FR3135149A1 - OPTICAL CABLE - Google Patents

Abstract

The invention relates to an optical cable (1) comprising: - a sheath (2) comprising a wall (21) delimiting an internal cavity (22), and - a plurality of components (3) contained in the internal cavity (22), the components (3) including a plurality of optical modules (31) and one or more additional components (32), including at least one hydro-inflatable line (32) extending inside the internal cavity (22), in in which each optical module (31) consists of a bundle of optical fibers (33) and one or more wire(s) (34) for holding together the optical fibers (35) of the bundle, and in which a ratio between a linear mass of all of the optical fibers (35) of the optical fiber bundles (33) and a linear mass of all of the components (3) extending inside the internal cavity (22), at exclusion of possible traction reinforcements (37), is high. Figure for abstract: Figure 1

Description

OPTICAL CABLE FIELD OF THE INVENTION

The invention relates to an optical cable. The invention relates in particular, but not exclusively, to an aerial optical cable.

STATE OF THE ART

Some optical cables include a plastic sheath, possibly reinforced, and optical modules extending inside the sheath. Each optical module comprises a plastic casing and a plurality of optical fibers contained in the casing.

In this type of optical cables, the sheath is generally manufactured by extruding plastic material around the optical modules. During extrusion, the plastic material is heated to its melting temperature. In order to protect the optical modules from heat and avoid sticking between the sheath and the casings of the optical modules, the optical cable generally includes a protective ribbon surrounding all of the optical modules. The protective tape can for example be made of polyester. The protective tape is wound helically or placed longitudinally around the optical modules, so as to thermally insulate the optical modules from the cable sheath during the extrusion operation.

Furthermore, each optical module is generally filled with a filling composition, so that the filling composition occupies the space between the optical fibers and the envelope. The filler composition generally has the consistency of a gel. The filling composition has the function of protecting the optical fibers from humidity. In addition, in the event of accidental penetration of water inside the envelope of an optical module, the filling composition blocks the circulation of water inside the envelope. The filler compositions used are generally synthetic compositions, for example compositions based on petroleum derivatives, such as petroleum jelly.

A disadvantage of these optical cables is that their manufacture requires a large amount of energy and a large amount of plastic or synthetic material.

In addition, recycling these optical cables can be complex. Indeed, to be able to be recycled, the optical cables must first be dismantled, which requires the removal of the protective tape, the removal of the optical module envelopes and the cleaning of the optical fibers in order to eliminate the filler composition.

Among optical cables, aerial optical cables are intended to be suspended or attached to poles or buildings, outdoors.

Thus, these aerial optical cables are exposed to risks of deterioration: they can be torn or crushed, for example in the case of a car accident or a fall from a tree.

Additionally, these aerial optical cables must be both lightweight and weather resistant. In particular, these aerial optical cables must be resistant to ultraviolet radiation, have minimal wind resistance and have sufficient mechanical strength to support a certain weight of ice that can accumulate on the cables.

An aim of the invention is to propose an optical cable which can be manufactured using less energy or using less plastic or synthetic material, and which can be more easily recycled.

This goal is achieved within the framework of the present invention, thanks to an optical cable comprising:

- a sheath comprising a wall delimiting an internal cavity, and

- a plurality of components contained in the internal cavity, the components may include one or more traction reinforcement(s),

wherein the components contained in the internal cavity comprise a plurality of optical modules extending inside the internal cavity, each optical module consisting of a bundle of free optical fibers and one or more wire(s) to hold together the optical fibers of the bundle, and one or more additional components extending inside the internal cavity,
in which the additional component(s) comprise at least one hydro-swellable line extending inside the internal cavity, the hydro-swelling line comprising a composition capable of swelling upon contact with water, and
in which a ratio between a linear mass of all the optical fibers of the optical fiber bundles and a linear mass of all the components extending inside the internal cavity, excluding the tensile reinforcements, is greater than or equal to a threshold as defined according to table 1:
Number of optical fibers per optical module Threshold 2 40% 3 49% 4 55% 5 60% 6 63% 7 66% 8 68% 9 70% 10 71% 11 73% from 12 to 17 74% from 18 to 23 78% from 24 to 35 80% from 36 to 47 83% ≥48 84%

Table 1 .

