GB2192073A

GB2192073A - Cable gland

Info

Publication number: GB2192073A
Application number: GB08715547A
Authority: GB
Inventors: Duncan Alexander Gunn; John Charles Crownshaw; Arthur Alfred Davis; Gilbert Wilfred Peter Colgate
Original assignee: STC PLC
Current assignee: STC PLC
Priority date: 1984-01-19
Filing date: 1987-07-02
Publication date: 1987-12-31
Also published as: GB8715547D0; GB2192073B

Abstract

An optical fibre gland for a submerged repeater has separate guide parts (54a,54b) which fits around the fibre (53) and inside a guide body (50), and epoxy (57) and solder (55) seal and secure the fibre to the gland. <IMAGE>

Description

SPECIFICATION Optical fibre glands This invention relates to optical fibre glanding, arrangements for submerged repeaters and is divided out of application 8401447 (serial number 2153159).

In an optical undersea telecommunications system the major problems are the maintenance of a vapour and water free environment and an assembly of the electrical and optical components which ficilitates manufacture and testing prior to installation.

UK Patent application 2091901A provides a sealed chamber on the front of the bulkhead and two cable glands, one through the chamber wall and one through the bulkhead, to provide a sealed environment within the repeaters and enable fibre splicing in the chamber. However this arrangement is not ideal; in particular it is difficult to see how either gland can be factory tested, other than with gas under pressure, without damaging the cable or the gland.

According to the present invention this is provided a gland for a coated optical fibre comprising a hollow gland body an optical fibre guide having an inner bore which fits over the fibre and an outer wall which fits in the inner bore of the gland body, wherein the guide is secured and sealed both to the fibre and to the gland body, the body having means to secure it to and through a bulkhead or like, said guide comprising separate parts which fit together over the fibre.

In order that the invention can be clearly understood references will now be made to the accompanying drawings wherein: Figure 1 shows an optical fibre gland according to an embodiment of the invention and Figure 1A shows the two part fibre guide of Fig. 1 on different and larger scales.

Referring to Fig. 1, here the soldered assembly of a mid-fibre gland is shown.

Gland body 50 has an annular flange 51 and an internal bore step 52a 52b with a step 52c. A secondary coated fibre 53 is stripped of its secondary coating over a length 53a and its primary coating is removed over length 53b which is metallised. A split fibre guide 54 is fitted over the primary coated fibre, the two-part guide being shown in cross section in Fig. 1A, and the gland body 50 is slid over the fibre guide until the tapered end 54d abuts the tapered step 52c.

A fillet of solder 55 is applied to the metallised surface of the fibre to seal the fibre to the split guide 54 and the internal bore 52a. A gland end 56 is screwed into the soldered end of the gland body 50 and both ends 56 and 58 are flooded, where there is a small annular gap between the secondary coatings 53 and the gland body, with epoxy resin 57 to seal and secure the secondary coating at both ends into the gland. The term "bore" is herein used to include the rectangular cross section hole as well as the circular hole.

Fig. 1A shows the two-part fibre guide 54.

It comprises two similar parts 54a, 54b with a square-section bore 54c and a tapered end 54d which abuts the tapered section 52c in the gland body 50. The bore 54c just fits i.e.

is a sliding fit over the primary coating portion 53a, and the outer cylindrical wall of the guide is a sliding fit inside the larger bore 52a of the body 50. The gland end 56 and the opposite end 58 have a small annular gap between the internal bore and the secondary coating 53, to enable the resin 57 to penetrate and flood.

This design has the advantage that the majority of the thrust generated by sea pressure (should this occur under e.g. fault condition) is transmitted through the guide 54 to the gland body at the step 52c. The solder 55 is only required to support the small proportion of thrust generated over the guide bore (or groove) cross sectional area, and hence only a short length of fibre soldering is required. The second action of the solder is to provide a seal between guide and gland body as mentioned earlier.

A further advantage is that the length of fibre metallisation required is relatively short.

The gland body 50 is then pressure tested, prior to installation in a housing wall aperture using metal and elastometic 'O'-ring seals.

Both the gland body and the fibre guide are made of steel.

The end of the fibre is cleaned and spliced to another fibre for splicing onto a tail cable fibre3 Thus in all there are two fibre splices between an opto-electric device and the sea cable in a submerged repeater.

It is an important feature that the gland is individually testable for pressure before assembly as well as after assembiy as any faulty gland can individually be replaced and the fibre re-spliced without the need to disturb other fibres and glands of the repeater.

1. A gland for a coated optical fibre comprising a hollow gland body, an optical fibre guide having an inner bore which fits over the fibre and an outer wall which fits in the inner bore of the gland body, wherein the guide is secured and sealed both to the fibre and to the gland body, the body having means to secure it to and through a bulkhead or like, said guide comprising seperate parts which fit together over the fibre.

