RESIDUAL INTENSITY MODULATION (RIM) CONTROL LOOP IN A RESONATOR FIBER-OPTIC GYROSCOPE (RFOG)

• US 20100225923A1
• Filed: 10/19/2009
• Published: 09/09/2010
• Est. Priority Date: 03/06/2009
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Qiu, Tiequn, Strandjord, Lee, Sanders, Glen A.
• Granted Patent: US 8,446,589 B2
• Time in Patent Office: Days
• 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:

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

modulating the light beam to reduce intensity modulation-induced measurement error.

2. The method of claim 1, further comprising:

directing the light beam through 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

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

3. The method of claim 2, further comprising amplifying the outputted photo detector signal before providing the outputted signal to the intensity modulator.

4. The method of claim 2, wherein the gyroscopic resonator is a component of a resonance fiber-optic gyroscope (RFOG).

5. An apparatus for improving gyroscope performance comprising a residual intensity modulation servo loop configured to reduce intensity modulation-induced measurement error.

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 an output of a 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, further comprising a servo electronics component, 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 measuring intensity modulation-induced amplitude variation in a light beam; and

a means for modulating the light beam to reduce intensity modulation-induced measurement error.

9. The system of claim 8, further comprising:

a means for directing the light beam through 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 outputting a signal proportional to an amplitude of the re-directed light beam; and

a means for modulating the light beam using the outputted signal as a control input.

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

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