Splice case for fibre optic cables

A fibre-optic splice case has a support for a sealed box which contains a splice connection strip that connects together the ends of two optical fibres from two separate cables. The box is a sealed assembly having a centre of symmetry. The two cables are connectable to the box. The box has a cylindrical support with a central drum and a coaxial outer wall defines therebetween a housing in which the two cables are unreeled or reeled-up in order to deliver or take up a length of cable sufficient to allow the splice to be made. The box also has two separate straight sides each lying substantially in an extension of the other. The straight sides tubular passages are provided for fixing the ends of the two cables. The ends of these straight sides are joined with bottoms of circular overall shape, giving the box a cross-section in the form of a snail-shell.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a splice case for connecting optical 
fibres placed end to end or as a lateral cap from one of the fibres to the 
other. This case, which can be buried, including means which make 
available, as required, the overlength of fibre necessary for the splice 
to be made satisfactorily and which then, once the splice has been 
completed, allow this overlength to be taken up again, with the fibre then 
being coiled up in the case without any detrimental torsional or flexural 
stress. 
2. Description of the Prior Art 
It is known that when making a splice at the end or along the free length 
of an optical fibre belonging to a cable containing, inside an outer 
protective jacket, a plurality of such fibres, these being parallel or 
stranded together, requires, for various reasons, that a sufficient length 
of the chosen fibre be extracted from the protective jacket. 
In the first instance, since the optical fibre in question is by nature 
fragile, it is always possible, when making the splice for connection to 
another fibre, that one or other of these fibres might break, requiring 
there still be available a long enough length to start the operation 
again. 
Moreover, the essential steps for ensuring this fibre connection require 
that the lengths of fibres used are sufficient, in particular for them to 
be taken to a suitably equipped vehicle, situated near the place where the 
connection has to be made, in a chamber which is generally buried but 
which is situated most often at some distance from that place. By way of 
example, it is common practice to keep some ten meters of free fibre, or 
overlength, in reserve at each end of the cable. 
Once the splice has been completed, the problem then arises of how to keep 
this overlength in reserve, making uniform turns of fibre, as a 
figure-of-eight or in round form, with a diameter of curvature large 
enough to prevent any break or cracking when bending the fibre. This 
operation is all the more tricky to perform the greater the relative 
rigidity of the cable, especially when it has to be buried. 
The turns or rings of fibre thus obtained, in round form or as a figure 
eight, are next fixed to the wall of an inner chamber, provided beneath a 
case where the splice proper is made, the portions of the fibres thus 
housed are not, however, being protected from shocks or bending which may 
occur. 
SUMMARY OF THE INVENTION 
The present invention relates to a fibre-optic splice case which provides a 
simple and effective solution to these problems, making readily available 
an appreciable overlength of fibre for making this connection splice and 
then allowing this unused overlength to be reabsorbed, while ensuring 
effective protection of the fibre and of the cable from which it came. 
For this purpose, the case in question, has a support for a sealed box 
suitable for containing a splice connection strip connecting together the 
ends of two optical fibres from two separate cables. The box has a sealed 
assembly having a centre of symmetry, the two cables being connected up to 
this box, the cylindrical support comprising a central drum and a coaxial 
peripheral wall delimiting between them a housing in which the two cables 
are unreeled or reeled up in order to deliver or reabsorb a length 
sufficient to allow the splice to be made. The box has two separate 
straight side portions each lying substantially in the extension of the 
other, and in which straight side portions tubular passages are provided 
for fixing the ends of the two cables respectively. The ends of these 
straight side portions are joined by bottoms of circular overall shape, 
giving the box a cross-section in the form of a snail-shell. 
Advantageously, the central drum of the support includes at its upper end a 
circular collar arranged to receive the sealed box. 
Moreover, and according to another characteristic of the invention, the 
housing of the support receiving the cables includes clips for locking 
each cable in place, before they penetrate the sealed box through the 
tubular passages, imparting these cables with an appropriate curvature. 
According to another characteristic, the sealed box is made in two parts 
which are mutually affixed in a common mid-plane, in the manner of a 
bottom and a lid, and the tubular passages for the cables are 
substantially arranged in line with this mid-plane. 
According to yet another characteristic, each tubular passage 
advantageously includes heat-shrinkable sealing sleeves. The box is 
provided with means for fastening the components of the cable in the 
extension of these tubular passages. 