By “free optical fibers” we mean optical fibers which are not linked together by any means other than the wire(s) which hold them together. In particular, the optical fibers of the same bundle of optical fibers are not linked together by gluing or welding. This has the consequence that if the wire(s) are removed, the optical fibers in the bundle separate from each other.

In such an optical cable, the use of plastic material is reduced due to the fact that the optical modules consist only of a bundle of optical fibers and one or more wire(s) wound around the bundle of optical fibers , and do not include an envelope surrounding the optical fiber bundle.

On the one hand, this has the consequence that the optical modules are arranged naturally in the internal cavity in relation to each other, occupying less space.

On the other hand, as the optical modules do not include an envelope, it is not necessary to provide a thermal shield between the optical modules and the cable sheath.

As a result, the internal cavity can have a reduced dimension and the external diameter of the optical cable can also be reduced.

Furthermore, the use of a filling composition is not necessary, since the optical modules benefit from the effect of the hydroinflatable line(s) present in the internal cavity.

Thus, the proposed optical cable has a ratio between the linear mass of all of the optical fibers of the optical fiber bundles and the linear mass of all of the components extending inside the internal cavity high.

This type of optical cable is particularly suitable for use as an aerial optical cable because it is lightweight and compact. This makes it possible to install a greater number of optical cables on the same pole or on the same building or in the same draw pipe. This makes it possible to considerably reduce the environmental impact of the infrastructure for deploying fiber optic cable networks.

When the optical cable is wound onto a reel for storage or transportation, the reel also has reduced weight, which helps reduce transportation costs.

Optical cable recycling is simplified and consumes less energy because the optical cable does not include protective tape or filler composition, and the optical modules do not include casings.

In addition, as the optical cable does not include protective tape and the optical modules do not include an envelope, access to the optical fibers is facilitated when maintenance operations are necessary.

In particular, the wire(s) wound around the bundle of optical fibers can be made of a material having a high melting temperature, while remaining flexible and thus leaving easy access to the optical fibers, unlike optical modules which would include a plastic envelope which would be made of materials having a high melting temperature which would make access to the fibers more difficult.

The proposed optical cable may also have the following characteristics:

- the or each wire of an optical module has a linear mass strictly less than 0.0375 grams per meter, preferably less than 0.012 grams per meter;

- the or each wire of an optical module is wound helically around the bundle of optical fibers to hold the optical fibers of the bundle together;

- the or each wire is wound helically around the bundle of optical fibers with a winding pitch less than or equal to 60 millimeters, preferably less than or equal to 35 millimeters;

- the wire or each wire is wound helically around the bundle of optical fibers with a winding pitch greater than or equal to 15 millimeters;

- the or each wire comprises a plurality of untwisted filaments;

- the or each wire has a breaking strength of at least 0.9 Newtons;

- at least one of the optical modules comprises two wires wound helically around the bundle of optical fibers to hold the optical fibers relative to each other, one of the two wires being wound in an S winding direction around the bundle of optical fibers, and the other of the wires being wound in a Z winding direction around the bundle of optical fibers;

- the wall of the sheath is formed in a single single layer of material, and the optical cable does not include a protective envelope between the wall of the sheath and the optical modules;

- the optical cable comprises two supporting elements, embedded in the material of the wall of the sheath, and arranged in diametrically opposite positions;

- the wall of the sheath is formed from a material having a melting temperature greater than or equal to 130 degrees Celsius;

- the wall of the sheath is formed of a material having a melting temperature lower than a melting temperature of the material of the wire(s) of the optical modules;

- the internal cavity delimited by the wall of the sheath is unique and contains all of the optical modules of the optical cable and additional components.

