Method and device for releasably fixing bare glass fibers in a splicing device

A method is disclosed in which the bare glass fibers are firmly soldered into a solder bath of the splicing device and, after being scored and broken, unsoldered again. To that end, the glass fibers are placed across the solder bath, the solder is heated, and the level of the molten solder is raised above the glass fibers by pressing a slide into the solder trough. The heat supply to the solder bath is subsequently cut off. After the solder has cooled, the glass fibers are firmly fixed therein. To release the fixed glass fibers, the solder is liquefied again. The device for carrying out the method consists essentially of a slotted guide bar, which serves to hold the glass fibers apart, and the solder bath. The latter is a copper block which is thermally insulated from the splicing device and has a projection at one end for attaching a soldering iron.

TECHNICAL FIELD 
The present invention pertains to a method for releasably fixing bare glass 
fibers and to a device for carrying out the method. 
BACKGROUND ART 
DE-OS No. 33 38 493 discloses a method and a device for splicing glass 
fiber bundles. In that method, the glass fibers of the ends of two bundles 
which have previously bee prepared for splicing are each placed and fixed 
in parallel V-shaped grooves of an axially and laterally movable 
supporting plate so that the fiber ends overlap, a glass fiber of one 
bundle and a glass fiber of the other bundle alternately lying side by 
side in each supporting plate. The glass fibers are releasably fixed in 
the splicing device by means of holding-down devices which are placed 
above the glass fibers and which press them into the grooves of the 
supporting plates. Minor manufacturing variations of the diameter of the 
glass fibers are compensated for by the design of the holding-down device 
as an elastic cushion. However, the adhesion produced between the 
pressed-down cushion and the grooves when the glass fibers are fixed is 
often not strong enough to safely protect the glass fibers in the splicing 
device from axial displacements. Such protection is necessary, however, 
because the end faces of the fibers must have exact 90.degree. fractures 
before being welded. The fractures are made with a scoring tool which is 
moved within the splicing device across the glass fibers transverse to the 
axial direction. Tensile action on the glass fibers after scoring will 
result in such smooth 90.degree. fractures. 
DISCLOSURE OF INVENTION 
It is the object of the invention to provide a method and a suitable device 
for releasably fixing bare glass fibers in a splicing device, so that 
there is practically no axial displacement of the glass fibers after they 
have been fixed. In accordance with the method aspects of the invention, 
the bare glass fibers are firmly soldered into a solder bath of the 
splicing device and, after being scored and broken, unsoldered again. To 
that end, the glass fibers are placed across the solder bath, the solder 
is heated, and the level of the molten solder is raised above the glass 
fibers, preferably by pressing a slide into the solder trough. The heat 
supply to the solder bath may then be cut off. After the solder has 
cooled, the glass fibers are firmly fixed therein. To release the fixed 
glass fibers, the solder is liquefied again. 
A device for carrying out such a method may consist essentially of a 
slotted guide bar, which serves to hold the glass fibers apart, and the 
solder bath. The latter may preferably be a copper block which is 
thermally insulated from the splicing device and has a projection at one 
end for attaching a soldering iron.

