Optical switch fabric with bias control

• US 9,485,552 B1
• Filed: 01/28/2016
• Issued: 11/01/2016
• Est. Priority Date: 01/28/2016
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Lee, Benjamin G., Schow, Clint L., Dupuis, Nicolas, Kuchta, Daniel M., Rylyakov, Alexander
• Primary Examiner(s): Li, Shi K
• Application Number:
  US15/009,084
• Time in Patent Office: 278 Days
• US Class Current: 1/1
• CPC Class Codes: H04B 10/07955 Monitoring or measuring power
• CPC Class Codes: H04Q 11/0001 using optical switching
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0039 Electrical control
• CPC Class Codes: H04Q 2011/0049 Crosstalk reduction; Noise; Power budget
• CPC Class Codes: H04Q 2011/0058 Crossbar; Matrix

Abstract

Methods and systems for bias control in an optical switch fabric include monitoring optical power at outputs of a plurality of switch elements in an N×N switch fabric that has N inputs, N outputs, and M≧2 stages. A bias control of a first of the plurality of switch elements is adjusted. It is determined whether the optical power at the outputs of the first switch element after bias control adjustment conform more closely to a predetermined criterion relative to the monitored optical power at the outputs of the first switch element prior to adjustment. The adjusting and determining steps are repeated for each of the remainder of the plurality of switch elements.

Claims

1. A method for bias control in an optical switch fabric, comprising:

monitoring optical power at outputs of a plurality of switch elements in an N×

N switch fabric that has N inputs, N outputs, and M≧

2 stages;

monitoring individual optical power at the outputs of every switch element in the switch fabric

adjusting a bias control of a first of the plurality of switch elements;

determining, using a processor, whether the optical power at the outputs of the first switch element after bias control adjustment match a predetermined harmonic signature more closely than the monitored optical power at the outputs of the first switch element prior to adjustment; and

repeating said steps of adjusting and determining for each of the remainder of the plurality of switch elements.

2. The method of claim 1, wherein each switch element comprises a Mach-Zehnder interferometer.

3. The method of claim 2, wherein determining the optical power at an output of a switch element comprises tapping one or more outputs of the Mach-Zehnder interferometer and measuring the tapped one or more outputs using a photodetector.

4. The method of claim 1, wherein monitoring the optical power at the outputs of a plurality of switch elements comprises monitoring individual optical power at the outputs of every switch element in the switch fabric.

5. The method of claim 1, wherein each switch element has a respective unique radio frequency tone.

6. The method of claim 5, wherein monitoring the optical power at the outputs comprises tone demultiplexing N multi-tone outputs.

7. The method of claim 1, further comprising repeating said adjusting and determining until the monitored optical power at the outputs of the first switch element converge on an optimal value according to the predetermined criterion.

8. A non-transitory computer readable storage medium comprising a computer readable program for bias control in an optical switch fabric, wherein the computer readable program when executed on a computer causes the computer to perform the steps of claim 1.

9. A method for bias control in an optical switch fabric, comprising:

monitoring optical power at outputs of a plurality of Mach-Zehnder interferometers in an N×

N switch fabric that has N inputs, N outputs, and M≧

2 stages by tapping one or more outputs of a final stage of the Mach Zehnder interferometers and measuring the tapped outputs using a photodetector;

tone demultiplexing the measured tapped outputs in accordance with a unique radio frequency tone assigned to each respective Mach-Zehnder interferometer;

adjusting a bias control of a first of the plurality of switch elements;

determining, using a processor, whether the optical power at the outputs of the first switch element after bias control adjustment conform more closely to a predetermined harmonic signature relative to the monitored optical power at the outputs of the first switch element prior to adjustment; and

repeating said steps of adjusting and determining for each of the remainder of the plurality of switch elements.

10. An optical switch fabric, comprising:

a plurality of switch elements in an N×

N arrangement that has N inputs, N outputs, and M≧

2 stages, wherein each switch element comprises a bias control configured to adjust a bias of the respective switch element;

a plurality of photodetectors configured to measure optical power at outputs of the plurality of switch elements;

a processor configured to trigger adjustment by the respective bias controls and to determine, for each switch element, whether the optical power at the output of each switch element match a predetermined harmonic signature more closely than the optical power at the output of that first switch element after an adjustment of that first switch element.

11. The optical switch fabric of claim 10, wherein each switch element comprises a Mach-Zehnder interferometer.

12. The optical switch fabric of claim 11, wherein the photodetectors are configured to tap and measure one or more outputs of the plurality of the Mach-Zehnder interferometers.

13. The optical switch fabric of claim 10, wherein the plurality of photodetectors are configured to monitor individual optical power at the outputs of every switch element in the switch fabric.

14. The optical switch fabric of claim 10, wherein each switch element has a respective unique radio frequency tone.

15. The optical switch fabric of claim 14, wherein the processor is further configured to demultiplexing N multi-tone outputs to determine an optical power at an output of each switch element.

16. The optical switch fabric of claim 10, wherein the processor is further configured to repeat said adjustment and determination until the monitored optical power at the outputs of the first switch element converge on an optimal value according to the predetermined criterion.