GB2296575A

GB2296575A - Fibre optic cable ,manufacturing process and plant

Info

Publication number: GB2296575A
Application number: GB9526191A
Authority: GB
Inventors: Yves Ruello; Annie Morgand; Anne-Cecile Reau; Dominique Erikson; Bernard Gay
Original assignee: France Telecom SA
Current assignee: Orange SA
Priority date: 1994-12-22
Filing date: 1995-12-21
Publication date: 1996-07-03
Anticipated expiration: 2015-12-21
Also published as: GB9526191D0; FR2728694B1; GB2296575B; FR2728694A1

Abstract

A fibre-optic cable 10, comprises at least one optical fibre 12, a primary coating 14 which surrounds the optical fibre or fibres and a rigid secondary coating 16 forming a microreinforcement which surrounds the primary coating 14. The secondary coating 16 is formed based on rovings coated with resin and the primary coating 14 is a decoupling agent based on a thermoplastic polymer. The cable may have an external polymer jacket (18, Fig. 4). Apparatus for making the cable includes a system for post-treating the decoupling agent, a constant speed haul off system and a constant tension take up. <IMAGE>

Description

MODULAR FOR FIBRE-OPTIC CABLES, NANUFACTURING PROCESS AND PLANT FOR THIS PURPOSE The present invention relates to the field of fibre-optic cables, in particular cables intended for subscriber distribution networks.

Future fibre-optic distribution networks will have to be constructed by means of cables adapted to existing civil engineering structures. These cables will, in particular, have to be modular, compact and be very easy to install and connect. The overall cost of the installed cable will have to be competitive with existing "copper" solutions.

The small size of optical fibres and the small moment of inertia resulting from this, as well as the low coefficient of expansion of silica, are the cause of its great sensitivity to mechanical and thermal stresses. In order to maintain a low level of attenuation, it is necessary to provide the fibre with an environment which isolates it with respect to these stresses.

Two main types of structures have been developed for long-haul (land and submarine) links: the loose structure and the tight structure.

The loose structure consists in arranging the fibre or fibres inside a tube or in a groove formed in a rod keeping the fibre with a slight overlength so as to prevent tensile forces or temperature rises from extending the fibre. The tubes or grooves are generally made of polymer material (having a Young's modulus of the order of 1000 to 5000 MPa and a coefficient of expansion of the order of 10-4 to 10-5 OC-l. The tubes and rods are reinforced by elements having a high modulus (generally greater than 50 GPa) and a low coefficient of expansion (of the order of 10-6 OC-l). The spaces between the fibre and the polymer material are usually filled by means of gels (yield point of the order of 10 to 60 Pa).

The tight structure consists in surrounding an individual fibre with a flexible material covered with a more rigid layer up to a thickness of approximately 900 Hm. The tight fibres are then arranged helically around a reinforcement.

In both cases, the assembly is then jacketed.

For long-haul links, the capacities are generally between 6 and 144 fibres.

The processes for manufacturing these structures include several steps.

For tube-type cables, the manufacturing process generally comprises the following steps: 1) extrusion of N tubes (having n fibres); 2) stranding them around a reinforcement; 3) intermediate jacketing; 4) peripheral reinforcement and outer jacketing.

For rod-type cables, the manufacturing process generally comprises the following steps: 1) extrusion of the rod; 2) depositing the N x n fibres; 3) intermediate jacketing or taping; 4) peripheral reinforcement and outer jacketing.

For tight-structure cables, the manufacturing process generally comprises the following steps: 1) extrusion of the flexible and rigid layers; 2) stranding around a reinforcement; 3) intermediate jacketing or taping; 4) peripheral reinforcement and outer jacketing.

For tube-type cables, rod-type cables and tightstructure cables, steps 2 and 3 are often carried out at the same time.

A single-tube structure has also been proposed in which strands of n fibres (n is generally of the order of 6) or ribbons (of 12 or 18 fibres) or microjackets are deposited. The process for manufacturing such a structure generally comprises the following steps: 1) manufacture of the strand, ribbon or microjacket; 2) depositing the fibres and extrusion of the tube; 3) reinforcement and extrusion of the outer jacket.

Although they have already been of great service, the prior known structures have various drawbacks.

In particular, the conventional cables are not very dense: generally the number of fibres per mmh is from 0.3 to 1 for line cables and of the order of 0.1 for termination cables.

