Abstract: A fiber optic coupler is formed by providing a glass tube having a longitudinal aperture. Glass optical fibers, each having a core, cladding and coating are disposed within the longitudinal aperture, the fibers extending beyond each end of the tube. The coating is removed from that portion of the fibers in the midregion of the tube but remains on that portion of the fibers extending into the ends of the apertures. The aperture is formed by a plurality of flattened walls, the dimensions and orientations of which are such that the cross-section of the aperture in the central region of the tube is symmetrical with respect to a plane passing through the longitudinal axis of the tube. At any cross-section of the aperture that is adjacent the coated regions of the fibers, each fiber coating contacts two walls of the aperture. The fibers are held taut to effect a tension, and the midregion of the tube is heated, collapsed about the fibers, and drawn to reduce the diameter thereof over a predetermined length.

Abstract: An overclad fiber optic coupler is formed from a coupler preform including a glass tube having a longitudinal aperture. The aperture is formed of a plurality of similarly shaped side walls, each of which includes a longitudinally extending, inwardly projecting protrusions. The region between each two adjacent protrusions constitutes a corner region. Disposed within the aperture are at least a portion of each of a plurality of glass optical fibers, one fiber being situated in each corner region. The midregion of the tube is collapsed onto the fibers, the protrusions maintaining the fibers in their relative positions. At least a portion of the midregion is stretched to reduce the tube midregion diameter.

Abstract: A fiber optic coupler is formed by providing a glass tube having a longitudinal extending aperture. Protective coating is removed from a region of a first optical fiber intermediate the end. 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 is near the tube end. 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. The threading operation is continued until the uncoated regions extend through the midregion of the tube, the midregion is heated to collapse it about the fibers, and the central portion of the midregion is drawn to reduce the diameter along a predetermined length.

Abstract: An optical fiber splice and the method of forming it are described wherein a hollow cylindrical glass member is provided, the member having a bore along the longitudinal axis thereof. Fluid at a pressure in excess of ambient pressure is provided to the bore while the member is subjected to localized heating of the member to the softening point of the glass. In this manner, a bubble is formed within the member bore under the influence of said heating and pressure. For more uniform bubbles, the member may be rotated about its longitudinal axis while it is subjected to said fluid pressure and heating. The splice member is subsequently formed by severing the cylindrical member at the location of the bubbles. Optical fibers may be inserted into the ends of the splicing member and cemented in place.

Abstract: An optical transmission system wherein light is transmitted from a transmitter to a receiver by at least one transmission optical fiber. The system includes a dispersion transformer which receives light from one of the components, compensates for or transforms the delay distortion of the various wavelengths transmitted through the system, and provides the next component in the system with a compensated or transformed light beam. The dispersion transformer comprises means for receiving light from one of the components and dispersing/separating the light into the plurality of spatially separated beams which are directed onto the endface of a multimode optical fiber. The position of each beam on that end-face is a function of the velocity with which the light that forms the beam propagates through the transmission optical fiber.

Abstract: This invention relates to a method of drawing twist-free optical fibers; it is particularly useful for drawing polarization retaining single-mode optical fibers having azimuthal inhomogeneities. There is applied to the fiber, during the drawing thereof, a coating having a non-circular cross-section, the azimuthal inhomogeneity of the fiber being positioned in a substantially constant orientation with respect to the non-circular cross-section of the coating. In another embodiment, a plurality of fibers having azimuthal inhomogeneities are drawn from a plurality of preforms that are properly oriented in the draw furnace. The fibers are drawn through the same coater so that the azimuthal inhomogeneity of each fiber is oriented in a substantially constant relationship with respect to the azimuthal inhomogeneities of the remaining fibers in the coating.

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: A method of making a polarization retaining single-mode (PRSM) optical fiber coupler. A section of coating is stripped from the central portion of two PRSM optical fibers. The fibers extend through the bore of a glass tube, the stripped portions being centered in the tube, and the coating portions extending into the ends of the bore. In one embodiment, each fiber is provided with a rectangularly shaped coating, and the two larger flattened sides of the coating are specifically oriented with respect to the major and minor axes of the PRSM fiber therein. The fiber coating can be disposed in only one orientation in the rectangularly-shaped tube bore, thereby properly orienting the two PRSM fibers with respect to each other. In another embodiment, the PRSM fibers are disposed within a single coating, the azimuthal inhomogenity of one fiber being aligned in the coating with respect to that of the remaining fibers.

