The invention discloses a resonant type
fiber-optic gyro coherent
demodulation system and method based on interference of externally added light beams. The
system includes a
laser, a first polarization-maintaining coupler, a Y-
branch phase modulator, a phase modulator, an
optical fiber resonant cavity, a second polarization-maintaining coupler, a third polarization-maintaining coupler, a first photoelectric
detector, a first band-pass filter, a local carrier generation module, a first local
carrier phase shift module, a first 90-degree
phase shift module, a first multiplier, a second multiplier, a first low-pass filter, a second low-pass filter, a third multiplier, a third low-pass filter, a first digital phase-lock
amplifier, a PI
servo loop, a fourth polarization-maintaining coupler, a second photoelectric
detector, a second band-pass filter, a second local
carrier phase shift module, a second 90-degree
phase shift module, a fourth multiplier, a fifth multiplier, a fourth low-pass filter, a fifth low-pass filter, a sixth multiplier, a sixth low-pass filter, and a second digital phase-lock
amplifier. By local
recovery of a carrier with high
signal-to-
noise ratio, the
signal-to-
noise ratio of a demodulated
signal is improved, the influence of
laser frequency noise is reduced, and the resonant type
fiber-optic gyro coherent
demodulation system and method have important scientific significance and application value.