Abstract: Embodiments of the invention include an optical fiber device such as a tunable birefringent optical fiber having a core region, a cladding layer therearound, and a controllable active material disposed in, e.g., selective capillaries or pockets formed in the cladding layer. The active materials include, e.g., electro-optic material, magneto-optic material, photorefractive material, thermo-optic material and/or materials such as laser dyes that provide tunable gain or loss. The application of, e.g., temperature, light or an electric or magnetic field varies optical properties of the active material, which, in turn, varies or affects the propagation properties of optical signals in the device. The optical device can include a tapered region or long period grating that causes the core mode to spread or couple into the cladding region and, simultaneously, allows the active material to be relatively close to the propagated modes, thus allowing interaction between the active material and the propagating modes.

Abstract: Systems and techniques are described for improving reproducibility in a pre-splice heat treatment. A heat treatment station is described for applying a pre-splice heat treatment to a lead end of a first optical fiber having a first modefield diameter. The heat treatment station comprises a base, and a fiber clamp for holding the first optical fiber such that a length of the lead end of the first optical fiber is positioned over a heat source mounted to the base. The heat source causes a controlled expansion of the first fiber modefield at the first fiber lead end to form an internal bridge. The heat treatment station further includes position adjustment means for adjusting the length of the first fiber lead end that is exposed to the heat source.

Abstract: An optical cable (10) includes one or more tubes (120), each containing a number of optical fibers (101), and a plastic jacket (160) that encloses the tube(s). A pair of diametrically opposed rods (300-1, 300-2) are at least partially embedded in the polyethylene jacket and are made from continuous-filament glass fibers that are embedded in epoxy. Each rod has a compressive stiffness that is effective to inhibit substantial contraction of the cable, and a tensile stiffness that is effective to receive tensile loads without substantial transfer of such loads to the glass fibers. Each dielectric rod includes a thin layer (330) of a frictional adhesion coating that provides a controlled adhesion between the rod and the jacket of between 50 and 300 lb./in2. Whereas dual-rod cable designs have a preferred bending plane that passes through the rods, controlled adhesion between the rods and the jacket enables the cable to be easily bent in other planes and to be blown through ducts having multiple corners.

Abstract: Embodiments of the invention include a method for making optical fiber having reduced aging or hydrogen aging loss over the life of the fiber and optical fiber systems including such optical fibers. The method includes the steps of dehydrating an optical fiber glass core rod in a first environment including oxygen and at least one of chlorine-containing gases, fluorine-containing gases and carbon monoxide; and adjusting the oxygen stoichiometry of the first environment so that it is neither oxygen-rich nor oxygen-deficient. Improved silicon-oxygen stoichiometry during one or more preform manufacturing steps reduces the amount of Si defects generated in the optical fiber preform. Also, deuterium exposure of optical fiber drawn from the preform reduces the likelihood of having atomic defects such as Si defects in the optical fiber that, over time, attract and bond with hydrogen atoms to form molecules that contribute to increased water absorption loss.

Abstract: Embodiments of the invention include an optical fiber cable having improved optical fiber densities and no central strength member. The optical fiber cable includes one or more multi-fiber unit tubes having an optical fiber ribbon stack snugly positioned therein. The diagonal length of the ribbon stack is approximately equal or, alternatively, at least 90% of the inner diameter of the unit tube. The multi-fiber unit tube is made of low-density polyethylene (LDPE) or other material soft and flexible enough to allow the ribbon stack to be relatively firmly positioned therein without affecting the optical fiber performance. The optical fiber cable includes one or more filling materials such as yarn fillers positioned, e.g., between the ribbon stack and the inner walls of the unit tube, to maintain the shape of the multi-fiber unit tube. The yarn filler material includes super absorbent polymers to reduce propagation of water down the unit tube.

Abstract: An optical fiber for use in optical energy transmission system has improved mode coupling in one embodiment thereof and both improved mode coupling and selective attenuation of unwanted modes in another embodiment. The optical fiber includes a plurality of particles of refractive index differing from that of the fiber core, in which the particles are distributed, and from that of the fiber cladding in which, in one embodiment, particles are distributed. In fabricating the fiber, the particles are introduced into the preform from which the fiber is drawn, and, in a co-extrusion process, they are also introduced into the polymer prior to its being extruded with the core material.

