Patent ID: 8830479

Claim:
A resonator fiber-optic gyro (RFOG) comprising: one or more light sources configured to produce a reference laser beam having a reference frequency, a first laser beam having a first frequency offset from the reference laser beam, and a second laser beam having a second frequency offset from the reference laser beam; a sensing resonator having a first input coupled to receive the first laser beam and a second input coupled to receive the second laser beam such that the first laser beam propagates through the sensing resonator in a first direction and exits at a first output and the second laser beam propagates through the sensing resonator in a second direction and exits at a second output, wherein the first laser beam and second laser beam are modulated at a modulation frequency; a first optical combiner coupled between a first output of the sensing resonator and a first input of the resonance tracking electronics, the first optical combiner configured to beat the first output of the sensing resonator with the reference laser beam creating a first beat signal; a second optical combiner coupled between a second output of the sensing resonator and a second input of the resonance tracking electronics, the second optical combiner configured to beat the second output of the sensing resonator with the reference laser beam creating a second beat signal; and resonance tracking electronics configured to generate a first control signal that indicates when the first laser beam is off resonance and to generate a second control signal that indicates when the second laser beam is off resonance, wherein the resonance tracking electronics is configured to: demodulate the first beat signal at the first frequency offset to generate first in-phase information and first quadrature information; square the first in-phase information; square the first quadrature information; sum the squared first in-phased information and the squared first quadrature information to generate first R-squared information; demodulate the first R-squared information at the modulation frequency to generate a first discriminant signal; demodulate the second beat signal at the second frequency offset to generate second in-phase information and second quadrature information; square the second in-phase information; square the second quadrature information; sum the squared second in-phased information and the squared second quadrature information to generate a second R-squared information; demodulate the second R-squared information at the modulation frequency to generate a second discriminant signal; and generate the first control signal and the second control signal based on the first discriminant signal and the second discriminant signal.