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 interference filter (10, 30, 50, 70, 90, 110, 130, 150, or 190) filters selected wavelengths by dividing an input beam into two or more intermediate beams having different optical path lengths and by recombining the intermediate beams into an output beam that is modified by interference between the intermediate beams. An optical path length difference generator (20, 40, 60, 80, 100, 120, 140, 160, or 200) varies the optical path lengths of the intermediate beams by changing the physical lengths of their paths or the refractive indices of the mediums in which they are conveyed. The optical path length generator (20) of one exemplary embodiment (10) includes a spacer plate (20) that is divided into elements (22 and 24) having different refractive indices for varying the optical path lengths of the intermediate beams.

Abstract: Wavelength dispersion in an optical demultiplexer is accomplished by varying propagation constants of a central pathway traverse to the direction of wavefront propagation through the central pathway. The propagation constant can be varied by changing the dimensions or refractive qualities of the central pathway, which can be formed as a common waveguide or as a plurality of individual waveguides.

Abstract: A novel optical waveguide fiber having low total dispersion slope, relatively large mode field diameter, larger effective area, and a relatively simple core profile design is disclosed. The core refractive index profile comprises three segments. The adjustability of the height, width and location of the three core index profile segments, provides sufficient flexibility to meet a specification which calls for a dispersion shifted waveguide fiber capable of limiting four photon mixing or self phase modulation. The novel waveguide is characterized by a mode field diameter .gtoreq.7.5 microns and a total dispersion slope .ltoreq.0.070 ps/nm.sup.2 -km.

Abstract: A planar optical waveguide comprises a substrate 1, a waveguide core layer 2, at least one planar optical element, wherein said planar optical element comprises at least one optically functional interface 3 which is adjacent to a cavity 4, and an overclad layer 5. The cavity enhances the optical characteristics of the planar optical element because of the substantial difference in the refractive index of the cavity as compared to the refractive index of said waveguide core layer.

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 waveguide fiber designed for high data rate, or WDM systems or systems incorporating optical amplifiers. The optical waveguide has a compound core having a central region and at least one annular region surrounding the central region. A distinguishing feature of the waveguide core is that the minimum refractive index of the central core region is less than the minimum index of the adjacent annular region. A relatively simple profile design has the characteristics of ease in manufacturing together with, flexibility in tailoring D.sub.w to yield a preselected zero dispersion wavelength, dispersion magnitude over a target wavelength range, and dispersion slope. The simplicity of profile gives reduced polarization mode dispersion.

Abstract: A planar optical waveguide comprises a substrate 1, a waveguide core layer 2, at least one planar optical element, wherein said planar optical element comprises at least one optically functional interface 3 which is adjacent to a cavity 4, and an overclad layer 5. The cavity enhances the optical characteristics of the planar optical element because of the substantial difference in the refractive index of the cavity as compared to the refractive index of said waveguide core layer.

Abstract: Disclosed is a method of making a polarization retaining single-mode optical fiber. Longitudinal grooves are formed on opposite sides of a cylindrically-shaped core perform having a glass core surrounded by cladding glass. The core preform is inserted into a glass tube, the tube is shrunk onto the core preform, and the interface between the core preform and the tube is fused to form a solid preform having longitudinal apertures on opposite sides of the core. An etchant gas is flowed through the apertures to enlarge the apertures into holes having a substantially round cross-section. Inserted into each aperture is a stress rod formed of glass having a coefficient of expansion different from that of the cladding glass. The resultant draw blank is drawn to form a single-mode optical fiber having a core that is subjected to a stress-induced birefringence.

Abstract: A metehod of manufacturing planar optical waveguides in which a planar optical preform which is stretched to form a planar optical cane with substantially smaller cross-sectional dimensions than the original preform, and in which the optical circuitry pattern is achieved by lithographic techniques. Optical fiber preforms may be inserted in slots in a substrate to form the planar optical preform.

Abstract: An optical transmission system wherein light is transmitted from a transmitter to a receiver by at least one transmission optical fiber. The system includes a dispersion transformer which receives light from one of the components, compensates for or transforms the delay distortion of the various wavelengths transmitted through the system, and provides the next component in the system with a compensated or transformed light beam. The dispersion transformer comprises means for receiving light from one of the components and dispersing/separating the light into the plurality of spatially separated beams which are directed onto the endface of a multimode optical fiber. The position of each beam on that end-face is a function of the velocity with which the light that forms the beam propagates through the transmission optical fiber.

Abstract: The present invention pertains to an asymmetrical bidirectional optical communication system of the type comprising a central station, a plurality of user stations, and a plurality of bidirectional optical transmission paths, one of which connects the central station and one of the user stations. The central station is provided with a laser for initiating in the optical transmission path the propagation at a wavelength in the 1100-1700 nm window of a single-mode signal. Each user station is provided with a light source which initiates in the optical transmission path the propagation at a wavelength in the 700-950 nm window of a few-mode signal. Each optical transmission path comprises an optical fiber having transmission characteristics such that the single-mode signal propagates with a total dispersion less than 5 ps/km-nm and the few mode signal propagates with a bandwidth greater than 1 GHz-km.

