CA1251075A - Optical fiber and cable with hydrogen combining layer - Google Patents
Optical fiber and cable with hydrogen combining layerInfo
- Publication number
- CA1251075A CA1251075A CA000480142A CA480142A CA1251075A CA 1251075 A CA1251075 A CA 1251075A CA 000480142 A CA000480142 A CA 000480142A CA 480142 A CA480142 A CA 480142A CA 1251075 A CA1251075 A CA 1251075A
- Authority
- CA
- Canada
- Prior art keywords
- optical fiber
- set forth
- fiber structure
- layers
- powder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000013307 optical fiber Substances 0.000 title claims abstract description 49
- 239000001257 hydrogen Substances 0.000 title claims abstract description 46
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 46
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 45
- 239000000835 fiber Substances 0.000 claims abstract description 37
- 229910052751 metal Inorganic materials 0.000 claims abstract description 35
- 239000002184 metal Substances 0.000 claims abstract description 35
- 239000000843 powder Substances 0.000 claims abstract description 23
- 238000010521 absorption reaction Methods 0.000 claims abstract description 7
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 6
- 239000000956 alloy Substances 0.000 claims abstract description 6
- 230000000737 periodic effect Effects 0.000 claims abstract description 3
- 239000010410 layer Substances 0.000 claims description 18
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 14
- 239000000463 material Substances 0.000 claims description 11
- 239000011241 protective layer Substances 0.000 claims description 10
- 239000011347 resin Substances 0.000 claims description 8
- 229920005989 resin Polymers 0.000 claims description 8
- 229910052763 palladium Inorganic materials 0.000 claims description 7
- 229920002379 silicone rubber Polymers 0.000 claims description 6
- 239000004945 silicone rubber Substances 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 4
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 3
- 229910052758 niobium Inorganic materials 0.000 claims description 3
- 239000010955 niobium Substances 0.000 claims description 3
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 3
- 230000003287 optical effect Effects 0.000 claims description 3
- 239000004033 plastic Substances 0.000 claims description 3
- 229910052726 zirconium Inorganic materials 0.000 claims description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 2
- 229910052747 lanthanoid Inorganic materials 0.000 claims description 2
- 150000002602 lanthanoids Chemical class 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 229910052715 tantalum Inorganic materials 0.000 claims description 2
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 2
- 229910052719 titanium Inorganic materials 0.000 claims description 2
- 239000010936 titanium Substances 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 239000000945 filler Substances 0.000 claims 2
- 229910052735 hafnium Inorganic materials 0.000 claims 1
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims 1
- 150000002739 metals Chemical class 0.000 abstract description 14
- 229910000765 intermetallic Inorganic materials 0.000 abstract description 5
- 238000000576 coating method Methods 0.000 description 33
- 239000011248 coating agent Substances 0.000 description 29
- 239000011253 protective coating Substances 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000006185 dispersion Substances 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- 230000036961 partial effect Effects 0.000 description 4
- 239000004677 Nylon Substances 0.000 description 3
- 238000005253 cladding Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 230000006870 function Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229920001778 nylon Polymers 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000499 gel Substances 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000011368 organic material Substances 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000001464 adherent effect Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000002144 chemical decomposition reaction Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 238000007730 finishing process Methods 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- 150000004678 hydrides Chemical class 0.000 description 1
- TUJKJAMUKRIRHC-UHFFFAOYSA-N hydroxyl Chemical compound [OH] TUJKJAMUKRIRHC-UHFFFAOYSA-N 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 230000005226 mechanical processes and functions Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 235000019271 petrolatum Nutrition 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000009993 protective function Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000002829 reductive effect Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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
- G02B6/4402—Optical cables with one single optical waveguide
-
- 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
- G02B6/4429—Means specially adapted for strengthening or protecting the cables
- G02B6/44382—Means specially adapted for strengthening or protecting the cables the means comprising hydrogen absorbing materials
Abstract
ABSTRACT OF THE DISCLOSURE
An optical fiber structure in which there is at least one layer around the fiber signal transmitting core, such layer being formed of, or containing a powder of, a hydrogen gas absorbing metal or metals from Group III, IV, V or VIII of the periodic table, or alloys or intermetallic compounds of such metals, to absorb hydrogen and for protecting the core with respect to hydrogen absorption.
An optical fiber structure in which there is at least one layer around the fiber signal transmitting core, such layer being formed of, or containing a powder of, a hydrogen gas absorbing metal or metals from Group III, IV, V or VIII of the periodic table, or alloys or intermetallic compounds of such metals, to absorb hydrogen and for protecting the core with respect to hydrogen absorption.
Description
~ ~.?~ ~ 5 OPTICAL FIBER AND cAsLE WITH HYDROGEN COMBI~IING LAYER
The present invention relates to the protection of an optical fiber with respect to the absorption of gaseous hydrogen, particularly, when the optical fi~er is incorporated within a cable.
In cables comprising one or more opticalfibers, there is found, at times, a deterioration in the transmission properties of the fibers if the fibers are subjected to the action of hydrogen however such gas is generated, e.g. by members which are either outside or inside the cable.
