WO2002091055A1 - A submarine communications cable, a method of its production and its use - Google Patents
A submarine communications cable, a method of its production and its use Download PDFInfo
- Publication number
- WO2002091055A1 WO2002091055A1 PCT/DK2002/000277 DK0200277W WO02091055A1 WO 2002091055 A1 WO2002091055 A1 WO 2002091055A1 DK 0200277 W DK0200277 W DK 0200277W WO 02091055 A1 WO02091055 A1 WO 02091055A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- cable
- layer
- long distance
- communications cable
- electrical conductors
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
- G02B6/4401—Optical cables
- G02B6/4415—Cables for special applications
- G02B6/4427—Pressure resistant cables, e.g. undersea cables
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
- G02B6/4401—Optical cables
- G02B6/4415—Cables for special applications
- G02B6/4416—Heterogeneous cables
- G02B6/4417—High voltage aspects, e.g. in cladding
Definitions
- a submarine communications cable a method of its production and its use
- the present invention relates to the field of intercontinental submarine cables for communications purposes using intermediate amplifiers or repeaters.
- the invention relates specifically to a long distance submarine communications cable for use in a communications system requiring a high DC-voltage power supply, said cable comprising one or more optical fibres for transferring optical signals, and one or more electrical conductors for power feeding one or more intermediate units for regenerating said optical signals, and an insulation system as a covering for said one or more electrical conductors.
- the invention furthermore relates to a method of manufacturing a long distance submarine communications cable for use in a communications system requiring a high DC-voltage power supply comprising the steps of providing a core element comprising one or more optical fibres for transferring optical signals, and arranging one or more electrical conductors for power feeding one or more intermediate units for regenerating said optical signals, and arranging an insulation system as a covering for said one or more electrical conductors.
- the invention furthermore relates to the use of a long distance submarine communications cable according.
- the following account of the prior art relates to one of the areas of application of the present invention, submarine cables for long distance optical communications .
- the development of low loss optical fibres for long distance high speed communications has resulted in a decrease in the number of repeaters which are necessary in an optical communications system for the transmission of a certain amount of data or voice traffic over a certain distance. In other words, an increasing distance between the repeaters is possible.
- the power for electrically feeding the repeaters typically has to be supplied from one or more electrical conductors running parallel to the optical fibres in the cable.
- the electrical energy for the repeaters In a long distance submarine communications cable (such as used e.g. for a transatlantic connection) the electrical energy for the repeaters must sometimes be supplied over several thousands of kilometres, requiring DC-voltages in the kilovolt range.
- PE Polyethylene
- Norwegian laid out publication no. 167 778 discloses a submarine fibre optic telecommunications cable comprising centrally located armouring (e.g. steel threads) surrounded by a plastic material in which optical fibres are positioned in helical grooves.
- a watertight metal sheath surrounds the central core of the cable, which again is surrounded by a plastic material such as polyethylene .
- US-A-4 , 907 , 855 discloses a submarine fibre optic cable provided with a stranded layer of metal wires, which serve to supply energy for the regenerators.
- the layer of stranded wires is surrounded by an insulation layer, which in turn is protected by a stranded layer of sheathing wires.
- Both of the stranded layers of wires are embedded in a layer of a plastic, water-repellent material.
- the outer casing of the cable is formed by a metal composite layer sheath.
- WDM Wave Division Multiplexing
- DWDM Dense Wave Division Multiplexing
- intermediate regenerating units e.g. comprising so-called fibre amplifiers (each typically comprising a section of Erbium-doped fibre, a laser pump, a section of dispersion compensating fibre, etc.) .
- the distance between intermediate regenerating units may be in the range 50-100 km, i.e. for a cable of length 6-7000 km
- the increased need for electrical power for the intermediate regenerating units creates problems for a conventional cable construction in that an increased power supply voltage increases the necessary thickness of the insulation layer and thus the diameter of the cable and accordingly gives a relatively lower mass density.
- the cable has to have a certain mass density to be able to position it safely on the seabed.
- a submarine cable further has to be armoured over certain sections of the cable in coastal areas where the probability of interference with fishing trawl and the like is large.
- the armouring process gets increasingly complicated the larger the cable diameter and the cable becomes increasingly difficult to handle:
- the cable becomes heavier and more voluminous per unit length, resulting in increasing costs pr. unit length (large amounts of materials, complicated production, etc.), smaller lengths of the cable can be handled by a given cable ship, i.e. the ship must make more shifts to lay out a given length of cable (requiring more time, and more sea joints, thus being more expensive), etc.
- the object of the present invention is to provide a long distance submarine fibre optical communications cable comprising electrical conductors for power feeding intermediate units and a method of manufacture of said cable, which allows a compact construction at high supply DC-voltages .
- the terms 'inner' and 'outer' in relation to features of a submarine cable are taken to mean that seen relative to the central core of the cable, an 'inner' surface or layer is located closer to the core than an 'outer' surface or layer. In other words an 'outer surface' is located closer to the marine environment than an 'inner surface'.
