Fiber optic gyroscope dead band error suppression

An interferometric fiber optic gyroscope (IFOG) comprising:

• a fiber optic coil;
• a light source configured to generate a light beam for input into the fiber optic coil;
• a phase modulator to modulate the light beam;
• a photodetector to convert an output light signal from the fiber optic coil into an electrical signal;
• and
• demodulating electronics configured to provide a signal indicative of a rotation rate sensed by the fiber optic coil and to generate a feedback signal for the phase modulator, the control electronics configured to:
• generate a bias modulation value for bias modulation of the input light beam;
• accumulate phase step corresponding to a difference in phase shift between outputs of the fiber optic coil in adjacent cycles of the IFOG to generate a phase step;
• generate a feedback signal for modulating the input light beam, the feedback signal corresponding to a sum of the bias modulation value and the phase step;
• and
• intermittently jump the phase step to suppress dead band, wherein jump the phase step includes:
• during a first cycle of the IFOG:
• demodulate a first cycle output of the fiber optic coil to determine a first cycle rate difference between the first cycle output and a previous output of the fiber optic coil;
• accumulate the first cycle rate difference with a prior raw rate to generate a first cycle raw rate;
• store the first cycle raw rate;
• create a jumped phase step;
• and
• generate a feedback signal for the first cycle from a sum of a bias modulation value and the jumped phase step;
• during a second cycle, the second cycle immediately following the first cycle:
• demodulate a second cycle output of the fiber optic coil to determine a second cycle rate difference between the second cycle output and the first cycle output;
• accumulate the second cycle rate difference with the first cycle raw rate to generate the second cycle raw rate;
• store the second cycle raw rate;
• hold a second cycle phase step at the jumped phase step;
• and
• generate a feedback signal for the second cycle from a sum of a bias modulation value and the second cycle phase step;
• during a third cycle, the third cycle immediately following the second cycle:
• discard a raw rate for the third cycle;
• and
• accumulate the first cycle raw rate with the second cycle phase step to generate a third cycle phase step;
• and
• generate a feedback signal for the third cycle from a sum of a bias modulation value and the third cycle phase step;
• during a fourth cycle, the fourth cycle immediately following the third cycle:
• discard a raw rate for the fourth cycle;
• and
• accumulate the second cycle raw rate with the third cycle phase step to generate a fourth cycle phase step;
• and
• generate a feedback signal for the fourth cycle from a sum of a bias modulation value and the fourth cycle phase step.

A method of jumping a phase step to suppress dead band during modulation of an input light beam of a fiber optic coil of an interferometric fiber optic gyroscope (IFOG), the method comprising:

• during a first cycle of the IFOG:
• demodulating a first cycle output of the fiber optic coil to determine a first cycle rate difference between the first cycle output and a previous output of the fiber optic coil;
• accumulating the first cycle rate difference with a prior raw rate to generate a first cycle raw rate;
• storing the first cycle raw rate;
• creating a jumped phase step;
• generating a first cycle bias modulation value for bias modulation of the input light beam;
• and
• generating a first cycle feedback signal from a sum of the first cycle bias modulation value and the jumped phase step;
• during a second cycle, the second cycle immediately following the first cycle:
• demodulating a second cycle output of the fiber optic coil to determine a second cycle rate difference between the second cycle output and the first cycle output of the fiber optic coil;
• accumulating the second cycle rate difference with the first cycle raw rate to generate a second cycle raw rate;
• storing second cycle raw rate;
• holding a second cycle phase step at the jumped phase step;
• generating a second cycle bias modulation value for bias modulation of the input light beam;
• generating a second cycle feedback signal from a sum of the second cycle bias modulation value and the second cycle phase step;
• during a third cycle, the third cycle immediately following the second cycle:
• discarding a raw rate for the third cycle;
• and
• accumulating the first cycle raw rate with the second cycle phase step to generate a third cycle phase step;
• and
• generating a third cycle bias modulation value for bias modulation of the input light beam;
• generating a third cycle feedback signal from a sum of the third cycle bias modulation value and the third cycle phase step;
• during a fourth cycle, the fourth cycle immediately following the third cycle:
• discarding a raw rate for the fourth cycle;
• and
• accumulating the second cycle raw rate with the third cycle phase step to generate a fourth cycle phase step;
• generating a third cycle bias modulation value for bias modulation of the input light beam;
• and
• generating a fourth cycle feedback signal from a sum of the fourth cycle bias modulation value and the fourth cycle phase step.