Abstract: A process for the chemical vapor deposition of oxidic particles by oxidat of halides or halide mixtures wherein dinitrogen monoxide is used as the oxidizing agent. The reaction is carried out at comparatively low temperatures of between 900.degree. and 1150.degree. C., but results in high yields.

Abstract: Novel halide glass-forming compositions in the CdF.sub.2 -AlF.sub.3 -PbF.sub.2 and CdF.sub.2 -AlF.sub.3 -PbF.sub.2 -LiF composition fields are disclosed which exhibit unusual glass stability. The constituents of these glasses are potentially vapor transportable, so that very pure glass articles exhibiting excellent infrared transparency can be envisioned.

Abstract: A high temperature induction furnace (10) for drawing lightguide fiber (52) from a silica preform (44) has an axially located tubular zirconium dioxide susceptor (34) therein. Prior to use, at least a portion of the inside surface of the susceptor (34) is coated with a vapor deposited silica "soot" (54). The silica soot (54) is then consolidated at an elevated temperature. Surprisingly, such a technique substantially eliminates migration of zirconium dioxide particles from the susceptor (34) to the preform (44) and/or the fiber 52 without deleteriously affecting the susceptor (34) and/or the operation of the furnace (10).

Abstract: Optical fibers are coated under pressure to reduce the amount of bubbles entrapped in the coating and provide good coating concentricities. The fiber is drawn axially thru a thin-walled, cylindrical flow distribution sleeve which is located between a guide die and a sizing die. The sleeve contains a plurality of evenly distributed holes the number and size of which is such that radial flow of liquid toward the fiber is maintained over the entire length of the sleeve which is less than 1.27 cm.

Abstract: A method for producing an optical fiber, more particularly a process for producing a preform in the course of the production of the optical fiber, which comprises the steps of using converging light beams as a heating source, heating the end of a starting rod with such light beams and blowing the fiber material-producing gases to the heated portion of the starting rod to grow the preform. The invention also provides a process for producing a low-loss optical fiber wherein the attenuation of light is greatly improved by growing the preform under reduced pressure or by applying supersonic waves to the heated end of the starting rod. There is also provided a process for producing a grated index optical fiber wherein the preform is produced by providing a specific distribution character to the converging light beams and to the impurity concentration of the blown gas so that the impurity concentration distribution will differ along the direction perpendicular to the preform growing direction.

Abstract: Vitreous optical fibers are useful in an expanding number of technologies. A process, corresponding apparatus, and a hermetically sealed fiber of the above nature are disclosed wherein high energy ionized plasmas are used in a continuous production of a coated vitreous optical fiber. Drawn fibers are axially aligned by ambient gases discharging through high vacuum gas locks. These fibers are then continuously fed through a high energy plasma zone so that the surface of the drawn fiber is subjected to ionized bombardment. This provides plasma-milling of the fiber surface for improving the fiber strength and for superior bonding of subsequently applied coatings.In preferred practice, a vacuum zone is used to deposit, from a plasma ion source, a diamond-like elemental carbon film onto the moving fiber. Another plasma vacuum zone may be used to deposit, over the carbon film, a very thin film of a conductive elemental metal illustratively; tin, indium and aluminum.

Abstract: A method is disclosed for making an optical fiber by drawing a preform whose fabrication involves deposition of a glass on a substrate by means of a chemical reaction between gaseous reagents. According to the disclosed method, accurately controlled amounts of a gaseous reagent are produced by flash evaporating a metered flow of a liquid reagent. The disclosed method is of particular interest for the industrial production of optical fibers.

Abstract: A process for manufacturing a preform from which is drawn an optical fiber, the core of which comprises layers of different glass composition. In one embodiment, the known CVD process for making preforms is modified by halting rotation of the substrate tube while the tube is asymmetrically heated by a source that traverses the length of the tube. A vapor mixture flowing through the tube reacts only near that region of the inner surface of the tube that is being heated. This forms a longitudinal strip of glass particles. The flow of reactants stops, the tube is rotated, and it is traversed by heating means which heats the tube to a temperature sufficiently high to fuse the glass particles and forming a longitudinal strip of glassy material.

Abstract: A method of forming optical fibers with minimal contamination from ambient air is disclosed. In the inventive method a gas stream is introduced into a rotating structure by means of a rotating seal. The rotating seal comprises a rotating member seated within a stationary member. Counterflowing gases are flowed through the clearance region between the rotating and stationary members to prevent seepage of ambient air into the gas stream.

