Abstract: The present invention relates to a single-mode optical fiber having a configuration which enables lowering of dispersion slope while securing a sufficient MFD. This single-mode optical fiber has a refractive index profile in which an indent with a sufficient width is provided at the center of its core region. In particular, this indent satisfies the following relationship: a·(&Dgr;n2−&Dgr;n1)/(b·&Dgr;n2)≧0.04 when the first core portion in the single-mode optical fiber has a mean relative refractive index difference of &Dgr;n1 with respect to the cladding portion and an outer diameter of a while the second core portion has a mean relative refractive index difference of &Dgr;n2 with respect to the cladding portion and an outer diameter of b.

Abstract: A sintered dense glass, alumina-doped optical fiber preform is stretched and is then heated to a temperature of 1490-1495° C. to remove bubbles without causing crystallization. Thereafter, the stretched glass body is either drawn directly into an optical fiber or overclad and then drawn into a fiber.

Abstract: A process for producing synthetic quartz glass using a burner composed of a plurality of concentric nozzles involves the steps of feeding a silica-forming raw material gas and a fluorine compound gas to a reaction zone from a center nozzle, feeding oxygen gas from a second nozzle outside the center nozzle, and feeding oxygen gas and/or hydrogen gas from a third nozzle. The silica-forming raw material gas is hydrolyzed to form fine particles of silica, which particles are deposited on a rotatable substrate so as to form a porous silica matrix, which is then fused to give the quartz glass. The flow rate of the oxygen gas fed from the second nozzle and the flow rate of the raw material gas are controlled so as to provide a 1.1- to 3.5-fold stoichiometric excess of oxygen. The excess oxygen suppresses Si—Si bond formation in the quartz glass, enabling the production of synthetic quartz glass having a high transmittance in the vacuum ultraviolet region.

Abstract: Disclosed is a method of minimizing re-wetting of a preform upon removal of the preform from the consolidation furnace and producing core cane and/or optical fiber therefrom. During removal, the consolidated preform and, in particular, the centerline aperture is exposed to a heavy inert gas, such as Argon, Krypton or Xenon. This reduces the amount of re-wetting thereby concomitantly improving attenuation of the optical fiber produced therefrom. This method produces beneficial attenuation reductions in the 1383 nm wavelength region.

Abstract: A method and a burner for manufacturing silica-containing soot is disclosed. The method includes providing a liquid silicon-containing feedstock and a gas mixture and ejecting the liquid-gas mixture from an orifice into a combustion site to convert the silica-containing feedstock into silica containing soot. The burner includes a plurality of channels for delivering a gas to provide a flame, an effervescent atomizer for atomizing a liquid, silicon-containing feedstock and a rail for guiding the atomized liquid, silicon-containing feedstock into the burner flame. The method and burner can be used to produce silica-containing articles such as high purity fused silica optical members and waveguides.

Abstract: An apparatus and method for producing a tubular member, which is suitable for use as a starter tube or an optical fiber preform, on a rotating cylindrical target mounted on a lathe. The tubular member is made by means of plasma outside vapor deposition. In this process, a source gas comprising SiCl4 and, optionally, a fluorine-laden chemical, is introduced into an air plasma. Both the air and the source gas are dry gases and have low hydroxyl content. The air plasma is created by a high-frequency induction plasma torch which travels along the length of the target on a carriage. The torch is provided with a short U-shaped gutter on either side of its rim directly beneath the target and the growing tubular member. This gutter helps channel reaction products of the source gas and the plasma so as to enhance deposition on the growing tubular member.

Abstract: A method of making a segmented core optical waveguide preform for making fiber that is resistant to attenuation increases due to hydrogen and heat aging. A first core region comprising a silica glass rod containing at least a first dopant is inserted into a central opening of a second core region comprising silica soot containing a second dopant. The first core region and second core region are consolidated together to form a segmented core region and cladding is deposited on the outer surface of the segmented core region.

Abstract: Disclosed is an optical waveguide fiber having a compressive outer layer that includes TiO2 in the SiO2 matrix glass. The compressive outer layer includes crystalline structures containing TiO2 that are predominately rutile. Also disclosed is a method for making an optical waveguide fiber having a compressive outer layer. The compressive outer layer can contain an additional metal oxide that is preferentially lost from the outer layer, instead of the TiO2, during the drying and consolidation step.

