GB2172410A

GB2172410A - Optical fibre cable containing hydrogen trapping powder

Info

Publication number: GB2172410A
Application number: GB08606149A
Authority: GB
Inventors: Raymond Sydney Ashpole; Norman Charles Fielder
Original assignee: Telephone Cables Ltd
Current assignee: Telephone Cables Ltd
Priority date: 1985-03-13
Filing date: 1986-03-12
Publication date: 1986-09-17
Also published as: GB2172410B; GB8606149D0; GB8506497D0

Abstract

Optical cables are provided with hydrogen trapping, and optionally water-blocking, powder (11) coated on a substrate tape (1) so as to avoid having loose powder within the cable which can compact and cause loss of freedom of movement of optical fibres (9). The substrate (1) extends longitudinally within a protective cover (10). Optical fibres (9) are shown. <IMAGE>

Description

SPECIFICATION Cables This invention relates to optical fibre cables, that is to say cables incorporating one or more filamentary elements of a light conducting nature within a protective cover and relates also to the manufacture of such cables.

It is known that hydrogen has a deleterious effect on the performance of optical fibres and thus it has been suggested in our co-pending PatentApplication No. 8428102 to use a hydrogen trapping material in such cables, that is to say a material capable of collecting free hydrogen, either by absorption or by chemical or other action, thereby reducing the amount of hydrogen available within the cable which could have a detrimental effect on the optical fibre or fibres.

Such a material may take the form of a powder and in the above-mentioned co-pending application it has been proposed to at least partially fill the interstices between the filamentary elements with such powder. However it has been found that the powder can settle and compact and thus cause a loss of freedom of movement of the elements which is particularly disadvantageous because optical fibres are very fragile.

Accordingly, the invention provides a cable incorporating one or more filamentary elements of a light conducting nature within a protective cover, the cable further including hydrogen trapping powder carried by a substrate extending longitudinally with- in the protective cover.

The hydrogen trapping powder may comprise a material, such as palladium-coated carbon particles, which catalyses the reaction of hydrogen with oxygen to form water. Accordingly the powder in such a case, is preferably mixed with a waterabsorbing or water-blocking substance as mentioned in said co-pending application.

The substrate is preferably a flexible tape made of either paper or plastic such as Mylar or Melinex polyester.

The powder is preferably bonded to the substrate by means of a suitable adhesive, which may be a resin such as acrylic emulsion or a U.V.-cured epoxyacrylate.

In accordance with a further aspect of the invention, there is provided a method of manufacturing a cable incorporating one or more filamentary elements of a light conducting nature the method including the steps of coating a substrate with hydrogen trapping powder, feeding the substrate and one or more said filamentary elements to an extruder head and extruding a protective cover of thermoplastic material around both the substrate and the element or elements.

At least one of the elements may first be enclosed in a separate protective tube before being fed to the extruder head if desired Preferably, the substrate is coated with the powder by first apprying adhesive to the substrate and then dusting the adhesive with the powder. Excess powder may then be scraped off if desired.

The invention will now be more fully described by way of example with reference to the drawing of which Figure 1 shows a diagrammatic form the steps according to the invention required for manufacturing a cable; and Figure 2 shows, in cross-section, one embodiment of a cable made in accordance with the invention.

Turning first to Figure 1, a paper tape 1 is fed from a roll 2 past an applicator 3 which applies acrylic emulsion to one surface of the tape. The tape is then led past a duster 4 which dusts the tape with a hydrogen trapping powder such as palladiumcoated carbon together with a quantity of a waterblocking substance, such as sodium carboxymethyl cellulose also in powder form, which powders stick to the emulsion. A scraper 5 is then used to scrape off excess powder and the tape is then heated by means of a heater 6 so as to cure the emulsion.

The tape is then formed into a tube with the coated side on the inside by passing it through a shaper 7 before it reaches an extruder head 8. As the tape is fed into the shaper 7, optical fibres 9 are also fed in so that they are enclosed within the tube, the fibres being slightly longer than the tube so that they are loose within it.

Finally a plastic protective cover 10 is extruded around the tube by the extruder head 8.

The construction of the cable can best be seen from Figure 2 where three optical fibres of paper tape 1 coated on the inside with hydrogen trapping and water-blocking powders 11 and having an extruded protective cover 10 around it.

The paper tape is conveniently 50ijm thick and has a coating which is typically 1 50-2001lm but could be thicker depending on the dimensions of the tube to be formed. Generally the volume of powder should be between 10-15% of the tube volume.

If a U.V.-cured expoxyacrylate resin is used, there is typically a 50/50 mix of powder/resin by volume.

This type of resin has the advantage of rapid curing and consequently fast production speeds.

It will be appreciated that tapes of other materials can be used providing they are compatible with the adhesive used.

It will further be appreciated that the tapes can easily be introduced into any cable construction whether of the type described above or when the fibres are enclosed within channels in an extrudate, the substrate then being within the channels also, or when the fibres are enclosed within separate tubes stranded together, the substrate then being either within each tube with the fibres or surrounding the stranded tubes or both. Thus the invention is applicable to all types of cable construction and can be used to advantage with all of them.

1. An optical fibre cable as hereinbefore defined including hydrogen trapping powder carried by a substrate extending longitudinally within the protective cover.

