Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1999-08-24
2001-09-25
Font, Frank G. (Department: 2877)
Optical waveguides
With optical coupler
Input/output coupler
C385S042000, C385S043000, C385S016000
Reexamination Certificate
active
06295398
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
N/A
BACKGROUND OF THE INVENTION
In certain fiber optical components and applications using small packages, it is necessary to form a miniature bend in the bare fiber to change the direction of the fiber. To avoid light loss and maintain a useful longevity in an unprocessed bent fiber, the turn typically requires a bend radius of 2 cm or more. This radius may be substantially reduced to as little as 50&mgr; using a miniature bend. To form a miniature bend, the diameter along a length of bare fiber is reduced to as little as 1 &mgr; or less, by, for example, drawing, etching, or a combination thereof. In the reduced diameter region, the fiber conducts light by internal reflection at least partially due to the difference in index of refraction at the interface between the fiber and the surrounding environment, generally air. Thus, in this region, the fiber may be bent with no substantial light loss from the bend. See U.S. Pat. Nos. 5,138,676 and 5,452,383, the disclosures of which are incorporated by reference herein.
In such miniature bends, it is desirable in some applications to keep the radius of curvature in the bend region to a value of 0.5 mm or larger to avoid loss of optical energy in the bend region. Because the bend is symmetrical, the bend region of the fiber protrudes above the plane of the fiber, as can be seen in FIG.
1
. If the fiber lies close to a surface, the bend may potentially contact the surface. Generally, contact of the fiber in the bend region with any surface also causes light loss, which is undesirable. Therefore, the input fibers to a symmetric miniature bend must be spaced a sufficient distance from such a surface to prevent contact between the surface and the bare fiber of the bend. Alternatively, the surface must be formed with a deviation to avoid contact with the bend.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a fiber optic device for changing direction along a fiber optic path using an asymmetrical miniature bend. The device comprises an optical fiber having an entering fiber portion and an exiting fiber portion. A buffer covers at least a portion of the entering fiber portion and the exiting fiber portion. A bend is formed in an intermediate portion comprising a bared optical fiber portion between the entering fiber portion and the exiting fiber portion of the optical fiber. The intermediate portion includes a region having a diameter reduced to less than a diameter of a fiber portion unreduced in diameter and is capable of transmitting light with substantially less light loss due to bending than the unreduced fiber portion. The bend provides a change of direction between the entering fiber portion and the exiting fiber portion and has an asymmetrical configuration formed by an outwardly convex portion and an outwardly concave portion. To provide a reversal of direction of the fiber optic path, the outwardly convex portion extends over an angle greater than 180°. Both the convex portion and the concave portion have a radius of curvature sufficiently large to minimize loss of optical energy in the bend. The radius of curvature is preferably at least approximately 0.5 mm. Those of skill in the art will appreciate that the minimization of loss of optical energy refers to avoiding as much light loss as practical using miniature bend technology such as described in U.S. Pat. Nos. 5,138,676 and 5,452,383.
The present invention also provides a method of forming such an asymmetrical miniature bend in optical fibers. In one embodiment, the entering and exiting fiber portions are offset along parallel axes prior to bending the intermediate portion, resulting in an asymmetrical bend. In another embodiment, the intermediate portion is heated at a location that is offset from the bending axis, also resulting in an asymmetrical bend.
The fiber optic device with an asymmetric miniature bend is particularly suitable for components in which one of the fiber portions lies close to a surface, such as a single sided splitter or coupler.
REFERENCES:
patent: 4812001 (1989-03-01), Tomita et al.
patent: 4911510 (1990-03-01), Jenkins
patent: 5138676 (1992-08-01), Stowe et al.
patent: 5222165 (1993-06-01), Bohlinger
patent: 5353363 (1994-10-01), Keck et al.
patent: 5452393 (1995-09-01), Stowe et al.
patent: 5517590 (1996-05-01), Auborn et al.
patent: 5553179 (1996-09-01), Cryan et al.
patent: 5633494 (1997-05-01), Danisch
Gillham Frederick J.
Ouellette Thomas R.
Stowe David W.
Font Frank G.
Nguyen Sang H.
Thomas & Betts International Inc.
Weingarten, Schurgin Gagnebin & Hayes LLP
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