Abstract: Improved single-mode optical waveguide fibers having a central core region, surrounded by an inner cladding region through which light at a chosen signal wavelength will propagate to an appreciable degree along with propagation of same in the central core region, the inner core region further surrounded by an outer cladding region, the improvement comprising germanium dioxide in the inner cladding region at a concentration within the range of about 0.005 percent by weight to about 1 percent by weight of said inner cladding region, effective to significantly reduce the concentration of oxygen atoms in the inner cladding region which are available to form defects that cause hydrogen-induced attenuation. Also provided are core preforms, overclad preforms, and processes for making the fibers, core preforms and overclad preforms.

Abstract: A method of manufacturing synthetic silica glass includes the steps of pressurizing a liquid storage tank including a liquid silicon compound therein, generating bubbles in the liquid silicon compound using a foamer, removing the bubbles using a degasser, displacing the liquid silicon compound into a vaporizer while controlling an amount of the liquid silicon compound displaced by a liquid mass flow meter, mixing the displaced liquid silicon compound with a carrier gas to generate a gaseous silicon compound, injecting the gaseous silicon compound into a synthesis furnace, and forming synthetic silica glass by hydrolyzing the gaseous silicon compound in the synthesis furnace.

Abstract: The present invention relates to a single-mode optical fiber having a configuration which enables lowering of dispersion slope while securing a sufficient MFD. This single-mode optical fiber has a refractive index profile in which an indent with a sufficient width is provided at the center of its core region. In particular, this indent satisfies the following relationship:a.multidot.(.DELTA.n.sub.2 -.DELTA.n.sub.1)/(b.multidot..DELTA.n.sub.2).gtoreq.0.04when the first core portion in the single-mode optical fiber has a mean relative refractive index difference of .DELTA.n.sub.1 with respect to the cladding portion and an outer diameter of a while the second core portion has a mean relative refractive index difference of .DELTA.n.sub.2 with respect to the cladding portion and an outer diameter of b.

Abstract: An apparatus is provided for synthesizing a silica glass ingot. The appartus includes a stage having a target plate thereover, the target plate being rotatable relative to the stage around a predetermined vertical axis, and a furnace for reacting material gas with combustion gas to synthesize the silica glass ingot on the target plate; the furnace having an opening at its bottom. The appratus further includes an elevation system that moves the stage in a vertical direction parallel to the predetermined vertical axis so as to vertically move the target plate through the opening of the furnace, the elevation system supporting the stage from at least one side of the stage and lacking a structure directly below the stage that would substantially interfere with the vertical movement of the stage.

Abstract: An apparatus for producing an optical fiber porous glass preform using the VAD method which can stably produce a high quality optical fiber porous glass preform, wherein a target bar is only rotatably supported by a chuck and is not pulled upward, a lower tip of a soot body is detected by a laser and a photodetector, and a core burner and a cladding burner is lowered in response to the result detected. A tip position detecting drive and burners are synchronizingly lowered while the deposit of porous glass grows at the lower portion of the target bar.

Abstract: The present invention is directed to a method for making silica glass and silica glass preforms. A liquid, preferably halide-free, silicon-containing compound capable of being converted by thermal oxidative decomposition to SiO.sub.2 is provided and introduced directly into the flame of a combustion burner, which converts the compound to silica, thereby forming finely divided amorphous soot. The soot is vaporized proximate the site where the liquid is converted into silica glass by atomizing the liquid, preferably with a stream of atomizing gas. A heater proximate the burner face and around the burner flame increases soot capture rate and allows for a reduction of the velocity of the atomizing gas. The amorphous soot is deposited on a receptor surface where, either substantially simultaneously with or subsequently to its deposition, the soot is consolidated into a body of fused silica glass.

Abstract: The invention relates to a method of performing surface treatment on a preform manufactured in an installation for manufacturing or building up preforms having supporting cores, the installation including at least rotation means having a horizontal axis of rotation and two mounting points between which the supporting core of the preform to be manufactured or built up is mounted, plasma-torch and material-supply means disposed radially relative to the supporting core and mounted to move in axial translation relative to and parallel to the supporting core so as to make the preform around the supporting core, the preform being manufactured or built up by effecting successive passes with the plasma torch while material is being supplied.

Abstract: A method for making an optical fiber preform comprises depositing fine particles of glass serving as a dad on the surfaces of a rod-shaped core over a given length of the rod-shaped core by use of a plurality of oxyhydrogen flame burner units, detecting an amount of the resultant deposit to check uniformity in the amount of the deposit along the lengthwise direction of the rod-shaped core during the course of the deposition, and further depositing fine particles of glass on any surface portion of the rod-shaped core within the given length from at least one burner unit other than the plurality of burner units to correct the amount of the deposit over the given length based on the results of the detection. The resultant deposit is dehydrated and fired by a usual manner to obtain a preform. An apparatus for carrying out the method is also described.

