Optical waveguides – Accessories
Reexamination Certificate
1999-07-30
2001-06-19
Lee, John D. (Department: 2874)
Optical waveguides
Accessories
C065S433000
Reexamination Certificate
active
06249631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for preparing a solid core fiber optic cable for a splice by applying a radial compressive strain to a waste end of the solid core fiber optic cable.
2. Description of Prior Art
Solid core fiber optic cable is commonly used to create a light source where light fixtures would be otherwise difficult to locate; to replace systems of multiple light bulbs; to reduce heat output at a light source; and/or many other practical and aesthetic applications. For instance, in the automotive industry, a single centralized light engine supplying light to a series of fiber optic cables can replace multiple light bulbs and fixtures by providing light to headlights, marker lights, runner lights, dome lights and instrument panels. As a result of the proliferation of fiber optic cable in such widespread applications, repairs, replacements and retrofits of fiber optic cable systems are often necessary. Therefore, an effective method and apparatus for creating a splice and maintaining a coupling between two ends of fiber optic cable, with minimum light loss, is necessary.
The Specification and Claims use the terms “solid core fiber optic cable” and “fiber optic cable” interchangeably. The method and apparatus of this invention are intended for use with fiber optic cable having an outer polymeric jacket and a light-transmitting inner core. Unlike fiber optic cable used for data communication that has a cross-section the size of a strand of hair, solid core fiber optic cable typically has a core diameter of between approximately 1 and 26 mm.
One such solid core fiber optic cable is Optiflex™ fiber optic cable made by Rohm and Haas of Philadelphia, Pa. Such fiber optic cable typically comprises three different materials: an acrylic copolymer inner core; a thin Teflon™ cladding used for reflection purposes; and a polyethylene outer jacket for protection. During the processing of the core, which in one embodiment is 7.1 mm in diameter, the cladding is extruded and joined with the inner core while in a molten state, thus providing a smooth interface between the inner core and the cladding. This smooth interface is beneficial to the transmission of light through the fiber optic cable for consistent reflection.
Fiber optic cable is currently cut or spliced using a hand tool having a spring biased Teflon™ coated razor blade. A guillotine-like action cuts through the outer jacket, the cladding and the inner core of the fiber optic cable resulting, at least initially, in a generally smooth inner core profile ready for a splice.
However, after the fiber optic cable is cut, for instance to prepare a splice between two lengths of fiber optic cable, the cladding and the inner core tend to delaminate and thus separate. This separation allows the inner core to relieve the residual tensile stresses imparted during the polymer curing process which results in a retracted, typically concave, inner core surface profile relative to the cladding and the outer jacket.
When two lengths of fiber optic cable having a retracted inner core surface profile are joined or spliced together, the result is an air gap between the opposing inner cores within the outer jackets. Such an air gap greatly reduces the effective light transmission through a spliced fiber optic cable. Mechanical fasteners exist that will hold and maintain a splice between two lengths of fiber optic cable, however, an effective method and apparatus to prepare a fiber optic cable for a splice is needed.
SUMMARY OF THE INVENTION
The method and apparatus according to this invention preferably result in a splice end of fiber optic cable having an inner core configured in a convex bulb. This convex bulb configuration results in intimate contact between opposing inner cores of adjacent splice ends of fiber optic cable. The intimate contact between opposing convex bulbs in adjacent splice ends results in greatly reduced light losses in a spliced fiber optic cable over the prior art.
A method for preparing fiber optic cable for a splice preferably comprises applying a radial compressive strain to a waste end of the fiber optic cable and cutting the fiber optic cable adjacent to the applied radial compressive strain. The resultant splice end of the fiber optic cable comprises a convex bulb facilitating intimate contact with an opposing convex bulb.
Preferably, the radial compressive strain is applied uniformly around a circumference of the fiber optic cable thus resulting in a uniformly shaped convex bulb having a symmetrical surface profile. When the splice ends of two fiber optic cables are joined together, the symmetrical surface profiles of the corresponding convex bulbs create uniform intimate contact between the corresponding convex bulbs and thus minimizes light loss through the resulting splice. The splice ends of each of two fiber optic cables are typically joined together using a mechanical fitting.
According to a preferred embodiment of the invention, the radial compressive strain is applied to the fiber optic cable using a collet. The collet preferably comprises a sleeve having a tapered or stepped inner surface and a corresponding collet sleeve for adjusting the applied radial compressive strain.
The device according to this invention is preferably adaptable to any cutting means known to those having ordinary skill in the art. The cutting means is preferably positioned directly adjacent to the applied radial compressive strain and in a position to cut perpendicularly with respect to a longitudinal axis of the fiber optic cable.
It is one object of this invention to provide a method for splicing fiber optic cable that avoids excess light loss in the resultant splice.
It is another object of this invention to provide a method for splicing fiber optic cable to promote intimate contact and thus avoid an air gap between two spliced ends of fiber optic cable.
It is another object of this invention to provide a device that results in a fiber optic cable having a splice end with a convex bulb.
It is still another object of this invention to provide a device for use in connection with existing fiber optic cable cutting tools.
It is yet another object of this invention to provide a device for preparing a splice end of a fiber optic cable that is capable of intimate contact and adhesion with an opposing splice end.
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Casey Christopher
Colwell Jason
LeVey Kenneth
Madhyastha Maitreya
Breh Donald J.
Connelly-Cushwa Michelle R.
Croll Mark W.
Illinois Tool Works Inc.
Lee John D.
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