Abstract: An achromatic fiber optic coupler of the type wherein a plurality of single-mode optical fibers, each having a core and a cladding, are fused together along a portion of the lengths thereof to form a coupling region. The propagation constants of the fibers are preferably equal; however if the fiber claddings have different refractive indices, the lowest cladding refractive index is n.sub.2. A matrix glass body of refractive index n.sub.3 surrounds the coupling region, n.sub.3 being lower than n.sub.2 by such an amount that the value of .DELTA..sub.2-3 is less than 0.125%, wherein .DELTA..sub.2-3 equals (n.sub.2.sup.2- n.sub.3.sup.2)2n.sub.2.sup.2.

Abstract: The invention concerns a method and apparatus for producing a carbon coated optical fiber. An optical fiber is drawn through a reactor tube. Reactant gas is flowed into the tube and onto the fiber where it reacts to form a carbon coating on the fiber. The reactant gas and reaction products are flowed in the direction of movement of the fiber and out of an end of the tube and into a receiving chamber having a diameter larger than that of the reaction tube. The reactant gas continues to react as it flows through the tube and after it exits the tube. At least some of the reaction product deposit on the surface of the receiving chamber where it has no adverse effect on the draw process.

Abstract: An overclad fiber optic coupler of the type wherein a plurality of optical optical fibers, each having a core and a cladding, are fused together along a portion of the lengths thereof to form a coupling region. Surrounding the coupling region is a matrix glass body of refractive index n3 which is lower than the fiber cladding refractive index n.sub.2. The body has an inner region adjacent the optical fibers, an outer region having a radius greater than that of the inner region, and a transition region between the inner and outer regions. The softening point temperature of the inner region is greater than that of the outer region. The coupler exhibits both low polarization dependent loss and low excess loss.

Abstract: A fiber optic coupler is formed by inserting a plurality of optical fibers into the longitudinal bore of a glass tube so that at least a portion of each fiber extends from at least one end of the tube. The midregion of the tube is collapsed onto the fibers, uncollapsed bore portions remaining at the tube end regions. Each bore portion is connected to the tube end surface by a funnel that facilitates the fiber insertion step. The central portion of the midregion is stretched to reduce the diameter thereof. In a first embodiment, glue is applied to the funnel. Before the glue is cured, a sufficient period of time is allowed to elapse to permit said glue to flow by capillary action between the fibers and the adjacent portion of the wall of the bore portion. The glue flows at least 3 mm into the bore portion beyond the bottom of the funnel. The glue that flows by capillary action fails to completely surround the fibers with glue. The glue is then 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 method of making an optical fiber having an oblong core comprising the steps of depositing layers of core glass particles and cladding glass particles on an enlarged mandrel, removing the mandrel to form a tubular porous preform, consolidating the porous preform to form a dense glass preform, evacuating the central hole of the dense glass preform while stretching that preform to collapse the central hole thereof and form a flattened rod, applying cladding material to the rod, and drawing the resultant composite to form an optical fiber. To facilitate the flat collapse of the central hole of the dense glass preform and to cause the core to have a large aspect ratio, the inside diameter-to-outside diameter ratio of the dense glass preform should be within the range of 0.3 to 0.9. For preferred core and cladding glasses, this ratio should be between 0.5 and 0.6. Also, the mandrel diameter should be at least 12 mm, and it is preferably between 25 mm and 50 mm.

Abstract: Disclosed is a fiber amplifier system in which a gain fiber is operatively combined with a fiber optic coupler having first and second coupler optical fibers. The coupler fibers are fused together along a portion of their lengths to form a wavelength dependent coupling region whereby most of the light power of a wavelength .lambda..sub.s couples between them, and most of the light power of a wavelength .lambda..sub.p that is introduced into the first fiber remains in it. The mode field diameter of the first coupler fiber is substantially matched to that of the gain fiber and is smaller than that of the second coupler fiber. One end of the first coupler fiber is spliced to the gain fiber. A transmission fiber is spliced to the second coupler fiber, and a laser diode introduces pumping light of wavelength .lambda..sub.p to the first coupler fiber. The fiber optic coupler preferably includes an elongated body of matrix glass through which the first and second coupler fibers extend.

