GB2117895A - Optical microswitch system - Google Patents

Optical microswitch system Download PDF

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Publication number
GB2117895A
GB2117895A GB08209714A GB8209714A GB2117895A GB 2117895 A GB2117895 A GB 2117895A GB 08209714 A GB08209714 A GB 08209714A GB 8209714 A GB8209714 A GB 8209714A GB 2117895 A GB2117895 A GB 2117895A
Authority
GB
United Kingdom
Prior art keywords
optical
fibre
light
microswitch
shutter
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Withdrawn
Application number
GB08209714A
Inventor
David George Dalgoutte
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
STC PLC
Original Assignee
Standard Telephone and Cables PLC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Standard Telephone and Cables PLC filed Critical Standard Telephone and Cables PLC
Priority to GB08209714A priority Critical patent/GB2117895A/en
Publication of GB2117895A publication Critical patent/GB2117895A/en
Withdrawn legal-status Critical Current

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
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means
    • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
    • 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
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
    • G02B6/29361—Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters
    • G02B6/29362—Serial cascade of filters or filtering operations, e.g. for a large number of channels
    • 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
    • G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
    • G02B6/4215—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms the intermediate optical elements being wavelength selective optical elements, e.g. variable wavelength optical modules or wavelength lockers
    • 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
    • G02B6/35—Optical coupling means having switching means
    • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
    • G02B6/353—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being a shutter, baffle, beam dump or opaque element

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Light Control Or Optical Switches (AREA)
  • Switches Operated By Changes In Physical Conditions (AREA)

Abstract

An optical microswitch system having a source 1 and detectors 5, 6 linked by optical fibres 2, 3 with a shutter 4, uses a pair of detectors detecting light of different wavelengths. The switch shutter 4 obstructs only one of these so that detector 6 can be used for monitoring the shutter position while the other detector 5 is used to monitor the integrity of the fibres. A broadband emitter with filters may provide the two wavelengths. Alternatively two emitters may be used and a third detector employed to monitor the source used with the fibre integrity detector 5. <IMAGE>

