The present invention relates to an end seal assembly for sealing the end of a conduit or passageway carrying multiple conductors such as optical fibers or wires or a feedthrough for optical fibers or wires into an enclosure or through a bulkhead, for example. The end seal assembly is particularly designed for underwater or other high pressure applications.
Modern communications systems, particularly those employing optical fibers as conductors, often require means for passing said conductors sealably through high-pressure barriers such as instrumentation housings. One such means has been to provide rigid metal bores through which the conductors pass and into which they are sealably restrained by epoxy potting material. One drawback to using epoxy potted directly into metal bores is that the two materials have different bulk moduli and thermal expansion coefficients. As a result, cracking of the epoxy, or separation of the epoxy-metal interface often occurs with thermal and/or pressure cycling.
A particular subset of feed-through applications involves the common use of rigid tubes, or cables, to contain and protect fibers. These may be incorporated within more complex cables. Sometimes these tubes or cables contain multiple fibers. Some cables are simply empty except for the fibers. Others are filled with gel. Such cables or tubes are typically of small diameter (1/10 inch or so). In gel-filled cables, the gel will expand or contract from the ends of the tube under changing pressure and temperature if it is not sealed, which will strain the fibers and potentially cause them to bend or break.
The ends of conductor-bearing cables, in practice, are usually terminated to fiber management chambers associated with connectors or instrument/equipment canisters. It is generally desirable to physically isolate the inside of the cables from these enclosures, both to preclude the exchange of fluid/gel between them, and to prevent the migration of fiber from the tube to the enclosure or vice versa. However, this can be difficult to achieve in a small size cable carrying multiple, very fine fibers or wires.
In application Ser. No. 08/856,928 of Cairns et al., filed May 15, 1997, an underwater bulkhead feedthrough assembly is described in which optical fibers or electrical wires are fed from the end of an underwater cable through a bulkhead into an enclosure or equipment housing. The cable end is coupled to one end of a connector body, and the individual fibers or wires extend through a bore in the body and a seal assembly within the body. This assembly is suitable for many applications, but is difficult to assemble for small tubes with closely packed fibers or wires.
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