WO2016075120A1

WO2016075120A1 - Optical cable with flame retardant tensile strength members

Info

Publication number: WO2016075120A1
Application number: PCT/EP2015/076165
Authority: WO
Inventors: Louise Sian TEESDALE; David J. Walker
Original assignee: Tyco Electronics Uk Infrastructure Limited
Priority date: 2014-11-10
Filing date: 2015-11-10
Publication date: 2016-05-19

Abstract

A fire retardant cable that maintains the desirable mechanical properties of non-fire retardant cables is provided. In one embodiment, strength members located within the cable are treated with a fire retardant additive. The fire retardant cable is as light, small, strong, and flexible as comparable non-fire retardant cables. Related methods of manufacturing such a cable are also provided.

Description

OPTICAL CABLE WITH FLAME RETARDANT TENSILE STRENGTH MEMBERS

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Patent Application Serial No.

62/077,827, filed on November 10, 2014, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to telecommunications cables and more particularly to optical telecommunication cables.

BACKGROUND

Applications for optical cables have been growing. Depending on the application, it can be desirable for the cables to be fire retardant yet still maintain the desirable mechanical properties of non-fire retardant cables including having comparable size, weight, strength, and flexibility.

SUMMARY

The present disclosure provides a fire retardant cable that maintains the desirable mechanical properties of non-fire retardant cables. In one embodiment, strength members located within the cable are treated with a fire retardant additive. The fire retardant cable is as light, small, strong, and flexible as comparable non-fire retardant cables. Related methods of manufacturing of such a cable are also provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an optical cable in accordance with the principles of the present disclosure; and

FIG. 2 is an enlarged view of a portion of FIG. 1. DETAILED DESCRIPTION

Various examples will be described in detail with reference to the figures, wherein like reference numerals represent like parts and assemblies throughout the several views. Any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible variations of the inventive aspects disclosed herein.

Referring to FIGS. 1 and 2, a fiber optic cable 10 according to principles of the present disclosure is described herein in further detail. In the depicted embodiment, the fiber optical cable 10 includes an optical fiber 22 located in the center of the cable 10, a protective assembly 36 positioned around the optical fiber 22, a strength layer 38 positioned around the protective assembly, and an outer jacket 12 positioned around the strength layer 38. In the depicted embodiment, the cable 10 includes a circular cross-section and each of the above identified layers are arranged coaxially relative to each other. It should, however, be appreciated that alternative configurations are also possible.

In the depicted embodiment, the optical fiber 22 includes a central glass core 28 that defines a central longitudinal axis of the cable 10, a glass cladding layer 26 positioned around the glass core 28, and a polymeric coating layer 24 positioned around the glass cladding layer 26. In one embodiment, the outer diameter of the polymeric coating layer 24 can be between 200 to 300 microns. It should be appreciated that a number of other configurations are also possible. For example, in an alternative configuration the cable may include a plurality of optical fibers.

In the depicted embodiment the protective assembly 36 includes an outer tube 18 and a gel filled interior 20. In the depicted embodiment the tube 18 is constructed of a polybutylene terephthalate (PBT) material and the gel 20 is a water blocking type gel. In the depicted embodiment, the tube 18 includes an outer diameter that is between 1000-3000 (e.g., 1500-2500) microns. In the depicted embodiment, the protective assembly 36 also includes a tight buffer 40 that is shown position around the optical fiber 22 and the gel 20. In the depicted embodiment the tight buffer 40 includes an outer diameter that is between 500-1000 microns. It should be appreciated that many other alternative configurations are also possible. For example, in an alternative embodiment, the protective assembly 36 could instead not include a tight buffer, not include a tube and gel assembly, or not include either of the depicted structures. In the depicted embodiment the strength layer 38 comprises a plurality of tensile reinforcing rovings ("rovings") 14, 16 for providing tensile reinforcement to the fiber optic cable 10. The tensile reinforcing rovings are positioned between the optical fiber 22 and the jacket 12. More particularly, the tensile reinforcing rovings are positioned between the protective assembly 36 and the jacket 12. In the depicted embodiment, the rovings 14, 16 include eight fiberglass rovings 16 and four aramid rovings 14. In the depicted embodiment, the fiberglass reinforced rovings 16 and aramid roving 14 cooperate to have a combined tensile strength of at least 500 Newtons. It should be appreciated, that in alternative embodiment number, arrangement and composition of the roving may be different.

