Bias-instability reduction in fiber optic gyroscopes

1. A computer-implementable method of reducing bias instability in a fiber optic gyroscope, the method comprising the steps of:

receiving with a computer a first data set enabling the computer to generate a model of the gyroscope, including a light source, a photodetector, and a plurality of optical components and fiber sections coupling the light source to the photodetector, and a light signal to be propagated from the light source to the photodetector, the light signal having an associated wavelength spectrum;

for each said wavelength of the spectrum, calculating the relative lightwave intensity reaching the photodetector;

determining, from the calculated relative lightwave intensities, a signal-wave intensity and a spurious-wave intensity;

determining, from the signal-wave intensity, a scale factor;

integrating the spurious-wave intensity over the wavelength spectrum of the light source to obtain a total spurious-wave intensity;

determining a rate bias error based on the total spurious-wave intensity and the scale factor; and

displaying the rate bias error.

2. The method of claim 1 wherein receiving the first data set comprises receiving wavelength dependent Jones-matrix data to represent at least one of phase delays, polarization-dependent losses and cross-couplings associated with the gyroscope.

3. The method of claim 1 , further comprising receiving with the computer a second data set enabling the computer to modify the gyroscope model and decrease the rate bias error.

4. The method of claim 3 wherein the gyroscope-model modification comprises changing the beat length of at least one of the fiber sections.

5. The method of claim 3 wherein:

the gyroscope model further includes a coupler; and

the gyroscope-model modification comprises reducing a polarization-dependent splitting ratio of said coupler.

6. The method of claim 3 wherein the gyroscope-model modification comprises reducing cross-coupling of at least one splice associated with a pair of the fiber sections.

7. The method of claim 3 wherein:

the gyroscope model further includes an integrated optical circuit (IOC); and

the gyroscope-model modification comprises increasing a polarization extinction ratio of said IOC.

8. The method of claim 3 wherein:

the gyroscope model further includes a sensing loop; and

the gyroscope-model modification comprises reducing at least one of differential group delay and birefringence of said sensing loop.

9. The method of claim 1 , further comprising:

applying a temperature ramp to at least one modeled gyroscope component;

calculating a peak-to-peak bias fluctuation amplitude associated with the modeled component under the temperature ramp; and

plotting the amplitude to determine an optimal design for the modeled component.

10. The method of claim 3 wherein the gyroscope-model modification comprises changing the length of at least one of the fiber sections.

11. A computer-readable medium including executable instructions that, when executed by a processing device, enable the processing device to perform the steps of:

receiving data enabling the processing device to generate a model of a fiber optic gyroscope, including a light source, a photodetector, and a plurality of optical components and fiber sections coupling the light source to the photodetector, and a light signal to be propagated from the light source to the photodetector, the light signal having an associated wavelength spectrum;

for each said wavelength of the spectrum, calculating the relative lightwave intensity reaching the photodetector;

determining, from the calculated relative lightwave intensities, a signal-wave intensity and a spurious-wave intensity;

determining, from the signal-wave intensity, a scale factor;

integrating the spurious-wave intensity over the wavelength spectrum of the light source to obtain a total spurious-wave intensity;

determining a rate bias error based on the total spurious-wave intensity and the scale factor; and

displaying the rate bias error.

12. The medium of claim 11 wherein the instructions further enable the processing device to perform the step of receiving the first data set comprises receiving Jones-matrix data to represent at least one of phase delays, polarization-dependent losses and cross-couplings associated with the gyroscope.

13. The medium of claim 11 , wherein the instructions further enable the processing device to perform the step of receiving with the processing device a second data set enabling the processing device to modify the gyroscope model and decrease the rate bias error.

14. The medium of claim 13 wherein the gyroscope-model modification comprises changing the beat length of at least one of the fiber sections.

15. The medium of claim 13 wherein:

the gyroscope model further includes a coupler; and

the gyroscope-model modification comprises reducing a polarization-dependent splitting ratio of said coupler.

16. The medium of claim 13 wherein:

the gyroscope model further includes an integrated optical circuit (IOC); and

the gyroscope-model modification comprises increasing a polarization extinction ratio of said IOC.

17. The medium of claim 13 wherein:

the gyroscope model further includes a sensing loop; and

the gyroscope-model modification comprises reducing at least one of differential group delay and birefringence of said sensing loop.

18. A method of reducing bias instability in a fiber optic gyroscope including an optical circuit comprising a plurality of fiber sections, the method comprising the steps of:

applying a temperature ramp to at least one portion of the optical circuit;

measuring at least one bias fluctuation associated with the temperature-ramped at least one portion;

determining at least one temperature period of said at least one bias fluctuation;

identifying at least one cross-coupling point associated with at least one pair of the fiber sections and corresponding to the temperature period; and

modifying at least one fiber section of the at least one fiber-section pair.

19. The method of claim 18 wherein modifying at least one fiber section comprises modifying the fiber-section type.

20. The method of claim 18 wherein modifying at least one fiber section comprises modifying the length of the fiber-section.