Relay submarine optical cable

Abstract

The present disclosure relates to a relay subsea optical cable (1) comprising:-one or more optical fibers (2); a metal tubular buffer element (3) housing the one or more optical fibers (2); -an electrically conductive layer (6) surrounding the tubular buffer element (3), and-at least one armor (4, 10) wherein the at least one armor (4, 10) and / or the electrically conductive layer (6) comprises a bundle (7) of carbon nanotubes (CNTs).

Description

Technical Field

[0001] The present disclosure relates to the field of telecommunication cables, and more particularly to repeater submarine optical cables, which can be deployed at relatively deep depths and long lengths, for example, on the seabed. Background Art

[0002] Optical cables for submarine applications should have high tensile strength while being lightweight. In fact, during installation and operation, when the submarine optical cable is lowered from an installation ship, hundreds of meters from the water surface to the seabed, resulting in significant tensile stress, it should withstand high tensile loads. Therefore, submarine optical cables include one or more metal armour layers, typically made of wound steel wires, which increases the weight of the optical cable. Therefore, generally, the deeper the deployment location, the heavier the optical cable. On the other hand, the pay-out system of the installation ship must be commensurate with the weight of the optical cable to be deployed. Therefore, the heavier the cable, the stronger the grip of the pay-out system is required.

[0003] In addition, submarine optical fiber cables, especially developed for deep-sea transoceanic systems, suffer from attenuation, which can be as high as 0.25 dB / km or more. Therefore, repeaters are generally placed every 50 km to 70 km for optical signal amplification. The repeaters are powered by electricity carried through the submarine optical cable. For this purpose, the repeater submarine optical cable includes an electrical conductor, typically made of copper, optionally bonded to a semiconductor layer. Figure 1 An example of a known repeater submarine optical cable is shown. This further increases the weight of the optical cable without significantly improving the tensile strength due to the poor mechanical properties of copper.

[0004] To maintain good mechanical properties while reducing the overall weight of the optical cable, optical cables reinforced with aramid fibers have been proposed (see, for example, US7285726).

[0005] In non-submarine applications, the problem of providing electrically conductive cables with high tensile strength and low weight is also common. For example, WO 2015 / 162263 A1 discloses a lifting member for an elevator system, which includes a strength member composed of carbon nanotubes (CNTs) surrounded or embedded in a matrix material such as epoxy resin or elastomer, thereby creating a solid structure for the lifting member. In some embodiments, the CNTs are configured to transmit electrical signals through the lifting member to provide power to the elevator car and / or communication between the controller and the elevator car. Summary of the Invention

[0006] Therefore, the applicant's objective is to provide a repeater submarine optical cable capable of transmitting power to an optical repeater, which has high tensile strength while being light enough in weight.

[0007] The applicant has found that providing carbon nanotube (CNT) bundles as a strength member in combination with or as an alternative to armor wires made of metal (such as steel) for a repeater submarine optical cable makes the optical cable lighter while maintaining high tensile strength. The CNT bundles can also be used as a conductive member in combination with or as an alternative to a conductor such as a copper layer optionally bonded to a semiconductor layer, thereby eliminating or reducing the thickness and weight of the conductor.

[0008] In this specification and the claims, the CNT bundles can be made of at least two CNT yarns twisted together with each other, and each CNT yarn is made of multiple CNT filaments.

[0009] Accordingly, the present disclosure relates to a repeater submarine optical cable comprising:

[0010] - one or more optical fibers;

[0011] - a metallic tubular buffer element that houses the one or more optical fibers;

[0012] - a conductive layer that surrounds the tubular buffer element, and

[0013] - at least one armor,

[0014] wherein the at least one armor and / or the conductive layer comprises carbon nanotube (CNT) bundles.

[0015] According to the present disclosure, the CNT bundles can be used as a strength member and / or an electrical conductor according to their positions in the cable, as will be shown below.

[0016] In an embodiment, the CNT bundles are in the form of one or more bundles stored in a jacket in a tight configuration.

[0017] In an embodiment, more bundles are stored in the sheath adjacent to and in direct contact with each other.

[0018] In an embodiment, the armor and the conductive layer are a single layer comprising the CNT bundles.

[0019] In an embodiment, the single layer consists essentially of CNT bundles.

[0020] In an alternative embodiment, the armor comprises a metallic armor wire helically wound around the buffer element and the CNT bundles.

[0021] In an embodiment, the conductive layer comprises a conductive element that surrounds the armor and comprises the CNT bundles.

[0022] Optionally, the conductive layer further comprises a swelling layer bonded to the conductive element.

[0023] In an embodiment, the repeater submarine optical cable further includes a protective sheath surrounding the conductive layer and the armor.

