GB2210472A - Optical fibre package termination assembly - Google Patents

Abstract

An assembly for protecting and separating individual fibres (5) of an optical fibre package (1) at the point where the outer covering of the fibre package is removed. The individual fibres are threaded through a manifold (7) and into individual plastics tubes (8) attached to the output end of the manifold apertures. A clamp assembly (9, 10) holds the manifold in position, and may also act to protect the base portions of the fibres although provision of a separate break out tube (3) is preferred. <IMAGE>

Description

TERMINATION ASSEMBLY This invention relates to optical fibre installations.

Installation of optical fibre bundles along ducts utilising viscous drag of compressed air injected at one end of a duct to propel a lightweight fibre package along the duct is described in our European Patent 0108590. In this technique, known as fibre blowing, the individual fibres are packaged together in a bundle, typically of eight fibres, with a lightweight foam polyethylene covering. This covering provides protection for the fibres within the installation ducts, but at terminations the foam covering has to be removed so that the individual fibres can be separated and connected to other elements of the assembly. At present about one metre of fibre package is stripped of the foam covering and the individual exposed fibres are spliced to reinforced ('ruggedised') terminal connection leads.

The splices and the excess lengths of exposed fibres, which are required for ease of handling during the splicing operation and for future splicing, are wound into a storage container into which the installation duct enters at one side and from which the ruggedised connection leads extend at the opposite side. The storage container for the splices and exposed fibre is large (compared with the fibre package dimensions) and the splices to the ruggedised connector leads have the disadvantage of up to 0.5 dB loss and introduction of cladding modes in a region where there is exposed fibre and also relatively simple access since the splices are accessible for servicing.

The present invention is directed towards providing a compact assembly that is more easily installed at a fibre bundle termination, is more compact and avoids the necessity for splices to separate ruggedised leads.

Accordingly the invention provides a break out assembly for an optical fibre package that comprises a plurality of optical fibres and an outer covering, the assembly comprising a break out member having a bore with a first portion being adapted to receive the fibre package and a second portion adapted to receive a manifold, the manifold having a plurality of bores for the receipt of exposed fibres from which protective outer covering of the package has been removed and each of the bores communicating with a passageway for the fibres that are threaded through the manifold.

The invention also provides a break out assembly further comprising means for securing the fibre package within the break out member.

The invention is now described by way of example with reference to the accompanying drawings in which: Figure 1 is perspective view of an embodiment of the invention prior to assembly; Figure 2 is a perspective view of the embodiment of Figure 1 assembled and showing an outer clamp enclosure, and Figure 3 shows the embodiment of Figure 2 with the clamp fully assembled.

Referring to Figure 1, a fibre blowing fibre package 1 is inserted into a break out member 3 through an aperture 2 in the end of the member. The break out member 3 preferably comprises a tube, which may be flared, as shown, or have a cylindrical shape. The break out member 3 has an axial bore opening at aperture 2 at one end where the diameter is sufficient to slidingly accommodate the fibre package, the bore then widens to a conical bore region with the wider end of the bore defining an aperture 4 at the other end of the member 3 to the aperture 2. Once located on the fibre package 1 the break out member is slid along until about a metre of fibre package extends out of aperture 4, and the outer coating is removed from the fibre package to expose the individual fibres 5 of the package.The break out member 3 is then slid a short way back along the fibre package, towards the exposed fibres so that the complete packaged fibre enters aperture 2 and extends along the first cylindrical part of the bore and the exposed length of fibres where the cladding has been removed commences at the conical region of the bore and the fibres have space to be flared apart.

Each individual fibre 5 is threaded through a corresponding aperture or bore 6 in a manifold tube 7.

In general the fibres are threaded singly, but it is possible in some applications to conduct more than one fibre through a single aperture. The manifold tube. 7 has a protective tube 8 attached to the exit of each of the bores 6 so that the fibres 5 having passed along the manifold bore each enter an individual protective tube 8. The manifold tube 7 is shaped to engage with the break out member 3 so that once the exposed fibres have been threaded through the manifold and into the protective tubes 8 the manifold and break out member can be engaged together into a single unit as shown in Figure 2.A suitable engagement mechanism is a push fit of the manifold into the aperture 4 of the break out member and in the embodiment shown the bore of the break out tube has a large diameter cylindrical portion extending from the wider end of the conical portion in order to facilitate this push fit. In order to protect the fibres, relative rotation of the manifold and break out member should be prevented. This may be achieved by fixing the parts together with epoxy resin. The fibre package is also secured in position in the break out member by epoxy resin or other suitable means.

