FR2563635A1 - OPTICAL FIBER CABLE WITH PROTECTION AGAINST THE ABSORPTION OF GASEOUS HYDROGEN BY OPTICAL FIBERS - Google Patents

Abstract

THE INVENTION RELATES TO OPTICAL FIBER CABLES. IN A CABLE FOR TELECOMMUNICATIONS WITH OPTICAL FIBERS, THESE FIBERS 10 ARE PROTECTED AGAINST THE ABSORPTION OF HYDROGEN GAS BY THE ADDITION TO THE CABLE OF ONE OR MORE ELEMENT (S) BELONGING TO GROUPS III, IV, V, VIII OF THE PERIODIC CLASSIFICATION. MAIN APPLICATIONS: FIBER OPTIC CABLES FOR TELECOMMUNICATIONS, IN PARTICULAR SUBMARINE CABLES.

Description

The present invention relates to a cable for

  optics for telecommunications protected against

  the absorption of hydrogen gas by the fibers.

  The absorption of hydrogen has negative effects on the properties of the fibers, inter alia, the increases in attenuation that occur as a result of

  the exposure of the fibers to gaseous hydrogen and a

  gradation of mechanical properties.

  In cables comprising one or more

  optic (s), there is sometimes a deterioration

  the transmission properties of the fibers in the

  where they are subject to the action of hydro-

  gene, regardless of how it was

  (whether by elements external to the cable

  only by internal elements of the cable).

  In fact, the mechanical characteristics of the fiber are also influenced although, normally, it is the macroscopic effects of the increase.

  the attenuation that we observe first.

  The fibers which come to be in such conditions have indeed an increase

  attenuation, in particular for the longer wavelengths

  at one micron, that is, in the range of

  wavelengths used for signal transmission.

  Experiments carried out by the plaintiff

  have established that a first source of growth

  mitigation is the hydrogen itself.

  which, once diffused in the fiber, is able to absorb energy with an absorption spectrum which includes the wavelengths used for the optical signal.

  Under certain conditions, this phenomenon is re-

  and the attenuation due to this phenomenon is reduced

  also appreciable if hydrogen has the possibility

  the ability to diffuse outward from the fiber (for example, as a result of

  of the hydrogen that gave rise to the pheno-

leads).

  In other cases, on the contrary, it has been possible

  a second source of attenuation is to be attributed to chemical reactions that occur between the main constituents of the fiber (eg SiO2)

  and / or its dopants (for example GeO2, P205, etc.) and hy-

  which has diffused into the fiber.

  The result of these reactions is the formation of groups which contain the hydroxyl radical (OH) and which are responsible for the absorption at the level of others.

  wavelengths also used for the transmission of

  if we. These last reactions are irreversible and can therefore provide for a corresponding deterioration of the properties of the fiber under all operating conditions. The parameters that control this phenomenon are, apart from the chemical composition of the fiber, the partial pressure of hydrogen to which the fiber is

  exposed, the temperature and, of course, the weather.

  The fiber can come into contact with the hydrogen

  generated during the production process

  cable during the use of the cable itself.

  me. Indeed, hydrogen can be emitted by

  metallic or non-metallic elements in the cable

  and who have absorbed this gas during the operations of production, refining or finishing of the constituent materials.

  Hydrogen can also be generated during

  the possible chemical degradation by oxidation of the organic materials constituting the cable or by a reaction of the water (in the liquid state as well as vapor) possibly present in the cable with

  constituent metallic elements of the cable.

  Finally, some organic materials

  also used in the coating of

  are able to release hydrogen under the ef-

  fet of chemical reactions of various natures. The dissemination

  hydrogen through the various

  Riels occurs at a rate that increases from metals to polymers to liquids and gases.

  Therefore, depending on the type of cable and the type

  environment in which it is used, it is observed that

  different rates of release of hydrogen

  the constituent elements of the cable and

  cable absorption rates of any hydrogen produced externally to this cable and which

  crosses the environment of use.

  The value of the partial pressure of the hydrogen

  the inside of the cable, which will be a function of time, depends on these different speeds; more pressure and

  the duration is large, the greater the level of risk

only for fibers.

