GB1576336A

GB1576336A - Optical waveguide connectors

Info

Publication number: GB1576336A
Application number: GB4666676A
Authority: GB
Original assignee: Post Office
Current assignee: Post Office
Priority date: 1977-11-09
Filing date: 1977-11-09
Publication date: 1980-10-08

Description

(54) IMPROVEMENTS IN OR RELATING TO OPTICAL WAVEGUIDE CONNECTORS (71) We, THE POST OFFICE, a British corporation established by Statute of 23 Howland Street, London W1P 6HQ, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to dielectric optical waveguide connectors and methods of connecting dielectric optical waveguides.

It is an object of the present invention to provide a connector for connecting dielectric optical waveguides and a method of connecting them which allow by means of simple adjustments a connection to be made and the light transmission capacity between the waveguides to be varied so that a particular or optimum coupling between the waveguides may be chosen.

Accordingly, the present invention in a first aspect provides a dielectric optical waveguide connector icluding : - first and second optical waveguide retaining means, at least one of which comprises a first retaining member made of rigid material and a second retaining member made of resilient material, said first retaining member having an optical waveguide receiving groove and said second retaining member being adapted to be located, at least partly, within said groove to hold an optical waveguide in the groove; and Coupling means for holding said first and second optical waveguide retaining means at relative locations such that the lengths of the dielectric optical waveguides when retained in the respective retaining means are maintained substantially parallel but not overlapping and allowing independent rotation of the retaining means about respective, substantially parallel, spaced apart axes, each axis being spaced from the axis of the waveguide when retained in the corresponding retaining means so that the light transmission capacity between the ends of the waveguides retained in the respective retaining means may be varied; and the coupling means having an inner surface being disposed around said first retaining member so that the resilient second retaining member bears on said inner surface and holds the corresponding retaining means in a fixed position with respect to the coupling means when a desired rotational position is chosen.

The coupling means may be adapted to hold said first and second retaining means at positions such that respective facing end surfaces of the retaining means are in substantially the same plane to allow the end surfaces of dielectric optical waveguides when retained in the retaining means to be brought into contact and the area of contact varied.

Each of said first and second optical waveguide receiving means comprises respectively a first retaining member made of rigid material and a second retaining member made of resilient material, said first retaining member having an optical waveguide receiving groove and said second retaining member being adapted to be located, at least partly, within said groove to hold an optical waveguide in the groove.

In a second aspect the present invention provides apparatus for aligning the ends of two dielectric optical waveguides to be connected by a connector as defined above and in which the first and second optical waveguide retaining means are substantially cylindrical in shape, the apparatus including means for supporting the coupling means of the connector, first and second mechanical gripping means adapted to grip a respective one of the two waveguide retaining means when located in the coupling means, each of the gripping means being rotatably mounted on support means for independent rotation about an axis corresponding to the longitudinal axis of the corresponding retaining means when located in the apparatus.

The apparatus may include a worm gearing arrangement operative to rotate the gripping means and hence the respective retaining means.

In a third aspect the present invention provides a method of coupling the ends of a pair of dielectric optical waveguides comprising : locating respective end portions of the waveguides in receiving grooves in respective ones of a pair of first waveguide receiving members made of rigid material; pressing resilient second retaining members into the respective receiving grooves thereby forming waveguide retaining means that hold the waveguides in the grooves; mounting the retaining means in a common coupling means so that when so mounted the positions of the optical wave guides held in the retaining means are; substantially parallel and not overlapping, the coupling means allowing independent rotation of the retaining means about respective, substantially parallel, spaced apart axes, each axis being spaced from the axis of the corresponding waveguide; independently rotating the retaining means with respect to the coupling means to vary the light transmission capacity between the ends of the waveguides; and allowing the resilient second retaining members to bear against an inner surface of the coupling means to hold the retaining means in a fixed position relative to the coupling means when a desired position is chosen.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings. In the drawings: Figure 1 is an exploded view of a dielectric optical waveguide connector; Figure 2 is an illustration of a cap for use with the connector of Figure 1; Figure 3 is an axial cross-section of part of the connector of Figure 1 and the cap of Figure 2 that illustrates an initial alignment procedure for use with the connector; Figure 4 is an axial cross-section of the assembled connector of Figure 1 showing parts of the connector in elevation; Figure 5 is an explanatory diagram of the method of alignment of the connector; and Figure 6 is a perspective view of apparatus for use with the connector of Figure 1.

