The Furukawa Electric Co., Ltd.

Yukihiro Tsuchida

Kazunori Mukasa

Koichi Maeda

Ryuichi Sugizaki

Tsunetoshi Saito

Yu Mimura

Kengo Watanabe

Hiroshi Matsuura

Katsunori Imamura

Masateru Tadakuma

Keiichi Aiso

Shigehiro Takasaka

Ryo Miyabe

Shigeto Matsumoto

A multi-core optical amplifying fiber device includes a plurality of multi-core optical amplifying fibers including a plurality of core portions doped with amplification medium and a cladding portion formed at outer peripheries of the plurality of core portions; and a connection portion connecting the core portions of the plurality of multi-core optical amplifying fibers to one another. The connection portion connects the core portions to restrain deviation, between every connected core portions, of amplification gain for a total length of the core portions connected one another.

Multi-core optical amplifying fiber device and multi-core optical fiber amplifier

A bundle structure is obtained by arranging optical fibers having equal diameters in a close-packed arrangement around the outer circumference of a center optical fiber. The optical fibers are signal light optical fibers that transmit signal lights. The optical fiber is a pump light optical fiber that transmits pump light. The number of optical fibers is equal to the number of cores in the multi-core fiber. The bundle structure and the multi-core fiber are connected to one another by adhering or fusing. The cores and the cores are optically connected, and the core and the cladding are optically connected. When connecting, the mode field diameter of the cores and the cores are substantially equivalent. In addition, the outer diameter (diameter of circumscribed circle including optical fibers) of the bundle structure is set so as not to be greater than the outer diameter of the multi-core fiber.

Optical-fiber-bundle structure, rare-earth-doped multi-core fiber, connection structure therefor, method for exciting rare-earth-doped multi-core fibers, and multi-core-optical-fiber amplifier

A multi-core amplification optical fiber includes: a plurality of core portions doped with a rare-earth element; an inner cladding portion positioned at a periphery of the plurality of core portions, having a refractive index lower than a refractive index of the plurality of core portions, in which a first hole is formed; and an outer cladding layer positioned at a periphery of the inner cladding portion, having a refractive index lower than the refractive index of the inner cladding portion.

Multi-core amplification optical fiber

A multi-core amplification optical fiber includes a plurality of rare-earth-doped core portions and a cladding portion positioned at an outer periphery of the core portions and having refractive index lower than those of the core portions. When a doping concentration of the rare-earth of each of the core portions is 250 ppm to 2000 ppm, a relative refractive index difference of each of the core portions relative to the cladding portion is 0.5% to 2% at a wavelength of 1550 nm, and a core diameter of each of the core portions is 1 &#x3bc;m to 5 &#x3bc;m, a separation distance between each of the core portions and adjacent one of the core portions is set at equal to or larger than 30 &#x3bc;m and at equal to or smaller than 60 &#x3bc;m so that a light-crosstalk between the adjacent core portions is equal to or lower than &#x2212;30 dB.

Multi-core amplification optical fiber and multi-core optical fiber amplifier

An optical fiber includes a core portion that confines light therein and guides the light therethrough and a cladding portion that is formed around an outer circumference of the core portion. The cladding portion contains a hole which is formed at a position a distance away from the core portion such that the hole does not substantially affect an effective core area or a chromatic dispersion characteristic of the optical fiber. The hole decreases a microbending loss of the optical fiber.

Optical fiber

A holey fiber includes a core portion located at a center of the holey fiber, and a cladding portion located around the core portion, the cladding portion having holes formed in layers around the core portion. The holes are arranged so as to form a triangular lattice while d/&#x39b; is within a range of 0.33 to 0.43, &#x39b; is within a range of 10.5 micrometers to 15 micrometers when a hole diameter is d in micrometer and a lattice constant of the triangular lattice is &#x39b; in micrometer, and in a wavelength of 1550 nanometer, an effective core-area is equal to or greater than 130 &#x3bc;m, a bending loss in a case of bending the holey fiber at a bend diameter of 20 millimeters is equal to or less than 200 dB/m, and the holey fiber demonstrates a single-mode operation.

Holey fiber

An optical fiber includes a center core portion; an inner core layer formed around an outer circumference of the center core portion, a refractive index of which is less than that of the center core portion; an outer core layer formed around an outer circumference of the inner core layer, a refractive index of which is less than that of the inner core layer; and a cladding portion formed around an outer circumference of the outer core layer. A refractive index of the cladding portion is substantially equal to that of the inner core layer. At a wavelength of 1550 nm, an effective core area is equal to or larger than 130 &#x3bc;mand a bending loss is equal to or less than 100 dB/m when the optical fiber is bent with a diameter of 20 mm. A cable cut-off wavelength is equal to or less than 1530 nm.

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Tokyo, Japan

Yukihiro Tsuchida