Abstract: This process for producing an optical waveguide comprises a step of sintering a glass fine-particle layer to form a upper cladding layer, and a step of controlling a refractive index of the upper cladding layer by changing a temperature decreasing rate when the glass layer is cooled down to the room temperature.

Abstract: The present invention relates to a package in which an optical waveguide module is mounted, at least having such structure as to reduce influence of expansion or contraction (thermal stress) of a metal housing, caused with a temperature change of the external environment and applied on junction parts between an optical waveguide substrate and members for fixedly supporting tip portions of input and output optical fibers. This package comprises a cavity for housing the whole of the optical waveguide module as covered with a buffer protection material, and a metal housing having through holes for leading the above optical fibers to the outside. Particularly, the optical fibers and the through holes are bonded and secured with a filler having higher airtightness than the buffer protection material and having a lower tensile modulus than a metal material forming the housing.

Abstract: A method for producing an oxide glass thin film is provided, in which volatilization of additives in a porous film from which the thin film is formed is effectively suppressed, and which the oxide glass film has a desired arrangement of refractive index with a low optical loss. According to this method, glass fine particles mainly containing SiO.sub.2 with a first additive are deposited on a substrate to form a porous thin film. A gas containing a second additive is supplied to a first chamber and heated to a first predetermined temperature profile to provide a heated gas containing an oxide. After disposing the substrate in a second chamber communicated with the first chamber, the substrate is heated to make the deposited porous glass into transparent glass while controlling a temperature in the second chamber according to a second temperature profile.

Abstract: An optical branching device according to present invention comprises a cladding member, a first core member, a second core member, and a third core member. These core members are isolated each other, and the with of a edge face of the first core member is greater than total length of the widths of second and third core members terminals facing to the first core member and a gap between the second and third core members.

Abstract: An optical branching device comprising: a substrate; a first core member formed on the substrate, having a first edge face; a second core member formed on the substrate, tapering toward the first edge face of the first core member, having a second edge face facing the first edge face at a given space; and a third core member formed on the substrate, tapering toward the first edge face of the first core member, having a third edge face facing the first edge face at a given space.

Abstract: In a method of fabricating DCF, the fiber is drawn while rotating said optical fiber preform, wherein a rotational speed of said optical fiber preform is 10 to 1,000 rpm, a drawing speed is 50 to 1,000 m/min, and a drawing tension is 2.4 to 13 kg/mm.sup.2.

Abstract: A process for forming film structure using Flame Hydrolysis Deposition (FHD) in which (1) glass soot is deposited on a substrate via FHD to form a first porous vitreous layer having a first bulk density, (2) a second porous vitreous layer having a second bulk density that is larger than the first bulk density is formed from a portion of the first porous vitreous layer, and (3) a third porous vitreous layer having a third bulk density is formed by depositing glass soot containing a refractive index increasing dopant on the second porous vitreous layer by FHD. The first, second and third porous vitreous layers are then heated to form an undercladding layer and a core layer, the undercladding layer being formed from the first and second porous vitreous layers and the core layer being formed from the third porous vitreous layer.

Abstract: A dispersion compensating fiber has a negative chromatic dispersion slope and a value of chromatic dispersion suitable for practical application, and a bending loss thereof with a bending diameter of 40 mm is smaller than 0.01 dB/m at 1.55 .mu.m. A diameter of a core is larger than 3 .mu.m but smaller than 4 .mu.m. A ratio (Da/Db) of the diameter of the core to an outer diameter of a first cladding is between 0.4 and 0.6 both inclusive. A relative refractive index difference of the core to a second cladding, (nc-n2)/n2, is larger than 0.02 but smaller than 0.03. A relative refractive index difference of the first cladding to the second cladding, (n2-n1)/n2, is larger than 0.004 but smaller than 0.01. This dispersion compensating optical fiber has a sufficient negative chromatic dispersion slope at wavelengths (1.55 .mu.m to 1.65 .mu.m both inclusive) around 1.55 .mu.m and a bending loss thereof at the wavelength of 1.55 .mu.m with the bending diameter of 40 mm is smaller than 0.01 dB/m.

Abstract: In the method for forming an optical waveguide according to this invention, an optical waveguide comprising a core of quartz as a main component, and a cladding layers surrounding the core is formed by deposition of glass fine particles by flame hydrolysis deposition and vitrifying the glass fine particle layers. This method includes a step of transiently increasing a feed amount of phosphorus to a flame burner in forming glass fine particle layers to be the cladding layers. Feeding phosphorus in this step for the first time after a glass fine particle layer is deposited without feeding phosphorus to the flame burner, whereby generation of foreign objects near the core dan be suppressed.

Abstract: A method of producing an oxide glass thin film includes a process to obtain a transparent glass film, in which volatilization of additives in a porous film deposited is effectively suppressed and which can provide an oxide glass thin film having a desired arrangement of refractive index with a low optical loss. The method is for producing an oxide glass thin film, in which glass fine particles mainly containing SiO.sub.2 with additives are deposited on a substrate to form a porous thin film and then heated to form a transparent glass film. In the method, vapor of oxides of additive components is mixed in an atmosphere in which the porous thin film is heated to form the transparent glass film, whereby stopping the volatilization of the additives in the porous film deposited, preventing diffusion of the additives added to a core layer, and preventing the volatilization of glass transition temperature lowering components of additives (P.sub.2 O.sub.5, B.sub.2 O.sub.3, GeO.sub.2, etc.).

