Abstract: Applicants have discovered the existence of loss peaks in optical fiber transmission systems using wavelengths in the E-band and the L-band. Specifically, they have discovered the existence of narrow loss peaks at 1440 nm, 1583 nm and 1614 nm. Because the peaks are relatively narrow, they cannot be easily removed by conventional gain equalizers in long haul transmission systems, and although the peaks are relatively small, they can nonetheless cause transmission channels to drop out in amplified DWDM transmission systems. Applicants have further discovered that these loss peaks are due to carbon contamination of the transmission fiber. Thus optical fibers should be fabricated essentially free of carbon contamination. This means eliminating carbon-containing reagents in preform and tube-making processes.

Abstract: A system and method is disclosed for manufacturing single mode optical fiber which incorporates a spin in the molten fiber during manufacturing. The introduction of spin minimizes a form of distortion called polarization mode dispersion (PMD) and varying the spin, i.e. changing its characteristics, is known to further reduce PMD. However, introducing spin on a molten fiber may result in also introducing twist on the fiber. Twist is a non-permanent rotational force on the cooled fiber which causes stress and is to be avoided. A spin function is disclosed that not only contains a high degree of variability for reducing PMD, but also ensures that mechanical twist on the fiber is minimized, thus reducing stress on the fiber. The spin function modulates either the amplitude, frequency, or both, at the beginning of a cycle to minimize twist on the fiber.

Abstract: A fiber coating applicator includes a chamber and a cup positioned over the chamber. The cup is connected to the chamber by an entrance aperture. The chamber includes an exit aperture opposite the entrance aperture. The cup, entrance aperture, chamber, and exit aperture define a pathway for a fiber, such as an optical fiber, to be coated. The chamber further includes an input port for pumping a coating material into the chamber. The entrance aperture is dimensioned such that as a fiber travels along the pathway and coating material is pumped into the chamber, coating material travels upward through the entrance aperture around the fiber into the cup, the upward flow of coating material being restricted by the fiber and entrance aperture such that there is a hydrostatic pressure in the chamber. The exit aperture is dimensioned to shape coating material around a fiber traveling along the pathway.

Abstract: Techniques and systems are described for reducing splice loss in an optical fiber transmission line. One described technique includes splicing together at a splice point a first fiber having a first modefield diameter to a second fiber having a second modefield diameter larger than the first modefield diameter. The splice point is heated to a core expansion temperature to cause a controlled thermal diffusion of core dopant in the first fiber in order to reduce modefield mismatch between the first and second fibers. Splice loss is then reduced by heating the splice point to a differential diffusion temperature to cause a controlled diffusion of a cladding dopant in the first fiber, while maintaining the expanded core.

Abstract: A single-mode fiber of increased core size consists of a “few-mode” fiber, of core size sufficient for guiding up to three high-order modes in addition to the fundamental mode, by interposing perturbations of such spacing along the fiber, as to selectively couple any such high-order modes to (unguided) cladding modes, thereby rejecting all but the fundamental mode. Unwanted coupling of the fundamental mode, leading to added fiber loss, is minimized by appropriate refractive index profile design.

Abstract: Multimode optical fiber local area networks, both intrabuilding and interbuilding, are optimized to take advantage of the wide wavelength operating range offered by co-pending patent application Ser. No. 10/408,076 “Enhanced Multimode Fiber” —a fiber provided both with: longitudinally spaced perturbations for inducing mode coupling and thereby lessening mode dispersion; and with a radial discontinuity for discouraging conversion of bound-to-cladding-modes and thereby lessening added loss previously associated with induced mode coupling.

Abstract: A connector system for terminating an optical fiber cable having a protective outer jacket. The system includes a connector plug and a crimp insert having an axial bore. A distal end of the insert is formed to be joined to a proximal end of the connector plug. A first portion of the insert bore has a diameter corresponding to an outside diameter of the cable jacket. A second portion of the insert bore has a diameter corresponding to an outer diameter of an unjacketed end of the cable. The insert deforms when crimped at axially spaced positions on its periphery, corresponding to the first and the second portions of the insert bore. Thus, both the outer jacket and the unjacketed end of the cable are restrained from axial movement with respect to the joined insert and connector plug.

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.

Abstract: Optical fibers are described that exhibit reduced splice loss. Further described are techniques for fabricating optical fibers exhibiting reduced splice loss. One described fiber includes a plurality of regions, one region having a higher viscosity and the other region having a lower viscosity, such that when the fiber is drawn under tension, a strain is frozen into the higher viscosity region. A lower viscosity buffer layer is sandwiched between the higher viscosity region and the lower viscosity region. The buffer layer isolates the lower viscosity region from changes in refractive index in the higher viscosity region arising from a change in the strain frozen into the higher viscosity region.

Abstract: A system and technique for determining discontinuities or events over a span of a multimode optical fiber (MMF). An optical time domain reflectometer (OTDR) has an operating port, and a first end face of a singlemode optical fiber (SMF) is coupled to the operating port. Light pulses produced by a source in the OTDR emerge from a second end face of the SMF, and an alignment stage aligns and matches the second end face with an end face of a multimode optical fiber (MMF) having a fiber core of given radius. The light pulses from the second end face of the SMF are applied at selected radial positions on the MMF core to excite corresponding mode groups in the MMF. Backscatter light produced by each excited mode group is coupled to the OTDR through the SMF, and locations and values of events detected along the MMF are indicated on the OTDR for each of the selected radial positions.

