Abstract: A Mach-Zehnder wavelength selective device is made using one or more composite optical fibers each incorporating a phase shift region having one effective refractive index spliced between coupling regions having a different effective refractive index. The optical path length difference or phase delay induced by each such composite fiber is a linear function of the length of the phase shift region.

Abstract: A single-mode optical waveguide fiber designed to limit power penalty due to four wave mixing and a method of making the waveguide is disclosed. Variations in properties, e.g., radius or refractive index, of the waveguide fiber core provide a total dispersion which varies along the length of the waveguide. The algebraic sum of products of length times total dispersion is controlled to a pre-selected value for each waveguide fiber which makes up a system link. Proper choice of total dispersion variation magnitude and sub-length results in a system link wherein a signal travels only short distances in waveguide portions having total dispersion near zero. However, the variation of the total dispersion provides a system link which has a pre-selected dispersive effect on the signal over a selected wavelength range. The dispersive effect on the signal can be chosen to be essentially zero. A number of techniques for fabricating DM fiber are also disclosed.

Abstract: The fiber-coating concentricity of a coated optical fiber is controlled by non-axisymmetrically heating the coating material in the sizing die with respect to the z-axis along which the fiber is drawn. By controlling the temperature profile and thus the viscosity profile of the coating material, the amount of coating material applied to each azimuthal position of the fiber is controlled as it exits the sizing die. The apparatus that provides the desired temperature profile can also be employed to control the coating diameter.

Abstract: Overclad fiber optic couplers typically include an elongated glass body having a solid midregion through which at least two glass optical fibers extend in optical signal coupling relationship. At each end of the midregion is an end region containing a bore from which optical fiber pigtails extend. In accordance with the invention, each end region includes a first projecting portion, one surface of which forms a ledge. That end of each bore opposite the midregion terminates at a recessed face that intersects the respective ledge. One end of at least the first fiber extends from the first bore. That portion of the first fiber outside the first bore has a coating that extends along the ledge, the coating terminating outside the first bore. A mass of glue extends between the ledge and the recessed face and encompasses the bare portion of the first fiber that extends along the first ledge and at least a portion of the first coating that extends along the first ledge.

Abstract: A system for controlling the drawing of a hermetically-coated optical waveguide fiber from a preform is provided in which two measurements of fiber diameter are made and combined into an overall control signal. The first measurement is made on bare fiber in the region of the preform's root using an interference technique. The second measurement is made after the hermetic coating has been applied using a shadow technique. The first measurement provides high speed, high accuracy data needed for process control and defect detection. It is, however, subject to error due to fluctuations in the root with tractor speed. The second measurement reduces the effects of such error on the overall control signal.

Abstract: The invention features an optical two-way transmission-receiver communications system utilizing a coaxial coupler having a ring waveguide and a core waveguide. A surface of an integrated source/ring detector substrate is positioned adjacent said coaxial coupler endface. A ring detector on the substrate, which receives light transmissions from the ring waveguide, has an annular opening therein. A light source disposed on the substrate within the annular opening in the ring detector directs light transmissions to the core waveguide of the coaxial coupler. An alignment device positions the substrate with respect to the coaxial coupler so that the light source and detector are respectively aligned with the coaxial coupler core and ring waveguides.

Abstract: A fiber optic coupler comprising a plurality of single-mode optical fibers, each of which is tapered to form a small diameter section that extends in contiguous relationship with the small diameter sections of the other fibers to form a coupling region. Each of the fibers has a core surrounded by a cladding of refractive index lower than that of the core. At least one of the fibers has a refractive index pedestal of refractive index n.sub.i between said core and cladding, wherein n.sub.1 >n.sub.i >n.sub.2, n.sub.1 and n.sub.2 being the refractive indices of the core and cladding, respectively.

Abstract: An induction furnace for heating a portion of an optical preform in order to draw an optical fiber therefrom. The furnace includes a tubular susceptor which is disposed centrally within a housing. The electromagnetic field from a high frequency coil surrounding the susceptor is coupled to the susceptor to heat and reflow a portion of the preform. A cellular refractory tubular insulator is located between the coil and the susceptor.