6 wherein the longitudinal axis of the portion Referring to Figure l, a dielectric optical waveguide connector comprises: first and second dielectric optical waveguide retaining means in the form of optical waveguide holders 1 and 2 respectively; and a coupling member 3.

The waveguide holders 1 and 2 are identical and each comprises interfitting members 4 and 5. The members 4 are optical waveguide receiving members and each has the shape of a cylinder with a cut away sectorial portion which defines a longitudinally extending V-shaped channel 6. In use, a portion of a dielectric optical waveguide is located in the shaped channel of the waveguide is offset but parallel to the longitudinal axis of the respective receiving member 4. The members 5 are optical waveguide clamping members and each has a uniform sectorial cross-section and each is made of a soft plastic material.

The apical portion of each member 5 is shaped to fit in the channel 6 of the corresponding member 4. Each member 5 is slightly radially longer than the cut away sectorial portion of the cylindrical shape of which shape the corresponding member 4 forms a part. Hence each member 5, when fitted in a corresponding channel 6, may be radially compressed to provide with its respective member 4 an assembled waveguide holder of cylindrical shape. The members 5 have an axial extent less than that of the receiving members 4 for a reason that is explained below.

The coupling member 3 is tubular and comprises- two portions 7 and 8 having respective circular bores 9 and 10 which are radially offset to a small extent. The two bores 9 and 10 have equal longitudinal extent and equal radii slightly greater than the cross-sectional radius of the cylindrical waveguide holders 1 and 2. The longitudinal extent of each of the bores 9 and 10 is approximately equal to that of each of the clamping members 5 and thus less than that of each of the receiving member 4.

In aligning a dielectric optical waveguide in the channel 6 of one of the holders 1, 2 use is made of two caps 11, one of which is shown in Figure 2. Referring to Figure 2, a cap 11 has a circular bore 12 closed at one end by a surface 13. The radius of the bore 12 is slightly greater than the cross-sectional radius of the cylindrical waveguide holders 1 and 2. A recess 20 is provided in the inner wall of the cap to accommodate a waveguide clamping member 5 so that the waveguide holder may be inserted without radial compression into the bore 12 of the cap. The surface 13 is convex and truncated in a region around its centre.

The two waveguide receiving members 4.

the coupling member 3 and the two caps 11 are made of glass-loaded noryl (R.T.M.), a material that is resistant to distortion when subject to stress and is accurately mouldable whilst also being suitable for use in injection moulding processes.

Referring now to Figure 3, the initial stage of the method employed in using the connector is the accurate location, in their respective waveguide holders 1 and 2, of two dielectric optical fibres 14 and 15 whose ends are required to be joined. A method of locating the optical fibres in their holders will now be described. Since the method is the same for both fibres 14 and 15, the method will be described with reference to optical fibre 14 only.

In the method the optical fibre 14 is placed along the V-shaped channel 6 of the waveguide receiving member 4 so that the end of the fibre does not quite extend to the end of the channel 6. The waveguide clamping member 5 is pressed down on to the portion of the fibre 14 situated in the channel 6. This pressure may be applied by an operator using his thumb and forefinger. The cap 11 is then pressed over the end of the assembled waveguide holder 1 so that its surface 13 contacts the end of the waveguide receiving member 4 and so that its recess 20 receives the end of the clamping member 5. The waveguide and clamping member are then slid along the channel 6 until the end of the fibre abuts the truncated portion of the internal cap surface 13.

The end surface of the fibre 14 will then be flush with the end surface of the waveguide receiving member 4.

It will be appreciated that the portion of the fibre 14, thus located by the method, has its longitudinal axis offset from the longitudinal axis of the receiving member 4. The caps 11 are removed from the waveguide holders and the holders are then ready for insertion into the coupling member 3.