Abstract: The present invention pertains to an optical fiber comprising a transparent core having a maximum refractive index n.sub.1 and a radius a surrounded by a layer of transparent cladding material having a refractive index n.sub.0 which is less than n.sub.1. The refractive indices n.sub.1 and n.sub.0, the radius a, and the refractive index profile of the core are designed such that:(a) .DELTA..tau..sub.j, the difference between .vertline.d(Vb)/dV.vertline..sub.j, the normalized delay time of the jth mode and .vertline.d(Vb)/dV.vertline..sub.0, the normalized delay time of the fundamental mode, is less than about 5.times.10.sup.-2 over a wide range of V-values where j is equal to 1 or 2 and represents the highest order mode that propagates with a low loss, 0 represents the fundamental mode, b is the propagation constant and V is the normalized frequency, and(b) the normalized waveguide dispersion Vd.sup.2 (Vb)/dV.sup.2 is about equal to or less than 0.2 at V-values near V.sup.1.sub.

Abstract: A single-mode transmission optical fiber may have a bandwidth much greater than that necessary to transmit a desired predetermined maximum data rate. The single-mode fiber is connected to a bandwidth limiting device comprising the serial combination of an input optical fiber, a mode converter and multimode fiber. If the multimode fiber is capable of propagating two modes, for example, the mode converter converts the LP01 signal from the transmission fiber to the LP01 and LP11 modes. These two modes propagate at different speeds through the multimode fiber. Means connected to the output end of the multimode fiber detects the two modes. If the time delay difference .DELTA.t between the two modes is small with respect to the width of a pulse in the transmitted pulse train, the pulse train will be detected without distortion. Transmission at a higher data rate causes .DELTA.t to be large with respect to pulse width.

Abstract: An optical transmission system wherein light is transmitted from a transmitter to a receiver by at least one transmission optical fiber. The system includes a dispersion transformer which receives light from one of the components, compensates for or transforms the delay distortion of the various wavelengths transmitted through the system, and provides the next component in the system with a compensated or transformed light beam. The dispersion transformer comprises means for receiving light from one of the components and dispersing/separating the light into a plurality of spatially separated beams which are directed onto the endface of a multimode optical fiber. The position of each beam on the endface of the mutimode fiber is a function of the velocity with which the light that forms the beam propagates through the transmission optical fiber.

Abstract: The various wavelength components propagating in a transmission optical fiber are delayed different times. A conventional dispersion compensation system connects the transmitted signal to wavelength dispersor means which spatially separates the different wavelength components of the transmitted signal. Each wavelength component is then propagated by an optical fiber delay line the length of which is such that the delay line fibers substantially fully compensate for the differences in propagation times of the wavelength components in the transmission fiber. The amount of light collected by the delay line array can be increased and the "dead spots" due to cladding layers between adjacent fiber cores in the array can be eliminated by optimizing fiber shape and by employing staggered, multiple arrays. Also, lens arrays and/or masks can be employed at the input end of the delay line array to reduce or eliminate the cladding effects.

Abstract: Disclosed is an optical waveguide fiber having a core surrounded by a layer of cladding material. The core is characterized in that it includes a region of depressed refractive index. The inner radius a.sub.i of this region is greater than zero, and the outer radius a.sub.o thereof is less than the core radius. By appropriately selecting the core index depression characteristics such as radial location, width, depth and shape, a fiber having the desired waveguide dispersion characteristics can be designed. Dispersion minimization over a wide wavelength range can be achieved, without adverse effect on system loss.

Abstract: Disclosed is an optical fiber for operating single polarization, single-mode at wavelength .lambda.. The fiber core is surrounded by cladding having the refractive index lower than the average refractive index of the core. The core is characterized in that it comprises a plurality of transparent laminae, each having a refractive index different from that of the adjacent laminae. The thickness of each laminae is equal to or less than wavelength .lambda..

Abstract: A process for manufacturing a preform from which is drawn an optical fiber, the core of which comprises layers of different glass composition. Layers of glass soot are deposited on the flat, longitudinally extending sides of a thin, elongated mandrel. Adjacent soot coatings have different refractive indices. A preliminary coating of cladding glass soot is deposited on the laminated soot structure. The resultant composite body is consolidated and stretched to form a rod or core structure upon which the final coating of cladding soot is deposited. The resultant composite body is consolidated and drawn into an optical fiber. In a modification of the this method, the mandrel is removed after the planar soot coatings and preliminary coating of cladding soot are deposited thereon. The resultant soot body is consolidated and processed as described previously.

Abstract: A process for manufacturing a preform from which is drawn an optical fiber, the core of which comprises layers of different glass composition. Layers of glass, adjacent ones of which have different composition, are deposited on a substrate. A process is preferred whereby layers of glass soot are deposited. The soot is consolidated and the resultant laminated glass structure is severed to form an elongated azimuthally asymmetric laminated core structure. A layer of cladding glass is added to the core structure, and the resultant preform is drawn into an optical fiber.