Fixing, earthing and sealing device for optical cables

Device for fixing, earthing end sealing the end of an optical cable, including at least one optical module, an outer jacket, especially made of relatively deformable plastic, having a cylindrical general shape, freely surrounding the optical module consisting of a set of adjacent fibres which are independent or preferably housed in a confinement sheath, and at least one reinforcing element having a high mechanical strength, in particular a high tensile strength, in order to take up and absorb the forces exerted on the cable without transferring them to the optical module, wherein it includes an immobilizing member operating by clamping the jacket from outside the latter, at least one hollow protective sealing plug capable of being placed around and possibly crimped onto a part of the reinforcing element that extends from the front end of the jacket which has been cut beforehand in order to strip the optical module, this plug including a flange, possibly protruding, bearing against a plane surface made on the end of the jacket, and a locking assembly for clamping over the plug, this locking assembly being formed by two oppositive jaws which mutually interact, closing together onto the external surface of the plug in a diametral plane passing through the axis of the latter, means being furthermore provided for closing together the locking assembly for clamping over the plug with respect to the member for immobilizing the jacket, so as locally to compress the latter by means of the flange of the plug, thereby achieving sealing with respect to the outside of the reinforcing element extending into the thickness of the sheath, parallel with its longitudinal axis.

BACKGROUND OF THE INVENTION 
The present invention relates to a device for fixing, earthing and sealing 
the end or the unsupported part of a cable comprising at least one optical 
module, consisting of one optical fibre or a set of optical fibres which 
are independent or joined together into a ribbon, this device including an 
outer protective jacket inside which is arranged at least one reinforcing 
element intended, in particular, to prevent forces exerted on the cable 
from being transmitted to the optical module lying inside the jacket. 
In current conventional solutions for cables of this kind, the optical 
fibres are more generally arranged directly in the central part of the 
sheath which is in the form of a reinforced tube or else in adjacent 
parallel passages, but inside the jacket. 
The reinforcements, metallic or non-metallic, are preferably diametrically 
opposed and incorporated in the jacket while it is being manufactured by 
extrusion. 
In particular, although not exclusively, these reinforcements may consist 
of steel strands which, although they have a high mechanical strength, are 
not sealed along their longitudinal direction, in such a way that, at the 
end of the cable where the optical fibres of the module or modules 
contained in the jacket may be joined together by appropriate splices to 
one or more application devices, or another cable (in the case of the 
in-line connection of two ends of cables), or else in the unsupported part 
of this cable in a stripped region thereof after removing a portion of the 
jacket in order to allow access to the optical module and to make a 
T-connection on one or more fibres thereof without cutting the remaining 
fibres, external moisture can travel along these strands, which has 
serious drawbacks. 
Applying a material in the form of a gel around the reinforcements in the 
regions where the jacket is stripped may, at least in part, prevent this 
drawback but it runs the risk of contaminating the case or other 
connection member containing the splices for linking the optical fibres. 
Moreover, in conventional solutions, on the end of a cable or in an 
intermediate region thereof, it is necessary to fasten this cable 
securely, in particular by suitably anchoring its reinforcements, further 
providing effective earthing when the latter are metallic. 
However, in the known arrangements, commonly used in practice today, the 
fastening techniques employed do not allow immobilization of the 
reinforcements in the longitudinal direction of the cable, along the 
natural extension of these reinforcements, but use laterally offset 
locking means, which generally leads to a phenomenon of twisting and/or 
curvature of the jacket and the reinforcements, and may even cause this 
jacket to be cut, thereby creating stresses on the optical fibres 
themselves, above all if the reinforcements are forced to cross with 
respect to the exit axis of the optical fibres. 
SUMMARY OF THE INVENTION 
The subject of the present invention is a fixing and sealing device for 
optical cables which prevents these drawbacks, making it possible, on the 
one hand, to immobilize the reinforcements within the jacket in their 
natural direction without inducing forces on the optical fibres 
themselves, this device making it possible furthermore to achieve a high 
degree of sealing on these reinforcements, right at the regions where they 
emerge from the jacket cut beforehand, independently of the optical fibres 
which preserve their total integrity, which sealing prevents penetration 
of moisture into the jacket or into its contents, in the event of an 
accident on the unsupported part of the cable. 
The invention also relates to a device which, in the case where the 
reinforcements of the jacket are metallic, enables these reinforcements to 
be earthed effectively, the means employed themselves being independent of 
the structure of the optical module or modules consisting of the fibres 
proper, it being possible for these fibres to be distributed either in a 
single module loosely arranged in a hollow part extending longitudinally 
at the centre of the jacket or in several parallel modules distributed in 
neighbouring passages, preferably arranged inside this jacket 
symmetrically with respect to the axis of the latter. 
