GB2140576A - Signal transmission system - Google Patents
Signal transmission system Download PDFInfo
- Publication number
- GB2140576A GB2140576A GB08314777A GB8314777A GB2140576A GB 2140576 A GB2140576 A GB 2140576A GB 08314777 A GB08314777 A GB 08314777A GB 8314777 A GB8314777 A GB 8314777A GB 2140576 A GB2140576 A GB 2140576A
- Authority
- GB
- United Kingdom
- Prior art keywords
- optical
- optical waveguide
- waveguide
- printed circuit
- signals
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4246—Bidirectionally operating package structures
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
- G02B6/2852—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using tapping light guides arranged sidewardly, e.g. in a non-parallel relationship with respect to the bus light guides (light extraction or launching through cladding, with or without surface discontinuities, bent structures)
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4256—Details of housings
- G02B6/4257—Details of housings having a supporting carrier or a mounting substrate or a mounting plate
- G02B6/4259—Details of housings having a supporting carrier or a mounting substrate or a mounting plate of the transparent type
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4286—Optical modules with optical power monitoring
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4287—Optical modules with tapping or launching means through the surface of the waveguide
- G02B6/429—Optical modules with tapping or launching means through the surface of the waveguide by surface irregularities on the light guide, e.g. by mechanical modification of the surface of the light guide on its exterior
Abstract
A signal transmission system comprises an optical waveguide (1), a plurality of electro-optical transducers (2,3) and a plurality of opto-electric transducers (4,5). The transducers are arranged adjacent to discontinuities in the surface of the optical waveguide, the discontinuities taking the form of grooves (6,7,8,9). The surface layer of the optical waveguide (1) may have a different refractive index to that of the core or may be a reflective material, the surface layer being selectively removed to form the discontinuities. The system may be used to couple signals between printed circuit boards in electronic apparatus particularly high frequency signals when a metal cored mother board is used. <IMAGE>
Description
SPECIFICATION
Signal transmission system
The invention relates to a signal transmission system comprising an optical waveguide, first means for converting an electrical signal into an optical signal and coupling the optical signal into the optical waveguide, and second means for monitoring the optical signal in the waveguide and producing an electrical signal therefrom. In this specification the term optical signal includes signals having a wavelength in the infra red region of the electromagnetic radiation spectrum as well as the visible light region.
U.K. Patent No. 1,534,786 discloses a data transmission system in which the first means comprises a light emitting diode our a laser, the output of which is coupled to the optical waveguide by means of two further lengths of optical waveguide and a coupling piece and the second means comprises a photodiode which is coupled to optical waveguide by two still further lengths of optical waveguide and the coupling piece. This system suffers from the disadvantage of requiring the assembly of a comparatively large number of parts to couple the signals from the electro-optical transducer into the optical waveguide and from the optical waveguide into the opto-electrical transducer and is consequently relatively expensive.
It is an object of the invention to enable the construction of a signal transmission system in which the coupling of the signals into and out of an optical waveguide can be achieved in a simpler and less expensive way.
The invention provides a signal transmission system as set forth in the opening paragraph, characterised in that the first means comprises an electro-optical transducer situated adjacent to a surface discontinuity in the optical waveguide so as to inject optical signals into the optical waveguide and the second means comprises an opto-electrical transducer situated adjacent a surface discontinuity in the optical waveguide so to detect optical signals therein and convert the optical signals to electrical signals.
The invention is based on the recognition of the fact that surface discontinuities in an optical waveguide cause the emission of optical signals and the signal in the waveguide can be coupled direct from the discontinuity into a detecting device, thus providing a simple and inexpensive coupling from the optical waveguide. Coupling of signals into the optical waveguide can be achieved in a similar manner by placing the optical source close to the surface discontinuity.
The optical waveguide may comprise an optically transparent core having a first refractive index surrounded by a surface layer of material having a different refractive index, the surface discontinuities being formed by local removal of the surface layer.
The provision of the surface layer reduces the losses which would otherwise occur due to contamination of the surface of the waveguide.
In an alternative embodiment the optical waveguide may comprise an optically transparent core having a surface layer of optically reflective material provided thereon, the surface discontinuities being formed by local removal of the surfae layer. A greater proportion ofthe radiation can be coupled into the waveguide by means of the reflective layer since the angle of entry is not critical.
In order to increase the coupling between the transducers and the radiation in the waveguide, the waveguide may be provided with recesses or grooves in which the transducers are located.
The optical waveguide may comprise a circularly cylindrical rod and the two surface discontinuities may be arranged diametrically opposite each other.
The invention further provides electronic apparatus including a plurality of printed circuit boards in which signals from one printed circuit board are transmitted to and received from one or more further printed circuit boards by means of one or more such transmission systems.
