CA1298116C - Bidirectional optical space switch - Google Patents
Bidirectional optical space switchInfo
- Publication number
- CA1298116C CA1298116C CA000557564A CA557564A CA1298116C CA 1298116 C CA1298116 C CA 1298116C CA 000557564 A CA000557564 A CA 000557564A CA 557564 A CA557564 A CA 557564A CA 1298116 C CA1298116 C CA 1298116C
- Authority
- CA
- Canada
- Prior art keywords
- array
- inputs
- cells
- outputs
- optical
- 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.)
- Expired - Fee Related
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Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/29—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the position or the direction of light beams, i.e. deflection
- G02F1/31—Digital deflection, i.e. optical switching
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
- G02B27/283—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for beam splitting or combining
- G02B27/285—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for beam splitting or combining comprising arrays of elements, e.g. microprisms
-
- 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
- G02B6/27—Optical coupling means with polarisation selective and adjusting means
- G02B6/2706—Optical coupling means with polarisation selective and adjusting means as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters
-
- 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
Abstract
ABSTRACT (ref. Fig 1) BIDIRECTIONAL OPTICAL SPACE SWITCH
A bidirectional optical space switch for selectively coupling an input signal to a selected output comprises two arrays of inputs (19 8), two arrays of outputs (5, 9), polarising beam splitters (2, 4), and a matrix of cells (3) each of which is selectively capable of varying the polarisation state of light passing through it in response to an applied control signal. A first optical system (5) couples each of inputs (1) and a corresponding one of outputs (9) with a corresponding column of cells while a second optical system (7) couples each of inputs (8) and a corresponding one of outputs (5) with a corresponding row of cells. One of inputs (1) is switched to one of outputs (5) by activating the appropriate cell so that it rotates the polarisation of light passing through it by 90°.
This also couples one of inputs 8 to one of outputs (9) thereby providing bidirectional switching. Use of combined beam splitters and polarisers (2, 4) provides bidirectionalily at substantially no loss of light additional to that lost on discrimination of the polarisation states.
A bidirectional optical space switch for selectively coupling an input signal to a selected output comprises two arrays of inputs (19 8), two arrays of outputs (5, 9), polarising beam splitters (2, 4), and a matrix of cells (3) each of which is selectively capable of varying the polarisation state of light passing through it in response to an applied control signal. A first optical system (5) couples each of inputs (1) and a corresponding one of outputs (9) with a corresponding column of cells while a second optical system (7) couples each of inputs (8) and a corresponding one of outputs (5) with a corresponding row of cells. One of inputs (1) is switched to one of outputs (5) by activating the appropriate cell so that it rotates the polarisation of light passing through it by 90°.
This also couples one of inputs 8 to one of outputs (9) thereby providing bidirectional switching. Use of combined beam splitters and polarisers (2, 4) provides bidirectionalily at substantially no loss of light additional to that lost on discrimination of the polarisation states.
Description
~Z~ 6 BT CASE NO,A23592 WP NO. 074~P :
BIDIRECTIONAL OPTIC~L SPACE SWITCH
.
The present invention relates to a bidirectional optical space switch which is capable of use in a centralised switching system for an optical network. A
centralised switching system is the s~plest active network which is co~patible with optical and electronic multiplexing, o~fers th~ maximum network size, range, and ~10xibility and is ~lso co~patible with the existing wire-networks.
o A paper to entitled "4 x 4 optical - Gate matrix switch" by A. Himeno and M.Kobayashi (Journal of lightwave Technology Vol LT-3 No.2 April '~5) dlscloses an optical gate matrix switch in which optical signals entering each input port Ii f four input ports are distributed by an optlcal splitter S~ to each o~ 3ate elements Gll to Gi4. When a desired single gate Gi~ is opened a light signal can pass through the gat~ to an output port OJ
vi~ a combiner Cj, which combines the outputs of all gates Gl; to G~, to an optlcal recciver. Thls arrange~ent permits multiconnections between any input port Ij and any plural output ports 0~ to be obtained. Each optical gate Gi~ is formed by a polarisation rotator placed between its own polariser and crosse~ analyser to form an on-o~ optical gate controllable by a driving volta~e applied to the polarisation rotator. A disadvantage o~ this arrangement is that it is uni-dlrectional.
According to the present inv~ntion a bi~directional optical space switch comprises:
'~
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a first and a second array of inputs for emitting optical si~nals to be switched;
a first and a second array of outputs for receiving switched optical signals from the first and second array o~ inputs, respectively;
an active array o~ cells having ~irst and second sides each cell being selectively capable of varying the polarisation state o~ light passing throu~h from one side of the cell to the othe~ in response to an applied control o signal;
a first optical coupling means for optically coupling the first sides of each of a plurality of ~roups of cells with a correspondin~ inputs of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling means for optically coupling the second sides o~ each o~ a plurality of groups of cells with a corresponding input o~ the second arxay o~ inputs and with a corresponding output of the second array of outputs;
the ~irst and second optical coupling means including a respective first and second polarising beam splitter each arranged both to polarise light travelling ~rom each input to the array o~ cells and to direct appropriately polarised llght, only, passin~ through a cell away ~rom the inputs and to the outputs.
The polarising beam splitters may, for example, comprise two right angle prisms having their hypotenuse ~aces cemented together and sandwiching a dielectric multilayer so that light polarised in th~ hypotenuse plane is reflected by the film and turned through 90/o whereas light polarised transverse to the hypotenuse plane passes straight through the splitter. The use of a polarising beam splitter in the bidlrectiona~ switch ~2~8~
according to the present invention ensures that there is substantially no loss of light save for that lost on discrimination by its polarisation state since the polarising beam splltters provide both the polarising means and the beam splitters. If a non-polarisation state ~el~ tlvo be~m ~:;plltt~r wcrc u~cd ln 3erie3 with ~
separate polarisex there would be typically a 50/o loss, at both beam splitters leading to a ~inimum of a 7S/o power loss throu~h the switch. Thc present ].o invention there~ore provides a particularly effective bi-directional optical switch.
Preferably the active array of cells has the ~orm of a matrix array with the optical coupling means being arranyed to connect each input to its respective column, or row, o~ the ~atrix array of cells and to couple each row, or column, to its respective output. Preferably the input and output arrays are ~ormed by linear arrays arranged perpendicularly to one another and the optical coupling means are ~ormed by lenses or holograms arranged to couple the light ~ro~ a particular input to a particular column or row o~ the array and, correspondingly arranged to couple light from a particular row or column o~ the array to its respectlve output.