Finally, the object of the invention is to provide a device which is 
compact and, in particular, the overall size of which is sufficiently 
small so that it can, if required, be inserted or connected in an appended 
member fixed by its intermediary on the end of the cable, in order to 
allow it to be pulled when laying it into a duct. 
For this purpose, the device in question, for fixing, earthing and sealing 
a cable, including at least one optical module, an outer jacket, 
especially made of relatively deformable plastic, having a cylindrical 
general shape, freely surrounding the optical module consisting of a set 
of adjacent fibres which are independent or preferably housed in a 
confinement sheath, and at least one reinforcing element having a high 
mechanical strength, in particular a high tensile strength, in order to 
take up and absorb the forces exerted on the cable without transferring 
them to the optical module, is characterized in that it includes an 
immobilizing member operating by clamping the jacket from outside the 
latter, at least one hollow protective sealing plug capable of being 
placed around and possibly crimped onto a part of the reinforcing element 
that extends from the front end of the jacket which has been cut 
beforehand in order to strip the optical module, this plug including a 
flange, possibly protruding, bearing against a plane surface made on the 
end of the jacket, and a locking assembly for clamping over the plug, this 
locking assembly being formed by two opposite jaws which mutually 
interact, closing together onto the external surface of the plug in a 
diametral plane passing through the axis of the latter, means being 
furthermore provided for closing together the locking assembly for 
clamping over the plug with respect to the member for immobilizing the 
jacket, so as locally to compress the latter by means of the flange of the 
plug, thereby achieving sealing with respect to the outside of the 
reinforcing element extending into the thickness of the sheath, parallel 
with its longitudinal axis. 
Preferably, the reinforcing element consists of at least one metallic 
filament, especially a steel wire, this being in the form of one or more 
straight or twisted strands. In an alternative form, the reinforcement may 
be made of a composite material, of reinforced polymer, of the kind 
comprising a filament or a roving of organic, inorganic or metallic 
materials, incorporating a reinforcement consisting of natural or man-made 
fibres, especially of the kind comprising glass fibres or a plastic 
roving. 
Also preferably, the outer jacket surrounding the optical module is made of 
high-density polyethylene. The hollow plug, for its part, consists of a 
metallic material, especially copper or aluminium. 
In a preferred embodiment, the jacket includes two parallel reinforcing 
filaments, diametrically opposed with respect to a single optical module 
arranged in the axis of this tube-shaped jacket, the end of each of these 
two reinforcements being associated with a hollow protective sealing plug. 
According to a particular characteristic, a flat seal is mounted between 
the plane surface on the end of the jacket and the flange of the hollow 
protective sealing plug of each reinforcement. Preferably, this seal is 
made of a plastic, similar to or different from that of the jacket. In 
particular, this seal may be made of a polymer or an elastomer. 
According to another characteristic, the means for closing together the 
immobilizing member and the locking assembly for clamping over the plug 
consist of at least one, and preferably two, longitudinal screws parallel 
to the axis of the jacket, these screws being self-tapping or passing 
through the locking assembly and being engaged in tapped bores in the 
immobilizing member, or vice versa, in such a way that turning the screw 
clamps the member and the assembly together. 
Advantageously, the member for immobilizing the jacket consists of two 
adjoining parts clamped against each other, trapping the jacket between 
them, these two parts being closed together by screws extending 
perpendicular to the axis of the jacket. 
According to another alternative form, the jacket includes a central 
conduit from which extends the optical module which is arranged coaxially 
inside the reinforcing element which has a tubular profile and is housed 
in this conduit, the protective sealing plug being pierced axially by a 
hole in its bottom opposite its bearing flange in order for the module to 
pass freely. 
Depending on the case, the seal and the plug are slipped over the end of 
the reinforcing element when the jacket is stripped at one end. In the 
case of lateral tap made on the optical module, the seal and the plug each 
consist of two parts, suitable for being put together in order to surround 
the optical module. If required, the seal may be cut laterally, its edges 
being mutually connected by an omega-shaped or other-shaped profile.

Drawn on these figures are identical reference numbers for designating 
members which are similar to one another. 
DETAILED DESCRIPTION OF THE INVENTION 
In the first embodiment shown in FIGS. 1 to 5, the reference 1 designates 
in general a fibre-optic cable, which includes, in this example, from its 
periphery towards its central axis, a protective jacket 2, generally made 
of a suitable plastic, especially high-density polyethylene, it being 
optionally possible for the jacket itself to be covered with an external 
protective sheath (not shown). 
