Abstract: A polarization compensator is disclosed for passing light in a predetermined wavelength range. The compensator has unequal output orthogonal polarizations for light launched into the device within a specific wavelength range. A waveguide having a blazed grating having a blaze angle &thgr;b1 of between 20° and 45° with respect to the optical axis of the waveguide exhibits a tap efficiency difference for orthogonal polarizations for offsetting and lessening a polarization dependence of the device. This waveguide is optically coupled with the optical device requiring polarization compensation. The grating is oriented about its optical axis to lesson the inequality in output orthogonal polarizations for light launched into the optical device.

Abstract: The invention relates to the design of laser collimators for free space through-the-air optical links. The laser collimator provides means for expanding the diameter of a light beam emitted from the end of a monomode optical fiber that has been optical coupled to a semiconductor laser diode and projecting through free space the expanded beam as a low divergence beam of substantially parallel rays. The laser collimators disclosed are compact, simple to make, and overcome many of the deleterious effects that result from the requirement that the air-glass surface terminating the end of the monomode fiber coupled to the semiconductor laser is not normal to the axis of the optical fiber. Means are also disclosed for increasing the divergence of the cone of light emitted from the tip of an optical fiber thereby enabling the construction of laser collimators with larger expansion ratios in a compact size.

Abstract: An polarization compensator is disclosed for passing light in a predetermined wavelength range. The compensator has unequal output orthogonal polarizations for light launched into the device within a specific wavelength range. A waveguide having a blazed grating having a blaze angle &thgr;bl of between 20° and 45° with respect to the optical axis of the waveguide exhibits a tap efficiency difference for orthogonal polarizations for offsetting and lessening a polarization dependence of the device. This waveguide is optically coupled with the optical device requiring polarization compensation. The grating is oriented about its optical axis to lessen the inequality in output orthogonal polarizations for light launched into the optical device.

Abstract: A method is disclosed wherein optical structures such as Bragg gratings can be written into planar waveguides disposed on a substrate. By employing the method of this invention, a polarization insensitive device can be made. Such relatively thin planar waveguides disposed on a substrate are inherently polarization sensitive and the structure itself is birefringent. By writing structures in the waveguides or by simply writing a refractive index change in the waveguide by limiting the beam width at the waveguide layer to less than or equal to the thickness of the waveguiding layers on the substrate, in combination with conventional wider beam writing techniques, polarization sensitivity can be lessened or obviated.

Abstract: A polarization compensator is disclosed for passing light in a predetermined wavelength range. The compensator has unequal output orthogonal polarizations for light launched into the device within a specific wavelength range. A waveguide having a blazed grating having a blaze angle &thgr;b1 of between 20° and 45° with respect to the optical axis of the waveguide exhibits a tap efficiency difference for orthogonal polarizations for offsetting and lessening a polarization dependence of the device. This waveguide is optically coupled with the optical device requiring polarization compensation. The grating is oriented about its optical axis to lesson the inequality in output orthogonal polarizations for light launched into the optical device.

Abstract: A method is disclosed wherein optical structures such as Bragg gratings can be written into planar waveguides disposed on a substrate. By employing the method of this invention, a polarization insensitive device can be made. Such relatively thin planar waveguides disposed on a substrate are inherently polarization sensitive and the structure itself is birefringent. By writing structures in the waveguides or by simply writing a refractive index change in the waveguide by limiting the beam width at the waveguide layer to less than or equal to the thickness of the waveguiding layers on the substrate, in combination with conventional wider beam writing techniques, polarization sensitivity can be lessened or obviated.

Abstract: A method is disclosed wherein optical structures such as Bragg gratings can be written into planar waveguides disposed on a substrate. By employing the method of this invention, a polarization insensitive device can be made. Such relatively thin planar waveguides disposed on a substrate are inherently polarization sensitive and the structure itself is birefringent. By writing structures in the waveguides or by simply writing a refractive index change in the waveguide by limiting the beam width at the waveguide layer to less than or equal to the thickness of the waveguiding layers on the substrate, in combination with conventional wider beam writing techniques, polarization sensitivity can be lessened or obviated.

Abstract: A method of fabricating a strongly photosensitive optical waveguide is comprised of locally heating at least a portion of a weakly photosensitive optical waveguide for a period of time sufficient to increase the density of defects associated with photosensitivity in the heated portion of the waveguide core.

Abstract: An index grating is imprinted in the core of an optical fiber using a specially designed silica glass phase grating mask. The phase mask is held in close proximity to the optical fiber. Laser irradiation of the phase mask with ultraviolet light at normal incidence imprints (photoinduces) into the optical fiber core the interference pattern created by the phase mask.

