more, and the relative photosensitivity ratio of the core relative to the photosensitive layer of the clad that is adjacent to the core is designed so as to satisfy a predetermined formula. As a result, in the wavelength spectrum of transmitted light, loss peaks are obtained in a narrow frequency band.

Slant short-period grating

Growing community of inventors

Sakura, Japan

Masaaki Sudo