The active array o~ cells is pre~erably ~ormed by an array o~ liquid crystal devices including devices of the twisted-ne~atic type. However, other types of liquid crystal devices such as scattering cells may be cascaded with the devices o~ the twisted nematic type to improve the overall contrast ratio.
3~ The polarising beam splitters are preferably arranged to direct to an output light in a polarisation state opposite to tha~ o~ light impingin~ on the active cell ~from an output so tha~, it is only when the light p~ss~ng through the selected cell has its plane of polarisatlon ~Zg8~.16 rotated through 90/o that it can pass through the polarising beam splitter downstream from the active cell array and be directed to an output. However, it is also ~ossible to have thQ ~ ri .s~t.in~ hP~m ~1 i tter arran3ed to direct to an output ligh~ in a polarisation state the same as the light impinging on the active cell array from an input and arrange for all o~ the active cells except for the selected cell to rotate the plane or polarisation of light passing through them by 90~o.
lo Whilst typically an optical switch according to the present invention is arrang2d so that each and every input can be selectively coupled to each and every output it is also possible to arrange ~or the distribution and collection means to provide particular multiple connection and barrin~ schemes. Thus, where it ls required that a particular input signal is sent to more than one output destination, it is possible to arrange for the optical means to couple corxesponding cells in each group to more than one output or, where it is required for a particular input not to bc able to be connected to a particular output, it is posslble to arrange for the optical means not to couple the corresponding cells in some of the groups to a particular output.
The arrays of inputs may be provided by the ends of a number of optical fibre waveguides ox, alternatively, by a number of optical devices the outputs of which are modulated by the input signals. Thus, each array of inputs may all be taken from a single optical source which is split, and each split component is modulated in accordance with an input signal or, alternatively, the devices may be formed by a number of independent optical sources each of which is modulated in accordance with an ~input signal. The arrays of outputs may be formed by the ends of arrays of optical waveguides leading away from the ~2~ 6 .
optical space switch or they may be formed by an arrays o~
photodetectors which detect the light received. Such photodetectors may form part o~ an optical regenerator which, in turn, generates an output in the ~orm of an optical signal.
In this way the optical space switch may be used as the switching element of an electrical communication system in which the electrical input signals are converted to optical signals at the input to the swltch and the lo reconverted to electrical signals at the output. This can thus avoid the necessity of electrical conduction paths physically connecting each input to each output with switching means connected in series in each path which is required in a conventional electrical cross-bar switch and improves the switch bandwidth. Alternatively, the optical space switch may be used as a switching element for optical signals.
The invention will now be described, by way of example only, with reference to the accompanying drawings, in which-Figure l is a diagrammatic perspective view o~ a first embodiment Or the present in~ention; and Figure 2 is a diagrammatic perspective view of a second embodiment o~ the present invention.
Referring to Figure 1, tllere is shown a ~irst input array o~ inputs l formed by ~ ribbon of single mode or multimode optical fibres located in a horizontal plane emits light which is polarised by a polarising beam splitter 2 and impinges upon a liquid crystal matrix arxay 3. Light passing through the liquid crystal matrix array 3 passes through an analysing polarising beam splitter 4 and thence to a ribbon of single, or ~ultimode output fibres 5, constituting the ~irst array o~ outputs, Located in a senerally vertical plane if of the correc~
polarisation. An optical system 6 comprising a combination o~ cylindrical and plano-convex lenses 20, 21 is located between the beam splitter 2 and the liquid crystal device 3 tb dlrect the light from each individual fibre ln the xibbon l to its respective column of tne liquid crystal device 3. lhe o:ptical system 6 and the polarising beam splitter 2 together constitute the first optical means. A further optical syste~ 7, also comprising a o combination of cylindrical and plano-convex lenses 22,~4, is located between the device 3 and the beam splitter 4.
These concentrate light ~rom a row of the matrix 3 to its respective output ~ibre in the ribbon 5 which together with the second polarising beam splitter 4 constitute the second optical means. The apparatus also includes a second array o~ input fibres 8 located in the vertioal plane and at right angles to the output ribbon 5, and a second array of output fibres 9 located in a vertical plane and generally perpendicular to the input ribbon l.
The liquid crystal device 3 is typically a twisted-nematic liquid crystal device divided into a N x N matrix, the ribbons l, 9,5 and 8 of input and output ~ibres each containing N fibres.
Thus considering light passing in a firs~ direction ~5 through the switch from the lnput ribbon l to the output ribbon 5, the light is first polarised in the polariser beam splitter 2 and any rejected light reflected from tne interface in the beam splitter 2 upwards (in the orientation as shown in Flgure 1). The optical system 6 spreads the non-rejected light ~rom that particular input ~lbre over a colu~n o~ cells of the liquid crystal device 3 which are in a position corresponding to that o~ the Darti~ul~r ~hr~ in thP rihhnn ~ r~l cign~l ic applied to one or more of the cells in the column to cause -` ~2~ 6 a change in polarisation state of 90 degrees so that light passing through these cells has its direction o~
polarisation rotated through 90 degrees whereas the light passing through all of the other cells in that coiumn is unaffected. .~he optical system 7 directs light from the different rows of the liquid crystals de~/ice 3 towards the ends of the respective output fibres in the ribbon 5.
However, light transmitted through cells ~hich have not changed their polarisation state are deflected by tne o interface of the beam splitter 4 and only light from those cells which have been rotated through 90 degrees are transmitted through the beam splitter to impinge upon the end fases of the fibres in the ribbon 5.
Light passing in the opposite direction through the switch is introduced via the optical ~ibres in the ribbon 8. Light of a particular polarisation state is reflected ~rom the interface of the beam splitter 4 and focussed by the optical system 7 onto particular rows of the liquid crystal device ~ corresponding to the lscation of the optical fibres in the ribbon 8. Those cells in that particular row which have a control signal applied to them to cause a 90 de~ree rotation of the plane of polarisation ~or light coming from an input of the first array 1 also will change the polarisation of light passing through it 2s from input of the second array of inputs 8. The optical system 6 collects light from all o~ the cells and directs it to the polarising beam splitter 2. Light which has not had its direction of polarisation changed passes straight through the bea~ splitter 2 ~hilst light which has has its polarisation state changed by 90 degrees is reflected by the inner face of the beam splitter 2 towards the ribbon o~ output optical fibres 9. The optical system 6 focusses the light ~rom a particular column of the liquid crystal .~ . . .