In actual fact, even the mechanical characteristics of the fiber are modified by such hydrogen although, as a rule, the macroscopic effects of increased attenuation are the first to become apparent. In fact, the fibers affected by hydrogen show an increase of attenuation for the wavelengths higher than 1 micron, i.e. at the wavelengths utilized for transmitting the signals.
Generally, the optical fibers comprise a glass structure formed with a cladding and a core of the "step index", of "graded index" type,, but they may have even other structures, and a primary coating is applied to the fiher immediately after its formation, for the purpose of preventing the fiber from having any direct contact with the outside environment. Over said primary coating, there are applied other protective coatings, for example, constituted by a layer of silicone rubber and by a more rigid layer or tube made, for example, of nylon.
An optical fibers cable generally comprises one or more optical fibers, enclosed in a sheath, together with one or more traction-resistant members. Said sheath, which can either be metallic or not, is, in its turn, surrounded by other mechanical 3. ~ ~
members such as armorings, coverings, etc.
Tests which have been carried out have demonstrated that a primary cause of attenuation in the optical fibers in-corporated in a cable is constituted by the hydrogen which, once it becomes diffused inside the fiber, is capable of absorbing energy in a spectrum comprising the wavelengths utilized for the optical signals.
Under particular conditions, this phenomenon is reversible, and the attenuation can even be considerably reduced if it is possible for the hydrogen to diffuse towards outside the fiber, for example, due to a lowering of the outside concentration of hydrogen which caused the phenomenon.
On the other hand, in other cases, it has been possible to establish that a second cause of attenuation must be attributed to chemical reactions taking place between the main constituents of the fiber, for example, Si02 and/or its dopants Ge02, P205, etc., and the hydrogen which are contained inside the fiber itself.
The result of these reactions is the formation of groups containing the hydroxyl radical ~OH) which are responsible for the absorption at the wavelengths which are also used for the transmission of signals. These latter reactions are irreversible, and hence, there is a ~orxesponding deterioration of the fiber properties which can be expected under all conditions of use.
The parameters which control these phenomena are, apart from the chemical composition of the fiber, the partial pressure of the hydrogen to which the fiber is exposed, the temperature and, of course, time.
The fiber can come into contact with the hydrogen generated inside the cable, either during the cable manufacturing process, or else during the operation of the cable itself. As a matter of fact, the hydrogen can be generated by metallic or ~ r-non-metallic members present in the cable which have absorbed said gas during the manufacturin~, treating or finishing processes for the materials forming the cable.
The hydrogen can also be generated because of the eventual chemical degradation, through the oxidation, of the organic materials forming the cable, or else through the reaction of the water, ei-ther in a liquid state or as vapor and eventually present in the cable, with the metallic members of the cable in-cluded in the cable structure.
Certain organic materials used in the fiber cladding, are capable of producing hydrogen due to chemical reactions of various natures. It has been found that one hydrogen source is constituted by the protective coatings themselves, and in paxti-cular, when the protective coating is the silicone rubber. As a theory, it is assumed that when the cross-linking process is pro-longed in duration, there is a liberation of hydrogen at the fiber surface. The spreading of the hydrogen takes place towards the fiber, as well as towards outside of the protective coating but does not cause any appreciable phenomena on the outside of the coating because, in this case, the hydrogen becomes dispersed in the surrounding environment.
Nevertheless, when the fiber is situated within a closed cable and without there being sufficient free space around the fiber, the hydrogen concentration can achieve relatively high values which cause its appreciable diffusion, even towards the fiber itself, aided by the fact that the cladding, from which the hydrogen is developed, is very near to the fiber.
The diffusion of the hydrogen through the varlous materials varies with the material and is the lowest with metals but increases, successively with polymers, liquids and gases.
Hence, depending upon the type of cable and upon the environment ~ ~3 wherein it is utilized, there may be several rates for the emission of the hydrogen produced by the cable members. There-fore, there also are diverse rates of absorption, on the part of the cable, of the hydrogen eventually produced outside it and which permeates the operating ambient. The value of the partial pressure of the hydrogen inside the cable depends on these various rates and is a function of the time, because the greater the pressure and the duration are, the greater the level of risk for the fibers will be.
Given the service lifetime of an optical fibers cable, under foreseeable temperature conditions, the diffusion rate of the hydrogen through the metals is so low -that metallic sheaths of a normal thickness can be considered as being prac-tically impermeable to the hydrogen. In particular, the cables having metallic sheaths, especially if they have a small space inside them, are cables which have, in a short time and at high levels, increases in attenuation due to the hydrogen which is liberated from the elements inside of the sheath.
The object of the present invention is to provide an optical fiber which is protected against the absorption of gas-eous hydrogen which may be present in the cable containing the fiber. Such protectiqn is obtained, according to the invention, by providing around the outermost layer of the fiber itself, one or more coatings containing metals which are capable of combining with the hydrogen and which form a barrier in corres-pondence to said coating.