Abstract: An optical fiber preform is made by supplying the base glass reactant and the dopant glass reactant to a burner that generates a flame in which a stream of glass particles is produced. The burner moves with respect to a rotating mandrel to deposit layers of glass particles on the mandrel. During the deposition of a portion of the preform, the flow rate of the dopant glass reactant is varied in accordance with a first recipe of dopant flow as a function of burner position as the burner moves longitudinally along the substrate to form one of the layers. The flow rate of the dopant glass reactant varies in accordance with a second recipe of dopant flow as a function of burner position as the burner moves longitudinally along the substrate to form a layer adjacent to the one layer. The second recipe is different from the first recipe, and the flow rate of the dopant glass reactant changes during the step of moving the reaction zone to form the one layer.

Abstract: A glass preform for an optical fiber is effectively drawn by connecting dummy rods to both ends of the glass preform and connecting the dummy rods to fitting members.

Abstract: A solid or hollow cylindrical heat-resistant substrate having a tapered shape is rotated about its axis, the degree of tapering being essentially constant along the entire length. The substrate has an outer diameter in the range of 20 mm to 500 mm and a length in the range of 500 mm to 5,000 mm. A mother material body made of porous quartz glass is formed on the outer surface of the substrate by chemical deposition, and vitrified by heating while holding it vertically with the larger outer-diameter side of the heat-resistant substrate positioned downward. Alternatively the heat-resistant substrate is extracted from the mother material body and a heat-resistant tapered body with a taper similar to that of the substrate is inserted into the hole left after extraction in the central region of the mother material body. The mother material body is vitrified starting at the lower end with the larger outer-diameter side positioned downwardly.

Abstract: Recent UV-lithography is required to provide a fine and sharp pattern with a line width of 0.5 .mu.m or less. A silica glass member adapted for use as an optical element for UV-lithography, by giving consideration to the RMS value of wave front aberration and the slant element of refractive index, which have not been considered in the art. Also there is provided a silica glass member excellent in durability to the ultraviolet irradiation, by introduction of hydrogen molecules at the synthesis of the silica glass, instead of using a secondary treatment for hydrogen introduction.

Abstract: A method of manufacturing an optical fiber in which the deviation of a cutoff wavelength from a design value can be minimized. It is found that, upon diameter reduction of a porous core glass body by heat treatment, when the diameter reduction ratio is set to a value larger than 0.90, a "spike" in the refractive index distribution curve of a core can be prevented, and the deviation of the cutoff wavelength from the design value can be minimized. Therefore, there is provided a method comprising the first step of depositing fine SiO.sub.2 particles and fine GeO.sub.2 particles, which are produced by a core formation burner, to grow a porous core glass body from a distal end of a rotating starting rod in an axial direction, the second step of performing diameter reduction by heating the grown porous core glass body by heating means while growing the porous core glass body, and the third step of depositing fine SiO.sub.

Abstract: The invention relates to a method of drying and sintering porous optical fiber preforms, especially those consisting of a solid glass core cane surrounded by a layer of cladding soot. After it is dried in a dehydrating atmosphere, the porous preform is heated to a presinter temperature just below that at which it would begin to rapidly densify. The various temperature holds and ramp rates are such that the preform is consolidated in a relatively short time without becoming cloudy or exhibiting other defects that would adversely affect the optical fiber drawn from the consolidated draw blank.

Abstract: During the gradual build-up of porous quartz glass by the combustion of a hydrolysis gas mixture and preferably for a certain period of time thereafter, a drying gas mixture is conducted under positive pressure through the porous tubular deposit from the inside to the outside as it is being built-up. This is accomplished by depositing the quartz on a tubular substrate in which a drying gas is introduced at positive pressure.

Abstract: A precision burner for oxidizing halide-free, silicon-containing compounds, such as, octamethyl-cyclotetrasiloxane (OMCTS), is provided. The burner includes a subassembly (13) which can be precisely mounted on a burner mounting block (107) through the use of an alignment stub (158), a raised face (162) on the burner mounting block (107), and a recess (160) in the back of the subassembly (13). The burner's face includes four concentric gas-emitting regions: a first central region (36, 90) from which exits a mixture of OMCTS and O.sub.2, a second innershield region (38, 92) from which exits N.sub.2, a third outershield region (40, 42, 94, 96) from which exits O.sub.2, and a fourth premix region (44, 98) from which exits a mixture of CH.sub.4 and O.sub.2. The burner provides more efficient utilization of halide-free, silicon-containing raw materials than prior burners.

