Protection schemes for mirror-failure in free-space micromachined optical switches

• US 6,278,812 B1
• Filed: 12/14/1999
• Issued: 08/21/2001
• Est. Priority Date: 12/14/1998
• Status: Expired due to Term

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Simmons, Jane M., Lin, Lih Y., Saleh, Adel A. M.
• Primary Examiner(s): Sanghavi, Hemang
• Assistant Examiner(s): Doan, Jennifer
• Application Number:
  US09/460,460
• Time in Patent Office: 616 Days
• Field of Search: 385/16, 385/17, 385/18, 385/19, 385/20, 385/24, 385/89
• US Class Current: 385/18
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3546 NxM switch, i.e. a regular array of switches elements of matrix type constellation
• CPC Class Codes: G02B 6/3562 Switch of the bypass type, i.e. enabling a change of path in a network, e.g. to bypass a failed element in the network

Abstract

The present invention provides a device and method for achieving protection in a free-space micromachined optical switching fabric. The present invention provides two protection schemes for mirror failures, which utilize either existing switching mirrors or additional integrated mirrors without extra fabrication effort or performance-degradation of the switch fabric. A switch fabric includes a plurality of micromachined free-rotating mirrors arranged in a rectilinear matrix configuration. The mirrors are reflective on both front and back sides. According to one embodiment of the present invention, upon the detection of a failed mirror associated with a transmission between an input and an output, a transmission path is determined that includes a backside of a pivot mirror. A transmission path is then established between the input and the output that utilizes the backside of the pivot mirror.

Claims

1. A method for performing protection in a free-space micro-machined optical switching fabric, wherein the switching fabric receives a plurality of inputs (M), and provides a plurality of outputs (N), comprising a matrix of micromachined free-rotating mirrors arranged in a plurality of (N) parallel rows and (M) columns wherein each of the plurality of mirrors is in either one of an actuated or non-actuated state comprising the steps of:

detecting a failed mirror, wherein the failed mirror is associated with a transmission path between an input and an output;

determining a transmission path between the input and the output, wherein the transmission path includes a backside of a pivot mirror that is in an actuated state;

actuating at least one mirror, to establish the transmission path between the input and the output that includes the backside of the pivot mirror.

2. The method according to claim 1, wherein the step of actuating at least one mirror further includes the steps of:

actuating a first mirror in a same row as the pivot mirror and a same column as the failed mirror;

actuating a second mirror in a same column as the pivot mirror and a same row as the failed mirror.

3. The method according to claim 1, wherein the mirrors include a first and a second side, wherein the first and second side include a reflective material.

4. A method for performing protection in a free-space micro-machined optical switching fabric, wherein the switching fabric receives a plurality of inputs (M), and provides a plurality of outputs (N), comprising a matrix of micromachined free-rotating mirrors arranged in a plurality of (N) parallel rows and (M) columns wherein each of the plurality of mirrors is in either one of an actuated or non-actuated state columns comprising the steps of:

detecting a failed mirror, wherein the failed mirror is located in a row Fr and a column Fc of the matrix;

determining a pivot mirror, in a row (Pr) and a column (Pc), wherein the pivot mirror is in an actuated state and Pr<

Fr and Pc<

Fc;

actuating a first mirror, wherein the first mirror is located in a row Pr and a column Fc;

actuating a second mirror, wherein the second mirror is located in a row Fr and a column Pc.

5. The method according to claim 4, wherein the mirrors include a first and a second side, wherein the first and second side include a reflective material.

6. A method for performing protection in a free-space micro-machined optical switching fabric, wherein the switching fabric receives a plurality of inputs (M), and provides a plurality of outputs (N), comprising a matrix of micromachined free-rotating mirrors, arranged in a plurality of N parallel rows and M parallel columns wherein each of the plurality of mirrors is in either one of an actuated or a non-actuated state comprising the steps of:

providing at least one protection row, wherein the protection row includes a plurality of mirrors;

providing at least one protection column, wherein the protection column includes a plurality of mirrors;

determining a failed mirror, wherein the failed mirror is associated with an input and an output;

determining a transmission path between the input and the output associated with the failed mirror that includes a first mirror located in the protection row and a second mirror in the protection column;

actuating at least one mirror, to establish the transmission path between the first mirror and the second mirror.

7. The method according to claim 6, wherein the transmission path includes a pivot mirror co-located in the protection row and the protection column.

8. A method for performing protection in a free-space micro-machined optical switching fabric, wherein the switching fabric receives a plurality of inputs (M), and provides a plurality of outputs (N), comprising a matrix of micromachined free-rotating mirrors, arranged in a plurality of N parallel rows and M parallel columns wherein each of the plurality of mirrors is in either one of an actuated or a non-actuated state comprising the steps of:

providing at least one protection row, wherein the protection row includes a plurality of mirrors;

providing at least one protection column, wherein the protection column includes a plurality of mirrors and wherein the protection column includes a pivot mirror co-located in the protection row;

actuating the pivot mirror, wherein the pivot mirror provides a transmission path between at least one of the mirrors in the protection row and at least one of the mirrors in the protection column, wherein the transmission path includes a backside of the pivot mirror;

determining a failed mirror, wherein the failed mirror is associated with an input and an output;

determining a transmission path between the input and the output associated with the failed mirror that includes a first mirror located in the protection row, a backside of the pivot mirror and a second mirror in the protection column; and

actuating the first mirror in the protection row and the second mirror in the protection column.

9. An optical cross-connect switch with protection comprising:

at least one input;

at least one output;

a switching fabric, including a plurality of micromachined mirrors arranged in a rectilinear configuration of rows and columns, wherein each of the mirrors establishes a transmission path between a single input and a single output, and wherein each micromachined mirrors includes actuation means for selectively placing the mirror in one of an actuated or non-actuated state, wherein the actuation means receives a signal for placing an associated mirror in one of an actuated and a non-actuated state;

a control processor, coupled to the actuation means of each of the mirrors, wherein the control processor transmits a signal to each of the actuation means associated with each of the plurality of mirrors for placing the associated mirror in one of an actuated or non-actuated state, and wherein the processor is adapted to;

detect a failed mirror, wherein the failed mirror is associated with a transmission path between an input and an output;

determine a transmission path between the input and the output,

wherein the transmission path includes a backside of a pivot mirror that is in an actuated state;

transmit a signal to at least one actuation means to establish the transmission path between the input and the output that includes the backside of the pivot mirror.

10. An optical cross-connect switch with protection comprising:

at least one input;

at least one output;

a switching fabric, including a plurality of micromachined mirrors arranged in a rectilinear configuration of rows and columns, wherein each of the mirrors establishes a transmission path between a single input and a single output, and wherein each micromachined mirrors includes actuation means for selectively placing the mirror in one of an actuated or non-actuated state, wherein the actuation means receives a signal for placing an associated mirror in one of an actuated and a non-actuated state;

at least one protection row, wherein the protection row includes a plurality of micromachined mirrors;

at least one protection column, wherein the protection column includes a plurality of micromachined mirrors;

a control processor, coupled to the actuation means of each of the mirrors, wherein the control processor transmits a signal to each of the actuation means associated with each of the plurality of mirrors for placing the associated mirror in one of an actuated or non-actuated state, and wherein the processor is adapted to;

detect a failed mirror, wherein the failed mirror is associated with a transmission path between an input and an output;

determine a transmission path between the input and the output associated with the failed mirror that includes a first mirror located in the protection row, a backside of a pivot mirror and a second mirror in the protection column wherein the transmission path includes a backside of a pivot mirror that is in an actuated state;

actuating the first mirror in the protection row and the second mirror in the protection column.