~2~8116 device ~ onto its .espective optical fibres in the ribbon 9. Thus, once a particular channel has been established in the opticaL switch by appl~Jing a control signal to one particular cell of the liquid crystal device 3 two corresponding,switch connection are made simultaneously, one in each direction through the optical switch.
Where N = 100 a contrast ratio between light which passes through a selected cell of the liquid crystal device 3 and that which does not must be at least 104 or o 40 dB. With good quality polarising beam splitters 2 and 4 and a twisted-nematic liquid crystal array this is feas.ble.
Referring now to Fig 2, an optical switch has arrays of inputs 1 and 8, arrays of outputs 5 and 9 and a liquid S crystal matrix array of cells 3 as provlded in the optical switch of Figure 1. This embodiment differs from that shown in Figure 1 in that polarising beam splitters 10 and 11 are positioned adjacent the matrix array 3. Optical systems 12, 13, 14 and 15 each comprising a combination of ~0 cylindrical and plano-convex lenses (illustrated schematically as optical boxes for clarity) direct light to or from the array 3, and to or from the inputs 1 an,d 8 and outputs 5 and 9 ~respectively via the polariser beam splitters. Optical systems 12, 15 and polarising beam splitter 10, and optical systems 13, 14 and polarising beam spl-ittèr ïï, constitute first and second optical meàns, respectively.
The switch of Figure 2 is ~unctionally equivalent to that of Figure 1 but with polarisation of light from an input by a polarising beam splitter occurring after an optical system has directed the light to be spread over the appropriate row or column of cells, and with the light ~xom the cells being analysed by a polarising beam ... ...
_ 9 ~
splitter be~ore passing to an optical system to be applied to an output.
The arrangement of Figure 2 having the imaging optical components o~ each direction separated allows the output S imaging optics of each direction to be optimised without affecting the input optics o~ the other direction. Input and output optics can therefore be independently optimised. On the other hand, this configuration rPquires a larger number of imaging devices than the con~iguration lo of Figure 1.
Imaging optics utilising lens systems other than the specifically described with reference to Figures 1 or 2, or other methods such as holographic imagillg, may be employed which distribute the input signals amongst the cells and convey the resulting signals from the cells to the outputs, however combinations of cylindrical and plano-convex lenses are simple and efficient and have ~he advantage of being freely avallable.
It will be appreciated that an optical system according to the present invention can also be used \ for uni-directional transmission without modification.
The optical means may include optical waveguides which couple the light emltted from the inputs to the cells and thence from th~ cells to the outputs. In this case the distribution means may be formed by a number of bundles of optical ~ibres each bundle being coupled to an input and the fibres o~ each bundle being coupled9 respectively, to individual cells in the group associated with that input.
In this case the geometric con~iguration o~ the active array o~ cells may have any convenient ~orm. For example, it may be formed by a linear or even a circular array and may be formed by a single, multi-element component or by a number of discrete components.
~Z9 !3~
-- 1~
Where optical waveguides replace the lens systems 6 and 7 of the embodiment of Figure l they ha~e to 3e polarisation maintaining fibres. ~here optical wave~uides replace the lens systems 12, 13, 14 and 15 of Figure 2 the ; ends of the waveguides will ideally be lensed to collimate light existing the waveguides to direct it to a chosen cell of the array 3 through the depth o~ the beam splittsr.
While the invention has been described in connection with what is presently considered to be the most lo practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
B
BIDIRECTIONAL OPTIC~L SPACE SWITCH
.
The present invention relates to a bidirectional optical space switch which is capable of use in a centralised switching system for an optical network. A
centralised switching system is the s~plest active network which is co~patible with optical and electronic multiplexing, o~fers th~ maximum network size, range, and ~10xibility and is ~lso co~patible with the existing wire-networks.
o A paper to entitled "4 x 4 optical - Gate matrix switch" by A. Himeno and M.Kobayashi (Journal of lightwave Technology Vol LT-3 No.2 April '~5) dlscloses an optical gate matrix switch in which optical signals entering each input port Ii f four input ports are distributed by an optlcal splitter S~ to each o~ 3ate elements Gll to Gi4. When a desired single gate Gi~ is opened a light signal can pass through the gat~ to an output port OJ
vi~ a combiner Cj, which combines the outputs of all gates Gl; to G~, to an optlcal recciver. Thls arrange~ent permits multiconnections between any input port Ij and any plural output ports 0~ to be obtained. Each optical gate Gi~ is formed by a polarisation rotator placed between its own polariser and crosse~ analyser to form an on-o~ optical gate controllable by a driving volta~e applied to the polarisation rotator. A disadvantage o~ this arrangement is that it is uni-dlrectional.
According to the present inv~ntion a bi~directional optical space switch comprises:
'~
\
~zr~
a first and a second array of inputs for emitting optical si~nals to be switched;
a first and a second array of outputs for receiving switched optical signals from the first and second array o~ inputs, respectively;
an active array o~ cells having ~irst and second sides each cell being selectively capable of varying the polarisation state o~ light passing throu~h from one side of the cell to the othe~ in response to an applied control o signal;
a first optical coupling means for optically coupling the first sides of each of a plurality of ~roups of cells with a correspondin~ inputs of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling means for optically coupling the second sides o~ each o~ a plurality of groups of cells with a corresponding input o~ the second arxay o~ inputs and with a corresponding output of the second array of outputs;
the ~irst and second optical coupling means including a respective first and second polarising beam splitter each arranged both to polarise light travelling ~rom each input to the array o~ cells and to direct appropriately polarised llght, only, passin~ through a cell away ~rom the inputs and to the outputs.
The polarising beam splitters may, for example, comprise two right angle prisms having their hypotenuse ~aces cemented together and sandwiching a dielectric multilayer so that light polarised in th~ hypotenuse plane is reflected by the film and turned through 90/o whereas light polarised transverse to the hypotenuse plane passes straight through the splitter. The use of a polarising beam splitter in the bidlrectiona~ switch ~2~8~
according to the present invention ensures that there is substantially no loss of light save for that lost on discrimination by its polarisation state since the polarising beam splltters provide both the polarising means and the beam splitters. If a non-polarisation state ~el~ tlvo be~m ~:;plltt~r wcrc u~cd ln 3erie3 with ~
separate polarisex there would be typically a 50/o loss, at both beam splitters leading to a ~inimum of a 7S/o power loss throu~h the switch. Thc present ].o invention there~ore provides a particularly effective bi-directional optical switch.