PRESENTATION OF DRAWINGS

Other characteristics and advantages will emerge from the description which follows, which is purely illustrative and not limiting, and must be read with reference to the appended drawings, among which:

- there is a general schematic representation of an optical cable conforming to a possible embodiment of the invention,

- there schematically represents, in cross section, a first example of an optical cable, conforming to a possible embodiment of the invention,

- there schematically represents, in cross section, a second example of optical cable, conforming to a possible embodiment of the invention,

- there schematically represents, in cross section, a third example of optical cable, conforming to a possible embodiment of the invention,

- there represents schematically, in cross section, a fourth example of optical cable, conforming to a possible embodiment of the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

On the , the optical cable 1 shown comprises a sheath 2, and a plurality of components 3 contained inside the sheath 2.

The sheath 2 extends in a general longitudinal direction. The sheath 2 comprises a wall 21 delimiting an internal cavity 22. The wall 21 of the sheath 2 has a tubular shape and surrounds the components 3. In the example illustrated in the , the wall 21 of the sheath 2 has a cross section (section in a plane perpendicular to the longitudinal direction) of circular shape.

The wall 21 of the sheath 2 is formed in a single single layer of material. This means that the optical cable 1 does not include an additional layer of material surrounding all of the components 3 contained in the internal cavity 22. In particular, the optical cable 1 does not include a thermal protection envelope between the wall 21 of the sheath 2 and the components 3.

The sheath 2 can be formed by extrusion directly around the components 3. The material of the wall 21 of the sheath 2 has a melting point greater than or equal to 130 degrees Celsius. The material of the wall 21 of the sheath 2 is for example polypropylene or polyethylene.

The optical cable 1 further comprises supporting elements 4 to increase the mechanical strength of the optical cable 1. The supporting elements 4 are embedded in the material of the wall 21 of the sheath 2. In the example illustrated in the , the optical cable 1 comprises two carrying elements 4 arranged in diametrically opposite positions. The supporting elements 4 may comprise strands of metal wires. Alternatively, the supporting elements 4 can be formed from a polymer material reinforced with fibers (in English, “fiber-reinforced plastic” or “FRP”), for example with glass, carbon or aramid fibers.

The components 3 are all contained inside the internal cavity 22 delimited by the wall 21 of the sheath 2.

The components 3 include a plurality of optical modules 31.

In addition, the components 3 may include one or more hydro-inflatable lines 32.

In the example illustrated on the , components 3 include two optical modules 31 and a hydro-inflatable line 32.

Each optical module 31 consists of a bundle of optical fibers 33 and one or more wire(s) 34 wound helically around the bundle of optical fibers 33 to hold together the optical fibers 35 of the bundle of optical fibers 33. The optical modules 31 do not include an envelope surrounding the optical fibers 33.

Each bundle of optical fibers 33 is made up of a plurality of optical fibers 35. The optical fibers 35 are free inside the bundle of optical fibers 33, that is to say that the optical fibers 35 are not linked between them by means other than the wire(s) 34. The bundles of optical fibers 33 are made up of an identical number of optical fibers 35. The number of optical fibers 35 per bundle is included in a range going from 2 to 48 optical fibers.

In the example illustrated on the , each bundle of optical fibers 33 is made up of 12 optical fibers.

In the example illustrated on the , each optical module 31 comprises two wires 34, one of the wires being wound helically in an S winding direction around the bundle of optical fibers 33 and the other of the wires being wound helically in a winding direction in Z (opposite of the direction of winding in S) around the bundle of optical fibers 33.

Each wire 34 is wound helically around the bundle of optical fibers 33, with a winding pitch greater than or equal to 15 millimeters and less than or equal to 60 millimeters, preferably less than or equal to 35 millimeters.

Each wire 34 may comprise a plurality of untwisted filaments. In this way, when it is wound around the bundle of optical fibers 33, the wire 34 flattens and matches the external shape of the bundle of optical fibers 33. Thus, the optical modules 31 have a particularly compact shape.

Each wire 34 can have a breaking strength of at least 0.9 Newtons.

