FR2541782A1 - METHOD FOR MANUFACTURING OPTICAL FIBER CABLE - Google Patents

Abstract

THE INVENTION CONCERNS OPTICAL TELECOMMUNICATIONS. THE INVENTION DESCRIBES AN UNDERWATER TELECOMMUNICATIONS CABLE 10 CONTAINING OPTICAL FIBERS AND A METHOD FOR MAKING SUCH A CABLE. THE PROCESS INCLUDES IN PARTICULAR THE OPERATIONS WHICH CONSIST OF COATING THE CORE 12 OF THE CABLE WITH AN ADHESIVE 25, WINDING ONE OR MORE LAYERS OF STEEL WIRE 13 ON THE ADHESIVE, FORMING A CONDUCTIVE TUBE 14 AROUND THE LAYERS OF WIRE D 'STEEL, AND TO RETRACT THE TUBE 14 ON THE LAYER OF STEEL WIRES. THE CABLE IS MANUFACTURED SO THAT THE OPTICAL ATTENUATION OF THE FIBERS VARIES SLIGHTLY DUE TO VARIATIONS IN CABLE DEFORMATION. APPLICATION TO UNDERWATER TELECOMMUNICATION CABLES.

Description

The present invention relates to a telecommunication cable

  underwater communications containing fiber optics and a

  method of manufacturing such a telecommunications cable.

  Coaxial Submarine Telecommunication Cables for Analog Telecommunication Systems - These cables have been manufactured to support a number of environmental factors

  obvious, such as low temperature,

  high pressure and the presence of corrosive water Submarine cables were further fabricated to withstand the high tensile and flexural forces which

  appear during laying and recovery operations.

cables.

  Recent progress in the field of techno-

  Fiber optic telecommunications have led to practical optical fiber telecommunication systems The characteristics of these systems, such as digital format, wide bandwidth and wide repeater spacing, result in a relatively low cost per kilometer of channel This low potential cost means that a submarine telecommunications cable containing optical fibers is an interesting alternative for coaxial telecommunications cables

current analog -

  A submarine cable containing optical fibers has been described previously in US Pat. No. 4,156,104. Such a cable comprises stranded steel wires separated from a central filament by a core in which the fibers are embedded. A problem arises in the manufacture of a cable containing optical fibers for use in a submarine telecommunications system The measured attenuation of the optical fibers incorporated in the cable depends on the deformation of the cable Any high fluctuation of the deformation of the cable cable during manufacture, installation, or operation of the cable system complicates the process of commissioning, aligning, and operating the system

submarine telecommunications.

  This problem is solved by manufacturing a fiber optic cable by the following operations.

  an adhesive a cable core containing optical fibers.

  A layer of steel wire is wound around the adhesive on the core of the cable. A conductive metal tube is formed on the layer of steel wire. The tube is shrunk on the layer.

of steel wire.

  The invention will be better understood when reading the

  detailed description which follows of an embodiment

  and with reference to the accompanying drawings in which: Figure 1 is a sectional view of an embodiment

  a telecommunications cable containing fiber optics

  c; FIG. 2 is an enlarged section of a core of the cable of FIG. 1 FIG. 3 is an enlarged section of the core of FIG.

  parts of certain reinforcing elements of the cable of FIG.

  Figure 4 is a schematic side elevational representation of a manufacturing line for an optical fiber cable for telecommunications; and

  Figure 5 is a graph showing a comparison

  reason between the optical attenuation in fibers of a

  cable manufactured in accordance with a process of the prior art

  in fiber from another cable, manufactured in accordance with

  according to the process described, depending on the two cases of

  the strain of tension in the cable.

  FIG. 1, which shows a section 10 of a submarine telecommunications cable containing optical fibers intended for the transmission of optical signals. The cable comprises a core 12, a steel strand 13 and a cylindrical conductor 14. , and an envelope

insulating and protective 16.

  As shown in FIG. 2, the core 12 of the cable

  takes an elongate central reinforcing element, or central carrier

  tral, 18, optical fibers 20 embedded in an elastomer 22, and a polymer sheath 23 surrounding the elastomer. The elongate central reinforcing element, or central carrier 18, shown in FIG. 2, is a central wire of circular cross-section which gives mechanical strength to the core 12 during the core manufacturing processes and or cable Characteristic use is made of high-strength copper-clad steel The center wire has a characteristic diameter of 0.8 mm The minimum size

  of the cross-section of the central carrier 18 is determined

  due to the tensile and bending forces required for the cable manufacturing process During the core cable manufacturing process, the central carrier is used as the main reinforcing element The core is fabricated in two During each operation, the central wearer is used to pull the growing soul through various equipment, while materials are

  added step by step After the manufacture of the soul, we manufacture

  than the cable by two additional operations.