Abstract: A process for producing a porous glass preform for optical fiber by depositing fine glass particles on an outer surface of a glass material while moving the glass material, including the steps of: preheating a portion of the glass material for not less than 5 minutes to clean the portion of the glass material in an apparatus for depositing fine glass particles; and depositing fine glass particles on the portion of the glass material cleaned by the preheating, in the apparatus for depositing fine glass particles.

Abstract: Low attenuation, low dispersion of optical waveguides are provided by a process initiating with axial deposition of a high velocity core soot stream impinging on, a target at a high angle of incidence relative to the axis of rotation of the target. A core cylinder is built up axially by relative movement between the soot stream and target during deposition, the movement being non-constant in order to maintain a substantially constant diameter with a constant deposition rate. A cladding layer is then built up by deposition of soot radially on the core. Subsequent drying and sintering provides a vitreous preform which may be drawn directly into optical waveguides. Alternatively, the sintered product may be drawn down to smaller rods, which then are covered with further deposited soot cladding to a desired final thickness, and after further drying and sintering may be drawn to optical waveguides.

Abstract: In a method of forming a preform from which an optical fibre can be drawn, successive layers of matter (24, 28) are deposited by vapour deposition on a rotating cylindrical body (10) which is traversed by a heat source (15). For the deposition of at least two successive layers (24, 28), a rate of rotation of the body and/or a rate of traverse of the heat source is selected so as to generate in one of said layers a surface profile different to a surface profile generated in the other said layer.

Abstract: In a method for making optical fiber preforms, the time taken for sintering and annealing the clad or jacket layer is significantly reduced by only partially sintering the jacket soot boule in an atmosphere of helium. For example, instead of using one hundred forty-three minutes to sinter completely the soot boule, the boule is only partially sintered by heating in a helium atmosphere for fifty-nine minutes. At this stage of course, the soot boule is still partially porous and is generally opaque. The completion of the sintering and the annealing is then done in a single step in an atmosphere of nitrogen. Surprisingly, we have found that this process does not entrap nitrogen in the soot jacket layer to any noticeable or harmful extent, and the total time for sintering and annealing is significantly reduced.

Abstract: There is provided an apparatus for the production of a hermetically coated optical fiber in which a glass preform for an optical fiber is melt drawn in a melt drawing furnace to produce a bare optical fiber which is passed to a reactor where a feed gas is supplied and the bare optical fiber is coated with a thin carbon coating made from the feed gas by the Chemical Vapor Deposition method characterized in that the reactor comprises an upper portion to which the feed gas is supplied, a middle portion in which the CVD method is substantially carried out and a lower portion from which an exhausted gas is withdrawn, and a cross sectional area of the middle portion perpendicular to a longitudinal direction of the optical fiber is larger than that of the upper portion.

Abstract: After a plurality of optical fibers are fused to make a fiber optic coupler, the ends thereof are glued to a substrate to provide the outwardly extending fibers with adequate pull strength. The glue can flow from the point of application toward the fused region where it can adversely affect the the device. To prevent the glue from flowing too far toward the fused region and yet permit sufficient flow to strengthen the fibers, a beam of UV light is directed onto the fibers at that predetermined point where glue flow should stop. When the glue is cured by the beam, it stops flowing. Thereafter, the remainder of the glue is cured.

Abstract: A fiber optic coupler is formed by providing a glass tube having a longitudinal bore and first and second funnels connecting the bore to the ends of the tube. The protective coating is stripped from the central portion of two optical fibers. The first and second fibers are threaded into the tube bore until the uncoated portions thereof are located within the bore. The protective coating of only one of the fibers extends into the first end of the bore, and the protective coating or only one of the fibers extends into the second end of the bore. The fibers extend beyond the tube ends. The bore diameter is just slightly larger than the sum of the diameter of the first fiber and the diameter of the coating of the second fiber. The resultant tight fit of the fibers in the tube promotes the retention the fibers in parallel alignment during the subsequent tube collapse step. The midregion of the tube is heated, collapsed about the fibers, and drawn to form a coupling region.