It should be appreciated that the term roving is used herein to refer to one or more strands that each including a plurality of continuous filaments. The rovings 14, 16 serve to provide the cable tensile strength. As discussed above, the material that comprises the roving is commonly fiberglass and/ or aramid yarn. The breaking tenacity of these material is relatively high (e.g., greater than 50 cN/tex for E-glass, greater than 70 cN/tex for S-glass, and greater than 175 cN/tex for aramid). In the depicted embodiment, the glass fiber roving 16 can for example be constructed of E-glass, S-glass, A-glass, C-glass, D-glass, or R-glass. It should be appreciated that other types of rovings are also possible.

In the depicted embodiment, the strength layer 38 comprises both a fire retardant/ flame retardant material 32 and a super-absorbent material 30. In the depicted embodiment the fire retardant material is a material that enables the cable to satisfy IEC standard 60332-1-2 vertical flame test criteria or any other industry test for fire resistance. This fire retardant construction is advantageous in application wherein the fiber cable may be located in area that could encounter fire or significant heat.

Super-absorbent material is used herein to refer to materials having hydrophiiic properties, which is capable of absorbing and retaining a comparatively large quantity of water. Super-absorbent materials are incorporated into optical cables to protect the optical fiber within the cable from water damage and/or to prevent water from migrating along the length of the cable. Examples of superabsorbents that can be used in the manufacture of the yarns include: cross-linked polyacrylic acid partially neutralized into its sodium salt, polypotassium. acrylate, copolymers of sodium aery I ate and acryiamide, terpoiymers of acrylamidc and carboxyl group- and suipho group-containing monomers (sodium salt), and polyacrylamide copolymers. It should be appreciated that many other alternative materials can also be super-absorbent materials. More information regarding super-absorbent materials as well as how to impregnate the materials into yarns can be found in, for example, US 6,319,558 and US 5,264,251. Both of these patents also refer to and describes procedures for determine the swelling value of such materials. In the depicted embodiment, the

superabsorbent materials have a swelling value of greater than 60.

In the depicted embodiment, the flame retardant material 32 and the super- absorbent material 30 are two different types of materials and they are both different than the material of the rovings 14, 16. In the depicted embodiment, the strength member layer 38 is constructed by impregnating a reinforcing roving with a superabsorbent component 30 and a fire retardant component 32 by exposing the reinforcing rovings 14, 16 to a solution that includes the superabsorbent component 30 mixed with the fire retardant component 32. In the depicted embodiment the spaces between the strands 34 of the rovings are impregnated with the mixture that comprises superabsorbent 30 and a fire retardant 32 compound. It should be appreciated that there are a number alternative ways to integrate the flame retardant material 32 and a super-absorbent material 30 with the roving 14, 16 to create a strength layer that incorporates a flame retardant material 32 and a super-absorbent material 30. It should be appreciated that the fire retardant compound 32 could be, for example, mica or any other fire retardant material that can be integrated into the rovings. In some example embodiments, chemical additives that have fire resistant properties are impregnated into rovings in a manner such that they cannot be removed from the rovings once applied.

In the depicted embodiment, the jacket 12 has a low smoke zero halogen construction. It should be appreciated that many other alternative jacket constructions are also possible.