According to the invention, an optical fiber, having at least one protective coating, is characteri~ed by the fact of including, in at least one of said protective coatings, at least one powder of a metal selected ~rom the ~roups III, IV, V, VIII of the periodic system as a protection against the ab-sorption of gaseous hydrogen on the ~lq~ 5 part of the fiber.
The metals which have proved to be particularly suitable are lanthanides for Group III; titanium, zirconium and hanium for Group IV; vanadium, niobium and tantalum for Group V; and palladium for Group VIII, in the form of pure metals, their alloys or intermetallic compounds.
In the presence of hydrogen, the identified elements tend to form solid interstitial solutions which are similar to hydrides having a good stability, and this allows Eor a reduction in the partial hydrogen pressure in the cables to values which counterbalance the solubility of the hydrogen in the members themselves.
Preferably, the identified elements are suhjected to ~
thermal treatment, under vacuum, at temperatures of some hundreds of degrees centigrade, prior to being utili~ed in cable pro-duction, for the purpose of eliminating any hydrogen which may have been absorbed, and/or the combined oxygen.
Other objects and advantages of the present invention will be apparent from the following detailed description of the presently preferred embodiments thereof, which description should be considered in conjunction with the accompanying drawings in which:
Fig. 1 is a schematic cross-section of an optical fiber provided with a primary metallic coating of the invention;
Fig. la is a schematic cross-section of an optical fiber provided with a metallic coating of the invention around a primary coating on the fiber;
Fig. 2 is a schematic cross-section of an optical fiber provided with a primary insulation-metal powder coating of the invention;
Fig. 3 is a schematic cross-section of an optical fiber provided with a primary coating and a secondary coating of the invention;
Fig. 4 is a schematic cross-section of an optical fiber provided with a primary coating and a secondary coating of the invention, between which there is inter-posed a cushioning layer; and Fig. 5 is a schemat:ic cross-section of a coated optical fiber loosely enc:Losed by a small tube, the space between the tube and the fiber being filled with a gel containing metal powder according to the invention.
With reference to Fig. 1, an elementary optical fiber comprises a glass portion 1 of any type whatsoever, i.e. 'tstep index", "graded index" or other types, and a primary coating 2 adjacent and contacting the portion 1, the coating 2 having the function of protecting the fiber from the outer environment.
According to a first embodiment of the invention, the glass portion 1 is protected by a metallizing layer formed by one or more of the materials described. Said layer can constitute the primary coating 2 shown in Fig. 1 in close contact with the glass structure of the optical fiber. Thus, there is obtained a fiber where the primary coating is of the metallic type and which, at the same time, performs the mechanical function as well as the function of safeguarding against the absorption of hydrogen by the environment surrounding the fiber, during operation.
According to a variation shown in Fig la, th~ metal-lizing layer 2 is applied immediately over the usual primary coating la made oE cross-linked resin. This construction is utilizable whenever it is not possible or convenient to modify the plant ~or producing the fiber so that the protective coating is applied immediately after drawing the optical fiber to the ~l2~ 75 desired dimensions.
As a further variation, the coating la may be one or more coatings described hereinafter.
In accordance with a further embodiment, illustrated in Fig. 2, the primary coating 2a, made of acrylic resin or of some other suitable material, contains a dispersion of the powders of one or more of the cited metals, or their alloys or inter-metallic compounds. I'his permits the incorporation of the pro--tective coating in a conventional manufacturing process.
A further embodiment (Fig. 3) adds the metallic powders to the resin coating 3 immediately surrounding the primary covering la. This coating 3 is typically made of silicone rubber and, as explained previously, silicone rubber can become a parti-cularly dangerous source of hydrogen. The presence of the metals in this coating 3 effectively neutralizes the hydrogen which is generated, even before it can diffuse towards the fiber.
The optical fiber illustrated schematically in Fig. 4, is a further embodiment of the invention which has a dispersion of metallic powders in the secondary coating 4 which is con-stituted, for example, out of nylon or some other thermoplastic polymer.
In the embodiments described, the particles of the powders have dimensions which are, preferably, less than 10 microns, and the quantity of the powders per length unit of the optical fiber is selected to achieve a concentration within the range of from 0.1 to 10 phr (parts per hundred of resin) in the resin. The range of 0.1-10 phr is preferred, but can vary de-pending on the thickness of the coating. The metal content of the coating should be at least 0~01 g./m.
It must be kept in mind that the protective function, according to the invention, is accomplished in various ways, 3l7 depending upon the coating in which the metals are incorporated~
More precisely, the presence of a protective layer very close to the optical fiber, protects the la-tter mainly against the hydrogen generated in the innermost protective coatings, while an outer protective coating, for example, around the silicone rubber, provides mainly a protection from the hydrogen derived from the cable elements.
In view of what has been stated, as other factors depending upon the structure and the foreseeable conditions of operation of the cable, it will be apparent that the several pre-viously described different embodiments can be combined in a same optical fiber.
