Splicing element for connection of individual light waveguides

A splicing element particularly useful for interconnecting the ends of a pair of light waveguides, such as optical fibers, in light transmitting relationship characterized by a single member, which is either molded or formed from a sheet of material, having a pair of thin wall portions with the inner surfaces inclined to each other at an acute angle to form a centering groove having a V-shape and extending longitudinally in the member for receiving and positioning the ends of the light waveguides. In one embodiment, a base of the centering groove terminates inward from each end of the member which ends have outwardly diverging surfaces to enable engaging a covering or sheathing on the waveguide. The base of the groove may have a constant depth or be concavely-shaped with the lowest point being between the ends of the groove and at the point of contact between the ends of the fibers. In one embodiment, the centering groove terminates in second wall portions which extend parallel to each other and form an aligning groove which second wall portions terminate in diverging outwardly flared third wall portions that form an insertion aid. The fibers can be held in the centering groove either by the use of a cement, by welding or the splicing element may be deformed and crimped to mechanically hold the waveguides in the connecting position.

BACKGROUND OF THE INVENTION 
Field of the Invention 
The present invention is directed to a splicing element for forming 
undetachable end-to-end connection between individual light waveguides. 
Prior Art 
Since the aligning and centering of individual waveguides such as optical 
fibers requires precise and expensive devices due to the small diameters 
of the waveguides, the connection of individual light waveguides with one 
another is generally quite difficult to accomplish. In German 
Offenlegungsschrift 2,237,444, a process for coupling optical component 
parts is described. In this process, the component parts are fastened on 
carrier bodies or members which are subsequently aligned to one another. 
For the centering of individual light waveguide devices, it has also been 
suggested to provide precision drilled bores or holes into which the 
individual light waveguides are introduced. In U.S. Pat. No. 3,870,395, 
which corresponds to Offenlegungsschrift 2,233,916, a connecting plug 
comprising a capillary tube into which the light waveguides such as 
optical fibers are inserted is dislosed. It has also been suggested that 
the guiding of individual light waveguides can be accomplished by using 
V-shaped grooves as dislosed in Canadian Patent No. 969,744. 
SUMMARY OF THE INVENTION 
The present invention is directed to providing a connecting device or 
splicing element which distinguishes itself by having an uncomplicated and 
simple structure, which has small space requirements, and which is 
especially suited for forming splicing connection which are accomplished 
without large adjustment expenses. 
To accomplish these tasks, the present invention provides a splicing 
element for undetachably connecting one end of a light waveguide to an end 
of another light waveguide in a light transmitting relationship comprising 
a single member having a pair of thin wall portions, each portion of said 
pair having a surface inclined to the surface of the other portion of the 
pair at an acute angle to form a centering groove having a V-shape and 
extending longitudinally in said member for receiving and positioning the 
ends of the light waveguides to be connected together. Since the 
waveguides during their insertion into the centering groove will be 
self-aligned to a common axis, the special advantage of the embodiments of 
the present invention are the fact that no expensive measurement or 
centering devices are required to obtain the centering of the ends of the 
individual light waveguides which are being interconnected by the splicing 
element. To this end, it is desirable that the V-shaped centering groove 
have a base with a radius of curvature which is smaller than one-half the 
diameter of the individual light waveguides. Thus, the embodiments of the 
splicing element of the present invention may be easily manufactured by 
bending a thin wall sheet of material, for example a sheet of metal or a 
synthetic material foil, so that the resulting bend, which forms the 
centering groove, has a desired radius of curvature which is less than 
one-half of the diameter of the optical fibers forming the waveguide being 
inserted therein. 
In forming the splice, the two waveguides, such as optical fibers, 
preferably have their ends properly squared. The two waveguides are 
inserted into the splicing element at an angle to the base of the 
centering groove and then moved until the ends are in contact with each 
other. Further movement of the waveguides toward each other will cause the 
fibers to then engage the base of the groove and the fibers are 
subsequently secured therein either by use of an adhesive such as a 
cement, by welding the fibers together, or by subsequently deforming the 
splicing element to crimp the element onto the fibers to hold them in the 
connected relationship. 
