The Furukawa Electric Co., Ltd.

Tohoku Gakuin

Yu Mimura

Takeshi Nakajima

Katsutoshi Takahashi

Osamu Aso

Masateru Tadakuma

Misao Sakano

Ryo Miyabe

Kazuyou Mizuno

Hiroshi Matsuura

Takeshi Takagi

Yukihiro Tsuchida

Mieko Yamagaki

Ryuichi Sugizaki

Shu Namiki

Yoshihiro Emori

Koichi Maeda

Tsunetoshi Saito

Keiichi Aiso

Shigehiro Takasaka

Kengo Watanabe

Shigehito Yodo

Toshihiko Ohta

Kazuhiro Ikeda

Toshiaki Tsuda

Shigeto Matsumoto

Kazuyo Mizuno

Abe Hiroyuki

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

An optical amplifier includes an optical gain fiber into which signal light and pump light are input and at least one relative phase shifter is inserted. Preferably, the relative phase shifter is inserted so that the relative phase in the lengthwise direction of the optical gain fiber falls within a predetermined range containing 0.5&#x3c0;. Preferably, the optical gain fiber is a highly non-linear optical fiber having a non-linearity constant of at least 10/W/km. Preferably, the dispersion of the optical gain fiber is within the range from &#x2212;1 ps/nm/km to 1 ps/nm/km in an amplification band. Preferably, the absolute value of the dispersion slope of the optical gain fiber at a zero dispersion wavelength is no greater than 0.05 ps/nm/km.

Optical amplifier, optical amplifying system, wavelength converter, optical amplification method, and optical communication system

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 coupling structure optically coupling a plurality of core portions and a plurality of core portions includes a plurality of first core portions outputting a plurality of lights, a first lens focusing or collimating the plurality of lights outputted from the plurality of first core portions, a second lens focusing the plurality of lights focused or collimated by the first lens, a plurality of second core portions, the plurality of lights focused by the second lens being inputted into the second core portions respectively, and an optical functional component disposed between the first lens and the second lens, the plurality of lights being inputted into the optical functional component. At least one of the first lens and the second lens is configured by a lens or a lens group focusing or collimating the plurality of lights collectively.

Optical coupling structure and optical fiber amplifier

A method of simultaneously specifying the wavelength dispersion and nonlinear coefficient of an optical fiber. Pulsed probe light and pulsed pump light are first caused to enter an optical fiber to be measured. Then, the power oscillation of the back-scattered light of the probe light or idler light generated within the optical fiber is measured. Next, the instantaneous frequency of the measured power oscillation is obtained, and the dependency of the instantaneous frequency relative to the power oscillation of the pump light in a longitudinal direction of the optical fiber is obtained. Thereafter, a rate of change in the longitudinal direction between phase-mismatching conditions and nonlinear coefficient of the optical fiber is obtained from the dependency of the instantaneous frequency. And based on the rate of change, the longitudinal wavelength-dispersion distribution and longitudinal nonlinear-coefficient distribution of the optical fiber are simultaneously specified.

System for measuring the wavelength dispersion and nonlinear coefficient of an optical fiber

A polarization-maintaining optical fiber includes a core region and a cladding region formed around the core region. The cladding region has a refractive index lower than a refractive index of the core region. A refractive index profile of the core region is either one of a step shaped or a concave shaped. The cladding region includes two holes formed in such a manner that a shortest distance from the core region is virtually zero at locations in opposite to each other across the core region.

Polarization-maintaining optical fiber, method of manufacturing polarization-maintaining optical-fiber connecting portion, and polarization-maintaining optical-fiber connecting portion

The invention provides a Stokes parameter measurement device and Stokes parameter measurement method that enable high-precision measurement. The Stokes parameter measurement device comprises a polarization splitting device which comprises an optical element formed of a birefringent crystal material and which, by means of the optical element, splits signal light to be measured into a plurality of polarized light beams and adjusts the polarization state of one or more among the plurality of polarized light beams, and a light-receiving portion for performing photoelectric conversion of an optical component of the signal light split by and emitted from the polarization splitting device.

Stokes parameter measurement device and method

An optical fiber includes a core region and a cladding region. The cladding region includes a first cladding region on outer circumference of the core region, which includes a main-medium region and a sub-medium region having a refractive index lower than that of the main-medium region. The sub-medium region includes a plurality of inner sub-medium regions arranged along the outer circumference of the core region and a plurality of outer sub-medium regions arranged on outer of the inner sub-medium regions. The outer sub-medium regions have a lateral cross section larger than that of the inner sub-medium regions.

Optical fiber and optical transmission medium

An optical fiber includes a core region and a cladding region. The cladding region includes a first cladding region on an outer circumference of the core region, the first cladding region including a main-medium region and a sub-medium region having a refractive index lower than a refractive index of the main-medium region. The sub-medium region includes inner sub-medium regions arranged at four folds rotationally symmetric centering on the core region, and outer sub-medium regions arranged at four folds rotationally symmetric centering on the core region on an outer side of the inner sub-medium regions.

An object is to accurately measure the Stokes parameters, without the occurrence of polarization fluctuations or PDL during the splitting of the incident light. When the incident light is made incident on a first-stage prism, the light is split into two first splitting light rays. Next, the first split light rays are respectively incident on a pair of prisms of a second stage. Each of the pair of first split light rays is split into two rays by a second-stage prism, to obtain four second split light rays.

A PMD emulator configured by connecting in this order: an input-side optical fiberfor receiving light to be measured; a first polarization rotating portionincluding M DGD sections(M is an integer equal to or more than 2) concatenated by (M&#x2212;1) polarization rotators, one DGD section being arranged at each end of said first polarization rotating portion; an arbitrary-arbitrary polarization controllerfor changing any state of polarization into any other state of polarization, a second PMD rotating portionconfigured in the same way as the first polarization rotating portionan output-side optical fiber for outputting the light to be measured.

PMD emulator

Method and system for measuring the wavelength dispersion and nonlinear coefficient of an optical fiber, method of manufacturing optical fibers, method of measuring wavelength-dispersion distribution, method of compensating for measurement errors, and method of specifying conditions of measurement

A method of simultaneously specifying the wavelength dispersion and nonlinear coefficient of an optical fiber. Pulsed probe light and pulsed pump light are first caused to enter an optical fiber to be measured. Then, the power oscillation of the back-scattered light of the probe light or idler light generated within the optical fiber is measured. Next, the instantaneous frequency of the measured power oscillation is obtained, and the dependency of the instantaneous frequency relative to the power oscillation of the pump light in a longitudinal direction of the optical fiber is obtained. Thereafter, a rate of change in the longitudinal direction between phase-mismatching conditions and nonlinear coefficient of the optical fiber is obtained from the dependency of the instantaneous frequency. And based on the rate of change, the longitudinal wavelength-dispersion distribution and longitudinal nonlinear-coefficient distribution of thee optical fiber are simultaneously specified.

The optical thickness of a film formed on a substrate is controlled precisely to manufacture an optical filter having an accurate optical thickness. Time is counted during a film being formed on a substrate to note time points t with respect to a reference time set in advance. At least one of two optical characteristics of energy transmittance and energy reflectance when the film being formed on the substrate is irradiated with monitoring light is expressed by a function f(t) of the time points t based on a theoretical formula of the optical characteristic. The optical characteristic is measured by irradiating the film with the monitoring light at the time points t. A designed thickness achieving time at which the optical thickness of the film designed thickness is predicted. The film formation is stopped at the designed thickness achieving time, thereby obtaining the optical filter.

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Tokyo, Japan

Yu Mimura