JPS60239702A - Optical fiber cable with hydrogen gas absorption preventing means in optical fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a fiber optic cable for communication that has protective measures against the absorption of hydrogen in the gas phase in an optical fiber. 01 or more optical fibers which can have a detrimental effect on the optical fiber properties, including, inter alia, an increase in attenuation caused by exposure of the optical fiber itself to hydrogen in the gas phase, as well as a deterioration in the mechanical properties. When optical fibers are subjected to the action of hydrogen, regardless of how it is generated (from components inside or outside the cable), the transmission characteristics of the optical fiber often deteriorate.

In practice, the seemingly large damping effect that is initially noticeable as a rule also results in a change in the mechanical properties of the optical fine.

In fact, it has been found that optical fines under such conditions exhibit an increase in attenuation, especially for wavelengths greater than 1 micron, i.e. in the wavelength interval used to transmit the signal. Tests conducted show that once diffused inside an optical fiber, hydrogen itself can absorb energy through an absorption spectrum that includes the wavelength used for the optical signal. This made it possible to confirm that the

Under certain conditions, such a phenomenon occurs as a reversible phenomenon, if hydrogen is allowed to diffuse outside the optical fiber (e.g., by a reduction in the external hydrogen concentration that produced such a phenomenon). If so, the attenuation due to this will also be significantly reduced.

Instead, in other cases, the source of the second attenuation is due to the main component of the optical fiber (e.g., 5lo2) and/or its dopants (e.g., GeO2, P2O5, etc.), and hydrogen diffused into the optical fiber itself. It was also possible to establish that it is related to a chemical reaction that occurs during the process.

The result of such reactions is hydroxyl groups (OH), which also account for absorption at other wavelengths used in transmission.
A group containing

These latter reactions are not reversible, so a corresponding deterioration in optical fiber properties can be expected under all conditions of use.

Parameters that control such phenomena, apart from the chemical composition of the optical fiber, are the partial pressure of hydrogen, temperature, and time to which the optical fiber is exposed.

Optical fibers can come into contact with hydrogen generated during the manufacturing process of the cable or during use of the cable itself. In fact, hydrogen is produced by metals or nonmetals that have absorbed the hydrogen gas during the manufacturing, refining, or finishing process of the constituent materials.
It could be generated by elements present within the cable.

Furthermore, hydrogen can be produced by chemical deterioration due to oxidation of the organic materials that make up the cable, or even by the reaction of moisture present in the cable (either in liquid or gaseous phase) with the metal components that make up the cable itself. It is.

Furthermore, organic materials often used in optical fiber coatings can generate hydrogen through chemical reactions of various nature. The diffusion of hydrogen through various materials increases from metals to polymers to liquids to gases.

Therefore, depending on the type of cable and the environment in which the cable is used, the rate of release of hydrogen generated by the members that make up the cable varies, and hydrogen that is generated on the outside of the cable and permeates through the environment in which the cable is used enters the cable. The rate of absorption also varies.

These different speeds depend on the resulting value of the partial pressure of hydrogen inside the cable as a function of time, i.e. the greater the pressure and the greater the duration, the greater the degree of danger to the culm fiber. become.

In general, in order to establish the partial pressure of hydrogen determined in the transient period and in the final stability conditions in the vicinity of the optical fibers of the cable, in any case the rate of hydrogen production (inside or outside the cable) must be It is necessary to take into account a strict balance between the rate of diffusion of hydrogen through the sheath of the cable, and ultimately through the surrounding objects.

For example, given the service life of fiber optic cables under predictable temperature and pressure conditions, the diffusion rate of hydrogen through metal is so low that a metal sheath of normal thickness is virtually impermeable to hydrogen. You can think of it as something that doesn't exist.

In particular, cables with metallic sheaths, especially if they have small internal spaces, can exhibit short-term and significant attenuation increases due to the hydrogen liberated by the elements within the sheath. The object of the invention is to provide an optical fiber cable with protection against the absorption of hydrogen in the gas phase in the optical fibers present in the cable.

This protective measure is achieved according to the invention by introducing into the cable in a suitable form at least one metallic element capable of absorbing and binding hydrogen.

An optical fiber according to the invention comprising a sheath in which is housed at least one optical device comprising one or more optical fibers.
Inside the sheath, the cable has the first element of the periodic table as a protective measure against the absorption of hydrogen in the gas phase in the optical fiber.
It is characterized in that it includes one or more metals from Group 1, Group 1, Group 2, and Group 2.

Among these metals, those which have proven particularly suitable are as follows. That is, as a form of pure metal,
In group 1, these are lanthanum, in group Ⅰ, titanium, zirconium, hafnium, in group iv, vanadium, niobium, and in group Ⅲ, palladium, and their alloys and/or intermetallic compounds.

