Patent ID: 7372574

Claim:
A resonator gyro comprising: a first light source configured to produce a first input light having a first frequency; a second light source configured to produce a second input light having a second frequency; a resonator coupled to said first and second light sources, said resonator having first and second counter-propagating directions and comprising an optical fiber coil having a hollow core, said resonator configured to: circulate a first circulating light through said hollow core in said first counter-propagating direction, said first circulating light based on a portion of said first input light; and circulate a second circulating light through said hollow core in a second counter-propagating direction, said second circulating light based on a portion of said second input light; a resonance detection circuit coupled to said resonator and comprising: a first photodetector configured to sample light from said first circulating light; a second photodetector configured to sample light from said second circulating light; a first resonance detection circuit coupled to said first photodetector and configured to detect a resonance center of said first counter-propagating direction; and a second resonance detection circuit coupled to said second photodetector and configured to detect a resonance center of said second counter-propagating direction; a controller coupled to said resonance detection circuit and said first and second light sources, said controller comprising: a first servo having an input coupled to said first resonance detection circuit and having an output coupled to said first light source; and a second servo having an input coupled to said second resonance detection circuit and having an output coupled to said second light source; wherein said controller is configured to: tune said first frequency to said resonance frequency of said first counter-propagating direction; and tune said second frequency to said resonance frequency of said second counter-propagating direction, a difference between said resonance frequencies of said first and second counter-propagating directions proportional to a rotational rate of the resonator gyro; wherein said first input light has a first modulation frequency and said second input light has a second modulation frequency, and wherein the resonator gyro further comprises: a first tracking loop based on said first light source, said resonator, said first photodetector, said first resonance detection circuit, and said first servo, said first tracking loop having a first unity gain frequency, said first modulation frequency at least four times greater than said first unity gain frequency; and a second tracking loop based on said second light source, said resonator, said second photodetector, said second resonance detection circuit, and said second servo, said second tracking loop having a second unity gain frequency, said second modulation frequency at least four times greater than said second unity gain frequency.