GB2049976A - Improvements in or relating to clamps - Google Patents

Abstract

A clamp for an optical fibre (1) has a sleeve (14) into which the optical fibre is inserted in a bore (17) and which has slots at each end (15; 16). The sleeve (14) is housed within a connector (4) which has two parts (5, 6) which are screwed together. The screwing together of these parts (5, 6) causes internal surfaces (24a, 24b) of the connector to abut the ends (15, 16) of the sleeve (14). This reduces the width of the slots and hence the circumference of the bore (17) which then grips the optical fibre (1). The optical fibre (1) is thus gripped securely within the connector (4). Hence one end (2) of the optical fibre (1) can be accurately located in a suitable position, relative to the end face (8) of the connector (4). The connector (4) can then be located in a socket (not shown) by means of a plug (26) which screws into the socket. <IMAGE>

Description

SPECIFICATION Improvements in or relating to clamps for optical fibres The present invention relates to clamps for optical fibres and, in particular, to the use of clamping sleeves for individual fibres.

Optical fibres comprise a glass fibre and a jacket coating the glass fibre to protect it. The resultant optical fibre has a diameter of between 50 and 500 surf. Due to the small diameter of the optical fibre, extreme precision is required to hold the fibre end faces in position to achieve the maximum light throughput. This problem arises, in particular, where the light from the fibre is to be incident on a light sensitive diode or where light is to pass from one fibre to another. In such situations, the ends of the fibre must be accurately aligned with the diode or second fibre and, because of this, normal methods of clamping are not practical.

It is known to position the fibres within connectors, the fibres being held in place by adhesives or potting compounds. This is unsatisfactory in many situations, however, because such methods do not allow the fibre to be removed from the connector shouid this be required.

It is also known to hold an optical fibre in place using a rubber sleeve.

According to the present invention there is provided a clamp for an optical fibre comprising a connector having two parts and a sleeve, each having a bore which receives the optical fibre, the sleeve being located within the connector and having ends abutting against internal surfaces of the connector when the two parts of the connector are fitted together, at least one slot being provided in the sleeve extending from the surface to the bore of the sleeve, the pressure of said abutment resiliently deforming the sleeve by a reduction in the width of said at least one slot, said deformation causing a reduction in the circumference of the bore of the sleeve in the region of said slot such that the optical fibre is gripped by the sleeve.

Preferably the at least one slot is situated at one end of the sleeve and more preferably, two slots are provided at each end of the sleeve.

The two parts of the connector are preferably screwed together, the screwing action increasing the abutment pressure of the internal surfaces of the connector on the ends of the sleeve. The two parts may thus be screwed together until the optical fibre is gripped to a sufficient degree.

According to one embodiment of the present invention the jacket is removed from part of the optical fibre and hence the bore of the sleeve has two parts of different diameters, one part corresponding to the diameter of the optical fibre including the jacket and a second part corresponding to the diameter of the glass fibre within the optical fibre.

The present invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, wherein: Figure 1 shows a longitudinai cross section through a connector for an optical fibre having a clamping sleeve according to the present invention; Figure 2 shows a clamping sleeve in elevation; Figure 3 shows a section through a clamping sleeve along the line A-A of Figure 2; and Figure 4 shows a section through a clamping sleeve along the line B-B of Figure 2.

Referring first to Figure 1, an optical fibre 1 comprises an inner glass fibre and an external jacket coating the glass fibre for protection. For one end 2 of the optical fibre 1 to be held in position, the optical fibre 1 is surrounded, adjacent the end 2 to be clamped, by clamping means which is designed to provide adequate support for the fibre. Before inserting the fibre in the clamping means, the jacket is removed from a part 3 of the optical fibre 1 adjacent the end 2 to be held in position. Hence the part 3 of the optical fibre 1 comprises only the glass fibre. This ensures that at least a part of the glass fibre may be gripped directly by the clamping means without the jacket causing any error in positioning of the end 2.

The optical fibre 1 is then inserted into a connector 4 having two parts 5 and 6. The part 6 of the connector 4 which is to receive the part 3 of the optical fibre 1 from which the jacket has been removed is provided with a narrow bore 7 which accurately located the end 2 of the optical fibre 1 in the end 8 of this part 6 of the connector 4. To further increase the accuracy of the positioning of the end 2 of the optical fibre 1, the end 2 may be machined to be flush with the end 8 of the connector 4. The other part 5 of the connector 4, which is screw threaded onto the first part 6 by a threaded region 9, also has a bore 10 which receives part 11 of the optical fibre 1 which has the jacket coating the glass fibre. In each case, the diameter of the bore 7, and 10 corresponds as closely as possible to the diameter of the respective part of the optical fibre 1.

The central regions 12 and 13 of each of the two parts 5 and 6 of the connector 4 have a bore significantly wider than the diameter of the optical fibre 1 and receive a cylindrical metal sleeve 14 with rounded ends 1 5 and 16 (see Fig. 2). The optical fibre 1 passes down the centre of this sleeve in a bore 1 7. In the embodiment shown in Figure 1, the jacket terminates within the sleeve 14 so that the bore 1 7 has two sections, a first section 1 8 having a diameter slightly greater than the diameter of the optical fibre 1 including jacket, and a second section 1 9 having a diameter slightly greater than that of the optical fibre 1 without jacket.

