This application relates generally to an optical fiber for the delivery of infrared light where the polarization state of the light entering the fiber is preserved upon exiting the fiber and the related methods for making thereof. The optical fiber has a wavelength between about 0.9 m and 15 m, comprises at least one infrared-transmitting glass, and has a polarization-maintaining (PM) transverse cross-sectional structure. The infrared-transmitting, polarization-maintaining (IR-PM) optical fiber has a birefringence greater than 10.sup.5 and has applications in dual-use technologies including laser power delivery, sensing and imaging.

A method of making an optical fibre preform comprising providing a hollow outer tube of glass, providing a hollow primary capillary tube of glass with an outer diameter smaller than an inner diameter of the outer tube, positioning the primary capillary tube inside the outer tube such that an outer surface of the primary capillary tube lies against an inner surface of the outer tube along a contact line parallel to the longitudinal axes of the primary capillary tube and the outer tube, and bonding the primary capillary tube into its position inside the outer tube by directing a laser beam onto a surface of the outer tube or the primary capillary at one or more locations aligned with the contact line.

A method for forming an optical fiber preform is provided. The method includes inserting a glass core cane into a glass sleeve such that the glass sleeve surrounds a portion of the glass core cane and such that there is a gap between the glass sleeve and the portion of the glass core cane surrounded by the glass sleeve. The method further includes depositing silica soot onto at least a portion of the glass core cane and at least a portion of the glass sleeve to form a silica soot preform, and flowing gas through the gap during processing of the silica soot preform.

An apparatus for scattering light may include: an optical fiber having a first length; and a sleeve, having a second length shorter than the first length, around the optical fiber. The optical fiber may include: a core; and cladding around the core. The sleeve may include fiber-optic material. The fiber-optic material may be substantially polymer-free. An outer surface of the sleeve may be roughened to scatter the light out of the sleeve through the roughened surface. A method of forming an apparatus for scattering light may include: providing a sleeve having a first length, the sleeve having inner and outer surfaces; providing an optical fiber having a second length longer than the first length; passing the sleeve around the optical fiber or threading the optical fiber through the sleeve; and roughening at least a portion of the outer surface of the sleeve.

A method of manufacturing a preform, the method including positioning at least one glass tube in a glass outer cladding to form a preform precursor, the glass tube comprising a first open end and a second open end, forming a preform from the preform precursor, and thermally treating at least one of the preform precursor and the preform. The thermally treating including sealing the first open end and the second open end of the glass tube to form a closed tube and heating and/or cooling the glass tube to manipulate gas pressure within the closed glass tube.

A method of forming a glass preform of predetermined length comprises providing a length of glass material to be separated to form a preform length and a remaining length; forming a notch in the glass material; inducing a tensile stress in excess of the tensile strength of the glass in an area adjacent to the notch; and separating the preform length from the remaining length at the notch.

This application relates generally to an optical fiber for the delivery of infrared light where the polarization state of the light entering the fiber is preserved upon exiting the fiber and the related methods for making thereof. The optical fiber has a wavelength between about 0.9 ?m and 15 ?m, comprises at least one infrared-transmitting glass, and has a polarization-maintaining (PM) transverse cross-sectional structure. The infrared-transmitting, polarization-maintaining (IR-PM) optical fiber has a birefringence greater than 10.sup.?5 and has applications in dual-use technologies including laser power delivery, sensing and imaging.

A method of making an optical fibre preform comprising providing a hollow outer tube of glass, providing a hollow primary capillary tube of glass with an outer diameter smaller than an inner diameter of the outer tube, positioning the primary capillary tube inside the outer tube such that an outer surface of the primary capillary tube lies against an inner surface of the outer tube along a contact line parallel to the longitudinal axes of the primary capillary tube and the outer tube, and bonding the primary capillary tube into its position inside the outer tube by directing a laser beam onto a surface of the outer tube or the primary capillary at one or more locations aligned with the contact line.

Provided is an optical fiber containing an alkali metal element or the like having a smaller diffusion coefficient than K and having a low Rayleigh scattering loss. An optical fiber is composed of silica glass and includes a core and a cladding arranged to surround the core which has a lower refractive index than the core. The core includes a first core including a central axis and a second core arranged to surround the first core. The average concentration of an alkali metal element or alkaline-earth metal element in the first core is 10 mol ppm or less. The average concentration of chlorine in the first core is 2000 mol ppm or more. The average concentration of an alkali metal element or alkaline-earth metal element in the second core is 10 mol ppm or more. The average concentration of chlorine in the second core is 10 to 600 mol ppm.

A glass cane is manufactured by filling a glass tube with a combination of glass structures forming a cross-sectional pattern within the glass tube, to form a preform. The preform is attached to a draw assembly, such as a draw tower. The draw assembly is operated o draw the preform to a reduced-diameter glass cane by passing the preform through a furnace of the draw assembly while pulling the preform or the reduced-diameter glass cane and rotating the preform or the reduced-diameter glass cane.