Flame retardant optical cable

Patent metadata

Field	Value
Publication number	US-11016256-B2
Application number	US-201716758831-A
Country	US
Kind code	B2
Filing date	Oct 30, 2017
Priority date	Oct 30, 2017
Publication date	May 25, 2021
Grant date	May 25, 2021

Abstract

A flame-retardant optical cable is disclosed which includes a polymeric central loose tube housing optical fibres, a metallic armour surrounding the polymeric central loose tube, and a multi-layered sheath surrounding and in direct contact with the metallic armour. The multi-layered sheath includes an inner layer, an intermediate layer, and an outer layer, all made of a LSoH flame-retardant material. The LSoH flame-retardant material of the intermediate layer has a limiting oxygen index (LOI) higher than the LOI of the LSoH flame-retardant material of the inner layer and of the outer layer. Such cable has improved flame-retardant properties, particularly in terms of slowing flame propagation, heat release, droplets and emission of smokes, when it is exposed to flames during fire.

First claim

The invention claimed is:

1. A flame-retardant optical cable comprising:
a polymeric central loose tube housing optical fibres;
a metallic armour surrounding the polymeric central loose tube; and
a multi-layered sheath surrounding and in direct contact with the metallic armour, wherein the multi-layered sheath comprises an inner layer, an intermediate layer and an outer layer all made of a LSoH flame-retardant material, and wherein the LSoH flame-retardant material of the intermediate layer has a limiting oxygen index (LOI) higher than the LOI of the LSoH flame-retardant material of the inner layer and of the outer layer.

2. The optical cable according claim 1 , wherein the intermediate layer of the multi-layered sheath is made of a LSoH flame-retardant material having a LOI higher than 70% and wherein the inner layer and the outer layer of the sheath are both made of a LSoH flame-retardant material having a LOI from 25% to 70%.

3. The optical cable according claim 2 , wherein the intermediate layer is made of a LSoH flame-retardant material having a LOI from 75% to 90%.

4. The optical cable according claim 2 , wherein the inner layer and the outer layer of the sheath are both made of a LSoH flame-retardant material having a LOI from 30% to 50%.

5. The optical cable according claim 1 , wherein the inner layer and the outer layer are made of the same LSoH flame-retardant material.

6. The optical cable according claim 1 , wherein the inner layer is made of a LSoH flame-retardant material having a LOI lower than that of the outer layer.

7. The optical cable according claim 6 , wherein the inner layer is made of a LSoH flame-retardant material having a LOI from 25 to 35%, and wherein the outer layer is made of a LSoH flame-retardant material having a LOI from 35 to 50%.

8. The optical cable according to claim 1 , wherein the inner layer and the outer layer of the multi-layered sheath have a thickness greater than the thickness of the intermediate layer.

9. The optical cable according to claim 1 , wherein the polymeric central loose tube is at least partially filled with a water-blocking material.

10. The optical cable according to claim 1 , further comprising a reinforcing layer around and in direct contact with the polymeric central loose tube.

11. The optical cable according to claim 10 , wherein the reinforcing layer comprises aramid.

12. The optical cable according claim 10 , further comprising a water-swellable layer surrounding the reinforcing layer and the metallic armour.

13. The optical cable according to claim 10 , wherein the reinforcing layer comprises fiberglass yarns.

14. An optical cable comprising:
a polymeric central loose tube housing optical fibres;
a reinforcing layer around and in direct contact with the polymeric central loose tube;
a metallic armour surrounding the reinforcing layer; and
a multi-layered sheath surrounding and in direct contact with the metallic armour, wherein the multi-layered sheath comprises an inner layer, an intermediate layer and an outer layer, all made of a LSoH flame-retardant material, and wherein the LSoH flame-retardant material of the intermediate layer has a limiting oxygen index (LOI) higher than the LOI of the LSoH flame-retardant material of the inner layer and of the outer layer.

15. The optical cable according claim 14 , further comprising a water-swellable layer surrounding the reinforcing layer and the metallic armour.

16. The optical cable according to claim 14 , wherein the reinforcing layer comprises fiberglass yarns.

17. The optical cable according claim 14 , wherein the intermediate layer of the multi-layered sheath is made of a LSoH flame-retardant material having a LOI higher than 70% and wherein the inner layer and the outer layer of the sheath are both made of a LSoH flame-retardant material having a LOI from 25% to 70%.

18. The optical cable according claim 14 , wherein the intermediate layer is made of a LSoH flame-retardant material having a LOI from 75% to 90%, wherein the inner layer and the outer layer of the sheath are both made of a LSoH flame-retardant material having a LOI from 30% to 50%.

19. The optical cable according claim 14 , wherein the inner layer is made of a LSoH flame-retardant material having a LOI lower than that of the outer layer.

20. The optical cable according to claim 14 , wherein the polymeric central loose tube is at least partially filled with a water-blocking material.

Assignees

• Prysmian Spa

Inventors

• Sirin Zekeriya
• Soenmez Baris

Classifications

• G02B6/4488

  using metallic tubes · CPC title

• G02B6/4436 Primary

  Heat resistant · CPC title

• G02B6/4432

  with fibre reinforcements · CPC title