Abstract: The present invention provides a method for making a multicore large diameter optical waveguide having a cross-section of at least about 0.3 millimeters, two or more inner cores, a cladding surrounding the two or more inner cores, and one or more side holes for reducing the bulk modulus of compressibility and maintaining the anti-buckling strength of the large diameter optical waveguide. The method features the steps of: assembling a preform for drawing a multicore large diameter optical waveguide having a cross-section of at least about 0.3 millimeters, by providing an outer tube having a cross-section of at least about 0.3 millimeters and arranging two or more preform elements in relation to the outer tube; heating the preform; and drawing the large diameter optical waveguide from the heated preform. In one embodiment, the method also includes the step of arranging at least one inner tube inside the outer tube.

Abstract: Embodiments of the present invention provide various methods to fabricate optical fibers with reduced radiation sensitivity. Optical fibers are treated to one or more secondary or post-processing “conditioning” steps to create and anneal residual defects in the glass for improved radiation insensitivity.

Abstract: Apparatus and methods to fabricate a radiation hardened optical fiber from a preform are provided. Various parameters affecting the draw process are controlled to optimize the radiation resistance of the resulting fiber. An annealing zone may be provided to allow a drawn fiber exiting a primary hot zone to undergo an annealing process which may increase radiation resistance.