Positioning a movable reflector in an optical switch

• US 6,610,974 B1
• Filed: 06/05/2000
• Issued: 08/26/2003
• Est. Priority Date: 06/05/2000
• Status: Expired due to Term

• Current Assignee: Calient AI Incorporated
• Original Assignee: Calient Networks Incorporated
• Inventors: Hunt, Peter, White, Kevin
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): KAO, CHIH CHENG G
• Application Number:
  US09/586,711
• Time in Patent Office: 1,177 Days
• Field of Search: 250/214.SW, 250/252.1, 250/227.22, 250/227.14, 250/227.21, 385/18, 385/16, 385/17, 385/52, 359/223
• US Class Current: 250/227.22
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• 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 6/3564 Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841
• CPC Class Codes: G02B 6/358 Latching of the moving element, i.e. maintaining or holding the moving element in place once operation has been performed; includes a mechanically bistable system
• CPC Class Codes: G02B 6/3584 constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching MEMS per se B81B, B81C
• CPC Class Codes: G02B 6/3588 of the processed beams, i.e. controlling during switching of orientation, alignment, or beam propagation properties such as intensity, size or shape

Abstract

A method for positioning a movable reflector in an optical switch. A set of optical power values are generated by measuring optical power related to optical reflections from the movable reflection for a plurality of positions of the movable reflector. A processor is used to generate a mathematical approximation of a relationship of optical power versus reflector position based on the set of optical power values. A position of the movable reflector is chosen based on a point in the mathematical approximation of the relationship of optical power versus reflector position.

Claims

1. A method for positioning a movable reflector in an optical switch, comprising:

(a) taking a plurality of optical power samples associated with optical reflections from the movable reflector for a position of the movable reflector;

(b) using a processor to average the plurality of optical power samples to produce an average optical power value for the position of the movable reflector;

(c) repeating the above steps (a) and (b) for each of a plurality of positions of the movable reflector to produce a set of average optical power values associated with a plurality of positions of the movable reflector;

(d) using the processor to generate a mathematical approximation of a relationship of optical power versus reflector position based on the set of average optical power values;

(e) choosing a position of the movable reflector based on a point in the mathematical approximation of the relationship of optical power versus reflector position.

2. The method of claim 1, wherein the mathematical approximation is substantially a Gaussian curve.

3. The method of claim 1, wherein the mathematical approximation is substantially a parabolic curve.

4. The method of claim 2, wherein the point in the mathematical approximation that is used to choose the mirror position is substantially the peak point in the Gaussian curve.

5. The method of claim 1, wherein the movable reflector is a gimbaled mirror in a microelectromechanical system (MEMS) device.

6. The method of claim 1, wherein the optical reflections from the movable reflector comprise coherent light carrying data.

7. The method of claim 1, wherein procedures (a) through (e) are repeated during normal operation of the optical switch.

8. A method for positioning a movable reflector in an optical switch, comprising:

(a) performing a first positioning procedure for the movable reflector, comprising;

(i) generating a first set of optical power values by measuring optical power related to optical reflections from the movable reflector for a first pattern of positions of the movable reflector;

(ii) using a processor to generate a first mathematical approximation of a first relationship of optical power versus reflector position based on the first set of optical power values;

(iii) choosing a first position of the movable reflector based on a first point in the first mathematical approximation;

(b) performing a second positioning procedure for the movable reflector, comprising;

(i) generating a second set of optical power values by measuring optical power related to optical reflections from the movable reflector for a second pattern of positions of the movable reflector, wherein the second pattern has smaller mirror displacements than the first pattern;

(ii) using the processor to generate a second mathematical approximation of a second relationship of optical power versus reflector position based on the second set of optical power values;

(iii) choosing a second position of the movable reflector based on a second point in the second mathematical approximation;

(c) performing a third positioning procedure for the movable reflector, comprising;

(i) taking a plurality of optical power samples associated with optical reflections from the movable reflector for a position of the movable reflector;

(ii) using the processor to average the plurality of optical power samples to produce a mean optical power value for the position of the movable reflector;

(iii) repeating the above procedures (c) (i) and (c) (ii) for each of a rest of positions of a third pattern of positions of the movable reflector to produce a third set of optical power values, wherein the third pattern has smaller mirrored displacements than the second pattern;

(iv) using the processor to generate a third mathematical approximation of the third relationship of optical power versus reflector position based on the third set of optical power values;

(v) choosing a third position of the movable reflector based on a third point in the third mathematical approximation.

9. The method of claim 8, wherein the third positioning procedure uses the second position of the movable reflector as a starting point.

10. The method of claim 8, wherein the first, second, and third mathematical approximations are each a substantially Gaussian curve.

11. The method of claim 8, wherein the movable reflector is a gimbaled mirror of a microelectromechanial system (MEMS) device.