FR2676287A1 - Device and method for the breaking-out of optical fibres from a jacketed end of a unitube cable - Google Patents

Abstract

The device according to the invention includes a central bundle (assembly) of optical fibres (10) inside a central tube (12) protected by an outer jacket (16) in which lateral carriers (15) are embedded, and comprises: - a main body (22) pierced along its longitudinal axis (X) in order to form an internal cavity which includes an inlet opening (25) for the cable, an outlet opening (28) for the broken-out fibres and, between the openings, a chamber (27) for breaking out the fibres; - means (23) fastened to the fibres housed in the outlet opening and provided with channels (33) intended for the passage of the fibres; - the same number of bores (32) as lateral carriers (15) in order to receive the latter, the bores (32) having one of their ends in communication with the inlet opening and the other not emerging into the break-out chamber; - means (41, 42) for the axial retention of the cable in the body (22).

Description

Device and method for flourishing optical fibers beyond a sheathed end of unitube cable
The present invention relates to a device for spreading optical fibers beyond a sheathed end of unitube cable, as well as a method for implementing such a device.

 Unlike conventional fiber optic cables, which include as a mechanical reinforcement element, a central carrier or a grooved rod around which bundles of optical fibers or unitary optical fibers are arranged, unitubes cables, the cross section of which is given to the FIG. 1, comprise a central bundle of optical fibers 10 possibly immersed in petroleum gel 11 and installed in a central tube 12 made of polyamide for example, itself possibly surrounded by a longitudinal sealing sheath 13 made of polypropylene for example, then optionally, a screen 14 made of steel (or any other sufficiently rigid material) having the role of mechanically reinforcing the structure against compression. In addition, diametrically opposite and around the screen 14 are two cylindrical carriers 15 steel, embedded in an outer sheath 16 of medium or high density polyethylene extruded around 'them during the manufacture of the cable.

The carriers 15 serve to protect the optical fibers from the tensile forces applied to the cable during installation and which may deteriorate their performance. They can also be made of wicks of aramid or glass fibers, or of any other material capable of protecting the optical fibers by supporting the tensile forces applied to the cable, such as for example wicks of Kevlar distributed all around the structure. cable center.

 The unitube cable 20 thus formed therefore differs from conventional cables in that the mechanical reinforcement means are located around the optical fibers.

 The flourishing of optical fibers, that is to say their extraction from the basic structure of the cable which contains them, is imposed either at the ends of the cable, where each fiber must be protected by a sheath and provided with a connector , either at splices or in-line divisions where the fibers can be protected by a sheath, individually or in groups. The flourishing devices must generally meet, among other things, the following conditions - do not provide constraints that could lead to, or by crushing , either by curvature according to a radius of curvature that is too small, a local increase in the attenuation of the fibers, - ensuring the mechanical protection of the fibers at the point where they are extracted from the cable, the maintenance of their sheaths relative to the device being sufficient to allow them to be handled without risk of introducing tensile, compression or torsional stresses during connection operations, - possibly guarantee a seal against the external environment, - ensure sufficient mechanical strength of the various elements constituting the device to prevent any significant relative movement of one of them with respect to the others as well as with respect to the friend and to the cable sheath.

Disclosure devices are known for optical fibers freely contained in a plastic tube. The patent
GB-2 166 563, for example, describes a device for developing optical fibers contained in a plastic tube, consisting of two parts fitted one inside the other. The first of these two parts has an inlet opening intended to receive a tube containing optical fibers, and the second comprises an outlet opening for receiving a barrel for bursting the optical fibers blooming in an intermediate blooming chamber in communication with either of the two previous openings.

 Such a device does not provide housing means for the lateral carriers of a unitube cable. I1 can therefore not be adapted to the development of the optical fibers of such a cable.

 In addition, even if the first part has two ribs cooperating with two grooves in the second part for the axial maintenance of the various elements of the device with respect to each other, no means is provided to prevent the rotation of the tube containing the fibers in the entrance opening. Thus, a possible rotation of this tube around its axis could cause shearing of the optical fibers.