  After the cable has been completely fabricated, and during the laying of the fiber telecommunications system and its use at the seabed, the core wire 18 acts as the center conductor of a coaxial cable structure which is used to low frequency transmission

  monitoring, maintenance and control information.

  Due to the coaxial central conductor function,

  chooses the central carrier so that it has a conductivity

  at least 40% of the conductivity of a copper wire

electrolytic of the same size.

  In another configuration intended for use

  in a terrestrial telecommunications system that does not use

  not the signaling function and operating at ambient temperatures that vary in a much

  more extensive than sea temperatures, it is possible to

  the elongated central reinforcement element from high mechanical strength glass, particularly in the form of a high strength glass fiber bundle

  embedded in a polymer such as epoxide or polyester.

  The elastomer 22 is a coating material of

  fiber optics, such as a thermoplastic polyester of

  extrusion machine, which is supplied under the HYTREL brand name

  E I of the Pont de Nemours and Co, and it is applied to

  The detailed information describing the HYTREL family of polyesters can be found in the following documents Rubber Age, 104, 3, pages 35-42 (1972); Proceedings of the International Wire and Cable Symposium, pp. 292-299 (1975); and Polymer Engineering and Science, Vol 14, No. 12, pages 848-852 (December 1974) The thermoplastic elastomer completely coats several separate optical fibers, to protect them inside the steel strand, near the center of the cable. this configuration, the fibers are placed near the neutral bending axis of the cable When the cable is put into operation, the pressure that exists at the bottom of the sea

  is applied to the cable essentially symmetrically.

  The steel strand configuration is designed to withstand the seabed pressure with very little deformation. Because the elastomer completely surrounds each fiber inside the core, it forms a layer

  buffer that isolates each fiber from local loads

  residual residues that can result from the pressure of the seabed. This minimizes the microbending of the fibers and

  the associated optical attenuation produced by such a micro-

  curvature, with regard to the effects of the pressure of the

bottom of the sea.

  In the first operation of making the soul,

  the central carrier 18 is unwound from a reel

  trice, with speed and tension that can be controlled.

  It is straightened, cleaned in trichloroethane and

  the heating is applied Two layers of thermoelastomer

  plastic 22 on the warm central carrier is extruded directly

  on the hot central carrier a first layer of the elastomer, in a plastic state is deposited in a helix on the first layer of the elastomer a number

  predetermined, for example six to twelve, glass fibers.

  A second layer of the elastomer is also extruded in an amorphous state. However, this second layer is extruded on the first layer of the elastomer and on the glass fibers. The second layer of elastomer is joined to the first layer between the layers. fibers, so as to completely surround

  each of the fibers with the elastomer -

  The first manufacturing operation of the core is completed by passing the partially completed core in a water bath to cool it, before winding it on a

receiver coil.

  In the second core fabrication operation, the outer surface of the elastomer is covered by the protective nylon sheath 23. One type of nylon used for the sheath is Zytel 153 L NC 10, which is a 6/12 nylon. which is provided by EI du Pont de Nemours and Co This sheath has a relatively high melting point, of 2130 C The Soul

  partially manufactured is unwound from the coil-

  and the nylon for the sheath 23 is heated to its plastic state and is extruded onto the elastomer 22 This sheath 23 completes the soul-which again passes into a cooling water bath, before the finished soul do not be rolled up

on a receiver coil.

  Because the elastomer 22 completely surrounds

  the fibers 20 and that the nylon sheath 23 surrounds the elastomer

  mother, the fibers follow the elastomer and the nylon sheath

when the cable is stretched.

  The manufacture of the cable 10 of FIG. 1 from this completed core 12 is accomplished in two additional operations. The first of these operations is described in connection with FIGS. 2, 3 and 4 during the first wiring operation which is accomplished-in the manufacturing line of Figure 4, the core 12 is unwound from a spool-delivery 40 and is pulled through a set of movable rollers 41 and a guide 42, to be coated with an adhesive hot melt 25 shown in FIG.

than the one called Eastman 148.

