High-sensitivity measurement of angular velocity based on an optoelectronic oscillator with an intra-loop Sagnac interferometer

A novel scheme for angular velocity measurement is proposed and demonstrated by using an optoelectronic oscillator (OEO) incorporating a Sagnac interferometer. In the OEO resonant cavity, the optical carrier (OC) and the first-order sidebands propagate in opposite directions in the Sagnac loop. Thus, the rotation-induced Sagnac phase difference between the OC and first-order sidebands will produce an oscillating frequency shift of the OEO which is proportional to the rotation angular velocity. Then a high-sensitivity angular velocity measurement is realized by monitoring the oscillating microwave frequency. The system is free from the lock-in problem, and the sensitivity scale is measured to be 51.8 kHz/(rad/s) which is equivalent to a minimally detectable angular velocity of 3.98°/h with a frequency shift of 1 Hz.