  In general, we will have to take into consideration

  for each case, a detailed assessment of the speed of pro-

  hydrogen production (of domestic origin as well

  outside the cable sheath), the speed of

  fusion of hydrogen through the cable sheath and, finally, the rate of diffusion of hydrogen to

  through the surrounding environment, in order to establish the

  their hydrogen partial pressure which will be established during the transient and possibly in

near the fibers of the cable.

  For example, given the life expectancy

  fiber optic cable under the conditions laid down in

  temperature and pressure, the speed of

  Hydrogen fusion through metals is so low that metal sheaths of usual thickness

  can be considered virtually impenetrable

hydrogen.

  In particular, cables having a metal sheath, and especially if their interior volume is reduced, can rapidly exhibit high levels of increased attenuation under the action of

  the hydrogen released by the elements located in the

of the sheath.

  The object of the present invention is to provide a fiber optic cable provided with protection against the absorption of hydrogen gas by the optical fibers

present in the cable.

  This protection is obtained according to the invention

  by introducing appropriately into the cable

  at least one metallic element which is able to absorb

  hydrogen and combine with it.

  The optical fiber cable according to the invention, which comprises a sheath in which is housed at least

  an optical core formed of one or more optical fiber (s)

  that (s), is characterized in that it includes, within the

  said sheath, one or more metals of the groups

  III, IV, V and VIII of the Periodic Table, as a protection against the absorption of hydrogen

gaseous by the optical fibers.

  Among these metals, those that have been revealed

  particularly appropriate are the following:

  thane for group III, titanium, zirconium, hafnium for group IV, vanadium, nobium for group V and palladium for group VIII, under

  form of pure metals or alloys or alloys

  intermetallic poses of these metals.

  In the presence of hydrogen, the abovementioned elements tend to form hydrid-like interstitial solid solutions, which are provided with good

  stability, and this makes it possible to reduce the partial pressure

  the hydrogen in the cable to values that are

  in equilibrium with the solubility of hydrogen in

said elements.

  By using appropriate amounts of these elements, it is possible to limit the pressure values

  residual hydrogen in the cable so as to

  negligible effects of the said pressure

  of hydrogen on the properties of the fibers and in particular

  to link their mitigation increments to

  limits of the expected life of the cable.

  The aforementioned elements are preferably subjected to heat treatment under vacuum at temperatures of a few hundred degrees Celsius, before being

  used in the manufacture of the cable.

  In some cases, for example, for nobium, it has been observed that it is useful to raise the temperature

  treatment above 1,600 C.

  It has been found that after these

  the aforementioned elements are more active in the ab-

  hydrogen sorption, especially at low values of

the partial pressure.

  It is assumed that these elements may in some

  some cases already contain a certain amount of hydrogen

  ne and / or other gases absorbed during manufacturing operations, purification and finishing of the elements and

  have a certain level of superficial oxidation

cial.

  These two phenomena could reduce the efficiency

  cited the protection of fibers against hydro-

  gene and the aforementioned heat treatments performed at temperatures close to but below the melting temperature determine degassing

  and / or the elimination of superficial oxidation by

  blimation. The figures of the appended drawing, given solely by way of non-limiting example, will make it clear how the invention can be implemented. On this drawing,

  FIG. 1 schematically represents the structure

  ture of the innermost part of a typical example of fiber optic cable; Figures 2 to 6 show schematic sections of the interior of an optical fiber cable

  according to different embodiments of the invention.

  The fiber optic cable shown schematically

  Figure 1 comprises an optical core 2

  of four optical fibers 10 gathered around an element

  tensile strength and assembled into a

  by one or more ribbon (s) 14.

  The optical core is contained inside

  of a sheath 16 above which are provided from

  layers, coatings or structures that differ

  the type of cable and which are schematically

part 20.

  This sheath 16 may be an impervious metallic sheath (for example in an underwater cable) or a plastic sheath. Inside this sheath, the cable may contain a filling having

  mechanical functions, an impervious sealing material

  posing to water seepage, etc.

