Feedback control system for a MEMS based optical switching fabric

• US 6,614,954 B2
• Filed: 10/24/2001
• Issued: 09/02/2003
• Est. Priority Date: 10/24/2001
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Transparent Networks, Inc.
• Inventors: Sprague, Randall B., Hawkins, Daryl Ray, Huang, Cheng-Chung, Skurnik, David, Abbott, Eric Charles
• Primary Examiner(s): Lee, John D.
• Assistant Examiner(s): WONG, TINA MEI SENG
• Application Number:
  US10/003,659
• Publication Number:
  US 20030077026A1
• Time in Patent Office: 678 Days
• Field of Search: 385/17, 385/18
• US Class Current: 385/18
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3556 NxM switch, i.e. regular arrays of switches elements of matrix type constellation
• CPC Class Codes: G02B 6/359 of the position of the moving element itself during switching, i.e. without monitoring the switched beams

Abstract

A control system for controlling individual mirrors in a MEMS-based optical switching fabric is presented. The control system includes a position sensitive detector positioned to receive a control beam reflected from individual mirrors of a first mirror array. In some embodiments, the control beam can be time-multiplexed with a calibration beam. The position of the control beam corrected in response to the position of the calibration beam can be compared with a position calculated on the port assignment of the individual mirrors in order to provide feedback to a feed-back based control system for the individual mirrors.

Claims

1. A method of controlling an optical switching fabric, comprising:

receiving port assignment for a first mirror on a first mirror array;

calculating a target position of a first control beam reflected from the first mirror on a corresponding cell of a first position sensitive detector;

measuring an actual position of the first control beam on the cell;

adjusting the orientation of the first mirror so that the measured position matches the target position; and

maintaining the orientation of the first mirror so that the measured position matches the target position.

2. The method of claim 1, wherein calculating the target position includes determining the target position from a look-up table based on the port assignment.

3. The method of claim 1, wherein maintaining the orientation of the first mirror includes

measuring the position of the first control beam in a first time interval;

measuring the position of a first calibration beam in a second time interval;

correcting the position of the first control beam in response to the position of the first calibration beam in order to obtain a measured position;

comparing the measured position with the target position;

calculating a voltage correction from the comparison of the measured position with the target position;

applying the voltage correction to actuators of the first mirror in order to alter the orientation of the first mirror.

4. The method of claim 3, further including calculating an estimated state of the first mirror.

5. The method of claim 4, wherein the state includes an estimate of an angular position of the first mirror.

6. The method of claim 5, wherein calculating the voltage correction includes

calculating a desired torque to apply to the first mirror to achieve the desired position;

and

converting the desired torque to the voltage correction.

7. The method of claim 6, wherein calculating the desired torque includes adding the desired position times a first factor, the error signal times a second factor, and an estimated state of the mirror times a matrix multiplier.

8. The method of claim 6, wherein converting the desired torque to the voltage correction includes calculating the voltage based on an estimate of the angular orientation of the first mirror and a model of the response of the first mirror.