Abstract: A method of producing polarization-maintaining single-mode optical waveguides is provided wherein the preform from which the optical waveguide is produced consists of a tube, a rod of core and cladding material centrally disposed in said tube, and two differently doped pairs of filler rods disposed about said rod, the two rods of each pair being disposed diametrically opposed to each other with respect to said rod. Maximum polarization maintenance of the optical waveguide being produced is achieved by choosing the diameter ratios so that each filler rod rests against the central rod, against the inside wall of the tube, and directly against the two filler rods of the respective other pair.

Abstract: In an optical fiber based on silicon dioxide with fluorine doping which determines its refractive index profile, at least in the light transmitting core a substance is added that increases the thermal expansion coefficient. The added substance is uniformly distributed at least in the light transmitting core, and reduces the influence of the drawing force F.sub.Z (during drawing of the preform) on the Rayleigh scattering .alpha..sub.R and the wavelength-independent "c term" losses. Even at high fluorine dopant concentrations, low Rayleigh scattering losses in the range of the material-intrinsic losses pure for silicon dioxide are achieved. The OH-contamination level is also further reduced, and cracks in the collapsed preforms are largely avoided.

Abstract: In the manufacture of high quality optical fibre for telecommunications, a preform (1) is advanced towards a furnace (9) until a tip detector (5) automatically stops the preform (1) at a predetermined position (11) in front of the furnace to provide a reference datum for a second mode of operation in which the computer (12) can be initiated manually (12B) to advance (4) the preform (1) by a predetermined amount into the furnace to commence drawing the optical fibre. Preferably the tip detector is a paddle (6) pivotally mounted (7) and operates an optical sensor (8).

Abstract: A low loss fiber optic coupler is fabricated by forming a coupler preform having a plurality of spaced glass cores extending longitudinally through a matrix of glass having a refractive index lower than that of the cores. The preform is heated and stretched to form a glass rod which is then severed into a plurality of units. Heat is applied to the central region of each unit while the ends of the unit are pulled apart to elongate and taper inwardly the heated central region, whereby the cores of the unit are more closely spaced and are of smaller diameter at the central region than they are at the ends of the unit. The unit is then provided with a plurality of optical fibers, one of which extends from each of the cores at the endfaces of the unit. A preferred method of providing the optical fibers involves forming the coupler preform of a matrix glass that is easily dissolved in a solvent.

Abstract: An improved process for the production of optical fiber porous preforms of predetermined refractive index distribution by the vapor-phase deposition method is disclosed wherein a glass material and a dopant material are subjected to flame oxidation by the use of an oxyhydrogen burner to form fine glass particles which are deposited on one end of a supporting rod adapted to move apart from the oxyhydrogen burner while rotating to allow a rod-like porous preform to grow thereon. The improved process is characterized in that the correlation between the shape of the deposition face and the refractive index distribution is previously determined mathematically, and on a basis of the correlation therebetween, a process variable such as the distance between the porous preform and the burner is adjusted to produce the desired shape of the deposition face whereby there can be obtained an optimum refractive index distribution.

Abstract: A rod-in-tube method for producing a glass preform for use in the fabrication of an optical fiber, which comprises steps of inserting a glass rod constituting a core material in a glass tube constituting a cladding material, heating the rod-tube composite by an outer heating source with introducing, in the gap between the rod and the tube, a gaseous mixture containing a silicon halogenide, a fluorine-containing compound and oxygen gas in which a ratio of silicon and fluorine (Si/F) is larger than 1/300 and smaller than 1/5, and heating and fusing the composite at a temperature not lower than 1,900.degree. C. with filling the gap by a gaseous mixture comprising a halogen-containing compound and oxygen gas; from which glass preform, an optical fiber with low attenuation of light transmission, particularly in a long wavelength range, is fabricated.

Abstract: In the process for applying a protective plastic coating to a glass optical waveguide fiber by the application of a curable liquid coating material thereto and the subsequent curing of the liquid coating to a protective plastic layer, the surface of the glass optical fiber is conditioned prior to the application of the liquid coating material thereto by replacing air adjacent the fiber surface with a selected gas preferably exhibiting high solubility in the liquid coating composition and resisting bubble formation in the liquid coating layer as it is formed.

