Foam for optical fiber cable, composition, and method of manufacturing

Patent metadata

Field	Value
Publication number	US-12339506-B2
Application number	US-202318195013-A
Country	US
Kind code	B2
Filing date	May 9, 2023
Priority date	Jul 2, 2019
Publication date	Jun 24, 2025
Grant date	Jun 24, 2025

Abstract

Embodiments of the disclosure relate to an optical fiber cable having at least one optical fiber, a cable jacket and a foam layer. The cable jacket includes an inner surface and an outer surface in which the outer surface is an outermost surface of the optical fiber cable. The inner surface is disposed around the at least one optical fiber. The foam layer is disposed between the at least one optical fiber and the cable jacket. The foam layer is made of an extruded product of at least one thermoplastic elastomer (TPE), a chemical foaming agent, and a crosslinking agent. The foam layer has a closed-cell morphology having pores with an average effective circle diameter of less than 100 μm. Further, the foam layer has a compression modulus of less than 1 MPa when measured at 50% strain.

First claim

What is claimed is:

1. An optical fiber cable comprising:
a cable jacket having an inner surface and an outer surface, wherein the inner surface defines a central bore that extends along a longitudinal axis of the optical fiber cable and the outer surface is an outermost surface of the optical fiber cable;
at least one optical fiber; and
a foam layer extruded to extend through the central bore that is disposed between the at least one optical fiber and the inner surface of the cable jacket, wherein the foam layer comprises:
a thermoplastic elastomer (TPE) foam comprising both a polymer component having at least one TPE and a chemical foaming agent;
wherein the TPE foam has a compression set of no more than 5% as measured after compression to a strain of 60% for ten hours and after four hours of recovery time using a parallel plate compression fixture on a dynamic mechanical analyzer, wherein further the foam layer has a closed-cell morphology having pores with an average effective circle diameter of less than 100 μm, wherein the foam layer has a compression modulus of less than 1 MPa when measured 50% strain as measured according to ASTM 3574.

2. The optical fiber cable of claim 1 , wherein the chemical foaming agent comprises at least of one azodicarbonamide, azodiisobutyronitrile, benzenesulfohydrazide, 4,4-oxybenzenesulfonyl semicarbazide, para-toluene sulfonyl semicarbazide, barium azodicarboxylate, N,N′-dimethyl-N, N′-dinitrosoterephthalamide, trihydrazino triazine, or sodium bicarbonate.

3. The optical fiber cable of claim 1 , wherein the TPE comprises at least one of a polyolefin elastomer, a thermoplastic polyolefin, or a thermoplastic vulcanizate.

4. The optical fiber cable of claim 1 , wherein the TPE has an unfoamed tensile modulus of at most 10 MPa at 100% secant as measured according ASTM D638.

5. The optical fiber cable of claim 1 , wherein a two meter piece of the optical fiber cable is capable of being twisted 1080° clockwise or counterclockwise along the longitudinal axis without having attenuation of greater than 0.15 dB.

6. The optical fiber cable of claim 1 , wherein the TPE comprises at least one of a polyolefin elastomer (POE), a thermoplastic polyolefin (TPO), or a thermoplastic vulcanizate (TPV).

7. The optical fiber cable of claim 6 , comprising the POE, wherein the comprises POE a copolymer of ethylene and octene or butene.

8. The optical fiber cable of claim 1 , further comprising:
at least one buffer tube, wherein the TPE foam is extruded around the at least one buffer tube.

9. The optical fiber cable of claim 1 , wherein the at least one buffer tube includes multiple buffer tubes in a stranded configuration in the central bore and the TPE foam is extruded around the stranded buffer tubes.

10. The optical fiber cable of claim 1 , wherein the at least one optical fiber includes a plurality of optical fibers arranged in a substantially planar array to form an optical fiber ribbon.

11. The optical fiber cable of claim 10 , further comprising multiple optical fiber ribbons formed into a ribbon stack, and wherein the TPE foam is extruded around the ribbon stack.

12. The optical fiber cable of claim 1 , wherein the TPE foam has a brittleness temperature below −50° C.

13. The optical fiber cable of claim 1 , wherein the TPE foam is dimensionally stable over the temperature range of −40° C. to 85° C. and has a shrinkback of less than 5%.

14. The optical fiber cable of claim 1 , wherein the TPE foam further comprises a crosslinking agent.

15. The optical fiber cable of claim 1 , wherein the foam layer is a first foam layer, the optical fiber cable further comprising a second foam layer, wherein the first foam layer is disposed between the optical fiber and the second foam layer, and wherein the second foam layer is disposed between the first foam layer and the inner surface of the cable jacket, wherein the first foam layer has a lower compression modulus than the second foam layer.

16. The optical fiber cable of claim 1 , wherein the foam layer has a compression modulus of less than 0.25 MPa when measured at 50% strain as measured according to ASTM 3574.

17. A method of preparing an optical fiber cable, the method comprising:
extruding a thermoplastic elastomer (TPE) foam layer around an optical fiber cable core along a longitudinal axis of the optical fiber cable core, wherein the TPE foam layer has a compression set of no more than 5% as measured after compression to a strain of 60% for ten hours and after four hours of recovery time using a parallel plate compression fixture on a dynamic mechanical analyzer, wherein further the TPE foam layer has a closed-cell morphology having pores with an average effective circle diameter of less than 100 μm, wherein still further the foam layer has a compression modulus of less than 1 MPa when measured at 50% strain as measured according to ASTM 3574.

18. The method of claim 17 , further comprising:
extruding a polymeric cable jacket around the TPE foam layer such that the TPE foam layer is disposed in an interior cavity of the polymeric cable jacket.

Assignees

• Corning Res & Dev Corp

Inventors

• Bringuier Anne Germaine
• Cheng Xiaole

Classifications

• G02B6/443 Primary

  Protective covering · CPC title

• C08J9/405

  with polymerisable compounds · CPC title

• G02B6/3888

  Protection from over-extension or over-compression · CPC title

• G02B6/3889

  using encapsulation for protection, e.g. adhesive, molding or casting resin · CPC title

• G02B6/4486

  Protective covering · CPC title