Preferably the active array of cells has the ~orm of a matrix array with the optical coupling means being arranyed to connect each input to its respective column, or row, o~ the ~atrix array of cells and to couple each row, or column, to its respective output. Preferably the input and output arrays are ~ormed by linear arrays arranged perpendicularly to one another and the optical coupling means are ~ormed by lenses or holograms arranged to couple the light ~ro~ a particular input to a particular column or row o~ the array and, correspondingly arranged to couple light from a particular row or column o~ the array to its respectlve output.
The active array o~ cells is pre~erably ~ormed by an array o~ liquid crystal devices including devices of the twisted-ne~atic type. However, other types of liquid crystal devices such as scattering cells may be cascaded with the devices o~ the twisted nematic type to improve the overall contrast ratio.
3~ The polarising beam splitters are preferably arranged to direct to an output light in a polarisation state opposite to tha~ o~ light impingin~ on the active cell ~from an output so tha~, it is only when the light p~ss~ng through the selected cell has its plane of polarisatlon ~Zg8~.16 rotated through 90/o that it can pass through the polarising beam splitter downstream from the active cell array and be directed to an output. However, it is also ~ossible to have thQ ~ ri .s~t.in~ hP~m ~1 i tter arran3ed to direct to an output ligh~ in a polarisation state the same as the light impinging on the active cell array from an input and arrange for all o~ the active cells except for the selected cell to rotate the plane or polarisation of light passing through them by 90~o.
lo Whilst typically an optical switch according to the present invention is arrang2d so that each and every input can be selectively coupled to each and every output it is also possible to arrange ~or the distribution and collection means to provide particular multiple connection and barrin~ schemes. Thus, where it ls required that a particular input signal is sent to more than one output destination, it is possible to arrange for the optical means to couple corxesponding cells in each group to more than one output or, where it is required for a particular input not to bc able to be connected to a particular output, it is posslble to arrange for the optical means not to couple the corresponding cells in some of the groups to a particular output.
The arrays of inputs may be provided by the ends of a number of optical fibre waveguides ox, alternatively, by a number of optical devices the outputs of which are modulated by the input signals. Thus, each array of inputs may all be taken from a single optical source which is split, and each split component is modulated in accordance with an input signal or, alternatively, the devices may be formed by a number of independent optical sources each of which is modulated in accordance with an ~input signal. The arrays of outputs may be formed by the ends of arrays of optical waveguides leading away from the ~2~ 6 .
optical space switch or they may be formed by an arrays o~
photodetectors which detect the light received. Such photodetectors may form part o~ an optical regenerator which, in turn, generates an output in the ~orm of an optical signal.
In this way the optical space switch may be used as the switching element of an electrical communication system in which the electrical input signals are converted to optical signals at the input to the swltch and the lo reconverted to electrical signals at the output. This can thus avoid the necessity of electrical conduction paths physically connecting each input to each output with switching means connected in series in each path which is required in a conventional electrical cross-bar switch and improves the switch bandwidth. Alternatively, the optical space switch may be used as a switching element for optical signals.
The invention will now be described, by way of example only, with reference to the accompanying drawings, in which-Figure l is a diagrammatic perspective view o~ a first embodiment Or the present in~ention; and Figure 2 is a diagrammatic perspective view of a second embodiment o~ the present invention.
Referring to Figure 1, tllere is shown a ~irst input array o~ inputs l formed by ~ ribbon of single mode or multimode optical fibres located in a horizontal plane emits light which is polarised by a polarising beam splitter 2 and impinges upon a liquid crystal matrix arxay 3. Light passing through the liquid crystal matrix array 3 passes through an analysing polarising beam splitter 4 and thence to a ribbon of single, or ~ultimode output fibres 5, constituting the ~irst array o~ outputs, Located in a senerally vertical plane if of the correc~
polarisation. An optical system 6 comprising a combination o~ cylindrical and plano-convex lenses 20, 21 is located between the beam splitter 2 and the liquid crystal device 3 tb dlrect the light from each individual fibre ln the xibbon l to its respective column of tne liquid crystal device 3. lhe o:ptical system 6 and the polarising beam splitter 2 together constitute the first optical means. A further optical syste~ 7, also comprising a o combination of cylindrical and plano-convex lenses 22,~4, is located between the device 3 and the beam splitter 4.
These concentrate light ~rom a row of the matrix 3 to its respective output ~ibre in the ribbon 5 which together with the second polarising beam splitter 4 constitute the second optical means. The apparatus also includes a second array o~ input fibres 8 located in the vertioal plane and at right angles to the output ribbon 5, and a second array of output fibres 9 located in a vertical plane and generally perpendicular to the input ribbon l.
The liquid crystal device 3 is typically a twisted-nematic liquid crystal device divided into a N x N matrix, the ribbons l, 9,5 and 8 of input and output ~ibres each containing N fibres.
Thus considering light passing in a firs~ direction ~5 through the switch from the lnput ribbon l to the output ribbon 5, the light is first polarised in the polariser beam splitter 2 and any rejected light reflected from tne interface in the beam splitter 2 upwards (in the orientation as shown in Flgure 1). The optical system 6 spreads the non-rejected light ~rom that particular input ~lbre over a colu~n o~ cells of the liquid crystal device 3 which are in a position corresponding to that o~ the Darti~ul~r ~hr~ in thP rihhnn ~ r~l cign~l ic applied to one or more of the cells in the column to cause -` ~2~ 6 a change in polarisation state of 90 degrees so that light passing through these cells has its direction o~
polarisation rotated through 90 degrees whereas the light passing through all of the other cells in that coiumn is unaffected. .~he optical system 7 directs light from the different rows of the liquid crystals de~/ice 3 towards the ends of the respective output fibres in the ribbon 5.
However, light transmitted through cells ~hich have not changed their polarisation state are deflected by tne o interface of the beam splitter 4 and only light from those cells which have been rotated through 90 degrees are transmitted through the beam splitter to impinge upon the end fases of the fibres in the ribbon 5.