[0024] In an embodiment, the repeater submarine optical cable includes an outer armor surrounding the protective sheath.

[0025] In an embodiment, the outer armor includes one or more layers, and the layers include multiple metal armor wires wound in a spiral.

[0026] In an alternative embodiment, the outer armor consists essentially of CNT bundles. Description of the Drawings

[0027] Further features and advantages will become more apparent from the following description of some embodiments given by way of example with reference to the accompanying drawings, in which:

[0028] Figure 1 is a cross-sectional view of a repeater submarine optical cable according to the prior art;

[0029] Figure 2a and Figure 2b is a cross-sectional view of CNT bundles of a repeater submarine optical cable according to an alternative embodiment;

[0030] Figure 3 is a cross-sectional view of a repeater submarine optical cable according to an embodiment of the present disclosure;

[0031] Figure 4 is a cross-sectional view of a repeater submarine optical cable according to another embodiment of the present disclosure; and

[0032] Figure 5 is a cross-sectional view of a repeater submarine optical cable according to yet another further embodiment of the present disclosure; and

[0033] Figure 6 is a cross-sectional view of a repeater submarine optical cable according to yet another further embodiment of the present disclosure. Detailed Description

[0034] For the purposes of this specification and the appended claims, unless otherwise specified, all numbers expressing quantities, numbers, percentages, etc. should be understood to be modified in all instances by the term "about". Additionally, all ranges include any combination of the disclosed maximum and minimum points and include any intermediate ranges therebetween, which intermediate ranges may or may not be specifically recited herein.

[0035] For the purposes of this specification and the appended claims, the word "a" is used to describe the elements and components of the present invention. This is done merely for convenience and to give a general sense of the present invention. In this specification and the claims, it should be understood to include one or at least one and the singular also includes the plural, unless it is clearly otherwise indicated.

[0036] In at least one of the above aspects, the present disclosure can be implemented according to one or more of the following embodiments, optionally combined together.

[0037] Figure 1 A relay submarine optical cable 1 known in the art is shown. The optical cable 1 is suitable for submarine applications. For example, as discussed in the introduction section of this specification, the optical cable can be deployed on the seabed.

[0038] The optical cable 1 can include one or more optical fibers 2 bundled within a tubular buffer element 3. The tubular buffer element 3, which is suitable as a water barrier, is made of a metal such as copper or steel. The tubular buffer element 3 can be manufactured by longitudinally welding (e.g., laser welding) a metal foil around the optical fibers 2. For the purposes of this specification, an "optical fiber" means an optical core that transmits light and is surrounded by one or more protective layers.

[0039] In addition to the optical fibers 2, the buffer element 3 can also contain one or more elements capable of absorbing hydrogen, such as gels or hydrogenophilic filling compounds.

[0040] The optical cable 1 includes an inner armor 4 that surrounds and optionally directly contacts the tubular buffer element 3. The inner armor 4 can be formed by a layer of helically wound metal armor wires 5. The armor wires 5 can be made of a steel such as galvanized steel.

[0041] The optical cable 1 further includes a conductive layer 6 that surrounds and can directly contact the inner armor 4. The conductive layer 6 is capable of powering an optical repeater (not shown) through the optical cable 1 itself. The conductive layer 6 includes a conductive element 6a made of, for example, copper. Additionally, the conductive layer 6 can include a composite conductive element, where the conductive element 6a is optionally bonded to a semiconductor layer and / or a swelling layer 6b. The layer 6b can be in the form of, for example, a textile or non-woven fabric tape made of polyester fibers filled with carbon black and water-absorbing powder.

[0042] A protective sheath 9 surrounds the conductive layer 6, for example, directly contacting the conductive layer 6. For example, the protective sheath 9 is formed by extruding a polymeric material such as HDPE (high-density polyethylene). The protective sheath 9 helps prevent the optical cable 1 from being immersed in water.

[0043] The optical cable 1 can also include an outer armor 10 that surrounds the protective sheath 9, for example, directly contacting it. The outer armor 10 can include one or more layers of helically wound metal (e.g., steel) armor wires 11.

[0044] The optical cable 1 may further include an outermost protective layer 12 surrounding the outer armor 10, e.g., in direct contact therewith. The outermost protective layer 12 may include a sheath formed by extruding a polymeric material such as HDPE (high density polyethylene). Alternatively, the outermost protective layer 12 comprises polypropylene (PP) yarns or consists essentially of polypropylene (PP) yarns. The PP yarns can improve handling performance.

[0045] As will be described in more detail below, the repeater submarine optical cable of the present disclosure includes a bundle of carbon nanotubes (CNT) as a strength member and / or as an electrical conductor (in combination with or instead of the conductive element 6a).