Abstract: A rod of silica 14 is inserted into a substrate tube 10 whose bore is lined with a layer 11 of material having a refractive index less than that of silica. This layer 11 is itself covered with a layer 12 of silica. The assembly of the rod and tube is drawn into fibre, or its components are fused together to form a solid cross-section optical fibre preform.

Abstract: A method for manufacturing silica-based optical fiber, and for manufacturing optical fiber preforms, the method comprising deuterium/hydrogen exchange in the silica-based material carried out subsequent to formation of the silica.

Abstract: A plasma process for the production of a dielectric rod 6 from gaseous starting materials, causes the rod 6 to grow in the axial direction by deposition on its end face. This is effected by conducting microwave energy via the rod 6 to its end face, this energy maintaining a gaseous discharge 7 at the end face. The starting material flows into this gaseous discharge as a gaseous jet by means of a concentric nozzle system 8.

Abstract: Various CVD processes are known whereby glass particles are flowed toward or over a substrate on which they are to be deposited. Because the substrate is cooler than the stream in which the particles are flowing, the thermophoretic force directs the particles toward the substrate. In accordance with the invention a beam of laser light is propagated over the surface in the vicinity of the stream of particles. The particles and/or a component within the stream absorbs the laser energy to induce within the stream of particles a temperature gradient whereby temperature increases with increased distance from the substrate surface.

Abstract: A method of producing a preform for a single-polarization optical fiber wherein a glass rod to become a core or a glass rod to become a clad is inserted into a quartz tube which has on its inner wall surface a glass thin film to become a clad layer, a glass thin film to become a jacket layer or glass films to become a jacket layer and a clad layer, and wherein under a state under which the internal pressure of the quartz tube is reduced, the quartz tube is heated to become solid, whereby at least one of the clad and the jacket of the optical fiber preform becomes elliptic in cross section.

Abstract: A preform for fabrication of a glass fiber optical transmission line is prepared by chemical reaction of vapor ingredients within a glass tube. Reaction, which may be between chlorides or hydrides of, for example, silicon and germanium with oxygen, occurs preferentially within a constantly traversing hot zone. Flow rates and temperature are sufficient to result in glass formation in the form of particulate matter on the inner surface of the tube. This particulate matter deposits on the tube and is fused with each passage of the hot zone. Continuous rotation of the tube during processing permits attainment of higher temperatures within the heated zone without distortion of the tube.

Abstract: The time required to collapse an OH-rich silica tube can be reduced significantly by subjecting the tube to a deuterium/hydrogen exchange prior to its collapse.

Abstract: In the manufacture of optical fiber having a core of a core material and a cladding of a cladding material by drawing the fiber from an optical glass preform, the preform is manufactured by reacting a first plurality of initial reactants in their vapor state to obtan core material particles, by producing a coherent core body from the core material particles, by reacting a second plurality of initial reactants in their vapor state to obtain cladding material particles, by providing a coherent porous cladding on the core body from the cladding material particles, and by sintering the resulting composite body to convert the same into the preform. The core body can either be sintered before combining the same with the porous cladding material, or it may remain in its initial porous state until the sintering of the composite body.

Abstract: A process for manufacturing a preform from which is drawn an optical fiber, the core of which comprises layers of different glass composition. Layers of glass, adjacent ones of which have different composition, are deposited on a substrate. A process is preferred whereby layers of glass soot are deposited. The soot is consolidated and the resultant laminated glass structure is severed to form an elongated azimuthally asymmetric laminated core structure. A layer of cladding glass is added to the core structure, and the resultant preform is drawn into an optical fiber.

Abstract: A process for manufacturing a preform from which is drawn an optical fiber, the core of which comprises layers of different glass composition. Layers of glass soot are deposited on the flat, longitudinally extending sides of a thin, elongated mandrel. Adjacent soot coatings have different refractive indices. A preliminary coating of cladding glass soot is deposited on the laminated soot structure. The resultant composite body is consolidated and stretched to form a rod or core structure upon which the final coating of cladding soot is deposited. The resultant composite body is consolidated and drawn into an optical fiber. In a modification of the this method, the mandrel is removed after the planar soot coatings and preliminary coating of cladding soot are deposited thereon. The resultant soot body is consolidated and processed as described previously.