Furthermore, the following points may be mentioned: - the fibres of the conventional cables often require retubing at their end as soon as they are separated out from the cable structure; - "jumper"-type or station cables very often have a poor modulus of compression, which occasionally results in mediocre thermal behaviour; - the succession of manufacturing steps and the use of generally technical special base materials lead to high costs for the cabled fibre; - the current technologies do not lend themselves well to fibre and micromodule manufacturing integration.

It will be possible to find embodiments of fibreoptic microcables in the following documents: a) "Newly developed, small-diameter optical link cord using compound glass fiber", Tatsuhiko Machida et al., International Wire & Cable Symposium Proceedings 1992, page 401, b) "Blends based on thermotropic liquid crystalline polymers (TLCP) as primary coating of optical fibers", F. Cocchini et al., International Wire & Cable Symposium Proceedings 1993, page 674, c) "Liquid crystal polymer coated fibers with thermally stable delay time characteristics", A. Sano et al., International Wire & Cable Symposium Proceedings 1993, page 680.

Moreover, the document EP-A-0,473,350 describes a module comprising an optical fibre, a primary coating which surrounds the optical fibre and a rigid secondary coating which surrounds the primary coating, in which the primary coating is preferably chosen from the group of thermoplastic materials comprising amorphous and semicrystalline materials, heat-fusible materials, hot crosslinkable materials, reactive polyurethanes, silicones, block copolymers by oils and grease-type materials, whereas the secondary coating is formed by a metal tube. The module described in this document is intended to be used in systems for guiding wire-guided vehicles, such as missiles or torpedoes. For this, the module is packaged in the form of a reel. The document EP-A-0,473,350 is essentially concerned with limiting the stresses applied to the fibre when reeling and unreeling.

In addition, in order to obtain a stable assembly, the document EP-A-0,473,350 recommends placing an adhesive coating on the outer periphery of the secondary coating.

Now, the object of the present invention is to improve the known fibre-optic cables and to improve their manufacture.

A main object of the present invention is to provide an optical module or micromodule which includes at least one self-reinforced optical fibre fulfilling the functions of a cable, designed to have low attenuation.

An important object of the invention is also to provide an optical module allowing effective decoupling between the fibre and a rigid shell formed by a microreinforcement.

Another important object of the present invention is to provide means making it possible to obtain a module or micromodule having a small transverse size, in particular having a cross-section smaller than that likely to be obtained using metallic secondary jackets, as is described, for example, in the document EP-A-0,473,350.

These objects are achieved within the scope of the present invention by virtue of a module comprising at least one optical fibre, a primary coating which surrounds the optical fibre or fibres and a rigid secondary coating forming a microreinforcement which surrounds the primary coating, characterized in that the primary coating is formed by a decoupling agent based on a thermoplastic polymer and the secondary coating is formed based on resin-coated rovings.

According to another advantageous characteristic of the present invention, the secondary coating is formed by pultrusion.

The subject of the present invention is also a process for manufacturing this module, comprising the steps which consist in: - forming a primary coating which surrounds at least one optical fibre; - forming a rigid secondary coating which forms a microreinforcement surrounding the primary coating; characterized in that the primary coating is formed by a decoupling agent based on a thermoplastic polymer and the step of forming the secondary coating consists in forming a coating based on resin and rovings.

According to another advantageous characteristic of the present invention, the secondary coating is produced by pultrusion or extrusion.

According to another advantageous characteristic of the present invention, the process furthermore comprises the step consisting in heating the thermoplastic polymer of which the primary coating is composed, after forming the latter, in order to eliminate the mechanical stresses applied to the fibre or fibres during the formation of the secondary coating.

The present invention also relates to a plant for implementing the aforementioned process.

Other characteristics, objects and advantages of the present invention will appear on reading the following detailed description, with regard to the appended drawings which are given by way of non-limiting examples and in which: - Figure 1 represents a diagrammatic crosssectional view of an optical module in accordance with one embodiment of the invention; - Figures 2, 3 and 4 represent similar crosssectional views of optical modules in accordance with three alternative forms of the present invention; - Figure 5 represents a diagrammatic view of a plant for manufacturing such a module in accordance with the present invention; and - Figure 6 represents the Young's modulus of the primary coating in accordance with the present invention, this coating being formed by a decoupling agent based on a thermoplastic polymer, as a function of temperature.