Abstract: Efficient, narrow-band rocking filters have been made in polarization-maintaining monomode optical fiber by photoinducing periodic birefringent gratings along the length of the fiber. These gratings, fabricated with a period chosen to provide synchronous coupling between the two principal states of polarization of the LP.sub.01 mode at a preselected wavelength, gently rock to and fro the principal polarization axes of the fiber. To photoinduce the grating, the fiber is exposed periodically along its length to a U.V. light beam which is incident at right angles to the geometrical axis of the fiber and is directed .pi./4 radians with respect to the principal axes. Efficient polarization mode conversion at 1.3 .mu.m with the fiber gratings are obtained.

Abstract: A two-channel optical fiber fused coupler comprising two optical fibers, each with a core and cladding, fused together at a narrow tapered waist. The first channel is at a wavelength of .lambda..sub.1 and the second channel is at a wavelength of .lambda..sub.2 where .lambda..sub.2 is longer than .lambda..sub.1. The coupler is fabricated to have a characteristic wavelength .lambda..sub.0 such that for wavelengths .lambda..sub.2 longer than .lambda..sub.0 coupling occurs and for wavelenghts .lambda..sub.1 shorter that .lambda..sub.0 the light at .lambda..sub.1 is core guided throughout the coupler and thus does not couple across.

Abstract: This invention relates to a method of creating an index grating in an optical fiber comprising disposing a slit mask containing one or more slits over a side of an optical fiber, illuminating the fiber through the slit mask by substantially monochromatic ultraviolet light for a short interval, whereby an index grating line is created and stored in the core of the fiber.

Abstract: A fused twin biconical taper fiber optic splitter comprised of a pair of non-identical monomode or nominally monomode optical fibers having predetermined cladding diameters fused at respective narrowed waists, the cladding diameter of one fiber before coupler fabrication being greater than the other, whereby wavelength selective coupling between one and the other fiber is obtained.

Abstract: A fused twin biconical taper fiber optic splitter comprised of a pair of non-identical monomode or nominally monomode optical fibers having predetermined cladding diameters fused at respective narrowed waists, the cladding diameter of one fiber before coupler fabrication being greater than the other, whereby wavelength selective coupling between one and the other fiber is obtained.

Abstract: The present disclosure makes a grating assisted optical waveguide device.

Abstract: New types of narrowband wavelength selective optical devices are described. Various configurations are possible, according to the invention, that perform as narrowband wavelength selective transmission or reflection filters or as narrowband wavelength selective optical taps or combiners. The optical devices of the invention include a 3 dB optical directional coupler and wavelength selecting elements such as Bragg reflection gratings or Fabry-Perot resonators usually positioned in optical symmetry with respect to the directional coupler. Two or more wavelength selecting elements can be used to obtain desired filtering characteristics.

Abstract: A method of forming a single mode biconical fiber optic coupler comprising holding 2 or more optical fibers parallel to and in contact with each other at spaced apart locations, exerting equal tension in opposite directions to the fibers at said spaced apart locations to stretch the fibers, fusing the fibers over a waist region, and scanning the tip of a flame from a microtorch back and forth along the fibers at a speed which is at least five times the speed of stretching of the fibers. This results in an overcoupled low loss coupler, a pressure or a temperature sensor, comprised of at least a pair of monomode optical fibers fused and parallel at a stretched waist portion, each having biconical tapers at opposite ends of the waist portion, the coupler having exhibited at least about 500 power transfer cycles during stretching formation of the waist portion.

Abstract: A fiber optic directional coupler comprising a pair of strands of single mode optical fiber having biconical tapers whereby the electromagnetic field within the fibers extend virtually to the cladding outside surface, the strands in the region of the tapers being bent in opposite directions and positioned with their cladding in contact over a length of the waist of the tapers, the cladding in contact being narrowed on one side, flat, and polished, whereby the field is coupled from one strand to the other.

Abstract: An optical coupler for single mode optical signals having a tunable (variable) coupling ratio, and a method of fabricating the coupler. A pair of virtually identical optical fibers are fused together at a narrowed waist region, each fiber being formed of a core and cladding, each being tapered toward the waist in such a manner as to ensure adiabatic propagation of light in the structure. An optical signal carried by one fiber first passes through a decreasing taper region and then passes through an increasing taper region of one or the other fiber (or both). The decreasing taper rate of the input portion of one fiber is such that the optical signal radiates out of the core (where V=1 locally) and into the cladding, as it approaches the waist. The increasing taper rates of the output portions of the two fibers are such that a predetermined coupling ratio is obtained.

Abstract: An index grating is imprinted in the core of an optical fiber using a specially designed silica glass phase grating mask. The phase mask is held in close proximity to the optical fiber. Laser irradiation of the phase mask with ultraviolet light at normal incidence imprints (photoinduces) into the optical fiber core the interference pattern created by the phase mask.