Light passing in the opposite direction through the switch is introduced via the optical ~ibres in the ribbon 8. Light of a particular polarisation state is reflected ~rom the interface of the beam splitter 4 and focussed by the optical system 7 onto particular rows of the liquid crystal device ~ corresponding to the lscation of the optical fibres in the ribbon 8. Those cells in that particular row which have a control signal applied to them to cause a 90 de~ree rotation of the plane of polarisation ~or light coming from an input of the first array 1 also will change the polarisation of light passing through it 2s from input of the second array of inputs 8. The optical system 6 collects light from all o~ the cells and directs it to the polarising beam splitter 2. Light which has not had its direction of polarisation changed passes straight through the bea~ splitter 2 ~hilst light which has has its polarisation state changed by 90 degrees is reflected by the inner face of the beam splitter 2 towards the ribbon o~ output optical fibres 9. The optical system 6 focusses the light ~rom a particular column of the liquid crystal .~ . . .
~2~8116 device ~ onto its .espective optical fibres in the ribbon 9. Thus, once a particular channel has been established in the opticaL switch by appl~Jing a control signal to one particular cell of the liquid crystal device 3 two corresponding,switch connection are made simultaneously, one in each direction through the optical switch.
Where N = 100 a contrast ratio between light which passes through a selected cell of the liquid crystal device 3 and that which does not must be at least 104 or o 40 dB. With good quality polarising beam splitters 2 and 4 and a twisted-nematic liquid crystal array this is feas.ble.
Referring now to Fig 2, an optical switch has arrays of inputs 1 and 8, arrays of outputs 5 and 9 and a liquid S crystal matrix array of cells 3 as provlded in the optical switch of Figure 1. This embodiment differs from that shown in Figure 1 in that polarising beam splitters 10 and 11 are positioned adjacent the matrix array 3. Optical systems 12, 13, 14 and 15 each comprising a combination of ~0 cylindrical and plano-convex lenses (illustrated schematically as optical boxes for clarity) direct light to or from the array 3, and to or from the inputs 1 an,d 8 and outputs 5 and 9 ~respectively via the polariser beam splitters. Optical systems 12, 15 and polarising beam splitter 10, and optical systems 13, 14 and polarising beam spl-ittèr ïï, constitute first and second optical meàns, respectively.
The switch of Figure 2 is ~unctionally equivalent to that of Figure 1 but with polarisation of light from an input by a polarising beam splitter occurring after an optical system has directed the light to be spread over the appropriate row or column of cells, and with the light ~xom the cells being analysed by a polarising beam ... ...
_ 9 ~
splitter be~ore passing to an optical system to be applied to an output.
The arrangement of Figure 2 having the imaging optical components o~ each direction separated allows the output S imaging optics of each direction to be optimised without affecting the input optics o~ the other direction. Input and output optics can therefore be independently optimised. On the other hand, this configuration rPquires a larger number of imaging devices than the con~iguration lo of Figure 1.
Imaging optics utilising lens systems other than the specifically described with reference to Figures 1 or 2, or other methods such as holographic imagillg, may be employed which distribute the input signals amongst the cells and convey the resulting signals from the cells to the outputs, however combinations of cylindrical and plano-convex lenses are simple and efficient and have ~he advantage of being freely avallable.
It will be appreciated that an optical system according to the present invention can also be used \ for uni-directional transmission without modification.
The optical means may include optical waveguides which couple the light emltted from the inputs to the cells and thence from th~ cells to the outputs. In this case the distribution means may be formed by a number of bundles of optical ~ibres each bundle being coupled to an input and the fibres o~ each bundle being coupled9 respectively, to individual cells in the group associated with that input.
In this case the geometric con~iguration o~ the active array o~ cells may have any convenient ~orm. For example, it may be formed by a linear or even a circular array and may be formed by a single, multi-element component or by a number of discrete components.
~Z9 !3~
-- 1~
Where optical waveguides replace the lens systems 6 and 7 of the embodiment of Figure l they ha~e to 3e polarisation maintaining fibres. ~here optical wave~uides replace the lens systems 12, 13, 14 and 15 of Figure 2 the ; ends of the waveguides will ideally be lensed to collimate light existing the waveguides to direct it to a chosen cell of the array 3 through the depth o~ the beam splittsr.
While the invention has been described in connection with what is presently considered to be the most lo practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
B
Claims (19)
1. A bi-directional optical space switch comprising:
a first array of inputs and a second array of inputs for emitting optical signals to be switched;
a first array of inputs and a second array of outputs for receiving switched optical signals from the first and second array of inputs, respectively;
an active array of cells having first and second sides each cell being selectively capable of varying the polarisation state of light passing through from one side of the cell to the other in response to an applied control signal;
a first optical coupling means for optically coupling the first sides of each of a plurality of groups of the active array of cells with a corresponding input of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling means for optically coupling the second sides of each of a plurality of groups of the active array of cells with a corresponding input of the second array of inputs and with a corresponding output of the first array of outputs;
the first and second optical coupling means including a respective first and second polarising beam splitter each arranged both to polarise light travelling from an input to the array of cells and to direct only appropriately polarised light passing through a cell away from the inputs and to the outputs.
a first array of inputs and a second array of inputs for emitting optical signals to be switched;
a first array of inputs and a second array of outputs for receiving switched optical signals from the first and second array of inputs, respectively;
an active array of cells having first and second sides each cell being selectively capable of varying the polarisation state of light passing through from one side of the cell to the other in response to an applied control signal;
a first optical coupling means for optically coupling the first sides of each of a plurality of groups of the active array of cells with a corresponding input of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling means for optically coupling the second sides of each of a plurality of groups of the active array of cells with a corresponding input of the second array of inputs and with a corresponding output of the first array of outputs;
the first and second optical coupling means including a respective first and second polarising beam splitter each arranged both to polarise light travelling from an input to the array of cells and to direct only appropriately polarised light passing through a cell away from the inputs and to the outputs.
2. An optical space switch as claimed in claim 1 in which each polarising beam splitter is located adjacent the array of cells.
3. An optical space switch as claimed in claim 1 in which each polarising beam splitter is located adjacent an array of inputs and an array of outputs.
4. An optical space switch as claimed in any one of claims 1, 2 or 3 in which the arrays of inputs and arrays of outputs comprise optical waveguides.