 The object of the present invention is therefore to produce a blooming device which can be used to extract the optical fibers beyond the sheathed end of a unitube cable with lateral carriers in order to carry out the connection operations, and guaranteeing the axial maintenance of the various elements with respect to each other.

 To this end, the present invention provides a device for developing optical fibers beyond a sheathed end of a unitube optical fiber cable, said cable comprising a central assembly of optical fibers inside a central tube. protected by an outer protective sheath in which one or more lateral carriers are embedded, said device comprising - a main body pierced right through along its longitudinal axis to form an internal cavity delimited by a wall and comprising an opening entry of said cable, an outlet opening of said spread fibers, and between said openings, a blooming chamber of said fibers released from said cable, - means integral with said fibers housed in said outlet opening of said body and provided with channels intended for passage said fibers, characterized in that it also comprises as many bores as lateral carriers, said a lesions being provided in said body to receive said carriers, each of said bores having one of its ends in communication with said inlet opening and the other of its ends not opening into said development chamber, and in that it also comprises means for axially maintaining said cable in said body.

 Advantageously, the internal cavity is formed by four cylindrical bores of the same axis arranged one in communication with the other, a first of these bores constituting the inlet opening and located around a first portion of the cable not exposed, a second of these bores with a diameter smaller than that of the first bore, located around a second portion of the cable in which the outer sheath has been removed so as to leave the central tube bare, a third of these bores constituting the development chamber fibers, and finally a last of these bores constituting the outlet opening.

 When the carrier (s) are made of steel, the means for axially holding these carriers include screws which tighten against the carriers through the wall of the body.

 When the carrier or carriers consist of wicks such as glass fiber wicks, aramid wicks, or kevlar wicks, the means for axially holding these carriers comprise so-called blocking plates inserted between each of the carriers and the wall of the corresponding bore and against which tighten locking screws through the wall of the body.

 Advantageously, the bores receiving the carriers can be blind.

 In addition, the means integral with the fibers comprise a barrel provided with fiber passage channels, each of the channels being lined with a fiber protection tube.

 The means secured to the fibers also include a notch cooperating with a screw located in the body and allowing the axial means to be secured to the fibers.

 Furthermore, the means for axially holding the various elements comprise screws for locking axes orhtogonal to the axis of the body and abutting against the cable.

 Advantageously, the means for axially retaining the cable in the body also comprise a metal plate called a blocking plate, comprising a part curved at one of its ends and inserted into the second bore between the central tube and the wall of the internal cavity, so that the curved part is stopped by the wall of the internal cavity separating the first and second bores.

 When the central tube is protected by a metal screen against compression, a screen earthing wire can be welded to the screen, this wire reaching the screen through a passage window made in the wall of the screen. the cavity and in communication with the inlet opening.

 A process for developing optical fibers beyond a sheathed end of unitube cable using a device according to the invention comprises the following operations: a) the outer sheath of the cable is cut and eliminated from the cable until to a stop section, over a length necessary for the fibers to flourish, b) the carriers are cut beyond the stop section over a length corresponding to that of the bores in which the carriers are received, c) the central tube is cut and eliminated beyond the stop section to leave the fibers free, d) the cable thus prepared is engaged in the body so that the optical fibers flourish in the flourishing chamber, and that the carriers are introduced into the corresponding bores, e) the axial retention means are installed, f) the fibers are introduced, in groups or individually, into the openings of the means of which they are intended to be be secured, g) the means secured to the fibers are installed and then held axially in the outlet opening.

 Advantageously, the installation of the axial holding means is carried out in the following manner - before the cable is fully engaged in the internal cavity, a plate called a blocking plate comprising a curved part at one of its ends is inserted, by a so-called passage window made for this purpose in the body and in communication with the inlet opening, between the bare central tube and the wall facing the internal cavity, so that the curved part is in the inlet opening, - locking screws are tightened in abutment against the carriers, against the sheath and against the plate.