- the outer sheath of metal enclosing the insulation system is provided to be able to increase the voltage per unit length of the cable.
- a higher supply voltage may be used for a given thickness of the insulation layer.
- a further reduction of the insulation thickness is achieved by supplying the insulation with electrical field limiting semiconducting layers on its inside and outside surfaces.
- a cable construction according to the invention has the advantage over a conventional cable of being more compact for a given power supply voltage, resulting in that less material per unit length is needed, an easier handling as regards armouring and longer lengths per shift to lay out, leading to a reduced 'cost per bit' .
- the power is ON during the layout of the cable. This, in combination with the increasing power supply voltage, requires a careful design of the combined system comprising the power supply, the cable, the regenerating units, the cable ship, and the sea to ensure that the personnel is safe in handling the cable in all possible situations.
- said electrically conducting outer sheath comprises at least one electrically semiconducting layer on its outer surface
- the outer metal sheath has the same potential as the surrounding water (or contact parts with the ship during layout) .
- a short-circuit situation will lead the resulting current to the water (or to the ground connection of contact parts with the ship during layout) thus avoiding a damage of the cable over longer lengths.
- a relatively thick second layer of a semiconducting material e.g.
- a relatively thin (sub mm) first layer of semiconducting material may be applied directly to the outer surface of the electrically conducting outer sheath by an appropriate coating technique (e.g. in the form of a 'hotmelt' adhesive layer) .
- the semiconducting first or second layers may be present alone or in combination.
- the term 'an electrically semiconducting layer' is taken to mean that the electrical conductivity of the layer in question has a value between that of a corresponding metal layer and an insulating layer.
- the semiconducting material has a specific resistance between that of Copper (1,7-10 ⁇ 6 ⁇ cm) and a good electrical insulator ( « 10 17 ⁇ cm) .
- the semiconducting outer layer in contact with the marine environment ensures that the metal sheath has the same electrical potential as the surrounding water.
- An advantage of the invention is that the damage of a short circuit between the electrical conductors in the cable core and the outer metal sheath, which e.g. may occur during a cable rupture, will be limited since current will be able to flow to the water thus avoiding the damage to extend over a longer length of the cable. The minimisation of damages is especially important for a long distance submarine cable, which is often located at great sea depths for which a repair may be extremely costly.
- said electrically conducting outer sheath is provided with at least one electrically insulating layer on its outer surface for mechanical protection and to protect the electrically conducting outer sheath from the marine environment, it is ensured that the metal -water surface of the cable is protected against corrosion.
- a relatively thick second layer of an insulating material e.g. a several mm thick layer of Polyethylene
- a relatively thin (sub mm) first layer of insulating material may be applied directly to the outer surface of the electrically conducting outer sheath by an appropriate coating technique (e.g. in the form of a 'hotmelt' adhesive layer) .
- the insulating first or second layers may be present alone or in combination.
- relatively thick insulating second layer may be present in combination with a relatively thin (sub mm) first layer of semiconducting material, where the thin coating of semiconducting material is applied directly to the outer metal surface and the relatively thick layer of insulating material is applied thereon e.g. by extrusion.
- said at least one electrically insulating layer is provided with an electrically semiconducting layer on its outer surface, it is ensured that it is possible to test the insulation sheath (located between the outer metal sheath and the semiconducting layer) by a voltage test.
- an electrically semiconducting layer is arranged adjacent to the inner surface of said electrically conducting outer sheath.
- the semiconducting layer can e.g. be a relatively thin (sub mm) layer applied directly to the inner surface of the electrically conducting outer sheath by an appropriate coating technique (e.g. in the form of a 'hotmelt' adhesive layer applied to the sheet metal in advance of the cable construction) . It may alternatively be constituted by the outmost layer of the insulation system.
- said insulation system comprises an insulation layer provided with a semiconducting layer on its inner and outer surfaces.
- the electrical field is limited to the insulation layer since the semiconducting layer on the outer surface of the insulation layer is short-circuited to the outer metal sheath and the semiconducting layer on the inner surface of the insulation layer is short-circuited to the one or more electrical conductors for power feeding the regenerating units.
- said inner semiconducting layer of said insulation system is applied to the outer surface of said one or more electrical conductors by a coating technique.
- said outer semiconducting layer of said insulation system is applied to the outer surface of said insulation layer by a coating technique.
- a method of manufacturing a long distance submarine communications cable for use in a communications system requiring a high DC-voltage power supply comprising the steps of providing a core element comprising one or more optical fibres for transferring optical signals, and arranging one or more electrical conductors for power feeding one or more intermediate units for regenerating said optical signals, and arranging an insulation system as a covering for said one or more electrical conductors is furthermore provided by the present invention.
- it comprises the step of applying an electrically conducting, watertight outer sheath to the outer surface of said insulation system, the same advantages as are achieved for the corresponding product claim are provided.
