NZ239019A

NZ239019A - Submarine fibre optic telecom cable: lay up structure.

Info

Publication number: NZ239019A
Application number: NZ23901991A
Authority: NZ
Inventors: Gery Marlier; Jean-Francois Libert
Original assignee: Alcatel Australia
Priority date: 1991-07-18
Filing date: 1991-07-18
Publication date: 1993-12-23

Description

<div class="application article clearfix" id="description"> 239 0 19 13~|-°»| C,0"2.(3>b\l_0^-; \-\o\e,n \^Z_ pi 2 3 DEC 1993 P.O. J-,.- V5»l€" NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "SUBMARINE OPTICAL CABLE" WE, ALCATEL AUSTRALIA LIMITED, A Company of the State of New South Wales, of 280 Botany Road, Alexandria, New South Wales, 2015, Australia, hereby declarc the invention for which wc pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: 1 23 90 19 This invention relates to a submarine fibre optic telecommunication cable including a tube containing optical fibres embedded in a filling material, inside a strand of high strength wires. Document AU-A-81304/87 already proposed a submarine telecommunication cable including a tube of conducting metal surrounding the optical fibres embedded in a filling material inside the tube, an electrical insulator surrounding the tube of conducting metal, and at least one layer of high tensile wires surrounding the insulator, forming a protective shield. Nevertheless, such a cable is not sufficiently strong to prevent possible water ingress and lengthwise spreading of the water, especially when the immersed cable is damaged. Moreover, once in contact with salt water, the wires forming the protective shield can become corroded by bacterial action for instance. This corrosion phenomenon could then generate molecular hydrogen which, under certain conditions, may migrate to come in contact with the optical fibres and thus downgrade the transmission characteristics. Furthermore, the tube of conducting metal containing the fibres implies an expensive structure when a link is not remotely powered, or imposes a different optical module dictated by the tube containing the fibres depending whether or not the link is remotely powered. Attention is drawn to New Zealand Patent Specification No. 239020 whose subject matter relates to the subject matter of the present specification. The purpose of the present invention is to provide a submarine telecommunication cable which prevents the water entering its damaged shield from spreading, which has a light and compact structure and a low production cost, and which can be fitted, if need be, with repeater power supply conductors without modifying its - 4 NOV 2 23$0 1 wiress of the strands are filled with a scaling material preventing the water from spreading into the cable, and in that, the strand itself is surrounded by a second abrasion-resistant and insulating extruded sheath. The cable preferably incorporates at least one of the following features: 5 - conducting devices dedicated to remote power supply of equipment inserted along the cable, made up of a conducting strip between the tube and the first sheath, or between this first sheath and the strand, or of conducting wires associated with the high strength wires of the strand. - a semiconducting layer interfacing the strand and the sccond extruded sheath, made 10 of insulating material laden with conducting particles. - the insulating material is also laden with conducting particles. In order that the invention may be readily carried into effect, embodiments thereof will now be described in relation to the drawings, in which: Figure 1 is a cross-section of a cable in accordance with the present invention. 15 Figures 2 and 3 are cross-sections of two other versions of the figure 1 cable. Throughout these figures, the same item numbers have been used when the same components are illustrated. The cable shown in figure 1 is described in detail, as for figures 2 and 3 versions, only the differences arc mentioned. The cable shown in figure I includes a tube (I) filled with a scaling compound, 20 silica gel (2) for instance, in which the optical fibres (3) arc embedded. The fibres may or may not be wired and may or may not have excess length in the tube. The tube (1) is made of metal, preferably steel, and is resistant to water pressure. It is welded lengthwise either by means of laser, arc welding under inert gas, plasma arc welding, or any other suitable method. This tube (1) may also be made 25 of extruded plastic, in this case it will be associated with some means mentioned below providing the cable with sufficient pressure resistance. 3 23 9 0 19 The cable includes a first extruded sheath (4) surrounding the tube (1) to protect it against local crushing or corrosion. This first sheath (4) is surrounded by a conducting strip (5) made of copper, aluminium or other metal or alloy being good conductor of electricity, dedicated to remote power supply of amplifier repeaters or 5 regenerators inserted between the cablc sections making up the submarine link. The conducting strip (5) is welded lengthwise and shaped like a tube surrounding the first sheath, or it is coiled in one or several layers around this first sheath, or it may also consist of preshaped foils placcd lengthwise and assembled around this sheath. A strand of high strength wires (6), preferably made of steel, is placed around 10 the conducting strip (5) in a single layer as illustrated, or in several layers arranged in the same direction or in opposite direction. The steel wire strand confers tensile strength to the cablc. Moreover, it provides an arch shape, in particular for a plastic tube (1) whose resistance to pressure is insufficient. The spaces between the wires of the strand, and the strand and the tube are IS filled with a sealing material (8), such as polyurcthane resin or other sealing material, preventing the water from spreading lengthwise into the cablc, especially when the immersed cable has been damaged. A second outer sheath (7), made of polyethylene or other electrically insulating and abrasion resistant material, is extruded in one or several layers over the strand. 20 Its thickness depends on the required level of electrical insulation and mechanical protection. As illustrated, this semiconducting interface layer (9) has the advantage of being located between the outer sheath (7) and the strand, and fills the outer spaces between the peripheral wires of the strand and this sheath (7). This layer (9) is a very 25 poor conductor, it may for instance be made of polyethylene laden with conducting particles, in particular carbon particles. A bonding agent, a copolymer for instance, 4 239 0 may be used to ensure that the semiconducting layer (9) adheres to the wires of the strand. The layer (9) prevents high concentration of elcctric fields where roughness exists, which may damage the outer sheath. Outer sheath (7) may thus be thinner. Furthermore, the sealing material (8) is also laden with conducting particles, 5 which is an advantage in particular for the conducting strip (5) which may be lapped and not perfectly smooth, in order to avoid any electrical problem at conducting strip/strand interface level. The cable shown in Figure 2 is different from the one shown in figure 1. Its conducting strip (5) is placed directly on the tube (1) containing the optical fibres and 10 is surrounded by the first extruded sheath (4). It should be noted that in these two examples of implementation, in the space between the wire strand (6) and the tube (1), the conducting strip (5) has a thickness selected to provide suitable electrical resistance and the first extruded sheath (4) then occupies the remaining space. 15 In another version (not shown) of figures 1 and 2 cables, for a link which is not remotely power supplied, the corresponding cable has the same central module defined by the tube (1) containing the fibres embedded, but is without the above-mentioned conducting strip (5) covered by, or covering, the first sheath (4), and without the above-mentioned semiconducting interface layer (9) between the strand 20 and the outer sheath (7). This cablc also contains scaling material (8) in the spaces between the wires of the strand, but this material is not laden with conducting particles. The cable shown in figure 3 is different from the one shown in figures 1 and 2. It is not fitted with the conducting strip (5) but with a strand preferably including, 25 in addition to the high strength wires (6), a peripheral layer of conducting wires (10a) alternating with high strength wires (10b) and dedicated to power supply of the re- 5 239 0 19 generators in the link. The spaccs between the wires of the strand and the strand and the tube (1) are filled with sealing material (not shown) which may be laden with conducting particles, and the outer spaccs between the peripheral wires of the strand arc filled with a semiconducting layer (not shown). The central module defined by 5 the tube (1) containing the inner fibres embedded remains unchanged. From the different examples of cables described above, it becomes clear that the existence, nature and sections of the conducting devices can be modified in accordance with the system's requirements with regard to remote power supply, without having to handle other cable components. The scction of these conducting dcviccs 10 may either be nil for systems without repeater, small for systems with optical amplifiers, or normal for systems with regenerators This docs not affect the resistance to hydrogen and pressure of the cablc. 15 20 25 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 23 90 1 9 What we claim is:-1. A submarine fibre optic telecommunication cable including a tube containing optical fibres embedded in a filling material and a layer of high strength wires around the said tube, wherein said tube, with the layer of high 5 strength wires and a first extruded sheath placed between the tube and the layer provide mechanical resistance to pressure and tensile strength of the cable, and wherein the spaces between the high strength wires of the layer are filled with a sealing material preventing water from spreading into the cable, the layer being surrounded by a second abrasion-resistant and insulating extruded sheath. 10 2. A cable as claimed in claim 1, the cable including conducting devices dedicated to remote power supply of equipment inserted along the cable, wherein said conducting means are made up of a conducting strip, internal to the said layer of high strength wires and associated with the said first sheath, and having a section suited to the said equipment. 15 3 A cable as claimed in claim 2, wherein said conducting strip is placed on the said tube containing the fibres and is welded lengthwise or helically coiled in one or several layers or placed lengthwise on the said tube, and is covered by the said first sheath. 