In one embodiment of the invention, the base of the V-shaped groove is 
preferably formed with a concavely-arched configuration along the length 
of the groove with the lowest point being disposed between the ends of the 
groove and at the point of contact of the ends of the individual 
waveguides to be joined. In such an embodiment, the concavely-arched base 
of the groove causes the fibers to be in a curved configuration that 
results in a forced component urging the free ends of the fibers into the 
groove towards the base thereof. If an adhesive such as the glue or cement 
as a result of its surface tension tends to raise the ends of the 
individual light waveguides from the base, the forced component very 
advantageously urges the ends back toward the base of the groove. 
In another embodiment of the present invention, the ends of the V-shaped 
groove terminate inward from the ends of the single member which has end 
portions which extend from the wall portion and diverge laterally 
outwardly in a flared configuration. These end portions enable insertion 
of a waveguide such as optical fibers which have had a portion of their 
protective sheathing or covering strip therefrom and enable receiving a 
portion of the covered fiber and engaging it to reduce tensions on the 
connection between the ends of the fibers. 
In a third embodiment of the invention, the splicing element is formed of a 
sheet of material with multiple bends so that each of the thin wall 
portions forming the centering grooves have first extensions which extend 
parallel to each other and terminate in second longitudinal extensions 
which diverge outwardly so that the first extensions form an aligning 
groove adjacent the centering groove and the second extensions form an 
insertion aid to facilitate inserting the ends of the waveguides into the 
aligning groove and then subsequently into the centering groove.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The principles of the present invention are particularly useful in a 
splicing element generally indicated at 15 in FIGS. 1, 2 and 3. The 
splicing element is particularly useful for connecting light waveguides, 
which have a circular cross section, in an end-to-end light transmitting 
relationship. 
The splicing element 15 comprises a single member such as either a thin 
sheet of metal or a thin synthetic plastic foil which is folded on a bend 
line 16 to form a pair of wall portions 1, 1. The pair of wall portions 1, 
1 have inner surfaces which are inclined at an acute angle 2 to each other 
to form a longitudinally extending centering groove 3 which has a V-shape 
with the bend line 16 being the base of the groove. The base of the groove 
3 has a radius of the curvature which is less than the radius of the 
circular waveguide or less than one-half of the diameter of the 
waveguides. 
In the embodiment of splicing element 15, the bend line 16 has been cut 
adjacent both ends 18, 18 of the element 15 so that the bend line 16 
terminates at points 17, 17 (FIG. 3) which are inwardly spaced from the 
ends 18 of the element 15. Due to the cutting of the bend line to the 
points 17, each of the side wall portions 1 have end portions 4 which, as 
best illustrated in FIG. 3, are divergently bent laterally outward. These 
end portions 4 serve to receive the individual waveguides having a 
protective sheathing or covering. After the ends of the individual light 
waveguides, whose end portions have been freed or stripped of their 
protective sheathing, have been brought into contact with each other, the 
surfaces of the end portions 4 may be connected to the sheathing on the 
waveguide such as by cementing. By engaging and attaching the end portions 
4 to the sheathing or the covering, a portion of any tension placed on the 
point of connection between the two individual waveguides is applied to 
the sheathing to minimize the amount of longitudinally directed tension 
that is being placed on the connection between the waveguides. 
To use the splicing element 15, each of the waveguides such as optical 
fibers have their protective sheathing or covering stripped therefrom for 
a distance which is slightly greater than one-half of the length of the 
bend line 16. After the end of each waveguide has been properly squared, 
the ends are inserted into the groove 3 preferably at an angle to the bend 
line 16 and then moved toward each other until contact is obtained. After 
contact between the end faces of the two waveguides is obtained, continual 
relative movement of the splicing element 15 and the waveguides cause the 
waveguides to lie axially aligned in the groove 3 and due to the removal 
of the covering or sheathing, the portion in the groove 3 does not have 
any of the sheathing or cladding. Preferably, as mentioned above, the 
sheathing or covering has only been stripped from a portion adjacent the 
end so that the sheathing will be engaged by the end portions 4. 
