1989-04-27
1991-05-07
Miller, Stanley D.
350335, 350352, 350400, 350401, G02F 113, G02B 530
Patent
active
050131400
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an optical space switch.
R. A. Spanke in a paper entitled Architectures for Large Nonblocking Optical Space Switches, IEEE Journal of Quantum Electronics Vol. QE-22, No.6, June 1986, discusses the use of active, N to 1 combiners fabricated from optical space switch elements on Ti:LINbO.sub.3 for use in nonblocking N to N optical space switch architectures. Such known N to 1 space switches are capable of selectively switching a selected one of N optical signals to an output.
According to the present invention an optical switch comprises--
an optical output;
n optical deflection stages each comprising a polarization rotator responsive to a respective control signal to rotate the polarization of an optical signal through 90.degree., and a deflection means for selectively deflecting optical signals according to their polarization;
the n deflection stages being serially arranged to define 2.sup.n distinct source locations from where an optical signal is selectively deflectable successively by the n deflection stages to the optical output, a distinct combination of states of the n control signals corresponding to each location;
a plurality of up to 2.sup.n optical sources each located at one of the 2.sup.n source locations;
and in which each deflection stage preserves the spatial integrity of the deflected optical signals.
An advantage of the present invention over known optical switches capable of connecting one of N inputs to an output is that it can switch optical signals having up to two spatial dimensions. For example, each optical signal might be a complete databus or represent a page of computer memory so providing a means of optically switching information at a greatly increased rate.
All the optical signals which enter a given one of the deflection stages pass through the same polarization rotator which therefore operates on spatially multiplexed signal paths giving a significant reduction in the effective number of cross-points and which uses few optical and electro-optical subassemblies.
By spatial integrity is meant that although an input signal may be distorted spatially as it is switched to the output, for example expanded or contracted, there is a consistant mapping between the spatial elements of the switched input and output signals which preserves the information content of the spatial modulation.
In this specification, the term "optical" is intended to refer to that part of the electromagnetic spectrum which is generally known as the visible region together with those parts of the infra-red and ultra-violet regions at each end of the visible region capable of having the polarization rotated.
The deflection means may be an optical component which supports propagation of the optical signal in two directions dependant on the polarization of the signal, for example a bi-refringent crystal such as calcite, or one which selectively reflects light of a given polarization, such as a polarizing beam splitter. In this case a prism may be conveniently used to align incoming signals with the beamsplitter such that all selected signals from the deflection stage pass from the beamsplitter in the direction of the next deflection stage or the output.
Embodiments of the invention will now be described by way of example only by reference to the accompanying drawings on which
FIG. 1 is a schematic perspective view of an optical switch according to the present invention using a birefringent crystal deflection means;
FIG. 2 is a schematic side view of the optical switch of FIG. 1 illustrating its use with collimated optical signals;
FIG. 3 is a schematic end view of the optical switch of FIG. 1 but using divergent optical sources and having additional lenses to focus the sources onto the output;
FIG. 4 is a schematic end view of an optical switch using polarization beamsplitters and prisms as the deflection means; and
FIG. 5 is a diagramatic, perspective view of a generalized connection network formed from the N-fold array of optical switches of FIG. 4 having optical sources generated by
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Healey Peter
Mallinson Stephen R.
British Telecommunications public limited company
Mai Huy K.
Miller Stanley D.
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