In accordance with another characteristic of the invention, the support 
includes an external protective cover, made of plastic or metal, having at 
least two lateral openings, preferably opposite each other, for the 
passage of the cables inserted into the housing. 
Also according to another characteristic, the peripheral wall of the 
housing includes an end edge which is inclined inwards so as to make it 
easier for the cables to be inserted into it. 
Yet other characteristics of a fibre-optic splice case, constructed in 
accordance with the invention, will appear in the following description of 
one embodiment, given by way of indication and implying no limitation, 
with reference to the appended drawings, in which:

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Shown highly diagrammatically in FIG. 1a is a conventional splice case 1, 
between two fibres coming from two cables, respectively 2 and 3. This case 
is placed in an open chamber 4, arranged in the ground 5 in which the 
cables 2 and 3 are buried. The necessary connections to be made at the 
ends of the fibres to be connected by the case I require both cables to 
have an appreciable overlength of fibre, which overlength, once the splice 
has been made, must be put into the chamber 4 by being coiled up on itself 
in order to form circular turns 6, or else having a configuration 7 in the 
form of a figure-of-eight, as illustrated in FIG. 1b which adopts the same 
arrangement as in FIG. 1a. 
In both cases, this manner of coiling up the overlength of optical fibre 
necessary for satisfactorily making the splice, to be placed in the case 
1, takes up an appreciable space and, above all, requires the circular a 
figure-of-eight turns to be fixed or hung against the walls of the chamber 
4, beneath the case 1, which does not protect them from possible shocks or 
bending which could have particularly detrimental consequences. 
FIG. 2a illustrates a splice case in accordance with the invention, 
designated in its entirety by the reference 8, this making it possible to 
group together into a single unit the zone where the ends of the fibres 
are connected to each other inside a connection box 9 carried by this case 
and also the zone where the overlengths of the cables 2 and 3, from which 
the fibres thus connected come, may be easily coiled up, allowing an 
appropriate length of these cables to be supplied for making this splice, 
as well as for these overlengths being put back into the case once this 
splice has been made, then ensuring that the cables are effectively 
protected. In the chamber 4, the case 8 may advantageously be covered by a 
protective cover 10, the details of which will be explained later. 
FIG. 2b diagrammatically illustrates the manner in which the case 8 makes 
it possible, simply by unreeling the cables outside the chamber 4, to 
provide the overlengths necessary for making the splice proper, which 
splice, once it has been placed in the connection box 9 and the latter 
fitted into the case 8, is completely protected, reeling the case in the 
opposite direction, in order to bring it back to the chamber 4, allowing 
the previously supplied overlengths to be taken up again, and placing the 
corresponding turns inside the housing in the case. 
FIG. 3 illustrates, on a larger scale, the structure of the case 8 and of 
the connection box 9 for the cables 2 and 3 from which the splice to be 
fitted into this box is made. 
As may be seen in these figures, the case 8, having the overall shape of a 
cylindrical support, consists especially of a central drum 11, extended at 
its upper end by a support plate 12 which itself terminates on its 
external periphery in a rim 13, perpendicular to the plane of the support 
plate. 
The support plate 12 and the rim 13 thus form an open cavity 14 in which 
the box 9 may be housed, which box is essentially formed by a hollow 
bottom 15 and an upper lid 16, which join together in a sealed manner in a 
mid-plane of the box. A circular boss 17, the external diameter of which 
corresponds substantially to the internal diameter of the drum 11, is 
provided beneath the bottom 15, in its central part, in such a way that 
the box can be suitably held in place in the cavity without preventing it 
from possible movement with respect to the axis of the drum. 
The cables 2 and 3 are connected up to the box 9, substantially in its 
mid-plane, by tubular passages such as 18 and 19, the constructional 
details of which will appear more clearly in FIGS. 4 and 6, these passages 
being arranged so as to immobilize the ends of the cables with respect to 
the box 9 and to seal the zone where they penetrate this box, especially 
by means of heat-shrinkable sleeves (not shown), while at the same time 
allowing, beyond these passages inside the box, break-out of the various 
optical fibres, such as 20 and 21, coming from the two cables 
respectively. 
All these fibres 20 and 21 belonging to one or other of the cables 2 and 3, 
or else only some of these fibres, are provided for being connected 
together in pairs, each time using an appropriate connection strip 22, the 
details of which are of little import to the invention and are therefore 
not described here. 
