Electronic phase-tracking open-loop fiber optic gyroscope
First Claim
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1. An electronic phase-tracking open-loop fiber optic gyroscope apparatus, comprising:
- an optical gyroscope responsive to a modulation signal for developing a phase-shifted optical signal output;
a modulator signal source for producing the modulation signal;
phase shift means responsive to the modulation signal for producing a reference modulation signal;
summer means responsive to the reference modulation signal and to a feedback signal for producing a reference signal;
signal processing means responsive to the optical signal output and the reference signal for producing a composite signal;
means for filtering the composite signal to produce an error signal; and
an integrator responsive to the error signal for producing and applying the feedback signal to said summer means and producing an electrical system output signal related to the phase-shift of the optical signal output.
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Abstract
A simplified signal processing technique for the open-loop fiber optic gyroscope is described which is based on the electronic closed-loop `phase-shift nulling` concept. The system provides a linear output from an open-loop gyroscope configuration over a ±2 pi radian range in Sagnac phase shift with good linearity and relatively low noise and drift. An alternative embodiment is disclosed utilizing, for example, a Mach-Zehnder interferometer for mixing the signals.
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Citations
13 Claims
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1. An electronic phase-tracking open-loop fiber optic gyroscope apparatus, comprising:
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an optical gyroscope responsive to a modulation signal for developing a phase-shifted optical signal output; a modulator signal source for producing the modulation signal; phase shift means responsive to the modulation signal for producing a reference modulation signal; summer means responsive to the reference modulation signal and to a feedback signal for producing a reference signal; signal processing means responsive to the optical signal output and the reference signal for producing a composite signal; means for filtering the composite signal to produce an error signal; and an integrator responsive to the error signal for producing and applying the feedback signal to said summer means and producing an electrical system output signal related to the phase-shift of the optical signal output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A fiber optic gyroscope apparatus comprising:
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an open loop fiber optic gyroscope including a phase modulator and having a phase-shifted optical signal output; and a closed loop phase tracking circuit comprising; a modulator signal source for producing and applying a modulation signal to said phase modulator of said open loop fiber optic gyroscope; means responsive to the modulation signal and to a feedback signal for developing a reference signal related to the modulation signal; and means for mixing the reference signal and the phase-shifted optical signal output to produce an electrical signal output related to the phase shift of the phase-shifted optical signal output and for feeding back to said developing means a portion of the electrical signal output as the feedback signal.
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11. A fiber optic gyroscope system comprising:
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an open loop fiber optic gyroscope, including a phase modulator, for generating a Sagnac phase-shifted optical signal; a closed loop phase tracking circuit comprising; a modulator signal source for producing and applying a modulation signal to said phase modulator of said open loop fiber optic gyroscope;
.means responsive to the modulation signal and to an electrical output signal for generating a phase-modulated reference sine function signal; and means responsive to said Sagnac phase-shifted optical signal and said phase-modulated reference sine function signal for generating the electrical output signal.
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12. A method of generating an electrical output signal from a fiber optic gyroscope apparatus, said method comprising the steps of:
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generating a signal having a Sagnac phase-shift in an open loop fiber optic portion of the fiber optic gyroscope apparatus; developing a phase-shifted modulator signal in a closed loop phase tracking circuit portion of the fiber optic gyroscope apparatus; combining the phase-shifted modulator signal with a feedback signal in the closed loop phase tracking circuit portion of the fiber optic gyroscope apparatus to generate a reference signal; utilizing the reference signal to generate a phase modulated reference sine function signal in the closed loop phase tracking circuit portion of the fiber optic gyroscope apparatus; mixing in the closed loop phase tracking circuit portion of the fiber optic gyroscope apparatus the signal having the Sagnac phase-shift and the phase modulated reference sine function signal to produce an electrical output signal related to the Sagnac phase-shift; and feeding back a portion of the the electrical output signal related to the sagnac phase-shift as the feedback signal. - View Dependent Claims (13)
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Specification