Abstract: A coupling mechanism for a non-identical dual core optical fiber. The fiber is sensitized along selected portions of its length by coating the fiber in a pattern of bands of specified spacing with material that is sensitive to the presence of a predetermined parameter or environmental field. By virtue of inequality of propagation properties and mismatch of optical phase of the fields of the two cores, evanescent wave coupling is largely or wholly suppressed except in those portions of length coated in the specified spatially periodic manner. Optical power launched into one of the two cores remains propagating within that core alone over an extended length of the fiber, except for that period of time when the predetermined parameter or environmental field is sensed. The specific spatial periodicity of the pattern of coating bands on the outside of the fiber acts in concert with the nonidentical propagation parameters of the two cores to effect intercore coupling of optical energy.

Abstract: Disclosed is an optical waveguide fiber having a core surrounded by a layer of cladding material. The core is characterized in that it includes a region of depressed refractive index. The inner radius a.sub.i of this region is greater than zero, and the outer radius a.sub.o thereof is less than the core radius. By appropriately selecting the core index depression characteristics such as radial location, width, depth and shape, a fiber having the desired waveguide dispersion characteristics can be designed. Dispersion minimization over a wide wavelength range can be achieved, without adverse effect on system loss.

Abstract: A porous glass optical waveguide preform is formed by depositing a coating of glass particulate material on the lateral surface of a core which may be a porous glass body continuously produced by the axial deposition of glass particles. The core rotates and moves longitudinally in one direction with respect to two flame hydrolysis burners which emit streams of glass particles having different compositions. In addition, the two burners reciprocatingly move with respect to a portion of the length of the core. The speed of each burner varies as it traverses along its path of reciprocating motion. The thickness of the layer produced by a burner at a given point is inversely related to the speed of the burner as it passes that point. The layers formed by the completion of a single traverse by both burners combine to form a conically-shaped layer, the composition of which varies from the base toward the apex thereof.

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 heated and stretched by first pulling means to form a glass rod which is drawn by second pulling means past an intermittant source of localized heat. When the localized heat source is turned on, the second pulling means draws the rod downwardly at a rate faster than the first pulling means. Since the rod is softened by the localized heat source, a necked-down coupling region is formed. The rod is severed to form a plurality of coupler units. When an end of a 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: A plurality of optical waveguide preforms are simultaneously formed by depositing on a plurality of starting members layers of glass soot to build up a coating on each starting member. The soot layers are deposited by traversing a series of burners along the starting members in such a manner that a given one of the burners traverses the first starting member from a first end thereof to a second end thereof to form a layer of soot thereon. The remaining burners of the series similarly traverses the first starting member, a plurality of burners traversing the first starting member at any given time. After the first burner has traversed the first starting member it similarly traverses the second starting member. After the last of the series of burners has begun its traverse along the first starting member, the first of the series of burners completes its traverse of the second starting member and again begins traversing the first starting member immediately following the last of the series of burners.

Abstract: A porous glass optical waveguide preform is formed by depositing a coating of glass particulate material on the lateral surface of a core which may be a porous glass body continuously produced by the axial deposition of glass particles. The core rotates and moves longitudinally in one direction with respect to two flame hydrolysis burners which emit streams of glass particles having different compositions. In addition, the two burners reciprocatingly move with respect to a portion of the length of the core. The speed of each burner varies as it traverses along its path of reciprocating motion. The thickness of the layer produced by a burner at a given point is inversely related to the speed of the burner as it passes that point. The layers formed by the completion of a single traverse by both burners combine to form a conically-shaped layer, the composition of which varies from the base toward the apex thereof.

Abstract: An apparatus is provided for curing a coating applied to an optical fiber. An elongated ultraviolet lamp and the optical fiber emerging from the coater are located at focii of an elliptical mirror which focuses the ultraviolet energy onto the coated fiber. The fiber is surrounded by a cylindrical chamber that is transparent to ultraviolet light. The chamber includes a jacket through which there flows a fluid which absorbs infrared energy. A cooling gas flows from a annular slot located at the bottom end of the chamber. The slot is so angled that gas flowing therefrom is directed upwardly and inwardly toward the coated fiber so that there exists within the chamber a recirculating flow of cooling gas. This enables the cooling gas to repeatedly absorb heat from the coated fiber and give up that heat to the chamber wall which is cooled by the fluid.

