Fused array preform fabrication of holey optical fibers

Abstract

This invention pertains to a holey fiber and to a fabrication method for making the fiber. The holey fiber can transmit light by total internal reflection or by Bragg diffraction, can be single mode or multimode and can have solid core or a hollow core. The holey fiber has outside diameter typically of 20 microns to 5 mm, a hollow core of a diameter typically of 0.2 micron to 150 microns and longitudinal channels therethrough of a diameter typically of 0.1 micron to 150 microns. The channels are disposed in a desired arrangement with center-to-center distance variation of less than about 2% along the length of the fiber and the cross-section thereof is round that varies less than about 2%. The method includes the steps of stacking structures of at least two different materials of lower and higher softening points in a desired arrangement to form a bundle containing interstices between the structures; heating the bundle to a fusion temperature which is below the softening point of the higher softening point material to form a fused element whereby the lower softening point material softens and flows around the higher softening point material and closes the interstices; removing the structures of the higher softening point material from the fused element to form a preform, thus forming openings in the fused element; and drawing the preform at a draw temperature which is below the softening point of the lower softening point material to form the holey fiber.

Description

BACKGROUND [0001] 1. Field of the Invention [0002] This invention pertains to fabrication of optical holey fibers and to the optical holey fibers made thereby. [0003] 2. Description of Related Prior Art [0004] There is significant current interest in the novel optical properties of holey fibers. Holey fibers are typically glass fibers that are fabricated with a network of open channels or holes that run the length of the fiber. Theoretical and computational studies of the properties of holey fibers indicate that these fibers may be superior in many ways to conventional step index or gradient index solid glass fibers. All conventional optical fibers confine light by total internal reflection whereby light is confined within a core that has a higher index of refraction than the surrounding cladding. Holey fibers can confine light using either of two mechanisms: conventional total internal reflection or Bragg diffraction, which is also known as photonic band gap confinement. If light i...

AI Technical Summary

Benefits of technology

[0015] Another object of this invention is the fabrication of high quality holey fibers characterized by transmission of light therethrough with essentially zero optical loss, virtually no nonlinear effects and significantly reduced light scattering.

Problems solved by technology

This periodicity allows light of certain wavelengths to be conveyed through the fiber but will not allow light of other wavelengths, in the stop band, through.

These wavelengths will scatter and be lost.

It is not possible to describe an optimum design of photonic crystal fibers in general since different fibers are optimized for each of the above mentioned properties.

This is due primarily to the inability to fabricate holey fibers uniformly and reproducibly.

Although holey fibers are of great interest and the physics is quite well understood, experimental studies are hampered due to an inability to fabricate high quality fibers.

The greatest challenge facing designers of holey fibers is fabrication.

High quality, uniform holey fibers are extremely difficult to make.

In practice, however, it is found that it is virtually impossible to sufficiently heat the bundle to successfully close the interstitial spaces without causing significant distortion in the circular shape of the tubes and the relative orientation of the tubes.

Non-uniformities in band gap fibers are primarily responsible for the optical losses.

There is no possibility of obtaining long lengths of holey fibers which have channel aspect ratio that is essentially infinite, following the acid etching techniques used for nanochannel glass.

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