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: A single mode optical waveguide having reduced polarization mode dispersion and a method for making such a waveguide is disclosed. Perturbations are introduced into the waveguide core to couple power between the two polarization modes. A model calculation shows that the perturbation length may be of the order of the correlation length. The inventive waveguide is robust in that polarization mode dispersion is reduced even if perturbations are impressed on the fiber after manufacture.

Abstract: An anti-abrasion and rockering system for an in-line skate. The skate includes a skate boot mounted on a chassis. The chassis includes two sidewalls which are parallel and opposite to each other. Each sidewall has a row of holes formed therein, such that the holes on the first sidewall align with and are opposite to the row of holes on the opposing sidewall. Two of the opposing sets of holes are oblong. A plurality of axles are disposed in the holes on the chassis so that the wheels are rotatably mounted on the axles and between the sidewalls of the chassis. The anti-abrasion and rockering system for the skate includes bushings disposed in the holes in the chassis. The bushings disposed in the oblong holes slide up and down in the holes. An anti-abrasion and rockering plate is disposed on the exterior of each sidewall. Each plate has a first and second row of holes for accommodating the axles.

Abstract: A single mode optical fiber suitable for use in an amplified fiber optic system which includes an inner glass core doped with a rare earth element and an outer transparent glass cladding. The fiber exhibits a plurality of mode coupling sites formed at regular intervals along the length of the fiber which provides for a reduced DOP. The sites are formed by a twist at regular intervals along the fiber length by applying a torque to the fiber. The method of forming the fiber is also disclosed.

Abstract: A voice-controlled wheelchair has a control system having a plurality of modes of operation in each of which only a limited number of commands for moving the wheelchair are executed. The commands are entered by a throat-engaging microphone, and backup commands are also recognized, including a command based on an excited utterance to stop the wheelchair. The control system is switchable by voice command between a first condition in which it executes other commands and a second condition in which it does not execute other commands.

Abstract: A method for processing or modifying programs and databases containing abbreviated date fields to achieve year 2000 compliancy includes examining an original database to ascertain the location of date fields, creating a supplementary PALM file that includes fully expanded date fields representative of corresponding date fields in the original database and modifying instructions or modules of the original program to access the PALM file for date information instead of the original database. The PALM file contains fully expanded date representations of abbreviated date fields of the original database. The PALM file also includes record identifiers and field identifiers to enable the modified program to access the required date information. Portions of the program requiring modification are identified by scanning for keywords that are generated from an examination of the database and/or from field layout definitions.

Abstract: A braking system for an in-line skate. The skate includes a boot mounted on a chassis. A cuff is rotatably mounted on the chassis. The chassis has a plurality of wheels rotatably mounted thereon. The braking system for the skate includes a brake pad housing which is either fixedly or pivotally attached to a rear portion of the cuff, a brake pad disposed in the housing, and a roller arm rotatably mounted on the chassis. The roller arm is spring loaded so that when the brake is not in use, the roller arm is disposed above the wheels. The roller arm has a bearing assembly disposed therein, so that when the brake is actuated by a rearward rotation of the cuff, the brake pad engages the bearing assembly of the roller arm, thereby causing said bearing assembly to engage said at least one of the wheels to slow and/or stop the skate.

Abstract: A single mode optical fiber suitable for use in an amplified fiber optic system which includes an inner glass core doped with a rare earth element and an outer transparent glass cladding. The fiber exhibits a plurality of mode coupling sites formed at regular intervals along the length of the fiber which provides for a reduced DOP. The sites are formed by a twist at regular intervals along the fiber length by applying a torque to the fiber. The method of forming the fiber is also disclosed.

Abstract: A compact monolithic interferometric switch such as a Mach-Zehnder switch is formed such that one of the waveguide paths between the input and output couplers contains a material having exhibits a resonant nonlinearity, whereby its refractive index changes when pump power propagates through it. Each of the waveguide paths has a different propagation constant whereby signal light is subjected to a different delay in each path when no pump power is propagating through the rare nonlinear path. An input signal applied to the input of the switch appears at a first output terminal when the pump power does not propagate through the nonlinear path, and it appears at a second output terminal when the pump power is applied to the nonlinear path. Switching occurs at relatively low levels of pump power.

Abstract: An M.times.O multiplex/demultiplex device is disclosed. An M.times.N coupler is connected to an N.times.O coupler by phase shifting means. The phase shifting means provide N paths between the couplers, each path having an optical path length different from every other optical path length. The coupling region of the M.times.N coupler must provide for substantially uniform division of light power among the coupler branches when M are the launch ports. Similarly, the coupling region of the N.times.O coupler must provide for substantially uniform division of light power among the coupler branches when O are the launch ports. A preferred embodiment includes two fused waveguide fiber couplers with dissimilar waveguide fibers used as the phase shifting means.

Abstract: Disclosed is a single mode optical waveguide fiber having periodic perturbations in the core to provide a birefringence which mixes the polarization modes of launched light. In addition, perturbations are introduced into the core which serve to manage total dispersion. The total dispersion of pre-selected segments of the waveguide are caused to change sign so that the sum of products, total dispersion times length, algebraically add to a pre-selected value. The two distinct core perturbation types serve to control both polarization mode dispersion and total dispersion. Methods for making the subject waveguide are also discussed.

Abstract: A single-mode optical fiber suitable for the transmission of solitons has a refractive index profile that changes along the length of the fiber to provide a fiber dispersion that monotonically decreases along the fiber from one end thereof to the other. The fiber includes a core of maximum refractive index n.sub.1 and a radius a, surrounded by cladding material having a refractive index n.sub.2 which is less than n.sub.1. The fiber core includes a central region that extends to the longitudinal axis of the fiber and an outer region, the inner and outer regions being separated by a region of depressed refractive index. The inner radius a.sub.1 of the region of depressed refractive index is greater than zero and the maximum radius a.sub.o of the region of depressed refractive index is less than a.

Abstract: An compound core optical waveguide fiber designed for high data rate or single channel or WDM systems which may include optical amplifiers. The waveguide is characterized by a core having two or three regions wherein the refractive index can be varied. The relative size of the regions may also be varied. By adjusting these variables, the desired mode field diameter, zero dispersion wavelength, dispersion slope and cut off wavelength were obtained. The optical properties are chosen to limit non-linear effects while maintaining low attenuation and acceptable bend performance. In addition, the residual stress within the waveguide is maintained at a low level to limit stress induced birefringence. The low residual stress in the uncoated waveguide, together with a dual coating system having selected moduli and glass transition temperatures results in low polarization mode dispersion.

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 Mach-Zehnder filter includes an input coupler for splitting an input signal into N equal output signals, where N>2, and a signal combining coupler for combining N optical signals into a single output signal. It further includes N optical waveguide fibers for connecting the N outputs from the input coupler to the signal combining coupler. Each of the N optical fibers subjects the light propagating therethrough to a delay that is different from the delay experienced by light propagating through each of the other optical fibers. This Mach-Zehnder filter exhibits greater finesse per stage than previous Mach-Zehnder devices, finesse being the ratio of the wavelength separation between adjacent peaks to the peak widths.

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: 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: 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: A fiber optic coupler is formed by assembling a coupler preform having two concentric glass tubes having a gap between them. The shape and/or size of the inner tube relative to the shape and/or size of the outer tube is such that a plurality of output optical fibers can be equally spaced in the gap. An input optical fiber is disposed in an aperture in the inner tube. The input and output fibers extend through the midregion of the resultant coupler preform. The midregion is heated to collapse it about the fibers, and the central portion of the midregion is stretched to reduce the diameter over a predetermined length.

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.