Optical fibre adapter means

Abstract: A two-part optical fibre adapter means suitable for coupling optical signals in electronic shelf assemblies incorporating plug-in circuit boards for high density racked optical systems. One part (1) of the adapter means is mounted in an aperture (10) in a support member (11) and has a thread (4) which is provided for attachment of an optical-fibre connector (23). The other part (2) incorporates a light-emitting diode (12) and is resiliently mounted by means of a helical spring (15) in an aperture (13) in a further support member (14). The other part (2) which takes the form of a spigot slidably locates in a bore (3) of the one part (1) and cooperates with a pin (24) of the optical fibre connector (23) which is attached to the one part (1). A plurality of the optical-fibre adapter means are mounted on an equipment shelf back-plane and a printed circuit board. Use of adapter means of this type eliminates the requirement for inter-link cables between the back-plane and the p.c.b. which have been required hitherto in such equipment-shelf assemblies.

Description: The present invention relates to a two-part optical fibre adapter means. This invention is eminently suitable for coupling optical signals in electronic shelf assemblies incorporating plug-in printed circuit boards particularly, although not exclusively, for high density racked optical systems. A problem with optical fibre connection schemes employing, say, SMA and ST type connectors is that they are not designed with high density racked optical systems in mind. In a large racked system, for instance, for efficient cable management it is preferable for the optical fibre connections to be from the rear of the printed circuit board frames. Where conventionally mounted active devices e.g. light emitting diodes and photo detectors are employed, in order to remove a printed circuit board, it is necessary to part, or completely withdraw a printed circuit board from the frame to demate the optical terminations, from the active devices mounted on the board. A disadvantage of this arrangement is that it is a time-consuming operation and it gives rise to a further disadvantage in that the cable management arrangement must provide enough cable slack to allow at least partial card removal to demate the optical terminations. Once demated these terminations are potentially vulnerable to damage, or contamination. Additionally it is also quite possible they could drop within the card frame and cause electrical short circuits. An alternative configuration is disclosed in DE-A-2741585. This involves an adapter having a first part which houses an optical fibre and which is secured to a frame for receiving a plug-in module, and a second part forming part of the module and incorporating a receiver photo-diode, the second part sliding into the first part when the module is inserted in the frame. The main disadvantage of this arrangement is that it is complicated to assemble and is unsuitable for use with conventional electronic shelf assemblies. An object of this invention is to provide an optical fibre adapter means which overcomes the beforementioned disadvantages in an efficient manner and which enables active printed circuit board devices to be interfaced to any standard optical fibre connectors. According to a first aspect of the invention there is provided a two-part optical fibre adapter means comprising a first adapter part for receiving an optical fibre connector containing an optical fibre and secured to a first support member, and a second adapter part which contains an opto-electronic device and is mounted in a second support member, the second part including a guide portion adapted for slidable location within a bore of the first part, characterised in that the first part includes attachment means for detachably securing thereto the optical fibre connector containing the optical fibre, and in that the adapter means further comprises resilient means for resiliently mounting the second part on the second support member so as to be capable of movement with respect to the second support member laterally and longitudinally relative to the direction of insertion of the second part in the first part, whereby the second part is dynamically alignable with the first part during the said insertion for directly optically coupling the opto-electronic device and the optical fibre. Preferably the first part is of cylindrical configuration and has a central through-bore and is firmly secured within an aperture incorporated in the first support member. The first support member preferably carries several such parts. The first part may be adapted, by means of an external thread, to enable attachment to one of its ends, of the optical fibre connector. Desirably the optical fibre connector is of the male type where the central protruding pin locates loosely and centrally within the central through-bore of the first adapter part. Advantageously, the second adapter part has the form of a spigot, and the resilient means is arranged so as to be axially effective for biasing the spigot into one position in the aperture, from which position the spigot is capable of movement longitudinally against the resilient means, and also laterally as a consequence of a differential in diameter dimensions of the aperture and the spigot. Conveniently the spigot is of an increasing external diameter stepped cylindrical configuration and incorporates a central throughbore which opens into a cavity at the larger diameter end of the spigot. The cavity is adapted for containment of the active opto-electronic device such as a light emitting diode or a photo-detector. Conveniently a first step of the spigot is provided for limiting the degree of insertion of the spigot within the central bore