In a first embodiment of the electronic apparatus the transducers may be mounted in one or more housings ccarried by the printed circuit boards. In an alternative embodiment the optical waveguides are mounted on a framework or housing and the transducers are mounted in bearings which are retained around the optical waveguides, which housings are constructed for engagement with the printed circuit boards.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure lisa schematic drawing of a signal transmission system according to the invention,
Figure 2 illustrates the coupling of the light signals to and from the transducers,
Figure 3 illustrates an alternative arrangement for coupling light signals to and from the transducers with the two transducers arranged side by side,
Figure 4 is a cross sectional view of the transducers and waveguide with the transducers mounted in a housing which surrounds the waveguide in the region of the discontinuities,
Figure 5 shows an arrangement of a printed circuit board and a plurality of signal transmission systems according to the invention,
Figure 6 is an end elevation of an assembly of a plurality of optical waveguides, and
Figure 7 is a plan view of the assembly of a plurality of optical waveguide shown in Figure 6.
Figure 1 shows diagrammatically a signal transmission system comprising an optical waveguide 1, first and second electro optical transducers in the form of light emitting diodes 2 and 3, and first and second opto-electrical transducers in the form of photodiodes 4 and 5. The light emitting diodes 2 and 3 are located adjacent to grooves 6 and 7 formed in the surface of the waveguide 1. Similarly the photodiodes 4 and 5 are situated adjacent grooves 8 and 9 in the waveguide 1. The grooves 6,7,8 and 9 are provided to increase the coupling between the transducers and the waveguide but are not essential.
A surface scratching would provide some coupling between the transducers and the core of the waveguide. If the outer surface is constructed of a material having a different refractive index from the core then this surface layer should be completely removed in the region where coupling is required. It is also possible to coat the surface of the waveguide with an outer layer of reflective material such as aluminium and in this case it is essential to completely remove the outer layer over the region where coupling is required.
Figure 2 illustrates diagrammatically the coupling of the optical signals from the transducers into and out of the optical waveguide. In Figure 2 the optical waveguide 11 comprises a circularly cylindrical rod, the electro-optical transducer 12 comprises a light emitting diode which is located adjacent to a groove 16 in the cylindrical surface of the waveguide 11, and the opto-electrical transducer 14 comprises a light emitting diode which is situated adjacent to a second groove 18 in the cylindrical surface of the waveguide 11. The grooves 16 and 18 are diametrically opposite each other across the waveguide 11. Light emitted by the light emitting diode 12 is coupled into the waveguide 16 by a groove 16. Where the light strikes the outer surface of the waveguide 11 with an angle greater than the critical angle it will be totally interally reflected and pass along the waveguide.
Similarly lightfrom other light emitting diodes further along the waveguide will pass in both directions along the waveguide and a portion of the light will emerge at the groove 18 and be detected by the photodiode 14 where it emerges from the waveguide through the groove 18. The surfaces of the grooves 16, may be roughened.
Figure 3 shows diametrically an alternative arrangement where the two transducers 22 and 24 are placed side by side on the same side of the waveguide 21 rather than diametrically opposite to each other. The transducers 22 and 24 are located adjacent to a groove 25 formed in the surface of the waveguide 21. This construction is more suitable when transmission in one direction only along the waveguide is desired.
Figure 4 shows an arrangement for locating the transducers adjacent to the discontinuities in the surfaces of the waveguides. As shown in Figure 4, the waveguide 41 is located in a generally U-shaped housing 50. A light emitting diode 42 is located in a bore 43 opposite a groove 46 in the light waveguide 41. Similarly a photodiode 44 is loated in a bore 45 opposite a groove 48 in the waveguide 41. The waveguide 41 is located within the housing 50 by means of two spring loaded wedges 51 and 52.
Electrical connections are made to the light emitting diode 42 and photodiode 44 by any convenient means. The photodiode 44 and light emitting diode 42 may be spring loaded within the bores 43 and 44 so that they bear against the surface of the waveguide when it is located within the housing.
Although the light emitting diodes and photodiodes have been shown located against grooves on the waveguide, it is equally possible to provide hemispherical or other shaped recesses into which the light emitting and photodiodes are positioned.
Further the optical waveguide may have a surface coating of material having a different refractive index, the surface coating being removed in the area around which the photodiode and light emitting diode are located. Alternatively, the optical waveguide may be coated with a reflective material sich as aluminium and the aluminium surface removed over the areas where the light emitting diode and photodiodes are located. Although the embodiments have been described and illustrated using light emitting diodes and photodiodes any convenient form of opto-electric and electro-optic transducers may be used.