In the presence of hydrogen, the elements listed above tend to form solid solutions that can be assimilated into hydrogen compounds that exhibit good stability;
This allows the partial pressure of hydrogen in the cable to be reduced to a value that is in balance with the hydrogen solubility in the element itself.

The use of appropriate amounts of these elements limits the residual pressure value of hydrogen in the cable such that the negative effects of said hydrogen pressure on the properties of the optical fiber, especially the increase in attenuation over the expected lifetime of the cable, are negligible. can do.

It is desirable that the above elements be heat treated under vacuum at a temperature of 1,600° C. or higher.

Indeed, it has been found that, after the treatment, the above-mentioned elements further increase the activity of hydrogen absorption, especially at low hydrogen partial pressures.

These elements may, in some cases, contain some amount of hydrogen and/or other gases absorbed during the manufacturing, refining and finishing processes of the elements themselves, and are also expected to exhibit some level of surface oxidation. .

Both of these phenomena may reduce the effectiveness of protection against hydrogen, but the heat treatment described above at a temperature slightly below the melting temperature provides degassing and eliminates surface oxidation due to sublimation.

EXAMPLES The invention will now be described in more detail with reference to preferred, but non-limiting embodiments shown in the drawings.

A fiber optic cable 1, shown schematically in FIG. 1, consists of an optical device 2 formed by four optical fibers 10 placed on a tensile member 12 and wrapped with one or more tapes 14.

This optical device is held inside a sheath 16, on which are provided other layers, coatings and various structures, schematically indicated in section 20, depending on the type of cable.

The sheath 16 may be an impermeable metal sheath (as in submarine cables, for example) or a plastics material sheath. Inside thereof, a filler having a mechanical function, a water-blocking filler, etc. can be held.

The optical device may include an elongate supporting tensile strength member different from that shown in FIG. In this regard, the sketch shown in Figure 1 is to be considered merely a general overview and is presented solely for the purpose of facilitating an understanding of the invention.

According to a first embodiment shown in FIG. 2 and which is particularly suitable for the protection of cables that already contain a filling material for the purpose of limiting the ingress of moisture in submarine cables, the inside of the outer sheath 16 space (approximately 5 cm per 1 m of cable)
The filler material 21, which occupies about 30% of the total amount (may be about 3%), contains a powder in a dispersed state of one or more elements of Groups 1, V, V, and 2 of the Periodic Table. Desirable materials are lanthanum, titanium, zirconium, hafnium,
Niobium, tantalum and palladium, and their alloys and/or intermetallic compounds. ), depending on the particle size of the powder and also on the shape of the particles.

For cables that have a moisture-blocking filler inside a metal sheath of normal size, e.g.
It has been found that an amount of palladium in powder form in the range of 10 to 100 mg per meter of cable, with a particle size of .

It must be pointed out here that the filler to which the powder is added does not necessarily have to be a moisture barrier filler for submarine cables. This cable can already foresee filling materials for other purposes (e.g. the preparation of more compact structures), to which powder materials can be added later and
Alternatively, the cable could be initially free of filler material, in which case it would obviously be added to contain the powder material.

In a second embodiment, as shown in FIG. 3, the cable includes at least one outer lastomeric or plastomeric sheath 16 disposed within groups I, V, and V of the periodic table. Powders of one or more elements of groups 1 and 2 are dispersed, including lanthanum, zirconium, hafnium, vanadium, niobium, tantalum and palladium, or alloys thereof and/or ) An intermetallic compound is desirable. In this case, the particle size of the dispersed powder is smaller (about several microns) compared to the above-mentioned embodiment. “This embodiment, an embodiment particularly suitable for the protection of optical fibers without metallic outer sheaths used in environments with high hydrogen content, is particularly suitable for the protection of optical fibers without metallic outer sheaths used in environments with high hydrogen content. Requires the use of a mixture containing .1 phr of palladium.

In a third embodiment (FIG. 4), the cable is one or more cables having at least a surface formed of one or more elements of Groups I, V, V, and I of the Periodic Table. The wire 18 is preferably composed of lanthanum, titanium, zirconium, nophnium, vanadium, niobium, tantalum and palladium, or alloys and/or intermetallic compounds thereof. The wire(s) are connected to the tensile strength member (12 in FIG. 1).
or otherwise form one of the components of this tensile strength member, around which the optical fibers would be arranged in a spiral manner. Alternatively, the wire can be attached to a member such as that already present in the cable as shown in FIG.

This embodiment is particularly suitable for cables with large internal free spaces (e.g. on the order of about 50 cm3 per meter of cable), and the volumes and pressures generated in such cables when the metal used is palladium. In order to protect the optical fiber against the action of hydrogen in the fibers, wires with a diameter in the range of the order of 0:02 to 0.2 mm are required.

The wires can also be made of other materials coated on the outside with a sufficiently thick layer of the metals mentioned, since the absorption phenomenon is related precisely to the outer surface of these metals.

