1984-12-05
1987-11-17
LaRoche, Eugene R.
G02B 636
Patent
active
047070650
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to optical fibre feed through and finds particular application in optical fibre feed through at repeater housings, especially in submarine optical fibre cables.
BACKGROUND OF THE INVENTION
Water and gases (particularly hydrogen) can cause substantial damage if they penetrate into a repeater housing. For instance electronic components, particularly semi-conductors, metal oxide resistors, and surface acoustic wave filters could be damaged by water or gas ingress. If water or gases have penetrated into a submarine cable, which can occur as a result of permeation or cable damage for example, then it is clearly important to prvent them from entering a repeater housing.
Optical fibres contained in a submarine cable are often provided with a protective sheath which may comprise a primary layer, of silicone rubber for instance, and a secondary layer of, say, a polymeric material. A potential path for water and gases into a repeater housing is provided by any optical fibre feed through into the housing, the path being along the layers of the protective sheath of the optical fibre.
In the event of certain types of damage, perhaps affecting the cable to repeater housing joint, then water or gas at considerable pressure may be present at the optical fibre feed through to the repeater housing. It is desirable that the feed through should not allow water or gas ingress even under these conditions.
A second factor affecting the design of a feed through is that optical fibres are extremely fragile. The protection afforded by a protective sheath is therefore a very important factor and preferably should be preserved in some manner even at an optical fibre feed through.
SUMMARY OF THE INVENTION
It is an object of the present invention to reduce the possibility of water and gas ingress along sheathed optical fibres into submarine repeater housings while maintaining satisfactory mechanical protection of the fibres.
According to this invention there is provided a sealing assembly comprising a component having a bore, an optical fibre having a protective sheath and a stripped portion from which said sheath has been removed, the optical fibre being disposed in the bore so that the stripped portion and an adjacent portion having said sheath are within the bore and with a first sealant sealing said stripped portion to the bore and a second sealant sealing said adjacent portion to the bore.
BRIEF DESCRIPTION OF THE DRAWINGS
By way of example only, illustrative embodiments of the invention will now be described with reference to the accompanying drawings, in which
FIG. 1 is a sectional view of a sealing assembly
according to a first embodiment of the invention.
FIG. 2a is a sectional view of a sealing assembly according to a second embodiment of the invention. Elements of the sealing assembly which also appear in FIG. 1 are allotted the same reference numerals.
FIG. 2b is a sectional view of part of the assembly shown in FIG. 2a, including an end member, shown in greater detail.
FIG. 3 is a sectional view of the assembly of FIG. 2a mounted within a bulkhead.
Please note that some cross-hatching is omitted from the Figures for the sake of clarity.
DETAILED DESCRIPTION
Referring now to FIG. 1, an elongate, generally tubular member or ferrule 1 has a bore 2 throughout its length, and an external peripheral shoulder 3. An optical fibre 4 extends through the bore. The fibre is provided with a protective sheath 5. A portion A--A' of the fibre within the bore has been exposed by the removal of the corresponding sheath portion, producing sheath ends 6, 6'. The fibre portion A--A', the sheath ends 6, 6' and the sheath adjacent the sheath ends, are all sealed within the bore 2 by an encapsulant 7. An epoxy resin may be a suitable encapsulant.
FIG. 2a shows a more complex assembly in which the portion A--A' of the fibre 4 is provided with a metallization layer 8. The fibre 4, in the region of the metallization layer 8, is sealed to the wall of the bore by solder (20). The solder (20) is
REFERENCES:
patent: 4295707 (1981-10-01), Nakai et al.
patent: 4389086 (1983-01-01), Furusawa et al.
patent: 4606603 (1986-08-01), Cairns
British Telecommunications
LaRoche Eugene R.
Lee James C.
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