As can be seen from Figure 2, the sleeve 14 is provided with two pairs of slots 20 and 21 , one pair at each end 1 5 and 1 6 of the sleeve 14.

These slots extend from the surface of the sleeve 14 to the central bore 17.

Figures 3 and 4 show the configuration of these slots. Figure 3 shows a section through the sleeve 14 in a region corresponding to the wider part 18 of the bore 17. It is clear from the figure that these slots are in the shape of sectors of the annuius formed by the section through the sleeve 14, the apex of the sector being at the centre of the bore 1 8. Typically, the slots subtend an angle of 200 at the centre ofthe bore 18. In this embodiment the ,two sectors forming the pair 20 are diagonally opposite each other. It can be seen that the part 22 of the slot which is adjacent the central bore 1 8 is narrower than the bore 18 so that the optical fibre 1 cannot be displaced into one of the slots.

Figure 4 shows a section through the sleeve 14 at a region corresponding to the narrower part 19 of the bore 1 7. The pair of slots 21 have a similar and are in a corresponding position relative to the pair of slots 20 shown in Figure 3. The region 23 of the slots adjacent the central bore 19 is again narrower than the bore 1 9 to prevent the optical fibre 1 from being displaced into the slot.

When the two parts 5 and 6 of the connector 4 are threaded together, this reduces the length of the central cavity formed by the wide bore regions 12 and 13 of the two parts 5 and 6 of the connector 4. This causes the rounded ends 1 5 and 16 of the sleeve to abut against internal surfaces 24a and 24b of this central cavity. These internal surfaces 24a and 24b are in the shape of the frustum of a cone and are co-axial with the bores 7 and 10 of the connector 4. The force of this abutment resiliently deforms the sleeve 14 so that the circumference of the sleeve 14 is reduced at the ends 15 and 16 by a reduction in the circumference of the central bore parts 1 8 and 19, the sleeve 14 then pressing onto the optical fibre 1 in the region of the slots. It is this pressure that holds the optical fibre 1 in place within the bore 17.The optical fibre 1 is thus gripped at each end 1 5 and 16 of the sleeve 14, which is located in the central cavity by the abutment of the rounded ends 15 and 16 of the sleeve 14 against the conical surfaces 24a and 24b of the cavity.

It may be noted that the region 25 of the central bore 17 of the sleeve 14, where the transition occurs between the wider bore 18 and narrower bore 19, is tapered. This is to guide the glass fibre 1 into the narrower bore 19 and hence helps to prevent breakage of the optical fibre 1.

The jacket also abuts against this tapered region 25 which assists in locating the optical fibre in position.

The connector 4 is held in place where required by a plug 26 provided with a screw thread 27 which screws into a socket (not shown) at the desired location to which the optical fibre is guided. The plug 26 abuts against one projection 28 on the connector 4 and the socket abuts against a second projection 29. The pressure of the plug 26 and socket on the projections 28 and 29 locates the connector in place.

Claims (13)

1. A clamp for an optical fibre comprising a connector having two parts and a sleeve, each having a bore which receives the optical fibre, the sleeve being located within the connector and having ends abutting against internal surfaces of the connector when the two parts of the connector are fitted together, at least one slot being provided in the sleeve extending from the surface to the bore of the sleeve, the pressure of said abutment resiliently deforming the sleeve by a reduction in the width of said at least one slot, said deformation causing a reduction in the circumference of the bore of the sleeve in the region of said slot such that the optical fibre is gripped by the sleeve.

2. A clamp according to claim 1, wherein said at least one slot is situated at the end of said sleeve.

3. A clamp according to claim 2, wherein there are two slots at each end of the sleeve.

4. A clamp according to claim 3, wherein the two slots at each end of the sleeve are diagonally opposite each other.

5. A clamp for an optical fibre according to any one of the preceding claims wherein said at least one slot is in the form of a sector of an annulus.

6. A clamp according to any one of the preceding claims, wherein said two parts of the connector are fitted together by screw means, said abutment pressure increasing as the two parts are screwed together.

7. A clamp according to any one of the preceding claims, wherein the bore of said sleeve has two regions of different diameters, one of said regions corresponding to the diameter of the optical fibre and the second said region corresponding to the diameter of a glass fibre within said optical fibre.

8. A clamp according to claim 6, wherein the two parts of the connector have bores of.different diameter, one bore diameter corresponding to the diameter of the optical fibre and the second bore diameter corresponding to the diameter of a glass fibre within said optical fibre.

9. A clamp according to any one of the preceding claims, wherein said ends of the sleeve are of rounded shape.

10. A clamp according to any one of the preceding claims, wherein said internal surfaces of the connector are in the shape of the frustom of a cone.

11. A clamp according to any one of the preceding claims, wherein said sleeve is made of metal.

12. A clamp for an optical fibre substantially as herein described with reference to, and as illustrated in the accompanying drawings.

13. A clamp for an optical fibre where the sleeve has slits machined in a vee format see Fig.

3 and Fig. 4.