Fujikura Limited

Akira Wada

Ryozo Yamauchi

Tetsuya Sakai

Kazuhiko Aikawa

Kensuke Shima

Shoichiro Matsuo

Kuniharu Himeno

Satoshi Okude

Manabu Saitou

Takaaki Suzuki

Tetsuo Nozawa

Daiichirou Tanaka

Takashi Suzuki

Michihiro Nakai

Koichi Harada

Tsuyoshi Shimomichi

Kenji Nishide

Hiroshi Hidaka

Shigefumi Yamasaki

Keiji Oohashi

Shinji Araki

Masaaki Sudoh

Nobuyuki Tanaka

Ken Sakuma

Naoki Kimura

Hideyuki Hosoya

Naoki Shamoto

Yuu Ishii

Hirokuni Ogawa

Shimon Ishikawa

Noriaki Shimada

Takuya Ienaka

Susumu Saito

Tomoko Shikata

Yasushi Takeda

An object of the invention is to improve polarization dependence of insertion loss (PDL) in an ultraviolet light induced optical fiber grating. In the invention, in a method of manufacturing an optical fiber grating with a plurality of grating sections arranged intermittently at a predetermined period along the longitudinal direction, by irradiating, from the side of an optical fiber having locations made of a material wherein the refractive index rises when irradiated by light of a specific wavelength, light of this specific wavelength along the length direction of the optical fiber at a predetermined period, causing the refractive index of the irradiated sections to rise, high refractive index sections are formed by irradiating light evenly onto the optical fiber around the circumferential direction thereof.

Method and device for manufacturing optical fiber grating, optical fiber grating, optical module, and optical communication system

An optical fiber is fabricated with a refractive index profile having a central core; a middle part provided around the outer periphery of the central core and having a lower refractive index than that of the central core; and a cladding provided around the periphery of the middle part and having a higher refractive index than the middle part and a lower refractive index than the central core. This optical fiber has an effective core area of 120 &#x3bc;mor more in an employed wavelength band selected from the range of 1.53&#x2dc;1.63 &#x3bc;m, and has a cut-off wavelength that is capable of substantially single mode propagation in the aforementioned employed wavelength band. As a result, it is possible to construct an optical transmission system having excellent transmission characteristics in which nonlinearity is decreased.

Optical fiber and optical transmission system

The present invention relates a method for manufacturing an optical coupler/splitter. A Y-shaped waveguide core is formed by focusing a laser beam into a cladding layer that is formed from a glass material. At least one portion of this Y-shaped waveguide core other than the input port and the output ports is treated as a refractive index adjustment area. After the portions of the Y-shaped waveguide core other than the refractive index adjustment area have been formed by focusing a laser beam, signal light is inputted into the input port of the Y-shaped waveguide core and the signal light outputted from the output ports of the Y-shaped waveguide core are monitored. The refractive index of the refractive index adjustment area is determined based on the result of the monitoring and is adjusted by focusing a laser beam repeatedly.

Manufacturing method for optical coupler/splitter and method for adjusting optical characteristics of planar lightwave circuit device

In order to provide a dispersion-compensating optical fiber able to be applied over a broad wavelength band, having a large effective area, and as a result, suppressing the occurrence of non-linear effects, the present invention comprises a dispersion-compensating optical fiber that compensates chromatic dispersion of a 1.3 &#x3bc;m single-mode optical fiber over the entire wavelength range of 1.53-1.63 &#x3bc;m characterized in that, chromatic dispersion at a wavelength of 1.55 &#x3bc;m is &#x2212;50 ps/nm/km or less, the dispersion slope is negative over the entire wavelength range of 1.53-1.63 &#x3bc;m, a cutoff wavelength is provided at which there is substantially single-mode propagation, bending loss is 30 dB/m or less, effective area is 20 &#x3bc;mor more, and the absolute value of chromatic dispersion during compensation of the chromatic dispersion of a 1.3 &#x3bc;m single-mode optical fiber serving as the target of compensation is 0.5 ps/nm/km or less.

Dispersion-compensating optical fiber and hybrid transmission line

An optical amplifier has a gain flatness which is maintained to be substantially constant regardless of temperature changes. The optical amplifier includes an EDF amplifying section and a Raman amplifying section, the Raman amplifying section having a temperature dependent gain profile which enables compensating for the temperature dependent gain profile of the EDF amplifying section. The Raman amplifying section includes a wavelength lock grating whose transmission wavelengths shift toward the short wavelength side as the temperature increases. The wavelength lock grating is preferably disposed to have the same temperature as that of an EDF of the EDF amplifying section. A method for compensating for temperature dependency of gain flatness of an optical amplifier and an optical transmission path including an optical amplifier are also disclosed.

