Sagnac phase shift tracking method for fiber-optic gyroscopes

An open-loop fiber-optic gyroscope comprising:

• a light source;
• a fiber-optic ring optically coupled to the light source;
• a detector optically coupled to the fiber-optic ring;
• and
• a processor to determine, based on an output of the detector, a Sagnac phase shift of the open-loop fiber-optic gyroscope, such that the Sagnac phase shift monotone interval of the open-loop fiber-optic gyroscope is not limited to the interval [−π/2 π/2).

A fiber-optic gyroscope comprising:

• a polarizer;
• a fiber-optic ring;
• a first coupler;
• a second coupler;
• a laser light source coupled with the polarizer through the first coupler, the polarizer coupled with the fiber-optic ring through the second coupler;
• a detector;
• a signal processing module;
• a filtering and analog-to-digital conversion module;
• a digital-to-analog conversion module;
• and
• a phase modulator coupled between the fiber-optic ring and the second coupler, a port of the second coupler being coupled with the detector, the detector and the laser light source being positioned at a same side of the first coupler, an output end of the detector being coupled with a control end of the phase modulator through the filtering and analog-to-digital conversion module, the signal processing module and the digital-to-analog conversion module;
• wherein the signal processing module is configured to perform a Sagnac phase shift tracking process that includes:
• determining, for both a current time and a previous time, a value of a primary harmonic demodulated signal and a value of a secondary harmonic demodulated signal from a detector output in the fiber-optic gyroscope;
• and
• determining the Sagnac phase shift of the fiber-optic gyroscope for the current time based on the values of the primary harmonic demodulated signal and the secondary harmonic demodulated signal for both the current time and the previous time.

A fiber-optic gyroscope comprising:

• a polarizer;
• a fiber-optic ring;
• a first coupler;
• a second coupler;
• a laser light source coupled with the polarizer through the first coupler, the polarizer coupled with the fiber-optic ring through a second coupler;
• a detector;
• a signal processing module;
• a filter;
• an analog-to-digital conversion module;
• a primary harmonic wave demodulation module;
• a secondary harmonic demodulation module;
• an oscillator;
• a 90° phase shift and frequency multiplication module;
• and
• a phase modulator coupled between the fiber-optic ring and the second coupler;
• wherein a port of the first coupler is coupled with a detector, the detector and the laser light source are positioned at a same side of the first coupler, an output end of the detector is coupled with an input end of the filter, an output end of the filter is coupled respectively with input ends of the primary harmonic wave demodulation module and the secondary harmonic demodulation module, wherein output ends of the primary harmonic wave demodulation module and the secondary harmonic demodulation module are coupled with the signal processing module through the analog-to-digital conversion module, control ends of the phase modulator and the primary harmonic wave demodulation module are coupled respectively with an output end of the oscillator;
• and a control end of the second harmonic demodulation module is coupled with an output end of the oscillator through the 90° phase shift and frequency multiplication module;
• and wherein the signal processing module is configured to execute a Sagnac phase shift tracking process that includes:
• determining, for both a current time and a previous time, a value of a primary harmonic demodulated signal and a value of a secondary harmonic demodulated signal from a detector output in the fiber-optic gyroscope;
• and
• determining the Sagnac phase shift of the fiber-optic gyroscope for the current time based on the values of the primary harmonic demodulated signal and the secondary harmonic demodulated signal for both the current time and the previous time.