 Finally, when the central tube is protected by a metal screen against compression, a grounding wire can be welded, before the cable is fully engaged in the body, to the metal screen, this wire accessing the screen. by a so-called passage window made in the body in communication with the entry opening.

 Other characteristics and advantages of the present invention will appear in the following description of a device according to the invention and of its implementation method, given by way of illustration and in no way limitative.

 In the following figures - Figure 1 shows in cross section a unitube cable, - Figure 2 shows in elevation a flourishing device according to the invention, for unitube cable with twelve optical fibers, - Figure 3 is a side view in direction III of Figure 2, - Figure 4 is a section along the line IV-IV of Figure-2, - Figure 5 is a section along the line VV of Figure 4, - Figure 6 is a elevation view of a possible alternative for the device according to the invention, shown without unitube cable.

 Figure 1 was described during the presentation of the state of the art.

 In Figures 2 to 5, there is shown a device 21 according to the invention, the mounting of this device 21 on the unitube cable 20 of Figure 1 being completed. The optical fibers 10 are spread to the left of the device 21.

The device 21 comprises a body 22 in brass or in "Duralumin" (registered trademark) for example and of cylindrical external shape, and a bursting barrel 23 in "Delrin" (registered trademark for example. The body 22 is pierced on the side in part along its axis X, to constitute an internal cavity delimited by a wall and formed by four cylindrical bores 25, 26, 27 and 28 of the same axis
X and in communication with each other. The bore 25, also called the cable entry opening 20, has a diameter slightly greater than the outside diameter of the cable 20. A window 29 (which is best seen in FIG. 2) of rectangular shape terminated by a half circle is formed in the body 22, at the end opposite to that of the flourishing of the fibers 10; the window 29 is in communication with the bore 25 and serves to engage a blocking plate 24 and possibly to allow passage to a grounding wire 30 of the steel screen 14 of the cable 20. The plate blocking 24 is a thin metal strip, of width slightly less than the diameter of the central tube 12 and of length slightly greater than that of the bore 26. It further has a curved end 31 in order to facilitate its introduction and setting placed through window 29 in bore 26.

 The intermediate bore 26 has a diameter less than that of the bore 25, and slightly greater than that of the central tube 12 of the cable 20 in order to accommodate both the tube 12 and the locking plate 24. Two blind cylindrical bores 32 , whose axis is parallel to the X axis, are drilled on either side of the bore 26 and in communication with the bore 25. They are each intended to receive one of the steel carriers 15 of the cable 20. The carriers 15 abut against the blind end of the bores 32.

 The central tube 12 extends into the bore 27 also called the blooming chamber and in which the fibers 10 flourish. The diameter of the chamber 27 is greater than that of the bore 26 and sufficient to allow the blooming fibers 10.

 Finally, the bore 28, also called the fiber outlet opening 10, and located at the end of the body 22 is intended to accommodate the barrel 23. Its diameter is thus slightly greater than that of the barrel 23. The barrel 23 is cylindrical and pierced, in the example described, with twelve cylindrical bores or channels 33 (see FIG. 4) with axes parallel to its axis and parallel to the X axis once the barrel is installed in the bore 28. The number of channels 33 is equal to the number of unit optical fibers to be extracted, in the case where the device 21 is used at one or the other of the ends of the cable 20. On the other hand, when the device 21 is used for a splice or a division online, the fibers can be connected by bundles or groups. In this case, the barrel 23 has as many channels as there are bundles (for example, two channels for a unitube cable with twelve fibers divided into two bundles of six fibers), the diameter of the channels then being adapted. The barrel 23 further comprises a groove 34 (see FIG. 3) cooperating with a blocking screw 40 installed in the body 22, and each of the channels 33 is provided with a protective tube 35 of the fiber (s) ) optics it receives. The tubes 35 are glued to the channels 33 in order to allow the fibers 10 to be handled without risking damaging them.