[0046] When the CNT bundles are intended as strength members, they can be combined with the metal wires 5 of the inner armor 4 and / or the metal wires 11 of the outer armor 10 or alternatively be present in the optical cable. Two of these embodiments are shown in Figure 4 wherein the inner armor 4 includes armor wires 5 and CNT bundles 7, and in Figure 5 wherein all the armor wires 11 of the outer armor 10 are replaced by CNT bundles 7.

[0047] When the CNT bundles are intended as electrical conductors, they can be combined with the conductive element 6a or alternatively be present. One of these embodiments is shown in Figure 6 wherein the conductive element 6a is replaced by a CNT bundle 7. In this case, the optional layer 6b can be omitted, especially when it is only a semiconductor.

[0048] The diameter of the CNT bundles can be between 0.2 mm and 1 mm and is formed by CNT yarns having a diameter between 10 μm and 100 μm (where each CNT yarn is formed by filaments having a diameter between 2 nm and 20 nm).

[0049] The specific conductivity of the CNT bundles is lower than that of copper (about 5,600 S·m / mm 2 vs 6,300 S·m / mm 2 ), while the tensile strength of the CNT bundles is higher than that of steel (5 to 70 GPa for steel vs 0.4 to 1.55 GPa). Considering that the strength-to-weight ratio (specific strength) is greater than 40,000 compared to a value of about 150 kN·m / kg for high carbon steel, the mechanical properties of the CNT bundles are even more prominent compared to steel.

[0050] In an embodiment, as shown in Figure 2a and Figure 2b the CNT bundles are in the form of one or more bundles 7 held in a jacket 8 in a tight configuration. For example, a single jacket 8 can be configured to hold a single CNT bundle 7 ( Figure 2a ) or two CNT bundles 7 (Figure 2b ), for example, stored adjacent to each other and in direct contact. For example, the jacket 8 is an extruded tube made of, for example, a polyurethane or rubber-(EPR, NBR)-based material or polyethylene or polypropylene.

[0051] In Figure 3 embodiments, the inner armor 4 and the conductive layer 6 are in the form of a single layer 4, 6, where the CNT bundles provide both mechanical (tensile) strength and conductivity. As Figure 2a or Figure 2b shown, the CNT bundles can be in the form of yarn bundles 7 in the jacket 8. The CNT bundles are helically wound around the buffer tube 3 and optionally in direct contact with the buffer tube 3. In this case, the total weight of the optical cable is reduced relative to Figure 1 optical cables, and as a single layer, it is lighter than a steel layer (the weight of the conductive layer is negligible compared to the weight of the armor layer), and can provide the sought-after electrical and mechanical properties for the optical cable.

[0052] In Figure 4 embodiments, the inner armor 4 includes a plurality of helically wound metal armor wires 5 and CNT bundles in the form of, for example, yarn bundles 7 in the jacket 8 as described in Figure 2a or Figure 2b , while the conductive layer 6 is as described with respect to Figure 1 . In this case, the total weight of the optical cable is reduced relative to Figure 1 optical cables.

[0053] In Figure 5 embodiments, the outer armor 10 is based on CNT bundles as strength members (instead of Figure 1 the steel wires 11 of known optical cables). The CNT bundles can be in the form of yarn bundles 7 in the jacket 8 as described in Figure 2a or Figure 2b . The CNT bundles are helically wound around the protective sheath 9 and optionally in direct contact with it. In this case, for the reasons already mentioned above, the weight of the optical cable is significantly reduced relative to Figure 1 optical cables.

[0054] In Figure 6 embodiments, the conductive layer 6 includes CNT bundles replacing the conductive elements 6a and an optional semiconductor layer 6b. The CNT bundles can be in the form of yarn bundles 7 in the jacket 8 as described in Figure 2a or Figure 2b . The CNT bundles are helically wound around the inner armor 4 and optionally in direct contact with it. In this case, the CNT bundles act only as electrical conductors. Therefore, the number of metal armor wires 5 and / or 11 or the number of layers of armor 4 and / or 10 can be reduced because electrical conductors made of CNTs are less susceptible to tensile stress than those made of copper.

[0055] In addition, according to the present disclosure Figures 3 to 6 the optical cable 1 may include an outermost protective layer 12 substantially composed of polypropylene (PP) yarns.

[0056] Thus, the CNT bundles can be used entirely or partially as a tensile element, as an electrical conductor, or as both a tensile strength element and an electrical conductor. Depending on the performance of the required optical cable in terms of weight, tensile strength, and electrical conductivity, the number of steel wires and / or copper conductive elements 6a can be partially reduced or completely eliminated and replaced with an appropriate amount of CNT bundles having equivalent mechanical and / or electrical properties.

