Abstract: The present invention relates to an OFA having a high signal gain, easily manufactured, having a high mechanical strength, having a small splice loss with respect to other optical fibers, and rarely encountering the occurrence of noise at a signal wavelength. The OFA according to the present invention has a function of amplifying signals propagating therethroug by pumping light supplied thereto, and comprises, at least, a core region, an inner cladding region provided on the periphery of the core region, an outer cladding region provided on the periphery of the inner cladding region, and one or more node coupling gratings. An element for signal amplification is added to at least the core region. The core region has a structure ensuring a core mode with respect to the signals, while the inner cladding region has a structure ensuring a multi-mode with respect to the pumping light.

Abstract: The present invention relates to an optical fiber grating element having structure enabling more precise design and fabrication, a production method thereof, and an optical fiber filter including the same. The optical fiber grating element according to the present invention comprises a multi-mode optical fiber having a first core region of a refractive index n1, a second core of a refractive index n2 provided on a periphery of the first core region, and a cladding region of a refractive index n3 provided on a periphery of the second core region, and having a cutoff wavelength regarding to LP02-mode light on the longer wavelength side than a wavelength band in use. A long-period grating for selectively coupling the fundamental LP01-mode light of a predetermined wavelength in the wavelength band I use to LP0m (m≧2)-mode light is provided in a predetermined region of the first core region.

Abstract: A method of forming a silica soot preform comprising: forming a primary soot preform on an outer periphery of a glass rod by a primary burner; and forming a secondary soot preform by a secondary burner on an outer periphery the primary soot preform, wherein a diameter of the primary soot preform is set to be ranged from twice to five times of a diameter of the glass rod, a thickness of the secondary soot preform is set to be range from 1.5 times to seven times of that of the primary soot preform. Consequently, the deposition rate with respect to the introduction of the raw material gas is considerably increased. Further, it is possible to maximize a performance of depositing the primary soot preform.

Abstract: A concentric multi-tubular burner for synthesizing glass particles having a center port group constituted by a combination of jet ports of raw material gas, combustible gas and oxygen gas, wherein an outer wall of the oxygen gas jet port in the center port group protrudes more toward a burner head than an inner wall of the oxygen gas jet port. The flow rate of oxygen gas jetted from the oxygen gas jet port of the center port group is controlled to be in a proper range.

Abstract: Fluorine-containing glass which comprises silica and contains, in said silica, not more than 10 ppm of OH group, not more than 10 ppm of Cl and not less than 1000 ppm of F, said fluorine-containing glass having a concentration ratio of F/Cl of 100 or more. Also disclosed is fluorine-containing glass which contains not more than 10 ppm of OH group, not more than 10 ppm of Cl and not less than 1000 ppm of F, and has a concentration ratio of F/Cl of 1000 or more.

Abstract: A dehydration and consolidation furnace and a dehydration and consolidation method in which gas in a chamber does not leak to a furnace body room and gas in a furnace body room does not leak into a chamber is provided. A furnace of one embodiment of this invention has first muffle tube 3 and second muffle tube 4. The second muffle tube 4 is arranged coaxially around the first muffle tube 3. An optical fiber preform is arranged in this furnace. During the dehydration and consolidation process the pressure of the intermediate room 10 is set lower than a pressure inside the first muffle tube and outside the second muffle tube, and a gas supply and exhaust of the intermediate room 10 are performed independent of the gas supply and exhaust of the first muffle tube and a furnace body room.

Abstract: The present invention relates to an optical fiber grating element having structure enabling more precise design and fabrication, a production method thereof, and an optical fiber filter including the same. The optical fiber grating element according to the present invention comprises a multi-mode optical fiber having a first core region of a refractive index n1, a second core of a refractive index n2 provided on a periphery of the first core region, and a cladding region of a refractive index n3 provided on a periphery of the second core region, and having a cutoff wavelength regarding to LP02-mode light on the longer wavelength side than a wavelength band in use. A long-period grating for selectively coupling the fundamental LP01-mode light of a predetermined wavelength in the wavelength band I use to LP0m (m≧2)-mode light is provided in a predetermined region of the first core region.

Abstract: The present invention relates to an OFA having a high signal gain, easily manufactured, having a high mechanical strength, having a small splice loss with respect to other optical fibers, and rarely encountering the occurrence of noise at a signal wavelength. The OFA according to the present invention has a function of amplifying signals propagating therethroug by pumping light supplied thereto, and comprises, at least, a core region, an inner cladding region provided on the periphery of the core region, an outer cladding region provided on the periphery of the inner cladding region, and one or more node coupling gratings. An element for signal amplification is added to at least the core region. The core region has a structure ensuring a core mode with respect to the signals, while the inner cladding region has a structure ensuring a multi-mode with respect to the pumping light.

Abstract: This invention relates to an optical fiber grating and a method of manufacturing the same. According to the method, a hydrogen doping process is performed before ultraviolet irradiation in order to obtain a sufficient photoinduced refractive index change. In particular, a target for the hydrogen doping process of the method is characterized by a coated fiber obtained by covering the outer surface of the bared fiber having a core region and a cladding region with the resin. After the coated fiber is exposed in a hydrogen atmosphere in a predetermined pressurized state for a predetermined period of time, the resin is partially removed. An ultraviolet ray is irradiated on the predetermined area of the bared fiber from which the resin is removed, thereby forming a reflection grating in the core region. The method is also characterized in that the pressure of the hydrogen atmosphere is reduced from the pressurized state while adjusting the pressure reducing rate.

Abstract: A glass body for optical fiber containing GeO.sub.2 --SiO.sub.2 glass in a core portion thereof, in which the GeO.sub.2 --SiO.sub.2 glass has an absorbance at 5.16 eV of at least 1/mm but not higher than 2.5/mm or in which concentration of Ge.sup.2+ contained in the GeO.sub.2 --SiO.sub.2 glass substantially lies within the range of 1.1.times.10.sup.-9 to 2.8.times.10.sup.-9 mol/mm.sup.3 as calculated by the following general equation:A=.epsilon..sub.5.16ev .multidot.C.sub.(Ge2+) .multidot.1wherein A is absorbance which is expressed by A=-log T (T being transmittance) and normalized per 1 mm of optical path length, C.sub.(Ge2+) is Ge.sup.2+ concentration, .epsilon..sub.5.16ev is absorption coefficient (1/mol/cm), and 1 is optical path length.

Abstract: A colored microlens array which functions as both a color filter array of different color filter layers and transparent microlenses. The colored microlens array has a transparent basic layer and a plurality of colored microlenses of different colors formed on the transparent basic layer in two dimensional arrangement in accordance with at least one basic color arrangement pattern. The colored microlenses are manufactured by forming semispherical lens forming layer portions on the respective color filter layers of the color filter array and by etching the color filter layers with the formed semispherical lens forming layer portions as a mask, to change in shape the respective color filter layers into the semispherical lenses, respectively. The colored microlenses are applied to solid-state image sensing devices, color liquid crystal display units, etc.

Abstract: Light is directed to each photosensitive section by independently adjusting the curvature or thickness of each light converging lens above the photosensitive section, irrespective of the shape of a photosensitive element (photosensitive section), i.e., irrespective of the shape having a longer side in the row direction than the side in the column direction. Specifically, a strip layer is formed above a plurality of photosensitive sections, disposed in a row direction. Light converging lenses are formed on each strip layer to obtain a desired curvature or thickness.