Abstract: The invention relates to a process for producing ultrapure doped vitreous silica for producing a preform for optical fibres. According to the invention, an ultrapure porous glass, glass obtained after its shaping, is used as the crude starting material in a deposition process of the plasma torch, grain by grain Verneuil type, for example, in order to complete a preform obtained by said process for the separation of phases and acid washing or etching of the glasses.

Abstract: Optical fibres are manufactured by etching the inner wall of a tube. The tube wall is etched by passing a hydrogen-free fluorine compound through the tube while reciprocating a nonisothermal plasma through the tube. After etching, core glass is chemically deposited on the etched surface. The core glass is deposited from the gaseous phase while using a nonisothermal plasma for initiating the reaction. The inner-coated tube is then collapsed and drawn to form an optical fiber.

Abstract: A lightguide fiber preform is made by depositing optically suitable layers of doped silicon dioxide on an inner wall of a rotating glass substrate tube (31) which is exposed to a moving zone of heat during a deposition mode and during a mode when the tube is collapsed. During each of a plurality of passes of a torch assembly (50) in the collapse mode following deposition, a contact device (101) is in continuous engagement with the tube and is caused to apply forces to each successive increment of its length following exposure to at least an initial portion of the zone of heat to collapse incrementally the tube. Between successive ones of the plurality of passes, the contact device is moved inwardly of the tube so that each increment of length is exposed to forces which as between the successive passes are applied at points incrementally closer to the longitudinal axis (36) of the tube.

Abstract: Porous glass optical fiber preforms are conventionally formed by depositing many layers of glass soot on a mandrel, removing the mandrel, and heating the porous preform to form a consolidated glass article. To prevent the formation of a devitrified layer at the aperture-forming surface during the consolidation step, the rate of soot deposition is initially reduced so that a stratum of fine soot is initially deposited on the mandrel. The stratum is initially discontinuous, but after a plurality passes of the soot-producing burner, it becomes continuous. Thereafter, the formation of the remainder of the soot preform continues in a conventional manner.

Abstract: Concentrations of dopants are changed while forming a gradient index optical waveguide so that an optimal index profile is produced even though the relationship between concentration and refractive index is not linear. This is accomplished by varying the concentrations of the dopants as a function of the radial distance from the center of said core substantially as:C.sub.i (r)=C.sub.i .degree.+[(l-.xi..sub.i)(r/a).sup..alpha. +.xi..sub.i (r/a).sup.2.alpha. ]C.sub.i.sup.1where C.sub.i (r) denotes the concentration of the i.sup.th dopant as a function of radial distance r, C.sub.i.sup..degree. denotes the concentration at r=o of the i.sup.th dopant, C.sub.i.sup.1 is the total change in concentration of dopant's between r=o and r=a, .alpha. is the selected index profile, and .xi..sub.i are variable parameters relating the concentration of the i.sup.th dopant to radial distance r.

Abstract: An optical waveguide for a communication system includes a graded index core formed from at least three glass-forming compounds with a profile having at least two .alpha.-type index profile terms.The core has a refractive index which is n.sub.c at the center of the core and which varies as a function of the radial distance r from the center of the core substantially as: ##EQU1## where .alpha..sub.i is defined by: ##EQU2## .DELTA.=(n.sub.c.sup.2 -n.sub.o.sup.2)/2n.sub.c.sup.2, n.sub.o is the refractive index of said compounds at r=a,N.sub.c =n.sub.c -.lambda.dn.sub.c /d.lambda. where .lambda. is the wavelength of the light source, and the quantities .DELTA..sub.i are parameters which can be varied provided the condition ##EQU3## is satisfied.

Abstract: A preform from which lightguide fiber is drawn is made by depositing optically suitable layers of doped silicon dioxide on an inner wall of a rotating glass substrate tube which is exposed to a moving zone of heat during a deposition mode and during a collapse mode. During at least a first pass following the deposition mode, a contact device is caused to engage each successive increment of length of the tube during exposure to the zone of heat. The contact device causes any sagged or offset portions of the tube to be reconfigured and causes the tube to have a central longitudinal axis which is a straight line which extends between stocks of a lathe by which ends of the tube are supported. The contact device may also be used to cause the tube to have a predetermined configuration along its length.