A further embodiment of the invention, which is il-lustrated in Fig. 5 r comprises an optical fiber 1 having a primary coating la enclosed by a small tube 9 of plastic material, the inner diameter of which is greater than the outer diameter of the fiber 1. The fiber 1 may be provided with the usual coatings for constituting an optical fiber of the loose type. For this type of fiber, which may have non-adherent coverings, the protection can be realized by having coatings such as those de-scribed previously and/or by providing inside the small tube 9 a gel 8, such as petroleum jelly or a silicone grease, containing a dispersion of powders of the described metals or their alloys or intermetallic compounds.
As an alternative, combined or not with the immediately preceding embodiment, the material that constitutes the small tube 9 may contain a dispersion of powders of the described metals or of their alloys or intermetallic compounds.
In the various embodiments, the content of the metal selected from one of -the Groups III, IV, V and VIII depends upon the amount of hydrogen which it is expected will be released or generated during the life of a cable containing the fiber. There-fore, the metal content depends on such things as cable size, materials, treatments, environment, etc. It is desirable to keep the hydrogen partial pressure content within the cable below 1-2 mm. Hg. The metal content should be the minimum amount determined to be necessary plus a small additional amount for safety reasons. The upper limit of the metal content depends upon cost and the effect oE the metal content on the physical properties of a coating incorporating the metal in powder form.
Palladium is,a preferred metal because it can be used in smaller amounts. Although other metals are less expensive, the niobium content, for example, should be of the order of ten times, by weight, the palladium content and the zirconium content, for example, should be of the order of one hundred times, by weight, the palladium content.
The content of palladium should not be less than lOntg/m.
of cable. A preferred range is between from 15 to 150 mg./m. of cable. Preferably, the palladium particle size is not greater than 10 microns when the material in which it is admixed is nylon to avoid significant alteration of the physical properties of the coating. The latter considerations apply when other metals are used.
Although preferred embodiments of the present invention have been described and illustrated, it will be apparent to those skilled in the art that various modifications may be made without departing from the principles of the invention.
The present invention relates to the protection of an optical fiber with respect to the absorption of gaseous hydrogen, particularly, when the optical fi~er is incorporated within a cable.
In cables comprising one or more opticalfibers, there is found, at times, a deterioration in the transmission properties of the fibers if the fibers are subjected to the action of hydrogen however such gas is generated, e.g. by members which are either outside or inside the cable.
In actual fact, even the mechanical characteristics of the fiber are modified by such hydrogen although, as a rule, the macroscopic effects of increased attenuation are the first to become apparent. In fact, the fibers affected by hydrogen show an increase of attenuation for the wavelengths higher than 1 micron, i.e. at the wavelengths utilized for transmitting the signals.
Generally, the optical fibers comprise a glass structure formed with a cladding and a core of the "step index", of "graded index" type,, but they may have even other structures, and a primary coating is applied to the fiher immediately after its formation, for the purpose of preventing the fiber from having any direct contact with the outside environment. Over said primary coating, there are applied other protective coatings, for example, constituted by a layer of silicone rubber and by a more rigid layer or tube made, for example, of nylon.
An optical fibers cable generally comprises one or more optical fibers, enclosed in a sheath, together with one or more traction-resistant members. Said sheath, which can either be metallic or not, is, in its turn, surrounded by other mechanical 3. ~ ~
members such as armorings, coverings, etc.
Tests which have been carried out have demonstrated that a primary cause of attenuation in the optical fibers in-corporated in a cable is constituted by the hydrogen which, once it becomes diffused inside the fiber, is capable of absorbing energy in a spectrum comprising the wavelengths utilized for the optical signals.
Under particular conditions, this phenomenon is reversible, and the attenuation can even be considerably reduced if it is possible for the hydrogen to diffuse towards outside the fiber, for example, due to a lowering of the outside concentration of hydrogen which caused the phenomenon.
On the other hand, in other cases, it has been possible to establish that a second cause of attenuation must be attributed to chemical reactions taking place between the main constituents of the fiber, for example, Si02 and/or its dopants Ge02, P205, etc., and the hydrogen which are contained inside the fiber itself.
The result of these reactions is the formation of groups containing the hydroxyl radical ~OH) which are responsible for the absorption at the wavelengths which are also used for the transmission of signals. These latter reactions are irreversible, and hence, there is a ~orxesponding deterioration of the fiber properties which can be expected under all conditions of use.
The parameters which control these phenomena are, apart from the chemical composition of the fiber, the partial pressure of the hydrogen to which the fiber is exposed, the temperature and, of course, time.
The fiber can come into contact with the hydrogen generated inside the cable, either during the cable manufacturing process, or else during the operation of the cable itself. As a matter of fact, the hydrogen can be generated by metallic or ~ r-non-metallic members present in the cable which have absorbed said gas during the manufacturin~, treating or finishing processes for the materials forming the cable.
The hydrogen can also be generated because of the eventual chemical degradation, through the oxidation, of the organic materials forming the cable, or else through the reaction of the water, ei-ther in a liquid state or as vapor and eventually present in the cable, with the metallic members of the cable in-cluded in the cable structure.
