Method and apparatus for monitoring angle random walk of a fiber optic gyroscope

1. A system for determining a level of angle random walk (ARW) associated with a fiber optic gyroscope (FOG), the system comprising:

first and second photodiodes, said first photodiode configured to receive a first light signal from a light source associated with the FOG, said second photodiode configured to receive a second light signal from a fiber optic coil associated with the FOG;

at least one analog-to-digital converter (ADC) operable to convert the first and second light signals into corresponding respective first and second digital signals;

a digital relative-intensity-noise (RIN) subtraction element configured to receive said first and second digital signals and output a third signal based on said first and second digital signals; and

an electronic device in signal communication with said subtraction element, said electronic device configured to determine a first noise level associated with the third signal, and determine the ARW level from said first noise level.

2. The system of claim 1 wherein said electronic device comprises a field-programmable gate array.

3. The system of claim 1 wherein said electronic device is further coupled to said first ADC and is configured to determine a second noise level associated with the first digital signal, and determine the ARW level from said second noise level.

4. The system of claim 1 wherein said electronic device is further coupled to said second ADC and is configured to determine a second noise level associated with the second digital signal, and determine the ARW level from said second noise level.

5. The system of claim 1 wherein said third signal comprises a DRS signal.

6. The system of claim 1 wherein said electronic device is configured to measure the first noise level within a one-half bias-modulation cycle of the FOG.

7. The system of claim 1 , wherein determining said ARW level includes analyzing a plurality of sub-bands within an encompassing noise monitoring band of the third signal.

8. A system for determining a level of angle random walk (ARW) associated with a fiber optic gyroscope (FOG), the system comprising:

first and second photodiodes, said first photodiode configured to receive a first light signal from a light source associated with the FOG, said second photodiode configured to receive a second light signal from a fiber optic coil associated with the FOG;

at least one analog-to-digital converter (ADC) operable to convert the first and second light signals into corresponding respective first and second digital signals;

a digital relative-intensity-noise (RIN) subtraction element configured to receive said first and second digital signals and output a third signal based on said first and second digital signals;

a rate demodulator element configured to receive the third signal and output a fourth signal based on the third signal;

a rate accumulator element configured to receive the fourth signal and output a fifth signal based on the fourth signal; and

an electronic device in signal communication with said rate accumulator element, said electronic device configured to determine a first noise level associated with the fifth signal, and determine the ARW level from said first noise level.

9. The system of claim 8 wherein said electronic device comprises a field-programmable gate array.

10. The system of claim 8 wherein said electronic device comprises a low-pass filter.

11. The system of claim 10 wherein:

said electronic device is further configured to downsample a portion of the fifth signal filtered by the low-pass filter; and

the ARW level is determined from said downsampled portion.

12. The system of claim 8 , wherein determining said ARW level includes analyzing a plurality of sub-bands within an overall noise monitoring band of the third signal.

13. A method of determining a level of angle random walk (ARW) associated with a fiber optic gyroscope (FOG), comprising the steps of:

receiving a first light signal from a fiber optic coil associated with the FOG;

converting the first light signal into a corresponding first digital signal;

generating a second digital signal based on said first digital signal;

determining first and second noise levels respectively associated with the first and second digital signals; and

determining the ARW level from at least one of said first and second noise levels.

14. The method of claim 13 , further comprising:

receiving a second light signal from a light source associated with the FOG;

converting the second light signal into a corresponding third digital signal;

determining a third noise level associated with the third digital signal; and

determining the ARW level from said third noise level.

15. The method of claim 13 , further comprising:

receiving a second light signal from a light source associated with the FOG;

converting the second light signal into a corresponding third digital signal;

generating a fourth digital signal based on said third digital signal;

determining a third noise level associated with the fourth digital signal; and

determining the ARW level from said third noise level.

16. The method of claim 15 wherein said fourth digital signal comprises a DRS signal.

17. The method of claim 13 wherein determining a first noise level comprises measuring the first noise level within a one-half bias-modulation cycle of the FOG.

18. The method of claim 13 , wherein determining said ARW level includes analyzing a plurality of sub-bands within an overall noise monitoring band of the first digital signal.