Abstract: A method of making an integrated optical component in which a central planar region includes an optical circuit path and a lateral region includes an optical fiber positioning groove in alignment with the path. A glass body having central and lateral regions is coated with a mask material. A photolithographic technique is used to provide the mask material with a patterned opening in the central region corrsponding in shape to the circuit path and a patterned opening in the lateral region corresponding to the shape of the alignment groove. A layer of resisting material is applied over the mask on the central region and the lateral region is etched to form the groove. The layer of resisting material is removed, and the zone of the central region that is exposed by the opening in the mask is subjected to an ion exchange process in order to form therein an optical path that is in registration with the fiber positioning groove.

Abstract: A device for connecting optical fibers is formed by inserting one or more fibers into at least one end of a capillary tube. The bore is tapered to facilitate fiber insertion. To taper the end of a bore, the tube is rotated about its longitudinal axis while a first narrow stream of abrasive particles is directed onto the tube end. The axis of the first stream is located off the axis of the tube bore, thereby forming a taper that is spherical rather than conical. A second stream, the axis of which is coaxial with the bore, is then directed onto the tube end to remove that portion of the tapered aperture adjacent the bore, thereby forming a more funnel-shaped aperture.

Abstract: A method of making an economical fiber coupler comprises providing a glass tube having first and second end portions and a midregion, and a longitudinal aperture extending therethrough. Two suitably prepared glass optical fibers, each having a core and cladding, are disposed within the longitudinal aperture, the fibers extending beyond each end thereof. The fibers are held taut to effect a tension therein, and they are glued to each end portion. The midregion of the member is heated, collapsed about the fibers, and drawn to reduce the diameter thereof.

Abstract: Optical fibers are spliced by securing them in end-to-end relationship in a tube. Tinted epoxy is inserted into the bore. One fiber is inserted into the bore until its endface reaches the center thereof. As the second fiber is inserted into the other end of the bore, the length of the epoxy column in the bore is observed to diminish as epoxy is displaced into venting means associated with the bore. When the second fiber begins to buckle, movement thereof is stopped. The central region of the tube is inspected to ascertain the disappearance of the epoxy column. This indicates that the endfaces are in abutment. The tube may contain an integral lens for viewing the fibers in the bore. A stripe of appropriate color on one side of the bore provides the contrast to enhance the visibility of the tinted epoxy.

Abstract: A fiber optic coupler is formed as follows. Glass optical fibers, each having a core, cladding and coating are disposed within the longitudinal aperture of a capillary tube, the fibers extending beyond each end thereof. The fibers are preferably held taut to effect a tension therein. The coating is removed from that portion of the fibers in the midregion of the tube by oxidation, depolymerization or the like. The coating remains on those portions of the fibers extending into the ends of the apertures to precisely orient the fibers within the tube. The midregion of the tube is heated, collapsed about the fibers, and drawn to reduce the diameter thereof.

Abstract: A fiber optic coupler is formed by providing a glass tube having a longitudinal aperture extending therethrough. Glass optical fibers, each having a core, cladding and coatng are disposed within the longitudinal aperture, the fibers extending beyond each end thereof. The coating is removed from that portion of the fibers in the midregion of the tube but remains on that portion of the fibers extending into the ends of the apertures. The aperture is formed by a plurality of flattened walls, the dimensions and orientations of which are such that the cross-section of the aperture in the central region of the tube is symmetrical with respect to a plane passing through the longitudinal axis of the tube. At any cross-section of the aperture that is adjacent the coated regions of the fibers, each fiber coating contacts two walls of the aperture.

Abstract: The present invention pertains to an asymmetrical bidirectional optical communication system of the type comprising a central station, a plurality of user stations, and a plurality of bidirectional optical transmission paths, one of which connects the central station and one of the user stations. The central station is provided with a laser for initiating in the optical transmission path the propagation at a wavelength in the 1100-1700 nm window of a single-mode signal. Each user station is provided with a light source which initiates in the optical transmission path the propagation at a wavelength in the 700-950 nm window of a few-mode signal. Each optical transmission path comprises an optical fiber having transmission characteristics such that the single-mode signal propagates with a total dispersion less than 5 ps/km-nm and the few mode signal propagates with a bandwidth greater than 1 GHz-km.