Abstract: A method for producing ultra-high purity, optical quality, glass articles is disclosed which involves: (1) forming a gel from a silicon-containing organic compound, such as, TEOS; (2) drying the gel to produce granules having a mean particle size of less than about 1 millimeter; (3) fully sintering the granules to produce high purity, artificial sand; (4) casting the artificial sand by conventional techniques, such as, slip casting, to form a high density, porous, green body; (5) drying and partially sintering the green body; (6) fully sintering the green body under vacuum; and (7) hot isostatic pressing ("hipping") the green body. The glass articles produced by the process have higher purity, greater homogeneity, and less IR absorption than existing, commercially available, premium quality, fused silica, glass articles.

Abstract: A sol-gel process for preparing dimensionally precise tubular silica glass articles wherein a solution having a specific gravity higher than the specific gravity of the sol solution is placed in a cylindrical container with the sol solution is provided. The container is rotated around its axis and the high specific gravity solution becomes aligned adjacent the inner wall of the cylindrical container due to the effect of centrifugal forces acting on the high specific gravity solution. The sol solution becomes aligned adjacent the inner surface of the high specific gravity solution. The tubular wet gel formed from the sol solution has a uniform thickness and a highly precise round cross-section. The dimensional precision of the wet gel is maintained by rotating the wet gel during drying in order to prevent warping.

Abstract: A method of improving device performance of optical devices formed in optical substrates is disclosed. The method requires that the optical substrate material, for example, lithium niobate, be pre-annealed to form a surface layer with a known congruent composition before diffusing the waveguide material into the substrate. It has been determined that the composition of optical substrates can vary from boule-to-boule, or even along the length of a given boule. These variations affect the diffusion rate of the waveguide material and result in varying mode sizes (both width and depth of the mode). By pre-annealing all material, the diffusion rate will remain relatively constant, regardless of the particular boule. The pre-annealing can be accomplished either by pre-equilibrating the lithium niobate in a vapor-phase equilibrating crucible containing pre-reacted lithium niobate cullet with the desired composition, or pre-equilibrating the lithium niobate to the Li.sub.2 O-rich phase boundary in a two-phase (LiNbO.

Abstract: Control of speed and uniformity of the heating of the working zone of the preform in a glass drawing operation in which the softening heat is applied by forced convection (13), using a separate fluid heating zone to introduce temperature and velocity controlled fluid. The size of the working zone is further controlled by changing (18) the configuration of a movable exit sleeve. Uniformity and accuracy of temperature is enhanced by normalization (10) of the temperature of the preform close to a preselected value before the preform enters the furnace.A glass drawing apparatus embodies the preferred means to carry out the process, providing a two-chamber furnace having an air heating chamber (44) connected by air delivery channels (51) to a drawing chamber (43). The drawing chamber has preform inlet (41) and a drawn product outlet (56). Each of the latter preferably has an adjustable opening diameter. The inlet is provided with a pre-cooling collar (35).

Abstract: The disclosed method of producing optical fiber comprises providing a silica-based glass rod of diameter D that comprises a core region of effective diameter d surrounded by cladding material (D/d typcially>2) and a silica-based porous jacketing tube, inserting the glass core rod into the porous tube, consolidating the porous material and sintering the jacketing tube onto the core rod such that a substantially pore-free optical fiber preform results. Fiber is then drawn from the preform in the conventional manner. Consolidation and sintering is carried out at a temperature below the softening temperature of the material, typically <1600.degree. C. In a preferred embodiment, the porous tube is produced by a sol/gel process that comprises mixing colloidal silica (surface area 5-100 m.sup.

Abstract: A low loss fiber optic coupler is fabricated by forming a coupler preform having a plurality of spaced glass cores extending longitudinally through a matrix of glass having a refractive index lower than that of the cores. The coupler preform is formed by inserting a plurality of coated optical fiber preform rods into an aperture extending axially through an elongated boule of relatively etchable matrix glass. The cladding portion of the rods, which is relatively etch-resistant, is coated with a layer of etchable glass. The coupler preform is heated and stretched to form a glass rod which is then severed into a plurality of units. Heat is applied to the central region of each unit, and the central region is elongated and tapered inwardly. When an end of the unit is immersed in acid, the matrix glass dissolves, thereby leaving the unit cores and surrounding etch-resistant cladding glass protruding from the newly formed endface of the unit.