- the step of arranging an insulation system as a covering for said one or more electrical conductors comprises the substeps of arranging an inner semiconducting layer around said one or more electrical conductors, and arranging an insulating layer around said inner semiconducting layer, and arranging an outer semiconducting layer around said insulating layer, the same advantages as are achieved for the corresponding product claim are provided.
- the semiconducting layers may e.g. be applied by extrusion.
- the semiconducting layers are applied to the outer surface of the one or more electrical conductors for feeding the regenerating units and/or to the inner surface of the outer metal sheath by a coating technique, e.g.
- the sheets used for the electrical conductors and/or the outer sheath and/or the outer surface of the insulation layer of the insulation system are coated with a semiconducting material. This has the advantages of yielding an easy addition of the semiconducting layers (possibly present from the start on the metallic foils) and an especially compact cable construction.
- fig. 1 shows a conventional construction of a communications cable
- fig. 2 shows a conventional construction of a communications cable adapted for a high DC-power supply
- fig. 3 shows a communications cable according to the invention
- fig. 4 shows a communications cable according to the invention with an outer semiconducting layer.
- Fig. 1 shows a conventional construction of a communications cable.
- Fig. 1 shows a known conventional communications cable for a power supply of repeaters with a DC voltage of some few kilovolts.
- the cable includes a fibre optic element 1, a tensile armouring 2 and an electrical conductor 3 for power feeding. Then follow the insulation layer 4 and a polymeric sheath 5.
- Fig. 2 shows a conventional construction of a communications cable adapted for a high DC-power supply.
- Fig. 2 shows a conventional communications cable with the components 1, 2 and 3 as for fig. 1 but upgraded for a high power supply DC voltage and therefore with an increased thickness of the insulation layer 4.
- the cable is protected by the polymeric sheath 5.
- Fig. 3 shows a communications cable according to the invention.
- the cable includes a fibre optic element 1, a tensile armouring 2 and an electrical conductor 3 for power feeding of repeaters.
- the insulation layer 4 forms together with the semiconducting layers 6 and 7 an insulation system for high DC voltage supply of repeaters.
- the cable is supplied with a metallic layer 8, which at any time secures a dry insulation system.
- the outer metal sheath 8 may comprise metals such as steel , Aluminium, Copper etc .
- the sheath may be made of sheets of metal that are folded and/or welded to provide a watertight protection of the cable.
- the sheets of metal may be provided with coatings of insulating or semiconducting material (not shown) on one of its sides (typically the outer) or on both.
- the polymeric sheath surrounding the outer metallic layer provides a mechanical and corrosion protection of the cable.
- the sheath material can be insulating or semiconducting or a combination with an insulating sheath, which is covered with a thin semiconducting layer for sheath voltage testing as shown in fig. 4.
- the sheath material is semiconducting (50) (which e.g. may be achieved by the addition of appropriate amounts of carbon black to the insulation), but it might alternatively be insulating.
- Fig. 4 shows a communications cable according to the invention with an outer semiconducting layer.
- the same elements as depicted in fig. 3 and as described above are present in fig. 4, only the polymeric sheath 51 surrounding the outer metallic layer is insulating. Additionally the insulating sheath 51 is supplied with a thin semiconducting layer 9 for sheath voltage testing.
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DKPA200100695 | 2001-05-03 | ||
DKPA200100695 | 2001-05-03 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2002091055A1 true WO2002091055A1 (en) | 2002-11-14 |
Family
ID=8160469
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/DK2002/000277 WO2002091055A1 (en) | 2001-05-03 | 2002-04-30 | A submarine communications cable, a method of its production and its use |
Country Status (1)
Country | Link |
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WO (1) | WO2002091055A1 (en) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4278835A (en) * | 1977-12-16 | 1981-07-14 | The Post Office | Submarine communication cable including optical fibres within an electrically conductive tube |
US4907855A (en) * | 1988-01-15 | 1990-03-13 | Siemens Aktiengesellschaft | Marine cable for a fiber optic waveguide with regenerator supply |
EP0371660A1 (en) * | 1988-11-17 | 1990-06-06 | Timothy Carl Stamnitz | Electro-opto-mechanical cable for fiber optic transmission systems |
US5125062A (en) * | 1990-07-19 | 1992-06-23 | Alcatel Cable | Undersea telecommunications cable having optical fibers |
-
2002
- 2002-04-30 WO PCT/DK2002/000277 patent/WO2002091055A1/en not_active Application Discontinuation
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4278835A (en) * | 1977-12-16 | 1981-07-14 | The Post Office | Submarine communication cable including optical fibres within an electrically conductive tube |
US4907855A (en) * | 1988-01-15 | 1990-03-13 | Siemens Aktiengesellschaft | Marine cable for a fiber optic waveguide with regenerator supply |
EP0371660A1 (en) * | 1988-11-17 | 1990-06-06 | Timothy Carl Stamnitz | Electro-opto-mechanical cable for fiber optic transmission systems |
US5125062A (en) * | 1990-07-19 | 1992-06-23 | Alcatel Cable | Undersea telecommunications cable having optical fibers |
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