Abstract: An optical fiber suitable for generation of a supercontinuum spectrum when light pulses of femtosecond (10−15 sec.) duration are launched at a certain wavelength into the fiber. The fiber includes a number of sections of highly non-linear fiber (HNLF) wherein each section exhibits a different dispersion at the wavelength of the launched light pulses. The fiber sections are joined, for example, by fusion splicing the sections in series with one another so that the dispersions of the sections decrease from an input end to an output end of the fiber. In the disclosed embodiment, a low noise, coherent supercontinuum spanning more than one octave is generated at the output end of the fiber when pulses of light of 188 fs duration are launched into the fiber at a repetition rate of 33 MHz and with an energy of three nanojoules per pulse.

Abstract: A precision method is defined for identifying defective sections of a spoolable material for removal. Defective sections are noted during manufacture and the spool containing the material is subsequently unwound to allow removal of the defective sections. The invention uses rotation data corresponding to the location on the spool where the fiber contains defects. A process controller records rotational positioning data from the take-up spool during manufacturing and uses the information to locate the defect when unwinding the spool. In addition, the pitch of winding the fiber onto the spool may be altered during manufacturing to indicate the beginning and end of a defective section. In this instance, the defective portion of the fiber can be determined during unwinding by monitoring the pitch width of the material. Finally, an algorithm for defining cut out bands adjacent to the defective sections aid in ensuring that no remaining defective fiber remains.

Abstract: A glass tube for use in an optical fiber preform is produced by applying a first soot on an end face of a starting member to form an elongated, porous cylindrical soot core having a first density, and applying a second soot including SiO2 on the periphery of the soot core to form a porous soot cladding having a second density greater than that of the soot core at the periphery of the core. The core and the cladding are later heated together at a temperature sufficient for sintering to form a core glass and a cladding glass. Because the soot core collapses at a greater rate than the soot cladding during sintering, the core glass separates or delaminates radially from the cladding glass. The core glass is then removed from the surrounding cladding glass, and the latter is treated to provide a high purity glass tube suitable for use as part of an optical fiber preform.

Abstract: Systems and methods are described for fabricating a varying-waveguide optical fiber. In one described method, a preform is fabricated having a core and at least one cladding region. The cladding region has a higher viscosity and the core region has a lower viscosity. The relative viscosities of the cladding region and core are chosen such that, when tension is applied to an optical fiber drawn from the preform, the applied tension is primarily borne by the cladding region thereby causing a viscoelastic strain to be frozen into the cladding region, while creating a minimal viscoelastic strain in the core. The method further includes drawing the preform into an optical fiber under an applied tension, such that a viscoelastic strain is frozen into the cladding region the frozen-in viscoelastic strain decreasing the cladding region refractive index.

Abstract: Buffered optical fibers and methods of fabricating them are presented. A representative buffered optical fiber includes an optical fiber through which optical signals can be transmitted and an inner layer comprising an ultra-violet (UV) curable acrylate material that surrounds the optical fiber and protects the core of the optical fiber from microbending forces.

Abstract: A torch and mount assembly wherein the torch, which has a plurality of gas receiving nipples is carried in a housing through which it extends. The housing has a plurality of walls forming a substantially air tight enclosure. In at least one wall of the housing are one or more leakproof fittings which are connected to similar leakproof fittings for the nipples by means of preferably flexible gas conduits within the housing. In the system, gaseous mixtures are applied from a source or sources to the fittings in the housing wall remote from the high temperatures of the torch, while the conduits within the housing are protected from mechanical and thermal stresses. An inert gas from a suitable source is introduced under pressure into the interior of the housing to reduce leakage from the torch into the housing. The atmosphere within the housing is heated, and the constituents of the housing atmosphere are monitored to aid in detecting leakage.

Abstract: The specification describes optical mode converters wherein coupling is made between a fundamental, or near fundamental, propagation mode and the next, or closely adjacent, higher order mode (HOM). Both modes propagate in the core of the optical fiber, thus maintaining efficient transmission through the mode converter. Mode coupling is effected using a long period grating (LPG) and the strength of the mode coupling is dynamically varied by changing the period of the grating or by varying the propagation constants of the two modes being coupled. The period of the grating is varied by physically changing the spacing between grating elements, for example by changing the strain on the grating to physically stretch the LPG. The propagation constants of the modes can be varied using any method that changes the refractive index of the fiber containing the LPG, for example, by changing the temperature, or electrically changing the index using the electro-optic effect.

