FR2728694A1 - MODULE FOR FIBER OPTIC CABLES, METHOD OF MANUFACTURING AND INSTALLATION THEREFOR - Google Patents

Abstract

The present invention relates to a fiber optic cable module comprising at least one optical fiber (12), a primary coating (14) which surrounds the optical fiber (s) and a rigid secondary coating (16) forming a microcarrier, which surrounds the primary coating. (14), characterized in that the secondary coating (16) is formed from wicks coated with resin.

Description

The present invention relates to the field of fiber optic cables, in

  especially cables for subscriber distribution networks. Future fiber optic distribution networks will have to be built using cables suitable for existing civil engineering. These cables must, in particular, be modular, compact, and have great ease of installation and connection. The overall cost of the cable installed should be competitive with existing "copper" solutions. The small size of the optical fibers and the resulting reduced moment of inertia, as well as the low expansion coefficient of the silica are at the origin of its great sensitivity to mechanical and thermal aggressions. In order to maintain a low level of attenuation, it is necessary to provide the fiber with an environment which isolates it from

these assaults.

  Two main types of structures have been developed for long-distance connections (land and submarine): the structure

free and tight structure.

  The free structure consists in placing the fiber (s) inside a tube or a groove formed in a rod, keeping the fiber slightly longer to avoid tensile forces or temperature increases do not put the fiber in extension. The tubes or grooves are generally made of polymer material (Young's modulus of the order of 1000 to 500N0MPa; coefficient of expansion of the order of 10-4 to 10-5sC-1. These tubes and rods are reinforced by elements with high modulus (generally greater than 50GPa) and low coefficient of expansion (of the order of 10-6 C-1). The spaces between the fiber and the polymer material are most often filled with gels

  (flow threshold of the order of 10 to 60 Pa).

  The tight structure consists of surrounding the individual fiber with a flexible material covered with a more rigid layer up to a thickness of approximately 900 μm. The tight fibers are then placed

  helically around a reinforcement.

  In both cases, the assembly is then sheathed.

  For long distance links, the capacities are

  generally between 6 and 144 fibers.

  The manufacturing processes for these structures include

many stages.

  For tube cables, the manufacturing process generally includes the following steps: 1) extrusion of the N tubes (with n fibers), 2) assembly of these around a reinforcement, 3) intermediate sheathing,

  4) peripheral reinforcement and external sheathing.

  For rod cables, the manufacturing process generally includes the following steps 1) extrusion of the rod, 2) deposition of N. xn fibers, 3) sheathing or intermediate tape,

  4) peripheral reinforcement and external sheathing.

  For cables with a tight structure, the manufacturing process generally comprises the following steps 1) extrusion of the flexible and rigid layers, 2) assembly around a reinforcement, 3) sheathing or intermediate tape,

  4) peripheral reinforcement and external sheathing.

  For tube cables, rod cables and structure cables

  tight, phases 2 and 3 are often carried out simultaneously.

  A single-tube structure has also been proposed in which strands of n fibers (generally n of the order of 6) or ribbons (of 12 or 18 fibers) or microgains are deposited. The manufacturing process for such a structure generally comprises the following steps 1) manufacturing the strand, ribbon or microgaine, 2) depositing the fibers and extruding the tube,

  3) reinforcement and extrusion of the outer sheath.

  Although they have already rendered great services, the structures

  prior art has various drawbacks.

  In particular, conventional cables are not very dense generally from 0.3 to 1 fiber per mm2 for line cables and

  about 0.1 fiber per mm2 for termination cables.

  In addition, the following points may be mentioned: - the fibers of conventional cables often require re-tying at the end as soon as they are detached from the cable structure, - cables of the "garter" or station type very often have a bad module compression, which results in a sometimes poor thermal behavior, - the succession of manufacturing steps and the use of generally technical basic materials induce high costs for the wired fiber, current technologies are not suitable for integration of manufacturing

fibers and micromodules.

  Examples of the realization of optical fiber microcables can be found 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) uBlends based on thermotropic liquid crystalline polymers (TLCP) as primary coating of optical fibers ", F. Cocchini et ai., International Wire & Cable Symposium Proceedings 1993, page 674, c)" Liquid crystal polymer coated fibers with thermally stable delay time characteristics ", A. Sano et ai., International Wire & Cable Symposium

Proceedings 1993, page 680.