5. A bi-directional optical space switch comprising:
a first array of inputs and a second array of inputs for emitting optical signals to be switched;
a first array of outputs and a second array of outputs for receiving switched optical signals from the first and second array of inputs, respectively;
an active array of cells having first and second sides each cell being selectively capable of varying the polarisation state of light passing through from one side of the cell to the other in response to an applied control signal;
a first optical coupling means for optically coupling the first sides of each of a plurality of groups of the active array of cells with a corresponding input of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling means for optically coupling the second sides of each of a plurality of groups of the active array of cells with a corresponding input of the second array of inputs and with a corresponding output of the first array of outputs;
the first and second optical coupling means including a respective first and second polarising beam splitter each arranged both to polarise light travelling from an input to the array of cells and to direct only appropriately polarised light passing through a cell away from the inputs and to the outputs;
wherein the active array of cells has the form of a matrix array; and the first and second coupling means are arranged to couple each input to a respective row or column of cells, and to couple each row and column of cells to a respective output.
a first array of inputs and a second array of inputs for emitting optical signals to be switched;
a first array of outputs and a second array of outputs for receiving switched optical signals from the first and second array of inputs, respectively;
an active array of cells having first and second sides each cell being selectively capable of varying the polarisation state of light passing through from one side of the cell to the other in response to an applied control signal;
a first optical coupling means for optically coupling the first sides of each of a plurality of groups of the active array of cells with a corresponding input of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling means for optically coupling the second sides of each of a plurality of groups of the active array of cells with a corresponding input of the second array of inputs and with a corresponding output of the first array of outputs;
the first and second optical coupling means including a respective first and second polarising beam splitter each arranged both to polarise light travelling from an input to the array of cells and to direct only appropriately polarised light passing through a cell away from the inputs and to the outputs;
wherein the active array of cells has the form of a matrix array; and the first and second coupling means are arranged to couple each input to a respective row or column of cells, and to couple each row and column of cells to a respective output.
6. A bi-directional optical space switch comprising:
a first array of inputs and a second array of inputs for emitting optical signals to be switched;
a first array of outputs and a second array of outputs for receiving switched optical signals from the first and second array of inputs, respectively;
an active array of cells having first and second sides each cell being selectively capable of varying the polarisation state of light passing through from one side of the cell to the other in response to an applied control signal;
a first optical coupling means for optically coupling the first sides of each of a plurality of groups of the active array of cells with a corresponding input of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling means for optically coupling the second sides of each of a plurality of groups of the active array of cells with a corresponding input of the second array of inputs and with a corresponding output of the first array of outputs;
the first and second optical coupling means including a respective first and second polarising beam splitter each arranged both to polarise light travelling from an input to the array of cells and to direct only appropriately polarised light passing through a cell away from the inputs and to the outputs;
wherein the active array of cells has the form of a matrix array;
the first and second coupling means are arranged to couple each input to a respective row or column of cells, and to couple each row and column of cells to a respective output;
and the optical coupling means are formed by lenses.
a first array of inputs and a second array of inputs for emitting optical signals to be switched;
a first array of outputs and a second array of outputs for receiving switched optical signals from the first and second array of inputs, respectively;
an active array of cells having first and second sides each cell being selectively capable of varying the polarisation state of light passing through from one side of the cell to the other in response to an applied control signal;
a first optical coupling means for optically coupling the first sides of each of a plurality of groups of the active array of cells with a corresponding input of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling means for optically coupling the second sides of each of a plurality of groups of the active array of cells with a corresponding input of the second array of inputs and with a corresponding output of the first array of outputs;
the first and second optical coupling means including a respective first and second polarising beam splitter each arranged both to polarise light travelling from an input to the array of cells and to direct only appropriately polarised light passing through a cell away from the inputs and to the outputs;
wherein the active array of cells has the form of a matrix array;
the first and second coupling means are arranged to couple each input to a respective row or column of cells, and to couple each row and column of cells to a respective output;
and the optical coupling means are formed by lenses.
7. A bi-directional optical space switch comprising:
a first array of inputs and a second array of inputs for emitting optical signals to be switched;
a first array of outputs and a second array of outputs for receiving switched optical signals from the first and second array of inputs, respectively;
an active array of cells having first and second sides each cell being selectively capable of varying the polarisation state of light passing through from one side of the cell to the other in response to an applied control signal;
a first optical coupling means for optically coupling the first sides of each of a plurality of groups of the active array of cells with a corresponding input of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling means for optically coupling the second sides of each of a plurality of groups of the active array of cells with a corresponding input of the second array of inputs and with a corresponding output of the first array of outputs;
the first and second optical coupling means including a respective first and second polarising beam splitter each arranged both to polarise light travelling from an input to the array of cells and to direct only appropriately polarised light passing through a cell away from the inputs and to the outputs;
wherein the active array of cells has the form of a matrix array;
the first and second coupling means are arranged to couple each input to a respective row or column of cells, and to couple each row and column of cells to a respective output;
the optical coupling means are formed by lenses; and wherein the optical coupling means includes a spherical lens and a plano-convex lens.
a first array of inputs and a second array of inputs for emitting optical signals to be switched;
a first array of outputs and a second array of outputs for receiving switched optical signals from the first and second array of inputs, respectively;
an active array of cells having first and second sides each cell being selectively capable of varying the polarisation state of light passing through from one side of the cell to the other in response to an applied control signal;
a first optical coupling means for optically coupling the first sides of each of a plurality of groups of the active array of cells with a corresponding input of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling means for optically coupling the second sides of each of a plurality of groups of the active array of cells with a corresponding input of the second array of inputs and with a corresponding output of the first array of outputs;
the first and second optical coupling means including a respective first and second polarising beam splitter each arranged both to polarise light travelling from an input to the array of cells and to direct only appropriately polarised light passing through a cell away from the inputs and to the outputs;
wherein the active array of cells has the form of a matrix array;
the first and second coupling means are arranged to couple each input to a respective row or column of cells, and to couple each row and column of cells to a respective output;
the optical coupling means are formed by lenses; and wherein the optical coupling means includes a spherical lens and a plano-convex lens.
8. An optical space switch as claimed in any one of claims 1, 2 or 3 in which the active array of cells comprises an array of liquid crystal devices of the twisted-nematic type.
9. An optical space switch as claimed in claim 8, in which the twisted-nematic liquid crystal cells are each cascaded with a liquid crystal scattering cell.