 According to an alternative of the device according to the invention shown in FIG. 6, the body 22 can consist of two parts of cylindrical external shapes 22A and 22B. The inlet opening and the bore intended to receive the blocking plate are located in the portion 22A of smaller diameter, and the expansion chamber as well as the outlet opening in the portion 22B of larger diameter. Part 22B is screwed onto part 22A at the level of a thread made for this purpose (not shown). Such a device can in particular be used when the cable to be bloomed comprises a large number of optical fibers (48 and more for example) for the blooming of which the blooming chamber 27 of the device of FIGS. 2 to 5 does not have a sufficient diameter. Apart from this modification, the device 21 ′ thus produced comprises the same elements as the device 21 in FIGS. 2 to 5.

 The invention will be better understood from the following description of a method of implementing the device according to the invention.

 In a first step, the cable 20 is prepared. For this, the outer sheath 16 is cut and eliminated at the end of the cable 20, to a stop section 50, over a length corresponding to the accessible fiber requirements. The two lateral carriers 15 thus released are then sectioned at about 20mm from the stop section 50 of the outer sheath 16. Then, the steel screen 14 and the sealing sheath 13 are cut and eliminated at about 5mm from the stop section 50 of the sheath 16. The grounding wire 30 can then be welded if necessary on the steel screen 14. Finally, the central tube 12 is cut and eliminated about 25mm from the section stop 50 of the sheath 16, taking care not to damage the fibers 10.

The fibers 10 are then released from the basic structure of the cable 20, either individually or by bundles of several fibers, and cleaned using an alcohol cloth for example to remove petroleum gel 11.

 A second step then consists in preparing the barrel 23, that is to say in sticking in the channels 33 the corresponding protective tubes 35.

 In the third and last step, the device is mounted on the cable. As the barrel 23 is not yet installed in the body 22, the fibers 10 are engaged in the successive bores 25, 26, 27 and 28 so as to engage the central tube 12 and the carriers 15 in the respective bores 26 by a few millimeters and 32. The blocking plate 24 is then introduced through the window 29, between the central tube 12 and the wall facing the bore 26, so that the curved end 31 remains outside the bore 26 , in the bore 25. The cable 20 is then pushed to the left of Figures 2, 4 or 5 until the curved end 31 abuts against a re-entrant shoulder 36 created by the bores 25 and 26. for soldering the possible grounding wire 30 is then located in the bore 25 so as to allow the wire 30 to be released by the window 29. Two screws 41 for clamping the carriers 15, diametrically opposed and installed in two corresponding tapped holes, perpendicularly t to the X axis and to the carriers 15, are then tightened in abutment against the carriers 15 through the body 22. Similarly, two screws 42, parallel to the screws 41 and also diametrically opposite are tightened in abutment against the outer sheath 16 of the cable 20 and thus ensure the axial maintenance of the cable 20. Then two other screws 43 perpendicular to the screws 41 and 42, and side by side are tightened in abutment against the locking plate 24. The fibers (or groups of fibers as required ) are then engaged in the protective tubes 35 of the barrel 23 which is then installed in its housing 28 at the end of the body 22 so that the groove 34 is located in the extension of a tapped hole 44 made in the body 22. The screw 40 is then introduced into the hole 44 and tightened in abutment against the bottom of the groove 34 to block the barrel 23 and prevent its rotation about the axis X.

 Thus, the device according to the invention can be used on any type of unitube cable containing mono or multimode fibers, whatever their number and arrangement (free, in bundles, in ribbons), and makes it possible to extract the fibers from the central tube of the cable to treat them individually or in groups in order to make the connections (at the ends or at the level of splices or divisions in line). To do this, it suffices to adapt the barrel used to the number and arrangement of the fiber outlet. In addition, all the devices according to the invention can be made up of two parts which are screwed together, in order to be adapted to the number of fibers to be extracted.

