A method comprising: providing a resonator fiber optic gyroscope, RFOG, that comprises an optical resonator in optical communication with a first light source that emits a first optical signal at a first power level in a clockwise, CW, direction, and a second light source that emits a second optical signal at a second power level in a counterclockwise, CCW, direction; adding a common intensity modulation to the first optical signal emitted from the first light source, to adjust the first power level and produce an intensity modulated CW signal; adding the same common intensity modulation to the second optical signal emitted from the second light source, to adjust the second power level and produce an intensity modulated CCW signal; providing means to equalize a modulation amplitude between the first and second optical signals; introducing the intensity modulated CW signal into the optical resonator, such that the intensity modulated CW signal propagates in a CW direction in the optical resonator; introducing the intensity modulated CCW signal into the optical resonator, such that the intensity modulated CCW signal propagates in a CCW direction in the optical resonator; detecting the intensity modulated CW and CCW signals that are output from the optical resonator; outputting a first electrical signal based on the detected intensity modulated CCW signal, and outputting a second electrical signal based on the detected intensity modulated CW signal; determining a rotation rate signal based on the first and second electrical signals, wherein the rotation rate signal comprises a sine wave at a common intensity modulation frequency; adjusting a power level ratio between the first and second power levels of the first and second optical signals based on the sine wave at the common intensity modulation frequency, to determine a modified power level ratio value where the sine wave in the rotation rate signal is reduced or eliminated, such that a Kerr effect bias instability due to an asymmetrical loss distribution in the RFOG is reduced or eliminated; and maintaining the modified power level ratio value in the RFOG such that the Kerr effect bias instability is reduced or eliminated. providing a resonator fiber optic gyroscope, RFOG, that comprises an optical resonator in optical communication with a first light source that emits a first optical signal at a first power level in a clockwise, CW, direction, and a second light source that emits a second optical signal at a second power level in a counterclockwise, CCW, direction; adding a common intensity modulation to the first optical signal emitted from the first light source, to adjust the first power level and produce an intensity modulated CW signal; adding the same common intensity modulation to the second optical signal emitted from the second light source, to adjust the second power level and produce an intensity modulated CCW signal; providing means to equalize a modulation amplitude between the first and second optical signals; introducing the intensity modulated CW signal into the optical resonator, such that the intensity modulated CW signal propagates in a CW direction in the optical resonator; introducing the intensity modulated CCW signal into the optical resonator, such that the intensity modulated CCW signal propagates in a CCW direction in the optical resonator; detecting the intensity modulated CW and CCW signals that are output from the optical resonator; outputting a first electrical signal based on the detected intensity modulated CCW signal, and outputting a second electrical signal based on the detected intensity modulated CW signal; determining a rotation rate signal based on the first and second electrical signals, wherein the rotation rate signal comprises a sine wave at a common intensity modulation frequency; adjusting a power level ratio between the first and second power levels of the first and second optical signals based on the sine wave at the common intensity modulation frequency, to determine a modified power level ratio value where the sine wave in the rotation rate signal is reduced or eliminated, such that a Kerr effect bias instability due to an asymmetrical loss distribution in the RFOG is reduced or eliminated; and maintaining the modified power level ratio value in the RFOG such that the Kerr effect bias instability is reduced or eliminated.