Referring to Figures 4 and 5, the ends of the waveguide holders 1 and 2 with which the ends of the fibres 14 and 15 are flush are inserted into opposite ends of the tubular coupling member 3 so that the ends of the holders 1 and 2 are in contact. The resilience of the clamping members 5 ensures that the holders 1 and 2 are tightly held in bores 9 and 10 respectively of the coupling member 3. Since the optical fibres 14 and 15 are offset with respect to the longitudinal axes 16 and 17 of holders 1 and 2, rotation of one- of the holders relative to the coupling member 3 causes the end of the fibre held by it to describe a circular path about the longitudinal axis of the respective holder. Since the bores 9 and 10 of the coupling member 3 are slightly offset the circular paths 18, 19 of the respective ends of the fibres will also be offset. The offsetting of the bores 9 and 10 is however only slight so that, as viewed from along either af the longitudinal axis of the bores as shown in Figure 5, the two circular paths 18, 19 of the ends of the fibres overlap.

Thus, the two waveguide holders may be independently rotated with respect to the coupling member 3 to bring the ends of the fibres 14 and 15 into contact and to vary the area of contact.

A small quantity of epoxy resin may be placed on the end surface of one of the members 4 before insertion into the coupling member 3 to alleviate the effect of refractive index discontinuities at the joint between the fibres and to cement the whole assembly in a selected position.

Referring now to Figure 6, apparatus for independently rotating the two waveguide holders includes a heavy base platform 20 having a vertically projecting clamp holder 21 at its centre. The clamp holder 21 has a plastics bush in which is supported a shaft 22 for a clamp 23. Two tubular rods 24 and 25 are mounted horizontally at respective first ends thereof in pedestals 28 and 29, the rods being supported so that their longitudinal axes are co-incident.

The tubular rods have respective narrow apertures 30 and 31 extending longitudinally from their outer surfacse to their respective interiors.

The rods 24 and 25 are received in a horizontal bore in a respective one of two clamping blocks 34 and 35 which are free to rotate about the respective rods. Each of the clamping blocks 34 and 35 comprises a cylindrical portion, eg 32, extending from a position adjacent the respective pedestal 28 and 29 to an integral co-axial cylindrical portion 36, 37 of larger diameter. The facing ends of the cylindrical portions 36 and 37 of the clamping blocks are each integral with a respective circular flange 38, 39 and a respective rectangular projecting portion 40, 41.

A narrow slot 42; 43 extends from each of the horizonal bores in the clamping blocks to the upper surface of each of the parts of the clamping blocks 34, 35; each slot extending along the full length of the clamping block.

A respective slot 44, 45 is also formed in the upper surface of each of the pedestals 28 and 29 which extends into the rodreceiving space 26, 27 in the pedestals. Thus the space inside each of the rods 24 and 25 is, when the appartus is first set up, in communication with the space outside the apparatus via the apertures 30 and 31 in the rods and the slots 42, 43, 44, and 45 in the clamping blocks and pedestals re spectively.

Each of the rectangular projecting portions 40 and 41 of the clamping blocks supports a short horizontal rod 46, 47 off set from the axis of rotation of the clamping blocks. The rods 46 and 47 connect the clamping blocks with respective clamps 48 and 49 for the waveguide holders 1 and 2.

Each of the clamps 48 and 49 includes a support member 50, 51 for a waveguide holder, the support member being pivotally connected at one end to a clamping member 52, 53.

The two members of each of the clamps 48 and 49 have opened and closed positions, the latter being illustrated in Figure 6, at which positions they are held by interconnecting pairs of springs 68 and 69. The support members 50 and 51 of the clamps have respective recesses that receive the ends of the waveguide holders 1 and 2.

The support members also include respective waveguide receiving blocks 54 and 55 each having a channel therein whose lower surface is disposed along a line continuing from the lower surface of the bores of the respective tubular rods 24 and 25.

The clamping members 52 and 53 have wedge-shajed projections 56, 57 on their lower surfaces which are operative to engage the respective waveguide holders by fitting into the channel 6 in these holders. The apical edge of each of the projections 56 and 57 is truncated and the angle of the wedge is chosen so that the wedge does not contact the bottom of the channel 6 and hence will not bear on a waveguide when located in the channel.

Each of the cylindrical portions 36 and 37 of the clamping blocks 34 and 35 has a circumferential plastics band 58, 59 with worm gear teeth. Each gear band 58 and 59 has a slot located over the corresponding slot in the clamping blocks. The cylindrical portion thus acts as a worm wheel which is turned by a worm 60, 61 extending beneath the respective clamping block and supported by brackets from the respective pedestal.

Each worm shaft carries an adjusting wheel 62, 63 at one end and an extension in the form of an M6 screw (not shown) at its other end. Each M6 screw operates in a respective slideway and has a stop at the end of its travelling distance. These stops put a limit on the available turns of the worm and hence on the worm wheel, the limits being such that only turns of the worm wheel of up to 1 270 are allowed.

Tn operation, the two portions 14 of the optical fibres to be joined are located in the receiving members 4 as previously described and the waveguide holders 1 and 2 com prising the respective receiving members 4 and clamping members 5 are inserted into the coupling member 3 after adhesive has been applied to their ends. The coupling member is then fixed in 'the clamp 23 which when inserted in the holder 21 prevents the coupling member 3 from rotating about its axis. The plastics bush in the clamp holder 21 is a tight fit about the clamp shaft 22 which holds the coupling member 3 in position but allows this position to be varied.

When the apparatus is set up the slots 42 and 43 in the clamping blocks and the slots 44 and 45 in the pedestals are aligned and receive the optical fibres extending from the waveguide holders 1 and 2. The optical fibres are then supported in the bores of the rods 24 and 25 respectively.

The ends of the waveguide receiving members 4 are supported in channels in the cuamp supporting members 50 and 51, and as previously mentioned the clamping members 5 are shorter than the receiving members 4 so that a portion of the respective channel 6 at the projecting end of each of the receiving members 4 is exposed. The clamping member 52 and 53 are then closed on to the waveguide holders 1 and 2 so that the wedge projections 56 and 57 are located in the exposed portions of the channels 6. The adjusting wheels 62 and 63 are then turned independently to rotate the waveguide holders 1 and 2 to align the fibre ends. By using a light source and light meter at the free ends of the respective fibres the holders may be rotated to a relative position at which the optical alignment of the fibres is at a maximum.

WHAT WE CLAIM IS: 1. A dielectric optical waveguide connector including: first and second optical waveguide retaining means, at least one of which comprises a first retaining member made of rigid material and a second retaining member made of resilient material, said first retaining mmeber having an optical waveguide receiving groove and said second retaining member being adapted to be located, at least partly, within said groove to hold an optical waveguide in the groove; and coupling means for holding said first and second optical waveguide retaining means at relative locations such that the lengths of the dielectric optical waveguides when retained in the respective retaning means are maintained substantially parallel but not overlapping and allowing independent rotation of the retaining means about respective, substantially parallel, spaced apart axes, each axis being spaced from the axis of the waveguide when retained in the corresponding retaining means so that the light transmission capacity between the ends of the waveguides retained in the respective retaining means may be varied; and he coupling means having an inner surface being disposed around said first retaining member so that the resilient second retaining member bears on said inner surface and holds the corresponding retaining means in a fixed position with respect to

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. clamping blocks with respective clamps 48 and 49 for the waveguide holders 1 and 2. Each of the clamps 48 and 49 includes a support member 50, 51 for a waveguide holder, the support member being pivotally connected at one end to a clamping member 52, 53. The two members of each of the clamps 48 and 49 have opened and closed positions, the latter being illustrated in Figure 6, at which positions they are held by interconnecting pairs of springs 68 and 69. The support members 50 and 51 of the clamps have respective recesses that receive the ends of the waveguide holders 1 and 2. The support members also include respective waveguide receiving blocks 54 and 55 each having a channel therein whose lower surface is disposed along a line continuing from the lower surface of the bores of the respective tubular rods 24 and 25. The clamping members 52 and 53 have wedge-shajed projections 56, 57 on their lower surfaces which are operative to engage the respective waveguide holders by fitting into the channel 6 in these holders. The apical edge of each of the projections 56 and 57 is truncated and the angle of the wedge is chosen so that the wedge does not contact the bottom of the channel 6 and hence will not bear on a waveguide when located in the channel. Each of the cylindrical portions 36 and 37 of the clamping blocks 34 and 35 has a circumferential plastics band 58, 59 with worm gear teeth. Each gear band 58 and 59 has a slot located over the corresponding slot in the clamping blocks. The cylindrical portion thus acts as a worm wheel which is turned by a worm 60, 61 extending beneath the respective clamping block and supported by brackets from the respective pedestal. Each worm shaft carries an adjusting wheel 62, 63 at one end and an extension in the form of an M6 screw (not shown) at its other end. Each M6 screw operates in a respective slideway and has a stop at the end of its travelling distance. These stops put a limit on the available turns of the worm and hence on the worm wheel, the limits being such that only turns of the worm wheel of up to 1 270 are allowed. Tn operation, the two portions 14 of the optical fibres to be joined are located in the receiving members 4 as previously described and the waveguide holders 1 and 2 com prising the respective receiving members 4 and clamping members 5 are inserted into the coupling member 3 after adhesive has been applied to their ends. The coupling member is then fixed in 'the clamp 23 which when inserted in the holder 21 prevents the coupling member 3 from rotating about its axis. The plastics bush in the clamp holder 21 is a tight fit about the clamp shaft 22 which holds the coupling member 3 in position but allows this position to be varied. When the apparatus is set up the slots 42 and 43 in the clamping blocks and the slots 44 and 45 in the pedestals are aligned and receive the optical fibres extending from the waveguide holders 1 and 2. The optical fibres are then supported in the bores of the rods 24 and 25 respectively. The ends of the waveguide receiving members 4 are supported in channels in the cuamp supporting members 50 and 51, and as previously mentioned the clamping members 5 are shorter than the receiving members 4 so that a portion of the respective channel 6 at the projecting end of each of the receiving members 4 is exposed. The clamping member 52 and 53 are then closed on to the waveguide holders 1 and 2 so that the wedge projections 56 and 57 are located in the exposed portions of the channels 6. The adjusting wheels 62 and 63 are then turned independently to rotate the waveguide holders 1 and 2 to align the fibre ends. By using a light source and light meter at the free ends of the respective fibres the holders may be rotated to a relative position at which the optical alignment of the fibres is at a maximum. WHAT WE CLAIM IS:

1. A dielectric optical waveguide connector including: first and second optical waveguide retaining means, at least one of which comprises a first retaining member made of rigid material and a second retaining member made of resilient material, said first retaining mmeber having an optical waveguide receiving groove and said second retaining member being adapted to be located, at least partly, within said groove to hold an optical waveguide in the groove; and coupling means for holding said first and second optical waveguide retaining means at relative locations such that the lengths of the dielectric optical waveguides when retained in the respective retaning means are maintained substantially parallel but not overlapping and allowing independent rotation of the retaining means about respective, substantially parallel, spaced apart axes, each axis being spaced from the axis of the waveguide when retained in the corresponding retaining means so that the light transmission capacity between the ends of the waveguides retained in the respective retaining means may be varied; and he coupling means having an inner surface being disposed around said first retaining member so that the resilient second retaining member bears on said inner surface and holds the corresponding retaining means in a fixed position with respect to

the coupling means when a desired rotational position is chosen.

2. A dielectric optical waveguide connector as claimed in claim 1 wherein said coupling means is adapted to hold said first and second retaining means at positions such that respective facing end surfaces of the retaining means are in substantially the same plane to allow the end surfaces of dieletcric optical waveguides when retained in the retaining means to be brought into contact and the area of contact varied.

3. A dielectric optical waveguide connector as claimed in claim 1 wherein each of the first and second optical waveguide receiving means comprises respectively a first retaining mmeber made of rigid material and a second retaining member made of resilient material, said first retaining member having an optical waveguide receiving groove and said second retaining member being adapted to be located, at least partly, within said groove to hold an optical waveguide in the groove.

4. A dielectric optical waveguide connector as claimed in claim 3 wherein the waveguide receiving grove in each of said first retaining members is V-shaped in cross section and the respective parts of the second retaining mmebers adapted to be located in the groove is V-shaped in cross section.

5. A dielectric optical waveguide connector as claimed in claim 3 or claim 4 wherein the first and secsond optical waveguide retaining means are cylindrical in shape and are adapted to hold respective dielectric optical waveguides at respective locations such that the longitudinal axis of the portion of the respective waveguide held by each waveguide retaining means is substantially parallel to, but slightly offset from, the longitudinal axis of the corresponding waveguide retaining means.

6. A dielectric optcial waveguide connector as claimed in claim 5 wherein the coupling means comprises a tubular member having two portions with respective circular bores that are parallel, but radially offset, which bores, in use, receive respectively said first and second waveguide retaining means.

7. A dielectric optical waveguide connecting assembly compriisng a dielectric optical waveguide connector as claimed in any one of claims 3 to 6 including an end cap for the or each first retaining member to provide an abutment surface for the end of a dielectric optical waveguide when located in the receiving grove of the first retaining member.

8. A dielectric optical waveguide connecting assembly as claimed in claim 7 wherein the abutment surface of the end cap is provided by a truncated convex inner surface of the end cap.

9. A dielectric optical waveguide connecting assembly as claimed in claim 7 or claim 8 wherein the end cap has a recess on its inner surface to accommodate the second retaining member.

10. Apparatus for aligning the ends of two dielectric -optical waveguides to be connected by a connector as claimed in claim 3 in which the first and second optical waveguide retaining means are substantially cylindrical in shape, the apparatus including means for supporting the coupling means of the connector, first and second mechanical gripping means adapted to grip a respective one of the two waveguide retaining means when located in the coupling means, each of the gripping means being rotatably mounted on support means for independent rotation about an axis corresponding to the longitudinal axis of the corresponding retaining means when located in the apparatus.

11. Apparatus as claimed in claim 10 wherein said gripping means comprises a clamping member having wedge-shaped projection that is adapted to partially fit in the waveguide receiving groove of the corresponding first retaining member.

12. Apparatus as claimed in claim 10 or claim 11 including a worm gearing arrangement operative to rotate the gripping means and hence the respective retaining means.

13. Apparatus as claimed in any one of claims 10 to 12 including two elongate members having channels therein for receiving the respective free ends of the dielectric optical waveguide when held in the respective receiving means.

14. Apparatus as claimed in claim 13 wherein the elongate members are the mountings on which the respective gripping means are supported for rotation.

15. A method of coupling the ends of a pair of dielectric optical waveguides comprising: locating respective end portions of the waveguides in receiving grooves in respective ones of a pair of first waveguide receiving members made of rigid material; pressing resilient second retaining members into the respective receiving grooves thereby forming waveguide retaining means that hold the waveguides in the grooves; mounting the retaining means in a common coupling means so that when so mounted the positions of the optical waveguides- held in the retaining means are substantially parallel and not overlapping, the coupling means allowing independent rotation of the retaining means about respective, substantially parallel, spaced apart axes, each axis being spaced from the axis of the corresponding waveguide; independently rotating the retaining means with respect to the coupling means to vary the light transmission capacity between the ends of the waveguides; and allowing the resilient second retaining members to bear against an inner surface of the coupling means to hold the retaining means in a fixed position relative to the coupling means when a desired position is chosen.

16. A method as claimed in claim 15 wherein the ends of the waveguides are made flush with respective end surfaces of the respective first retaining members, the retaining 'means are held in the coupling means so that the facing ends surfaces of the retaining means are in substantially the same plane, and the retaining means are moved to vary the area of contact between the waveguide end surfaces.

17. A method as claimed in claim 16 including the step of locating the end of each waveguide flush with the end surface of the corresponding first retaining member by fitting a removable end cap on the end of the first retaining member, so that the inner end surface of the cap contacts the end surface of the first retaining member and sliding the optical waveguide along the receiving groove until its end abuts said inner end surface of the cap.

18. A dielectric optical waveguide connector substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 6 of the accompanying drawings.

19. A dielectric optical waveguide connecting assembly substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 5 of the accompanying drawings.

20. A method of coupling the ends of pair of dielectric optical waveguides substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 6 of the accompanying drawings.

21. Apparatus for aligning the ends of two dielectric optical waveguides substantially as hereinbefore described with reference to and as illustrated in Figure 6 of the accompanying drawings.