 The blind bores 32 provided to receive the steel carriers 15 of the unitube cable also serve to prevent any rotation of the cable support structure relative to the optical fibers, which avoids possible shearing of the latter. The bores 32 can also be open towards the outside of the body 21.

However, it is preferable that they do not lead to the blooming chamber 27 so that the carriers of the cable 20 do not damage the fibers 10.

 The geometry of the barrel 23 and of the blooming chamber 27 does not introduce any significant curvature of the fibers 10 which risks deteriorating their performance. In addition, the protective tubes 35 provide mechanical protection of the fibers at the point where they are extracted from the cable. Thanks to the use of numerous locking screws 40, 41, 42, 43, the various elements of the device are held axially with respect to the friend and the sheath of the cable.

 The use of the locking plate 24 is preferable. Indeed, the direct use of locking screws 43 more rigid than the tube 12 would risk leading to deterioration of the tube 12 itself and then of the fibers that it protects. This is why a blocking plate 24 is used as an interface between the tube 12 and the screws 43 making it possible to distribute the blocking forces imposed by the screws 43 over the entire length of the central tube 12 and to ensure the axial maintenance of the tube 12.

Thus, possible torsional movements which can cause shearing and therefore the deterioration of the optical fibers are avoided.

 Obviously, the device and the method according to the invention are not limited to the embodiment which has just been written.

 In particular, when the carriers 15 are two strands of glass fibers for example, the locking screws are tightened against these strands by means of locking plates similar to the plate 24 so as not to damage the glass fibers.

Furthermore, when the carriers consist of locks of
Kevlar distributed all around the screen 14 for example, at the moment when the outer sheath 16 is eliminated, these locks are brought together to form two (or more) braids, then introduced into corresponding bores opening towards the outside of the body 21.

 In addition, the bores intended to receive the possible carriers are not necessarily parallel to the axis X. They are as numerous as there are carriers of the cable.

 The body 22 and the barrel 23 can be either of metal or of plastic. When the body 22 is made of plastic, it is preferable to increase the diameter of the various locking screws and the thicknesses of the parts of the body which they pass through so as not to damage the latter during tightening.

 Finally, the use of a grounding wire 30 is not compulsory. However, when applying voltages to the steel screen, it is preferable to earth it in order to protect users or possible installers.

 We can of course replace any means with equivalent means without departing from the scope of the invention.

Claims (13)

