Symmetric three-laser resonator fiber optic gyroscope

Patent metadata

Field	Value
Publication number	US-9587945-B2
Application number	US-201414312009-A
Country	US
Kind code	B2
Filing date	Jun 23, 2014
Priority date	Jun 23, 2014
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

A resonator fiber optic gyroscope comprises a master laser that emits a reference optical signal, a first slave laser that emits a clockwise optical signal, and a second slave laser that emits a counter-clockwise optical signal. A resonator ring cavity in optical communication with the first slave laser and second slave laser is configured to receive the optical signals from the slave lasers without receiving the reference optical signal. A reflected optical signal from the cavity is directed to a feedback laser stabilization loop for the master laser that includes a common modulation frequency scheme. A frequency of the optical signal from the master laser is indirectly locked onto a resonance frequency of the cavity with a fixed frequency offset, which is determined by a relative frequency between the optical signal of the first slave laser or the second slave laser, and the optical signal of the master laser.

First claim

What is claimed is:

1. A resonator fiber optic gyroscope (RFOG), comprising:
a master laser configured to emit a reference optical signal;
a first slave laser configured to emit a clockwise (CW) optical signal, the first slave laser operatively coupled to the master laser and responsive to the reference optical signal through a CW optical phase lock loop;
a second slave laser configured to emit a counter-clockwise (CCW) optical signal, the second slave laser operatively coupled to the master laser and responsive to the reference optical signal through a CCW optical phase lock loop; and
an optical resonator ring cavity in optical communication with the first slave laser and the second slave laser, the resonator ring cavity configured to receive the CW optical signal and the CCW optical signal, the resonator ring cavity not optically connected to the master laser such that the resonator ring cavity does not receive the reference optical signal;
a feedback laser stabilization loop for the master laser that includes a common modulation frequency scheme, wherein a reflected optical signal from the resonator ring cavity is directed to the feedback laser stabilization loop;
wherein a frequency of the reference optical signal from the master laser is indirectly locked onto a resonance frequency of the resonator ring cavity with a fixed frequency offset, which is determined by a relative frequency between the optical signal of the first slave laser or the second slave laser, and the reference optical signal of the master laser.

2. The RFOG of claim 1 , further comprising a Pound-Drever-Hall (PDH) servo electronics module configured to demodulate the reflected optical signal using a sideband heterodyne modulation frequency to provide a resonance tracking error signal that indicates when a frequency of the CW optical signal or the CCW optical signal has deviated from a resonance frequency of the resonator ring cavity.

3. The RFOG of claim 2 , wherein the PDH servo electronics module receives a set point control signal comprising a common modulation frequency from a sine wave generator.

4. The RFOG of claim 3 , wherein an output signal from the PDH servo electronics module is sent to an input of the master laser as part of the feedback laser stabilization loop.

5. The RFOG of claim 1 , wherein the reflected optical signal is a CW reflection signal from the first slave laser.

6. The RFOG of claim 1 , wherein the reflected optical signal is a CCW reflection signal from the second slave laser.

7. The RFOG of claim 1 , wherein a portion of the CW optical signal and a portion of the reference optical signal are combined in the CW optical phase lock loop for the first slave laser to provide tuning of a relative optical frequency between the CW optical signal and the reference optical signal, wherein the CW optical phase lock loop is part of the feedback laser stabilization loop for the master laser.

8. The RFOG of claim 1 , wherein a portion of the CCW optical signal and a portion of the reference optical signal are combined in the CCW optical phase lock loop for the second slave laser to provide tuning of a relative optical frequency between the CCW optical signal and the reference optical signal, wherein the CCW optical phase lock loop is part of the feedback laser stabilization loop for the master laser.

9. The RFOG of claim 2 , wherein the resonator ring cavity is operatively coupled to a CW resonance tracking electronics module, and a CCW resonance tracking electronics module.

10. The RFOG of claim 9 , wherein a digital signal is output from the CW resonance tracking electronics module and sent to a first direct digital synthesizer as part of a CW resonance tracking loop.

11. The RFOG of claim 10 , wherein a digital signal is output from the CCW resonance tracking electronics module and sent to a second direct digital synthesizer as part of a CCW resonance tracking loop.

12. The RFOG of claim 10 , wherein the first direct digital synthesizer receives a common modulation frequency that is digitally generated.

13. The RFOG of claim 11 , wherein the second direct digital synthesizer receives a common modulation frequency that is digitally generated.

14. The RFOG of claim 9 , wherein an output signal from the PDH servo electronics module is transmitted to a modulation stripper in a PDH control feedback loop.

15. The RFOG of claim 14 , wherein the modulation stripper receives a reference frequency and transmits a stripper signal to a summer.

16. The RFOG of claim 15 , wherein the summer is configured to:
receive an analog signal output from the CW resonance tracking electronics module or the CCW resonance tracking electronics module;
combine the analog signal with the stripper signal; and
output a setpoint control signal to the PDH servo electronics module.

17. The RFOG of claim 16 , wherein the output signal from the PDH servo electronics module is also sent to an input of the master laser as part of the feedback laser stabilization loop for the master laser.

18. A resonator fiber optic gyroscope (RFOG), comprising:
a master laser that emits a reference optical signal;
a first slave laser that emits a clockwise (CW) optical signal, the first slave laser operatively coupled to the master laser and responsive to the reference optical signal through a CW optical phase lock loop;
a second slave laser that emits a counter-clockwise (CCW) optical signal, the second slave laser operatively coupled to the master laser and responsive to the reference optical signal through a CCW optical phase lock loop;
an optical resonator ring cavity in optical communication with the first slave laser and the second slave laser, the resonator ring cavity configured to receive the CW optical signal and the CCW optical signal without receiving the reference optical signal;
a piezoelectric phase modulator operatively coupled to the resonator ring cavity and configured to provide a common cavity modulation for the resonator ring cavity;
a CW resonance tracking electronics module operatively coupled to the resonator ring cavity;
a CCW resonance tracking electronics module operatively coupled to the resonator ring cavity;
a photodetector that converts a reflected optical signal from the resonator ring cavity to an electrical signal; and
a feedback laser stabilization loop for the master laser, the feedback laser stabilization loop comprising:
a Pound-Drever-Hall (PDH) servo electronics module configured to receive the electrical signal from the photodetector;
a modulation stripper responsive to an output signal from the PDH servo electronics module in a PDH control feedback loop;
a summer configured to:
receive a stripper signal from the modulation stripper;
receive an analog signal output from the CW resonance tracking electronics module or the CCW resonance tracking electronics module as part of a PDH error correction loop;
combine the stripper signal with the analog signal; and
output a setpoint control signal to the PDH servo electronics module;

wherein the output signal from the PDH servo electronics module is transmitted to an input of the master laser;

wherein a frequency of the reference optical signal from the master laser is indirectly locked onto a resonance frequency of the resonator ring cavity with a fixed frequency offset, which is determined by a relative frequency between the optical signal of the first slave laser or the second slave laser, and the reference optical signal of the master laser.

19. The RFOG of claim 18 , wherein the ref

Assignees

• Honeywell Int Inc

Inventors

• Strandjord Lee K
• Sanders Glen A
• Qiu Tiequn

Classifications

• G01C19/727 Primary

  using a passive ring resonator · CPC title

• G01C19/721

  Details, e.g. optical or electronical details · CPC title