Abstract: An optical physical condition sensor includes an optical fiber resonant cavity into which optical energy, including wavelengths resonatable within the cavity, is introduced. External physical conditions, such as temperature or pressure, change the effective optical path length within the cavity to cause a corresponding change in the cavity's resonant characteristics. Changes in the sensed condition can be determined as a function of changes in the wavelength of optical energy peaks or minimas in the cavity or changes in the cavity's finesse characteristics.

Abstract: An improved method of forming an optical fiber preform includes separately forming a rod-like inner member and a hollow tube-like outer member by a soot glass deposition technique. The inner member is inserted into the outer member, while they are both in their unconsolidated state, and the asssembled parts heated to cause the outer member to collapse about the inner member and form a preform. The resulting preform can be drawn in one or more stages to provide an optical fiber having sharp step change in its index of refraction between the core and the cladding, a superior quality core to cladding interface, and improved optical transmission qualities. The inner and outer members can, if desired, be partially consolidated but for an unconsolidated layer at their interface prior to heating the outer member to cause it to join with the inner member.

Abstract: A coupling device for forming optically efficient end-to-end connections between optical fibers having a common core and cladding geometry but different relative dimensions and cross sections includes forming a segment of optical fiber having the same general geometry of the fibers to be coupled but which varies between relatively enlarged and reduced cross sections along its length. The coupling device is severed along its length at appropriate points to match the relative cross sections of each fiber to be coupled to thereby allow a butt type coupling between optical fibers of the same general geometry but with differing cross sectional areas. The coupling devices may be manufactured by drawing a starting fiber having the same geometry of the fibers to be coupled and varying the drawing speed to create enlarged and reduced cross section portions. The starting fiber may then be severed at the reduced cross section portions to provide the coupling device.

Abstract: A fiber laser sensor is comprised of two fiber lasers which are each optically coupled to a third fiber so that energy is exchanged between each of the laser fibers and the third fiber. The coupling is accomplished by arranging the laser fibers parallel to and on either side of a third fiber and properly spacing the three fibers to produce optical coupling along the length of the fibers. The central fiber ends are non-reflective so that light generated by one of the lasers and coupled to the central fiber is lost except for a small fraction of the energy transferred to the other laser. Accordingly, the structure operates with the least loss when the two lasers oscillate at a common frequency but 180.degree. out-of-phase. The resonant cavities of the two fiber lasers are made non-identical by making the path length one cavity slightly longer than the other to produce Vernier tuning of the laser resonant frequency orders relative to each other with only one common resonant frequency.

Abstract: A wavelength filtering device and system in which an optical resonant cavity is laterally coupled to a trunk waveguide carrying a broad range of wavelengths in the optical spectrum. The filtering cavities may be linear optical fiber segments or fiber segments closed at their ends in the shape of a loop. The devices may include single or multiple optical cavities or hybrid filtering utilizing both dispersive and resonant functions.

Abstract: A single-mode optical fiber transmission line suited for coupling to another fiber through a laterally coupled splice includes a core having a selected diameter, a cladding layer that surrounds the core and has a cladding thickness between one and two core diameters, and an auxiliary cladding into which the optical fiber is nested. The auxiliary cladding has an index of refraction not substantially greater than that of the cladding layer that surrounds the core, an inside dimension greater than that of the outside dimension of the optical fiber, at least partially surrounds the optical fiber and is attached to the optical fiber at least along one lineal connection zone.

Abstract: A stressed-core rotationally non-symmetric optical fiber includes a longitudinally extending substrate fabricated from an optical energy transmitting material including an embedded tensional stress member. The substrate is provided with stress-altering discontinuities, such as longitudinally extending slots and notches, that are effective to resolve the tensional stress so as to place a longitudinally extending zone within the substrate adjacent the exterior surface thereof under a compressive stress sufficient to raise the index of refraction of the zone to support guided light transmission. In a second embodiment, a longitudinally extending substrate is provided with a notch in which a light energy transmitting core is maintained in axial compression to provide a stress-induced increase in the index of refraction thereof sufficient to support guided light transmission.

Abstract: An optical fiber structure having resonant characteristics useful for coupling to an optical transmission line for removing selected wavelengths of light energy includes a light guiding structure, such as an optical fiber waveguide, which conditionally operates as a resonant cavity responsive to resonance of at least one other resonant cavity. In one embodiment, an extrinsically defined or adscititious reflectance is formed in the waveguide segment by laterally coupling an etalon cavity to the waveguide segment. In another embodiment, the waveguide segment is coupled to one or more resonant loops to form a conditional resonant loop cavity which includes the other loops. The resonant wavelength spacing for the conditional cavity and its cooperating resonant cavity are made different from one another with only one wavelength coresonantly supported in both cavities.

