GB2201561A

GB2201561A - Data handling systems

Info

Publication number: GB2201561A
Application number: GB8729112A
Authority: GB
Inventors: Robert William Davies; Robert James; Stephen Michael Small
Original assignee: GEC Marconi Ltd; Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1986-12-15
Filing date: 1987-12-14
Publication date: 1988-09-01
Also published as: GB2201561B; GB8629921D0; GB8729112D0

Abstract

A data handling system comprising a multiplicity of data processing modules (5a - 5e) releasably retained in a racking system (1) and an optical data link arrangement (13) interconnecting the modules (5a - 5e), the optical data link arrangement comprising an elongated light path in the form of one or more light transmissive bars (21, 23) interconnecting the modules (5a - 5e) and to which the modules (5a - 5e) are coupled by way of reflection at respective partially light reflective, partially light transmissive members extending across the light path. In the embodiment of Fig 1, bar 21 is used for transmission only, bar 23 being used for reception. In an alternative embodiment a single bar is used for transmission and reception. The bars may be replaced by hollow tubes. If the modules are not aligned a flexible bar may be used (Fig 6 not shown). Signalling may be effected using TDM or WDM. <IMAGE>

Description

Data Handling Systems This invention relates to data handling systems.

More particularly the invention relates to data handling systems of the kind comprising a multiplicity of data processing modules which are releasably retained in a racking system and means interconnecting the modules for the transmission of data therebetween.

In conventional forms of such a system each module comprises a circuit board carrying electric components and connections between the components, and at least one connector part, e.g. an edge connector connected with said components and adapted to mate with a respective one of a multiplicity of complementary connector parts carried on a mother circuit board, or backplane which provides the desired interconnections between the modules.

Such systems may be highly complex and have a large number of modules thereby necessitating a complex, bulky and therefore possibly unreliable-backplane.

It is an object of the present invention to provide a data handling system wherein this problem is alleviated.

According to the present invention there is provided a multiplicity of data processing modules releasably retained in a racking system and an optical data link arrangement interconnecting said modules wherein said optical data link arrangement comprises an elongated light path interconnecting said modules and to which at least one of said modules is coupled by way of reflection at a partially light reflective, partially light transmissive member extending across said light path at a position along the length of the light path.

In-one particular embodiment of the invention each of a plurality of said modules is coupled to a first portion of said light path by way of a respective one of a plurality of first said members at spaced positions along said first portion to effect transmission to one end of said first portion, and is coupled to a second portion of said light path by way of a respective one of a said plurality of second said members at spaced positions along said second portion for reception from one end of said second portion, and means is provided for causing light exiting from said one end of said first portion to pass along said second portion from its said one end.

In another particular embodiment of the invention each of a plurality of said modules is coupled to said light path by way of a respective one of a plurality of said members at spaced positions along said light path to effect transmission to one end of said light path, and for reception of light from said one end, and means is provided for causing light reaching said one end of said light path to return along said light path.

Two data handling systems in accordance with the present invention 11 now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a partly cut away perspective view of the first system; Figures 2 and 3 are schematic diagrams illustrating the configuration of an optical data link arrangement of the system of Figure 1; Figure 4 is a partly cut away perspective view of the second system; Figure 5 is a schematic diagram illustrating the configuration of an optical data link arrangement of the system of Figure 4; and- Figure 6 is a schematic diagram illustrating the configuration of a modification of the optical data link arrangement of Figure 5.

Referring to Figure 1, the first system comprises a racking system in the form of a cabinet 1 in which are releasably retained, at speed positions set by guides 3, a number of modules 5a- 5e. Each module 5a - 5e comprises one or more circuit boards (not shown) carrying electric components and connections between the components.

Each module 5a - 5e further includes an edge connector 7 connected with the components and adapted to mate when the module is in the cabinet 1 with a respective one of a number of complementary connector parts carried on a mother circuit board or backplane (not shown), extending along the inside of the rear wall 9 of the cabinet 1. This electronic backplane arrangement provides any required power supply connections between the modules, and any other connections requiring solid permanent connection.

Connection between the modules for the transmission of data therebetween is effected by way of an optical data link arrangement 13 secured to and extending along the upper surface of the top side 11 of the cabinet 1. The optical link'arrangement includes a light path between the modules provided by bars of light transmissive material of rectangular cross-section. The light path comprises spaced parallel portions constituted respectively by bars 21 and 23 which are optically connected via a further bar 15 having reflectors in the form of coatings '7 and 19 at interfaces between sections of the bar 15.

In respect of each module 5a - 5e, a hole 25 in the topside 27 of the module 5a - 5e and a corresponding hole 29 In the topside 11 of the cabinet 1 enables the module 5a - 5e to be optically coupled to the bar 21. Similarly, in respect of each module 5a - 5e, a hole 31 in the topside 27 of the module 5a - 5e and a corresponding hole 33 in the topside 11 of the cabinet 1 enables the module 5a - 5e to be optically coupled to the bar 23.