Subsequent to insertion of the waveguides in the splicing element 15, they 
are secured in a connected relationship either by applying an adhesive or 
by crimping or deforming the splicing element into gripping engagement. If 
an adhesive is used, it can act as an immersion fluid between the two end 
faces of the fibers. 
An embodiment of the splicing element in accordance with the present 
invention is generally indicated at 20 in FIG. 4. In the splicing element 
20, the centering groove 3 extends the complete longitudinal length of the 
element and therefore is only suited for receiving an end of each 
individual light waveguide which has had the protective sheathing or 
coating removed therefrom. 
In the embodiment 20, the sheet of material in addition to the bend line 16 
has a pair of bend lines 21, 21 and a pair of bend lines 22, 22. Each of 
the bend lines 21 separates the wall portion 1 from a second wall portion 
6. Each of the bend lines 22 separates each of the second wall portions 6 
from a third wall portion 7. The pair of second wall portions 6 extend 
parallel to each other and form an aligning groove or portion 5 that 
overlies the centering groove 3. The third wall portions 7 extend or 
diverge outwardly to form an insertion aid. Thus, the element 20 has a 
cross section configuration of a V-shaped groove with a parallel extending 
second portion 6 that terminates in outwardly extending third portions 7. 
The insertion aid formed by the portion 7 assists in inserting the ends of 
the light waveguides into the aligning groove 5 which facilitates aligning 
the axes of each of the waveguides such as optical fibers to a common 
longitudinal axis as they are lowered into the centering groove 3. 
While both of the embodiments of the splicing element 15 and 20 are 
preferably since piece of sheet material such as either sheet metal or a 
thin synthetic plastic foil which is bent on the various bend lines to 
form the various wall portions, both embodiments can also be produced by 
molding a material into the splicing element with the thin wall portions. 
A third embodiment of the splicing element in accordance with the present 
invention is generally indicated at 25 in FIGS. 5 and 6. The element 25 
has a centering groove 10 which has a V-shape and extending longitudinally 
along the element. As illustrated, the groove 10 has a base 9 and 
terminates inward of the ends of the element 25 such as at points 26, 26. 
As illustrated in FIGS. 5 and 6, portions or extensions 11 extending from 
the points 26 to the end of the element 25 have diverging outward 
extending surfaces so that waveguide with protective sheathing or coating 
can be received and engaged by the surfaces of the portions 11. 
The base 9, as best illustrated in FIG. 5, between the ends 26, 26, has a 
concavely-arched configuration with the lowest point of the arch being 
substantially midway between the points 26, 26 and preferably at the point 
of contact between the ends of the two waveguides being interconnected. 
Thus, as the waveguides are inserted in the groove 10, and have their end 
faces in contact with each other, they are in a slightly curved condition 
which creates a forced component that tends to hold them closely to the 
base line 9 and opposes any lifting force caused by an adhesive used to 
secure the waveguides in the element 25. 
The embodiment 25 may be advantageously produced from a synthetic material 
by utilizing injecting molding process. In addition, the device 25 may be 
molded out of other materials, for example metal as well as glass or 
ceramic materials. As pointed out hereinabove, the individual light 
waveguides are preferably secured within the element 25 by a suitable 
adhesive such as cement which will simultaneously serve as an immersion 
substance. 
If the element 25 is formed of a deformable material, a mechanical gripping 
of the ends of the individual light waveguides while in the centering 
groove may be accomplished by squeezing the thin walls forming the groove 
10 into tight gripping engagement on the inserted aligned fibers. 
Although various minor modifications might be suggested by those versed in 
the art, it should be understood that we wish to employ within the scope 
of the patent warranted hereon, all such modifications as reasonably and 
properly come within the scope of our contribution to the art.