  An adhesive application station 43 of FIG. 4 heats the adhesive 25, coats the nylon sheath and wipes off any excess adhesive. At station 43, the adhesive is heated.

  in a range of 2200 C-2400 C The temperature is sufficient

  high enough for the adhesive to be pumped to flow on the

  Nylon and completely cover it, but it is not enough

  high enough to damage the core The adhesive 25 is

  wiped on the nylon 23 to give it a uniform thickness

  me, as shown in Figure 2, by means of a hinged dying die, which is part of the post 43. Once the adhesive has been applied to the sheath, two layers of stranded steel are deposited on the adhesive On

  choose the amount of adhesive 25 to be sufficient

  to completely cover the sheath and to fill almost

  the interstices 27 between the sheath and the wires 13 of the first

  first layer of stranded steel, as shown in Figure 3.

  Interstices must not be completely filled

  hardening of the adhesive takes place over a period of

  The cured adhesive forms a firm bond between the nylon sheath 23 and the inner layer of the steel strand 13 This bond prevents creep and makes

  that the core containing the fibers follows the steel strand

  cable laying and recovery operations and during service The adhesive is chosen to avoid

  any failure of this link during these operations.

  Returning to Figure 1, we note that the

  the outer conductor of the coaxial cable structure of

  low frequency is formed by the steel strand

  13 and by the driver 14, both lying outside the

  The strand of steel has two layers of

  stranded steel wire of circular cross section.

  An inner layer, or first layer, of the steel strand comprises eight wires wound directly on and in contact with the outer surface of the core. These eight wires have a similar cross-sectional size and are clamped together, With a friction contact They are set up by a first stage of a stringer 45 shown in Figure 4, so as to form a cylindrical pressure cage in which the stranded son press against each other continuously along their surface, without the cylinder sinking. The steel strand of the cable also includes an outer layer, or second layer, of sixteen steel wires, which are placed on the inner stranded wires by a

  second floor of the stringer 45 These sixteen sons have alternated

  natively a large diameter and a small diameter, as shown in Figure 1 They are placed in continuous frictional contact and clamped with each other and with the inner strand wires These wires of the second layer form a shape pressure cage additional cylindrical which

  also keeps in place the inner wire layer.

  The first and second layers of the steel strand are

  born together on the adhesive-coated core by a die

  47, shown in FIG.

  formed, including the core, adhesive and two layers of steel strand, is cleaned in a trichloroethane bath

  48, before being locked in the conductive tube.

  A non-porous conductive cylindrical tube 14, shown in FIG. 1, must be formed directly on the outer layer of steel wires It is formed by a

  welded tube of malleable electrolytic copper This tube strong-

  It provides (1) a good direct current path for the power supply of electronic repeaters to be distributed along the cable, (2) a moisture barrier for the fibers and (3) in combination with steel, the cylindrical outer conductor for the

  low frequency signaling system mentioned above.

  ously. During the manufacture of the cable in the production line of FIG. 4, a copper strip is cleaned

  malleable with high conductivity, 50, it is cut longitudinally

  nally to give it a uniform width and

  The tube is dimensioned so as to loosely fit over the steel core, leaving a gap in the tubular shape around the steel strand by means of a cutting machine and forming a tube. Between the steel and the abutting edges of the strip, which have been laminated together Leaving the tube forming machine 51, the edges of the strip are welded together to form the tubular conductor 14, by a continuous welding machine 53 The conductive tube is immediately squeezed on the outer steel strands by rolling and drawing in a stamping machine 55, forcing some of the copper into the interstices between adjacent wires in the steel strand As shown in FIG. 1, this constriction of the copper in the outer interstices of the second steel layer contributes to ensuring that all the steel strands retain their cylindrical shape, in particular during anipulation-of the cable The necking of the copper on the steel wires

  a contact zone between each wire and the copper, to

  to maintain the cylindrical shape of the strands and to ensure that steel and copper remain in solidarity

  from each other during subsequent manipulation.

254 1782

  Once the copper tube 14 has been narrowed in place, the cable is passed in the course of growth

  in another cleaning bath 57, to perform cleaning

  Final yage in trichloroethane This part of the cable being manufactured is directed to cross a game

  movable rollers 58 and is wound on a receiver reel.

this 60.