Description

SPECIFICATION Optical microswitch system This invention relates to an optical microswitch system with remote read-out.
For certain applications such as general process control in hazardous areas it is convenient to monitor the position of some integer by means of a microswitch that operates optically rather than electrically. This may be for instance because the microswitch has to operate in an environment where arcing electrical contacts could cause an explosion. The particular type of optical microswitch system with which the present invention is concerned is one in which light from an optical source is directed to the microswitch along one fibre, and the microswitch incorporates some form of shutter arrangement controlling the coupling of that light into a second fibre for onward transmission to a detector at some point remote from the microswitch.
In a simple system of this type, if no signal is received by the detector, this could be because the system is operating properly and the shutter is in a position designed to block the transmission of light Alternatively it could be because the system is not operating properly and, although the shutter is in a position designed not to block the transmission of light, no light is reaching the detector because one of the fibres has been broken. The present invention employs light of two wavelengths to resolve this particular type of ambiguity for applications requiring high integrity of operation of the microswitch system.
According to the present invention there is provided an optical microswitch system which includes a first optical fibre optically coupled at one end with one end of a second optical fibre, an optical microswitch shutter interposable between said coupled ends, a transmitter adapted to launch light of first and second wavelengths into the other end of the first fibre for transmission to the other end of the second fibre, first and second optical detectors optically coupled with said other end of the second optical fibre and adapted to provide output signals representative respectively of the optical signal strengths at said first and second wavelengths, wherein the shutter construction is such that in one position light of the first wavelength, but substantially none of the second, is coupled from the first fibre into the second, and in another position light of both wavelengths is coupled from the first fibre into the second.
There follows a description of an optical microswitch system embodying the invention in a preferred form. The description refers to the accompanying drawing which shows a schematic of the system.
The output of a light source 1, which may be a composite source rather than a single emitter, is directed into one end of an optical fibre 2. This light source emits at least at two wavelengths y,, and y2, and typically may be provided by two light emissive diodes of different band-gap material, such as a GaAIAs diode operating at 0.85 microns and an InGaAsP diode operating at 1.3 microns, whose outputs are combined typically with a dichroic reflector or by means of a 3 dB optical fibre beam splitter (not shown). The optical fibre 2 extends to a remote location and terminates in a microswitch housing (not shown) where it is optically coupled with second optical fibre 3.The optical coupling may be of the expanded beam type so that a shutter 4 may be interposed between the coupled ends of the two fibres with minimal insertion loss in the ON state.
This shutter takes the form of a dichroic filter which transmits light of the second wavelength, y,, but obstructs light of the first wavelength, y,.
The second optical fibre extends to a monitoring station which is generally, but not necessarily, located next to the transmitter. At this monitoring station the light merging from the end of the second fibre is split so that the component at wavelength y1, is directed to a first photodetector 5 while the component at wavelength Y2 is directed to a second photodetector 6. Conveniently the light is split into its components by means of a dichroic reflector 7.
In operation of the system photodetector 6 monitors the operation of the microswitch shutter while photodetector 5 monitors the integrity of the two optical fibres.
It will be noted that with this system the condition in which the shutter in position to block the launching of light into the second fibre is not distinguished from the faulty condition in which the Y2 wavelength emitter has failed in a manner in which the y,wavelength emitter remains functioning. This ambiguity can simply be resolved by use of a third detector (not shown) directly to monitor the output of the Y2 waveiength emitter, and if the source is adjacent the monitoring station this can simply be done using a short length of optical fibre whose integrity is not in question to couple this third detector to the relevant emitter.
This use of a third detector is not necessary in an alternative embodiment which employs a single broad-band emitter as the source and in which the components at the two wavelengths y and Y2 are obtained by means of conventional filters (not shown).
Claims
1. An optical microswitch system which includes a first optical fibre optically coupled at one end with one end of a second optical fibre, an optical microswitch shutter interposable between said coupled ends, a transmitter adapted to launch light of first and second wavelengths into the other end of the first fibre for transmission to the other end of the second fibre, first and second optical detectors optically coupled with said other end of the second optical fibre and adapted to provide output signals representative respectively of the optical signal strengths at said first and second wavelengths, wherein the shutter construction is such that in one position light of
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Optical microswitch system This invention relates to an optical microswitch system with remote read-out. For certain applications such as general process control in hazardous areas it is convenient to monitor the position of some integer by means of a microswitch that operates optically rather than electrically. This may be for instance because the microswitch has to operate in an environment where arcing electrical contacts could cause an explosion. The particular type of optical microswitch system with which the present invention is concerned is one in which light from an optical source is directed to the microswitch along one fibre, and the microswitch incorporates some form of shutter arrangement controlling the coupling of that light into a second fibre for onward transmission to a detector at some point remote from the microswitch. In a simple system of this type, if no signal is received by the detector, this could be because the system is operating properly and the shutter is in a position designed to block the transmission of light