Fujikura Limited

Kenji Nishide

Ryozo Yamauchi

Shigefumi Yamasaki

Kensuke Shima

Tetsuya Sakai

Akira Wada

Ryokichi Matsumoto

Satoshi Okude

Hideki Sasaki

Nobuyuki Tanaka

Fumio Suzuki

Michihiro Nakai

Akira Sakamoto

Takeshi Yamada

Hiroyuki Taya

Mikio Yoshinuma

Hiroshi Hidaka

Yuu Ishii

Tomosada Inada

Masaaki Sudo

Reiko Kojima

Yoji Suzuki

Hirohisa Fujimoto

A polarization-maintaining optical fiber component which suppresses coupling of propagating light to a high-order mode at the optical coupling section of the polarization-maintaining optical fiber component, caused by different refractive indexes between the stress applying sections and the cladding, thus reducing excess loss, is constructed by using a polarization-maintaining optical fiber having stress applying sections arranged symmetrically to each other with respect to a core in a cladding surrounding the core, wherein the largest one of those concentric circles of the core or the said cladding which do not reach the stress applying sections and do not include the stress applying sections within has a diameter of 20 &#x3bc;m or greater.

Polarization-maintaining optical fiber and polarization-maintaining optical fiber component

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

The invention provides a method and apparatus that precisely and efficiently improves the optical properties of an optical fiber grating. Preferably hydrogen loading processing, grating formation processing that forms a grating part by irradiation with ultraviolet light at a predetermined period, and preferably dehydrogenation, adjusting the optical properties by a suitable combination of uniform ultraviolet irradiation processing that irradiates the grating part as a whole with ultraviolet light and heat trimming processing, and finally heat aging is carried out.

Optical fiber grating, optical fiber grating manufacturing method, and optical fiber grating manufacturing apparatus

In a method of manufacturing a polarization-maintaining optical fiber coupler by heating lengthwise portions of two polarization-maintaining optical fibers extending side by side, and elongating the heated portions to thereby form a fused-elongated section, elongation is terminated when the cyclic changes in a coupling ratio of two polarized waves according to an elongation length at a wavelength in use are both within first two cycles, so that the coupling ratio of one of the polarized waves is equal to or less than 10% and the coupling ratio of the other one of the polarized waves is equal to or greater than 90%. This method can provide a polarization-maintaining optical fiber coupler whose coupling ratio has a large dependency on polarization with a short elongation length.

Method of manufacturing polarization-maintaining optical fiber coupler

An optical fiber grating is manufactured by heating intermittently an optical fiber, provided with a core having residual stress in the longitudinal direction, softening a peripheral cladding of the core, and forming spatial periodical changes for the relative refractive index-difference between the core and the cladding, in the longitudinal direction of the aforementioned optical fiber by having the index of refraction of the core change, through the releasing of the aforementioned residual stress. As a result, an optical fiber grating and the manufacturing method thereof, which do not require expensive equipment and which exhibit high productivity, and furthermore a grating characteristic which is stable over time can be provided.

Optical fiber grating and manufacturing method thereof

Optical fiber grating and manufacturing method therefor

The present invention discloses a manufacturing method for polarization maintaining optical fiber couplers which are used for joining light signals and at optical fiber branch points. The disclosed manufacturing method employs polarization maintaining optical fibers, and describes a method for mutually aligning the stress applying parts of such optical fibers so that polarized optical signals are maintained in the polarized state when transiting such couplers.

Manufacturing method for polarization maintaining optical fiber couplers

Growing community of inventors

Sakura, Japan

Kenji Nishide