SPECIFICATIONAn optical fibre connectorThe object of the present invention is an optical fibre connector.
It has already been proposed, for its connection, to immobilize an optical fibre provided with a plastics material coating inside a tube device through ribs or fillets protruding inside a tube which is longitudinally slit, so that when the tube is being tightened on its outer surface, there appears a deformation of the tongs limited by the slits ensuring the penetration of the fillets or similar in the coating of the fibre.
Now, it has been established that by providing fillets or ribs on the inner surface of a tube which is not slit and is relatively deformable, it was possible to ensure the effective immobilization of the optical fibre provided with its coating by a simple outer tightening operation of the portion of the tube which is opposite the protrusions: the tube becomes deformed in such a manner that not only the fillets are driven into the plastics coating, but also this embedding remains after the tightening effort has ceased.
The tightening effort may be provided by a tool which is currently available in the industry, for instance so-called tube pliers with two jaws leaving a hexagonal housing in which is placed the tube for the tightening operation.
Another object of the invention is an embodiment according which the fillets, advantageously in the form of a tapping or of a threading, are present on a tube or sleeve of semirigid plastics material which is housed inside a metallic tube not slit and the wall of which is relatively thin, the tightening pressure exerted on the metallic tube providing the driving of the protrusions of the sleeve inside the coating of the optical fibre.
It has been established that once the tightening effort has ceased, the deformation of the metallic tube, which is permanent, maintains the protrusions firmly anchored inside the coating of the fibre.
Due to this disposition, one takes advantage not only of the good adaptability of the plastics material forming the sleeve with regards to the outer coating of the fibre, but also it is possible to use metallic tubes with the same diameter for the connection of fibres of different diameters, the adaption to the various diameters of the fibres being possible by an appropriate choice of the thickness of the sleeve wall, said sleeve forming for example part of a set of sleeves.
The user, instead of being compelled to have available as many types of metallic tubes as there are types of optical fibres to be assembed, can use the same type of tube, with the benefit of a simplification of supplies and storage.
The following description, which is given by way of example, refers to accompanying drawing wherein:Figure 1 is a cross-sectional view of a metallic tube device;Figure 2 is an axial section of a sleeve;Figure 3 shows in axial section the constitution of an optical fibre;Figure 4 shows the optical fibre after assembly with the tube; andFigure 5 is a view similar to that of Figure 4, but for an optical fibre of larger diameter than that of the fibre shown in Figure 4.
A'metallic tube device 41 (Figure 1) which has to be fixed on an optical fibre for its connection therewith, comprises a body 42 extending into a relatively thin skirt the thickness of its wall being of the order of a few tenths of a millimetre. For the assembly with an optical fibre, one starts by introducing in the skirt 43 a sleeve 44 (Figure 2), made of a semi-rigid plastics material, advantageously in polyamide of the "nylon" or "rilsan" type, which comprises a cylindrical body 45 with, at one end, a flange 46 of outer diameter iarger than that of the body 45. The inner surface of the sleeve is formed with protrusions, such as for example those formed by a tapping 47.
The sleeve 44 is chosen such that the thickness of its wall 48 allows the introduction with a snug fit inside channel 49 which it provides, of the optical fibre 51 (Fig. 3) formed for example of a core in silica glass 52 and a coating 53 comprising for example an outer layer 54 for the protection, for example in "Tefzel" (registered trade-mark ofDu Pont de Nemours) and a plastics optical layer or sleeve 55 having a refractive index lower that that of the glass.
After the introduction, a crimping operation is carried out by tightening the skirt 43 with pliers, the jaws of which for example delimit a hexagonal housing.
The tightening effort if transmitted by the skirt 43 which is deformed to the body 45 of sleeve 44, and the helical protrusion formed by the tapping 47 drives into the coating 54, without however passing completely through it.
When the tightening effort is released, the skirt 43, which is permanently deformed, maintains in the position reached the body 45 of the sleeve, and the crimping remains.
For an assembly with an optical fibre of larger diameter, one uses a metallic tube 41 of same gauge but which one provides with a sleeve 44' the wall 48' of body 45' having a smaller thickness, as is shown in Figure 5.
On the contrary, for an assembly with an optical fibre of smaller diameter, one uses a sleeve with a thicker wall.
The risks of damage to the coating of the optical fibre are reduced relative to a crimping operation which is carried out with a tapping formed on a metallic wall.
In addition, the crimping effect is betterdistributed: it appears practically on the whole of the periphery of the fibre, in spite of the polygonalshape of the crimping pliers.
Good results are obtained with tighteningpressures varying within wide limits, so that it isnot necessary to set regulations of high precision for the tightening effort.