In the thickness of the jacket, preferably arranged symmetrically on either 
side of its central axis, are housed two reinforcing elements, 
respectively 3 and 4, each of these being in the form of a metallic 
filament or a strand of straight or twisted wires, advantageously made of 
steel, so as to impart a high mechanical strength to these reinforcements 
and above all to allow them to take up the tensile, compression or even 
bending forces and, depending on the case, to limit the thermal expansion 
phenomena, which may be exerted on the cable itself. 
The reinforcing filaments 3 and 4 are preferably put in place in the jacket 
while it is being manufactured, each being housed inside a passage 5 
provided in the thickness of the jacket 2, the two corresponding passages 
being parallel to each other and having a diameter adapted to the overall 
size of the metallic filaments which may have a slight play in these 
passages, which passages thereafter are not completely sealed, so much so 
that, at the end of the cable, when its jacket is cut as illustrated in 
FIGS. 1 and 2, the moisture of the ambient air can possibly penetrate 
between each filament and the internal surface of the corresponding 
passage in the jacket, which leads to the drawbacks already mentioned. 
It should be noted that the reinforcing filaments 3 and 4 may be made of a 
material other than steel, for example by means of a composite material 
formed by fibres or rovings, these being bonded together by a resin which 
can polymerize on exposure to heat or to radiation, it being possible for 
each filament furthermore to include a stiffening reinforcement, 
especially one based on glass fibres. 
Finally, arranged in the central part of the jacket 2 is an optical module 
6 which extends along a conduit 7 provided along the axis of the cable 1, 
there being a sufficient play around the module 6 in this conduit so as to 
limit any reaction and friction force of the jacket on this conduit. 
The optical module 6 consists, in a manner known per se, of an outer 
protective sheath 8 inside which extend, along the length of the cable, a 
plurality of optical fibres 9, these being independent or possibly joined 
together in several groups, these then being in the form of fibre ribbons 
10, as is illustrated, for example, in the alternative form in FIG. 12. A 
filling material may be provided inside the sheath 8 around the fibres 9. 
In accordance with the invention, the cable 1 thus formed is associated 
with a fixing and sealing device, capable especially, as shown in the 
first example considered in FIGS. 1 to 5, to be mounted on one of the ends 
of the cable, in a region of the cable where the jacket 2 has been cut 
transversely and the two metallic reinforcements 3 and 4, which protrude 
slightly from the corresponding cut face 11 of this jacket, only the 
optical module 6 being left intact, extending beyond its conduit 7 in the 
jacket, it being possible for one or more of the fibres 9 to be extracted 
from the sheath 8 and connected to any application device or connected to 
the end of another fibre, these not being shown in this case. 
According to the invention, the device includes a member 12 for clamping 
and immobilizing the jacket 2, hollow protective plugs, respectively 13 
and 14, for the projecting ends of the reinforcing filaments 3 and 4 and, 
finally, a locking assembly for clamping over these plugs, this assembly 
being provided with locking screws 16 and 17, making it possible to seal 
the arrangement and, in particular, to prevent external moisture from 
penetrating into the jacket or flowing outwards in the passages 5 of the 
reinforcing filaments. 
Preferably, the hollow protective plugs 13, 14 are made of a metallic 
material, especially copper or aluminium, so as to be able to be easily 
compressed onto the ends of the reinforcing filaments 3 and 4, as 
explained later. 
The clamping and immobilizing member 12 is produced by means of two 
semicylindrical half-rings 18 and 19, capable of being joined together 
around the jacket, clamping the latter from the outside, the two rings 
being closed together, in the common diametral plane in which they fit 
around the jacket, by means of screws, such as 20 and 21, engaged on 
either side of this jacket in drillholes 22 and 23, these being 
perpendicular to this plane provided in one of the two rings, these screws 
interacting with tapped bores in the other ring, or vice versa. 
The hollow protective plugs 13 and 14 are provided so as to be fitted, from 
the outside, over the ends of the filaments 3 and 4 and, for this purpose, 
include internal blind housings designated in the drawings by the 
references 24 and 25. Each plug is closed at its opposite end, this end 
nevertheless possibly including a blind hole 26 suitable for receiving the 
end of an earthing wire 27 which engages in this hole in the manner of an 
electrical plug, as shown in FIG. 1, but not in FIG. 2 in order not to 
clutter up its drawing. 
