Kerr effect compensation by optical power balancing in interferometric fiber optic gyroscopes

An interferometric fiber optic gyroscope comprising:

• light source means for emitting a first light beam;
• splitting means, proximate to said light source means, for splitting a first light beam into second and third light beams;
• optical fiber sensing loop means, connected to said splitting means, wherein the second light beam propagates through said optical fiber sensing loop means in a first direction and the third light beam propagates in said optical fiber sensing loop means in a second direction, such that the second and third beams counter-rotate in said optical fiber sensing loop means;
• first modulation means, connected to said optical fiber sensing loop means, for phase modulating the third light beam when entering said optical fiber sensing loop means, according to a first frequency;
• detection means, connected to said splitting means, for receiving at least portions of second and third light beams after exiting said optical fiber sensing loop means;
• phase signal demodulation means, connected to said detection means, for receiving electrical signals representing second and third light beams as detected by said detection means, and for demodulating the electrical signals into phase signals that represent phase differences which exist between second and third light beams, according to the first frequency, wherein the phase differences between second and third light beams are indications of rotation of said optical fiber sensing loop means;
• second modulation means, proximate to said light source means, for intensity modulating the first light beam according to a second frequency;
• third modulation means, connected to said optical fiber sensing loop means, for intensity modulating the second light beam when entering said optical fiber sensing loop means;
• intensity signal demodulation means, connected to said phase signal demodulation means, for demodulating signals from said phase signal demodulation means, according to the second frequency, wherein said intensity signal demodulation means outputs signals indicating intensity differences between second and third light beams;
• and
• optical power balancing servo electronic means, connected to said intensity signal demodulation means and to said third modulation means, for processing signals indicating intensity differences between second and third light beams and outputting optical balancing signals to said third modulation means to affect the intensity of the second light beam so as to null-out the intensity differences between the second and third light beams.

An interferometric fiber optic gyroscope comprising:

• light source means for emitting a first light beam;
• first modulation means, proximate to said light source means, for intensity modulating the first light beam according to a first frequency;
• splitting means, connected to said first modulation means, for splitting a modulated first light beam into second and third light beams;
• optical fiber sensing loop means, connected to said splitting means, wherein the second light beam propagates through said optical fiber sensing loop means in a first direction and the third light beam propagates in said optical fiber sensing loop means in a second direction, such that the second and third beams counter-rotate in said optical fiber sensing loop means;
• second modulation means, connected to said optical fiber sensing loop means, for intensity modulating the second light beam when entering said optical fiber sensing loop means;
• third modulation means, connected to said optical fiber sensing loop means, for phase modulating the third light beam when entering said optical fiber sensing loop means, according to a second frequency;
• detection means, connected to said splitting means, for receiving at least portions of second and third light beams after exiting said optical fiber sensing loop means;
• phase signal demodulation means, connected to said detection means, for receiving electrical signals representing second and third light beams as detected by said detection means, and for demodulating the electrical signals into phase signals that represent phase differences which exist between second and third light beams, according to the second frequency;
• phase signal servo electronic means, connected to said phase signal demodulation means and to third modulation means, for receiving the phase signals and outputting phase modulation signals which go to said third modulation means, wherein the phase modulation signals have a sufficient magnitude to modulate the second light beam so as to bring the second light beam in phase with the third light beam, the amount of magnitude of the phase modulation signals being an indication of a rotation rate of said optical fiber sensing loop means;
• intensity signal demodulation means, connected to said phase signal demodulation means, for demodulating phase signals from said phase signal demodulation means, according to the first frequency, wherein said intensity signal demodulation means outputs signals indicating intensity differences between second and third light beams;
• and
• optical power balancing servo electronic means, connected to said intensity signal demodulation means and to said second modulation means, for processing signals indicating intensity differences between second and third light beams and outputting optical balancing signals to said second modulation means to affect the intensity of the second light beam so as to null-out the intensity differences between the second and third light beams.