10. An optical space switch as claimed in any one of claims 1, 2 or 3 in which the inputs comprise the ends of optical fibre waveguides.
11. An optical space switch as claimed in any one of claims 1,2 or 3 in which the arrays of inputs are formed by a plurality of optical devices the outputs of which are modulated to provide the optical signals to be switched.
12. An optical space switch as claimed in any one of claims 1, 2 or 3 in which the outputs comprise the ends of optical waveguides.
13. An optical space switch as claimed in any one of claims 1 in which the outputs comprise photodetectors which detect switched optical signals.
14. Apparatus for the bi-directional switching of optical signals comprising:
an array of cells, each of which is selectively capable of rotating the polarisation state of light passing through the cell in response to an applied control signal;
first and second arrays of inputs, located on first and second sides of the array of cells, for producing optical signals to be switched;
first and second arrays of outputs for receiving switched signals from the second and first arrays of inputs, respectively;
a first optical coupling system for optically coupling each of a plurality of groups of the array of cells with a corresponding input of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling system for optically coupling each of a plurality of groups of the array of cells with a corresponding input of the second array of inputs and with a corresponding output of the first array of outputs;
whereby ones of the first array of inputs are switched to ones of the second array of outputs and ones of the second array of inputs are switched to ones of the first array of outputs only if the polarisation of the light passing through the cells has been appropriately rotated in response to the application of control signals.
an array of cells, each of which is selectively capable of rotating the polarisation state of light passing through the cell in response to an applied control signal;
first and second arrays of inputs, located on first and second sides of the array of cells, for producing optical signals to be switched;
first and second arrays of outputs for receiving switched signals from the second and first arrays of inputs, respectively;
a first optical coupling system for optically coupling each of a plurality of groups of the array of cells with a corresponding input of the first array of inputs and with a corresponding output of the second array of outputs;
a second optical coupling system for optically coupling each of a plurality of groups of the array of cells with a corresponding input of the second array of inputs and with a corresponding output of the first array of outputs;
whereby ones of the first array of inputs are switched to ones of the second array of outputs and ones of the second array of inputs are switched to ones of the first array of outputs only if the polarisation of the light passing through the cells has been appropriately rotated in response to the application of control signals.
15. The apparatus of claim 14, in which the array of cells is a matrix array; and the first and second optical coupling systems are arranged to couple each input to a respective row or column of cells, and to couple each row or column to a respective output.
16. The apparatus of claim 15, in which the first and second optical coupling systems each include lenses and a polarising beam splitter.
17. The apparatus of claim 16, in which the lenses include a spherical lens and a plano-convex lens.
18. A method for bi-directionally switching optical signals between first and second arrays of inputs, and corresponding second and first arrays of outputs comprising:
optically coupling each of the inputs of the first array of inputs and a corresponding one of the second array of outputs with a corresponding column or row of a matrix of cells, said cells being selectively capable of rotating the polarisation state of light passing through the cells in response to an applied control signal;
optically coupling each of the inputs of the second array of inputs and a corresponding one of the first array of outputs with a corresponding column or row of said matrix of cells;
activating at least one cell to switch only appropriately rotated light from at least one of the inputs of the first input array to at least a corresponding one of the outputs of the second output array and switch only appropriately rotated light from at least one input of the second input array to at least a corresponding one of the outputs of the first output array.
optically coupling each of the inputs of the first array of inputs and a corresponding one of the second array of outputs with a corresponding column or row of a matrix of cells, said cells being selectively capable of rotating the polarisation state of light passing through the cells in response to an applied control signal;
optically coupling each of the inputs of the second array of inputs and a corresponding one of the first array of outputs with a corresponding column or row of said matrix of cells;
activating at least one cell to switch only appropriately rotated light from at least one of the inputs of the first input array to at least a corresponding one of the outputs of the second output array and switch only appropriately rotated light from at least one input of the second input array to at least a corresponding one of the outputs of the first output array.
19. A bi-directional optical space switch comprising:
an array of cells individually capable of selectively rotating the polarization of optical signals passing therethrough;
an array of optical inputs and an array of optical outputs disposed on one side of said array of cells having individual inputs and outputs optically coupled to respective sub-groups of said cells and an array of optical outputs and an array of optical inputs disposed on an opposite side of said array of cells having individual inputs and outputs optically coupled to respective sub-groups of said cells.
an array of cells individually capable of selectively rotating the polarization of optical signals passing therethrough;
an array of optical inputs and an array of optical outputs disposed on one side of said array of cells having individual inputs and outputs optically coupled to respective sub-groups of said cells and an array of optical outputs and an array of optical inputs disposed on an opposite side of said array of cells having individual inputs and outputs optically coupled to respective sub-groups of said cells.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8701996 | 1987-01-29 | ||
| GB878701996A GB8701996D0 (en) | 1987-01-29 | 1987-01-29 | Optical space switch |
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|---|---|