  Furthermore, the document EP-A-0 473 350 describes a module comprising an optical fiber, a primary coating which surrounds the optical fiber and a rigid secondary coating which surrounds the primary coating, in which the primary coating is preferably chosen from the family. thermoplastic materials including amorphous and semi-crystalline materials, hot melt materials, hot crosslinkable materials, reactive polyurethanes, silicones, oil block copolymers and grease-like materials, while the secondary coating is formed of 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 coil. The document EP-A-0 473 350 is essentially concerned with limiting the stresses applied to the fiber during winding and unwinding. In addition to obtain a stable assembly, the document EP-A-0 473 350 recommends placing an adhesive coating on the periphery

  exterior of secondary coating.

  The present invention now aims to improve

  known fiber optic cables and improve their manufacture.

  A main aim of the present invention is to propose an optical module or micromodule comprising at least one self-reinforced optical fiber fulfilling the functions of a cable, adapted to present

reduced attenuation.

  An important aim of the invention is also to propose an optical module allowing efficient decoupling between the fiber and a

  rigid shell formed of a micro-reinforcement.

  Another important object of the present invention is to propose means making it possible to obtain a module or micromodule of small transverse dimension, in particular of smaller section than that which can be obtained with metallic secondary sheaths, such as

  described for example in document EP-A-0 473 350.

  These aims are achieved in the context of the present invention, thanks to a module comprising at least one optical fiber, a primary coating which surrounds the optical fiber (s) and a rigid secondary coating forming a microcarrier, which surrounds the primary coating, characterized in that the secondary coating is formed on the basis of

resin coated wicks.

  According to another advantageous characteristic of the present

  invention, the secondary coating is formed by pultrusion.

  According to another advantageous characteristic of the present invention, the primary coating is formed of a decoupling agent with

thermoplastic polymer base.

  The present invention also relates to a method for manufacturing this module comprising the steps which consist in: - forming a primary coating which surrounds at least one optical fiber, - forming a rigid secondary coating forming a microcarrier which surrounds the primary coating, characterized by the fact that the secondary coating formation step

  consists in making a coating based on wicks coated with resin.

  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 primary coating is formed of a decoupling agent based on a thermoplastic polymer, and the method further comprises the step of heating the thermoplastic polymer making up the primary coating, after formation of this, to remove the mechanical stresses applied to the fiber (s) during the formation

secondary coating.

  The present invention also relates to an installation

  for the implementation of the above method.

  Other features, purposes and advantages of this

  invention will appear on reading the detailed description which will

  follow, and with reference to the appended drawings given by way of nonlimiting examples and in which: - FIG. 1 represents a schematic view in transverse section of an optical module according to an embodiment of the invention, - the figures 2, 3 and 4 show views in similar cross section of optical modules according to three variants of the present invention, and - Figure 5 shows a schematic view of an installation of

  manufacture of such a module according to the present invention.

  There is shown in Figure 1 attached, an optical module 10 according to a variant of the invention comprising a single optical fiber 12. As indicated above, according to the invention, this optical fiber 12 is surrounded by a primary coating 14, which primary coating 14 is itself surrounded by a secondary coating

rigid 16 forming a microcarrier.

  According to the invention, the secondary coating 16 is formed using

  wicks and resin, preferably by pultrusion.

  The primary coating 14 preferably consists of a

  decoupling agent based on thermoplastic polymer.

  By way of nonlimiting example, the outside diameter of the module, that is to say the outside diameter of the secondary coating 16 can be of the order of 0.65 mm. The purpose of the decoupling agent 14 formed on the basis of a thermoplastic polymer is to allow the relative movement of the fiber 12 relative to the microcarrier 16. The decoupling agent 14 must intervene throughout the life of the cable. It must in particular facilitate the extraction of the fiber 12 during the connection and not pass on the expansions of the microcarrier 16 on the coating of the fiber. The decoupling agent 14 must also allow the fiber 12 to slip during the polymerization withdrawal from the microcarrier 16 during the manufacturing process. In the context of the present invention, the expression "thermoplastic polymer" should be understood to include any polymer which under the action of heat melts or, at least, softens or fluidizes sufficiently to be able to be shaped. In a thermoplastic material, the macromolecules are only interconnected by

  secondary links; they are linear but can be branched.

