Full investigation of the resonant frequency servo loop for resonator fiber-optic gyro

Abstract

Resonator fiber-optic gyro (RFOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A high-accuracy resonant frequency servo loop is indispensable for a high-performance RFOG. It is composed of a frequency discriminator, a loop filter, and a laser actuator. Influences of the loop parameters are fully developed. Optimized loop parameters are obtained by considering the noise reduction and wide dynamic performance of the RFOG. As a result, with the integration time of 10 s, the accuracy of the resonant frequency loop is increased to 0.02 Hz (1σ). It is equivalent to a rotation rate of 0.067°/h, which is close to the shot noise limit for the RFOG, while a minimum rotation of ±0.05°/s has been carried out simultaneously. These are the best results reported to date, to the best of our knowledge, for an RFOG using the miniature semiconductor laser that benefits from the optimization of the resonant frequency servo-loop parameters.

Low-delay, high-bandwidth frequency-locking loop of resonator integrated optic gyro with triangular phase modulation

“…The delay time of the frequency-locking loop, which is one of the significant parameters affecting the frequency-locking error [14,20,21], is composed of optical signal delay, circuit signal delay, and signal processing delay. In an RIOG system, the optical signal delay and the circuit signal delay are at the same order of magnitude 10 −9 s, which can be neglected compared with the signal processing delay.…”

“…As a result, a smaller τ l and τ d are theoretically beneficial to improve the performance of loop. But a smaller τ l will bring about more noises [21], the value selected should be comprehensively considered.…”

“…It has been widely investigated in recent decades [10][11][12][13]. Although the short-term bias stability of the RIOG has been reached, 1.85 × 10 −4 rad∕s (0.0106 deg ∕s) for 60 seconds [14], the long-term performance is affected by backscattering noise [15][16][17], polarization noise [18,19], accuracy of frequency-locking loop [20][21][22], and so on. Much work is required to improve the performance of the RIOG.…”

“…In a RIOG system, in order to detect the resonance frequency difference induced by the Sagnac effect, the frequency of the laser is usually locked to the resonance frequency of the clockwise (CW) or counter-clockwise (CCW) lightwave propagating in the resonator [30,31], which varies with the rotation and is also perturbed by environment. Moreover, the dynamic performance of the RIOG is dependent on the bandwidth of the frequency-locking loop [21]. Consequently, a high precision and wide bandwidth frequency-locking loop is indispensable for RIOG.…”

Reduction of the effect of the overflow reset in resonant frequency servo loop for resonator fiber optic gyro

“…To obtain a high-performance R-FOG, a high-accuracy resonant frequency servo loop which is used to make the central frequency of the laser source to track the resonance of the OFRR in one direction, is indispensable. Digital proportionalintegral (PI) controller, which implemented on a single field-programmable gate array (FPGA), was adopted in the resonant frequency servo loop to reduce the residual error at the frequency of the lock-in detection [6][7][8]. The resonant frequency of the OFRR drifts with environmental temperature change.…”