Abstract: An object of this invention is to provide a mode field diameter conversion optical fiber which can be processed in a short period of time to have a reduced mode field diameter at a desired portion thereof. The optical fiber according to this invention comprises a core of silica glass having a residual tensile stress, and a cladding surrounding the core and having a lower refractive index than that of the core. The desired portion is heated to relax the residual tensile stress in the core, whereby the optical fiber has a reduced mode field diameter at the desired portion.

Abstract: The present invention comprises a waveguide substrate and an optical waveguide disposed on the substrate, the optical waveguide having an optical waveguide region as a light transmission path, an insertion region for inserting an optical functional component having a mode field width of light propagating therein larger than that of light propagating in the optical waveguide region, and an optical connection region provided between the optical waveguide region and the insertion region to change a mode field width of light propagating therein.

Abstract: Lead-containing fluoride glass comprises 50-70 mol % of ZrF.sub.4, 3-5 mol % of LaF.sub.3, 0.1-3 mol % of YF.sub.3, and 2-15 mol % of NaF and/or LiF and/or CsF, where LaF.sub.3 +YF.sub.3 =4.5-6 mol %, and further comprises lead. An optical fiber comprises a core made of the lead-containing fluoride glass and a cladding surrounding the core. A process for producing an optical fiber comprises forming a base material for a core of the lead-containing fluoride glass, forming a base material for a cladding of fluoride glass containing 30-60 mol % of HfF.sub.4, and drawing the base materials into an optical fiber at a drawing temperature of 315.degree.-340.degree. C.

Abstract: An object of this invention is to provide an optical filter which has higher mass-producibility and economy. This feature can be realized by doped a rare earth element into the region made of a glass material which can transmit light. In a case that Er and Tm are doped as the rare earth element into the region, a ratio .alpha..sub.Er /.alpha..sub.Tm between a contribution .alpha..sub.Er of Er to attenuation and a contribution .alpha..sub.Tm of Tm to attenuation is set in a range from about 1 to 1/25 for a 1.5 .mu.m band range, whereby attenuation in this wavelength range is retained above 50 dB/m to realize required cutoff function.

Abstract: In the first step, a fuel and raw material gases are fed to burner while flames from the burner scan a Si substrate. Synthesized fine glass particles are deposited on the substrate to form a first porous vitreous layer to be an under cladding layer. In the second step, the first porous vitreous layer is heated by the flames. A bulk density of an upper part of the first porous vitreous layer is raised to 0.3 g/cm.sup.3. Having a raised bulk density, this upper part functions as a shield layer against GeO.sub.2. In the third step, a second porous vitreous layer, to be a core layer, is deposited uniformly on the first porous vitreous layer. In the fourth step, the first and the second porous vitreous layers are sintered. In this case, the shield layer with a higher bulk density hinders the GeO.sub.2 component which has evaporated from the second porous vitreous layer from diffusing into the first porous vitreous layer.

Abstract: In an optical fiber functional device for processing a light beam between optical fibers, single-mode optical fibers for processing the light beam are concentrically connected at the mutually opposed ends to convergence-type rod lenses each having a prescribed length and made of a graded-index optical fiber.

Abstract: There is disclosed an optical waveguide comprising a core portion made of a light propagating material and a cladding portion, a first dopant and a second dopant being induced into said core portion, the first dopant having a function of increasing a refractive index of the light propagating material and having a first thermal diffusion coefficient to said light propagating material, the second dopant having a function of decreasing the refractive index of said light propagating material and having a second thermal diffusion coefficient to the light propagating material larger than the first thermal diffusion coefficient under a predetermined temperature.

Abstract: An optical functioning glass for enabling optical amplification at 1.3-.mu.m wavelength band or increasing efficiency of the amplification is disclosed. The optical functioning glass contains Nd.sup.3+ as an active material and uranium, both of which are doped in a multi-component function glass serving as a host glass. Since uranium is doped in the optical functioning glass, light emission of Nd.sup.3+ in the 1.06-.mu.m wavelength band can be absorbed by uranium. A decrease in efficiency of induced emission in a 1.3-.mu.m wavelength band can be prevented, and an optical functioning glass suitable for optical amplification in the 1.3-.mu.m wavelength band can be obtained. When a fiber is formed using the optical functioning glass as a core, a low-threshold, high-gain fiber amplifier, fiber laser, and the like can be obtained.

Abstract: A thin glass film is formed on a substrate using a sol-gel method by applying to the substrate a hydrolyzable solution which contains a metal alkoxide, water, an alcohol and an acid, contacting the applied solution with an atmosphere containing ammonia and an alcohol to polycondensate the metal alkoxide, and heating to form the thin glass film.

Abstract: There is disclosed an optical component capable of amolifying function by itself and a method of producing thereof. The component includes a light amplifying portion therein and the light amplifying portion includes active elements which serves the light amplification. In the producing method, the amplifying portion is, for example, formed by utilizing sol-gel method to introduce the active elements.