Abstract: Optical waveguide having a fused silica core and a fluorine doped silica cladding is made by heating a cylinder of silica in fluorine, the cylinder initially having an outer annular particulate or porous region which is dried by the fluorine and into which fluorine diffuses to lower the refractive index of the silica when fused. The cylinder is made by depositing particulate silica onto a mandrel, drying the silica in chlorine, and heating the silica to densify it. Further particulate silica is deposited and is then heated in a fluorine-containing gas to dry, fluorine diffuse, and sinter the porous outer part of the silica. The resulting tubular silica preform is heated to collapse the tubular preform into a rod from which optical waveguide is drawn, the waveguide having a fluorine doped silica cladding.

Abstract: Certain dopant materials, when present in a significant power-carrying portion of a silica-based optical waveguide fiber, are effective as intrinsic loss-reducing agents; the concentration of such dopant materials is at significantly lower levels as compared with levels used for producing a refractive index difference. Suitable in this respect are germania and phosphorus pentoxide as added to essentially pure silica or to silica containing other dopant additives such as, e.g., alumina or fluorine as may be used in a waveguiding core-cladding structure. Intrinsic loss in the vicinity of 0.2 dB/km is readily realized.

Abstract: A composite reinforcing element, especially a reinforcing cable, having a core consisting of a thread of non-metallic material and being coated in a reinforced polymer, and a process for producing it.

Abstract: The disclosed simple, economical and rapid sol-gel process for forming a silica-based glass body, termed the "vapogel" process, comprises introduction of a silicon halide-containing gas (e.g., SiCl.sub.4 +O.sub.2) into an aqueous medium. The thus formed sol can gel within minutes, resulting in a monolithic gel from which particles having a narrow size distribution can easily be formed. The thus formed particles can be used to produce a glass body such as an optical fiber. Various techniques for forming the glass body from the gel are disclosed. Among the many advantages of the vapogel method are its ability to produce very homogeneous mixed oxide glasses of composition not obtainable by prior art sol-gel processes, and the advantageous mechanical properties of the gel produced by the method. The latter makes possible, inter alia, formation of particles having a relatively narrow size distribution.

Abstract: There is provided by this disclosure a method and apparatus for making fiber optic couplers that is comprised generally of the steps of stretching a fused optical fiber pair at a predetermined rate to produce first a tapered section, second a constant diameter cylindrical section, and third a final tapered section. The two optical fibers are placed in juxtaposition under a predetermined load, heated to a predetermined temperature until they fuse together to form a single entity having a predetermined width, length and circular cross section. The two moveable platforms apply a predetermined tensile load to the fibers and move the fibers past a heat source in a controlled manner to form the different sections.

Abstract: A method for manufacturing hollow core optical fibers is disclosed comprising continuously feeding a glass rod of the desired cladding composition into a high temperature furnace with the rod in line contact with the inner surface of the glass tube. The glass transition temperature of the rod is substantially lower than the glass transition temperature of the glass tube. The glass rod composition is uniformly distributed on the glass tube inner wall as it enters the furnace hot zone. The ratio of the rod diameter to the glass tube inner diameter and the drawing temperature determine the coating thickness of the glass cladding on the inner surface of the glass tube. As the coated tube is passed through the furnace hot zone peak, the optical fiber is drawn. The rod and tube feed rate, the drawing temperature of the rod and glass tube and the drawing rate of the coated glass tube are selected to yield a hollow core optical fiber, with preselected interior and exterior diameters.

Abstract: The speed at which optical fibers can be drawn and coated is significantly increased by efficiently stripping the gas boundary layer entrained by the moving fiber. The stripping is periodically repeated to ensure that the entrained flow is not re-established.

Abstract: Polarization beam splitters/combiners or polarization insensitive beam splitters/combiners are manufactured from low or zero birefringence single mode optical fibre, rather than high birefringence fibre, by using a differential pulling technique to induce the appropriate amount of form birefringence, the fibres being stretched further than hitherto.

Abstract: A method is provided of manufacturing a device for conducting quantized particles such as photons and electrons. The method comprises the following steps:providing a layer of magnetizable material throughout the length of a conductor;dividing the conductor into conductor pieces having a predetermined length;aligning the conductor pieces by means of a magnetic field in such a manner that their ends are positioned perpendicularly to an abutment face;bundling the conductor pieces to a dense packing; andjoining the bundled conductor pieces to a mechanical unit.The method is preferably carried out in such a manner that the abutment face extends substantially perpendicularly to the direction of the gravitational field and that the attraction caused by the magnetic field is greater than and opposed to the force of gravity caused by the gravitational field.