| CA1298116C true CA1298116C (en) | 1992-03-31 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000557564A Expired - Fee Related CA1298116C (en) | 1987-01-29 | 1988-01-28 | Bidirectional optical space switch |
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| US (1) | US4923269A (en) |
| EP (1) | EP0277779A1 (en) |
| JP (1) | JPH01502710A (en) |
| AU (1) | AU597149B2 (en) |
| CA (1) | CA1298116C (en) |
| GB (1) | GB8701996D0 (en) |
| WO (1) | WO1988005986A1 (en) |
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| DE69024988T2 (en) * | 1989-03-09 | 1996-06-13 | Canon Kk | Optical switching arrangement for bidirectional signal transmission between several terminal devices |
| DE69013130T2 (en) * | 1989-12-28 | 1995-03-09 | Fujitsu Ltd | Optical spatial switch and network with such optical spatial switches. |
| US5177348A (en) * | 1991-08-26 | 1993-01-05 | Herzel Laor | Apparatus and method for aligning optical fibers with an array of radiation emitting devices |
| JP3273583B2 (en) * | 1993-07-28 | 2002-04-08 | 日本電信電話株式会社 | Liquid crystal microprism array and spatial light beam connector and optical switch using the same |
| GB2296098B (en) * | 1994-12-15 | 1998-02-11 | British Aerospace | Optical cross bar switch assembly |
| US5524153A (en) * | 1995-02-10 | 1996-06-04 | Astarte Fiber Networks, Inc. | Optical fiber switching system and method using same |
| US5942157A (en) * | 1996-07-12 | 1999-08-24 | Science Applications International Corporation | Switchable volume hologram materials and devices |
| US6867888B2 (en) * | 1996-07-12 | 2005-03-15 | Science Applications International Corporation | Switchable polymer-dispersed liquid crystal optical elements |
| US6821457B1 (en) * | 1998-07-29 | 2004-11-23 | Science Applications International Corporation | Electrically switchable polymer-dispersed liquid crystal materials including switchable optical couplers and reconfigurable optical interconnects |
| US7312906B2 (en) * | 1996-07-12 | 2007-12-25 | Science Applications International Corporation | Switchable polymer-dispersed liquid crystal optical elements |
| US7077984B1 (en) | 1996-07-12 | 2006-07-18 | Science Applications International Corporation | Electrically switchable polymer-dispersed liquid crystal materials |
| US6154591A (en) * | 1998-04-20 | 2000-11-28 | British Telecommunications Public Limited Company | Tunable optical device |
| US6169594B1 (en) | 1998-08-24 | 2001-01-02 | Physical Optics Corporation | Beam deflector and scanner |
| US6449098B1 (en) | 2000-05-16 | 2002-09-10 | Calient Networks, Inc. | High uniformity lens arrays having lens correction and methods for fabricating the same |
| US6730442B1 (en) * | 2000-05-24 | 2004-05-04 | Science Applications International Corporation | System and method for replicating volume holograms |
| US6483961B1 (en) | 2000-06-02 | 2002-11-19 | Calient Networks, Inc. | Dual refraction index collimator for an optical switch |
| US6810176B2 (en) | 2000-08-07 | 2004-10-26 | Rosemount Inc. | Integrated transparent substrate and diffractive optical element |
| US7003187B2 (en) | 2000-08-07 | 2006-02-21 | Rosemount Inc. | Optical switch with moveable holographic optical element |
| US6825967B1 (en) | 2000-09-29 | 2004-11-30 | Calient Networks, Inc. | Shaped electrodes for micro-electro-mechanical-system (MEMS) devices to improve actuator performance and methods for fabricating the same |
| US6712121B2 (en) * | 2001-10-12 | 2004-03-30 | Kimberly-Clark Worldwide, Inc. | Antimicrobially-treated fabrics |
| US6987901B2 (en) | 2002-03-01 | 2006-01-17 | Rosemount, Inc. | Optical switch with 3D waveguides |
| US7619739B1 (en) | 2002-08-29 | 2009-11-17 | Science Applications International Corporation | Detection and identification of biological agents using Bragg filters |
| US7018563B1 (en) | 2002-11-26 | 2006-03-28 | Science Applications International Corporation | Tailoring material composition for optimization of application-specific switchable holograms |
| JP4390468B2 (en) * | 2003-03-24 | 2009-12-24 | 株式会社小松製作所 | Pipe layer |
| US6950173B1 (en) | 2003-04-08 | 2005-09-27 | Science Applications International Corporation | Optimizing performance parameters for switchable polymer dispersed liquid crystal optical elements |
| US7280735B2 (en) * | 2004-06-07 | 2007-10-09 | Andre Sean Thibault | Combined optical fiber wheel, beamsplitter, switch, and logic gate |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2243573A1 (en) * | 1973-09-06 | 1975-04-04 | Treheux Michel | Broadband electro-optical coupler for telephony - uses point holography by scanning photo-matrix with laser's and LED's |
| US3985975A (en) * | 1975-03-04 | 1976-10-12 | International Telephone And Telegraph Corporation | Holographic telephone switching system |
| FR2385266A1 (en) * | 1977-03-25 | 1978-10-20 | Thomson Csf | ELECTRO-OPTICAL SWITCHING DEVICE AND TELEPHONE AUTOMOTE SWITCH INCLUDING SUCH A DEVICE |
| US4278327A (en) * | 1979-11-26 | 1981-07-14 | Sperry Corporation | Liquid crystal matrices |
| US4385799A (en) * | 1980-06-26 | 1983-05-31 | Sperry Corporation | Dual array fiber liquid crystal optical switches |
| JPS57161827A (en) * | 1981-03-31 | 1982-10-05 | Yokogawa Hokushin Electric Corp | Optical changeover switch |
| US4516837A (en) * | 1983-02-22 | 1985-05-14 | Sperry Corporation | Electro-optical switch for unpolarized optical signals |
| FR2547150A1 (en) * | 1983-05-31 | 1984-12-07 | Cit Alcatel | OPTO-MECHANICAL SWITCH AND SPATIAL SWITCHING ASSEMBLY IMPLEMENTING THE SAME |
| JPS60182423A (en) * | 1984-02-29 | 1985-09-18 | Mitsubishi Electric Corp | Optical switch |
| DE3410629A1 (en) * | 1984-03-22 | 1985-10-03 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V., 8000 München | METHOD AND ARRANGEMENT FOR TRANSMITTING DIGITAL DATA BETWEEN DATA SOURCES AND DATA Sinks |
| DE3587515T2 (en) * | 1984-05-17 | 1994-03-17 | Nec Corp | Optical switching device. |
| GB8704016D0 (en) * | 1987-02-20 | 1987-04-15 | British Telecomm | Optical space switch |
-
1987
- 1987-01-29 GB GB878701996A patent/GB8701996D0/en active Pending
-
1988
- 1988-01-28 AU AU11595/88A patent/AU597149B2/en not_active Ceased
- 1988-01-28 EP EP88300758A patent/EP0277779A1/en not_active Withdrawn
- 1988-01-28 CA CA000557564A patent/CA1298116C/en not_active Expired - Fee Related
- 1988-01-28 JP JP63501311A patent/JPH01502710A/en active Pending
- 1988-01-28 US US07/249,560 patent/US4923269A/en not_active Expired - Fee Related
- 1988-01-28 WO PCT/GB1988/000052 patent/WO1988005986A1/en unknown
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| Publication number | Publication date |
|---|---|
| GB8701996D0 (en) | 1987-03-04 |
| EP0277779A1 (en) | 1988-08-10 |
| US4923269A (en) | 1990-05-08 |
| JPH01502710A (en) | 1989-09-14 |
| AU597149B2 (en) | 1990-05-24 |
| WO1988005986A1 (en) | 1988-08-11 |
| AU1159588A (en) | 1988-08-24 |
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