Abstract: The specification describes tuning devices for controlling variable polarization dependent loss. These are based on the discovery that essential properties of TAP LPGs can be realized in birefringent fibers, i.e. in fibers where the propagation constants of the core and/or cladding modes are different for different SOPs of light. This yields a device that exhibits broadband loss of varying amounts for different SOPs of input light. Thus, the building block for a broadband in-fiber polarizer is realized. Tuning mechanisms are applied to vary the relative coupling magnitudes for two orthogonal SOPs of light in the device. This yields a polarizer in which the polarization is dynamically tuned.

Abstract: Systems and methods are described for reducing splice loss in an optical transmission line. A described system includes fiber guides for holding a first fiber and a second fiber in position for splicing to each other at a splice point. A heat source applies sufficient heat at the splice point to cause the first and second fibers to be fused together at the splice point, and subsequently applied heat to the splice point after the splice has been completed. The system further includes a tensioning assembly for applying a controlled, non-zero tension to the first and second fibers after they have been spliced together.

Abstract: A dispersion compensating fiber and module are described for controlling residual dispersion in a dispersion compensated system. The dispersion compensating fiber is designed with dispersion curve having an inflection point at a wavelength near the optical transmission operating wavelength region. The dispersion curve, having an inflection point near the operating wavelength region, produces a relative dispersion slope that closely matches the relative dispersion slope of the transmission fiber over a relatively wide bandwidth surrounding the operating wavelength region.

Abstract: A tunable multimode wavelength division multiplex Raman pump and amplifier, and a system, method, and computer program product for controlling a tunable Raman pump and amplifier. The tunability of the pump source is accomplished by either straining or heating an external fiber grating, thereby causing a different wavelength of light to be emitted by the pump source. The system includes a microprocessor-based controller that monitors an amplifier's performance and adjusts the drive current and/or wavelength of the tunable pumps of an amplifier to achieve a target performance.

Abstract: A high density panel mounting assembly has a first connector housing having first and second arrays of channels for receiving modified connectors, separated by a shelf. An adapter assembly for receiving the ferrules of the connectors has an interior wall having first and second arrays of bored projections forming sleeves for receiving the connector ferrules. The adapter assembly has a second connector housing substantially identical with the first connector housing mounted to or integral with the rear of the adapter housing for receiving individual connectors. Each of the connector housings has an array of apertures along the top and bottom surfaces for latching the connectors in place. Each of the connectors has a resilient latching arm having a distal end having a latching surface thereon which bears against the end of its corresponding aperture to latch the connector in place within the connector housing.

Abstract: A grating fabrication process utilizes real-time measurement of a grating characteristic (such as, for example, grating period chirp, reflectivity, group delay) as a feedback error signal to modify the writing process and improve the characteristics of the finished grating. A test beam is launched through the optical medium during the writing process (or at the end of an initial writing process) and a particular characteristic is measured and used to generate a “corrective” apodization refractive index profile that can be incorporated with the grating to improve its characteristics. The improvements may be applied to a phase (or amplitude) mask used to write the grating (etching, local deformation, coating changes, for example), or the grating itself may be corrected using additional UV exposure, non-uniform annealing, non-uniform heating, and/or non-uniform tension—these techniques applied separately or in an intermittent sequence.

Abstract: Techniques are described for reducing splice loss by using an ultra-short bridge fiber to splice together a first fiber and a second fiber having different modefield diameters. The ultra-short bridge fiber has an intermediate modefield diameter between the modefield diameters of the first and second fibers. In one described technique, a first end of the ultra-short bridge fiber is spliced to a lead end of the first fiber at a first splice point. The bridge fiber is then cleaved at a predetermined distance away from the first splice point. A lead end of the second fiber is then spliced to cleaved end of the bridge fiber at a second splice point. A single protective splint is then installed that covers the bridge fiber and the first and second splice points. Further described is an optical fiber transmission line including an ultra-short bridge fiber.