Abstract: A method of manufacturing glass bodies, in which the starting material for the glass body, being monodispersed SiO.sub.2 particles (quartz-glass powder), is used to form an open-pore green body which is subjected to a purification process in which the impurities present in the green body react with a purifying gas which is heated to a temperature in the range from 600 to 900.degree. C., after which the green body is sintered, in which a two-stage heating-purification step is used, such that in the first stage SiO.sub.2 particles are heated until they are dense-sintered, i.e. they have no more micropores, and in the second stage the homogeneous open-pore green body formed from the dense-sintered SiO.sub.2 particles is purified in a known manner in the purification gaseous atmosphere and subsequently sintered.

Abstract: The invention provides an optical glass fibre having a synthetic resin coating and a method of manufacturing same, the first layer of the synthetic resin coating being formed from a curable polyether urethane acrylate composition.The glass transition temperature of the synthetic rubber formed after curing is reduced to -50.degree. C. or lower by increasing the molecular weight of the polyether urethane acrylate and, if necessary, by using aromatic instead of aliphatic urethanes. During coating the viscosity is low due to the presence of monofunctional acrylates of low viscosity. The curable synthetic composition exhibits a high curing rate.

Abstract: It is disclosed that a radiation-resistant optical conductor, such as an optical fiber for telecommunication, a multiple fiber for an image scope, and a light guide for illumination, which comprises a core composed of a pure silica glass which is prepared via an ultrahigh temperature of at least 3,000.degree. C. and has an OH group content of from 0.1 to 300 ppm, and a cladding layer formed on the core, and the cladding layer being composed of a silica glass which contains boron element and fluorine element as a dopant.

Abstract: The process employs solid-state halides heated at high temperature, under pressure conditions necessary to their vaporization, and obtains their condensation to a solid state on the internal surface of a glass tube, which, after collapsing, forms the preform.

Abstract: A method of manufacturing rotationally symmetrical glass bodies. The starting material for the glass body is a thixotropic suspension consisting of powered glass in a liquid dispersing agent. The suspension is introduced into a hollow mold whose geometry corresponds to that of the glass body to be formed. The hollow mold is rotated about its longitudinal axis to deposit the suspension on the inner wall of the hollow mold. The after which the green body thus formed is purified and sintered. The green body is formed by heating the rotating mold and the suspension therein to a temperature below the boiling point of the dispersing liquid until cross-linking and solidification of the starting material is obtained. Thereafter, the green body can be removed from the hollow mold.

Abstract: An optical fiber contact for terminating an optical fiber includes a memory tube material having a first section which has been recovered around a pigtail optical fiber. A second section of the memory material is nonrecovered, and an optical fiber is terminated by inserting a cleaved or polished end of the optical fiber into the nonrecovered tube section and recovering this tube section around the cleaved or polished optical fiber end. A plurality of contacts are disposed in first and second linear arrays which are then optically interconnected with an optical fiber contact assembly.

Abstract: Manufacture of optical fibre preforms. A material such as Si, Ge and B.sub.2 O.sub.3 is evaporated in vacuo into a silica tube and is made to condense therein as a viscous liquid which is then oxidized. The operation may be repeated several times with different materials. In this way the tube is clad from within in such a way that the optical index of refraction increases from the periphery inwards. Upon completion of the cladding the tube is collapsed into a rod which is then used for drawing optical fibres.

Abstract: A method and a device for applying a primary coating to an optical filament. In order to make the distribution of the coating material even, the flow of the coating material to be introduced into the crucible is divided in the crucible into two flows opposite in direction and advancing in the peripheral direction of the crucible. The two flows are caused to flow in the axial direction substantially at the opposite sides of the crucible. The axial flows are caused to flow in the peripheral direction of the crucible and joined by means of an outer channel extending around the crucible in the peripheral direction thereof. The flow is passed radially through throttle openings into an inner peripheral channel and further through a peripheral throttle slot into a conical channel along which it is led into a central chamber of the crucible, through which chamber the filament is drawn.

Abstract: A single-mode optical fiber transmission line suited for coupling to another fiber through a laterally coupled splice includes a core having a selected diameter, a cladding layer that surrounds the core and has a cladding thickness between one and two core diameters, and an auxiliary cladding into which the optical fiber is nested. The auxiliary cladding has an index of refraction not substantially greater than that of the cladding layer that surrounds the core, an inside dimension greater than that of the outside dimension of the optical fiber, at least partially surrounds the optical fiber and is attached to the optical fiber at least along one lineal connection zone.

