Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
0~352132 R. L. McCartney/E. A.
La ndgree n 12 -4
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B~C KG RO i ND OF T HE I NVE NTI ON
The present invention relates generally to fiber optic connectors,and,
more particularly, to a novel fiber optic cable for use with a fiber optic con-
nector.
InourU. S. PatentNo. 3,910,678, issuedOctober7, 1975, thereis
disclosed an optical fiber connector for coupling a pair of fiber optic cables
containing fewer number of larger fibers than are normally incorporated in
standard fiber optic cables. In accordance with the invention disclosed in
our prior patent, the connector contains a star coupler employing a generally
axially elongated spindte tapered at both extremities to form a pointed end at
each extremity. These points lie substantially on the axial centerline of the
spindle~ An annular sleeve of transparent elastomer optical interface material
surroùnds the center portion of the spindle and both are contained in a coaxlal
sleeve naving an inside diameter equal to the outside diameter of the elastomer
; element. When the connector members holding the two optical fiber cables to
be connected are mated, the tapered ends of the spindle feed into the fiber bun-dles essentially on the axial centerline and force the fibers outward and aroundthe spindle body to a point of abutment against the annular elastomer element
from both sides. Thus, the fibers in the two bundles are arranged in complemen-
tary annular arrays so that the mating end faces of the flbers may be coupled
through the intermediate elastomer element, thereby- permitting light coupling
between the two optical fiber cables with minimum light transmlssion losses.
As will be seen from the following description, the present invention is
directed to an entirely different problem than the coupling of a pair of fiber optic
5 cables, but the invention embodies some features which have a slmilarlty to
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R. L. McCartney-E. A. Landgrean
12-4
those disclosed in our Patent No. 3,910,678. More specifically, the present
invention is directed to the problem of the use of an edge emitting LED for
: coupling light into a fiber optic cable. When using an edge emitting light
source, a reflecting surface is required to project the light onto the end
face of the cable. The projected beam of light has the form of a hollow cone.
This hollow cone, when intercepted by the fiber bundle of the cable, creates
an annulus of light on the receiving surface of the bundle. If the receiving
bundle surface contains enough fibers to fully fill the outside diameter of
the annulus, then no special adjustments need be made to receive the light
beam. However, if the fiber bundle diameter is not large enough to fully
intercept the light annulus due to insufficient fibers or due to bundle -;
division for use in optical bus systems, some means must be provided to in-
crease the fiber bundle diameter so that the fiber bundle will receive all
the light emitted from the edge emitting LED. The present invention achieves
a solution to this problem.
SUMMARY OF THE INVENTION
.
According to a principal aspect of the present invention, there is
provided a fiber optic cable for use in a fiber optic connector. The cable
comprises a fiber optic bundle including a plurality of light transmitting
fibers terminating in a planar end surface. A hollow body surrounds the bundle
having a forward end co-planar with said end surface. A rearwardly tapered
member centrally located with respect to the center axis of the body positions
~ the fibers in an annular array therein.
; The cable may be used in a fiber optic connector employing a light
source which produces a light annulus. The light source and fiber optic
cable of the present invention may be mounted in respective conneFtor members
such that when the connector members are inter-engaged, the annular array of
fibers in the cable will be adjacent to and concentrically aligned with the
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R. L. McCartney-E. A. Landgreen
12-4
light annulus produced by the light source. Thus, by the present inven-
tion, efficient light coupling to a light annulus can be achieved by the
use of a fiber optic cable containing fewer fibers than previously required.
BRIEF DESCRIPTION OF THE DRAWINGS -
:
Fig. 1 is a front elevational view of a receptacle connector
member containing a pair of fiber optic cables, one of which embodies the
- novel features of the present invention; ~ ;
~` Fig. 2 is a vertical sectional view taken along 2-2 of Fig. l;
Fig. 3 is a horizontal sectional view taken through a plug
connector member, which is matable with the receptacle connector member
of Figs. 1 and 2, and contains a light source which produces a light
annulus;
Fig. 4 is a longitudinal sectional view through the mating end of
the fiber optic cable employed in the receptacle connector member of Figs. 1
and 2; and
Fig. 5 is a front end view of the cable illustrated in Fig. 4.
,
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings in detail, there is illustrated
in Figs. 1 and 2 a receptacle connector member, generally designated 10,
- 20 which is matable with a plug connector member, generally designated 12,
illustrated in Fig. 3. The plus connector member comprises a metal
shell 14 containing a metal insert 16, which may be formed of aluminum,
for example, so as to function as a heat sink. ~;
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R. L. McCartney-E. A. Landgreen
12-4
A light source 18 is mounted within a cavity 20 in the in- -
- sert 16. The light source may be an edge emitting LED
which produces an annulus of light. An insulator 22 is
mounted in the inser~ 16. A light receiving detector 24
is mounted in a cavity 26 în the insulator 22. An insulator
disc 28 is mounted behind the insert 16.