  Various types of materials can be used, as part

  of the invention, to form the decoupling agent 14.

  By way of nonlimiting example, it is possible to envisage using the materials chosen from the following group: polyamide-elastomers,

  polyester-elastomers, acrylic-elastomers, polyvinyl chloride

  elastomers, styrene ethylene butadiene styrene, ethylen vinyl acetate, styrene butadiene styrene, non-crosslinked silicone, or any equivalent product. Preferably, the thermoplastic polymer forming the decoupling agent 14 has the following properties - it is fairly fluid and not adherent at the temperature of a reprocessing which will be defined below, to allow the fiber 12 to slide and its easy extraction; nevertheless, given its small thickness (typically of the order of 10 to 20v), it can have a high viscosity. A formulation having a flow threshold below 200 Pa at the reprocessing temperature gives very convincing results; - it is viscous or solid enough not to flow over the entire range of use of the cable. On this point, a flow threshold greater than 5 Pa at room temperature seems satisfactory; - It has a low Young's modulus at -30 ° C, typically a modulus less than a few tens of MNIPa; - It is immiscible with the resin of microcarrier 16 and non-aggressive towards

fiber coating screw 12.

  Of course, the present invention can be the subject of

many variations.

  There is thus shown in Figure 2 attached, a variant of micromodule 10 comprising two fibers 12 surrounded by a primary coating 14 formed of a decoupling agent based on thermoplastic polymer and a rigid secondary coating 16 forming microcarrier. Preferably, the decoupling agent 14 respectively surrounds each fiber 12, so that polymer

  thermoplastic is placed between the two adjacent fibers 12.

  FIG. 3 shows an alternative embodiment of a micromodule according to the present invention with N fibers 12, with N> 2, in

the species N = 7.

  The micromodule of FIG. 3 also comprises a primary coating 14 based on a thermoplastic polymer which surrounds the fibers 12 and a rigid secondary coating forming a microcarrier 16 which surrounds the primary coating 14. According to a variant of FIG. 3, a micro-sheath 15 can be formed between the primary coating 14 based on a thermoplastic polymer and the secondary coating 16 forming a micro-reinforcement. Such micro-sheathing 15 can be formed for example of a plastic sheathing having a high modulus to ensure a

  geometric limitation of all optical fibers 12.

  The outside diameter of the module in FIG. 3, ie the outside diameter of the secondary coating 16 can typically be of the order of 2mm. Finally, FIG. 4 shows a variant embodiment in accordance with the present invention comprising a single optical fiber 12 surrounded by a primary coating 14 formed from a decoupling agent based on a thermoplastic polymer, a rigid secondary coating 16 forming microrenfort which surrounds the decoupling agent, and an external polymeric sheathing 18. The external diameter of the polymeric sheathing 18 can typically be of the order of 1 mm. We will now describe the installation and the method for manufacturing such modules according to the present invention, with reference to

in Figure 5.

  In this figure, a manufacturing line 100 has been shown which comprises: - a system for supplying optical fiber (s), for example an unwinder 110 of optical fibers, making it possible to adjust the tension of the one or more fibers 12, - a system 120 for coating the decoupling agent 14, - a possible system 130 for treating the decoupling agent 14 (fusion, etc.), - an assembly 140 for unwinding reinforcing wicks 142 intended to form the secondary coating 16; (these reinforcing wicks 142 can be formed for example of glass, carbon, aramid or equivalent products), - a tank 150 for impregnating resin associated with the reinforcing wicks 142 - a system 155 for curing this resin, formed for example a thermal or ultra-violet oven, - a system 160 for post-treatment of the decoupling agent 14, advantageously formed by a scrolling thermal oven, - a possible thermoplastic sheather 165, - a speed drawing system constant 170, and - a constant tension reel 180 designed to receive the cable thus formed. Conventionally, the respective tensions of the fiber 12 at the outlet from the supply system (unwinder) 110 on the one hand, and reinforcing locks 142 at the outlet of the assembly 140 on the other hand, are

  adjusted to equalize the relative elongations.