Referring also to Figures 2 and 3, which illustrate schematically the configuration of the parallel portions of the optical data link arrangement 13 viewed from the rear of the cabinet 1, each bar 21 and 23 has at intervals along its length adjacent holes 29 or 33 a plurality of partially light reflective, partially light transmissive planar members 35a - 35d or 37a - 37d in the form of coatings at interfaces between sections of the bars 21, 23. The planes of the coatings 35a - 35d, 37a - 37d are parallel, and included at an angle of 450 to the longitudinal axis of the bar 21, 23 in which they are located.Adjacent one end 39, 41 of each bar 21, 23, adjacent end hole 29 or 33, there Is a planar reflective member 35e or 37e which is also in the form of a coating at the interface between two sections of the bar 21 or 23, the plane of the coatings 35e and 37e being parallel to the planes of the other coatings 35a - 35d or 37a - 37d.

As illustrated schematically in Figures 2 and 3, adjacent each of the holes 25, 31 in the upper side 27 of each module 5a - 5e is a lens 43. Each lens 43 adjacent a hole 31 is positioned so as to receive light passing into the module 5a - 5e via the hole 31 and focus it onto a photodiode 45.

Each lens 43 adjacent a hole 25 is positioned so as to receive light from a light emitting diode 47 in the module 5a - 5e and collimate it so as to pass out of the module 5a - 5e via the hole 25.

In operation of the first system, each module communicates with other modules by causing its light emitting diode 47 to emit light via the associated lens 43 and holes 25 and 29 into the bar 21.

The emitted light is subsequently incident on and reflected by the adjacent member 35 to pass along the bar 21, through any intervening members 3F n the end 49 of the bar 21. Upon emergence from the end 49 the light is incident on and reflected by the reflector 17, passes along the bar 15, is incident on and reflected by the reflector 19 and enters the end 51 of the bar 23. The light then passes along the bar 23 and is incident on and at least partially reflected at each of the members 37 and passes through the holes 33 and 31 and the associated lens 43 of each module 5 to reach the photodiode 45 of each module 5.

It will be noted that each module 5a - 5e is thus coupled by way of the members 35a - 35e of the bar 21 for transmission only and by way of the members 37a - 37e of the bar 23 for reception only.

Referring to Figure 4, the second system to be described comprises a racking system in the form of a cabinet 101 in which are releasably retained, at positions set by guides 103, a number of modules 105a - 105e. Each module comprises one or more circuit boards 104 carrying electric components 106 and connections between the components 106 and an edge connector 107 connected with the components 106 and adapted to mate when the module is in the cabinet with a respective one of a number of complementary connector parts carried on a mother circuit board or backplane 108, the backplane being mounted within an electromagnetic hazard and environmental shield 110, extending along the Inside of the rear wall 109 of the cabinet 101.A ventilation channel 112 is located just below the top side 111 of the cabinet 10I. Mounted within the upper part of the shield 110 is an optical data link arrangement 113.

Referring also to Figure 5, which illustrates schematically the configuration of the optical data link arrangement 113 when viewed from the top of the cabinet 101, in respect of each module 105a - 105e a hole 125 in the rear wall 127 of the module 105a - 105e and a corresponding hole 124 in a wall of the shield 110 enables the module 105a - 105e to be optically coupled to the optical data link arrangement 113. The arrangement 113 comprises an elongate bar 130 of rectangular cross-section and made of light transmissive material.

Spaced apart at intervals along the length of the bar 130 adjacent holes 124 are a plurality of partially light reflective, partially light transmissive planar members 131a - 131d in the form of coatings at interfaces between sections of the bar 130. The planes of the coatings X R - 131d are parallel and inclined at an angle of 45" to the longitudinal axis of the bar 130. Adjacent one end 133 of the bar 130 and spaced from the coating 131d by the above-mentioned interval is a planar reflective member 131e also in the form of a coating at the interface between two sections of the bar 130, the plane of the coating 131e being parallel to the plane of the other coatings 131a - 131d. Adjacent the other end 145 of the bar 130 is a 90" angled mirror 147.

As illustrated schematically in Figure 5, adjacent each of the holes 125 in the rear side 127 of each module 105a - 105e is a rectangular housing piece 135. Fixed within the side of each piece 135 facing the hole 125 are a pair of lenses 137, 139. Also housed within each piece 135 are a light emitting diode 141 and a photodiode 143. The lens 137 is positioned so as to receive light from the light emitting diode 141 and collimate it so as to pass out of the module 105a - 105e via the hole 125. The lens 139 is positioned so as to receive light passing into the module 105a - 105e via the hole 125 and focus it onto the photodiode 143.

In operation of the second system, each module communicates with other modules by causing its light emitting diode 141 to emit light via the associated lens 137 and holes 125 and 124 into the bar 130. The emitted light is subsequently incident on and reflected by the adjacent member 131 to form a beam passing along the bar 130, through any intervening members 131 to the 90" angled mirror 147 at the end 145 of the bar 130. Thereat the light is reflected back along the bar 130, in a beam parallel to and spaced from the beam incident on the mirror 147, and is at least partially reflected at each to member 131 to pass through the holes 124 and 125 and the lens 139 of each module 105 to reach the photodiode 143 of each module 105.