The hydro-inflatable line 32 extends inside the internal cavity 22, parallel to the bundles of optical fibers 33. The hydro-inflatable line 32 comprises an elongated support and a composition capable of swelling on contact with water, the support being impregnated with the composition. The composition capable of swelling on contact with water comprises for example a superabsorbent polymer (in English “superabsorbent polymer” or “SAP”). The superabsorbent polymer may comprise a polyacrylate or a polyacrylamide, either as is or grafted onto a natural polymer such as an amide, cellulose, a methylcellulose ester, a cellulose ether such as carboxymethyl cellulose. The composition likely to swell on contact with water is preferably in the form of a powder. Thus, in the event of contact with water, the composition disperses in the water and swells inside the internal cavity 22, which creates a plug and prevents the water from progressing inside the cavity 22 along the optical cable 1.

In optical cable 1 shown in the , the ratio between a linear mass of all of the optical fibers 35 of the optical fiber bundles 33 and a linear mass of all of the components 3 extending inside the internal cavity 22 is greater than or equal to 91%.

This means that a large part of the weight of the components 3 contained in the internal cavity 22 of the optical cable 1 is constituted by the weight of the optical fibers, and not by the weight of the other components contained in the internal cavity 22 of the optical cable.

Example 1

In the first example illustrated on the , the optical cable 1 comprises a sheath 2 delimiting an internal cavity 22, two optical modules 31 extending inside the internal cavity 22 and a hydroinflatable cable 32 extending inside the internal cavity 22.

The wall 21 of the sheath 2 is made of high density polyethylene (HDPE).

The optical cable 1 further comprises two carrying elements 4. In this example, each carrying element 4 is made up of a strand of metal wires. The supporting elements 4 are embedded in the material of the sheath 2. In this example, the supporting elements 4 are arranged in diametrically opposite positions.

The internal cavity 22 has a diameter equal to 2.10 millimeters.

Each optical module 31 is made up of a bundle of twelve optical fibers 35 and two wires 34 wound helically around the bundle of optical fibers 33.

Each optical fiber 35 has a diameter equal to 245 micrometers. The linear mass of an optical fiber 35 is equal to 0.0623 grams per meter.

The linear mass of all the optical fibers 35 of all the bundles of optical fibers 33 is equal to 1.49 grams per meter.

Each wire 34 surrounding one of the bundles of optical fibers 33 has a linear mass equal to 0.0075 grams per meter. The winding pitch of each wire 34 is equal to 32 millimeters.

The hydroinflatable line 32 has a linear mass equal to 0.29 grams per meter.

The linear mass of all of the components 3 extending inside the internal cavity 22 (namely the two optical modules 31 and the hydroinflatable line 32) is equal to 1.815 grams per meter.

Thus, in this first example, the ratio between the linear mass of all of the optical fibers 35 of the optical fiber bundles 33 and the linear mass of all of the components 3 extending inside the internal cavity 22 is equal at 1.495 / 1.815 = 0.8236, i.e. 82.36%.

Example 2

In the second example illustrated on the , the optical cable 1 comprises a sheath 2 delimiting an internal cavity 22, twelve optical modules 31 extending inside the internal cavity 22 and four hydroinflatable lines 32 extending inside the internal cavity 22.

Sheath 2 has an external diameter equal to 8.7 millimeters.

The wall 21 of the sheath 2 is made of high density polyethylene (HDPE).

The optical cable 1 further comprises two supporting elements 4. In this example, each supporting element 4 is formed from a polymer material reinforced with glass fibers. The supporting elements 4 are embedded in the material of the sheath 2. In this example, the supporting elements 4 are arranged in diametrically opposite positions.

Each optical module 31 is made up of a bundle of six optical fibers 35 and two wires 34 wound helically around the bundle of optical fibers 33.

Each optical fiber 35 has a diameter equal to 245 micrometers. The linear mass of an optical fiber is equal to 0.0623 grams per meter.

The linear mass of all the optical fibers 35 of all the bundles of optical fibers 33 contained in the internal cavity 22 is equal to 4.49 grams per meter.

Each wire 34 surrounding one of the bundles of optical fibers 33 has a linear mass equal to 0.0075 grams per meter. The winding pitch of each wire is equal to 32 millimeters.

The hydroinflatable lines 32 each have a linear mass equal to 0.29 grams per meter.

The linear mass of all the components 3 extending inside the internal cavity 22 (namely the ten optical modules 31 and the four hydroinflatable lines 32) is equal to 5.83 grams per meter.