  The decoupling agent 14 formed from a thermoplastic polymer is coated on the optical fiber 12 through a die integrated into the coating system 120. In this die, which receives the fiber 12, the decoupling agent 14 is heated to a temperature such that it is sufficiently fluid. The diameter of the die regulates the thickness of the deposit of

  the decoupling agent 14 on the periphery of the optical fiber 12.

  The microcarrier 16 is produced, preferably by pultrusion, using reinforcing wicks 142 coated with thermoplastic or thermosetting resin. By "pultrusion" means any operation of passing the assembly formed through a calibration die. As a variant, the microcarrier 16 can also be produced by direct extrusion of a high modulus thermoplastic material (such as a liquid crystal polymer, etc.) associated with wicks (for example glass, carbon, aramid

  or equivalent products) on optical fiber 12.

  The distance between the coating tank 120 of the decoupling agent and the resin impregnation tank 150 must be sufficient, depending on the manufacturing speed, so that the decoupling agent 14 has time to cool and return to the solid state before the fiber 12 is assembled with the reinforcing wicks 142 coated with resin. This prevents this resin from mixing with the decoupling agent 14. Of course, this decoupling agent must be chosen to prevent it from

  can migrate into the impregnation resin and the sheath of the fiber 12.

  The assembly formed of the fiber 12 coated with decoupling agent 14 in the station 120 and provided with the secondary coating 16 formed of wicks impregnated with resin in the tank 150 is then directed into the resin hardening system 155 formed for example of an ultra violet oven. It is this hardening of the secondary coating 16, linked to a shrinkage of the resin, which can cause random stresses on the fiber 12 through the decoupling material 14 and which can cause a

  sometimes high attenuation increase.

  Thus, according to the invention, these random constraints are eliminated by a thermal post-treatment, and preferably in line, of the decoupling material 14, in the thermal oven 160. The reflow or refluidification of the material constituting the decoupling agent allows thus the optical fiber 12 to find its place in the supporting structure and no longer to undergo stresses conventionally brought about by manufacturing

microrenforcement 16.

  According to the embodiment shown in Figure 5, this heat post-treatment station 160 consists of an oven arranged

  downstream of the curing station 155 of the microrefort resin.

  However, as a variant, when the temperature and the treatment time in the station 155 allow adequate post-treatment of the decoupling agent 14, the additional downstream station 160 can be omitted. In this case, the resin hardening station 16 and the post-treatment of the decoupling agent 14 are combined in the form of a

  single entity composed by the thermal or ultra-violet oven 155.

  An in-line extruder 165 can make it possible to sheath the micromodule and thus to constitute in a single operation a microcable, which is directed via the speed drawing system

  constant 170 on the reel 180 at constant tension.

  Such a production line can also be associated

  directly to a fiber line.

  In this case, preferably, the module production line does not extend horizontally as illustrated diagrammatically in FIG. 5, but vertically, at the base of the fiberizing line. The chain no longer includes an unwinder, as illustrated in FIG. 5, but this

  the latter is replaced by the output from the fiber line.

  The present invention can allow the use of an optical fiber 12 formed of a single core, for example a silica core of the order of 125 im in diameter, devoid of sheath, but provided directly with the primary coating 14 based on polymer. thermoplastic, especially in the case of preparation directly at the outlet of the

  fibering line as indicated above.

  We can also associate several production lines in

  parallel for simultaneous assembly.

  The installation and the manufacturing method in accordance with the present invention make it possible to obtain a self-reinforced fiber (or assembly of fibers) fulfilling the functions of a cable. Such a module can be used as it is or sheathed, alone or assembled and at any point on a network, in particular in the transport parts,

  distribution or termination of the network.

  il The resin used for the manufacture of microrenfort 16 can be chosen in particular from the group comprising epoxy resins, urethane acrylate, epoxy acrylate, polyester, vinylester ... the fibers or wicks 142 preferably being chosen from the group comprising glass , carbon, aramid, polymeric materials, or a combination

of these.

