DETERMINING AND COMPENSATING FOR MODULATOR DYNAMICS IN INTERFEROMETRIC FIBER-OPTIC GYROSCOPES

• US 20090201510A1
• Filed: 01/22/2008
• Published: 08/13/2009
• Est. Priority Date: 01/22/2007
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Kishinevsky, Michael, Soucy, Matthew, Smith, Stephen P., Ward, Paul A., Zarinetchi, Farhad
• Granted Patent: US 7,872,758 B2
• Time in Patent Office: Days
• US Class Current: 356/460
• CPC Class Codes: G01C 19/726 Phase nulling gyrometers, i.e. compensating the Sagnac phase shift in a closed loop system

Abstract

Determining linear modulator dynamics in an interferometric fiber-optic gyroscope may be accomplished by applying a stimulus at a point within the gyroscope, observing a response in an output of the gyroscope, and determining, from the observed response, the linear modulator dynamics.

Claims

1. A method for determining, in-situ, linear modulator dynamics in an interferometric fiber-optic gyroscope, comprising:

applying a first signal to a phase modulator located within an interferometric fiber-optic gyroscope;

observing a response in an output of the interferometric fiber-optic gyroscope to the first signal; and

determining, from the observed response, linear modulator dynamics introduced by the phase modulator.

2. The method of claim 1, wherein determining the linear modulator dynamics comprises determining at least one pole of the phase modulator.

3. The method of claim 1, wherein determining the linear modulator dynamics comprises determining at least one zero of the phase modulator.

4. The method of claim 1, wherein determining the linear modulator dynamics further comprises determining a high frequency gain of the phase modulator.

5. The method of claim 1 further comprising compensating for the linear modulator dynamics.

6. The method of claim 5, wherein the linear modulator dynamics are compensated by pre-filtering a drive signal before it drives the phase modulator.

7. The method of claim 6, wherein the drive signal is multiplied by an inverse of a transfer function for the phase modulator.

8. The method of claim 5, wherein the compensation of the linear modulator dynamics occurs while the interferometric fiber-optic gyroscope is also performing functions unrelated to the compensation.

9. The method of claim 1, wherein the first signal applied to the phase modulator comprises a step.

10. A method for determining, in-situ, linear modulator dynamics in an interferometric fiber-optic gyroscope, comprising:

applying a stimulus at a point within an interferometric fiber-optic gyroscope;

observing a response in an output of the interferometric fiber-optic gyroscope to the stimulus; and

determining, from the observed response, linear modulator dynamics present in the interferometric fiber-optic gyroscope.

11. The method of claim 10, wherein determining the linear modulator dynamics comprises determining at least one pole of a phase modulator in the interferometric fiber-optic gyroscope.

12. The method of claim 10, wherein determining the linear modulator dynamics comprises determining at least one zero of a phase modulator in the interferometric fiber-optic gyroscope.

13. The method of claim 10, wherein determining the linear modulator dynamics further comprises determining a high frequency gain of a phase modulator in the interferometric fiber-optic gyroscope.

14. The method of claim 10 further comprising compensating for the linear modulator dynamics.

15. The method of claim 14, wherein the linear modulator dynamics are compensated by pre-filtering a drive signal before it drives a phase modulator in the interferometric fiber-optic gyroscope.

16. The method of claim 15, wherein the drive signal is multiplied by an inverse of a transfer function for the phase modulator.

17. The method of claim 14, wherein the compensation of the linear modulator dynamics occurs while the interferometric fiber-optic gyroscope is also performing functions unrelated to the compensation.

18. An interferometric fiber-optic gyroscope, comprising:

a phase modulator; and

a means for pre-filtering a drive signal before it drives the phase modulator, thereby compensating for linear modulator dynamics present in the interferometric fiber-optic gyroscope.

19. The interferometric fiber-optic gyroscope of claim 18 further comprising a means for determining a transfer function of the phase modulator.

20. The interferometric fiber-optic gyroscope of claim 19, wherein the means for pre-filtering the drive signal multiplies the drive signal by an inverse of the transfer function.

21. The interferometric fiber-optic gyroscope of claim 18, wherein the means for pre-filtering the drive signal is a digital pre-emphasis filter.

22. A method for compensating a frequency-dependent complex gain of a phase modulator, comprising:

applying a first signal to a phase modulator located within an interferometric fiber-optic gyroscope;

determining a transfer function of the phase modulator based, at least in part, on a response in an output of the interferometric fiber-optic gyroscope to the first signal; and

multiplying a drive signal of the phase modulator with an inverse of the transfer function.

23. An interferometric fiber-optic gyroscope, comprising:

a phase modulator; and

a means for multiplying a drive signal for the phase modulator with an inverse of a transfer function of the phase modulator before the drive signal drives the phase modulator, thereby compensating for linear modulator dynamics present in the interferometric fiber-optic gyroscope.

24. The interferometric fiber-optic gyroscope of claim 23 further comprising a means for determining the transfer function of the phase modulator.