Abstract: Optical ribbon cable fan-out device includes a top cover portion, a fan-out portion and a bottom portion formed as a unitary body. The fan-out portion has an array of guides housing individual fibers of the optical ribbon cable. The top cover portion and bottom cover portion are connected respectively to the fan-out portion by first and second hinges. The top cover portion and the bottom cover portion each have a plate projecting respectively therefrom to secure a ribbon cable in an axis extending longitudinally through the fan-out apparatus. The fan-out portion is so configured that a first portion of the arrayed guides is co-linear with the axis, a second portion of the arrayed guides is above the axis and a third of the arrayed guides is below the axis. The fan-out apparatus defines pathways for individual optical fibers having a bend radius of at least approximately 1.5 inches.

Abstract: Systems and techniques are described for monitoring a pre-splice heat treatment of an optical fiber. In one described technique, a lead end of a first fiber is prepared for splicing. The lead of the fiber is then loaded into a heat treatment station. While heating the lead fiber end, an optical time domain reflectometer is used to measure reflected backscatter loss from the lead fiber end. The lead fiber continues to be heated end until the measured reflected backscatter loss from the lead fiber end reaches a predetermined level. At that point, the heat treatment is discontinued.

Abstract: A fiber optic cable suitable for blowing into and through ducts containing pressurized gas, such as natural gas, has the fibers therein arranged in arrays that form longitudinally extending vents. The vents are blocked from transmission of any gas by each being filled with a compliant member which assumes the cross-sectional shape of the vents thereby blocking it. In a second embodiment of the invention, the first and third ferrules are fixed within the housing with their offset bores in alignment. A second ferrule is interposed between the first and third ferrules and is mounted in a rotatable member for misaligning the bore in the second ferrule with the bores in the first and third ferrule to produce attenuation of a signal passing through the ferrules by misaligning the fibers contained in the bores.

Abstract: A multi-wavelength cascaded Raman resonator (“MWCRR”). The MWCRR has an optical source for pumping optical radiation centered around an input wavelength. The MWCRR further includes a Raman fiber having at least a first set of optical gratings for converting the pumped optical radiation to wavelengths other than the input wavelength. The Raman fiber also has at least one adjustable output coupler having a variable reflectivity for controlling the power of the optical radiation propagating from the at least one set of optical gratings at the wavelengths other than the input wavelength.

Abstract: A variable attenuator has first and second substantially identical ferrules or capillaries, each being mounted in a barrel or splice housing and extending toward each other, with their distal ends being separated by a gap of a first width. The width of the gap is controlled by a sleeve into which the ferrules are inserted, the ends of the sleeve butting against the front faces of the barrels. The ferrules are made by producing a glass rod mounted between the barrels and having a bore offset from and parallel to the centerline of the rod and breaking or cleaving the rod at its longitudinal center. The broken ends are then polished. The barrels are keyed to a housing member so that the offset bores are coincident in the zero position as defined by the keys.

Abstract: The specification describes optical fibers that are constructed to prevent theft of optical signals. One construction is designed to block access of the core of the fiber to the “writing” radiation necessary to form a grating tap. In this embodiment the optical fiber cladding is provided with a highly absorbing UV layer. In a variation of this embodiment, one or more additional optical paths are provided in the optical fiber to accommodate monitoring signals. The added optical paths allow monitoring signals to be transmitted in the optical fiber, separate from the information signal, to signal an attempt to breach the outer coating or the cladding of the optical fiber. A second case of intrusion is addressed by increasing the sensitivity of the optical fiber to microbending loss to the extent that bends in the fiber cause such high attenuation of the signal that the bends do not go undetected at the receiving station.

Abstract: An optical fiber cable structure including a tube comprised of inorganic fillers dispersed within a soft resin, the tube housing optical fibers or ribbons surrounded by a water blocking material. The use of the inorganic fillers in the soft resin provides a cable structure with superior blowing performance due to low surface friction and high flexibility, allowing more effective installation of the fiber optic cable via blowing techniques The use of the inorganic fillers in the soft resin also reduces the thermal expansion/contraction of the cable structure, and increases the compression resistance of the cable structure to axial loads, providing protection to the optical fibers.

Abstract: A pull-proof optical fiber connector for use with robust optical fiber has a housing and a ferrule bearing barrel member therein having a first outside diameter over a front portion thereof and a second, lesser outside diameter rearward portion, and a bore extending therethrough forming an optical fiber passage. The barrel member and, hence, the ferrule are rearwardly movable under axially pulling stress, and a stop member prevents further rearward movement prior to any disengagement of the ferrule with an associated ferrule or other apparatus. In one embodiment of the invention, the stop member is a fiber retention member having a front face and a bore extending therethrough of lesser diameter than the outside diameter of the second portion, thereby halting rearward movement when the end of the second portion butts against the front face of the cable retention member.

Abstract: A system and method is disclosed for determining information regarding the result of introducing a rotational force on an optical fiber during manufacturing. A rotational deformation of the molten fiber, called spin, is imparted that becomes permanent upon cooling of the fiber. The rotational force also introduces twist on the cooled fiber, which is a non-permanent, mechanical rotation of the fiber. The system and method uses a diameter measuring device that produces a signal corresponding to the fiber's diameter with respect to time. Since the fiber is slightly elliptical in practice, periodic variations in the diameter measurement signal are detected that reflect the rotation imparted into the fiber. The signal is further processed to provide data regarding the effect of the rotations introduced into the fiber, namely the twist and spin present in the fiber.

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 beat 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.