Optical amplifier, method for compensating for temperature dependency of gain flatness of an optical amplifier and optical transmission path including optical amplifier

In order to provide a dispersion-compensating optical fiber able to be applied over a broad wavelength band, having a large effective area, and as a result, suppressing the occurrence of non-linear effects, the present invention comprises a dispersion-compensating optical fiber that compensates chromatic dispersion of a 1.3 &mgr;m single-mode optical fiber over the entire wavelength range of 1.53-1.63 &mgr;m characterized in that, chromatic dispersion at a wavelength of 1.55 &mgr;m is &minus;50 ps/nm/km or less, the dispersion slope is negative over the entire wavelength range of 1.53-1.63 &mgr;m, a cutoff wavelength is provided at which there is substantially single-mode propagation, bending loss is 30 dB/m or less, effective area is 20 &mgr;m or more, and the absolute value of chromatic dispersion during compensation of the chromatic dispersion of a 1.3 &mgr;m single-mode optical fiber serving as the target of compensation is 0.5 ps/nm/km or less.

An optical fiber for preserving the plane of polarization including a cladding and a stress imparting part disposed in the cladding, the stress imparting part comprising a base material including B O . The average concentration of B O in the base material of the stress imparting part is in a range between about 17 and 21 wt. %, and the maximum concentration of B O in the base material is in a range between about 17 and 22 wt. %. The optical fiber has excellent polarization plane preserving properties, and no concave portion is generated in its stress imparting part even under wet heat conditions.

Optical fiber for preserving plane of polarization

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 is related to an dispersion compensating optical fiber technology, comprising a central core, a middle part with a refractive index lower than this central core, and a cladding with a refractive index higher than said middle part and lower than said central core, characterized in: an outer diameter of said middle part being 2.5.about.3.5 times an outer diameter of said central core; a relative refractive index difference of said cladding to said middle part being -0.08.about.-0.2% with the refractive index of the cladding being zero; and having substantially single-mode transmission in the wavelength 1.55 .mu.m band, the chromatic dispersion being -80 ps/nm/km or less, the dispersion slope being +0.08 ps/nm.sup.2 /km or less, and the bending loss being 1.0 dB/m or less.

Dispersion compensating optical fiber

An optical waveguide grating with radiative mode-coupling properties, with exceptional stability and reliability as an optical component, wherein the central wavelength of the rejection band has a low temperature dependence, due to the use of silica glass doped with germanium and boron for the core. The rejection bandwidth can be narrowed without increasing the grating length by forming the radiative mode-coupled optical waveguide grating in an optical waveguide wherein the mean relative refractive index difference of the core is greater than that of optical communication waveguides. The rejection can be increased by reducing the occurrence of cases wherein propagation modes of the core coupled to cladding modes once again couple to the core in palnar optical waveguide gratings formed by making periodic changes in the waveguide structure along the direction of propagation of light in an optical waveguide having a cladding with a lower refractive index than the core surrounding the core, by making the thickness of the cladding at least thirteen times the thickness of the core.

Optical waveguide grating and production method therefor

Core comprises a main stem which is formed on a substrate, linearly extending in the beam propagating direction and short branches with a certain length which extend perpendicularly to the beam propagating direction toward both sides along the plane of the substrate and are arranged at regular intervals in the beam propagating direction. Thus, the branches are arranged in a ladder geometry when it is viewed from the top, forming a rectangular waveform arrangement. The core constitutes a grating structure in which the width of the core is made to vary periodically with the branches in the beam propagating direction.

Optical filter with planar optical waveguide having periodically varied

The present invention relates to an optical fiber filter provided with a portion which selectively reflects or transmits light of a specific wavelength, this portion comprised of a multimode optical fiber in which the refractive index of the core changes periodically along the longitudinal direction thereof. Furthermore, this multimode optical fiber has an input end and an output end, with at least the input end of the multimode optical fiber being connected to a single mode optical fiber. As a result of forming an optical fiber filter in this way, it is possible to realize an optical fiber filter that exhibits no transmission loss at wavelengths other than the center wavelength.

Optical fiber filter

A manufacturing method for erbium doped silica, having a soot formation process, in which a silica glass soot is deposited on a seed rod for forming a soot preform in a porous state on the seed rod, a dopant impregnation process, wherein the soot preform is impregnated with at least an erbium compound, and a preform formation process, wherein this soot preform impregnated with a dopant is heated and rendered transparent. The dopant impregnation process is provided with an operation in which the soot preform obtained in the soot formation process is dipped in a solution containing an erbium compound, an aluminum compound, and a phosphorus compound; this is then desiccated, and soot preform which is impregnated with the erbium compound, the aluminum compound, and the phosphorus compound is obtained.

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Sakura, Japan

Akira Wada