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: The present invention relates to a multi-stage fiber amplifier in which the first and stages are connected by means including a filter for attenuating the amplified spontaneous emission. The pump source consists of a pair of light sources that are connected to a coupler that splits the power equally to two output legs. All of the pump power from the second coupler output leg is supplied to the second stage. A portion of the pump power from the second coupler output leg is converted in the first stage to amplified signal and amplified spontaneous emission, and the remainder of the power from that leg is supplied to the second stage.

Abstract: Disclosed is a fiber amplifier including a gain fiber and a source of pump power having a wavelength .lambda..sub.p coupled to one end thereof. A signal of wavelength .lambda..sub.s is introduced into a first end of the gain fiber, and an amplified signal of wavelength .lambda..sub.s is coupled from the second end thereof. The signal can traverse an undesired secondary path as well as a preferred primary path to the amplifier output. To prevent light of wavelength .lambda..sub.s from traversing the secondary path and thus increasing the amplifier noise figure, the amplifier includes attenuating fiber means for attenuating that portion of the signal of wavelength .lambda..sub.s that propagates in the secondary path.

Abstract: Disclosed is a method and apparatus for providing reactant vapors to a utilization site. The apparatus includes a vaporization chamber enclosed by top and bottom walls, side walls and first and second end walls. The first end wall is elevated with respect to the second end wall. The reactant is supplied in liquid form to a flow distributor that delivers the liquid to that portion of the bottom wall near the first end wall. The angle with which the bottom wall is inclined with respect to horizontal is sufficient to cause the liquid to flow down the bottom wall at a rate sufficient to form a film, the thickness of which is smaller than that thickness which would support a bubble during heating of the film. The surface is heated to a temperature greater than the boiling point of the liquid, thereby converting the liquid reactant to a vapor that is delivered to the vapor utilization site.

Abstract: A low loss fiber optic coupler of the type wherein a plurality of single-mode optical fibers are fused together along a portion of the lengths thereof to form a coupling region. Each fiber includes a core and a cladding, the lowest refractive index of the fiber claddings being n.sub.2. Each of the output fibers of the coupler further includes a surface region of refractive index n.sub.4 that inhibits the coupling of light to lossy composite modes, n.sub.4 being lower than n.sub.2.

Abstract: Optical waveguide paths are formed under the surface of a glass substrate by a method comprising (a) forming by ion-exchange a dopant ion path on a first substrate surface, (b) applying an electrode to the second surface, (c) contacting the first surface with a molten salt bath, and (d) applying an electrical field across the substrate to drive the dopant ions deeper into the substrate. The current resulting from high fields can overheat the substrate, thereby causing substrate warping and burying of paths to uneven depths. One aspect of the invention involves cooling the substrate by flowing the molten salt along the first surface of the substrate at a sufficient rate of flow to adequately decrease its temperature and by rapidly flowing the furnace atmosphere over the surface of the substrate. A further aspect of the invention involves initially applying a voltage V.sub.i across the substrate, allowing the current to increase to a predetermined level I.sub.

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 of 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 monolithic, environmentally stable Mach-Zehnder device is formed by threading first and second dissimilar optical fibers through the bore of a glass tube. The tube is evacuated and heated to collapse it onto the fibers. The tube is further heated and stretched at two spaced locations to form two couplers that are joined by the two optical fibers. The fibers have different propagation constants in the region between the two couplers, whereby there is a relative delay in the optical signal propagating in one of the fibers with respect to the optical signal propagating in the other fiber.

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. The difference in mode field diameters between said couplers is sufficient create a difference in coupler fiber propagation constants in the coupling region which degrades the coupling of the .lambda..sub.S signal.

Abstract: An achromatic fiber optic coupler of the type wherein three single-mode optical fibers are fused together along a portion of the lengths thereof to form a coupling region. Each fiber includes a core and a cladding, the lowest refractive index of the fiber claddings being n.sub.2. The fibers are disposed in a triangular array in the coupling region. 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: After a plurality of optical fibers are fused to make a fiber optic coupler, the ends thereof are glued to a substrate to provide the outwardly extending fibers with adequate pull strength. The glue can flow from the point of application toward the fused region where it can adversely affect the the device. To prevent the glue from flowing too far toward the fused region and yet permit sufficient flow to strengthen the fibers, a beam of UV light is directed onto the fibers at that predetermined point where glue flow should stop. When the glue is cured by the beam, it stops flowing. Thereafter, the remainder of the glue is cured.

Abstract: 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.