Abstract: A technique for fabricating a lightguide soot-boule. Gaseous reactants are directed through an inner tube of a torch having a plurality of coaxially aligned tubes. A glassy soot is formed at the output of the torch by a flame hydrolysis reaction and at least a portion of the soot is deposited on a forming soot-boule. The inner tube may be axially moved during the soot deposition process to alter or maintain the refractive index of the boule.

Abstract: A waveguide and method of making the same is disclosed which comprises an elongated dielectric core surrounded by dielectric shell at least one of which have an anisotropic index of refraction. The core is made up of a plurality of layers each having a parallel surface normal with pairs of such layers having unequal indices of refraction. The layers are selected to preferably have the same thickness.

Abstract: A torch (24) used in the Vapor-phase Axial Deposition (VAD) process to form small diameter cores for single mode lightguide preforms. The torch (24) is comprised of a plurality of concentrically mounted, spaced, glass tubes (62, 63, 64, 65, 66) through which reactants and combustible materials are passed. A tapered shroud (68) is mounted about the end of the torch (24) and a shield gas directed along the inner surface thereof to confine and direct the gases and reactants to the surface of the soot form (12).

Abstract: The invention relates to an apparatus for producing a preform for constituting an optical fiber. This apparatus essentially comprises a glass maker's lathe and a motor which holds and rotates a hollow silica tube, a torch making it possible to heat a cross-section of the tube and which can be translated along the tube and means for supplying the gaseous compounds consisting of silicon chloride, oxygen and doping agents decomposing under the action of the heat. Part of the products obtained is deposited on the walls of the tube. The supply means comprise a pipe entering the tube in axial manner and at the end of which are provided two radially directed arms, which terminate with an outlet normal to the pipe and arm, said pipe moving in translation integrally with the torch.

Abstract: A glass optical waveguide preform is formed by depositing first and second coatings of glass soot on a mandrel. The characteristics of the first coating are such that it can ultimately form the core of an optical fiber. The core-clad diameter ratio of the preform is greater than that necessary to provide the desired core-clad diameter ratio of the resultant fiber. The mandrel is removed and the porous preform is consolidated. The preform aperture is etched, rinsed and dried. One end of the preform is heated and pinched to close the aperture. The aperture is evacuated, and the remaining end of the preform is heated, the corresponding end of the aperture being caused to close. An intermediate fiber is drawn from the resultant consolidated preform, the entire aperture being closed during drawing due to the low pressure within the aperture. The intermediate fiber is severed into sections, each of which functions as a mandrel for the deposition of a further coating of cladding soot.

Abstract: A method for producing an optical multiple fiber, which comprises bundling a multiplicity of silica glass light-conducting elements and drawing the bundle of the light-conducting elements in the state that a liquid intermediary material (comprising at least one member selected from the group consisting of glass forming oxides, glass modifying oxides and intermediate oxides) exists among the elements; thereby providing a multiple fiber excellent in image-transmitting capacity and image-resolving power, by fusing together a multiplicity of silica glass light-conducting elements with each other in drawing to prevent the occurrence of bubbles.

Abstract: Vapor deposition of doped silica in a reaction chamber on a rotating supporting surface, in the manufacture of a preform for the drawing of an optical fiber, is accompanied by the continuous admixture of deuterium with a flow of carrier gas, specifically oxygen, by which the reactants are transported to the reaction chamber. An isotopic substitution of deuterium for the hydrogen of hydroxyl groups in the reaction products shifts the major absorption peaks to wavelengths outside the minimum-attenuation range of 0.7 to 1.6.mu. used for fiber-optical signaling. The proper ratio of deuterium to carrier gas is maintained with the aid of a mixer having two compartments separated by a perforated diaphragm or a thin metallic foil, one compartment being connected to a deuterium tank while the other communicates with a conduit through which the vapors entrained by the carrier gas pass to the reaction chamber.

Abstract: Hydroxyl free deposition with high efficiency and at a high deposition rate may be achieved, even with use of relatively inexpensive raw materials, by utilizing a ring-shaped plasma activated axial chemical vapor deposition obtaining 100% chemical conversion and fractional volatilization of impurities. The plasma is induced in an annular stream of a plasma-forming gaseous medium, and the reactant or reactants used in the axial chemical vapor deposition are introduced into the center of the ring-shaped plasma to be converted by the heat of the plasma flame into soot which is deposited on a bait. An annular stream of a cooling medium flows outwardly past the plasma flame and is circumferentially centered by an extension of the outer tubular element of a plasma torch in which the plasma is generated. An RF generator which induces the plasma is operated at a frequency exceeding 20 MHz to give the plasma flame the desired ring-sloped configuration.