BEST MODE FOR CARRYING OUT THE INVENTION 
In FIG. 1, the splicing device as a whole bears the reference numeral 1. It 
consists essentially of a base plate 2, a base 3 fixed thereto and a guide 
rail 4 which is supported by the base and which has a portion 5 for 
receiving a fiber holding plate 6 (FIG. 2). Furthermore, a 
micromanipulator 7 which is adjustable in three coordinate directions and 
which also supports a gguide rail 8 with a portion 9 for receiving an 
additional fiber holding plate 10 is located on the base plate 2 in a 
predetermined spatial relationship with the base 3. Finally, between the 
base 3 and the micromanipulator 7, a slide 11 is provided which is movable 
transverse to the longitudinal direction of the two receiving portions 5, 
9 and on which a scoring device for producing 90.degree. fractures of the 
glass fibers, and a welding device for fusing the fiber ends are located 
(not shown). 
At the front end 12 of the guide rails 4, 8, the portions 5, 9 for 
receiving the fiber holding plates 6, 10 each have a stop whose top side 
has a groove array 13 for inserting the glass fibers. Immediately behind, 
in a recess of each guide rail 4, 8, a device is located for releasably 
fixing the glass fibers. This device consists of a slotte guide bar 14 
whose slots 14' are aligned with the groove array 13, and, behind the 
slots 14', a solder bath 15 whose edge, at least in the area of the trough 
containing the solder 16, is level with the groove array 13. When the 
solder 16 is liquefied, a slide 17 can be inserted into the trough, thus 
raising the level of the solder. By withdrawing the slide 17 from the 
trough, the level of the solder is lowered. In the embodiment shown, the 
slide 17 is a simple pin with a handle portion on its outer end. 
The solder bath 15 is a block-shaped body, appropriately a block of copper 
because of its good thermal conductivity, and has, for example, a 
projection 18 at one end for attaching a soldering iron which has no tip. 
Of course, the solder bath 15 can also be heated by means of a heating 
element, such as a heating wire or a heating cartridge. The heating 
element is then located in or below the body of the solder bath 15. 
Another possibility of heating the solder is to design the block-shaped 
body of the solder bath 15 as an insulator and to heat the solder 16 by 
direct passage of current. The solder bath is thermally insulated from the 
receiving portions 5, 9 and the guide bar 14 by small glass plates or 
other suitable means. 
In FIG. 2, the ends of two glass fiber bundles 19 are each fixed to one 
fiber holding plate 6, 10 by clamping springs 20. Moreover, the spread-out 
bundle of individual fibers 21 from which the outer covering has been 
removed over part of their length are fixed to the fiber holding plate by 
means of a pivoted lever 22 and are again held, together with the bare 
glass fibers 23 stripped of their primary coating from another such bundle 
in a precision-guiding member 24 at the front end of the fiber holding 
plates 6, 10, each glass fiber 23 of one bundle lying next to the end of a 
glass fiber of the other bundle. The distance between the precisionguiding 
members 24 of both fiber holding plates is so chosen that the fiber 
holding plates 6, 10 which may, for example, be rigidly connected by a 
stirrup, can be inserted behind the solder baths 15 into the receiving 
portions 5, 9 of the splicing device 1. 
When the fiber holding plates 6, 10 are inserted into the receiving 
portions 5, 9 of the splicing device 1, the glass fibers 23 projecting 
from the precisionguiding members 24 are simultaneously placed into the 
slots 14' of the guide bars 14. The glass fibers 23 lie in the individual 
grooves of the groove arrays 13 and also flat on the edges of the solder 
baths 15. In the groove arrays I3, which are preferably made of steel, the 
glass fibers 23 can be protected from the possibility of falling out after 
the fibers have been separated, by placing magnetic rubber cushions on the 
glass fibers 23. To fix the bare glass fibers 23, which, in the 
single-mode design, have a diameter of only 0.125 mm, so as to secure them 
against axial tensile action, the solder 16 of each solder bath 55 is 
heated until the solder liquefies, a narrow holding-down device is placed 
across the glass fibers 23 at the center of the solder bath, and the level 
of the solder is raised above the glass fibers by pressing the slide 17 
into the trough. The holding-down device, which may be designed as a wire 
stirrup, ensures that the glass fibers 23 do not float on the molten 
solder 16 and that the solder can pass between the closely adjacent glass 
fibers, which have a very small clear distance of about 0.25 to 0.3 mm 
from each other, and surround them individually. The slots 14' of the 
guide bar 14 and the slots of the precision-guiding member 24 prevent the 
glass fibers 23 from sticking to each other in the molten solder 16. When 
the solder 16 is cooled until it solidifies, for example by removing the 
solder iron, the glass fibers 23 are firmly and tightly embedded in the 
solder without any requirement that they have previously been metalized, 
and they can no longer slide in the axial direction if they are exposed to 
tensile action. 
After the fiber ends have been scored and broken, the solder 16 is 
liquefied again, the level of the solder is lowered, the holding-down 
device removed from the solder bath 15 or swung back, and any remaining 
solder is removed from the glass fibers 23. The heat supply to the solder 
bath is then cut off to cool it down. The fiber ends can then be welded 
and subsequently removed from the splicing device 1. It is of course also 
possible to first weld the fiber ends together after scoring and breaking 
them, and to remove the fixed glass fibers 23 only after heating the 
solder bath I5. 
The present invention has been described above with regard to the 
structure, function and use of a presently contemplated specific 
embodiment of the invention. It should be appreciated by those skilled in 
the art that many modifications and variations are possible. Accordingly 
the exclusive rights afforded hereby should be broadly construed, limited 
only by the spirit and scope of the appended claims.