Advantageously, the fibres 20 and 21 and their connection strips 22 are 
themselves housed in a holder 23, suitable for being fitted and locked in 
place inside the sealed box 9, between its bottom 15 and its lid 16, these 
being joined together around their respective peripheries by connection 
screws 24. 
In accordance with the invention and as shown in more detail in FIG. 4, the 
box 9 is formed so as to give it the shape of a snail-shell, having a 
centre of symmetry and including for this purpose two straight side 
portions 24 and 25, each lying substantially in the extension of the 
other, these straight portions being joined together by two bottoms of 
circular overall shape 26 and 27, these being symmetrical and opposite 
each other, the bottom 26 being connected to those ends of the straight 
portions 24 and 25 which are located on the left-hand side in the drawing, 
while the bottom 27 is joined to those ends of these same portions which 
are located on the right-hand side. 
The sealed passages 18 and 19, where the cables 2 and 3 end, are provided, 
in the example in question, in the straight portion 24, the equivalent 
passages of portion 25 being in this case blocked off by plugs 28. A 
symmetrical arrangement could, of course, be envisaged with the passages 
18 and 19 in the portion 25 and the plugs 28 in the portion 24. 
Beyond these passages, the cable jackets are cut so as to allow the 
break-out of the fibres 20 and 21 contained in these cables, these jackets 
being immobilized by locking clips 29. Also shown diagrammatically in FIG. 
4, on the output side of the cables 2 and 3, are axial reinforcements 30, 
generally made of metal, equipping these cables, these reinforcements 
being locked in place against the bottom 15 of the box 9 by fastening 
means such as 31 (see also FIG. 6). 
Still in FIG. 4, it may be seen in more detail how the holder 23 may be 
formed, in which the connection strips 22 joining together the ends of the 
fibres 20 and 21 respectively are immobilized, these fibres being wound 
around a central core 32 provided in this holder and advantageously being 
housed beneath peripheral retaining tabs 33. 
The holder 23, once it has been housed inside the sealed box 9, is held in 
place against or beneath the edges of the straight portions 24 and 25 (see 
FIG. 6 again) facing the bottoms 26 and 27 and leaving free with respect 
to the latter a space sufficient for the swelling of the fibres between 
the passages 18 and 19 and the holder. 
FIG. 5 illustrates, seen in partial cross-section, the case 8 into which 
the sealed box 9 is fitted by its boss 17, this box itself containing the 
holder 23 (not shown in this figure). 
The corresponding sectional view makes it possible to see more clearly the 
structure of the case 8 which includes, around the central drum 11, a 
coaxial peripheral wall 34 having, at its upper end, an edge 35 which is 
inclined towards the inside of the housing 36 delimited between the drum 
and the wall and leaving, beneath the support plate 12, a circular opening 
37 for inserting or extracting the cables 2 and 3 depending on whether the 
case is reeled up or unreeled along the ground, as illustrated in FIG. 2b 
seen above. 
The support plate 12 moreover includes an opening 38 for the passage of the 
ends of the cables, these cables being held in place with respect to the 
box 9 by locking and guiding clips 39. 
Next, the whole assembly is covered with the protective cover 10, this 
being, of course, removable in order to allow access to the box 9 and, 
after opening the latter, to the holder 23, this protective cover being 
made of an appropriate plastic or metallic material. Near its lower end, 
the cover includes at least two through-openings 40 for the cables 2 and 
3, only one of these openings appearing in the drawing. 
A fibre-optic splice case of simple design is thus produced, which allows 
both the splice proper to be made between the fibres to be joined, before 
their connections are fixed to a holder which is itself housed and 
immobilized in a sealed box, and also allows there to be available, as 
required, any overlength of cable possibly necessary for modifying or 
redoing any of the splices thus made. The structure of the case then 
allows this overlength to be reliably and easily taken up again, without 
imposing any stress on the fibres themselves, as on the cables, which are 
reeled up naturally, without bending or twisting, into the case in the 
housing that it has beneath the cavity for receiving the sealed box. 
The case has a relatively small overall size and allows the cables to be 
housed optimally, the protective cover giving effective protection of the 
case from ground pressures when this case is buried, in respect of 
ordinary communication cables. 
Of course, it goes without saying that the invention is not limited to the 
embodiment more especially described with reference to the appended 
drawings; on the contrary it encompasses all variations thereof.