Preferably the free space within the bore is filled with a suitable resin: this may be achieved by injection via the aperture 2 (if a sufficiently loose fit around the fibre package) or via specifically provided injection holes.

Alternative structures of manifold are envisaged, for example the bores may have lateral slots communicating with the surface to aid threading. The protective tubes 8 may be demountable from the manifold to aid threading, with a suitable permanent fixing being provided after threading, again resin bonding interfitting parts being possible or alternatively a threaded coupling.

Preferably the protective tubes 8 comprise part of a ruggedised terminal assembly with end connectors. The tubes 8 may include a Kevlar coating for added strength.

A plurality of tubes, possibly co-extruded, may be held together so that their ends constitute the manifold. The manifold may have configurations other than circular. If the ducts are co-extruded a line or array manifold formation with the ducts forming an easily separable ribbon is particularly preferred.

The break out member and manifold assembly fit into a two part clamp 9, 10 shown in Figure 2 that has a shaped recess 14 in each part to accommodate the assembly. The clamp may conveniently comprise two identical halves which can be injection moulded. The clamp parts also each have a channel 11 for the fibre package with a series of ridges 12 in the channels for gripping the exterior of the fibre package so that any tension or disturbance is taken up by the clamp rather than transferred to the break out member and manifold assembly. Holes 13 are provided through the clamp for securing the clamp to a wall, fixing panel or other mounting. The compact assembly may be located within a housing for other apparatus, such as a computer housing, or when mounted externally the clamp assembly is not unduly large compared with the duct for the fibre package.The clamp may also be provided with means for sealing to the duct along which the fibre package is installed as well as for sealing to the fibre package itself.

A modification of the assembly is for the clamp and break out member to be made as a single unit, with the recess 14 for the break out member being replaced by a channel for direct receipt of the fibre package, for example a recess shaped similarly to the bore of the break out member 3. The manifold could also be made integrally with the clamp or remain separate, for example as a slot in disc. In this instance the manifold could be threaded before the clamp parts are mounted around the fibre package. In order to connect the clamp to the installation duct the end 15 of the clamp is conveniently made of the same diameter as the duct so that a standard duct connector may be used.

Break out assemblies and/or clamps may also be incorporated in the structure of equipment such as patch panels.

It will be realised that when the clamp and break out member are combined with the clamp, in general as shown in Figure 2, the break out member is separable along a longitudinal partition line. Alternatively the clamp parts may be made as integral outer extensions of the break out assembly shown in Figure 1, so that there is no longitudinal break. Another option is for the break out member and manifold to be longitudinally separable.

A particular advantage of the invention is that it enables a practical realisation of a splice free optical fibre link, especially in conjunction with blown fibre and field mountable connectors.

Assemblies may be made that receive more than one fibre package.

Claims (13)

1. A break out assembly for an optical fibre package that comprises a plurality of optical fibres and an outer covering, the assembly comprising a break out member having a bore with a first portion being adapted to receive the fibre package and a second portion adapted to receive a manifold, the manifold having a plurality of bores for the receipt of exposed fibres from which protective outer covering of the package has been removed and each of the bores communicating with an individual passageway for the fibres that are threaded through the manifold.

2. A break out assembly according to claim 1 further comprising means for securing the fibre package within the break out member.

3. A break out assembly according to claim 1 or claim 2 in which the manifold engages with the break out member.

4. A break out assembly according to claim 1 or claim 2 further comprising means for clamping the manifold in position with respect to the break out tube.

5. A break out assembly according to any preceding claim further comprising a moulded enclosure for the break out tube and manifold.

6. A break out assembly according to claim 5 in which the enclosure comprises means for gripping a fibre package installation duct.

7. A break out assembly according to claim 5 or claim 6 in which a part of the enclosure constitutes the break out member.

8. A break out assembly for an optical fibre package that comprises a plurality of optical fibres and an outer covering, the assembly comprising a casing member for receiving and securing a section of complete fibre package, the casing having a passageway within which the fibres of the package, stripped of the outer covering can spread apart, a manifold providing a plurality of bores through which separate fibres are introduced into individual passageways and means for introducing resin into the passageway.

9. A break out assembly according to claim 2 in which the casing is longitudinally separable with respect to the fibre package.

10. A break out assembly according to any preceding claim in which the individual passageways for the fibres comprise ruggedised terminations.

11. A break out assembly according to any preceding claim in which the entrances to the individual passageways constitute the manifold.

12. A break out assembly according to any preceding claim adapted to receive a plurality of fibre packages.

13. A break out assembly substantially as hereinbefore described with reference to the accompanying drawings.