It will be noted that each module 105a - 105e is optically coupled to the bar 130 for transmission and reception by way of a respective single member 131a - 131e.

It will be appreciated that each member 131a - 131e need not be arranged to couple a single module to the bar 130 for transmission and reception but could be arrangd to couple one module to the bar 130 for transmission only and couple another module to the bar 130 for reception nly.

it will be understood that in the systems of Figures 1 and 4 the transmissivity and reflectivity characteristics of the members 35, 37, 131 are preferably chosen to make the attenuation of the light beam between modules as nearly constant as possible irrespective of the module from which the light is emitted and the module to which the light is intended to go.

It will be further understood that in the systems of Figures 1 and 4 data intended to reach one module also reaches all the other modules but that a data management arrangement is provided within the modules so that the other modules will ignore this received data.

The data management arrangement could be, for example, a command/response, token passing or time division multiplexing arrangement. If wavelength division multiplexing techniques are used in conjunction with the optical data link arrangement parallel transmission via the arrangement can occur, the bit width of the arrangement being determined by the number of wavelengths used.

It will be further appreciated that the optical data link arrangements 13, 113 of the systems of Figures 1 and 4 need not comprise solid light transmissive bars 21, 23, 130 but could comprise hollow tubes along which are positioned a plurality of members having appropriate reflectivity and transmissivity characteristics.

Apertures, in the walls of the tubes to enable the modules to be optically coupled to the members in the tubes.

It is desirable that the optical data link arrangements 13, 113 do not impose a strict requirement on the alignment of the modules with respect to one another. A modification of the optical data link arrangement 113 is shown in Figure 6 wherein such a strict requirement is not imposed.

Referring to Figure 6, in the modification a flexible guiding optical bar 201 is used. Spaced apart at intervals along the length of the bar 201 are a plurality of planar members 202a - 202e, having appropriate reflectivity and transmissivity characteristics in the form of coatings at interfaces between sections of the bar 201.

The plane of each member 202a - 202e is inclined at an angle of 45" to the longitudinal axis of the bar 201. Each of a plurality of module 203a - 203e is optically coupled to the bar 201 by way of a respective member 202a - 202e. A retro-reflector 206 is positioned at one end of the bar 201 so that light incident on the reflector 206 is reflected back along its incident path. In operation of a system incorporating the modification, the transmitted and received beams therefore occupy the same space when guided along the bar 201. In addition the beams have a substantial cross-sectional area so that small flexing of the bar 201 does not prevent the reflected light beam reaching the modules 203a - 203e. The bar 201 is shown in an exaggerated bent position in Figure 6.

Since a transmitted and a received beam will pass from and to each of the modules 202a - 202e along the same path only one lens 204 is needed for each module 203a - 203e. The light emitting diode and the photodiode in a module are thus required to occupy the same area and a dual purpose device 205, for example a polo diode, is therefore used.

Claims

1. A data handling system comprising a multiplicity of data processing modules releasably retained in a racking system and an optical data link arrangement interconnecting said modules wherein said optical data link arrangement comprises an elongated light path interconnecting said modules and to which at least one of said modules is coupled by way of reflection at a partially light reflective, partially light transmissive member extending across said light path at a position along the length of the light path.

2. A system according to Claim 1 wherein said one module is coupled to said light path by way of a first said member for transmission and by way of a second said member for reception.

3. A system according to Claim 2 wherein each of a plurality of said modules is coupled to a first portion of said light path by way of a respective one of a plurality of first said members at spaced positions along said first portion to effect transmission to one end of said first portion, and is coupled to a second portion of said light path by way of a respective one of a said plurality of second said members at spaced positions along said second portion for reception from one end of said second portion, and means is provided for causing light exiting from said one end of said first portion to pass along said second portion from its said one end.

4. A system according to Claim 1 wherein said one module is coupled to said light path for transmission and reception by way of a single said member.

5. A system according to Claim 4 wherein each of a plurality of said modules is coupled to said light path by way of a respective one of a plurality of said members at spaced positions along said light path to effect transmission to one end of said light path, and for reception of light from said one end, and means is provided for causing light reaching said one end of said light path to return along said light path.

6. A system according to any one of the preceding claims wherein said light path is provided in one or more bars of solid light transmissive material and the or each said member comprises a coating at an interface between sections of a said bar.

7. A system according to Claim 6 wherein said material is a flexible material.

8. A system according to Claim 7 when dependent on Claim 5 wherein the light transmitted to said one end of said light path forms a beam of substantial cross-sectional area and occupies substantially the same space as light returning along said path from said one end'of said light path.

9. A system according to any one of the preceding claims wherein said light path is provided in a structure secured to said racking system.

10. A system according to Claim 9 wherein the or each said module is arranged to direct light onto and/or receive light from an associated said member via a path including an air gap to facilitate withdrawal of the or each said module from the racking system.

11. A system according to any one of the preceding claims wherein the or each said member is a planar member at an angle of substantially 450 to said light path.

12. A data handling system according to Claim 1 and substantially as hereinbefore described with reference to Figures 1, 2 and 3 or Figures 4 and 5 or Figure 6.