Abstract: A fiber optic polarization maintaining apparatus for use in fabrication of fused optical couplers, where the fused optical couplers include first and second optical fibers. The apparatus includes apparatus for holding the first and second optical fibers in a first predetermined alignment where the first and second fibers each include a stripped portion and where the stripped portions are held in contact along their length. Apparatus for heating the first and second optical fibers are located adjacent the holding apparatus wherein the heating apparatus is brushed across the length of the first and second fibers so as to oscillate across the fibers in an amplitude varied in an ever decreasing stepped manner until fusion of the fibers is complete.

Abstract: Fiber composites, particularly for imaging, easy to manufacture even with great cross-sectional area, in which fibers are in a peak-to-valley relation with abutting pairs of fibers throughout.

Abstract: The present invention relates to a method for the fusion splicing of carbon coated optical fibers and to a method for providing reinforced performance of the spliced points. Concretely, carbon coated optical fibers are fusion spliced in an atmosphere containing less than 0.5 vol % of oxygen without the removal of the carbon coating. In order to minimize the amount of damage to the carbon coating resulting from the fusion, the decline in the failure probability of the optical fiber is controlled by means of applying moisture to the spliced part or by means of the adhesion of the oxidized carbon gases to the optical fiber. On the other hand, the carbon coating layer which was removed by oxidation at the time of the fusion splicing is recoated by means of a CVD reaction using a laser as a heat source. By means of this, the decline in the fatigue characteristics of the spliced part can be controlled.

Abstract: To make a fused fiber coupler (1) which is especially suited as a pump coupler for use in fiber amplifiers, exhibits low sensitivity to polarization, and can be spliced in with low loss, commercially available single-mode fibers are employed. After completion of an elongating process and interruption of heat from a heat supply, the input-fiber pair (fiber ends 4, 5) and the output-fiber (fiber ends 6, 7) of two fused lengths of the fiber (2, 3) are twisted by 180.degree. about their common axis and fixed in this position.

Abstract: In a method of producing an optical fiber coupler, in which glass portions of a plurality of optical fibers are heated so as to be fusion bonded to each other and then, are heated so as to be stretched, the improvement comprising: a gas burner which acts as a heat source and has a plurality of gas nozzles arranged in an axial direction of the optical fibers so as to be fixed in position during heating of the glass portions.

Abstract: Substrates for supporting optical fibers in an optical coupler are made by, first, making grooves in a glass preform which are about ten times the desired size, and then using glass drawing techniques to draw from the preform a substrate of the proper size. Optical fibers are arranged in ribbon form and placed in a fixture which allows the ends to be cut and polished at the angle required for proper coupler operation. Fibers are stripped from the end of the ribbon that has been cut and polished and placed in the grooves for proper alignment with abutting fibers. The ends of the fibers that remain fixed to the ribbon prevent unwanted rotation of the fibers.

Abstract: The invention relates to a method of making multi-ferrules. It provides a method of making multi-ferrules from a vitreous material, the multi-ferrules having a series of cylindrical channels with parallel axes.

Abstract: The invention provides a method for producing an optical-fiber coupler with a preset branching ratio. The present invention relates to a method in which part of a plurality of optical fibers are made to closely contact with each other so as to form a coupler. The coupler is heated to thereby obtain a predetermined branching ratio; the flow rate of a gas to be supplied to a heat source is increased/decreased by a quantity proportional to a difference between the drawing speed and a preset drawing speed while predetermined tension is applied to the optical fibers.

Abstract: The present invention provides a manufacturing method for an optical fiber coupler, the optical characteristic of which is less dependent on wavelength. In the manufacturing method, a coupling region is formed by fusion-bonding and extending parts of a plurality of optical fibers arranged to be closely touching each other. At least one of the optical fibers is extended at a speed different from that of the other optical fibers when a low-temperature heat source is applied to soften the optical fibers. When the temperature of the low-temperature heat source is raised to form a high-temperature heat source, the extended parts of the closely touching optical fibers are fusion-bonded. When the temperature of the high-temperature heat source is then lowered to form a low-temperature heat source again, the fusion-bonded part can be extended further. In one embodiment, the fibers are twisted before fusion bonding the fibers.

Abstract: A catheter for delivering radiant energy, such as a laser beam, is used in a technique to controllably apply the radiant energy in a patient's body, such as in a blood vessel. The radiant energy is applied in a manner which erodes biological material and may be used to drill through vascular obstructions. The catheter emtis the radiant energy from its distal end in a pattern which defines a relatively small working region in which the energy density level is sufficiently high to remove the biological material. The energy disribution is substantially uniform across the beam. Distally beyond the working region, the energy density of the beam decays sharply so that biological material beyond the working region is not removed. Biological material is removed in very limited layer-like regions and in a manner in which a distally propagated segment of the beam will not have sufficient energy density to puncture the blood bessel wall.