Shown in the appended Figure 1 is an optical module 10 in accordance with one embodiment of the invention, comprising a single optical fibre 12. As indicated previously, according to the invention this optical fibre 12 is surrounded by a primary coating 14, which primary coating 14 is itself surrounded by a rigid secondary coating 16 forming a microreinforcement.

According to the invention, the secondary coating 16 is formed by means of rovings and resin, preferably by pultrusion.

The primary coating 14 preferably consists of a decoupling agent based on a thermoplastic polymer.

By way of non-limiting example, the external diameter of the module 10, that is to say the external diameter of the secondary coating 16 may be of the order of 0.65 mm.

The object of the decoupling agent 14 formed, based on a thermoplastic polymer, is to allow relative movement of the fibre 12 with respect to the microreinforcement 16. The decoupling agent 14 must work throughout the life of the cable. In particular, it must make it easier to extract the fibre 12 when connecting it and must not pass on the expansions of the microreinforcement 16 to the coating of the fibre. The decoupling agent 14 must also allow slippage of the fibre 12 during polymerization shrinkage of the microreinforcement 16 in the course of the manufacturing process.

Within the scope of the present invention, the term "thermoplastic polymer" should be understood as encompassing any polymer which melts under the action of heat or, at the very least, softens or becomes sufficiently fluid to be able to be shaped. In a thermoplastic, the macromolecules are only connected together by secondary bonds; they are linear, but may be branched.

Various types of materials may be used within the scope of the invention to form the decoupling agent 14.

By way of non-limiting example, it is conceivable to use materials chosen from the following group: polyamide elastomers, polyester elastomers, acrylic elastomers, polyvinyl chloride elastomers, styrene (ethylene-butadiene)-styrene, ethylene-vinyl acetate and styrene-butadiene- styrene copolymers, uncrosslinked silicones, or any equivalent product.

Preferably, the thermoplastic polymer forming the decoupling agent 14 has the following properties: - it is quite fluid and non-adhering at the temperature of a shrinkage, which will be defined below, allowing the fibre 12 to slip and be easily extracted; nevertheless, given its small thickness (typically of the order of from 10 to 20 y), it may have a high viscosity.

A formulation having a yield point less than 200 Pa at the shrinkage temperature gives very convincing results; - it is quite viscous or solid so as not to flow over the entire range of use of the cable. In this regard, a yield point greater than 5 Pa at the shrinkage temperature seems to be satisfactory; - it has a low Young's modulus at -300C, typically a modulus less than a few tens of MPa; a typical curve produced at a vibration frequency of 1 Hz, representing Young's modulus as a function of temperature, is shown in Figure 6; - it is immiscible with the resin of the microreinforcement 16 and does not attack the coating of the fibre 12.

Of course, the present invention may form the subject of many alternative forms.

Thus, the appended Figure 2 shows an alternative form of the micromodule 10, comprising two fibres 12 surrounded by a primary coating 14 formed by a decoupling agent based on a thermoplastic polymer and by a rigid secondary coating 16 forming a microreinforcement 16.

Preferably, the decoupling agent 14 surrounds respectively each fibre 12 so that thermoplastic polymer is placed between the two adjacent fibres 12.

Figure 3 shows an alternative embodiment of a micromodule in accordance with the present invention, having N fibres 12, where N > 2, in this case N = 7.

The micromodule of Figure 3 also comprises a primary coating 14 based on a thermoplastic polymer which surrounds the fibres 12 and a rigid secondary coating forming a microreinforcement 16 which surrounds the primary coating 14. According to an alternative form of Figure 3, microjacketing 15 may be formed between the primary coating 14, based on a thermoplastic polymer, and the secondary coating 16 forming a microreinforcement.

Such microjacketing 15 may be formed, for example, by a plastic jacket having a high modulus in order to ensure geometrical limitation of the set of optical fibres 12.

The external diameter of the module of Figure 3, i.e. the external diameter of the secondary coating 16, may typically be of the order of 2 mm.

Finally, Figure 4 shows an alternative embodiment in accordance with the present invention, comprising a single optical fibre 12 surrounded by a primary coating 14 formed by a decoupling agent based on a thermoplastic polymer, a rigid secondary coating 16 forming a microreinforcement which surrounds the decoupling agent, and an external polymer jacket 18. The external diameter of the polymer jacket 18 may be typically of the order of 1 mm.

The plant and the process for manufacturing such modules in accordance with the present invention will now be described with regard to Figure 5.