[0057] Hereinafter, a comparison is made between a known optical cable (having a structure similar to that of Figure 1 but having an outer armor 10 including two layers of steel wires 11) and the optical cable according to the present disclosure Figure 3 in terms of size and weight, where the inner armor and the electrical conductor are made of CNT bundles.

[0058] Considering that the buffer tubes 3 of the two optical cables have the same diameter (4.4 mm), the electrical conductor 6 of the comparison optical cable has a diameter of 9.0 mm, while in the optical cable of Figure 3 the layers 4, 6 of CNT bundles serving as the inner armor layer and the conductive layer have a diameter of 13 mm. The weight of the inner armor 4 + conductive layer 6a of the comparison optical cable is 328 kg / km, while the weight of the layers 4, 6 of CNT bundles is 240 kg / km.

[0059] The protective sheath 9 of the comparison optical cable has an outer diameter of 17 mm and a weight of 52 kg / km, while Figure 3 the protective sheath 9 of the optical cable of

[0060] has an outer diameter of 21 mm and a weight of 199 kg / km due to the larger diameter of the underlying CNT layers 4, 6. Figure 3 The outer armor 10 (including two layers of steel wires 11) of the comparison optical cable has a diameter of 27.4 mm. Since the CNT bundles acting as the inner armor 4 (and the electrical conductor 6) have a greater tensile strength than the steel wires, in the optical cable of

[0061] the outer armor 10 made of a single layer of steel wire 11 is suitable for bearing the weight of the optical cable, and this single-layer outer armor 10 has a diameter of 26.2 mm. The weight of the double-layer outer armor 10 of the comparison optical cable is 2,145 kg / km, while the weight of the single-layer outer armor 10 of the current optical cable is 1,200 kg / km. Figure 3 The outermost protective layer 12 of the comparison optical cable has an outer diameter of 34.2 mm and a weight of 230 kg / km, while

[0062] Figure 3 the outermost protective layer 12 of the optical cable of

[0062] Figure 3 has an outer diameter of 33 mm and a weight of 221 kg / km due to the smaller diameter of the underlying outer armor 10.

[0062] Add the weight of the buffer tube 3 (45 kg / km) to the weight of the two above-mentioned optical cables. The total weight of the optical cable is compared to be 2,908 kg / km, while Figure 3 the total weight of the optical cable is 1,906 kg / km.

[0063] Compared with known optical cables, the optical cable according to the present disclosure has a smaller diameter and has almost half the weight.

[0064] It is further observed that the manufacturing of steel and copper causes a large amount of global CO2 emissions, while CNT can be made from hydrocarbons, capture carbon and jointly produce hydrogen. Therefore, since the amount of steel and copper can be reduced, the relay submarine optical cable according to the present disclosure is more sustainable than the relay submarine optical cable according to the known technology.

Claims

1. A repeater submarine optical cable (1), comprising: - one or more optical fibers (2); - a metallic tubular buffer member (3) that houses the one or more optical fibers (2); - a conductive layer (6) that surrounds the tubular buffer member (3), and - at least one armor (4, 10), wherein the at least one armor (4, 10) and / or the conductive layer (6) comprises a carbon nanotube (CNT) bundle (7).

2. The relay submarine optical cable (1) according to claim 1, wherein, The CNT bundle is in the form of one or more bundles (7) stored in a jacket (8) in a tight configuration.

3. The relay submarine optical cable (1) according to claim 2, wherein, More bundles (7) are stored adjacent to and in direct contact with each other in the sheath (8).

4. The relay submarine optical cable (1) according to claim 1, wherein, The armor (4) and the conductive layer (6) are single layers (4, 6) that comprise the CNT bundle (7).

5. The relay submarine optical cable (1) according to claim 4, wherein, The single layer (4, 6) consists essentially of CNT bundles (7).

6. The relay submarine optical cable (1) according to claim 4, wherein, The armor (4) comprises a metallic armor wire (5) helically wound around the buffer member (3) and the CNT bundle (7).

7. The relay submarine optical cable (1) according to claim 1, wherein, The conductive layer (6) comprises a conductive element (6a) that surrounds the armor (4) and comprises the CNT bundle.

8. The relay submarine optical cable (1) according to claim 7, wherein, The conductive layer (6) further comprises a swelling layer (6b) joined to the conductive element (6a).

9. The repeater submarine optical cable (1) according to claim 1, further comprising a protective sheath (9) that surrounds the conductive layer (6) and the armor (4).

10. The repeater submarine optical cable (1) according to claim 9, comprising an outer armor (10) that surrounds the protective sheath (9).

11. The relay submarine optical cable (1) according to claim 10, wherein, The outer armor (10) comprises one or more layers that comprise a plurality of metallic armor wires (11) helically wound.

12. The relay submarine optical cable (1) according to claim 10, wherein, The outer armor (10) consists essentially of CNT bundles (7).

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