  Then, in a separate operation, the insulating jacket 16, shown in FIG. 1, is extruded onto the copper tube 14 The envelope is formed by low density natural polyethylene During the extrusion process of the polyethylene, the cable including the steel strand and the

  copper tube is heated to a sufficiently high temperature

  Polyethylene is heated to a plastic state in a temperature range of 210 o C-230 o C,

  to flow easily during extrusion Temperature

  The copper pipe is raised to a minimum value of 800 C. A bond formed between the polyethylene and the copper is sufficiently strong to be interdependent.

  of each other during the laying and recovery operations

  During this operation and because the copper tube is tight on the steel strand, the polyethylene outer casing and the steel strand are also secured to the cable and during operations corresponding to the operation of the system. Because the envelope, the steel strand and the core are all integral with each other, the fibers are deformed as much as

  other elements of the cable- Because the fibers are

  at 2.0% deformation, they can withstand without

  to break the installation and recovery operations of the cable.

  The optical attenuation in the fibers varies only slightly under the effect of variations-of the tensile strain in the cable The variation of the optical attenuation of the fibers as a function of the deformation is much lower than the variation of attenuation which manifests itself in cable structures

  A description of appropriate optical fibers

  is presented in the following documents-: Proceedings of

  the IEEE, pages 1280-81, September 1974; Digest of Tech.

  Papers, International Conference on Integrated Optics and Optical Fiber Communications, page 26, April 1981; CLEO 1981, article W 6 6-1, June 1981; and IEEE Journal of Quantum Electronics, Vol. QE-18, No. 4, pages 504510, April, 1982. Figure 5 shows the variation of the optical attenuation in the fibers as a function of the deformation of the cable The continuous line 62 represents the variation of the optical attenuation characteristic for the fibers in the cable having the

  According to the invention, the variation of the attenuation

  The optical shade is about 0.01 decibel per kilometer for a deformation of 0.5%. A dashed line 64 represents the variation of the optical attenuation characteristic for fibers in a cable configuration.

  The prior art line 32 shows that the variation of attenuation

  optical shade of the previous structure is about 0.10 decibel per kilometer for a deformation of 0.5%

  decrease in the variation of optical attenuation

  The deformation is the result of the new design.

  allows the elements of the cable to be integral with each other, which opposes the formation of microbends that

  would also create the deformation of the cable.

  It goes without saying that many modifications can be made to the described method and device.

  and represented without departing from the scope of the invention.

Claims (5)

  A method of manufacturing an optical fiber cable comprising reinforcing elements made of steel wire, characterized by the following operations: coating with an adhesive (25) a cable core (12) containing optical fibers (20) ; at least one layer of steel wires (13) is wrapped around the adhesive on the core; forming a conductive tube (14) on the layer of steel wires; and we   shrinks the tube (14) on the layer of steel wires (13).   A method of manufacturing a fiber optic cable according to claim 1, characterized in that an outer surface of the core of the cable (12) is made of nylon (23); the nylon is coated with a hot-melt adhesive (25) and the adhesive is applied to the core of the cable at a temperature within the range of 220 C-240 C.   3 Method of manufacturing a fiber cable   optical devices according to any one of claims 1 or 2,   characterized in that the adhesive (25) is wiped on the core of the cable to give it a uniform thickness which leaves enough adhesive to fill almost the gaps between the steel wire layer (13) and the surface of the cable core (12).   4 Optical fiber cable manufactured according to one   any of the preceding process claims,   characterized in that it comprises: an elastic material (22) coating the fibers (20); a sheath (23) surrounding the elastic material; a stranded wire (13) surrounding the sheath and an adhesive (25) bonding the stranded wire to the sheath to   so that the optical attenuation characteristic of each   that fiber varies only slightly under the effect of variations   deformation ranging from 0 to 1% in the cable.   Optical fiber cable according to claim   4, characterized in that the adhesive (25) is a thermal adhesive.   mofusible which is applied to the sheath at a temperature within a range of 220 OC-240 C. 6 Fiber optic cable according to claim 1, characterized in that the adhesive cures forming a bond having an imperceptible creep, thereby the soul and the stranded wire to be in solidarity with each other during   cable handling operations.   Optical fiber cable according to claim 4, characterized in that the attenuation of the optical fibers   is less than 0.02 decibel per kilometer for a deformation 0.5%.