Thus, in this second example, the ratio between the linear mass of all of the optical fibers 35 of the optical fiber bundles 33 and the linear mass of all of the components 3 extending inside the internal cavity 22 is equal at 4.49 / 5.83 = 0.77, i.e. 77%.

Example 3

In the third example illustrated on the , the optical cable 1 comprises a sheath 2, 60 optical modules 31 extending inside the internal cavity 22 of the sheath 2 and twenty-one hydroinflatable cables 32 extending inside the cavity of the sheath 22.

Sheath 2 has an external diameter equal to 15.7 millimeters.

The wall 21 of the sheath 2 is made of high density polyethylene (HDPE).

The optical cable 1 further comprises two supporting elements 4. In this example, each supporting element 4 is formed from a polymer material reinforced with glass fibers. The supporting elements 4 are embedded in the material of the sheath 2. In this example, the supporting elements 4 are arranged in diametrically opposite positions.

In this example, the sixty optical modules 31 are grouped into five packages 36 of twelve optical modules 31 each.

More precisely, in this example, each package 36 comprises twelve optical modules 31, three hydro-inflating lines 32 and a wire 38 surrounding the optical modules 31 and the hydro-inflating lines to hold them together.

Each optical module 31 is made up of a bundle of twelve optical fibers 35 and two wires 34 wound helically around the bundle of optical fibers 33.

Each optical fiber 35 has a diameter equal to 245 micrometers. The linear mass of an optical fiber 35 is equal to 0.623 grams per meter.

The linear mass of all of the optical fibers 35 of all of the bundles of optical fibers 33 is equal to 44.86.2 grams per meter.

Each wire 34 surrounding one of the bundles of optical fibers 33 has a linear mass equal to 0.0075 grams per meter. The winding pitch of each wire is equal to 32 millimeters.

The hydroinflatable lines 32 each have a linear mass equal to 0.29 grams per meter.

Furthermore, the optical cable 1 further comprises a wire 39 surrounding all of the packages 36 of optical modules 31.

In this example, the wire 39 surrounds the five packages 36 of optical modules 31 and six hydro-inflatable lines 32 located outside the packages 36.

The wire 39 surrounding the packages 36 of optical modules 31 has a linear mass equal to 0.167 grams per meter.

The reinforcing element 37 is formed from glass wicks. The reinforcing element 37 has a linear mass equal to 1.7 grams per meter.

The linear mass of all of the components 3 extending inside the internal cavity 22, excluding the reinforcing element 37, (namely the five packages 36 including the sixty optical modules, the wires 38 and 39, and the twenty-one hydro-inflatable lines 32) is equal to 56 grams per meter.

Thus, in this third example, the ratio between the linear mass of all of the optical fibers 35 of all of the bundles of optical fibers 33 and the linear mass of all of the components 3 extending inside the cavity internal 22, excluding the reinforcing element 37, is equal to 44.86 / 53 = 0.846, that is to say 85%.

Example 4

In the fourth example illustrated on the , optical cable 1 is identical to the optical cable illustrated on the , except that it does not include a reinforcing element 37 extending inside the internal cavity 22.

The linear mass of all the components 3 extending inside the internal cavity 22 (namely the five packages 36 including the sixty optical modules, the wires 38 and 39, and the twenty-one hydroinflatable lines 32) is equal to 56 grams per meter.

Thus, in this fourth example, the ratio between the linear mass of all of the optical fibers 35 of all of the bundles of optical fibers 33 and the linear mass of all of the components 3 extending inside the cavity internal 22 is identical to that of the cable of the .

