Abstract: A free space optical tap and multi/demultiplexer unit includes at least one optical unit that can tap off an optical signal from and/or add an input optical signal to a received FSO signal. The optical unit propagates the resulting optical signal, via free space, to a next optical unit of the system. The optical unit can include a holographic grating to diffract a portion of the received FSO signal to an optical detector and/or diffract an input optical signal to form part of a free space optical output signal. In addition, the FSO signal can include component signals of different wavelengths, with each optical unit of the system being wavelength specific to a different one of the wavelengths of the FSO signal.

Abstract: Disclosed is the use of a polymer material in an optical waveguide structure. The polymer material may be used in either the cladding or the core material of an optical waveguide. The use of polymer material as such is advantageous in that the index of refraction of polymer material varies significantly with changing temperature. The polymer material is subjected to a heating mechanism and/or a cooling mechanism to manipulate the index of refraction as desired.

Abstract: An optical fiber assembly includes an optical fiber and ferrule. The ferrule's face is partitioned into several regions. Optical elements can be formed on the regions to diffract light incident on the ferrule. Alternatively, the ferrule's face may have several reflective facets. Light incident on the end of the optical fiber propagates to a communications detector. Light incident on the ferrule's face is redirected to tracking detectors, each arranged to receive the redirected light from a preselected region of the ferrule. The output signals of the tracking detectors are used to adjust the alignment between the incident light and the assembly. Alternatively, tracking fibers or a quadrant cell may be used to directly receive light that would otherwise be incident on the ferrule's face.

Abstract: An optical tracking system for use in an optical receiver of an optical communication system includes a first focus unit, a tracker, and an optical fiber having an angled tip. The first focus unit receives an optical signal to be tracked and focuses it on the angled tip of the fiber. The fiber is connected to a communications detector of the optical communication system. In addition, the angled tip of the fiber reflects a portion of the focused optical signal to the tracker. The tracker processes the reflected portion of the optical signal to correct for any misalignment between the optical signal and the optical receiver.

Abstract: A laser beam is used to ablate the outer cladding of an extended portion of an optical fiber. The laser beam is focused at a tangential point on the outer cladding. The laser can be rotated around the optical fiber while the optical fiber is held stationary. Alternatively the optical fiber can be rotated while the focal point of the laser beam is kept at a constant position.

Abstract: An optical attenuator and method, the optical attenuator having a core which is covered by a cladding material with a section of polymer cladding of an identifiable length. The polymer cladding has an index of refraction that varies with temperature. A thermal device such as a thermoelectric heater or cooler is placed adjacent to the polymer cladding to control the temperature of the cladding. The index of refraction of the polymer cladding is manipulated by changing its temperature by supplying power to the thermal device. The index of refraction of the polymer cladding will range from values below and above the index of refraction of the core material. A light wave transmitted through the core will experience a degree of attenuation due to leakage into the polymer cladding material when the index of refraction of the polymer cladding is equal to or greater than the index of refraction of the core. The light wave may be either attenuated or blocked entirely.

Abstract: An optical coupler and method is disclosed in which a polymer material is employed to optically couple a first and second waveguide in a transfer region. In the transfer region, the first and second waveguides are positioned in parallel separated by a specific distance. The polymer material has an index of refraction which varies with temperature. The optical switch device is controlled by adjusting the temperature of the polymer material to obtain a desired index of refraction, thereby resulting in the desired transfer of an optical wave from on waveguide core to another.

Abstract: The present invention entails an extended optical fiber having an extended portion and a normal portion. The extended portion is located at an end of the extended optical fiber and has a cladding of reduced diameter in relation with the cladding of the normal portion. A common core runs throughout the normal and extended portions. The thickness of the cladding in the extended portion is sufficient to ensure that the propagation characteristics of the extended optical fiber are unaffected through the extended portion. The extended portion provides the advantage of being easily inserted, for example, into a restrictive input port of a photodetector or other suitable device. Also disclosed is a method for producing the extended optical fiber which employs a focused laser to ablate the cladding material of the optical fiber.

Abstract: A Mach-Zender interferometer employing a section of polymer cladding in one branch. The polymer cladding has an index of refraction that varies with temperature. The temperature of the section of polymer cladding is adjusted to cause a corresponding change in the phase of the laser light flowing through the waveguide core bounded by the polymer cladding to effect a desired switching or modulation of the laser light.

Abstract: An optical switch having a straight waveguide core with a lateral waveguide core extending therefrom. A region of polymer material is disposed in the straight waveguide core to deflect optical waves from the first waveguide core into the lateral waveguide core depending on the relative indexes of refraction between the first waveguide core and the polymer material. The temperature of the polymer material is adjusted, thereby adjusting the index of refraction of the polymer material so as to cause the deflection in a switched state, and to allow light radiation to pass through the polymer material in an un-switched state.

Abstract: An optical beam compressor formed of light transparent material for compressing optical signals emitted from an end of an optic fiber. The compressor has a substantially tapered shape extending between a first surface or base having a cross-sectional area, and a second surface or head having a cross-sectional area less than the base area. The compressor has an index of refraction greater than the index of refraction of the environment in which it is disposed, and can be positioned between the end of the optic fiber and a photodetector. Optical signals are provided from the free end of the fiber to the base of the compressor wherein the signals are compressed and transmitted or directed to the photodetector for detection.