1 / Device for developing optical fibers beyond a sheathed end of a unitube cable (20) with optical fibers (10), said cable (20) comprising a central assembly of optical fibers (10) at the interior of a central tube (12) protected by an external protective sheath (16) in which one or more lateral carriers (15) are embedded, said device comprising - a main body (22) pierced right through from its longitudinal axis (X) to form an internal cavity delimited by a wall and comprising an inlet opening (25) of said cable (20), an outlet opening (28) of said floured fibers (10), and between said openings , a blooming chamber (27) of said fibers (10) disengaged from said cable (20), - means (23) integral with said fibers (10) housed in said outlet opening (28) of said body (22) and provided with channels (33) intended for the passage of said fibers (10), characterized in that it comprises furthermore as many bores (32) as lateral carriers (15), said bores (32) being provided in said body (22) for receiving said carriers (15), each of said bores (32) having one of its ends in communication with said inlet opening (25) and the other of its ends not opening into said blooming chamber (27), and in that it also comprises means for axial retention (41, 42, 43, 24) of said cable (20) in said body (22). 2 / Device according to claim 1, characterized in that said internal cavity is formed of four cylindrical bores (25, 26, 27, 28) of the same axis (X) arranged one in communication with the other, a first of said bores ( 25) constituting said inlet opening and located around a first portion of said non-stripped cable, a second of said bores (26) of diameter smaller than that of said first bore (25), located around a second portion of said cable in wherein said outer sheath (16) has been removed so as to leave bare said central tube (12), a third of said bores (27) constituting said development chamber of said fibers (10), and finally a last of said bores (28 ) constituting said outlet opening. 3 / Device according to one of claims 1 and 2, characterized in that, when the said carrier (s) (15) are made of steel, the said axial holding means of the said carriers comprise screws (41) which are tightened against the said carriers with through the wall of said body. 4 / Device according to one of claims 1 and 2, characterized in that, when the said carrier (s) (15) consist of wicks chosen from wicks of glass fibers, wicks of aramid, and wicks of Kevlar , said axial holding means of said carriers comprise so-called blocking plates inserted between each of said carriers and the wall of said corresponding bore and against which clamping screws are tightened through the wall of said body (22). 5 / Device according to one of claims 1 to 4, characterized in that said bores (32) receiving said carriers (15) are blind. 6 / Device according to one of claims 1 to 5, characterized in that said means integral with said fibers (10) comprise a barrel (23) provided with passage channels (33) of said fibers (10), each of said channels (33 ) being provided with a protective tube (35) of said fibers (10). 7 / Device according to one of claims 1 to 6, characterized in that said means (23) integral with said fibers comprise a notch (34) cooperating with a screw (40) located in said body (22) and allowing the axial maintenance said means (23) integral with said fibers (10). 8 / Device according to one of claims 1 to 7, characterized in that said means for axially holding the various elements comprise locking screws (41, 42, 43) of axes orthogonal to said axis (X) of said body and coming abutting against said cable (20). 9 / Device according to one of claims 2 to 8, characterized in that said means for axially holding said cable (20) in said body (22) further comprises a metal plate (24) called blocking plate, comprising a part curved (31) at one of its ends and inserted into said second bore (26) between said central tube (12) and said wall of said internal cavity, so that said curved part (31) is stopped by said wall of said internal cavity separating said first and second bores (36). 10 / Device according to one of claims 2 to 9, characterized in that, when said central tube (12) is protected by a metal screen (14) against compression, a grounding wire (30) of said screen (14) is welded to said screen (14), said wire (30) accessing said screen (14) through a passage window (29) formed in said wall of said cavity and in communication with said inlet opening (25). 11 / Method for flourishing optical fibers beyond a sheathed end of unitube cable using a device according to one of claims 1 to 10, characterized in that it comprises the following operations a) said outer sheath (16) of said cable (20) is cut and eliminated from said cable (20) to a stop section (50), over a length necessary for the development of said fibers (10), b) said carriers (15) are cut beyond said stop section (50) over a length corresponding to that of said bores (32) in which said carriers are received (15), c) said central tube (12) is cut and eliminated beyond said stop section (50) to leave free said fibers (10), d) said cable (20) thus prepared is engaged in said body (22) so that said optical fibers (10) flourish in said blooming chamber (27), and that said carriers (15) are introduced into said al mages (32) corresponding, e) said axial holding means (41, 42, 43, 24) are installed, f) said fibers (10) are introduced, in groups or individually, into said openings (33) of said means (23 ) of which they are intended to be integral, g) said means (23) integral with said fibers are installed and then held axially in said outlet opening (28). 12 / A method according to claim 11, characterized in that the installation of said axial holding means is carried out as follows - before said cable (20) is fully engaged in said internal cavity, a plate (24) said plate blocking comprising a curved part (31) at one of its ends is inserted, by a window (29) called passage made for this purpose in said body (22) and in communication with said inlet opening (25), between said naked central tube (12) and the wall opposite said internal cavity, so that said curved part (31) is located in said inlet opening (25), - locking screws (41, 42, 43) are clamped in abutment against said carriers (15), against said sheath (16) and against said plate (24). 13 / A method according to one of claims 11 and 12, characterized in that when said central tube (12) is protected by a metal screen (14) against compression, a wire (30) for grounding is welded, before said cable (20) is fully engaged in said body (22), to said screen (14), said wire (30) accessing said screen (14) through a window (29) called passage made in said body (22) in communication with said inlet opening (25).