Abstract: A sensor or transducer having a dual path optical fiber, such as a single mode, two polarization state, waveguide fiber, utilizes the relative change in propagation constant of the paths to sense and transduce an applied force to an interference variation and ultimately an electrical signal. In this arrangement, in-phase light is introduced to both polarized states or paths in the fiber and transmitted therealong past a stress area of birefringement inducing force and ultimately combined, thereby producing in the combined beam a variation in interference which is related to the applied force. Specific structures are provided for converting isotropic forces such as pressure and temperature to anisotropic forces on the fiber to thereby produce birefringement and to also magnify the latter effect.

Abstract: A single mode optical waveguide and method for making same in which the equivalent of a core and cladding portions are made of the same material. The outer portion of the waveguide includes a tube which imposes a compressive stress through intermediate elements onto a central region of the waveguide, raising its index of refraction of that central region above that of the adjacent outer portions. The tube and other elements have different thermal coefficients of expansion and may have different freezing temperatures so that the outer elements are pressed against the core portion as the waveguide cools. A vise-like device may be used to maintain compression on the central portion and a part of the outer tube may be removed to provide for laterally coupling the waveguide with another waveguide.

Abstract: A polarization locked optical fiber having a fiber core suspended by a thin cladding web within a tube with a prestress acting along the web to fixedly polarize the core. Preferably, the tube and web are glass materials having different thermal characteristics to provide a built-in stress upon drawing of the web and tube assembly. In the preferred method, an optical fiber preform is machined to a rectangular form and drawn within an enclosing tube to provide the stressed web arrangement.

Abstract: A method for determining optical transmission characteristics and efficiencies in multi-path optical fiber networks which include, for example, inter-fiber couplings and optical components, includes introducing light energy into the entry port of the network, measuring the light energy at the network exit port or ports, exposing a portion of the light energy transmitting core in one of the optical paths of the network by, for example, removing the cladding from core, surrounding the exposed core with a material, such as a liquid, having an index of refraction greater than that of the exposed core to cause the light energy to escape and thereby quench light transmission, and remeasuring the light energy at the network exit ports. The change in energy transmission before and after light quenching is a measure of transfer characteristics of the selected optical path and related couplings.

Abstract: An optical fiber communication system for transmitting information-bearing optical signals over an optical fiber transmission line includes a signal generator coupled to the transmission line for introducing information-bearing optical signals thereonto, preferably as wavelength modulated signals, and one or more optical amplifiers for periodically, collectively amplifying the transmitted signals to overcome the effects of attenuation. Wavelength modulation is achieved by altering the resonant characteristics of an optical resonator, optically coupled to a gain medium so as to provide an output that varies between a first and second wavelength. The optical amplification is achieved by injecting, preferably via lateral optical fiber couplings, pumping beams into the optical fiber so as to effect an increase in the amplitude of the information-bearing signals by stimulated Raman scattering.

Abstract: A method for fabricating preforms for drawing into single mode optical fibers having core and cladding doped with different amounts fluorine. A pure fused silica start rod is first coated with a layer of soot which is then dehydrated, doped with a first level of fluorine, and then consolidated. This structure, which is an intermediate preform, is then drawn down until its area weighted average index of refraction is such that it would perform as a core in a fiber. If not, it is recoated and drawn down further until it will behave as a core upon further reduction in size. The intermediate preform is then recoated with another layer doped with a higher concentration of fluorine so that it will act as a cladding layer over the first fluorinated layer whose index is higher because of a lower concentration of fluorine. This final structure serves as a preform from which the desired fiber can be drawn.

Abstract: A method for forming an optical fiber from a single characteristic glass includes arraying hollow starter tubes about a central axis with each starter tube contacting its adjoining tubes along respective lines of contact to define a longitudinally extending opening about the central axis. The arrayed starter tubes are heated to cause them to fuse together along their lines of contact, and the fused starter tubes are inserted into a jacketing tube, preferably having the same physical and optical properties as the starter tubes. A pressure differential is established between the interior of the starter tubes and the tube-defined longitudinally extending opening. The tube assembly is heated to allow the established pressure differential to cause portions of the starter tubes to reform by moving toward and to the central axis to create a solid, void-free core and supporting webs. Other portions of the starter tubes expand toward and fuse to the interior surface of the jacketing tube.

Abstract: A fiber optics polarizer, wherein a multi-core polarization element is inserted to a fiber communications line and a signal to be communicated through the polarizer is carried by a first core and the other polarizations are coupled from the first core into one or more other cores to prevent propagation through the system.

Abstract: A method and apparatus for assembling fiber optic devices in multi-fiber layers to avoid the problems of misalignment and interstices. The furnace apparatus includes a mold for receiving the fiber devices and a packing piston for placing each layer of fiber devices in position. Heating is maintained in the furnace at a level so that heat penetrates from the fibers already packed into the new layer sufficiently to enable the new layer to adhere, but no more, so that the piston may be withdrawn before it adheres to the new layer.

Abstract: A wave length filter construction using fiber optics techniques and devices for selective tuning. By core coupling for a portion of the fiber lengths, a communications facility is provided and various wave length selection structures are enabled.

Abstract: A coupling structure for coupling light intelligence between fiber optic elements. Both abuttment and lateral coupling structures are presented.