Moreover, on its end facing the jacket 2, each plug 13 and 14 includes a 
bearing flange 28, making it possible to achieve the necessary sealing 
right at this jacket in the region where the reinforcing filaments 3 and 4 
emerge slightly therefrom. 
Finally, the locking assembly 15 of the device includes two jaws, 
respectively 29 and 30, these being similar to the half-rings 18 and 19 of 
the immobilizing member but including certain specific arrangements. 
In particular, the two jaws 29 and 30 include, in their plane faces 
intended to be closed together in order to clamp the hollow plugs 13 and 
14 together, semicylindrical open housings 31 and 32, the diameter of 
which corresponds substantially to that of the plugs, in such a way that, 
when the two jaws are closed together by means of screws 33 and 34 which 
extend perpendicular to the plane faces of these jaws and in turn pass 
through drillholes 35 in one of them in order to interact with a tapped 
bore 36 provided in the other, the hollow plugs are progressively pressed 
and thus crimped onto the ends of the reinforcing filaments 3 and 4 
engaged in the blind housing 24, 25 in these plugs 13 and 14. 
In the central part, the jaws 29 and 30 each include a recess 37, having a 
larger radius than that of the housings 31 and 32 so as to allow the 
optical module 6 to pass freely through the locking assembly 15. 
Finally, the device is completed by a flat seal 38 (see FIG. 5), preferably 
made of a polymer or elastomer, intended to be applied against the end 
surface 11 of the jacket 2 (see FIG. 2), this seal being in the form of a 
washer provided with two lateral drillholes, respectively 39 and 40, 
enabling the reinforcing filaments 3 and 4 to pass through the seal, and 
with a central hole 41 for the optical module 6 to pass through. 
When mounting the device, after having stripped the jacket 2 right at its 
end face 11, leaving the ends of the reinforcing filaments 3 and 4 
projecting, the immobilizing member 12 is put into place with its 
half-rings 18 and 19 clamping the jacket from the outside. 
In a second step, the flat seal 38 is put in place in such a way that the 
filaments 3 and 4 pass through the drillholes 39 and 40 in it, the optical 
module 6, at the centre of the jacket, for its part passing freely through 
the hole 41 in this seal. 
In the next step, the hollow plugs 13 and 14 are slipped over the ends of 
the reinforcing filaments 3 and 4 into the housings 24 and 25 in these 
hollow plugs, until their flange 28 butts up against the facing surface of 
the flat seal 38. If required, the ends of the earth wires 27 are slipped 
into the holes 26 in these plugs. The plugs 13 and 14 must be compressed 
before being immobilized. 
In the following step, the two jaws 29 and 30 are put in place, without 
clamping the plugs 13 and 14, in such a way that these plugs can slide. 
In the next step, the screws 16 and 17 are turned so as to move 
progressively towards the immobilizing member 12 the assembly 15 for 
locking the flanges 28 of the plugs 13 and 14 so as to bear on the joint 
38, the latter itself being applied against the end face 11 of the jacket 
2, blocking off the mounting clearance between the reinforcing filaments 3 
and 4 and their passages 5 in the jacket 2, thereby achieving perfect 
sealing of the arrangement. 
Finally, in a last step, the two aforementioned jaws 29 and 30 are clamped, 
by acting on the screws 20 and 21, so as to clamp the plugs 13 and 14, 
thereby crimping them onto the filaments 3 and 4. 
In this arrangement, the reinforcing elements 3 and 4 remain immobilized in 
their natural direction, parallel to the axis of the cable 1, without 
causing these filaments to bend due to lateral twisting, as occurs in the 
solutions of the prior art. 
Moreover, the controlled compression of the seal 38 on the plane end 11 of 
the jacket 2 allows limited compression of this joint, thereby enabling, 
by virtue of the flanges 28 of the hollow plugs 13 and 14, perfect sealing 
to be achieved, preventing any penetration of moisture into the jacket or 
preventing this moisture in the cable from going towards and getting into 
the case. 
Advantageously, a suitable quantity of a sufficiently fluid product, such 
as a petroleum or silicone gel may be put in place right at the central 
conduit 7 through which the optical module 6 passes, once again preventing 
moisture from penetrating into this conduit but exerting no force on the 
optical module itself which remains perfectly free with respect to its 
jacket 2 and reinforcing elements 3 and 4. 
In an alternative embodiment illustrated in FIG. 6, the flanges 28 provided 
on the ends of the plugs 13 and 14 interact directly with the plane face 
11 made on the end of the jacket 2 of the cable 1 in order to achieve 
sealing with respect to the clearances provided between the passages 5 and 
the reinforcing filaments 3 and 4, thereby in this case avoiding the use, 
envisaged in the embodiment in FIGS. 1 to 5, of the flat seal 38. 
