Abstract: The specification describes an optical fiber drop cable with a flat configuration and having two side-by-side subunits. One of the subunits contains a cable strength member, e.g. a steel wire or stranded wire. The other subunit is an optical fiber subunit, which contains the optical fiber(s), and also contains one or more additional strength members. In a preferred embodiment, the cable is dry, and has conformal encasements that couple the optical fiber(s) to the outer cable sheath.

Abstract: A flexible membrane test apparatus and test method for high-speed IC chips. The method and apparatus rely on locating the reference components of the test circuit very close to the contact pads of the IC chip under test. This is achieved in one embodiment by locating those components adjacent to the flexible membrane. In another embodiment, the reference components may be attached to the membrane itself, so the length of the runners connecting the contact points of the tester and the critical reference components is optimally reduced. In yet a further embodiment, the entire test circuit, in the form of an IC test chip, is located on the membrane.

Abstract: The specification describes a technique for drawing circular core multimode optical fiber using twist during draw to increase fiber bandwidth.

Abstract: The specification describes an improved optical fiber cable wherein the cable cross section is round and contains a plurality of bundled optical fibers. The bundle may comprise randomly spaced fibers or fibers aligned in a ribbon configuration. The bundle is encased in a polymer encasement that couples mechanically to each optical fiber. Preferably, the fibers are spaced from the nearest neighbor to improve coupling. In some embodiments the encasement is relatively hard, and is deliberately made to adhere to the optical fiber bundle. Consequently the encasement medium functions as an effective stress translating medium that deliberately translates stresses on the cable to the optical fibers. The cable construction of the invention is essentially void free, and provides a dry cable with water blocking capability.

Abstract: The specification describes an improved optical fiber design in which the criteria for high performance in a Raman amplified optical system, such as moderate effective area, moderate dispersion, low dispersion slope, and selected zero dispersion wavelength, are simultaneously optimized. In preferred embodiments of the invention, the dispersion characteristics are deliberately made selectively dependent on the core radius. This allows manufacturing variability in the dispersion properties, introduced in the core-making process, to be mitigated during subsequent processing steps.

Abstract: The specification describes dispersion compensators that are adjustable based on selection of mode propagation properties of two or more modes. The fundamental device structure comprises two or more sections of optical fiber that support the fundamental mode as well as well as one or more higher-order-modes (HOM). The HOM fibers are connected to each other by means of a spatial mode-converter (MC) that is switchable. The MC may be fabricated with, for example, long-period fiber-gratings (LPG), coupled waveguide devices, free-space phase-retardation elements, micro-electro-mechanical devices, or acousto-optic couplers. The MC is assembled such that it transforms any incoming spatial mode into one of any other guided modes in the HOM fiber. Switching is achieved by strain, temperature, the electro-optic or nonlinear optic effect, or any other physical effect that changes the refractive index of the optical material used to construct the MC.

Abstract: The specification describes an improved optical fiber cable wherein the cable cross section is round and contains a plurality of bundled optical fibers. The bundle may comprise randomly arranged optical fibers or optical fibers aligned in a ribbon configuration. The bundle is encased in a polymer encasement that couples mechanically to the optical fibers. In some embodiments the encasement is relatively hard, and is deliberately made to adhere to the optical fiber bundle. Consequently the encasement medium functions as an effective stress translating medium that deliberately translates stresses on the cable to the optical fibers. The cable construction of the invention is essentially void free, and provides a dry cable with water blocking capability.

Abstract: The specification describes a VAD method for producing optical fiber preforms by depositing soot onto a solid core rod. The solid core rod preferably has a uniform composition, doped or undoped, suitable for the center core region of the preform. The primary cladding layer, and additional cladding layers if desired, are produced by depositing soot on the center core rod. The surface of the center core rod is treated with an etchant torch that traverses the center core rod in front of the soot deposition torch. This produces a clean interface between the core and primary cladding. This soot-on-center-core-rod method allows the production of sharp index profiles by reducing the diffusion of dopants into and out of the center core portion of the preform that occurs in soot-on-soot processes.

Abstract: The specification describes a VAD method for dynamically controlling the growth rate of both the core soot and the cladding soot in response to separate growth monitors.