Abstract: A device for transferring the energy emitted by a high power laser onto a target characterized in that it comprises two guides of optical fibre having step index refraction distribution and at least a plastic material coating. The first guide, stiffly coupled to the laser source, is a variable section fibre with an input face of larger diameter. Guide is the second one by a uniform or variable section fibre with a larger diameter near the output terminal. The two guides are joined by a low leakage optical fibre connector, and between them an adapter can be interposed if the output section of the first guide of fibre does not coincide with the input section of the second guide of fibre. The variable section fibre can be drawn from a pre-moulded or melted material, with the speed controlled by an electronic circuit. Different kinds of pots can be utilized in order to obtain the fibre plastic coating.

Abstract: The method allows surface defect reduction in silica optical-fibres by enriching the external layer by silica bonded carbon atoms within the silica network: SiC.SiO.sub.2. Carbon is obtained from chemical reaction directly during the drawing step.Volume defects are reduced by rapidly cooling the fibre structure heated up to vitrous transition temperature.The apparatus allows the method to be carried out during drawing step.

Abstract: A lead phosphate glass to which has been added indium oxide or scandium oe to improve chemical durability and provide a lead phosphate glass with good optical properties.

Abstract: A method of manufacturing a passive fiber optic component, in which two or more fibers are each bared at one end by removal of the outer coating of the fiber the bare portions of the fibers are etched to produce a cylindrical end portion which adjoins a conical portion. Subsequently, the fibers (1) are arranged with their etched portions in a capillary tube which is sealed at one end. The tube is then evacuated and is fused with the etched portions of the fibers to form a solid rod with a rotationally symmetric distribution of the end portions of the fibers. The fibers are etched to such a diameter that after fusion of the fibers with the tube, the fused fibers ends have a circular cross-section substantially equal to the cross-section of a single fiber core. An end face is formed on the rod by cleaving or by grinding, and by polishing to obtain a fused fiber head.

Abstract: A method of and arrangements for manufacturing glass bodies, in which method a thixotropic suspension, being the starting material for the glass body, is used to form a porous green body which is subsequently subjected to a purification step in a heated gaseous phase and then sintered to form a glass body, the starting material being homogenized and liquefied in a closed elastic mould by subjecting it to sound or ultrasonic, after which the liquid starting material is given the shape of the glass body to be formed and then solidified.

Abstract: An optical fiber comprising a core essentially made of quartz and a cladding made of fluorine added quartz is fabricated with good productivity from a glass preform produced by a method comprising maintaining a hollow cylindrical porous glass preform in a first high temperature atmosphere comprising at least one fluorine-containing compound with jetting a cooling gas through the central hollow part of the porous glass preform to grade the amount of fluorine to be added in the radial direction of the porous glass preform and then sintering the porous glass preform in a second high temperature atmosphere kept at a temperature higher than the first high temperature atmosphere to make it transparent.

Abstract: A method of and arrangements for manufacturing glass bodies, in which the starting material for the glass body, being an anhydrous suspension having a microdispersed solids content, is used to form a porous green body which is subsequently purified and sintered, in which by separating the phases of an anhydrous suspension the green body is formed by means of electrophoresis on a deposition electrode whose shape corresponds to that of the glass body to be produced.

Abstract: Method and equipment for the manufacture of glass bodies wherein a porous green body is formed by extrusion from the starting material for the glass body in the form of a plastic mass and this green body is then purified and sintered, the plastic mass being transformed into a state of reduced viscosity by the application of mechanical forces utilizing the thixotropic effect and being extruded in this state.

Abstract: Method and equipment for the manufacture of glass bodies with which a porous green body is formed from the starting material for the glass body in the form of an aqueous suspension with highly disperse solids content and this green body is then purified and sintered, the green body being deposited by separation of the phases of the suspension by electrophoresis.

Abstract: A method of and arrangements for manufacturing glass bodies, in which the starting material for the glass body, being a suspension having a microdispersed solids content, is used to form a porous green body which is subsequently purified and sintered, in which, by separating the phases of the suspension in an arrangement in which a pressure difference can be built up, the green body is deposited on a porous membrane whose shape corresponds to that of the glass body to be produced, the pores of the membrane having a diameter in the range from 1 to 500 times the average particle diameter of the solids content of the suspension.