  The optical core may include elements

  longitudinal supports, as well as other

  tensile strengths different from those previously mentioned

  above and the fibers may be of the structural type

  loose ture as well as tight-structure type. AT

  reading of what has been stated above, the repre-

  of Figure 1 should be considered as gener-

  that and schematic and as given only to make

  to understand the invention more easily.

  According to a first embodiment

  shown in Figure 2 and particularly well

  required to protect a cable already provided with a jam to limit possible penetrations of water, as in the case of submarine cables, the stuffing material 31 which fills the voids located under the outer sheath 16 (voids which can be of the order of 5 cm3 per meter of cable) contains a dispersion of powders of one or more element (s) of groups III,

  IV, V and VIII of the Periodic Table, among-

  which lanthanum, titanium, zirconium, hafnium, vanadium, niobium, tantalum, palladium or the alloys of these metals are preferably chosen

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  or their intermetallic compounds.

  The quantity of powders introduced into the material

  Depending on the type of cable, its geometry and the element (or elements) chosen from those mentioned above and whose powders are made, as well as the particle size of the

  powders and the shape of their grains.

  In the case of a cable of usual dimensions

  equipped with a stuffing and enclosed in a metallic sheath

  It has been observed, for example, that between 10 and 100 mg of palladium powder per

  cable, with particles having

  between 10 and 100 microns, is sufficient to protect

  handle the fibers of hydrogen volumes and pressures

  which emerge in this type of cable.

  It should be noted that the filling

  which powders are added may not be the material

  jamming of a submarine cable. The cable could

  already include filling for other functions

  (for example compaction), to which the powders would be added, or alternatively, the cable could initially be empty and, in this case,

  the last would be specially added to contain the

ders.

  In a second embodiment,

  shown in Figure 3, the cable includes at least one

  outer member 16 made of elastomeric material or plastomer

  in which are dispersed powders of one or more

  the elements of Groups III, IV, V, VIII of the Periodic Table, inter alia, preferably

  lanthanum, titanium, zirconium, hafnium,

  nadium, niobium, tantalum, palladium or alcohols

  binding or intermetallic compounds of these metals.

  The particle size of the dispersed powders is in this case smaller (of the order of one micron) than in the previous case. This embodiment, which is particularly well adapted to protect cables to

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  optical fibers without an outer metal sheath

  re and who work in environments rich in

  hydrogen, for example, requires the adoption of

  outer sheath of the mixtures of at least 0.1 part of palladium per 100 parts of resin. In a third embodiment (Figure 4), the cable comprises one or more wire (s) 18 formed (s),

  at least superficially, one or more

  group III, IV, V and VIII of the classifica-

  periodic, among other things, and preferably

  thane, titanium, zirconium, hafnium, vanadium, niobium, tantalum, palladium, or an alloy

  intermetallic compound of these metals.

  The wire or wires can form the element of

  traction (12 in figure 1) or one of the

  of the tensile element and, in these cases, the fibers are wired around this wire or these

  son. As a variant, said wire may be added to the elements

  already present in the cable, as has been shown

in Figure 4.

  This embodiment is particularly

  suitable for cables with a large

  me free inside (for example, of the order of 50 cm3 per meter of cable) and, in the case where the metal used

  is palladium, it requires a wire with a diameter

  between 0.02 and 0.2 mm to protect the

  of the action of hydrogen in the quantities and

  the pressures that emerge in this type of cable.

  Since the absorption phenomenon does not

  Concerned that the outer surface of the considered metals, the son can be made of other materials and be externally coated with a sufficient layer of the aforementioned metals. In this case, the values of the diameters

are obviously different.

  Figure 5 shows another variant of reali-

  in which the protective elements are obtained

  held with a coating or film of a

  or more of the aforementioned metals (or their alloys)

  intermetallic compounds or compounds), expected around

nucleus or optical nuclei (s).

  In the cable of Figure 5, the outer surface

  top of the sheath 16 is metallized with a film

  19. As already mentioned, it is possible to use

  to read two or more of the aforementioned metals or

  their alloys or intermetallic compounds.