This figure shows a manufacturing line 100 which comprises: - a system for supplying optical fibre(s), for example a device 110 for paying out optical fibres, enabling the tension in the fibre or fibres 12 to be adjusted; - a system 120 for coating the decoupling agent 14; - an optional system 130 for treating the decoupling agent 14 (melting, etc.); - an assembly 140 for paying out reinforcement rovings 142 which are intended to form the secondary coating 16; (these reinforcement rovings 142 may be formed, for example, from glass, carbon or aramid rovings or equivalent products); - a tank 150 for impregnating the resin associated with the reinforcement rovings 142; - a system 155 for curing this resin, formed for example by a thermal or ultraviolet oven; - a system 160 for post-treating the decoupling agent 14, advantageously formed by a continuous thermal oven; - an optional thermoplastic jacketing device 165; - a constant-speed haul-off system 170; and - a constant-tension take-up 180 designed to receive the cable thus formed.

Conventionally, the respective tensions in the fibre 12 on leaving the supply system (pay-out device) 110 on the one hand, and in the reinforcement rovings 142 on leaving the assembly 140 on the other hand, are adjusted so as to equalize the relative elongations.

The decoupling agent 14 formed by a thermoplastic polymer is coated onto the optical fibre 12 through a die built into the coating system 120. In this die, which receives the fibre 12, the decoupling agent 14 is heated to a temperature such that it is sufficiently fluid. The diameter of the die controls the thickness of the deposition of decoupling agent 14 on the periphery of the optical fibre 12.

The microreinforcement 16 is produced, preferably by pultrusion, using reinforcement rovings 142 coated with thermoplastic or thermosetting resin. By "pultrusion" is meant any operation for passing the whole assembly formed through a sizing die. As a variant, the microreinforcement 16 may also be produced by directly extruding a high-modulus thermoplastic (such as a liquidcrystal polymer, etc.) associated with rovings (for example glass, carbon or aramid rovings, or equivalent products) onto the optical fibre 12.

The distance between the tank 120 for coating the decoupling agent and the tank 150 for impregnating the resin must be great enough, depending on the rate of manufacture, for the decoupling agent 14 to have time to cool down and return to the solid state before the fibre 12 is joined to the resin-coated reinforcement rovings 142. Thus, this resin is prevented from mixing with the decoupling agent 14. Of course, this decoupling agent must be chosen so that it is prevented from being able to migrate into the impregnation resin and the jacket of the fibre 12.

The assembly formed by the fibre 12 coated with decoupling agent 14 in the unit 120, and provided with the secondary coating 16 formed by rovings impregnated with resin in the tank 150, is then directed into the resin-curing system 155, formed for example by an ultraviolet oven.

It is this curing of the secondary coating 16, associated with shrinkage of the resin, which may cause random stresses on the fibre 12 through the decoupling material 14 and which may lead to an occasionally high increase in attenuation.

Thus, according to the invention, these random stresses are removed by a thermal post-treatment, preferably in line, of the decoupling material 14 in the thermal oven 160. Remelting or reflowing of the material constituting the decoupling agent thus allows the optical fibre 12 to find its place in the carrier structure and no longer to experience stresses conventionally produced by the manufacture of the microreinforcement 16.

According to the embodiment shown in Figure 5, this thermal post-treatment station 160 consists of an oven located downstream of the microreinforcement-resin curing station 155.

However, as a variant, when the treatment temperature and time in the station 155 allows suitable post-treatment of the decoupling agent 14, the additional downstream station 160 may be dispensed with. In this case, the station for curing the resin 16 and for posttreating the decoupling agent 14 are combined in the form of a single entity composed of the thermal or ultraviolet oven 155.

An in-line extruder 165 may also jacket the micromodule and thus form, in a single operation, a microcable, which is conveyed via the constant-speed haul-off system 170 to the constant-tension take-up 180.

Such a manufacturing line may also be directly associated with a fibre-forming line.

In this case, the line for manufacturing the module preferably does not extend horizontally, as illustrated diagrammatically in Figure 5, but vertically, at the base of the fibre-forming line. The manufacturing line no longer comprises a pay-out device, as illustrated in Figure 5, but this ie replaced by the output of the fibre-forming line.