The mating receptacle connector member 10 comprises a
shell 30 containing an insulator 32 formed with a pair of
parallel, axially extending cavities 34, only one being
visible in Fig. 2. Fiber optic cables 36 and 38 are mounted
in the cavities 34. Each cable is terminated by a termination - -
pin, generally designated 40, only one being visible in Fig. 2.
The termination pins on the cables 36 and 38 are arranged -
in the respective cavities 34 in the receptacle connector ;
member 10 so that when such member is mated with the plug
connector member 12, the termination pins will be aligned
with and come into abutmen$ with the light source 18 and
detector 24, respectively. Each termination pin 40 is
mounted in its respective cavity 34 by means of a spring
retention clip 42. The clip has a pair of forwardly and
inwardly extending spring fingers 44 engaging the rear-
wardly facing shoulder 46 on the termination pin 40, ,
limiting rearward movement of the pin in the insert 32.
The pin is also formed with an annular groove 48 which
contains an elastomeric O-ring 50. The O-ring cooperates
with an inclined rearwardly facing surface 52 on the
insert 32 to provide axial tolerance relief for the termi-
; nation pin.
A rubber grommet 54 is mounted over the
rear of the insert 32 behind the
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8~i2~)2 R. L. McCar~ney/E. A.
Land~reen 12 4
shell 30. The grommet has a pair of passages 56, only one being visible ln
Fig. 2, which receive the fiber optic cables 36 and 38. ~n elas~omeric inter~
facial seal 58 is mounted on the front of the insert 32 surrounding each of
the termination pins 40. A peripheral seal 60 is provided on the inner surface
62 of the shell 30. The seals 58 and 60 assure that no dust or other contam
inants enter the connector members 10 and 12 after they are coupled together.
The termination pin 40 of the fiber optic cable 38 terminates a fiber
optic bundle in which the fibers are arranged in a random array in a conventlonal
manner, as seen in Fig. 1. Such bundle is coupled to the light detector 24 when
the connector members 10 and 12 are interengaged.
In accordance with the present invention, the individuat fibers of the
fiber optic bundle of cable 36 are arranged in an annular array which is comple-mentary to the light annulus produced by the edge emitting LED 18.
Referring to Figs. 4 and 5 of the drawings for a detailed showing of the
cable 36, it is noted that the light transmitting fibers 64 of the~fiber optic
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bundle 66 of cable 36 are enclosed by a jacket 68 except for the forward ends
~f the fibers from which the jacket has been removed. The termination pin 40
is in the form of an elongated hollow metal body having an axially extending
passage 70 therethrough. The rear portion of the passage is enlarged, as indi-
cated at 72, and receives the forward end of the jacket 68 of the fiber optic
- bundle 66.
An elongated fiber spreader 74, preferably formed of plastic,
is mounted in the forward end of the termination pin 40. The spreader has a
forward cylindrical portion ?6 and a rear portion 78 which tapers rearwardly to
a point 80. Preferably the rear portion 78 has a conical configuratLon. The
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:1~135202 R. 1,. McCartney/E. A.
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fiber spreader 74 is concentrically mounted within thc passage 70 of the
termination pin 40 and has a smaller diameter than the passage so as to
provide an annular space 82 therebetween. The space is dimensioned to
slidably receive the Individual fibers of the bundle 66 therein. The fibers 64
are positioned circumferentially around the spreader 74 in the annular space
82. The spreader and termination pin 40 are dimensioned so that the annular
array of fibers surrounding the spreader has the same diameter as the light
annulus produced by the light source 18. Preferably, the wall of the passage
70 er~gages the outer peripheries of the annular array of fibers 64 circumscrib-ing the spreader 74, and the outer surface of the cylindrical portion 76 of the
spreader engages the inner peripheries of the annular array of fihers so that the
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fibers are firmly held between the spreader and the termination pin. As can be
seen from Fig. 5, the fibers 64 at the forward end of the termination pin 40 are- ~ in a single annular layer. However, if a thicker light receiving annular surface
lS is desired in the termination pin 40, the fiber spreader 74 could ~e reduced in
diameter and more than one layer of fibers could be provided therearound,
The forward end of the termination pin 40 is ground and polished flat so
the plànar forward end surface 84 of the termination pin, the front face 86 of the
fibe~ spreader 74, and the mating end faces 88 of the fibers are coplanar or flush
lO with each other.
.
It will be appreciated from the foregoing that hy the present invention
there is provided an annular arTay of optical fibers which are concentric to the ;-
center axis of the termination pin. Hence, when the pin is coaxially mounted with
respect to the edge emitting light emitting diode 18 by the mating of the connector
!5 members 10 and 12, the annular array of fibers will abut the edge of the LED in
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Z R. L. McCartney/E. A.
Landgreen 12-4
concentric abutting relationship therewith so as to recelve the light annulus
produced by the diode. The number of fibers required to intercept the edge
emitting LED is less than that which would be required employing a conven-
tional fiber optic cable without the spreader 74. This results in increased
versati`lity of the fiber bundle applications to which the cable of the present
invention may be employed, such as in split cables for optical bus system
applications .
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