  The choice of the combination depends on different

  factors, among others, the cost, the effectiveness of the ab-

  sorption of hydrogen, availability,

bility, etc.

  However, it has been observed that some combinations of

  have improved efficiency as is the case, in particular, for a mixture of niobium and zirconium used in the form of wires or in the form of

  layers of metallization. The excellent performance

  these of this mixture probably derive from the fact that,

  these two metals are hydrogen absorbers, zirconium combines very easily with oxygen,

thus safeguarding the niobium.

  According to a fifth embodiment,

  6, the cable comprises a layer or film of at least one of the aforementioned elements or of

  their alloys or intermetallic compounds, this

  film or film being deposited on a plastic tape or on a metal ribbon (for example

  steel, Al, Cu, etc.), or on a metal tape.

  plasticized (eg Al coated with polyethylene

  lene) which constitutes the taping 14 arranged around the

optical core of the cable.

  This embodiment, which is adapted,

  others, to protect the cables in which the

  can enter from the outside, requires

  a palladium layer thickness deposited between 1 and 20 microns, on ribbons which are wound

  with a short step on the optical core of dimensions

256 3 55

  to achieve the protection of fibers in

  normally predictable conditions.

* In the case of external sources of hydrogen,

  the active layer with respect to hydrogen should be

  is directed outwards. Finally, it goes without saying that the different

  represented embodiments are not incompatible with

  between them but that they can coexist on the contrary and be used to advantage

  complement others in the same cable.

  It goes without saying that various modifications

  be made to the embodiments that come

  to be described solely as examples,

  by substituting the equivalent technical means,

  without departing from the scope of the invention.

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R EV E ND IC A T IO N S

  1 - Optical fiber cable including a gimp

  within which is housed at least one nucleus

  an optical fiber formed of one or more optical fibers,

  characterized in that it comprises, within said sheath (16), one or more metals of groups III, IV, V and VIII of the Periodic Table, as a protection against the absorption of gaseous hydrogen by

optical fibers.

  2 - Cable according to claim 1, characterized

  in that said metals are respectively lanthan-

  ne, titanium, zirconium, hafnium, vanadium, niobium, tantalum and palladium,

  form of pure metals or alloys or

  intermetallic metals of these metals.

  3 - Cable according to one of claims nl and

  2, characterized in that said metals are present

in the form of powders.

  4 - Cable according to claim 3, characterized

  in that said powders are dispersed in a

  pleating contained within said sheath (16).

  Cable according to Claim 4, characterized

  in that the filling is the stuffing (21) of the cable.

  6 - Cable according to claim 5, characterized in that said sheath is metallic and that the cable

is an underwater cable.

  7 - Cable according to claim 3, characterized

  in that said sheath (16) is made of a plastic material

  tick containing a dispersion of said powders.

  8 - Cable according to claim 7, characterized

  in that said powders have smaller dimensions than

to 10 microns.

  9 - Cable according to one of claims 1 and

  2, characterized in that said metals are present in the cable in the form of wires (18) formed, at least superficially, of one or more of the aforementioned metals, or alloys or intermetallic compounds

of these metals.

  Cable according to claim 9, characterized

  characterized in that said wires constitute at least in part the resisting element (12) for pulling the cable.

  11 - Cable according to one of claims 1 and

  2, characterized in that said metals are present

  cable in the form of films or

perposées.

  12 - Cable according to claim 2, characterized

  in that said films or layers are deposited

  on a ribbon-shaped support (14) which is wound

  then around the optical core.

  13 - Cable according to claim 12, characterized

  in that said ribbon carrier (14) is in

plastic material.

  14 - Cable according to claim 13, characterized

  in that said ribbon carrier (14) is

a metallic material.

  15 - Cable according to claim 13, characterized

  in that said ribbon carrier (14) is

  a plasticized metal material.

  16 - Cable according to claim 12, characterized

  in that said plastic layer is made of

  palladium, deposited to a thickness of

  be 1 and 20 microns, on a ribbon (14) which is then

  wrapped around an optical core with a short pitch.

  17 - Cable according to claim 11, characterized

  in that said film or layer (19) is deposited

  on the outer surface of said sheath (16).