  Compared to existing fiber optic cables

  previously, the present invention provides the following advantages.

  The present invention allows the production of a coating

secondary 16 of small section.

  The present invention also allows the production of a decoupling agent 14 of small thickness, typically of the order of 10 to Stm only, that is to say approximately 10 times thinner than the thickness of conventional primary coatings (of the order of 100 to several hundred

from im).

  The present invention therefore makes it possible to obtain complete cables of small diameter, typically of the order of 1.2 mm or less. The present invention provides an increase

  almost zero or negligible fiber attenuation.

  The present invention makes it possible to obtain a reduced radius of curvature of the cable (of the order of 10 to 15mm for a conventional radius of the order of O50mm depending on the state of the art) with reinforcing wicks.

  classic and without special treatment.

  The present invention provides excellent

  thermal and mechanical behaviors (traction, compression ...).

  The present invention makes it easier to install overhead due to the lightness of the cable obtained and in the pipe, the cable

  can be pushed without difficulty.

  The present invention allows easy connection,

  since it allows stripping of the fiber in a few seconds.

  The present invention allows integrated manufacturing on a

fiber line.

  Finally, the present invention makes it possible to produce a line of

  wiring at low investment cost.

  Of course, the present invention is not limited to the particular embodiments which have just been described but extends to any

variant according to his spirit.

Claims (33)