Abstract: This invention relates to a method forming fluorine-doped glass. A coating of glass particles is deposited on the surface of a cylindrical rod of high purity glass. The coated rod is inserted into a furnace which contains a cylindrical muffle formed of high silica content glass. A fluorine-containing atmosphere is flowed through the muffle and over the outer surface of the coating of glass particles and also flows inwardly through the interstices thereof. The temperature within the furnace is sufficiently high to cause fluorine to diffuse into the surfaces of the glass particles and to cause the particles to fuse and form a fluorine-containing dense glass coating on the surface of the rod.

Abstract: A tubular capacitor is formed as follows. A ceramic tube comprising an outer ceramic cylinder and a plurality of radial walls is extruded. The extruded body may also include a second ceramic cylinder coaxial with the first. The one or more cylinders and the radial walls form a plurality of longitudinal passages. After the extrudate is fired and cut, the surfaces of the passages and the remaining surfaces of the cylinder or cylinders are metallized. Selected regions of metalization are removed to form discrete electrodes. The end terminations each comprise a base member from which there extends a plurality of prongs. Some of the prongs extend into the longitudinal passages, whereas others make contact with the outer surface of the outer cylinder and the inner surface of the inner cylinder.

Abstract: A tubular capacitor is formed as follows. A ceramic tube comprising an outer ceramic cylinder and a plurality of radial walls is extruded. The extruded body may also include a second ceramic cylinder coaxial with the first. The one or more cylinders and the radial walls form a plurality of longitudinal passages. After the extrudate is fired and cut, the surfaces of the passages and the remaining surfaces of the cylinder or cylinders are metallized. Selected regions of metalization are removed to form discrete electrodes. Two sets of electrodes are respectively connected to first and second electrical termination means.

Abstract: A single-mode optical waveguide is constructed in a manner such that the core thereof is subjected to a stress-induced birefringence. A coating of core glass soot is deposited on the surface of a cylindrical mandrel, and a coating of inner cladding glass soot is deposited on the core glass soot. The mandrel is removed and the resultant porous preform is consolidated to form a hollow dense glass preform. The preform aperture is closed at both ends. Diametrically opposed slabs are removed from the inner cladding region of the consolidated preform. The resultant article is evacuated, heated and stretched to close the aperture and form a preform foreproduct having two opposed rounded sides and two opposed flattened sides. The foreproduct is coated with a layer of outer cladding glass soot having a thermal coefficient of expansion which differs from that of the inner cladding glass by at least 1.times.10.sup.-7 /.degree.C.

Abstract: Disclosed is a sample chamber which is particularly adapted to the spectrophotometric analysis of blood samples. The instrument of which the sample chamber is a part includes means for directing a beam of light through the sample fluid and means for analyzing the light emanating from the fluid. The sample chamber comprises a first transparent member having a flat surface. A surface of a prism is disposed adjacent to the flat surface of the first member, and a resilient gasket located between the prism and the first member seals off a region which forms the sample chamber. A spring on a door, which closes to a position adjacent to the prism, engages the hypotenuse surface thereof to force the prism against the first member and compress the resilient gasket. First and second holes through the prism intersect the first surface thereof at opposite sides of the chamber formed by the gasket to enable the sample fluid to flow through the chamber.

Abstract: A porous glass optical waveguide preform is formed by depositing a coating of glass particulate material on the lateral surface of a core which may be a porous glass body continuously produced by the axial deposition of glass particles. The core rotates and moves longitudinally in one direction with respect to two flame hydrolysis burners which emit streams of glass particles having different compositions. In addition, the two burners reciprocatingly move with respect to a portion of the length of the core. The speed of each burner varies as it traverses along its path of reciprocating motion. The thickness of the layer produced by a burner at a given point is inversely related to the speed of the burner as it passes that point. The layers formed by the completion of a single traverse by both burners combine to form a conically-shaped layer, the composition of which varies from the base toward the apex thereof.