1988-10-17
1990-08-28
Arnold, Bruce Y.
350 368, 350 373, 350 378, 350 9615, G02B 532
Patent
active
049520105
DESCRIPTION:
BRIEF SUMMARY
RELATED APPLICATION
This application is related to commonly assigned U.S. patent application Ser. No. 07/249,560, filed Sept. 23, 1988 for a BIDIRECTIONAL OPTICAL SPACE SWITCH naming Peter Healey as sole inventor now U.S. Pat. No. 4,923,269.
BACKGROUND OF THE INVENTION
This invention relates to an optical space switch which is capable of use in a centralised switching system for an optical network. A centralised switching system is the simplest active network which is compatible with optical and electronic multiplexing, offers the maximum network size, range, and flexibility and is also compatible with the existing wire-network.
SUMMARY OF THE INVENTION
According to this invention an optical space switch for connecting light from one of a number of inputs to a selected one of a number of outputs includes a number of multiplexed phase volume holograms, a spatial light modulator for imposing a selected phase change on light passing through it, distribution means for coupling light from the inputs via the spatial light modulator to the multiplexed phase volume holograms, and collection means for collecting light diffracted by the multiplexed phase volume holograms, each multiplexed phase volume hologram diffracting light to a selected output in dependence upon the phase change imposed by the spatial light modulator on the light incident upon that hologram.
Preferably there are the same number of multiplexed phase volume holograms as there are inputs and the same number of holograms in each multiplexed phase volume hologram as there are outputs and the distribution means couples light from each input via the spatial light modulator to its respective multiplexed phase volume hologram and the collection means collects the light diffracted by the multiplexed phase volume holograms and applies it to its respective output. This arrangement provides total flexibility and enables each and every input to be coupled to each and every output. However, in some circumstances it is desirable to be able to arrange for two inputs to be switched together by the optical switch or, for example, two outputs to receive the same signal. In this case, there may be fewer multiplexed phase volume holograms than there are inputs and greater numbers of holograms in each multiple of phase volume hologram than there are outputs. The distribution and collection means are formed by lenses or holograms arranged to couple light emitted from a particular input to a particular multiplexed phase volume hologram via the spatial light modulator and arranged to receive light diffracted by the multiplexed phase volume holograms and couple it to the individual outputs.
The inputs may be provided by the ends of a number of optical fibre waveguides, or, alternatively, the inputs may be formed by a number of optical devices the outputs of which are modulated by the input signals. Thus, the optical inputs may all be taken from a single optical source which is split and each split component 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 outputs may be formed by the ends of an array of optical waveguides leading away from the optical space switch and, in this case they are preferably formed by an array of multimode optical fibres. Alternatively, the outputs may be formed by an array of photo detectors or other active devices such as self electrooptic effect devices which detect, amplify, or regenerate the light received. Photodetectors may form part of an optical regenerator which, in turn, generates an output in the form of an optical signal. The input may be arranged in a linear array and, in this case the output may also be arranged as a linear array extending in a direction perpendicular to that of the linear input array. Alternatively, the input and/or outputs may have the form of two dimensional matrix arrays.
The spatial light modulator may be formed by a material the refractive index of whi
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Healey Peter
Smith David W.
Arnold Bruce Y.
British Telecommunications public limited company
Callaghan Terry S.
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