The Furukawa Electric Co., Ltd.

Kunio Kokura

Ryuichi Sugizaki

Youichi Akasaka

Kazunori Mukasa

Koichi Furukawa

Shigehito Yodo

Kazunori Watanabe

Atsushi Umeda

Ikuo Ota

Luksun Li

Multi-core fibers are optical fibers each of which has a circular cross section. In each of the multi-core fibers, a plurality of cores are arranged at a prescribed interval, the peripheries thereof are covered by a cladding, and a resin coating is formed on the outer periphery of the cladding. In a cross section of this optical fiber ribbon, said cross section being orthogonal to the length direction, the multi-core fibers are arranged such that the cores of all of the multi-core fibers are all arranged in the same direction. The multi-core fibers are arranged such that central lines of the respective multi-core fibers, said central lines respectively linking three of the cores, all face the thickness direction of the optical fiber ribbon. Furthermore, in the optical fiber ribbon, the arrangement of the cores is substantially constant along the entire length of the optical fiber ribbon in the length direction.

Optical fiber ribbon, and optical-fiber-ribbon production method

In this multi-core fiber, a plurality of cores are arranged at a prescribed interval, and the peripheries thereof are covered by a cladding having a lower refractive index than the plurality of cores. A resin coating is formed on the outer periphery of the cladding. A colored section is formed on a section of the outer surface of the resin coating in the peripheral direction. The colored section is formed continuously along the length direction of the multi-core fiber. In a multi-core fiber cross section orthogonal to the length direction, the position of a specific core and the peripheral position where the colored section is formed are substantially constant along the length direction of the multi-core fiber. In other words, in the multi-core fiber cross section orthogonal to the length direction, the position of the specific core and the position where the colored section is formed are substantially constant along the length direction of the multi-core fiber.

Optical fiber, and optical-fiber production method

This invention provides an optical transmission line, which is small in dispersion in the 1570 to 1620 nm band (L-band) and low in nonlinearity, and thereby enables wavelength division multiplexed transmission in the 1520 to 1620 nm band, which contains the wavelength band that has been considered priorly. With this optical transmission line, an optical amplification device ( ), an SMF ( ), and an L-RDF ( ) are connected in that order to comprise a block, and one or more such blocks are inserted between an optical signal sending device ( ) and an optical signal receiving device ( ) to form the optical transmission line. With SMF ( ), the dispersion value and dispersion slope value in a preset wavelength band within the L-band are both positive. L-RDF ( ) is a line-type negative dispersion optical fiber that compensates the dispersion and dispersion slope of SMF ( ) in the abovementioned preset wavelength band. By connecting these SMF's ( ) and L-RDF's ( ), the dispersion value in the abovementioned preset wavelength band of the optical transmission line as a whole is made greater than or equal to &minus;1 ps/nm/km and less than or equal to 1 ps/nm/km.

Optical transmission line, negative dispersion optical fiber used for the optical transmission line, and optical transmission system comprising optical transmission line

The present invention relates to a fiber grating formed on an optical component for processing optical signals and a method of forming the grating. After the sheath ( ) of an optical fiber ( ) is partially removed, the surface of the bare optical fiber ( ) at an area where the sheath ( ) is removed is covered by a resin film ( ) having a thinness at which ultraviolet light permeability not hindering formation of gratings. Thereafter, by irradiating ultraviolet light (ultraviolet coherent light) via a phase mask ( ), a grating where the refractive index of the core ( ) of the bare optical fiber ) cyclically changes in the beam axis is formed. The resin film ( ) is made of, for example, an organic material having heat resistance, which is not dissolved by ultraviolet ray irradiation, such as polyimide resin, polyamideimide resin, etc. The thickness of the resin film ( ) is 10 &mgr;m or less to ensure that ultraviolet light sufficiently permeates and the convergence of interference light is not lowered.

Method for forming fiber grating and fiber grating formed by the same

An optical fiber which comprises a coating layer disposed outside a bare optical fiber having a core and a cladding and a grating formed in the core of the exposed bare optical fiber by removing the coating layer and its manufacturing method. The optical fiber is provided with a re-coating layer disposed in the exposed bare optical fiber.

Optical fiber and its manufacturing method

A dispersion compensating optical fiber is proposed for application in a wavelength optical signal transmission system. This dispersion compensating fiber has a W shaped refractive index profile, and has a first core layer, a second core layer formed around the outside of the first core layer, and a cladding layer made of substantially pure silica formed around the outside of the second core layer. The first core layer is doped with germanium, so that its refractive index s increased by a proportional refractive index difference of about 2%. The second core layer is uniformly doped with fluorine, so that its refractive index is decreased by a proportional refractive index difference of about 0.58%. The ratio of the outer radius of the second core layer to the outer radius of the first core layer is about 2.5. The wavelength dispersion slope is in the negative region, the dispersion is made to be high negative dispersion, and moreover the dispersion slope compensation ratio from a wavelength of 1530 nm to a wavelength of 1570 nm is made to be a value close to the perfect dispersion ratio and about 0.75 to 1.25 thereof.

Dispersion compensating optical fiber

The present invention is intended to provide a dispersion compensating optical fiber for wavelength division multiplex optical communication. A refractive index distribution of the dispersion compensating optical fiber is set to be W-shaped, an outside of a core is formed as an internal clad layer and the outside of the internal clad layer is formed as an outermost clad layer made of pure silica. Germanium for raising the refractive index by 2.8% in a specific refractive index difference is doped in the core, and fluorine is uniformly doped in the internal clad layer so that the refractive index is reduced by 0.45% in the specific refractive index difference. A diameter ratio of the core and the internal clad layer is set to be in a range of 1:1.5 to 1:4.0, a wavelength dispersion slope is set to be in a negative area, and dispersion is controlled to a negative high dispersion structure of -100 ps/km-nm or under.

Growing community of inventors

Tokyo, Japan

Kunio Kokura