In both of the above examples, provision was made for the jacket 2 of the 
cable 1 to be cut at the end of the latter so as to leave the optical 
module 6 free and to allow, if required, the fibres 9 contained in the 
latter to be connected directly to other fibres, or even to application 
devices. 
The embodiment illustrated in FIG. 7 corresponds to a different use in 
which the optical module 6 is not cut transversely but only opened 
laterally by a lateral slit 42, enabling any one of the fibres 9 to be 
extracted from this module and to be connected by means of a splice 43 to 
a similar fibre 9' of a cable 1', separate from the cable 1 itself. FIG. 7 
illustrates such an arrangement, which includes two devices, respectively 
D1 and D2, for a first cable 1, each of these devices, in accordance with 
the embodiments described, comprising an immobilizing member 12, a locking 
assembly 15, a flat seal 38 and screws 16 and 17 for moving these two 
parts closer together in a controlled manner, so as to make it possible, 
after crimping the hollow plugs 13 and 14 onto the ends of the 
reinforcements 3 and 4 of the cable [lacuna]. 
In this case, the optical module 6 is no longer cut, the cable 1' being 
connected by tapping with the cable 1, the fibres 9 and 9' of the two 
cables being joined together by their splices 43, as shown. The whole 
assembly is preferably mounted in an external splice case 44. 
In the alternative form illustrated in FIG. 8, the cable 1 has a special 
shape, the jacket 2 surrounding, inside two separate parts 2a and 2b, 
respectively the optical module 6 and a reinforcing element 3 which, this 
time, is just a single one shifted laterally with respect to the region 
where the optical fibres 9 are distributed. The two parts 2a and 2b of the 
jacket are joined together by a linking strip 45. 
In this embodiment, the device once again includes an immobilizing member 
12 and a locking assembly 15, capable of crimping, from the outside, the 
hollow plug 13 which surrounds the end of the reinforcing element 3. In 
this case, the optical module 6 is no longer arranged axially between the 
half-rings 18 and 19 clamped together by the screws 20 and 21 but offset 
laterally with respect to the reinforcing element 3, as shown in FIGS. 9 
and 10. 
In another embodiment, shown diagrammatically in FIGS. 11 and 12, the cable 
1 includes a jacket 2 but has a tube-shaped reinforcing element 46 housed 
coaxially inside the jacket surrounding the optical module 6. 
In this alternative form, the reinforcing element passes through a hollow 
plug 47, pierced in its bottom in order to allow the optical module 6 to 
pass through freely, this plug including a flange 48 bearing on the end of 
the jacket in order to achieve the required sealing in the manner already 
explained. 
Thus, a device of very simple design is produced which has the advantages 
already mentioned, especially fixing, along the axis, the various elements 
of the cable, furthermore achieving perfect sealing right at its 
reinforcing elements. 
Of course, it goes without saying that the invention is not limited to the 
examples described hereinabove and shown in the appended drawings; on the 
contrary, it embraces all the alternative forms thereof which come within 
the scope of the hereto-appended claims. 
In particular, in the case where the optical module itself is not cut, that 
is to say when one or more optical fibres of this module, but not all of 
them, are designed to be connected to other equivalent fibres of a cable, 
making a lateral tap on the first, it is clear that the seal 38, through 
which the optical module passes, can be put in place on the latter only in 
so far as it is cut beforehand laterally in order to be arranged around 
the sheath of the module. 
In this case, the edges of the seal right at its cut are advantageously 
joined together by means of an omega-shaped or other-shaped profile which 
enables them to be connected in a secure manner after the seal has been 
put in place on the module. 
In the alternative form in FIGS. 11 and 12, where the optical module passes 
through the plug for protecting the reinforcing element, this reinforcing 
element itself being of tube shape, it should be pointed out that the 
protective plug 46 must also be made in two parts which are brought 
together around this module. 
Finally, in the preceding examples, it has been envisaged that the plugs 13 
and 14 include, at their end intended to bear on the seal 38 or on the 
plane end face 11 provided at the end of the jacket 2, a slightly 
protruding flange 28, ensuring satisfactory compression in the sealing 
region. As a variant, this flange may be formed directly by the end of 
each plug 13, 14 or 47, not provided with a transverse shoulder, the plug 
then advantageously including raised features or striations in its 
external surface, in such a way that it can be moved, translationally in 
the direction of the sealing to be achieved, by the jaws 29 and 30 clamped 
directly over this or these plugs.