Abstract: The specification describes an improved optical fiber design in which the criteria for high performance in a Raman amplified optical system, such as moderate effective area, moderate dispersion, low dispersion slope, and selected zero dispersion wavelength, are simultaneously optimized. In preferred embodiments of the invention, the dispersion characteristics are deliberately made selectively dependent on the core radius. This allows manufacturing variability in the dispersion properties, introduced in the core-making process, to be mitigated during subsequent processing steps.

Abstract: The specification describes a wavelength monitoring system for multiple wavelength communications systems, such as WDM systems, based on the recognition that the mechanism for spatially separating the individual wavelength bands can be achieved within the optical fiber itself. Individual wavelength bands are separated using a series of discrete gratings spaced longitudinally along the fiber core. The wavelength bands are extracted from the fiber core by converting the energy in the selected band from a core-guided mode to a radiation mode. By using a tilted grating, the light in the radiation mode is directed through the cladding and out of the fiber. Spatial resolution of the selected bands can be any desired physical length. An important implication of this is that detection can be made in the near field using inexpensive detecting apparatus.

Abstract: The specification describes a flexible membrane test apparatus and test method for high-speed IC chips. The method and apparatus rely on locating the reference components of the test circuit very close to the contact pads of the IC chip under test. This is achieved in one embodiment by locating those components adjacent to the flexible membrane. In another embodiment, the reference components may be attached to the membrane itself, so the length of the runners connecting the contact points of the tester and the critical reference components is optimally reduced. In yet a further embodiment, the entire test circuit, in the form of an IC test chip, is located on the membrane.

Abstract: The specification describes an optical filter wherein long period gratings (LPGs) are used in a new configuration to provide in-line bandpass filtering of optical signals. In the basic embodiment, two dissimilar LPGs are installed in the optical fiber transmission line. The first LPG converts light, over a broad wavelength range, being transmitted in the fundamental, or LP01, mode of the optical fiber transmission line into light in a higher order mode (HOM) of the optical fiber. The mode-converted signal, with mode LPm,n, is then coupled to a second waveguide, the second waveguide having transmission characteristics different from those of the first. The second waveguide supports propagation of light in a LPm,n mode. The mode-converted signal is then transmitted through a second LPG where the signal over a selected narrow band of wavelengths that is accepted by the second LPG is converted back to a LP01 mode.

Abstract: The specification describes an optical fiber drop cable with a flat configuration, corresponding to “A-drop” cable. The cable is dry, and has a conformal primary encasement that is coupled directly to the optical fiber(s). Coupling the optical fibers and the exterior surface of the cable provides unexpected benefits, reducing the tendency of the fiber cable to buckle or shrink-back, and reducing the susceptibility of the cable to fiber retraction. The drop cable comprises three in-line components encased in a conformal secondary encasement. The center component comprises the optical fiber(s) coupled to the primary encasement. Located on each side of the optical fiber system are strength members. In a preferred embodiment, dimensions of the three elements are chosen so that the diameter of the center component is less than the diameter of either strength member. This provides crush protection for the optical fiber system.

Abstract: Dynamically controlling the reaction temperature at the tip of a soot preform by controlling the flow of hydrogen gas to the core torch provides a wide latitude of control over the temperature range necessary to produce uniform composition of the preform.

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: 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 a distributed Raman amplifier with multiple pump sources for wide band amplification of wavelength division multiplexed (WDM) signals. It was recognized that using multiple pump sources introduces non-linear effects, such as four wave mixing (FWM). These effects are reduced by multiplexing the pump wavelengths in the multiple pump source. It was also recognized that not all of the pump wavelengths over the wavelength spectrum of the pumps contributes to FWM. Thus fewer than all of the pump wavelengths require multiplexing to eliminate FWM in the multiple wavelength pump source. Various approaches are described to ensure that the pump wavelengths do not interact in FWM in the transmission span. The selected individual pump wavelengths may be either time division multiplexed, or frequency modulated.

Abstract: The specification describes a technique for drawing circular core multimode optical fiber using twist during draw to increase fiber bandwidth.

Abstract: Integrated circuit devices are formed in a substrate wafer using selective epitaxial growth (SEG). Non-uniform epitaxial wafer thickness results when the distribution of SEG regions across the surface of the wafer is non-uniform, resulting in loading effects during the growth process. Loading effects are minimized according to the invention by adding passive SEG regions thereby giving a relatively even distribution of SEG growth regions on the wafer. The passive regions remain unprocessed in the finished IC device.