# Patent

## Title
Apparatus and method for absorbing laser energy that fails to couple into the core of a laser fiber, and for absorbing the energy that has been transmitted to the cladding of the laser

## Abstract

A fiber optic connector for coupling focused radiant energy from a laser to a fiber optic conductor includes a quartz alignment ferrule that is fused mechanically and optically to the fiber's proximal end, either by an index matching first adhesive or by heat fusing the cladding to the ferrule without removing the cladding from the end of the fiber. The fiber and ferrule are attached to the fiber's proximal termination connector by a second adhesive with a high refractive index which absorbs errant radiant energy that has propagated in the fiber's cladding. The absorbed errant energy is dissipated by the connector assembly as it is converted to heat.

## Background
This application claims the benefit of U.S. provisional patent application Ser. No. 61/788,238, filed Mar. 15, 2013, and incorporated herein by reference.


BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fiber optic connector and connector system or arrangement for coupling focused radiant energy from a laser to a fiber optic conductor.
2. Description of Related Art
The invention provides an improvement to the connector arrangements disclosed in the Inventor's U.S. Pat. Nos. 5,179,610 and 7,090,411, incorporated by reference herein. In the connectors disclosed in the cited patents, radiation that fails to couple with a small core fiber and radiation which couples with higher order propagation modes is absorbed by the connector or surrounding structures. The improvement permits the use of a fiber with full cladding, thereby making the fiber termination more rugged and simplifying manufacturability.
SUMMARY OF THE INVENTION
A fiber optic connector for coupling focused radiant energy from a laser to a fiber optic conductor includes a quartz alignment ferrule that is fused mechanically and optically to the fiber's proximal end, either by an index matching first adhesive or by heat fusing the cladding to the ferrule without removing the cladding from the end of the fiber. The fiber and ferrule are attached to the fiber's proximal termination connector by an adhesive with a high refractive index which absorbs errant radiant energy that has propagated in the fiber's cladding. The absorbed errant energy is dissipated by the connector assembly as it is converted to heat.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic depiction showing the effects of thermal lensing on coupling of a focused laser beam to the core and cladding of the fiber.
FIG. 2 is a cross-sectional side view of proximal terminal connector constructed in accordance with the principles of a preferred embodiment of the invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in FIG. 1, a laser beam 19 is focused into the fiber core 23 by the laser's focusing lens 21 with a half angle of acceptance (θ1). However, due to thermal lensing, an expanded beam 20 is focused into both the fiber core 23 and cladding 22 with a half angle of acceptance (θ2). The present invention uses refractive index matching adhesives to provide a path for dissipation of the energy in the cladding to a heat sink in the form of a ferrule and/or structures in contact with the ferrule.
As shown in FIG. 2, the termination arrangement of a preferred embodiment of the invention is included in a proximal termination connector 10 and threaded nut 8, although the illustrated connector and nut configuration should not be taken as limiting since the invention can be applied to a variety of termination connectors, including ones without nuts.
The fiber inside the connector consists of a fiber core 1, cladding 2, coating 7, and buffer 6. The fiber is fused to the quartz ferrule 3 by a refractive index matching first adhesive 4 or by heat fusing the cladding 2 to the ferrule 3 without removing the cladding from the end of the fiber, and the fiber and ferrule are secured in the connector by a high refractive index second adhesive 5, thereby providing a dissipation path for energy that has coupled to the cladding 2 rather than to the core 1 of the fiber.
Having thus described a preferred embodiment of the invention in connection with the accompanying drawings, it will be appreciated that the invention is not to be limited to the specific embodiments or variations disclosed.

## Claims

1. A fiber optic connector arrangement for coupling focused radiant energy from a laser to a fiber optic conductor, the fiber optic conductor including a core and cladding, comprising:
an alignment ferrule; and
an index matching first adhesive for mechanically and optically fusing the alignment ferrule to a proximal end of the fiber optic conductor,
wherein the fiber optic conductor and ferrule are attached to a connector by a second adhesive with a high refractive index so as to absorb errant radiant energy that has propagated in the fiber optic conductor's cladding.

2. A fiber optic connector arrangement as claimed in claim 1, wherein the ferrule is a quartz alignment ferrule.

3. A fiber optic connector arrangement as claimed in claim 1, wherein the connector is a proximal termination connector with a coupling nut.

4. A fiber optic connector arrangement for coupling focused radiant energy from a laser to a fiber optic conductor, the fiber optic conductor including a core and cladding, comprising:
an alignment ferrule, wherein the cladding of the fiber optic conductor is heat fused to the ferrule without removing the cladding from the end of the fiber optic conductor; and
an adhesive for attaching the fiber optic conductor and ferrule to a connector, wherein the adhesive has a high refractive index so as to absorb errant radiant energy that has propagated in the fiber optic conductor's cladding.

5. A fiber optic connector arrangement as claimed in claim 4, wherein the ferrule is a quartz alignment ferrule.

6. A fiber optic connector arrangement as claimed in claim 4, wherein the connector is a proximal termination connector with a coupling nut.