Certain organic materials used in the fiber cladding, are capable of producing hydrogen due to chemical reactions of various natures. It has been found that one hydrogen source is constituted by the protective coatings themselves, and in paxti-cular, when the protective coating is the silicone rubber. As a theory, it is assumed that when the cross-linking process is pro-longed in duration, there is a liberation of hydrogen at the fiber surface. The spreading of the hydrogen takes place towards the fiber, as well as towards outside of the protective coating but does not cause any appreciable phenomena on the outside of the coating because, in this case, the hydrogen becomes dispersed in the surrounding environment.
Nevertheless, when the fiber is situated within a closed cable and without there being sufficient free space around the fiber, the hydrogen concentration can achieve relatively high values which cause its appreciable diffusion, even towards the fiber itself, aided by the fact that the cladding, from which the hydrogen is developed, is very near to the fiber.
The diffusion of the hydrogen through the varlous materials varies with the material and is the lowest with metals but increases, successively with polymers, liquids and gases.
Hence, depending upon the type of cable and upon the environment ~ ~3 wherein it is utilized, there may be several rates for the emission of the hydrogen produced by the cable members. There-fore, there also are diverse rates of absorption, on the part of the cable, of the hydrogen eventually produced outside it and which permeates the operating ambient. The value of the partial pressure of the hydrogen inside the cable depends on these various rates and is a function of the time, because the greater the pressure and the duration are, the greater the level of risk for the fibers will be.
Given the service lifetime of an optical fibers cable, under foreseeable temperature conditions, the diffusion rate of the hydrogen through the metals is so low -that metallic sheaths of a normal thickness can be considered as being prac-tically impermeable to the hydrogen. In particular, the cables having metallic sheaths, especially if they have a small space inside them, are cables which have, in a short time and at high levels, increases in attenuation due to the hydrogen which is liberated from the elements inside of the sheath.
The object of the present invention is to provide an optical fiber which is protected against the absorption of gas-eous hydrogen which may be present in the cable containing the fiber. Such protectiqn is obtained, according to the invention, by providing around the outermost layer of the fiber itself, one or more coatings containing metals which are capable of combining with the hydrogen and which form a barrier in corres-pondence to said coating.
According to the invention, an optical fiber, having at least one protective coating, is characteri~ed by the fact of including, in at least one of said protective coatings, at least one powder of a metal selected ~rom the ~roups III, IV, V, VIII of the periodic system as a protection against the ab-sorption of gaseous hydrogen on the ~lq~ 5 part of the fiber.
The metals which have proved to be particularly suitable are lanthanides for Group III; titanium, zirconium and hanium for Group IV; vanadium, niobium and tantalum for Group V; and palladium for Group VIII, in the form of pure metals, their alloys or intermetallic compounds.
In the presence of hydrogen, the identified elements tend to form solid interstitial solutions which are similar to hydrides having a good stability, and this allows Eor a reduction in the partial hydrogen pressure in the cables to values which counterbalance the solubility of the hydrogen in the members themselves.
Preferably, the identified elements are suhjected to ~
thermal treatment, under vacuum, at temperatures of some hundreds of degrees centigrade, prior to being utili~ed in cable pro-duction, for the purpose of eliminating any hydrogen which may have been absorbed, and/or the combined oxygen.
Other objects and advantages of the present invention will be apparent from the following detailed description of the presently preferred embodiments thereof, which description should be considered in conjunction with the accompanying drawings in which:
Fig. 1 is a schematic cross-section of an optical fiber provided with a primary metallic coating of the invention;
Fig. la is a schematic cross-section of an optical fiber provided with a metallic coating of the invention around a primary coating on the fiber;
Fig. 2 is a schematic cross-section of an optical fiber provided with a primary insulation-metal powder coating of the invention;
Fig. 3 is a schematic cross-section of an optical fiber provided with a primary coating and a secondary coating of the invention;
Fig. 4 is a schematic cross-section of an optical fiber provided with a primary coating and a secondary coating of the invention, between which there is inter-posed a cushioning layer; and Fig. 5 is a schemat:ic cross-section of a coated optical fiber loosely enc:Losed by a small tube, the space between the tube and the fiber being filled with a gel containing metal powder according to the invention.
With reference to Fig. 1, an elementary optical fiber comprises a glass portion 1 of any type whatsoever, i.e. 'tstep index", "graded index" or other types, and a primary coating 2 adjacent and contacting the portion 1, the coating 2 having the function of protecting the fiber from the outer environment.
According to a first embodiment of the invention, the glass portion 1 is protected by a metallizing layer formed by one or more of the materials described. Said layer can constitute the primary coating 2 shown in Fig. 1 in close contact with the glass structure of the optical fiber. Thus, there is obtained a fiber where the primary coating is of the metallic type and which, at the same time, performs the mechanical function as well as the function of safeguarding against the absorption of hydrogen by the environment surrounding the fiber, during operation.
