Optical switch

• US 4,969,717 A
• Filed: 01/23/1989
• Issued: 11/13/1990
• Est. Priority Date: 06/03/1987
• Status: Expired due to Term

• Current Assignee: British Telecommunications PLC (BT Group PLC)
• Original Assignee: British Telecommunications PLC (BT Group PLC)
• Inventors: Mallinson, Stephen R.
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US07/303,662
• Time in Patent Office: 659 Days
• Field of Search: 350/335, 350/334, 350/377, 350/378, 350/400, 350/403, 350/347 E, 350/347 R, 350/338
• US Class Current: 349/196
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence

Abstract

An optical switch includes a series of 2(n-1) macro-cells each having a variable polarization rotating cell and a birefringent cell. Each rotating cell is divided into individually addressable and switchable sub-cells. Some of the macro-cells have birefringent cells having a first orientation. In these macro-cells, sub-cells switch light passing through position Pi to either position Pi or Pi+1 of the rotating cell of the next macro-cell in the series. Other macro-cells have birefringent cells having a second orientation. In these macro-cells, the sub-cells switch light passing through position Pi to either position Pi or Pi-1 of the rotating cell of the next macro-cell in the series. The sub-cells of the macro-cells are positioned such that light from any one of several inputs is switchable independently to any one of several outputs.

Claims

1. An optical switch comprising:

a series of 2(n-1) macro-cells each having a variable polarization rotating cell with up to n individually addressable sub-cells, each of said sub-cells being located at one of n positions Pl to Pn, and a birefringent cell adjacent said rotating cell;

(n-1) of said birefringent cells being in a first orientation so that light passing through an addressable sub-cell position Pi is switchable to pass through either of sub-cell positions Pi or Pi+l of said rotating cell of the next macro-cell in said series, and

(n-1) birefringent cells being in a second orientation so that light passing through an addressable sub-cell position Pi is switchable to pass through either of sub-cell positions Pi or Pi-l of said rotating cell of the next macro-cell in said series,

said sub-cells being positioned to provide that light from any one of m inputs is switchable independently to any of m outputs, where m is less than or equal to n and greater than 1.

2. An optical switch as claimed in claim 1 in which said variable polarization rotating sub-cells are liquid crystal cells.

3. An optical switch as claimed in claim 2 in which said liquid crystal is a smectic c liquid crystal.

4. A optical switch as claimed in any one of claims 1 through 3 in which said birefringent cells are calcite crystals.

5. An optical switch as claimed in any one of claims 1, 2, or 3 in which said birefringent cells comprise stressed polymer sheets.

6. An optical switch as claimed in any one of claims 1, 2 or 3 which macro-cells having birefringent cells of the same orientation are grouped together.

7. An optical switch as claimed in any one of claims 1, 2 or 3 in which said macro-cells are grouped in pairs of macro-cells, each of said pairs including said first orientation and said second orientation birefringent cells.

8. An optical switch having a series of macro-cells, each said macro-cell comprising:

a variable polarization rotating cell divided into sub-cells, each of said sub-cells being located at one of n positions P1 to Pn;

a birefringent cell adjacent to said rotating cell;

said birefringent cell in each of a first portion of said macro-cells having a first orientation, said sub-cells being switchable so that light entering sub-cell position Pi in one of said first portion macro-cells passes through to either sub-cell position Pi or Pi+1 in the next macro-cell in said series;

said birefringent cell in each of a second portion of said macro-cells having a second orientation, said sub-cells being switchable so that light entering sub-cell position Pi in one of said second portion macro-cells passes through to either sub-cell position Pi or Pi-1 in the next macro-cell in said series, and

said sub-cells being positioned to direct light from any one of a plurality of inputs to any one of a plurality of outputs.

9. An optical switch as in claim 8 having 2(n-1) of said macro-cells, and in which the number said first portion of macro-cells is (n-1), and the number of said second portion macro-cells is (n-1).

10. An optical switch comprising:

a series of macro-cells each having a variable polarization rotating cell with up to n individually addressable sub-cells and a birefringent cell adjacent to said rotating cell;

each of said sub-cells located at one of n positions P1 to Pn, said sub-cells being switchable so that light entering sub-cell position Pi in one of said macro-cells passes through to either sub-cell position Pi or Pi+1 in the next macro-cell in said series;

a mirror adjacent to the last macro-cell in said series, said mirror reflecting light exiting said last macro-cell, and

said sub-cells being positioned to direct light from any one of m inputs back to any one of said m inputs, where m is less than or equal to n and greater than one.

11. An optical switch as in claim 10 in which said rotating sub-cells comprise liquid crystal cells.

12. An optical switch as in claim 11 in which said liquid crystal cells comprise smectic c liquid crystals.

13. An optical switch as in any one of claims 10-12 in which said birefringent cells comprise calcite crystals.

14. An optical switch as in any of claims 10-12 in which said birefringent cells comprise stressed polymer sheets.

15. An optical switch including a series of cascaded macro-cell switches, each said macro-cell switch comprising:

a birefringent cell; and

an plurality of individually controllable polarization rotating sub-cells located adjacent said birefringent cell at corresponding n optical input/output port positions P1 to Pn;

said birefringent cell having predetermined orientation and dimensions to cause optical signals from a given input port position Pi to pass (a) to the same output port position Pi or (b) to a next adjacent output port position (Pi+1 or Pi-1) depending upon the state of the corresponding polarization rotating cell and the orientation of said birefringent cell.

16. An optical switch as in claim 15 having 2(n-1) macro-cell switches and having n of said polarization rotating sub-cells disposed in a linear array adjacent an input face of the birefringent cell for each said macro-cell switch.

17. An optical switch as in claim 15 having 2(n-1) macro-cell switches and having (n-1) of said macro-cell switches with birefringent cells of a first orientation and having (n-1) of said macro-cell switches with birefringent cells of a second orientation,

macro cells having said first orientation directing optical signals input at Pi to output position Pi+1 depending upon the state of the ith polarization rotating sub-cell for that macro-cell;

macro-cells having said second orientation directing optical signals input at Pi to output position Pi-1 depending upon the state of the ith polarization rotating sub-cell for that macro-cell.

18. An optical switch as in claim 15 further comprising:

a reflective surface disposed at the output of said series of cascaded macro-cell switches so as to redirect output optical signals back through the macro-cells.