Abstract: Method and equipment for the manufacture of glass bodies in which a porous green body is formed from the starting material for the glass body in the form of a thixotropic suspension, is dried, purified and then sintered, during which process the starting material is transformed into a state with minimum viscosity and homogenized by the introduction of mechanical forces, is poured in the low-viscosity state into a mould of hydrophobic material corresponding to the shape of the glass body to be manufactured and is dried in the mould until a shrinkage of approximately 10% is achieved and then, after removal from the mould, is subjected to further processing steps to produce the glass body.

Abstract: Method and equipment for the manufacture of glass bodies wherein a porous green body is formed by extrusion from the starting material for the glass body in the form of a thixotropic suspension and this green body is then purified and sintered, during which process the starting material is brought in a state of minimum viscosity into an extruding press closed at its outlet end, is heated in the extruding press to a temperature below the boiling point of the dispersing liquid and then, after the extruding press is opened, is extruded into a green body of dimensionally stable shape by means of the die of the extruding press.

Abstract: A method of manufacturing glass bodies, in which the starting material for the glass body, in the form of microdispersed SiO.sub.2 particles, is used to form an open-pore green body which is subjected to a cyclic purification process in which the impurities present in the green body react with a purifying gas which is heated to a temperature in the range from 600.degree. to 900.degree. C., after which the green body is sintered; in each cycle of the said process, the arrangement holding the green body to be purified being flushed and subsequently evacuated.

Abstract: A method for the manufacture of glass bodies, in which a thixotropic suspension, being the starting material for the glass body, is used to form a porous green body which is subsequently purified and sintered, the starting material being liquefied in a mould by subjecting it to mechanical forces, and subsequently freeing it of the influence of the said forces, after which it solidifies again to form a green body.

Abstract: A sol-gel method of preparing doped glass articles is provided. The glass is formed by preparing a sol solution containing hydrolyzed silicon alkoxide and ultrafine particle silica. The sol solution can also include a dopant. The sol solution is gelled in a container, dried and sintered to yield the doped silica glass articles.

Abstract: The present invention relates to a method of producing a fluoride glass preform and/or fiber having a modified refractive index by heating the fluoride glass preform to a temperature that is above its glass transition temperature, but below its devitrification temperature; inserting a first electrode into the inner core of the preform and surrounding the outer perimeter of the preform with a second electrode of opposite polarity; means for generating an electromotive force; and applying an electromotive force through the first electrode and the second electrode which causes a movement of positive ions toward the electrode of opposite charge while simultaneously causing a movement of negative ions toward its electrode of opposite charge such that the movement of these ions results in a modification of the refractive index of the preform.

Abstract: A method of preparing tubular silica glass is disclosed. The method includes the steps of first hydrolyzing silicon alkoxide with acid and then adding ultra-fine particle silica to form a sol solution. The sol solution is placed in a cylindrical container and gelled while rotating the cylindrical container to obtain a tubular gel. The tubular gel is dried and sintered to the tubular silica glass.

Abstract: A method of preparing preforms for optical fibers is provided. The method includes preparation of a first sol solution of a silicon alkoxide hydrolyzed with an acid and ultrafine particle silica, placement of the first sol solution into a container, and gelation of the first sol solution while the container is being rotated to yield a wet gel having a center hole. A second sol solution having a different composition than the first sol solution is prepared and used to fill the center hole in the wet gel. The second sol solution is then gelled to a wet gel composite and the composite is dried and sintered to yield the preform.

Abstract: An optical fiber waveguide resistant to ionizing radiation having a glass core of predetermined refractive index surrounded by glass cladding having a lower predetermined refractive index. The glass core and glass cladding are each composed of high purity silica incorporating gallium as a constituent. The gallium is present in the form of Ga.sub.2 O.sub.3 in a concentration of about 0.01 to 0.15 mole percent ratio to the silica. The glass of the optical waveguide can further include phosphorus in the form of P.sub.2 O.sub.5 as an additional constituent in the amount of from about 5 to 16 mole percent ratio to the total amount of all constituents.The waveguide of the invention is preferably manufactured by using GaCl.sub.3 in combination with an internal vapor phase process to produce a silica soot (16) containing Ga.sub.2 O.sub.3 on the interior surface of a high purity silica tube (10). The soot is then consolidated and the tube collapsed to form a substantially voidless solid rod preform of high purity SiO.