Alternatively it could be because the system is not operating properly and, although the shutter is in a position designed not to block the transmission of light, no light is reaching the detector because one of the fibres has been broken. The present invention employs light of two wavelengths to resolve this particular type of ambiguity for applications requiring high integrity of operation of the microswitch system. According to the present invention there is provided an optical microswitch system which includes a first optical fibre optically coupled at one end with one end of a second optical fibre, an optical microswitch shutter interposable between said coupled ends, a transmitter adapted to launch light of first and second wavelengths into the other end of the first fibre for transmission to the other end of the second fibre, first and second optical detectors optically coupled with said other end of the second optical fibre and adapted to provide output signals representative respectively of the optical signal strengths at said first and second wavelengths, wherein the shutter construction is such that in one position light of the first wavelength, but substantially none of the second, is coupled from the first fibre into the second, and in another position light of both wavelengths is coupled from the first fibre into the second. There follows a description of an optical microswitch system embodying the invention in a preferred form. The description refers to the accompanying drawing which shows a schematic of the system. The output of a light source 1, which may be a composite source rather than a single emitter, is directed into one end of an optical fibre 2. This light source emits at least at two wavelengths y,, and y2, and typically may be provided by two light emissive diodes of different band-gap material, such as a GaAIAs diode operating at 0.85 microns and an InGaAsP diode operating at 1.3 microns, whose outputs are combined typically with a dichroic reflector or by means of a 3 dB optical fibre beam splitter (not shown). The optical fibre 2 extends to a remote location and terminates in a microswitch housing (not shown) where it is optically coupled with second optical fibre 3.The optical coupling may be of the expanded beam type so that a shutter 4 may be interposed between the coupled ends of the two fibres with minimal insertion loss in the ON state. This shutter takes the form of a dichroic filter which transmits light of the second wavelength, y,, but obstructs light of the first wavelength, y,. The second optical fibre extends to a monitoring station which is generally, but not necessarily, located next to the transmitter. At this monitoring station the light merging from the end of the second fibre is split so that the component at wavelength y1, is directed to a first photodetector 5 while the component at wavelength Y2 is directed to a second photodetector 6. Conveniently the light is split into its components by means of a dichroic reflector 7. In operation of the system photodetector 6 monitors the operation of the microswitch shutter while photodetector 5 monitors the integrity of the two optical fibres. It will be noted that with this system the condition in which the shutter in position to block the launching of light into the second fibre is not distinguished from the faulty condition in which the Y2 wavelength emitter has failed in a manner in which the y,wavelength emitter remains functioning. This ambiguity can simply be resolved by use of a third detector (not shown) directly to monitor the output of the Y2 waveiength emitter, and if the source is adjacent the monitoring station this can simply be done using a short length of optical fibre whose integrity is not in question to couple this third detector to the relevant emitter. This use of a third detector is not necessary in an alternative embodiment which employs a single broad-band emitter as the source and in which the components at the two wavelengths y and Y2 are obtained by means of conventional filters (not shown). Claims
1. An optical microswitch system which includes a first optical fibre optically coupled at one end with one end of a second optical fibre, an optical microswitch shutter interposable between said coupled ends, a transmitter adapted to launch light of first and second wavelengths into the other end of the first fibre for transmission to the other end of the second fibre, first and second optical detectors optically coupled with said other end of the second optical fibre and adapted to provide output signals representative respectively of the optical signal strengths at said first and second wavelengths, wherein the shutter construction is such that in one position light of the first wavelength, but substantially none of the second, is coupled from the first fibre into the second, and in another position light of both wavelengths is coupled from the first fibre into the second.
2. An optical microswitch system as claimed in claim 1, wherein a third detector is optically coupled to receive light of the second wavelength directly from the transmitter.
3. An optical microswitch system as claimed in claim 1, wherein the transmitter includes a single light source emitting at both said first and second wavelengths.
4. An optical microswitch system as claimed in claim 3, wherein the source is a broad-band emitter and said first and second wavelengths are selected by optical filtering.
5. An optical microswitch system substantially as hereinbefore described with reference to the accompanying drawing.
GB08209714A 1982-04-01 1982-04-01 Optical microswitch system Withdrawn GB2117895A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08209714A GB2117895A (en) 1982-04-01 1982-04-01 Optical microswitch system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08209714A GB2117895A (en) 1982-04-01 1982-04-01 Optical microswitch system

Publications (1)

Publication Number Publication Date
GB2117895A true GB2117895A (en) 1983-10-19

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB08209714A Withdrawn GB2117895A (en) 1982-04-01 1982-04-01 Optical microswitch system

Country Status (1)

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GB (1) GB2117895A (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1523999A (en) * 1976-05-26 1978-09-06 Gen Motors Corp Optical multifunction control systems for motor vehicles
GB2016684A (en) * 1978-02-15 1979-09-26 Hitachi Ltd Optical measurement system
GB2025608A (en) * 1978-06-02 1980-01-23 Asea Ab Fibre opticalmeasuring devie

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1523999A (en) * 1976-05-26 1978-09-06 Gen Motors Corp Optical multifunction control systems for motor vehicles
GB2016684A (en) * 1978-02-15 1979-09-26 Hitachi Ltd Optical measurement system
GB2025608A (en) * 1978-06-02 1980-01-23 Asea Ab Fibre opticalmeasuring devie

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