The present invention may allow use of an optical fibre 12 formed by a single core, for example a silica core of the order of 125 ym in diameter, devoid of cladding, but provided directly with the primary coating 14 based on a thermoplastic polymer, especially in the case of production directly at the output of the fibreforming line, as indicated hereinabove.

It is also possible to combine several manufacturing lines in parallel for the purpose of simultaneous assembly.

The manufacturing plant and process in accordance with the present invention make it possible to obtain a self-reinforced fibre (or an assembly of self-reinforced fibres) fulfilling the functions of a cable. Such a module may be used as it is or jacketed, by itself or in an assembly, at any point in a network, especially in the transmission, distribution or termination parts of the network.

The resin used for manufacturing the microreinforcement 16 may be chosen, in particular, from the group comprising epoxy resins, urethane acrylate resins, epoxy acrylate resins, polyester resins, vinyl ester resins, etc., the fibres or rovings 142 preferably being chosen from the group comprising glass, carbon, aramid, polymer materials, or a combination of these.

Compared to fibre-optic cables existing previously, the present invention offers the following advantages.

The present invention allows production of a secondary coating 16 having a small cross-section.

The present invention also allows production of a decoupling agent 14 having a small thickness, typically of the order of from 10 to 20 m only, i.e. approximately 10 times less than the thickness of the conventional primary coatings (of the order of from 100 to several hundreds of yam).

The present invention consequently makes it possible to obtain complete cables having a small diameter, typically of the order of 1.2 mm or less.

The present invention makes it possible to obtain a virtually zero or negligible increase in attenuation of the fibre.

The present invention makes it possible to obtain a small radius of curvature of the cable (of the order of from 10 to 15 mm compared to a conventional radius of the order of 50 mm according to the prior art) with conventional reinforcing rovings and without any special treatment.

The present invention makes it possible to obtain excellent thermal and mechanical (tensile, compressive, etc.) properties.

The present invention makes it possible to facilitate overhead installation, because of the lightness of the cable obtained, and in-duct installation, it being possible for the cable to be pushed without difficulty.

The present invention allows easy connection, since it enables the fibre to be stripped in a few seconds.

The present invention allows manufacture to be integrated with a fibre-forming line.

Finally, the present invention makes it possible to produce a cabling line at low capital cost.

Of course, the present invention is not limited to the particular embodiments which have just been described, but extends to any alternative form in accordance with its spirit.

Claims

1. Module for fibre-optic cable, comprising at least one optical fibre, a primary coating which surrounds the optical fibre or fibres and a rigid secondary coating forming a microreinforcement which surrounds the primary coating; characterized in that the primary coating is formed by a decoupling agent based on a thermoplastic polymer and the secondary coating is formed based on rovings coated with resin.

2. Module according to Claim 1, characterized in that the secondary coating is produced by pultrusion.

3. Module according to Claim 1, characterized in that the secondary coating is produced by extrusion.

4. Module according to one of Claims 1 to 3, characterized in that the rovings are chosen from the group comprising glass, carbon, aramid, polymer materials, or a combination of these.

5. Module according to one of Claims 1 to 4, characterized in that the resin of the secondary coating is chosen from the group comprising epoxy resins, urethane acrylate resins, epoxy acrylate resins, polyester resins and vinyl ester resins.

6. Module according to one of Claims 1 to 5, characterized in that the decoupling agent based on a thermoplastic polymer is adapted so as to allow relative movement of the fibre with respect to the microreinforcement throughout the life of the cable.

7. Module according to one of Claims 1 to 6, characterized in that the thermoplastic polymer of which the primary coating is composed is chosen from the group comprising: polyamide elastomers, polyester elastomers, acrylic elastomers, polyvinyl chloride elastomers, styrene-(ethylene-butadiene)-styrene, ethylene-vinyl acetate and styrene-butadiene-styrene copolymers, uncrosslinked silicones and equivalent products.

8. Module according to one of Claims 1 to 7, characterized in that the thermoplastic polymer of which the decoupling agent is composed is quite fluid and/or non-adhering at a shrinkage temperature in order to allow the fibre to slip and to be easily extracted.

9. Module according to one of Claims 1 to 8, characterized in that the thermoplastic polymer of which the decoupling agent is composed has a yield point less than 200 Pa at a shrinkage temperature.

10. Module according to one of Claims 1 to 9, characterized in that the thermoplastic polymer has a yield point greater than 5 Pa.

11. Module according to one of Claims 1 to 10, characterized in that the thermoplastic polymer of which the decoupling agent is composed has a Young's modulus less than a few tens of MPa at a temperature of minus 30 C.

12. Modulus according to one of Claims 1 to 11, characterized in that the thermoplastic polymer of which the decoupling agent is composed is immiscible with the resin of the microreinforcement and does not attack the coating of the fibre.

13. Module according to one of Claims 1 to 12, characterized in that it comprises several fibres surrounded with the primary coating.

14. Module according to Claim 13, characterized in that the thermoplastic polymer forming the decoupling agent surrounds each optical fibre.

15. Module according to one of Claims 1 to 14, characterized in that a microjacketing surrounds the primary coating.

16. Module according to one of Claims 1 to 15, characterized in that a polymer jacket surrounds the secondary coating.

17. Module according to Claim 3, characterized in that the secondary coating is formed by directly extruding a high-modulus thermoplastic, such as liquidcrystal polymer.

18. Module according to one of Claims 1 to 17, characterized in that the primary coating has a thickness of the order of from 10 to 20 ym.

19. Process for manufacturing a module in accordance with one of Claims 1 to 18, characterized in that it comprises the steps consisting in: - forming a primary coating which surrounds at least one optical fibre.

- forming a rigid secondary coating forming a microreinforcement which surrounds the primary coating; characterized in that the primary coating is formed by a decoupling agent based on a thermoplastic polymer and the step of forming the secondary coating consists in forming a coating based on resin and rovings.

20. Process according to Claim 19, characterized in that the secondary coating is produced by pultrusion.

21. Process according to Claim 20, characterized in that the pultrusion step consists in drawing, through a sizing die, the assembly consisting of the optical fibre provided with the primary coating which is itself surrounded by the resin-coated rovings, in order to form the secondary coating.

22. Process according to Claim 19, characterized in that the secondary coating is produced by extrusion, preferably by directly extruding a high-modulus thermoplastic, such as a liquid-crystal polymer, associated with rovings.

23. Process according to one of Claims 19 to 22, characterized in that it furthermore comprises the step of curing, preferably hot and/or by exposure to ultraviolet, of the resin making up the secondary coating.

24. Process according to one of Claims 19 to 23, characterized in that: - the process furthermore comprises the step consisting in heating the thermoplastic polymer of which the primary coating is composed, after forming the latter, in order to remove the mechanical stresses applied to the optical fibre or fibres during the formation of the secondary coating.

25, Process according to Claim 24, characterized in that the step of heating the thermoplastic polymer of which the primary coating is composed, after forming the latter, is carried out after the module has passed through a unit for curing the resin of which the secondary coating is composed.

26. Process according to Claim 24, characterized in that the step of heating the thermoplastic polymer of which the primary coating is composed, after forming the latter, is carried out during a step for curing the resin of the secondary coating.

27. Process according to one of Claims 24 to 26, characterized in that the distance separating the unit for coating the thermoplastic polymer forming the primary coating from a tank for impregnating the resin forming the secondary coating is great enough for the decoupling agent to have time to cool down and to return to the solid state before the fibre is joined to reinforcement rovings coated with the resin forming the secondary coating.

28. Plant for implementing the process in accordance with one of Claims 19 to 27, characterized in that it comprises: - a system for supplying optical fibre(s); - a system for coating a decoupling agent (14) based on a thermoplastic polymer onto the optical fibre; - an assembly for paying out reinforcement rovings; - a tank for impregnating resin associated with the reinforcement rovings; - a system for curing this resin; - a system for post-treating the decoupling agent; - a constant-speed haul-off system; and - a constant-tension take-up.

29. Plant according to Claim 28, characterized in that it furthermore comprises a system for pretreating the decoupling agent before producing the secondary coating.

30. Plant according to either of Claims 28 and 29, characterized in that it furthermore comprises a thermoplastic jacketing device downstream of the station for post-treating the decoupling agent.

31. Plant according to one of Claims 28 to 30, characterized in that the system for curing the resin associated with the reinforcement rovings and the system for post-treating the decoupling agent are formed by a single entity.

32. Plant according to one of Claims 28 to 31, characterized in that the system for supplying optical fibres is formed by a fibre-forming line.

33. Plant according to one of Claims 28 to 31, characterized in that the system for supplying optical fibres is formed by a pay-out device adapted to allow the tension in each fibre to be adjusted.

34. Module for fibre-optic cable, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.