Resonator fiber optic gyroscope without frequency overlap in sideband-heterodyne-detection modulations

A method to lock a clockwise (CW) input light and a counter-clockwise (CCW) input light to suppress carrier frequencies and implement sideband-heterodyne-detection modulations in a resonator fiber optic gyroscope, the method comprising:

• applying a first phase modulation with frequency of (n+0.5) times a free spectral range (FSR) to a CW input light, where n is zero or a positive integer, wherein the first phase modulation amplitude is set to suppresses the carrier power of the CW input light;
• applying a second phase modulation with frequency of (m+0.5) times the FSR to CCW input light, where m is zero or a positive integer and is different from n, wherein the second phase modulation amplitude is set to suppresses the carrier power of the CCW input light, and wherein n and m are selected to avoid overlap of major sidebands of the CW input light and the CCW input light;
• and
• applying a common modulation to the CW input light and the CCW input light.

The method of 11, further comprising:

• coupling the CW input light modulated with the first phase modulation into a fiber coil in the CW direction at a first coupler;
• and
• coupling the CCW input light modulated with the second phase modulation into the fiber coil in the CCW direction at a second coupler;
• wherein applying the common modulation to the CW input light and the CCW input light comprises:
• providing a common periodic modulation signal to a piezo-electric transducer from a common modulation signal generator.

A system for detecting a rotation rate of a gyroscope comprising:

• means for applying a first phase modulation to clockwise (CW) input light with a first phase modulation amplitude set to suppresses carrier power of the CW input light and with a first frequency of (n+0.5) times a free spectral range (FSR), where n is zero or a positive integer;
• means for applying a second phase modulation to counter-clockwise (CCW) input light with a second phase modulation amplitude set to suppresses carrier power of the CCW input light and with a second frequency of (m+0.5) times the FSR, where m is zero or a positive integer and is different from n, and where the values of m and n are selected to avoid overlap of major sidebands of the CW input light and the CCW input light;
• means for applying a common modulation to the CW input light and the CCW input light;
• means for double demodulating first signals;
• means for double demodulating second signals;
• and
• means for determining the rotation rate based on a frequency difference between a first carrier frequency and a second carrier frequency.