Table 2 compares external diameters (in millimeters) of several optical cables conforming to the state of the art with external diameters of optical cables conforming to embodiments of the invention, for the same number of optical modules and for the same number of optical fibers contained in the sheath:
Total number of optical fibers Organization of optical modules Conventional cable External diameter Example of cable according to the invention
External diameter 12 1 x 12 fibers 6.1mm 5.6mm 24 2 x 12 fibers 8.4mm 7.2mm 36 3 x 12 fibers 8.4mm 7.2mm 48 4 x 12 fibers 8.4mm 7.4mm 72 6 x 12 fibers 10.2mm 8.7mm 144 12 x 12 fibers 12.0mm 9.7mm 288 24 x 12 fibers 12.6mm 10.3mm 432 6 x 6 x 12 fibers 16.5mm 13.7mm 720 5 x 12 x 12 fibers 18.5mm 15.7mm 864 6 x 12 x 12 fibers 19.5mm 16.0mm

Table 2

Claims (13)

Optical cable (1) comprising:
- a sheath (2) comprising a wall (21) delimiting an internal cavity (22), and
- a plurality of components (3) contained in the internal cavity (22), the components (3) being able to include one or more traction reinforcement(s) (37),
wherein the components (3) contained in the internal cavity (22) comprise a plurality of optical modules (31) extending inside the internal cavity (22), each optical module (31) consisting of a bundle of optical fibers (33), the optical fibers (35) being free within the bundle of optical fibers (33), and one or more wire(s) (34) for holding together the optical fibers (35) of the beam, and one or more additional components (32) extending inside the internal cavity (22),
in which the additional component(s) comprise at least one hydro-inflatable line (32) extending inside the internal cavity (22), the hydro-inflatable line (32) comprising a composition capable of swelling at contact with water, and
in which a ratio between a linear mass of all of the optical fibers (35) of the optical fiber bundles (33) and a linear mass of all of the components (3) extending inside the internal cavity (22 ), excluding tensile reinforcements (37), is greater than or equal to a threshold as defined according to table 1:
Number of optical fibers per optical module Threshold 2 40% 3 49% 4 55% 5 60% 6 63% 7 66% 8 68% 9 70% 10 71% 11 73% from 12 to 17 74% from 18 to 23 78% from 24 to 35 80% from 36 to 47 83% ≥48 84% Table 1. Optical cable according to claim 1, in which the or each wire (34) of an optical module (31) has a linear mass strictly less than 0.0375 grams per meter, preferably less than 0.012 grams per meter. Optical cable according to one of claims 1 and 2, in which the or each wire (34) of an optical module (31) is wound helically around the bundle of optical fibers (33) to hold the optical fibers (35) together. of the beam. Optical cable according to one of claims 1 to 3, in which the or each wire (34) of an optical module (31) is wound helically around the bundle of optical fibers (33) with a winding pitch less than or equal to at 60 millimeters, preferably less than or equal to 35 millimeters. Optical cable according to one of claims 1 to 4, in which the wire or each wire (34) of an optical module (31) is wound helically around the bundle of optical fibers (33) with a greater winding pitch or equal to 15 millimeters. Optical cable according to one of claims 1 to 5, in which the or each wire (34) comprises a plurality of untwisted filaments. Optical cable according to one of claims 1 to 6, in which the or each wire (34) has a breaking strength of at least 0.9 Newtons. Optical cable according to one of claims 1 to 7, in which at least one of the optical modules (31) comprises two wires (34) wound helically around the bundle of optical fibers (33) to hold the optical fibers (35) relative to each other, one of the two wires (34) being wound in an S winding direction around the bundle of optical fibers (33), and the other of the wires (34) being wound in one direction Z-shaped winding around the bundle of optical fibers (33). Optical cable according to one of claims 1 to 8, in which the wall (21) of the sheath (2) is formed in a single single layer of material, and the optical cable (1) does not include a protective envelope between the wall (21) of the sheath (2) and the optical modules (31). Optical cable according to claim 9, comprising two supporting elements (4), embedded in the material of the wall (21) of the sheath (2), and arranged in diametrically opposite positions. Optical cable according to one of claims 1 to 10, in which the wall (21) of the sheath (2) is formed of a material having a melting temperature greater than or equal to 130 degrees Celsius. Optical cable according to one of claims 1 to 11, in which the wall (21) of the sheath (2) is formed of a material having a melting temperature lower than a melting temperature of the material of the wire(s) (34) optical modules (31). Optical cable according to one of claims 1 to 12, in which the internal cavity (22) delimited by the wall (21) of the sheath (2) is unique and contains all of the optical modules (31) of the optical cable ( 2) and additional components (32).