4. A cable as claimed in claim 2, wherein said conducting strip is placed on 20 the said first sheath and welded lengthwise or coiled in one or several layers or placed lengthwise on the said first sheath, which is directly extruded on the said first tube containing the fibres. 

5. A cable as claimed in claim 2, including conducting devices dedicated to N.
2. FAT■'~CFRC£ —* -4 NOV 1993 ReCEiVC.T 23 90 19 remote power supply of the equipment inserted along the cable, wherein said conductor means are made up of conducting wires which, together with the said high strength wires, belong to the layer. 

6. A cable as claimed in claim 5, wherein said layer has at least a first layer of high strength wires, a second layer of high strength wires and a layer of conducting wires. 

7. A cable as claimed in any of claims 2 to 6, including a semiconducting layer interfacing the layer and the said second extruded sheath, filling the outer spaces between the wires of the strand and adhering to its peripheral wires. 

8. A cable as claimed in claim 7, wherein the semiconducting layer is a polyethylene resin laden with conducting particles. 

9. A cable as claimed in any one of claims 2 to 8, wherein said sealing material is laden with conducting particles. 

10. A cable as claimed in any one of claims 1 to 9, wherein said tube containing the fibres is either made of metal and is pressure resistant, or of plastics whereby the said layer, containing at least one layer of high strength wires, forms a vault around the plastics tube. 

10. A submarine fibre optic telecommunication cable substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings. ALCATEL AUSTRALIA LIMITED B. O'Connor Authorized Agent P5/1/1703 8 </div>