Abstract: An exhaust system (3) for a vapor-phase axial deposition (VAD) system (5) is comprised of the serial combination of an exhaust tube (26), an outlet pipe (27), a soot collection chamber (32) and a discharge line (34). The exhaust tube (26) has a constricted central portion (48) and a flared intake (44) with a gradually turned back end (46).

Abstract: A vapor-phase axial deposition system (5) for fabricating a lightguide soot boule (16). The system (5) is comprised of a short cylindrical housing (10) having end plates (26--26) affixed thereto. A starting member (58) is radially directed into the central portion of the housing (10) and a torch (12) is activated to direct a stream of glassy soot thereat. The member (58) is simultaneously rotated and withdrawn from the housing (10) as a cylindrical, porous, soot boule is formed on the end thereof. The housing (10) having a substantially two-dimensional character eliminates secondary gas flow within the housing (10) resulting in enhanced deposition rates and repeatability.

Abstract: Selected portions of the interior surface of a substrate tube, or of the cladding or core layers deposited on the interior surface of the substrate tube, are treated by one or more process steps such as shaping, diffusing, leaching, or depositing. Patterning processes such as photolithography and lift-off are employed to define the selected portions. The resulting core and/or cladding layers of the fiber can be made to have a variety of geometric shapes and composition profiles useful, for example, in realizing birefringent fibers and multiple-core fibers. Also described is the similar treating of metal layers and the incorporation of such layers into the fiber.

Abstract: A glass layer is formed inside a silica glass tube and another glass layer having a refractive index higher than that of the abovementioned glass layer is formed on said glass layer. After these glass layers are formed, one end of the glass tube is collapsed. While the internal pressure of the glass tube is being reduced below the atmospheric pressure, the glass tube is caused to collapse by heating, thereby yielding a preform for an optical fiber. The optical fiber produced from this preform has the difference in the refractive indices of the two orthogonal major axes of at least 1.6.times.10.sup.-4 and maintains the linear polarization plane.

Abstract: Halides of Si and Ti, B, P, or Ge and oxygen or steam are introduced into a reaction vessel and heated in a vapor phase to form fine glass particles by oxidation or hydrolysis. The fine glass particles are deposited on a substrate. The deposited fine glass particles are heated and vitrified into a transparent glass layer, which is etched to form a core having a desired pattern by a reactive sputter etching process using Freon gas. The core is coated by a clad. In a waveguide thus formed, the cross sectional configuration and dimensions of the core layer and the refractive index difference are precisely controlled. The waveguide is manufactured with good reproducibility. The fabrication method is suitable for mass production of waveguides. An expansion coefficient transient layer is provided between the core layer and the substrate to prevent a crack in the waveguide.

Abstract: A process for producing an optical fiber preform in a muffle furnace by hydrolyzing a gaseous glass forming material with a flame from an oxyhydrogen burner and depositing the resulting soot in a rod shape and an apparatus therefor are described, wherein a gas is supplied to the muffle furnace other than from said burner, and the volume supply of said gas is held constant by controlling the amount of a control gas supplied into an intermediate portion of an exhaust pipe through which the gases formed in the muffle furnace and the fine glass particles that do not deposit in a rod shape are discharged.

Abstract: There is described a method of producing a rod-shaped base material for an optical transmission fiber which has the steps of advantageously measuring the refractive index distribution of the transparent glass rod obtained. The method contemplates heating and sintering the glass soot unit before the step of covering quartz glass material onto the transparent glass rod and removing the outer peripheral part of the transparent glass rod in which the value of the refractive index is largely displaced from a reference in a predetermined range. The rod-shaped base material thus produced exhibits very wide band width transmission characteristics.