Abstract: A mechanically stable self-aligned optical switch having a low insertion loss is achieved by employing two silica optical structures containing a plurality of waveguides. The waveguides within each structure are arranged in a common plane. It is possible to achieve such silica optical structures by cleaving a monolithic silica optical structure. In one embodiment, the structures are disposed on respective flat surfaces of moveable and fixed bases that are aligned in a common plane. The structures are further positioned with their cleaved edges adjacent to and facing one another. In this manner, the waveguides of the cleaved structures are effectively self aligned in the direction normal to the flat surface of the bases. In operation, the moveable base moves in the direction along the cleaved edges to selectively provide connections between the waveguides in each structure.

Abstract: A method of making a silicate optical waveguide structure for transforming an optical beam of a first modal spot size to a beam of a second modal spot size includes the step of selecting an irradiation energy which is at least partially absorbed by the cladding of the structure. A variable dosage of radiation is then provided along the length of the structure. The radiation has an energy equal to the selected irradiation energy so that a refractive index change of the cladding is greater than a refractive index change of the core.

Abstract: The present invention provides polarization-independent optical devices by reducing or eliminating strain-induced birefrigence associated with prior device structures. In a first embodiment, an optical device is produced comprising a doped silica substrate having a coefficient of thermal expansion between 8.times.10.sup.-7 .degree. C..sup.-1 and 15.times.10.sup.-7 .degree.C..sup.-1. On the doped silica substrate is formed a doped silica waveguiding structure having a coefficient of thermal expansion between 8.times.10.sup.-7 .degree. C..sup.-1 and 15.times.10.sup.-7 .degree. C..sup.-1. Alternatively, the coefficient of thermal expansion of the doped silica substrate is selected to be approximately 90% to 110% of the coefficient of thermal expansion of the doped silica waveguiding structure. In another aspect, the present invention provides an optical device comprising a doped silica substrate having a doping gradient from a lower surface to an upper surface.

Abstract: In accordance with the invention, a polarization independent optical device is fabricated by building the waveguide structure on a silicon substrate, adding a reinforcing layer of glass and removing regions of the silicon substrate underlying the waveguide structure. Alternatively, a reinforcing layer of glass can be added after the silicon in removed. Removal of the silicon underlying the waveguide structure eliminates polarization dependent spectral effects by eliminating the source of compressive strain, and the resulting glass reinforced structures are sufficiently robust for practical applications.

Abstract: Efficient conversion between the LP.sub.01 and the LP.sub.11 modes in a two-mode optical fiber is realized in a fiber grating fabricated by forming a series of longitudinally-spaced cuts in the fiber cladding, and then annealing the fiber in the region of the cuts. The latter step uses the surface tension of the molten glass to transform the corrugation on the cladding into a sinusoidal deformation of the fiber core.

Abstract: A method of preparing a waveguiding structure, of the type comprising an optical waveguide supported by a semiconductor substrate, for splicing to an optical fiber, is described. In accordance with the disclosure, a layer of glass is deposited over a distance from the end of said waveguide, and the underlying semiconductor substrate is removed over a portion of said distance. The resulting modified waveguide can then be fused to optical glass fibers using standard fusion machines.

Abstract: An asymmetric hyperbolic microlens on the end of a single-mode optical fiber enhances the fiber's coupling to elliptical laser beams. The lenses, with controlled eccentricity ratios, are made by micromachining the end of the fiber with a pulsed CO.sub.2 laser as the fiber is directed, preferably by computer control, about the focused laser beam. Coupling efficiencies of 90 percent (-0.75 dB) have been realized with single transverse mode lasers at a wavelength of 0.98 .mu.m having an approximately 3 to 1 beam ellipicity. With multimode lasers at 1.48 .mu.m having similar elliptical beams, the asymmetric lenses demonstrate an almost 2 dB increase in coupling efficiency over symmetric hyperbolic microlenses. Such lasers are useful to pump erbium-doped fiber amplifiers. About 120 mw was coupled from such a laser into single-mode fiber.

Abstract: This invention is directed toward joining an optical fiber to a waveguide on a silicon or silica substrate. In a preferred embodiment, a discontinuity such as a notch is provided in the substrate along each side of a waveguide. The notches, which extend back from the end of each waveguide form air gaps between the ends of adjacent waveguides. Now, when an optical fiber is butt coupled to a waveguide on a substrate with adhesive, the notches at either side of the waveguides prevent adhesive from flowing along the edge of the substrate and onto the end of an adjacent waveguide. In addition, the adhesive flows around and encapsulates the substrate projections defined by the notches along the ends of the waveguide to provide a sturdy butt connection.

Abstract: This invention is directed toward joining, with glass, a waveguide supported by a substrate to an optical fiber. In a preferred embodiment, a glass material which melts at a temperature that is lower than the temperature to which the waveguide can be safely heated is applied to either the optical fiber and/or the waveguide. The glass material is then heated to cause it to connect the optical fiber to the waveguide. A feature of the invention is the presence of heat breaks in the substrate upon which the waveguide resides to thermally isolate the end of each waveguide and the underlying substrate from adjacent waveguides and the portions of the substrate which underlie said adjacent waveguides. The heat breaks restrict heat from being conducted along the end of the substrate from one waveguide region to adjacent waveguide regions when heat is being applied to make a connection.