Resonator fiber optic gyro employing a semiconductor laser

Abstract

Resonator fiber optic gyro (RFOG) based on the Sagnac effect has the potential to achieve the inertial navigation system requirement with a short sensing coil. Semiconductor laser is one of the key elements for integration and miniaturization of the RFOG. In this paper, an RFOG employing a semiconductor laser is demonstrated. The model of the laser frequency noise induced error in the RFOG is described. To attenuate the laser frequency noise induced error, active frequency stabilization is applied. An online laser frequency noise observation is built, as a powerful optimum criterion for the loop parameters. Moreover, the laser frequency noise observation method is developed as a new measurement tool. With a fast digital proportional integrator based on a single field programmable gate array applied in the active stabilization loop, the laser frequency noise is reduced to 0.021 Hz (1σ). It is equivalent to a rotation rate of 0.07°/h, and close to the shot noise limit for the RFOG. As a result, a bias stability of open-loop gyro output is 9.5°/h (1σ) for the integration time 10 s in an hour observed in the RFOG. To the best of our knowledge, this result is the best long-term stability using the miniature semiconductor laser.

Optimization of frequency stabilization loop for resonator fiber optic gyro

“…Jin et al described the model of the frequency stabilization loop in the counterclockwise (CCW) direction in detail [4]. The frequency stabilization loop is composed of a laser, a frequency discriminator and a PI controller, as shown in Figure 1.…”

“…Laser frequency noise is the main one of the reciprocal noises. Z. Jin et al demonstrated the influence of the laser frequency noise in the RFOG and proposed an effective method of a frequency stabilization loop based on the proportional integrator (PI) [4].…”

Laser frequency locking with second-harmonic demodulation

“…The double/hybrid phase modulation technique was also demonstrated theoretically and experimentally [19,20]. The modulation technique based on the absorption feature can realize carrier suppression; however, the modulation frequency is limited by the FWHM of the reference cavity, which is not suitable for 1/f noise suppression when the FWHM is relatively small [21]. The Pound-Drever-Hall (PDH) technique based on the dispersion feature can solve this problem [22,23].…”

Current modulation technique used in resonator micro-optic gyro

“…The rotation rate sensitivity of 0.28 deg∕h (10 s integration time) is achieved by Imai et al, using a highly coherent laser diode module [18]. Jin et al demonstrated an RFOG employing a distributed feedback laser diode, a bias stability of 9.5 deg∕h for the integration time 10 s in an hour was obtained [19]. A fiber ring resonator (FRR) is used to sense the angular velocity in the RFOG.…”