Patent ID: 6445455
Filing Date: 2002-09-03
Classification: G01C

Abstract:
A phase and intensity modulated IFOG comprising:a light source responsive to an intensity modulation signal for providing an intensity modulated light signal; a Sagnac interferometer having a fiber optic coil having a first and a second end, said fiber optic coil receiving and circulating a cw (clockwise) and a ccw (counter clockwise) beam, the coil having a sensitive axis, the Sagnac interferometer being responsive to the intensity modulated light signal at a first input port, and a phase modulation signal at a phase modulation input terminal, for outputting a non-reciprocal interference signal; a PSD detector system responsive to said non-reciprocal interference signal for providing a demodulated bias signal; an intensity signal generator having an output providing said intensity modulation signal, a phase signal generator providing said phase modulation signal to said phase modulation input terminal, the intensity signal generator and the phase signal generator having a common frequency, the phase difference &thgr; between the phase modulation signal and the intensity modulation signal being adjustable in response to at least a first computer control signal, a computer having a digitizing sampler coupled to receive and digitize successive sample values of the demodulated bias signal, the computer executing a program characterized to adjust at least said first computer control signal to adjust the phase difference &thgr; between the intensity modulation signal and the phase modulation signal to drive the amplitude of the sample values of the demodulated bias signals to a minimum, the computer program successively calculating and outputting an input rotation rate to the Sagnac sensitive axis as a function of the phase angle between the intensity modulation signal and the phase modulation signal.