Abstract: Packages for long period fiber gratings and other optical components (and methods for forming the packages) are described. According to an aspect of the invention, a hollow tube surrounding an optical fiber containing a long-period grating is collapsed in two areas, forming a seal at each end of the tube. According to another aspect of the invention, a hollow tube with a shelf section at each end surrounds an optical fiber containing a long-period grating. The hollow tube is sealed at each end with a fused frit. According to another aspect of the invention, a hollow tube surrounding an optical fiber containing a long-period grating is sealed at each end with a glass plug.

Abstract: Packages for long period fiber gratings and other optical components (and methods for forming the packages) are described. According to an aspect of the invention, a hollow tube surrounding an optical fiber containing a long-period grating is collapsed in two areas, forming a seal at each end of the tube. According to another aspect of the invention, a hollow tube with a shelf section at each end surrounds an optical fiber containing a long-period grating. The hollow tube is sealed at each end with a fused frit. According to another aspect of the invention, a hollow tube surrounding an optical fiber containing a long-period grating is sealed at each end with a glass plug.

Abstract: Packages for long period fiber gratings and other optical components (and methods for forming the packages) are described. According to an aspect of the invention, a hollow tube surrounding an optical fiber containing a long-period grating is collapsed in two areas, forming a seal at each end of the tube. According to another aspect of the invention, a hollow tube with a shelf section at each end surrounds an optical fiber containing a long-period grating. The hollow tube is sealed at each end with a fused frit. According to another aspect of the invention, a hollow tube surrounding an optical fiber containing a long-period grating is sealed at each end with a glass plug.

Abstract: Packages for long period fiber gratings and other optical components (and methods for forming the packages) are described. According to an aspect of the invention, a hollow tube surrounding an optical fiber containing a long-period grating is collapsed in two areas, forming a seal at each end of the tube. According to another aspect of the invention, a hollow tube with a shelf section at each end surrounds an optical fiber containing a long-period grating. The hollow tube is sealed at each end with a fused frit. According to another aspect of the invention, a hollow tube surrounding an optical fiber containing a long-period grating is sealed at each end with a glass plug.

Abstract: Optical gratings having a range of possible Bragg wavelengths can be produced using a single phase mask by exposing the mask to a non-collimated spatially filtered beam of light. A spatial filter removes high spatial frequency components from the beam, and a focusing system directs the filtered beam to a phase mask. A rate at which the beam is focused and a spacing between the phase mask and a photo-sensitive waveguide are varied to produce gratings in the waveguide having a range of possible periods.

Abstract: Packages for long period fiber gratings and other optical components (and methods for forming the packages) are described. According to an aspect of the invention, a hollow tube surrounding an optical fiber containing a long-period grating is collapsed in two areas, forming a seal at each end of the tube. According to another aspect of the invention, a hollow tube with a shelf section at each end surrounds an optical fiber containing a long-period grating. The hollow tube is sealed at each end with a fused frit. According to another aspect of the invention, a hollow tube surrounding an optical fiber containing a long-period grating is sealed at each end with a glass plug.

Abstract: The invention comprises a spatial filter and a method of spatially filtering a laser beam, particularly a high power laser beam. The inventive spatial filter and method of use is especially suited for use in an optical system for writing index gratings in optical waveguides. The invention provides a method of writing gratings in optical waveguide fiber that results in improved grating performance.

Abstract: A Mach-Zehnder filter is provided with a strongly aperiodic transfer function including a broad, sharply defined pass band. The filter can be used in conjunction with optical amplifiers.

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 Mach-Zehnder filter is provided with a strongly aperiodic transfer function including a broad, sharply defined pass band. The filter can be used in conjunction with optical amplifiers.

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 method for side writing Bragg gratings, having minimal birefringence, in a waveguide structure is disclosed. The method employs the orientation of the polarization direction of the writing light beam relative to the long axis of the waveguide structure together with the orientation of the intrinsic birefringence slow axis to effectively minimize birefringence in the subject grating.

Abstract: A variable period amplitude grating mask for use in making a long period Bragg grating is realized by a helically coiled spring. Stretching or compressing the spring changes the periodicity of the mask. A photosensitive optical waveguide, planar or fiber, is positioned within the spring coils along the major axis of the spring. Actinic radiation is incident on the masked waveguide, and induces an index perturbation in the waveguide having the periodicity of the mask. Different spring coil sizes and/or orientation of the waveguide with respect to the mask provide linear and nonlinear (chirped) grating periods. A device and method are described.

Abstract: A method and apparatus for writing a Bragg grating in a photosensitive optical waveguide is disclosed. The novel method comprises an interferometer having precisely adjustable light collecting and directing components. A phase mask illuminated with ultraviolet light is used as the interferometer light source. The adjustability of the interferometer allows the writing of Bragg gratings for filtering wavelengths in the range 1275 nm to 1575 nm while adjusting the appropriate interferometer elements by only +/-0.75.degree. each.

Abstract: Fiber Bragg gratings of low reflectivity are given a squared reflectivity function in the form of a tophat configuration having a flat top and lacking undesirable side lobes. Such a reflectivity function for a fiber Bragg grating is achieved by interfering a diffracted beam with a plane wavefront beam so as to impose a sinc function on the resulting interference pattern that imprints the grating on an optical fiber.

Abstract: Apparatus for forming a refractive index grating in a waveguide in accordance with the invention includes a waveguide formed from a material that changes its index of refraction when exposed to a beam of optical radiation, a source of coherent optical radiation for forming a beam of radiation, a mirror arranged to intercept a first part of a beam and to reflect the first part of the beam through an angle, and a phase delay plate arranged to intercept a second part of the beam for delaying the second part of the beam propagating through the plate, in which the mirror and the phase delay plate are arranged so that the first part of the beam and the second delayed part of the beam form an interference pattern on the waveguide for changing the index of refraction of the waveguide, in a pattern corresponding to the interference pattern for forming an index grating in the waveguide.

Abstract: To couple the elliptical mode field light beam of a laser radiation source to a circularly symmetric single-mode optical fiber, the end of the fiber is provided with an anamorphic lens. The double wedge-shaped lens provides high coupling efficiency and is easily constructed. Other anamorphic lenses are also disclosed. A single wedge lens can provide high coupling efficiency if it is formed on the end of a coupling fiber which has a core that is elliptically-shaped in cross-section, the line of intersection of the two surfaces forming the lens being aligned with the major axis of the elliptical fiber core.

Abstract: An optical system for coupling a laser radiation source to a circularly symmetric single-mode optical fiber. The laser radiation source produces a beam of light having an elliptical mode field. The input end of a coupling fiber, which has a core that is elliptically-shaped in cross-section, is situated in light receiving relationship with respect to the source. The coupling fiber is oriented with respect to the source such that the mode field of the source is aligned with the coupling fiber core to provide the most efficient coupling of light from the source to the fiber. Means such as an evanescent coupler couples light from the output end of the fiber to the circularly symmetric fiber.

Abstract: Thermoelectric heat pumps are individually located at multiple flexures functioning to support a primary mirror which mirror reflects light from an aluminum mask onto a semiconductor wafer. The heat pumps are selectively energized to apply thermal stresses by heat or cold application at the flexures into the primary mirror suspension to compensate for distortions in the image transfer between the mask and the semiconductor wafer.