In this case the diameter values are clearly different.

FIG. 5 shows yet another embodiment. In this embodiment,
A protective member is obtained by a coating or membrane made of one or more of the above-mentioned metals (and their alloys and/or intermetallic compounds) placed around the optical device(s).

In the cable of FIG. 5, the outer surface of the sheath 16 is metallized with a membrane or coating 19. As already mentioned, one or more of the metals mentioned above and/or their alloys or intermetallic compounds can be used.

The choice of the metal compound used depends on various factors, among others the required cost, hydrogen absorption efficiency of the metal, availability of the metal, metal availability, etc.

However, in the case of certain compounds, the phenomenon of improved effectiveness has been found, especially in the form of wires (particularly noticeable in the mixture of niobium and zirconium used as a metallizing layer). The properties are probably due to the fact that, apart from the fact that both these metals are absorbers of hydrogen, zirconium combines very easily with oxygen and thus protects niobium.

According to a fifth embodiment shown in FIG. 6, the cable is wrapped with plastic tape or metal tape (
at least one of the previously mentioned elements and/or their Contains layers or films of alloys and/or intermetallic compounds.

This embodiment, which is more suitable for the protection of cables that may be attacked by external hydrogen sources, can be wound with a short pitch on an optical device of normal dimensions to provide protection for optical fibers under normally expected conditions of use. In the case of an external hydrogen source requiring a palladium layer of thickness in the range 1 to 20 microns in the applied tape, it is desirable to orient the active layer outwardly.

In conclusion, it should be clearly understood that the different embodiments illustrated in the text are not mutually exclusive, but are in fact compatible and can be advantageously co-operated in the same cable. It is.

Although the invention has been described with particularity to certain embodiments and particular cable constructions, it is not intended to be limited to such embodiments and may be extended to cover various changes and modifications that will be apparent to those skilled in the art. It is something that should be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of the innermost part of the optical fiber cable of the present invention, and FIGS. 2 to 6 are cross-sectional views showing the inner side of the optical fiber cable according to various embodiments of the present invention. 0 1... Optical fiber cable, 2... Optical device, 10... Optical fiber, 12...
- Tensile strength member, 14. Tape, 16... Sheath part,
18...Wire, 19...Coating, 21...
・Filling material. Agent: Patent attorney Kyogo Yuasa - 0 (one outsider 1 Figure 5 Figure 6)

Claims (1)

[Claims] (1) An optical fiber comprising a sheath housing at least one optical device containing one or more optical fibers.
In the cable, as a protective measure to prevent absorption of hydrogen in the gas phase in the optical fin (group Ⅰ of the periodic table,
Optical fiber cable 0 characterized in that one or more metals from Group V, Group V, and Group (I) are provided inside the sheath portion (2) Lanthanum and titanium, in which each of the metals is present as a pure metal. , zirconium, naufnium, vanadium, niobium, tantalum and palladium, or alloys thereof, or intermetallic compounds. (3) Claim 1 or 2, characterized in that the metal is present in the cable in the form of a powder material.
Fiber optic cables as described in Section. (4) The optical fiber cable according to claim 3, wherein the powder material is dispersed within a filler material held within the sheath. (5) The optical fiber cable of claim 4, wherein the filler is a moisture barrier material in the cable. (6) Claim 5, wherein the sheath is made of metal, and the cable is a submarine cable.
Fiber optic cable as described in section. (7) The optical fiber cable according to claim 3, wherein the sheath is made of plastic containing the powder material in a dispersed state. (8) The optical fiber according to claim 7, characterized in that the powder material has a particle size smaller than 10μ.
cable. (9) In the cable, the metal is present in the form of a wire whose surface is formed at least by one or more such metals, their alloys and/or intermetallic compounds. The optical fiber cable according to item 1 or 2. 00) said wire is at least partially connected to said tape. 10. The optical fiber table according to claim 9, which constitutes a tensile strength member of a fiber optic fiber. 01) The optical fiber cable according to claim 9, wherein in the cable, the metal layer is present in the form of a single layer. (12I) A fiber optic cable Q according to claim 2, characterized in that said membrane or layer is affixed on a ribbon-like support that is continuously wrapped around said optical device ( 13) An optical fiber cable according to claim 12, characterized in that the ribbon-shaped support is made of plastic. 04) The optical fiber cable according to claim 12, characterized in that the ribbon-shaped support is made of a metallic material. The optical fiber according to claim 13
cable. (1) Claim 13, characterized in that the ribbon-shaped support is made of a plasticized metallic material.
Optical fiber cable as described in section. (L6) that said material layer is radium with a thickness in the range of 1 to 20 μm applied on a tape continuously wrapped in a pinch around said optical device; 13. The optical fiber cable of claim 12. (171) A fiber optic cable according to claim 11, wherein said membrane or layer is affixed on the outer surface of said sheath.