An application for which the signal transmission system as described is particularly suitable is in the transmission of signals between two or more printed circuit boards in electronic apparatus. A common method of interconnecting printed circuit boards is to use mother boards on which the printed circuit boards are mounted, the mother boards bearing conductor tracks to provide electrical interconnection between the printed circuit boards. It has been proposed to use mother boards fabricated from a metallic alloy on which a thin insulating layer has been deposited, the conductors being further deposited over the thin insulating layer. The use of a metallic based mother board gives certain advantages, such as structural strength and good heat conducting properties.However, since a thin insulating layer is provided between an electrically conductive metallic core and the conductive tracks interconnecting the printed circuit boards a large stray capacitance is formed. This limits the bandwidth of the signals which may be transmitted between the printed circuit board. In order to overcome this disadvantage it is proposed to use optical transmission for the signals having high frequencies. The signal transmission system described hereinbefore enables this to be done economically by providing an inexpensive coupling between the electrical signals and the optical waveguide.
Figure 5 shows part of electronic apparatus including a printed circuit board 60 which is mounted on a mother board 61 by means of an edge connector 62.
A housing 63 is mounted in an aperture formed in the mother board 61 by means barbs 64 and 65 and carries three optical waveguides 66, 67 and 68. The housing 63 carries a photodiode and a light emitting diode for each optical waveguide in a manner similar to that shown in Figure 4. The rear 69 of the housing 63 is formed as a printed circuit board edge connectorto enable connection between the printed circuit board 60 and the light emitting and photodiodes within the housing 63. Alternatively the housing 63 may be formed integrally with the printed circuit board and be arranged to mate with the mother board 61 when the printed circuit board 60 is plugged into the edge connector 61. In this case further means must be provided to hold the optical waveguides 66, 67, 68 in position when the printed circuit board is removed. The mother board 61 may extend only so far as to accommodate the pritned circuit board edge connectors with the housing 63 attached to a frame or housing which may also support the mother board. Such mechanical expe dientswill be readily apparent to one skilled in the art.
Figures 6 and 7 illustrate an alternative form for the optical waveguide which is particularly suitable for use when a comparatively large number of optical waveguides is required. Figure 6 is an end elevation of an array of optical waveguides 70-1 to 70-n which are separated by reflective spacers 71-1 to 71-n -1. Reflective surfaces 72,73, 74 and 75 surround the array of optical waveguides. Figure 7 is a plan view of the array shown in Figure 6. The reflective surface 74 of the array is removed in strips, two of which are shown 76 and 77, to expose the optical waveguide at various points along its length.
The transducers are placed over these areas to couple the signals into and out of the respective waveguides. This arrangement gives a compact multi-conductor array. The construction of the array may be similar to that of the Light Control Film (louvred filters) sold by Minnesota Mining and
Manufacturing Co. This film provides a sheet of optically transparent film containing spaced louvres.
By choosing a suitable film and coating the outer surfaces an array as shown in Figures 6 and 7 may be constructed.
Claims (13)
1. A signal transmission system comprising an optical waveguide, first means for converting an electrical signal into an optical signal and coupling the optical signal into the optical waveguide, and second means for detecting the optical signal in the optical waveguide and producing an electrical signal therefrom, characterised in that the first means comprises an electro-optical transducer situated adjacent to a surface discontinuity in the optical waveguide so as to couple optical signals into the optical waveguide and the second means comprises an opto-electrical transducer situated adjacent a surface discontinuity in the optical waveguide so as to detect signals there-in and to convert the optical signals to electrical signals.
2. A system as claimed in Claim 1, in which the optical waveguide comprises an optically transparent core having a first refractive index surrounded by a surface layer of material having a second refractive index, the surface discontinuities being formed by local removal of the surface layer.
3. A system as claimed in Claim 1, in which the optical waveguide comprises an optically transparent core having a surface layer of optically reflective material provided thereon, the surface discontinuities being formed by local removal of the surface layer.
4. A system as claimed in any of Claims 1 to 3, in which the surface discontinuities comprise recesses formed in the waveguide.
5. A system as claimed in Claim 4, in which the recesses are formed as grooves.
6. A system as claimed in any preceding claim in which the discontinuities are roughened.
7. A system as claimed in any preceding claim in which the optical waveguide a circularly cylindrical rod.
8. A system as claimed in Claim 7, in which two surface discontinuities are arranged diametrically opposite each other.
9. A data transmission system substantially as described herein with reference to the accompanying drawings.
10. Electronic apparatus including a plurality of printed circuit boards in which signals from one printed circuit board are transmitted to and received from one or more further printed circuit boards by means of one or more signal transmission systems as claimed in any of Claims 1 to 9.
11. Electronic apparatus as claimed in Claim 10, in which the electro-optical and opto-electrical transducers are mounted in one or more housings carried by the printed circuit boards.
12. Electronic apparatus as claimed in Claim 10, in which the optical waveguides are mounted on a framework or housing and the transducers are mounted in housings which are retained around the optical waveguides, which housings are constructed for engagement with the printed circuit boards.