Abstract: A process and apparatus for producing an optical fiber preform by oxidizing a gaseous glass forming material with a flame from a burner and depositing the resulting soot in a rod form are described, wherein two signal beams, supplied by splitting a light beam, are projected in a direction normal to the direction in which the preform grows and are directed into the space between the burner and the deposition face of the preform, and they are positioned so that one beam partially contacts the deposition face of the preform, while the other beam is directed to pass between the burner and the deposition face, and the distance between the burner and the deposition face is controlled such that the ratio of the intensity of the two beams passing through the space between the burner and the deposition face is held constant.

Abstract: High-silica glasses are formed by sintering a dried gel at temperatures below the liquidus. The gel may be formed by mixing colloidal silica particles or silica-containing liquids with appropriate liquids. Fragmentation of the gel during drying is advantageously avoided by redispersing the dried gel or sol in a liquid to yield a colloidal suspension which is then gelled, dried, and finally sintered below the liquidus.

Abstract: In the manufacture of a glass optical fibre preform by forming a coating of oxide material on the interior surface of a substrate tube, in particular a coating of silica and one or more dopant oxides on a vitreous silica tube, by causing a reaction to take place between oxygen and the vapor or vapors of one or more compounds such as halides, the reactant vapors are introduced into a perforated tube supported coaxially within the heated substrate tube and pass through the perforations into the annular space between the perforated and substrate tubes, while oxygen, and optionally an additional carrier gas, is passed either into the perforated tube or directly into said space. The coating-forming reaction is caused to take place in said space by generating energy in the space, in the form of a plasma, or a laser beam, and/or heat, and/or gas combustion, whereby the coating is formed simultaneously on the whole heated length of the substrate tube.

Abstract: A process for manufacturing a glass tube, comprising at least one doped silica layer, wherein the layer is formed by forming a gel in situ, by the atomization of a hydrolyzing agent, onto a layer of a gelable liquid containing an alkoxy silane on a cylindrical mandrel rotated in a centrifuge, the gelable liquid and/or hydrolyzing agent containing a doping element, whereafter the resulting gel layer is subjected, after the withdrawal of the mandrel, to at least one thermal treatment to dry the gel and convert it into doped vitreous silica. The process can be applied to the production of preforms for the manufacture of optical fibers.

Abstract: The method of the invention provides a thin film deposit of a binary glass for use in integrated circuits which binary glass has a softening or flow point far below temperatures at which glasses normally used in connection with integrated circuits flow. After the binary glass has been deposited (on a semiconductor substrate), it is heated and reflowed. Preferably the glass comprises a mixture of germanium dioxide and silicon dioxide wherein the germanium dioxide is no greater than approximately 50 mole percent of the mixture. Phosphorus is added to the glass film for passivation of the underlying devices.

Abstract: Manufacturing method of doped silica glass suitable for optical fiber wherein quartz powder or SiO.sub.2 glass fine particles are exposed to a gas for producing the doped silica glass containing SiCl.sub.4, a gaseous additive and water vapor (H.sub.2 O) to add the dopant to the glass body, and then the resulting glass body is fused at a high temperature, thereby producing a transparent doped silica glass in which the production of the glass particles, the addition of the dopant, and the vitrification of the glass body are carried out by separate steps under respective suitable conditions. The manufacturing speed is remarkably increased because of the separate steps. The content of the dopant is not limited, but can be adjusted with any desired amount by changing the reaction time of dissolution. Dopant components like PbO.sub.2, SnO.sub.2, ZnO which were typically not added to the glass body can now be added thereto.

Abstract: A process for producing a porous optical fiber preform by hydrolyzing a gaseous glass forming material with a flame from an oxyhydrogen burner and depositing the resulting soot in a rod form in a muffle furnace is described, wherein the muffle furnace is supplied with a gas other than that from the oxyhydrogen burner, and said gas is maintained at a constant temperature.

Abstract: A glass tube is formed having a mean cross-sectional tube wall area less than a preselected mean cross-sectional area. Additional glass differing in composition from that of the glass tube, but having an index of refraction substantially equal to that of the glass tube, is then fused onto a surface of the tube by vapor deposition, outside vapor-phase oxidation or outside vapor-phase axial deposition until the tube wall obtains the preselected mean cross-sectional area.

Abstract: A collimated laser beam focuses on a substrate put in a reaction vessel which includes glass raw materials to raise the temperature high enough for the thermal reaction of the glass raw materials to form a glass layer. The repeated scanning of the glass substrate with the laser beam accumulates a plurality of layers and forms an optical waveguide on the glass substrate.