According to a variation shown in Fig la, th~ metal-lizing layer 2 is applied immediately over the usual primary coating la made oE cross-linked resin. This construction is utilizable whenever it is not possible or convenient to modify the plant ~or producing the fiber so that the protective coating is applied immediately after drawing the optical fiber to the ~l2~ 75 desired dimensions.
As a further variation, the coating la may be one or more coatings described hereinafter.
In accordance with a further embodiment, illustrated in Fig. 2, the primary coating 2a, made of acrylic resin or of some other suitable material, contains a dispersion of the powders of one or more of the cited metals, or their alloys or inter-metallic compounds. I'his permits the incorporation of the pro--tective coating in a conventional manufacturing process.
A further embodiment (Fig. 3) adds the metallic powders to the resin coating 3 immediately surrounding the primary covering la. This coating 3 is typically made of silicone rubber and, as explained previously, silicone rubber can become a parti-cularly dangerous source of hydrogen. The presence of the metals in this coating 3 effectively neutralizes the hydrogen which is generated, even before it can diffuse towards the fiber.
The optical fiber illustrated schematically in Fig. 4, is a further embodiment of the invention which has a dispersion of metallic powders in the secondary coating 4 which is con-stituted, for example, out of nylon or some other thermoplastic polymer.
In the embodiments described, the particles of the powders have dimensions which are, preferably, less than 10 microns, and the quantity of the powders per length unit of the optical fiber is selected to achieve a concentration within the range of from 0.1 to 10 phr (parts per hundred of resin) in the resin. The range of 0.1-10 phr is preferred, but can vary de-pending on the thickness of the coating. The metal content of the coating should be at least 0~01 g./m.
It must be kept in mind that the protective function, according to the invention, is accomplished in various ways, 3l7 depending upon the coating in which the metals are incorporated~
More precisely, the presence of a protective layer very close to the optical fiber, protects the la-tter mainly against the hydrogen generated in the innermost protective coatings, while an outer protective coating, for example, around the silicone rubber, provides mainly a protection from the hydrogen derived from the cable elements.
In view of what has been stated, as other factors depending upon the structure and the foreseeable conditions of operation of the cable, it will be apparent that the several pre-viously described different embodiments can be combined in a same optical fiber.
A further embodiment of the invention, which is il-lustrated in Fig. 5 r comprises an optical fiber 1 having a primary coating la enclosed by a small tube 9 of plastic material, the inner diameter of which is greater than the outer diameter of the fiber 1. The fiber 1 may be provided with the usual coatings for constituting an optical fiber of the loose type. For this type of fiber, which may have non-adherent coverings, the protection can be realized by having coatings such as those de-scribed previously and/or by providing inside the small tube 9 a gel 8, such as petroleum jelly or a silicone grease, containing a dispersion of powders of the described metals or their alloys or intermetallic compounds.
As an alternative, combined or not with the immediately preceding embodiment, the material that constitutes the small tube 9 may contain a dispersion of powders of the described metals or of their alloys or intermetallic compounds.
In the various embodiments, the content of the metal selected from one of -the Groups III, IV, V and VIII depends upon the amount of hydrogen which it is expected will be released or generated during the life of a cable containing the fiber. There-fore, the metal content depends on such things as cable size, materials, treatments, environment, etc. It is desirable to keep the hydrogen partial pressure content within the cable below 1-2 mm. Hg. The metal content should be the minimum amount determined to be necessary plus a small additional amount for safety reasons. The upper limit of the metal content depends upon cost and the effect oE the metal content on the physical properties of a coating incorporating the metal in powder form.
Palladium is,a preferred metal because it can be used in smaller amounts. Although other metals are less expensive, the niobium content, for example, should be of the order of ten times, by weight, the palladium content and the zirconium content, for example, should be of the order of one hundred times, by weight, the palladium content.
The content of palladium should not be less than lOntg/m.
of cable. A preferred range is between from 15 to 150 mg./m. of cable. Preferably, the palladium particle size is not greater than 10 microns when the material in which it is admixed is nylon to avoid significant alteration of the physical properties of the coating. The latter considerations apply when other metals are used.
Although preferred embodiments of the present invention have been described and illustrated, it will be apparent to those skilled in the art that various modifications may be made without departing from the principles of the invention.
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An optical fiber structure comprising an optical signal transmitting core surrounded by at least one protective layer, wherein the improvement comprises including in at least one of the protective layers at least one gaseous hydrogen absorbing powder of a metal selected from Groups III, IV, V and VIII of the periodic system for protecting the core with respect to the absorption of gaseous hydrogen.
2. An optical fiber structure as set forth in claim 1 wherein said powder of said metal is present in said one of the layers in an amount at least equal to 0.01 g./m. of length of the fiber.
3. An optical fiber structure as set forth in claim 1 wherein said metal is selected from the group consisting of lanthanides, titanium, zirconium, hafnium, vanadium, niobium, tantalum, palladium and mixtures, alloys and intermetallic components thereof.
4. An optical fiber structure as set forth in claim 1 or 3 wherein said one of the layers is in contact with said core.
5. An optical fiber structure as set forth in claim 1 or 3 wherein there is a further protective layer intermediate said one of the layers and the core.