13. Electronic apparatus substantially as described herein with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08314777A GB2140576A (en) | 1983-05-27 | 1983-05-27 | Signal transmission system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08314777A GB2140576A (en) | 1983-05-27 | 1983-05-27 | Signal transmission system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8314777D0 GB8314777D0 (en) | 1983-07-06 |
| GB2140576A true GB2140576A (en) | 1984-11-28 |
Family
ID=10543504
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08314777A Withdrawn GB2140576A (en) | 1983-05-27 | 1983-05-27 | Signal transmission system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2140576A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0271177A2 (en) * | 1986-08-01 | 1988-06-15 | Spectran Specialty Optics Company | Optical fibre coupler |
| US4826274A (en) * | 1986-12-24 | 1989-05-02 | Motorola, Inc. | Optical coupling arrangements including emitter and detector placed inside of a hollow closed end reflective waveguide |
| EP0350720A2 (en) * | 1988-07-15 | 1990-01-17 | Eckard Design Gmbh | Optical fibre adapted for data transmission and bus system for a motor vehicle |
| WO1990013835A1 (en) * | 1989-05-03 | 1990-11-15 | Robert Bosch Gmbh | A coupling component for a light-waveguide |
| AU641674B2 (en) * | 1989-08-01 | 1993-09-30 | Nippon Telegraph & Telephone Corporation | Embedded-in-optical-fiber type optical component |
| EP2707766A4 (en) * | 2011-05-10 | 2015-07-08 | Invensys Sys Inc | Multi-drop optical communication |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB629174A (en) * | 1945-10-31 | 1949-09-14 | Marconi Wireless Telegraph Co | Improvements in or relating to signal transmission systems |
| GB1376630A (en) * | 1970-12-26 | 1974-12-11 | Fuji Photo Film Co Ltd | Photoelectric converting optical fibre and method of making the same |
| GB2031182A (en) * | 1978-09-18 | 1980-04-16 | Siemens Ag | Optical waveguid arrangements |
| GB1569952A (en) * | 1976-01-27 | 1980-06-25 | Thomson C | Electrooptical branching device and method of manufacturing the same |
| GB1575468A (en) * | 1976-03-18 | 1980-09-24 | Patelhold Patentverwertung | Optical fibre data transmission system |
| GB2056111A (en) * | 1977-09-30 | 1981-03-11 | Siemens Ag | Optical arrangements |
-
1983
- 1983-05-27 GB GB08314777A patent/GB2140576A/en not_active Withdrawn
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB629174A (en) * | 1945-10-31 | 1949-09-14 | Marconi Wireless Telegraph Co | Improvements in or relating to signal transmission systems |
| GB1376630A (en) * | 1970-12-26 | 1974-12-11 | Fuji Photo Film Co Ltd | Photoelectric converting optical fibre and method of making the same |
| GB1569952A (en) * | 1976-01-27 | 1980-06-25 | Thomson C | Electrooptical branching device and method of manufacturing the same |
| GB1575468A (en) * | 1976-03-18 | 1980-09-24 | Patelhold Patentverwertung | Optical fibre data transmission system |
| GB2056111A (en) * | 1977-09-30 | 1981-03-11 | Siemens Ag | Optical arrangements |
| GB2031182A (en) * | 1978-09-18 | 1980-04-16 | Siemens Ag | Optical waveguid arrangements |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0271177A2 (en) * | 1986-08-01 | 1988-06-15 | Spectran Specialty Optics Company | Optical fibre coupler |
| EP0271177A3 (en) * | 1986-08-01 | 1990-02-07 | Ensign-Bickford Optics Co. | Optical fibre coupler |
| US4826274A (en) * | 1986-12-24 | 1989-05-02 | Motorola, Inc. | Optical coupling arrangements including emitter and detector placed inside of a hollow closed end reflective waveguide |
| EP0350720A2 (en) * | 1988-07-15 | 1990-01-17 | Eckard Design Gmbh | Optical fibre adapted for data transmission and bus system for a motor vehicle |
| EP0350720A3 (en) * | 1988-07-15 | 1991-09-11 | Eckard Design Gmbh | Optical fibre adapted for data transmission and bus system for a motor vehicle |
| WO1990013835A1 (en) * | 1989-05-03 | 1990-11-15 | Robert Bosch Gmbh | A coupling component for a light-waveguide |
| US5163105A (en) * | 1989-05-03 | 1992-11-10 | Robert Bosch Gmbh | Coupling component for a light-waveguide |
| AU641674B2 (en) * | 1989-08-01 | 1993-09-30 | Nippon Telegraph & Telephone Corporation | Embedded-in-optical-fiber type optical component |
| EP2707766A4 (en) * | 2011-05-10 | 2015-07-08 | Invensys Sys Inc | Multi-drop optical communication |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8314777D0 (en) | 1983-07-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |