The output signal of optical fiber gyroscope strap-down inertial navigation system（ SINS） contains high frequency random noise as the system is sensitive to its environment

thus yielding poor long-term narigation precision. To further improve navigation precision

more effective filtering technology is needed to process output noise of device. Traditional digital filter utilize the fixed cut-off frequency which will have a deviation to its real value. In order to eliminate high frequency noise of devices effectively

a filter design method which based on HMM / KF is proposed

and the adaptive digital filter designed by this method are utilized to process original output signal of optical fiber gyro

so high frequency noise of gyro is significantly eliminated.