6. An optical fiber structure as set forth in claim 1 or 3 wherein said one of the layers comprises said powder of said metal admixed with a resin.
7. An optical fiber structure as set forth in claim 1 wherein said one of the layers comprises said powder of said metal admixed with a resin and the particle size of the particles of said powder is not greater than 10 microns and said powder is present in an amount which is in the range from 0.1 to 10 parts per hundred of said resin.
8. An optical fiber structure as set forth in claim 7 wherein said one of the layers is in contact with the core.
9. An optical fiber structure as set forth in claim 7 wherein there is a further layer intermediate said one of the layers and said core.
10. An optical fiber structure as set forth in claim 7 wherein said resin is silicone rubber.
11. An optical fiber structure as set forth in claim 7 wherein there are two further layers intermediate said one of the layers and said core.
12. An optical fiber structure as set forth in claim 1 wherein said powder of said metal is dispersed in a gel.
13. An optical fiber structure as set forth in claim 17 wherein said gel is surrounded by a tube.
14. An optical fiber structure as set forth in claim 1 or 3 further comprising a further protective layer around said core and wherein said powder of said metal is around said further protective layer.
15. An optical fiber structure as set forth in claim 1 or 3 wherein one of the protective layers is a sheath.
16. An optical fiber structure as set forth in claim 1 or 3 wherein one of the protective layers is a sheath spaced from the optical fiber and said powder is intermediate said sheath and said optical fiber.
17. An optical fiber structure as set forth in claim 1 or 3 wherein one of the protective layers is a sheath spaced from the optical fiber, wherein one of the protective layers is a filler intermediate said sheath and said optical fiber and wherein said metal powder is dispersed in said filler.
18. An optical fiber structure as set forth in claim 1 or 3 wherein said sheath is made of a plastic material and said metal powder is dispersed in said plastic material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT20700/84A IT1176135B (en) | 1984-04-27 | 1984-04-27 | OPTICAL FIBER PROTECTED AGAINST GAS HYDROGEN ABSORPTION |
| IT20700A/84 | 1984-04-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1251075A true CA1251075A (en) | 1989-03-14 |
Family
ID=11170753
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000480142A Expired CA1251075A (en) | 1984-04-27 | 1985-04-26 | Optical fiber and cable with hydrogen combining layer |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS60239703A (en) |
| AU (1) | AU577574B2 (en) |
| BR (1) | BR8501841A (en) |
| CA (1) | CA1251075A (en) |
| DE (1) | DE3515228A1 (en) |
| FR (1) | FR2563634B1 (en) |
| GB (1) | GB2158263B (en) |
| GR (1) | GR851015B (en) |
| IT (1) | IT1176135B (en) |
| NL (1) | NL8500892A (en) |
| NO (1) | NO168209C (en) |
| NZ (1) | NZ211369A (en) |
| SE (1) | SE462007B (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8506497D0 (en) * | 1985-03-13 | 1985-04-17 | Telephone Cables Ltd | Cables |
| IT1186003B (en) * | 1985-10-08 | 1987-11-18 | Pirelli Cavi Spa | ABSORBENT HYDROGEN MIXTURE AND HYDROGEN ABSORBENT MIXTURE FOR FIBER OPTIC CABLE |
| GB8528423D0 (en) * | 1985-11-19 | 1985-12-24 | Stc Plc | Hydrogen occlusion in optical cables |
| GB2240189A (en) * | 1990-01-17 | 1991-07-24 | Telephone Cables Ltd | Optical cables |
| DE4108032A1 (en) | 1991-03-13 | 1992-09-17 | Bayer Ag | PALLADIUM-CONTAINING POLYMER COMPOSITION AND METHOD FOR THE PRODUCTION THEREOF |
| GB2313330A (en) * | 1996-05-24 | 1997-11-26 | Perkin Elmer Ltd | Coating optical fibres |
| US6205276B1 (en) | 1997-02-10 | 2001-03-20 | Pirelli Cavi E Sistemi S.P.A. | Moisture-resistant cable including zeolite |
| IT1290287B1 (en) * | 1997-02-10 | 1998-10-22 | Pirelli Cavi Spa Ora Pirelli C | MOISTURE RESISTANT CABLE |
| US6404961B1 (en) | 1998-07-23 | 2002-06-11 | Weatherford/Lamb, Inc. | Optical fiber cable having fiber in metal tube core with outer protective layer |
| FR2803045B1 (en) * | 1999-12-22 | 2002-10-11 | Cit Alcatel | OPTICAL FIBER AND FIBER OPTIC CABLE COMPRISING AT LEAST ONE HYDROGEN-ABSORBING INTERMETALLIC ELEMENT |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1079512A (en) * | 1978-11-16 | 1980-06-17 | Basil V.E. Walton | Powdered telephone cable filling compound |