Parts List:

10 Fiber optic cable

12 jacket

14 aramid roving

16 glass roving

18 tube (PBT)

20 gel

22 optical fiber

24 polymeric coating

26 glass cladding

28 glass core

30 super-absorbent material

32 flame retardant material

34 strands

36 protective assembly

38 strength layer

Various modifications and alterations of this disclosure will become apparent to those skilled in the art without departing from the scope and spirit of this disclosure, and it should be understood that the scope of this disclosure is not to be unduly limited to the illustrative examples set forth herein.

Claims

WHAT IS CLAIMED IS:

1. A fiber optic cable comprising:

an optical fiber;

a jacket surrounding the optical fiber;

a plurality of tensile reinforcing rovings for providing tensile reinforcement to the fiber optic cable, the tensile reinforcing rovings being positioned between the optical fiber and the jacket;

a super-absorbent material integrated into the tensile reinforcing rovings; and a fire retardant material integrated into the tensile reinforcing rovings.

2. The fiber optic cable of claim 1 , further comprising a buffer tube positioned between the optical fiber and the tensile reinforcing rovings.

3. The fiber optic cable of claim 2, further comprising a water blocking gel located within the buffer tube.

4. The fiber optic cable of claim 2, wherein the buffer tube includes a composition including polybutylene terephthalate (PBT).

5. The fiber optic cable of claim 1 , wherein the tensile reinforcing rovings include aramid yarn.

6. The fiber optic cable of claim 1 , wherein the tensile reinforcing rovings include e- glass.

7. The fiber optic cable of claim 1 , wherein the superabsorbent material includes materials that have a swelling value of greater than 60.

8. The fiber optic cable of claim 1 , wherein the fire retardant material includes mica.

9. The fiber optic cable of claim 1 , wherein the jacket has a low smoke zero halogen construction.

10. A fiber optic cable comprising:

an optical fiber;

a tube surrounding the optical fiber, the tube including a composition that includes polybutylene terephthalate (PBT);

a water blocking gel positioned within the tube;

a jacket surrounding the optical fiber;

a plurality of fiberglass reinforcing rovings for providing tensile reinforcement to the fiber optic cable, the fiberglass reinforcing rovings being positioned between the tube and the jacket;

a super-absorbent material integrated into the fiberglass reinforcing rovings;

a fire retardant material integrated into the fiberglass reinforcing rovings; and aramid yarn strands for providing tensile reinforcement to the fiber optic cable, the aramid yarn strands being positioned between the tube and the jacket.

1 1. The fiber optic cable of claim 10, wherein the fiberglass reinforced rovings and aramid cooperate to have a combined tensile strength of at least 500 Newtons.

12. The fiber optic cable of claim 10, wherein the fire retardant material is a material that enables the cable to satisfy IEC standard 60332-1-2 vertical flame test criteria.

13. The fiber optic cable of claim 10, wherein the fire retardant material is material other than the glass fiber that is impregnated into the glass fiber.

14. The fiber optic cable of claim 10, wherein the super-absorbent material is material other than the glass fiber and that is impregnated into the glass fiber.

15. The fiber optic cable of claim 10, wherein the super-absorbent material is material other than the fire retardant material and other than the glass fiber.

16. The fiber optic cable of claim 10, wherein the glass fiber substrate is selected from a group consisting of E-glass, S-glass, A-glass, C-glass, D-glass, and R-glass.

17. The fiber optic cable of claim 10, wherein the tube includes an outer diameter that is between 1500-2500 microns.

18. The fiber optic cable of claim 10, wherein the optical fiber includes a glass core, a glass cladding around the core, and a polymeric coating layer around the glass cladding, and wherein the outer diameter of the polymeric coating is between 200 to 300 microns.

19. The fiber optic cable of claim 10, further comprising a tight buffer located between the optical fiber and the water blocking gel.

20. Method for making a strength member for a cable comprising:

impregnating a reinforcing roving with a superabsorbent component and a fire retardant component by exposing the reinforcing roving to a solution including the superabsorbent component mixed with the fire retardant component.