of the first adapter part, and a second step is provided for containing the spigot within the aperture on the further support member under the pressure of the resilient means, which preferably takes the form of a helical spring contained in the second support member by a securing means such as a plate. The first support member may comprise a plate which incorporates at least one pin which is arranged for co-operation with an appropriately positioned hole within the second support member. Such pins and holes may be provided to assist accurate alignment of the two-part adapter means. Conveniently, the first support member is mounted adjacent one part of a standard printed circuit board electrical connector, e.g. of the DIN 41612 type, on a back-plane assembly of an electronic equipment shelf. The second support member can be mounted adjacent the corresponding cooperating other part of the standard printed circuit board electrical connector on a plug-in printed circuit board assembly. Thus, as the printed circuit board assembly is slidably inserted, or removed from the equipment shelf, the two-part adapter means slidably engages or disengages respectively. The invention further provides a two-part optical-fibre adapter means as set forth above in combination with an electronic equipment shelf assembly including a back-plane and slidably mounted plug-in printed circuit boards for direct coupling between active opto-electronic devices on the printed circuit board and optical fibre connector means on the back-plane. According to a second aspect of the invention, there is provided a printed circuit board frame assembly comprising the combination of a printed circuit board frame having a first support member and at least one first optical fibre adapter part mounted on the first support member and shaped to receive an optical fibre connector containing an optical fibre, and at least one plug-in printed circuit board assembly to be received in the frame, the board assembly including a second support member arranged to be located in registry with the first support member when the board assembly is inserted in the frame, and at least one second adapter part which contains an active opto-electronic transducer for coupling to the optical fibre, the second adapter part including a guide portion adapted for slidable location within a bore of the first adapter part, characterised in that the first part includes attachment means for detachably securing thereto the optical fibre connector containing the optical fibre, and in that the board assembly includes resilient means for resiliently mounting the second part on the second support member so as to be capable of movement with respect to the second support member laterally and longitudinally relative to the direction of insertion of the second part in the first part, whereby the second part is dynamically alignable with the first part during the said insertion for directly optically coupling the transducer and the optical fibre. The invention will now be described by way of example with reference to the drawings, in which:- Figure 1 is a sectional view of interengaging components of a two-part adapter means in accordance with the invention; Figure 2 is a sectional view of the two-part adapter means mounted on first and second support members which are displaceable relative to each other; Figure 3 is a sectional view of the two-part adapter means shown mounted on a back-plane assembly and a printed circuit board respectively of an electronic equipment shelf; Figure 4 is a diagrammatic side elevation of a back-plane and printed circuit board incorporating several two-part adapter means; Figure 5 is a diagrammatic plan view of the assembly shown in Figure 4; and Figure 6 is a diagrammatic end elevation of the assembly shown in Figures 4 and 5. Referring to the drawings, in Figure 1 the two main parts 1 and 2 of an optical fibre adapter are shown. One part 1, which is generally of cylindrical configuration, incorporates a central through-bore 3 and an external threaded portion 4. The other part 2, is also of cylindrical configuration and takes the form of a spigot. The spigot 2 also incorporates a central through-bore 5 which opens into a cavity 6 at one end of the spigot. The spigot 2 incorporates two external stepped regions 7 and 8 of increasing diameter while the cavity 6, which is at the large diameter end, has an internal shoulder 9. Figure 2 has the two-part adapter means fitted together with each part mounted on its respective support member. The one part 1, is secured within an aperture 10 on a support member 11 as a consequence of an interference fit with the aperture. The other part 2, the spigot, contains an active opto-electronic or electro-optic device i.e. a light emitting diode 12 within the cavity 6. The spigot 2 is resiliently mounted within an aperture 13 on a further support member 14 by means of a helical spring 15 providing axial pressure against the spigot 2. The spring 15 and spigot 2 are contained within the aperture 13 by means of a securing plate 16. The spigot is held against an internal shoulder 17 of the aperture 13 by the spring 15 and longitudinal movement is possible in one direction against the pressure of the spring 15 when necessary, particularly when an optical fibre connector described below is inserted and screwed home until tight. This is when the pin of the connector enters the spigot, the shoulder on the pin comes into contact with the end of the spigot which moves it against the pressure of the spring. A degree of lateral movement of the spigot can be obtained as a result of a gap 18 present between the spigot 2 and the wall of the aperture 13 as a consequence of a differential in the diameters of the large end of the spigot 2 and the aperture 13. This lateral movement aids accurate alignment of the spigot with the aperture 3 of the one part 1 of the adapter. As will be seen in Figure 2, electrical connections such as 19 emanating from the light emitting diode 12 pass through a suitably positioned opening 20 in the support member 16 and are terminated on tags such as 21 on a tag strip 22. This tag strip 22 is connected with, and supported by, a printed circuit board (described below with reference to Figure 3, Figure 4, Figure 5 and Figure 6). The one part 1 of the adapter means is arranged to receive a standard optical fibre connector 23 of the types known as SMA, ST etc., the protruding pin 24 locating snugly within the central through-bore 5 of the spigot 2. The optical fibre connector is retained securely in position by the appropriate part of the connector being tightened on the threaded portion 4 of the one part 1 of the adapter. By this arrangement, the adapter means is enabled to couple optical signals directly from an active opto-electronic device, e.g. a light emitting diode 12 to an optical fibre connector 23 without the necessity of an optical fibre link involving the customary cable slack. Referring now to Figure 3, Figure 4, Figure 5 and Figure 6 it should be understood that like component parts as referred to in Figure 1 and Figure 2 have been designated with identical numerals as referred to in Figure 1 and Figure 2. In Figure 3 the support member 11 is shown secured to an upper rail 25 and a lower rail 26 of an equipment shelf back-plane. The further support member 14 is shown secured by means of screws 27 and 28, to a plug-in printed circuit board 29. Figure 4 shows a plurality (three) of optical adaptor means mounted on the back-plane and printed circuit board 29 respectively. In Figure 4 the printed circuit board 29 is shown partially withdrawn, and it will be seen that the support member 11 incorporates two pins 30 and 31, positioned at opposite ends of the member. Cooperating holes 32 and 33 positioned at opposite ends of the further support member 14 are provided to accommodate the pins 30 and 31 and assist in accurate alignment of the two-part adapters as the plug-in printed circuit board 29 is slidably pushed home to effect mating of DIN 41612 electrical connectors 34 and 35 (see Figure 5). Standard securing arrangements for the printed circuit board are shown in the form of screws 36 and 37 which are screwed into appropriate holes (not shown) in a main shelf assembly 38 and 39. Accordingly this arrangement enables active board-mounted devices to be interfaced to standard optical fibre connectors (SMA, ST etc.) which remain permanently connected at the rear of the back-plane assembly alongside the DIN 41612 electrical connectors. There is no requirement for inter-link cables between back plane and printed circuit boards and hence no need for cable slack to remove a printed circuit board. Accordingly printed circuit boards can simply be removed from the shelf assembly to break all optical connections. To re-connect these optical connections, the card is simply re-inserted. It should be understood that although the optical fibre connector shown in the described embodiment incorporates a threaded attachment means, other attachment means, for instance, a bayonet type, could be employed. Additionally, it should also be understood that while the adapter means are shown mounted adjacent DIN 41612 electrical connectors, they could be placed in any convenient location at the rear of the printed circuit board, even conveniently within apertures on the DIN 41612 connector itself.

Claims: A two-part optical fibre adapter means comprising a first adapter part (1) for receiving an optical fibre connector containing an optical fibre and secured to a first support member (11), and a second adapter part (2) which contains an opto-electronic device (12) and is mounted in a second support member (14), the second part (2) including a guide portion adapted for slidable location within a bore (3) of the first part (1), characterised in that the first part (1) includes attachment means (4) for detachably securing thereto the optical fibre connector containing the optical fibre, and in that the adapter means further comprises resilient means (15) for resiliently mounting the second part (2) on the second support member (14) so as to be capable of movement with respect to the second support member (14) laterally and longitudinally relative to the direction of insertion of the second part (2) in the first part (1), whereby the second part (2) is dynamically alignable with the first part (1) during the said insertion for directly optically coupling the opto-electronic device (12) and the optical fibre. An adapter means according to claim 1, characterised in that the first part (1) is of cylindrical configuration and has a central through-bore (3) and is firmly secured within an aperture (10) incorporated in the first support member (11). An adapter means according to claim 2, characterised in that the attachment means comprises an external thread (4) on the first part (1). An adapter means according to claim 3, characterised in that the first part (1) is arranged to receive an optical fibre connector (23) of the male type having a central protruding pin (24), the central protruding pin locating loosely and centrally within the central through-bore (3) of the first part (1). An adapter means according to any preceding claim, characterised in that the second part (2) takes the form of a spigot, and in that the resilient means (15) is arranged so as to be longitudinally effective for biasing the spigot (2) into one position in an aperture (13) in the second support member (14), from which position the spigot (2) is capable of movement longitudinally against the resilient means (15), and also laterally as a consequence of a differential in diameter dimensions of the aperture (13) and the spigot (2). An adapter means according to claim 5, characterised in that the spigot (2) is of an increasing external diameter stepped cylindrical configuration and incorporates a central through-bore (5) which opens into a cavity (6) at the larger diameter end of the spigot (2). An adapter means according to claim 6, characterised in that the cavity (6) is adapted for containment of the opto-electronic device (12). An adapter means according to any preceding claim, characterised in that the opto-electronic device (12) is a light emitting diode. An adapter means according to any of claims 1 to 7, wherein the opto-electronic device (12) is a photo-detector. An adapter means according to claim 6, characterised in that the spigot (2) has an external step (7) which limits the degree of insertion of the spigot (2) within a central bore (3) of the first part (1), the step (7) being of a greater outer diameter than an inner diameter of the central bore (3). An adapter means according to claim 6 or claim 10, characterised in that the spigot (2) has a second external step (8) for retaining the spigot (2) within the aperture (13) in the further support member (14) against a shoulder (17) of the aperture (13) under the pressure of the resilient means, the second external step (8) having an outer diameter which is greater than an inner diameter of the shoulder (17). An adapter means according to any preceding claim, characterised in that the resilient means (13) is a helical spring contained in the further support member (14) by a securing means. An adapter means according to any preceding claim, characterised in that the first support member (11) comprises a plate which incorporates at least one pin (30, 31) arranged for co-operation with an appropriately positioned hole (33) in the second support member (14). A back-plane assembly for an electronic equipment shelf (38, 39), the assembly incorporating an adapter means according to any preceding claim, characterised in that the first support member (11) of the adapter means is mounted adjacent one part of a standard printed circuit board electrical connector (34, 25) of the assembly (25, 26). A plug-in printed circuit board assembly including a back-plane assembly according to claim 14 and a printed circuit board, characterised in that the second support member (14) of the adapter means is adopted to be mounted on the printed circuit board adjacent a corresponding and co-operating other part (35) of the standard printed circuit board electrical connector (34, 25) on the printed circuit board. An electronic equipment shelf assembly (38, 39) including a back-plane (25, 26), adapter means according to any preceding claim, and slidably mounted plug-in printed circuit boards (29) for direct coupling between (a) active opto-electronic devices (12) mounted in the adapter means and connected to the printed circuit boards (29) and (b) optical fibre connector means on the back-plane. A printed circuit board frame assembly comprising the combination of a printed circuit board frame having a first support member (11) and at least one first optical fibre adapter part (1) mounted on the first support member and shaped to receive an optical fibre connector containing an optical fibre, and at least one plug-in printed circuit board assembly to be received in the frame, the board assembly including a second support member (14) arranged to be located in registry with the first support member (11) when the board assembly is inserted in the frame, and at least one second adapter part (2) which contains an active opto-electronic transducer (12) for coupling to the optical fibre, the second adapter part (2) including a guide portion adapted for slidable location within a bore (3) of the first adapter part (1), characterised in that the first part (1) includes attachment means (4) for detachably securing thereto the optical fibre connector containing the optical fibre, and in that the board assembly includes resilient means (15) for resiliently mounting the second part (2) on the second support member (14) so as to be capable of movement with respect to the second support member (14) laterally and longitudinally relative to the direction of insertion of the second part (2) in the first part (1), whereby the second part (2) is dynamically alignable with the first part (1) during the said insertion for directly optically coupling the transducer (12) and the optical fibre. An assembly according to claim 17, characterised in that the first part (1) has a central through-bore (3) and is arranged to receive in the bore (3) a central protruding pin of a male type optical fibre connector. An assembly according to claim 17 or claim 18, characterised in that the attachment means comprises an external screw thread (4) on the first part (1). An assembly according to any of claims 17 to 19, characterised in that the resilient means (15) is arranged to act longitudinally. An assembly according to claim 18, characterised in that the second part (2) is in the form of a spigot arranged to be received in the central through-bore (3) of the first part (1), and in that the spigot (2) has a central longitudinal bore (5) for receiving a pin of the connector. An assembly according to claim 21, characterised in that the spigot (2) is of an increasing external diameter stepped cylindrical configuration and the central longitudinal bore (5) opens into a cavity (6) at the larger diameter end of the spigot (2) which houses the transducer (12).

Inventors: HUGHES HOWARD GLYN, HUGHES, HOWARD GLYN
Applicants: PINACL COMMUNICATION SYSTEMS L, PINACL COMMUNICATION SYSTEMS LIMITED
Application year: 1988
Main classification: G02B6
IPC codes: G02B6