| ATE4046T1 (en) * | 1980-02-12 | 1983-07-15 | The Post Office | OPTICAL GLASS FIBER AND METHOD OF METAL COATING PLASTIC COATED GLASS FIBER. |
| US4407561A (en) * | 1980-10-14 | 1983-10-04 | Hughes Aircraft Company | Metallic clad fiber optical waveguide |
| US4418984A (en) * | 1980-11-03 | 1983-12-06 | Hughes Aircraft Company | Multiply coated metallic clad fiber optical waveguide |
| GB2125180A (en) * | 1982-08-10 | 1984-02-29 | Standard Telephones Cables Ltd | Optical fibre manufacture |
| GB8321229D0 (en) * | 1983-08-05 | 1983-09-07 | Bicc Plc | Optical cables |
| JPS6082156A (en) * | 1983-10-13 | 1985-05-10 | ドル−オリバ− インコ−ポレイテツド | Hydrocyclone |
-
1984
- 1984-04-27 IT IT20700/84A patent/IT1176135B/en active
-
1985
- 1985-03-05 AU AU39535/85A patent/AU577574B2/en not_active Ceased
- 1985-03-08 NZ NZ211369A patent/NZ211369A/en unknown
- 1985-03-27 NL NL8500892A patent/NL8500892A/en not_active Application Discontinuation
- 1985-04-18 FR FR858505855A patent/FR2563634B1/en not_active Expired - Lifetime
- 1985-04-18 BR BR8501841A patent/BR8501841A/en unknown
- 1985-04-26 SE SE8502047A patent/SE462007B/en not_active IP Right Cessation
- 1985-04-26 CA CA000480142A patent/CA1251075A/en not_active Expired
- 1985-04-26 GR GR851015A patent/GR851015B/el unknown
- 1985-04-26 NO NO851686A patent/NO168209C/en unknown
- 1985-04-26 JP JP60090760A patent/JPS60239703A/en active Pending
- 1985-04-26 GB GB08510656A patent/GB2158263B/en not_active Expired
- 1985-04-26 DE DE19853515228 patent/DE3515228A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| NO168209C (en) | 1992-01-22 |
| NL8500892A (en) | 1985-11-18 |
| BR8501841A (en) | 1985-12-17 |
| GB2158263B (en) | 1988-01-06 |
| IT8420700A0 (en) | 1984-04-27 |
| JPS60239703A (en) | 1985-11-28 |
| SE462007B (en) | 1990-04-23 |
| SE8502047L (en) | 1985-10-28 |
| GR851015B (en) | 1985-11-25 |
| FR2563634A1 (en) | 1985-10-31 |
| NO168209B (en) | 1991-10-14 |
| IT8420700A1 (en) | 1985-10-27 |
| NZ211369A (en) | 1988-03-30 |
| GB8510656D0 (en) | 1985-06-05 |
| AU3953585A (en) | 1985-10-31 |
| FR2563634B1 (en) | 1990-02-23 |
| GB2158263A (en) | 1985-11-06 |
| SE8502047D0 (en) | 1985-04-26 |
| AU577574B2 (en) | 1988-09-29 |
| DE3515228A1 (en) | 1985-10-31 |
| NO851686L (en) | 1985-10-28 |
| IT1176135B (en) | 1987-08-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4718747A (en) | Optical fiber and cable with hydrogen combining layer | |
| CA1251075A (en) | Optical fiber and cable with hydrogen combining layer | |
| CA1152022A (en) | Ultraviolet absorbers in optical fiber coatings | |
| EP2060941B1 (en) | Optical fiber core and optical fiber tape core | |
| JP2786387B2 (en) | Hermetically sealed optical fiber cable | |
| EP0432931B1 (en) | Optical fiber comprising a nonpigmented cured color coating | |
| US5509101A (en) | Radiation resistant optical waveguide fiber and method of making same | |
| CA1262715A (en) | Hydrogen absorbing composition for optical fiber cables and cables containing such composition | |
| CA1251076A (en) | Optical fiber cable with hydrogen combining material | |
| EP2230221A1 (en) | Method of treatment of optical fibers with deuterium | |
| US5901264A (en) | Solar resistant optical fiber and method | |
| CA2006847C (en) | Optical fiber | |
| KR900002538B1 (en) | Composite over head transmission cable | |
| US4839970A (en) | Filling compound for light waveguide leads and/or light waveguide cables | |
| EP1458910B1 (en) | Composite yarn, method for obtaining same and resulting textile structure | |
| AU706194B2 (en) | Optical cable protected against humidity | |
| EP0157488B1 (en) | Optical fiber | |
| JP3484698B2 (en) | Optical fiber | |
| CN1212989C (en) | Method of producing optical fiber | |
| EP0114092B1 (en) | Glass fiber for optical transmission | |
| JPS6273213A (en) | Fire retardant optical fiber core | |
| JPH01262509A (en) | Method of maintaining radiation resistance of optical fiber | |
| US6418259B2 (en) | Optical conductor and its method of manufacture | |
| JPS6061709A (en) | Covered optical fiber | |
| JPH05249354A (en) | Running water preventive type optical fiber cable |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |