INTERFEROMETRIC FIBER OPTIC GYROSCOPE WITH OFF-FREQUENCY MODULATION SIGNALS

• US 20090040526A1
• Filed: 06/27/2008
• Published: 02/12/2009
• Est. Priority Date: 08/08/2007
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: WARD, PAUL A.
• Granted Patent: US 7,817,284 B2
• Time in Patent Office: Days
• US Class Current: 356/460
• CPC Class Codes: G01C 19/721 Details

Abstract

Interference in a rotation rate detector signal of an interferometric fiber-optic gyroscope from a bias phase modulator signal may be reduced or substantially avoided by transmitting one or more off-frequency signals having a frequency other than the eigenfrequency of the gyroscope towards a bias phase modulator, generating the bias phase modulator signal having a frequency substantially equal to the eigenfrequency of the gyroscope, and driving the bias phase modulator with the bias phase modulator signal.

Claims

1. A method for driving a bias phase modulator in an interferometric fiber-optic gyroscope, the method comprising:

transmitting, towards the bias phase modulator, at least one off-frequency signal having a frequency different from an eigenfrequency of the gyroscope;

generating, from the at least one off-frequency signal, a bias phase modulator signal having a frequency substantially equal to the eigenfrequency of the gyroscope; and

driving the bias phase modulator with the bias phase modulator signal.

2. The method of claim 1 further comprising generating the at least one off-frequency signal.

3. The method of claim 1, wherein two off-frequency signals are transmitted.

4. The method of claim 3, wherein the two off-frequency signals are offset by 90 degrees from one another.

5. The method of claim 3, wherein the two off-frequency signals are substantially equal in magnitude, but opposite in sign, to one another.

6. The method of claim 1, wherein each off-frequency signal has a frequency substantially equal to one-half the eigenfrequency of the gyroscope.

7. The method of claim 1, wherein each off-frequency signal has negligible signal power at or near the eigenfrequency of the gyroscope.

8. A signal converter for use in a gyroscope, comprising:

at least one input for receiving an off-frequency signal having a frequency different from an eigenfrequency of the gyroscope;

circuitry for generating, from the off-frequency signal, a bias phase modulator signal having a frequency substantially equal to the eigenfrequency of the gyroscope; and

an output for providing the bias phase modulator signal to a bias phase modulator of the gyroscope.

9. The signal converter of claim 8, wherein the signal converter comprises two inputs, each input for receiving a single off-frequency signal.

10. The signal converter of claim 9, wherein the two off-frequency signals are offset by 90 degrees from one another.

11. The signal converter of claim 9, wherein the two off-frequency signals are substantially equal in magnitude, but opposite in sign, to one another.

12. The signal converter of claim 8, wherein the off-frequency signal has a frequency substantially equal to one-half the eigenfrequency of the gyroscope.

13. The signal converter of claim 8, wherein the off-frequency signal has negligible signal power at or near the eigenfrequency of the gyroscope.

14. The signal converter of claim 8, wherein the circuitry comprises an XOR gate.

15. The signal converter of claim 8, wherein the circuitry comprises a rectifier circuit.

16. The signal converter of claim 8, wherein the circuitry introduces no appreciable delay between the off-frequency signal received at the input and the bias phase modulator signal provided at the output.

17. A system for driving a bias phase modulator in an interferometric fiber-optic gyroscope, the system comprising:

an off-frequency signal generator for transmitting at least one off-frequency signal having a frequency different from an eigenfrequency of the gyroscope; and

a signal converter for i) generating, from the at least one off-frequency signal, a bias phase modulator signal having a frequency substantially equal to the eigenfrequency of the gyroscope, and ii) providing the bias phase modulator signal to the bias phase modulator.

18. The system of claim 17, wherein the off-frequency signal generator is further configured to generate the at least one off-frequency signal.

19. The system of claim 17, wherein each off-frequency signal has negligible signal power at or near the eigenfrequency of the gyroscope.

20. The system of claim 17 further comprising a signal processing circuit for removing out-of-band interference from a rotation rate detector signal output from the gyroscope.

21. The system of claim 17 further comprising the bias phase modulator.

22. A method for driving a bias phase modulator in an interferometric fiber-optic gyroscope, the method comprising:

transmitting, towards the bias phase modulator, at least one first signal having negligible signal power at or near an eigenfrequency of the gyroscope;

generating, from the at least one first signal, a bias phase modulator signal having measurable signal power at or near the eigenfrequency of the gyroscope; and

driving the bias phase modulator with the bias phase modulator signal.

23. A system for driving a bias phase modulator in an interferometric fiber-optic gyroscope, the system comprising:

means for transmitting, towards the bias phase modulator, at least one first signal having negligible signal power at or near an eigenfrequency of the gyroscope;

means for generating, from the at least one first signal, a bias phase modulator signal having measurable signal power at or near the eigenfrequency of the gyroscope; and

means for driving the bias phase modulator with the bias phase modulator signal.