Abstract: Disclosed is a mode field modifier which can be used in a fiber-to-fiber connector or a source-to-fiber connector. In a downtaper-type mode field modifier embodiment, the modifier comprises a modifier core of refractive index n.sub.1 surrounded by first and second cladding layers having refractive indices n.sub.2 and n.sub.3, respectively. In an uptaper-type mode field modifier embodiment, the modifier comprises a modifier core of refractive index n.sub.1 surrounded by a cladding layer having a refractive index n.sub.2. The refractive indices are such that n.sub.1 >n.sub.2 >n.sub.3. In both embodiments, there is a nonadiabatic taper intermediate the ends of the mode field modifier, whereby a substantial amount of mode coupling occurs therein.

Abstract: The present invention pertains to an optical fiber comprising a transparent core having a maximum refractive index n.sub.1 and a radius a surrounded by a layer of transparent cladding material having a refractive index n.sub.0 which is less than n.sub.1. The refractive indices n.sub.1 and n.sub.0, the radius a, and the refractive index profile of the core are designed such that:(a) .DELTA..tau..sub.j, the difference between .vertline.d(Vb)/dV.vertline..sub.j, the normalized delay time of the jth mode and .vertline.d(Vb)/dV.vertline..sub.0, the normalized delay time of the fundamental mode, is less than about 5.times.10.sup.-2 over a wide range of V-values where j is equal to 1 or 2 and represents the highest order mode that propagates with a low loss, 0 represents the fundamental mode, b is the propagation constant and V is the normalized frequency, and(b) the normalized waveguide dispersion Vd.sup.2 (Vb)/dV.sup.2 is about equal to or less than 0.2 at V-values near V.sup.1.sub.

Abstract: The present invention relates to a method of attaching an optical fiber alignment ferrule to a connector body, the first end of which is lens-shaped. The body has an indented region in the second end thereof opposite the lens, the indented region being centered on the optical axis of the lens. The body is mounted in a cavity in an alignment fixture which also includes a bore that is aligned with the cavity. The bore is so positioned that when a connector body is mounted in the cavity, the axis of the bore is coaxial with the optical axis of the lens. A rigid alignment rod is slidably mounted in the bore so that the rod is capable of only longitudinal movement along its axis. One end of the rod is inserted through the hole in a tubular ferrule. The rod is advanced toward the connector body until the rod contacts the bottom of the indented region. The ferrule is moved along the rod until it contacts the second surface of the body. The ferrule is then bonded to the body.

Abstract: A method is disclosed for making a step-index optical fiber having a steep refractive index gradient between core and cladding. Core glass particles comprising a base glass and a refractive index-increasing dopant are deposited on a mandrel. The mandrel is removed and the resultant soot preform is consolidated to form a core preform having a dopant-poor surface region. The core glass preform is stretched and the hole therein is closed to form a core bait rod. Cladding glass soot is deposited on the core bait rod at a density which is at least 0.5 g/cc. This is accomplished by directing the flame from an auxiliary burner onto the core bait rod immediately prior to the deposition of cladding soot thereon. The resultant preform is consolidated and drawn into an optical fiber. In another embodiment, the etched core preform is overclad with a layer of cladding glass, and the composite preform is stretched prior to applying a second overclad layer.

Abstract: A single-mode transmission optical fiber may have a bandwidth much greater than that necessary to transmit a desired predetermined maximum data rate. The single-mode fiber is connected to a bandwidth limiting device comprising the serial combination of an input optical fiber, a mode converter and multimode fiber. If the multimode fiber is capable of propagating two modes, for example, the mode converter converts the LP01 signal from the transmission fiber to the LP01 and LP11 modes. These two modes propagate at different speeds through the multimode fiber. Means connected to the output end of the multimode fiber detects the two modes. If the time delay difference .DELTA.t between the two modes is small with respect to the width of a pulse in the transmitted pulse train, the pulse train will be detected without distortion. Transmission at a higher data rate causes .DELTA.t to be large with respect to pulse width.