Optical space switch

• US 5,013,140 A
• Filed: 04/27/1989
• Issued: 05/07/1991
• Est. Priority Date: 09/11/1987
• Status: Expired due to Fees

• Current Assignee: British Telecommunications PLC (BT Group PLC)
• Original Assignee: British Telecommunications PLC (BT Group PLC)
• Inventors: Healey, Peter, Mallinson, Stephen R.
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US07/348,576
• Time in Patent Office: 740 Days
• Field of Search: 350/347 E, 350/347 R, 350/352, 350/335, 350/400, 350/401, 350/96.13, 350/377, 350/378
• US Class Current: 349/196
• CPC Class Codes: G02B 6/2817 using reflective elements to split or combine optical signals
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence

Abstract

An optical space switch comprising an optical output; three optical deflection stages each having a twisted-nematic liquid crystal polarization rotator responsive to a respective bi-state control signal and a calcite crystal deflection means for selectively deflecting optical signals according to their polarization. The deflection stages are arranged serially to define eight distinct source locations from where an optical signal is selectively deflectable successively by the deflection stages to the optical output. A distinct combination of states of the three control signals corresponds to each location. Each input is formed from an array of fibers so as to be capable of launching an optical signal which is spatially modulated transverse to the signal propagation direction. Each deflection stage preserves the spatial integrity of the deflected optical signals.

Claims

1. An optical space switch comprising:

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°

, and a deflection means for selectively deflecting optical signals according to their polarization;

said n deflection stages being serially arranged to define 2ⁿ distinct source locations from where any single optical signal is selectively deflectable successively by the n deflection stages to said optical output, a distinct combination of states of the n control signals corresponding to each location;

a plurality of up to 2ⁿ optical sources each located at one of said 2ⁿ source locations;

and in which each deflection stage preserves the spatial integrity of the deflected optical signals.

2. A switch as claimed in claim 1 in which the optical sources emit an optical signal whose spatial modulation is representative of at least one binary word.

5. A switch as claimed in either claims 1, 3 or 4 in which said deflection means comprises a birefringent material.

6. A switch as claimed in claim 5 in which said birefringent material is calcite.

7. A switch as claimed in either claims 1, 3 or 4 in which said deflection means comprises a combination of polarization beamsplitters and prisms.

8. A switch as claimed in either claims 1, 3 or 4 in which said polarization rotator is a twisted-nematic liquid crystal.

9. A switch as claimed in either claims 1, 3 or 4 in which the optical signals are collimated.

10. A switch as claimed in either claims 1, 3 or 4 in which said optical sources provide divergent optical signals and further comprising a means for directing the optical signal which emerges axially from the final deflection stage to said output.

11. A switch as claimed in either claims 1, 3 or 4 in which each said optical source is capable of launching an optical signal which is spatially modulated transverse to the signal propagation direction.

3. An optical space switch comprising:

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°

, and a deflection means for selectively deflecting optical signals according to their polarization;

said n deflection stages being serially arranged to define 2ⁿ distinct source locations from where any single optical signal is selectively deflectable successively by the n deflection stages to said optical output, a distinct combination of states of the n control signals corresponding to each location;

a plurality of up to 2ⁿ optical sources each located at one of said 2ⁿ source locations, said optical sources each comprising a plurality of optical fibers;

and in which each deflection stage preserves the spatial integrity of the deflected optical signals.

4. An optical space switch comprising:

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°

, and a deflection means for selectively deflecting optical signals according to their polarization;

said n deflection stages being serially arranged to define 2ⁿ distinct source locations from where any single optical signal is selectively deflectable successively by the n deflection stages to said optical output, a distinct combination of states of the n control signals corresponding to each location;

a plurality of up to 2ⁿ optical sources each located at one of said 2ⁿ emitter locations, said optical sources each comprising a plurality of individually modulated optical emitters;

and in which each deflection stage preserves the spatial integrity of the deflected optical signals.

12. An optical space switch comprising:

n optical deflection stages serially arranged, each comprising a polarization rotor and a deflector for selectively deflecting optical signals according to their polarization;

said polarization rotor alters the polarization of an optical signal in response to a control signal;

said n deflection stages define 2ⁿ distinct source locations, an optical signal from any of said locations is selectively deflectable to an optical output by said deflection stages, a unique combination of states of said control signals corresponding to each location, and

up to 2ⁿ optical sources each located at one of said source locations.

13. An optical connection network comprising:

n passive optical signal distributors, each distributor receiving an optical input signal and emitting m duplicate signals copied from said optical input signal;

m optical space switches wherein each switch receives at said source locations one of said m duplicate signals from each distributor, and said optical signals being the emitted signals from the distributor, each optical space switch comprising;

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°

, and a deflection means for selectively deflecting optical signals according to their polarization;

said n deflection stages being serially arranged to define 2ⁿ distinct source locations from where any single optical signal is selectively deflectable successively by the n deflection stages to said optical output, a distinct combination of states of the n control signals corresponding to each location;

a plurality of up to 2ⁿ optical sources each located at one of said 2ⁿ source locations;

and in which each deflection stage preserves the spatial integrity of the deflected optical signals.

14. A method of optically switching an array of up to n optical signals using n passive optical signal distributors and m optical space switches, each switch having an output, n deflection stages and 2ⁿ source locations for receiving signals from the distributors and each deflection stage comprising a polarization rotator responsive to a respective control signal and a deflector, said method comprising the steps of:

(a) inputting up to n optical signals into the distributors;

(b) distributing these signals such that m copies of each signal is emitted by a distributor and a copy signal is received by each of the optical switches, and each switch receiving up to n signals from n distributors;

(c) setting the control signals for the rotators such that a selected one of the up to n signals received by each switch is rotated and deflected to the output of each switch.

15. A method of optically switching one of up to n optical input signals to an output using an optical space switch having n deflection stages in which each stage has 2ⁿ distinct source locations and includes a polarization rotator responsive to a respective control signal and a deflector that selectively deflects an optical signal according to its polarization, said method comprising the steps of:

(a) inputting up to 2ⁿ optical signals into the switch such that each signal enters a unique source location,

(b) setting the control signals for the rotators such that the control signals correspond to a preselected one of the source locations, and

(c) adjusting the path of the optical signal entering the preselected source location by rotating the polarization of the signal and deflecting the optical signal in the deflection stages so that only the preselected signal reaches the output of the switch.