Residual intensity modulation (RIM) control loop in a resonator fiber-optic gyroscope (RFOG)

• US 8,446,589 B2
• Filed: 10/19/2009
• Issued: 05/21/2013
• Est. Priority Date: 03/06/2009
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Strandjord, Lee, Sanders, Glen A., Qiu, Tiequn
• Primary Examiner(s): LEE, HWA S
• Application Number:
  US12/581,715
• Publication Number:
  US 20100225923A1
• Time in Patent Office: 1,310 Days
• Field of Search: 356459-476
• US Class Current: 356/461
• CPC Class Codes: G01C 19/727 using a passive ring resonator

Abstract

Systems and methods for reducing intensity modulation-induced rotation rate measurement error in a resonator optical gyroscope. The method includes tapping an intensity modulated light beam, directing a portion of the tapped light beam toward a photo detector, outputting from the photo detector a signal proportional to the amplitude variation of the light beam, amplifying the signal, and then providing the signal to the intensity modulator as a control input. Intensity modulation-induced error is reduced by an amount proportional to the gain of the feedback loop.

Claims

1. A method for improving the performance of a gyroscope, comprising:

providing a light beam from a laser source as an input for a resonator, wherein providing the light beam comprises;

measuring intensity modulation-induced amplitude variation in the light beam;

modulating the light beam to reduce intensity modulation-induced measurement error by controlling intensity variations occurring at frequencies around the modulation frequency, wherein the modulation is controlled by a negative feedback signal received from a servo electronics component;

receiving the light beam from the resonator in a demodulation component to detect a signal that is indicative of the difference in the resonance frequency and the laser frequency; and

driving the light beam produced by the laser source to a resonance frequency with the detected signal.

2. The method of claim 1, further comprising:

directing the light beam to an intensity modulator positioned upstream from a gyroscope resonator;

re-directing at least a portion of the light beam received from the intensity modulator toward a photodetector;

outputting from the photo detector a signal proportional to an amplitude of the re-directed light beam at a modulation frequency;

providing an outputted signal to the intensity modulator as a control input; and

the modulating comprises modulating the light beam with the intensity modulator using the outputted signal as a control input.

3. The method of claim 1, further comprising amplifying the output of the negative feedback loop before providing the output to an intensity modulator.

4. The method of claim 1, wherein the gyroscope is a component of a resonance fiber-optic gyroscope (RFOG).

5. An apparatus for improving resonator fiber optic gyroscope performance comprising:

at least one laser source comprising a residual intensity modulation servo loop configured to reduce intensity modulation-induced measurement error by controlling intensity variations occurring at frequencies around the modulation frequency, wherein the modulation is controlled by a negative feedback signal received from a servo electronics component in the servo loop;

a resonator coupled to receive a light beam from the at least one laser source; and

a demodulation component coupled to receive the light beam from the resonator, wherein the demodulation component detects a signal that is indicative of the difference in the resonance frequency and the laser frequency, the signal driving the at least one laser source such that the light beam is driven to a resonance frequency.

6. The apparatus of claim 5, wherein the residual modulation servo loop comprises:

an intensity modulator;

a tap coupler; and

a photo detector;

wherein an input of the intensity modulator is communicatively coupled with the output of the laser source, an input of the tap coupler is communicatively coupled with an output of the intensity modulator, an input of the photo detector is communicatively coupled with an output of the tap coupler, and an output of the photo detector is communicatively coupled with a control port of the intensity modulator; and

wherein the intensity modulator reduces amplitude variation in a light beam received from the laser source in response to a feedback signal from the photo detector.

7. The apparatus of claim 6, wherein an input of the servo electronics component is communicatively coupled with the output of the photo detector, wherein an output of the servo electronics component is communicatively coupled with the control port of the intensity modulator, and wherein the servo electronics component amplifies the feedback signal from the photo detector before delivering the signal to the intensity modulator control port.

8. A system for improving the performance of a gyroscope, comprising:

a means for directing a light beam to an intensity modulation means positioned upstream from a gyroscope resonator;

a means for re-directing at least a portion of the light beam received from the intensity modulation means;

a means for measuring intensity modulation-induced amplitude variation in a light beam;

a means for outputting a signal proportional to intensity modulation-induced amplitude of the re-directed light beam; and

wherein the intensity modulation means, to reduce intensity modulation-induced measurement error, modulates the light beam using the outputted signal as a control input.

9. The system of claim 8, further comprising a means for amplifying the outputted signal before providing the outputted signal to the intensity modulation means.

10. The system of claim 8, wherein the gyroscopic resonator is a component of a resonance fiber-optic gyroscope (RFOG).