Optical waveguides – Optical fiber waveguide with cladding
Patent
1993-02-12
1995-09-19
Lee, John D.
Optical waveguides
Optical fiber waveguide with cladding
385 39, 385136, G02B 616
Patent
active
054523931
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a family of new fiber routing components. The invention also relates to providing bends in optical fibers with no appreciable loss of optical power and without fracturing the fiber or affecting its longevity. The invention also relates to packaging electro-optical and fiberoptic components in greatly reduced package volumes. The invention further relates to twisting optical fibers without incurring breakage or loss of optical power.
BACKGROUND OF THE INVENTION
Panel connections of glass fiberoptic cables are often cumbersome and inefficient. An example is a patch panel for a communications network in which a great number of side-by-side fiber cables are connected endwise to the face of the panel. The cables extend outwardly in a group and bend only gradually from the connection to avoid mechanical failure of the glass fibers and signal loss. Routing of fiber cables in restricted spaces, as in an automobiles, presents similar problems.
Fiberoptic device packages are often large and cumbersome due to large radius bends required in glass fibers within the packages.
SUMMARY OF THE INVENTION
According to one aspect of the invention we have realized that small routing devices that reorient the fiber path from one axis to another over a short distance are both practical to realize and can contribute significantly to routing of optical fibers.
In achieving many such configurations the bent fiber portion is provided in a special treated state that reduces likelihood of mechanical failure over time. Depending upon the application and the particular treatment employed, bend loss of say 10 percent may be tolerated or bend loss can be reduced to a minimal amount. Treatment includes reduction in diameter and/or annealing heat treatment, and/or provision, effectively, of air cladding in the region of the bend.
According to one aspect of the invention a routing device is provided for changing the direction of a fiberoptic path from a first axis to a second axis. The routing device comprises a short length of low-loss optical fiber having first and second directed portions aligned respectively with the first and second axes and a mid-fiber portion integral with and extending through an arc of radius of the order of two centimeters or less between the first and second directed fiber portions. The mid-portion of fiber is in a treated state that reduces likelihood of mechanical failure over time without introducing substantial optical loss, e.g., the diameter is reduced relative to the main portion of the fiber, or the fiber is bent and annealed to reduce bending stresses. This treated section of fiber is typically housed in an outer member that fixes the first and second directed fiber portions relative to one another in a predetermined, desired angular relationship. The outer member also serves to protect the first and second directed portions and the mid-portion from the environment.
According to a more particular aspect of the invention, a selected length of optical fiber, in a region where the exterior of the fiber is exposed to an external environment having an index of refraction substantially lower than that of the solid clad layer, is reduced in diameter in a manner to cause the fiber to conduct light by internal reflection attributable at least in part to the difference in index of refraction at the interface between the exterior of the fiber and the external environment. By this means light energy can be transmitted through the region with substantially lower bend-loss than a similarly bent section of the main length of the fiber, and it is in this region that the fiber is oriented differently, e.g. bent and/or twisted relative to an adjacent portion of the fiber, without causing substantial light loss attributable to the orientation. In both single mode and multimode fibers, the optical mechanism which allows a very significant reduction in bend radius relates to the change of waveguide structure accompanying diameter reduction. Optical fibers typically have a
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Fitzgerald Paul W.
Gillham Frederick J.
Stowe David W.
Aster Corporation
Lee John D.
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