SECONDARY-PHASE-MODULATION METHOD FOR OPEN-LOOP FIBEROPTIC GYROSCOPES

A proposed method of secondary phase modulation for open-loop fiber-op tic gyroscopes is examined in general terms. To detect the rotation ra te of a system through a beat-frequency channel, we employ linearly co mbined signals with different frequencies for the optical phase modula tion. We find that the proper combinations of the modulation frequenci es can optimize the sensitivity of gyroscopes. With this method we can employ a high-frequency band for optical phase modulations while keep ing relative a lower-frequency band of the detection channel. The theo retically derived result is experimentally confirmed by using a lithiu m-niobate (LiNbO3) optical phase modulator. We also discuss the combin ation setup with an optical integrated-circuit device and digital sign al processing. (C) 1996 Optical Society of America