2. An optical fibre gland as claimed in claim 1 wherein the gland body has a stepped bore, the smailer bore fitting a larger diameter coating on the fibre, and the fibre guide parts

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Optical fibre glands This invention relates to optical fibre glanding, arrangements for submerged repeaters and is divided out of application 8401447 (serial number 2153159). In an optical undersea telecommunications system the major problems are the maintenance of a vapour and water free environment and an assembly of the electrical and optical components which ficilitates manufacture and testing prior to installation. UK Patent application 2091901A provides a sealed chamber on the front of the bulkhead and two cable glands, one through the chamber wall and one through the bulkhead, to provide a sealed environment within the repeaters and enable fibre splicing in the chamber. However this arrangement is not ideal; in particular it is difficult to see how either gland can be factory tested, other than with gas under pressure, without damaging the cable or the gland. According to the present invention this is provided a gland for a coated optical fibre comprising a hollow gland body an optical fibre guide having an inner bore which fits over the fibre and an outer wall which fits in the inner bore of the gland body, wherein the guide is secured and sealed both to the fibre and to the gland body, the body having means to secure it to and through a bulkhead or like, said guide comprising separate parts which fit together over the fibre. In order that the invention can be clearly understood references will now be made to the accompanying drawings wherein: Figure 1 shows an optical fibre gland according to an embodiment of the invention and Figure 1A shows the two part fibre guide of Fig. 1 on different and larger scales. Referring to Fig. 1, here the soldered assembly of a mid-fibre gland is shown. Gland body 50 has an annular flange 51 and an internal bore step 52a 52b with a step 52c. A secondary coated fibre 53 is stripped of its secondary coating over a length 53a and its primary coating is removed over length 53b which is metallised. A split fibre guide 54 is fitted over the primary coated fibre, the two-part guide being shown in cross section in Fig. 1A, and the gland body 50 is slid over the fibre guide until the tapered end 54d abuts the tapered step 52c. A fillet of solder 55 is applied to the metallised surface of the fibre to seal the fibre to the split guide 54 and the internal bore 52a. A gland end 56 is screwed into the soldered end of the gland body 50 and both ends 56 and 58 are flooded, where there is a small annular gap between the secondary coatings 53 and the gland body, with epoxy resin 57 to seal and secure the secondary coating at both ends into the gland. The term "bore" is herein used to include the rectangular cross section hole as well as the circular hole. Fig. 1A shows the two-part fibre guide 54. It comprises two similar parts 54a, 54b with a square-section bore 54c and a tapered end 54d which abuts the tapered section 52c in the gland body 50. The bore 54c just fits i.e. is a sliding fit over the primary coating portion 53a, and the outer cylindrical wall of the guide is a sliding fit inside the larger bore 52a of the body 50. The gland end 56 and the opposite end 58 have a small annular gap between the internal bore and the secondary coating 53, to enable the resin 57 to penetrate and flood. This design has the advantage that the majority of the thrust generated by sea pressure (should this occur under e.g. fault condition) is transmitted through the guide 54 to the gland body at the step 52c. The solder 55 is only required to support the small proportion of thrust generated over the guide bore (or groove) cross sectional area, and hence only a short length of fibre soldering is required. The second action of the solder is to provide a seal between guide and gland body as mentioned earlier. A further advantage is that the length of fibre metallisation required is relatively short. The gland body 50 is then pressure tested, prior to installation in a housing wall aperture using metal and elastometic 'O'-ring seals. Both the gland body and the fibre guide are made of steel. The end of the fibre is cleaned and spliced to another fibre for splicing onto a tail cable fibre3 Thus in all there are two fibre splices between an opto-electric device and the sea cable in a submerged repeater. It is an important feature that the gland is individually testable for pressure before assembly as well as after assembiy as any faulty gland can individually be replaced and the fibre re-spliced without the need to disturb other fibres and glands of the repeater. CLAIMS

2. An optical fibre gland as claimed in claim 1 wherein the gland body has a stepped bore, the smailer bore fitting a larger diameter coating on the fibre, and the fibre guide parts fitting in the larger bore and fitting over a smaller portion of the fibre, wherein an exposed length of the fibre is bonded both to the fibre guide and to the gland body at one end of the body and wherein axial hydrostatic pressure on the gland will be borne substantially by reaction between the guide parts and the step in the bore.

3. A gland as claimed in claim 1 or 2, wherein there are two similar fibre guide parts which fit together at longitudinal faces, each part defining an inner surface which embraces the fibre.

4. A gland substantially as hereinbefore described with reference to Figs. 1 and 1A of the accompanying drawings.

5. A method of glanding an optical fibre comprising providing a coated fibre, providing a tubular gland body over the fibre providing optical fibre guide parts, fitting over the fibre, the optical fibre guide parts, assembling the guide inside the gland body and sealing the securing guide to the optical fibre and to the gland body so that in use pressure across the gland will be borne substantially by reaction between the guide and the gland body.

6. A method as claimed in claim 5, wherein an exposed portion of fibre is metalically bonded to one end of the guide and to the gland body.

7. A method as claimed in claim 5 or 6, wherein at least one of the gland body is flooded with epoxy to secure a secondary coating of the fibre to the gland body.

8. A method of glanding an optical fibre substantially as hereinbefore described with reference to Figs. 1 and 1A of the accompanying drawings.