Abstract: A method for manufacturing a fiber type coupler of the present invention by fusing and elongating a plurality of optical fibers is characterized in that a multi-wire optical fiber wire is used as the plurality of optical fibers.

Abstract: In a method of preventing twisting of a fusion-spliced optical fiber in the process of encasing the optical fiber in a casing, one of a pair of optical fibers is wound N turns in one direction to form a first coil. Another of the pair of optical fibers is wound N turns in another direction opposite to the direction to form a second coil. Ends of remainder portions of the optical fibers which are not wound are fusion-spliced to each other to form a fusion-spliced portion. The fusion-spliced portion is fixed within a casing. The remainder portions of the optical fibers are pushed into the casing to expand the first and second coils.

Abstract: An apparatus for fusion splicing optical fibers has one rotatable clamp mechanism that is manually operated and a second rotatable clamp mechanism that is operated by a motor. A three position stopper functions in the first position as a stopper against the optical fibers when the optical fibers are moved toward each other and in the second position as a mirror for reflecting an image of respective end faces of the optical fibers. A rapid fine adjustment of the alignment of the polarization maintaining optical fibers can be made.

Abstract: A method of splicing optical fibres is described in which at least one of the fibers has a high numerical aperture (NA) and the two fibres have different mode spot sizes. The method comprises fusing the ends of the fibres together with their cores in alignment and heating the fused junction between the fibres so as to cause dopant to migrate out of the core. The heating step is carried out for a time sufficient to achieve a predetermined level of matching between propagation modes in the two fibres.

Abstract: A method for fabricating a high efficiency optical coupler by matching the emerging light exit pupil from a coupler opening to the acceptance shape of a couple optical fiber. An excimer laser forms the coupler opening in an optical fiber by removing cladding from the optical core surface. The coupler opening has an elliptical shape resulting in an emerging light exit cone, and that exit cone matches an acceptance cone of a circular coupler optical fiber.

Abstract: A fiber optic coupler is formed by providing a glass tube having a longitudinal aperture extending therethrough. Protective coating is removed from a region of a first optical fiber intermediate the ends thereof. Protective coating is removed from an end region of at least one other optical fiber. The coated portion of the first fiber is threaded through the tube until the uncoated region thereof is near the tube end. The size of the aperture is insufficient for simultaneously receiving the coated portions of the first and second fibers in side-by-side relationship at the coated portion of both. The uncoated region of the second fiber is placed adjacent that of the first fiber, and both uncoated regions are simultaneously fed into the tube aperture.

Abstract: A method of producing an optical multi-fibre cable element provided with a secondary sheathing by extruding (1) a loose secondary sheathing (10) around a fibre bundle (9) and providing the fibres with a desired extra length with respect to the secondary sheathing. To avoid variation in fibre length in the production of cable elements the secondary sheathing (10) together with the fibre bundle (9) is twisted (12) around its axis after the extrusion step (1) at least to such an extent that the longitudinal sliding of the fibres with respect to each other is prevented in the twisted fibre bundle and that the stretching of the fibres in the fibre bundle at the step of providing the extra length (3; 18) is kept within the elastic range of the fibres.

Abstract: A method of fabricating an optical branching and coupling device includes the steps of preparing at least a pair of coated optical fibers; partly stripping the coating of the optical fibers; and fixedly inserting the coating stripped portions of the optical fibers into a pair of comb-shaped grooves under a condition prior to a unification step which is free from tension and torsional stress in an optical axial direction to bring the coating stripped portions into contact with each other between the comb-shaped grooves. The method also includes the steps of melting the coating stripped portions thus contacting each other by heating to unify the coating stripped portions and extending the coating stripped portions in the optical axial direction while in the melted state.

Abstract: A method disclosure for making an economical fiber coupler including providing a glass tube having first and second end portions and a midregion, and a longitudinal aperture extending through it. Two suitably prepared glass optical fibers, each having a core and cladding, are disposed within the longitudinal aperture, the fibers extending beyond each end of the tube. The fibers are glued to each end portion. The midregion of the tube is evacuated, heated, collapsed about the fibers, and drawn to reduce the diameter of the resulting composite.