  1. Module for optical fiber cable comprising at least one optical fiber (12), a primary coating (14) which surrounds the optical fiber or fibers and a rigid secondary coating (16) forming a microcarrier, which surrounds the primary coating (14) , characterized in that the secondary coating (16) is formed on the basis   wicks (142) coated (150) with resin.   2. Module according to claim 1, characterized in that the   secondary coating (16) is produced by pultrusion.   3. Module according to claim 1, characterized in that the   secondary coating (16) is produced by extrusion.   4. Module according to one of claims 1 to 3, characterized by   the fact that the wicks are chosen from the group comprising glass,   carbon, aramid, polymeric materials, or a combination thereof this.   5. Module according to one of claims 1 to 4, characterized by   the fact that the resin for the secondary coating (16) is chosen from the group comprising epoxy, urethane acrylate, epoxy acrylate resins, polyester, vinylester.   6. Module according to one of claims 1 to 5 characterized by the   the primary coating (14) is formed of a decoupling agent thermoplastic polymer base.   7. Module according to claim 6, characterized in that the decoupling agent (14) based on thermoplastic polymer is adapted to allow relative movement of the fiber (12) relative to the   microcarrier (16) during the life of the cable.   8. Module according to one of claims 6 or 7, characterized by   the fact that the thermoplastic polymer making up the primary coating (14) is chosen from the group comprising: polyamide-elastomers, polyester-elastomers, acrylic-elastomers, polyvinyl elastomers, styrene ethylene butadiene styrene, ethylene vinyl acetate, styrene butadiene styrene, uncrosslinked silicone, and equivalent products.   9. Module according to one of claims 6 to 8, characterized by the   the thermoplastic polymer composing the decoupling agent (14) is fairly fluid and / or not adherent at a reprocessing temperature   to allow sliding of the fiber (12) and its easy extraction.   10. Module according to one of claims 6 to 9, characterized by   the fact that the thermoplastic polymer composing the decoupling agent (14) has a flow threshold below 200 Pa at a temperature reprocessing.   11. Niodule according to one of claims 6 to 10, characterized by   the fact that the thermoplastic polymer (14) has a threshold flow greater than 5 Pa.   12. Module according to one of claims 6 to 11, characterized by   the fact that the thermoplastic polymer making up the decoupling agent (14) has a Young's modulus of less than a few tens of MNIPa at a temperature of minus 30'C.   13. Module according to one of claims 6 to 12, characterized by   the fact that the thermoplastic polymer composing the decoupling agent (14) is immiscible with the resin of the microcarrier (16) and non-aggressive towards   fiber coating screw (12).   -0 14. Module according to one of claims 6 to 13, characterized by   the fact that it comprises several fibers (12) surrounded by the coating primary (14).   15. Module according to claim 14, characterized in that the thermoplastic polymer forming a decoupling agent (14) surrounds each optical fiber (12).   16. NModule according to one of claims 1 to 15, characterized by   the fact that a micro-sheathing (15) surrounds the primary coating (14).   17. NIodule according to one of claims 1 to 16, characterized by   the fact that a polymer cladding (18) surrounds the secondary coating (16).   18. NModule according to claim 3, characterized in that the secondary coating (16) is formed by direct extrusion of a high modulus thermoplastic material, such as a liquid crystal polymer. 19. Method of manufacturing a module in accordance with one of the   Claims 1 to 18, characterized in that it comprises the steps which   consist in: - forming a primary coating (14) which surrounds at least one optical fiber (12), - forming a rigid secondary coating (16) forming a microcarrier which surrounds the primary coating (14), characterized in that the step secondary coating formation   (16) consists in forming a coating based on resin and wicks.   20. Method according to claim 19, characterized in that   that the secondary coating (16) is produced by pultrusion.   21. The method of claim 20, characterized in that the pultrusion step consists in pulling the assembly constituted by the optical fiber (12) provided with the primary coating (14) itself surrounded by the wicks (142) coated with resin to form the secondary coating   (16), through a calibration process.   22. Method according to claim 19, characterized in that the secondary coating (16) is produced by extrusion, preferably by direct extrusion of a high modulus thermoplastic material, such as   than a liquid crystal polymer, combined with wicks.   23. Method according to one of claims 19 to 22, characterized   by the fact that it further comprises the step of hardening, preferably hot and / or by exposure to ultraviolet, of the resin composing the secondary coating (16).   24. Method according to one of claims 19 to 23, characterized   by the fact that: - the primary coating (14) is formed from a decoupling agent based on a thermoplastic polymer, and by the fact that - the method further comprises the step of heating the thermoplastic polymer making up the primary coating (14), after formation thereof, to remove the mechanical stresses applied to the optical fiber or fibers (12) during the formation of the secondary coating (16). 25. The method of claim 24, characterized in that the step of heating the thermoplastic polymer (14) composing the primary coating, after formation thereof, is carried out after passage of the module in a curing station (155) resin   making up the secondary coating (16).   26. The method of claim 24, characterized in that the step of heating the thermoplastic polymer composing the primary coating (14), after formation thereof, is carried out during a curing step (155) of coating resin secondary (16).   27. Method according to one of claims 24 to 26, characterized   in that the distance separating a station (120) for coating the thermoplastic polymer forming the primary coating (14) and a tank (150) for impregnating the resin forming the secondary coating (16) is sufficient for the agent decoupling (14) has time to cool and return to the solid state before the fiber (12) is assembled with reinforcing wicks (142) coated with resin forming the coating secondary (16).   28. Installation for implementing the process in accordance with   one of claims 19 to 27, characterized in that it comprises   - a supply system (110) of optical fiber (s) (12), - a system (120) of coating a decoupling agent (14) based on thermoplastic polymer on the optical fiber ( 12), - a reeling unit (140) of reinforcing wicks, - a tank (150) of resin impregnation associated with the reinforcing wicks (142),   - a system (155) for curing this resin, - a system (160) for post-treatment of the decoupling agent (14), - a system (170) for drawing at constant speed, and   - a reel (180) at constant tension.   29. Installation according to claim 28, characterized in that it further comprises a system (130) for pre-treatment of the decoupling agent (14) before production of the secondary coating (16).   30. Installation according to one of claims 28 or 29,   characterized by the fact that it further comprises a thermoplastic sheath (165) downstream of the post-treatment station (160) of the decoupling agent (14).   31. Installation according to one of claims 28 to 30,   characterized by the fact that the resin hardening system (155) associated with the reinforcing wicks (142) and the post-treatment system of   the decoupling agent (14) are formed of a single entity.   32. Installation according to one of claims 28 to 31,   characterized by the fact that the fiber supply system (s)   optic (s) (110) is formed by a fiber line.   33. Installation according to one of claims 28 to 31,   characterized by the fact that the system for supplying optical fiber (s) (110) is formed by an unwinder adapted to allow adjustment the tension of each fiber.