2. An optical fibre cable according to Claim 1 wherein the hydrogen trapping powder comprises a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Cables This invention relates to optical fibre cables, that is to say cables incorporating one or more filamentary elements of a light conducting nature within a protective cover and relates also to the manufacture of such cables. It is known that hydrogen has a deleterious effect on the performance of optical fibres and thus it has been suggested in our co-pending PatentApplication No. 8428102 to use a hydrogen trapping material in such cables, that is to say a material capable of collecting free hydrogen, either by absorption or by chemical or other action, thereby reducing the amount of hydrogen available within the cable which could have a detrimental effect on the optical fibre or fibres. Such a material may take the form of a powder and in the above-mentioned co-pending application it has been proposed to at least partially fill the interstices between the filamentary elements with such powder. However it has been found that the powder can settle and compact and thus cause a loss of freedom of movement of the elements which is particularly disadvantageous because optical fibres are very fragile. Accordingly, the invention provides a cable incorporating one or more filamentary elements of a light conducting nature within a protective cover, the cable further including hydrogen trapping powder carried by a substrate extending longitudinally with- in the protective cover. The hydrogen trapping powder may comprise a material, such as palladium-coated carbon particles, which catalyses the reaction of hydrogen with oxygen to form water. Accordingly the powder in such a case, is preferably mixed with a waterabsorbing or water-blocking substance as mentioned in said co-pending application. The substrate is preferably a flexible tape made of either paper or plastic such as Mylar or Melinex polyester. The powder is preferably bonded to the substrate by means of a suitable adhesive, which may be a resin such as acrylic emulsion or a U.V.-cured epoxyacrylate. In accordance with a further aspect of the invention, there is provided a method of manufacturing a cable incorporating one or more filamentary elements of a light conducting nature the method including the steps of coating a substrate with hydrogen trapping powder, feeding the substrate and one or more said filamentary elements to an extruder head and extruding a protective cover of thermoplastic material around both the substrate and the element or elements. At least one of the elements may first be enclosed in a separate protective tube before being fed to the extruder head if desired Preferably, the substrate is coated with the powder by first apprying adhesive to the substrate and then dusting the adhesive with the powder. Excess powder may then be scraped off if desired. The invention will now be more fully described by way of example with reference to the drawing of which Figure 1 shows a diagrammatic form the steps according to the invention required for manufacturing a cable; and Figure 2 shows, in cross-section, one embodiment of a cable made in accordance with the invention. Turning first to Figure 1, a paper tape 1 is fed from a roll 2 past an applicator 3 which applies acrylic emulsion to one surface of the tape. The tape is then led past a duster 4 which dusts the tape with a hydrogen trapping powder such as palladiumcoated carbon together with a quantity of a waterblocking substance, such as sodium carboxymethyl cellulose also in powder form, which powders stick to the emulsion. A scraper 5 is then used to scrape off excess powder and the tape is then heated by means of a heater 6 so as to cure the emulsion. The tape is then formed into a tube with the coated side on the inside by passing it through a shaper 7 before it reaches an extruder head 8. As the tape is fed into the shaper 7, optical fibres 9 are also fed in so that they are enclosed within the tube, the fibres being slightly longer than the tube so that they are loose within it. Finally a plastic protective cover 10 is extruded around the tube by the extruder head 8. The construction of the cable can best be seen from Figure 2 where three optical fibres of paper tape 1 coated on the inside with hydrogen trapping and water-blocking powders 11 and having an extruded protective cover 10 around it. The paper tape is conveniently 50ijm thick and has a coating which is typically 1 50-2001lm but could be thicker depending on the dimensions of the tube to be formed. Generally the volume of powder should be between 10-15% of the tube volume. If a U.V.-cured expoxyacrylate resin is used, there is typically a 50/50 mix of powder/resin by volume. This type of resin has the advantage of rapid curing and consequently fast production speeds. It will be appreciated that tapes of other materials can be used providing they are compatible with the adhesive used. It will further be appreciated that the tapes can easily be introduced into any cable construction whether of the type described above or when the fibres are enclosed within channels in an extrudate, the substrate then being within the channels also, or when the fibres are enclosed within separate tubes stranded together, the substrate then being either within each tube with the fibres or surrounding the stranded tubes or both. Thus the invention is applicable to all types of cable construction and can be used to advantage with all of them. CLAIMS

2. An optical fibre cable according to Claim 1 wherein the hydrogen trapping powder comprises a material which catalyses the reaction of hydrogen with oxygen to form water, and is mixed with a water-absorbing or water-blocking substance.

3. An optical fibre cable according to Claim 1 or 2 wherein the substrate is a flexible tape.

4. An optical fibre cable according to Claim 3 wherein the tape is formed of paper or a plastics material.

5. An optical fibre cable according to any preceding Claim wherein the hydrogen trapping powder is bonded to the substrate by an adhesive.

6. An optical fibre cable according to Claim 5 wherein the adhesive is a synthetic resin.

7. A method of manufacturing an optical fibre cable in accordance with any preceding Claim including the steps of coating a substrate with hydrogen trapping powder, feeding the substrate and one or more said filamentary elements to an extruder head and extruding a protective cover of thermoplastic material around both the substrate and the element or elements.

8. A method according to Claim 7 wherein at least one of the filamentary elements is enclosed in a separate protective tube before being fed to the extruder head.

9. A method according to Claim 7 or 8 wherein the substrate is coated with the powder by first applying an adhesive to the substrate and then dusting the adhesive with the powder.

10. A method according to Claim 9 wherein the adhesive comprises an acrylic emulsion or a U.V.curable epoxyacrylate.

11. A method according to Claim 7, 8,9 or 10 wherein the substrate is in the form of a flexible tape.

12. A method according to Claim 11 wherein the tape is formed of paper or a plastics material.

13. A method of making an optical fibre cable substantially as shown in and as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawing.

14. An optical fibre cable made by a method according to any one of Claims 7 to 13.