The resonant micro-optic gyroscope (RMOG) is an attractive candidate for inertial rotation sensors requiring small, light and robust gyros. A high-performance RMOG needs a low-loss and high finesse waveguide-type ring resonator (WRR). Two general configurations of the WRRs which are made of Ge-doped silica core waveguides based on plasma enhanced chemical vapor deposition including the reflector-type and the transmitter-type are introduced. The reflector-type WRR with a length of 7.9 cm and a diameter of 2.5 cm has a finesse of 196.7 and a resonant depth of 98%. In addition, it’s pigtailed with single-polarization fiber to reduce the polarization error. The transmitter-type WRR with a length of 15.9 cm and a diameter of 5.06 cm has a finesse of 128 and a resonant depth of 95%. The waveguide loss low as 0.007 dB/cm has been measured, leading to the shot-noise limited sensitivity of 1.0°/h when the average optical power at the input of the photodetector is 1 mW and the detecting bandwidth is 1 Hz.
A high-finesse silica waveguide ring resonator (WRR) is designed and a new record is demonstrated experimentally. The finesse and the resonant depth of the silica WRR with a length of 7.9 cm and a diameter of 2.5 cm are 196.7 and 98%, respectively. In addition, the silica WRR is pigtailed with single-polarization fiber to improve the polarization extinction ratio thus to reduce the polarization error. With the application of this high-finesse and high polarization extinction ratio WRR to the resonant micro-optic gyroscope (RMOG), a bias stability of 0.004°/s was observed over a one-hour timeframe.
KEYWORDS: Resonators, Signal processing, Polarization, Gyroscopes, Digital signal processing, Fiber optic gyroscopes, Kerr effect, Polarizers, Temperature metrology, Signal detection
The resonant fiber optic gyro (RFOG) is a high accuracy inertial rotation sensor based on the Sagnac effect. The existence of various noises, including the nonreciprocal noises such as the polarization noise and the Kerr noise as well as the reciprocal circuit noise, limits the performance improvement of the RFOG. An improved scheme by inserting two in-line polarizers in the polarization maintaining fiber transmission-type resonator has been proposed to suppress the polarization-fluctuation induced drift. Furthermore, the adoption of the air-core photonic bandgap fibers (PBFs) offers a novel solution to reduce the optical Kerr effect. In addition, A digital signal processor is designed to reduce the reciprocal noises and detect the rotation information. A minimum actual rotation of 0.001°/s is achieved. The dynamic range is improved by a factor of 7 and the scale factor nonlinearity is decreased by a factor of 60.
A novel hybrid polarization-maintaining (PM) air-core photonic bandgap fiber (PBF) ring resonator is demonstrated by using a conventional PM fiber coupler formed by splicing a section of air-core PBF into the resonator. The coupling loss between the PM air-core PBF and the conventional solid-core PM fiber is reduced down to ∼1.8 dB per junction. With the countermeasures proposed to reduce the backscattering induced noise, a bias stability of approximately 0.007 °/s was observed over a 1 hour timeframe, which is the best result reported to date, to the best of our knowledge, for RFOGs equipped with a hybrid air-core PBF ring resonator.
A double closed-loop resonant micro optic gyro (RMOG) employing a hybrid digital phase modulation technique is demonstrated, showing encouraging progress. In this hybrid modulation scheme, the width of one stair of the stair-like digital serrodyne wave is optimized according to the rise time of the digital-to-analogue converter to obtain the maximum sideband suppression. Based on the optimum parameters of the hybrid modulation scheme, a typical bias stability of 0.05/s in 1 hr is demonstrated in an RMOG with a silica waveguide ring resonator having a ring length of 7.9 cm. This is the best long-term performance which has ever been reported in an RMOG to our knowledge.
A resonant micro optic gyro (RMOG) is a promising candidate for applications requiring small, light and robust gyros. A high-performance RMOG requires a low-loss micro-ring resonator, and thus a resonator having a high finesse. We experimentally create a new record for high-finesse micro-ring resonators by using 30-cm long low-loss fiber coils laid into the V-groove on a silicon substrate. Both the simulation and experimental results indicate that the 30-cm long micro-ring resonator is sufficient to build a tactical-grade RMOG. Experimentally, a bias stability of 0.046/s in 1800 s with an integration time of 1 s is successfully demonstrated.
Digital proportional-integral (PI) controller is always adopted in the resonant frequency servo loop in a highperformance resonator fiber optic gyro (R-FOG). Large reset pulse at the output of the R-FOG occurs on the overflow reset of the digital PI controller, which limits the lock-in frequency accuracy and system response. To reduce the effect of the overflow reset in the digital PI, an auto-controlled reset technique is proposed and experimentally demonstrated. As a result, the time back to the lock-in state falls from 8 s to 5 ms. With the integration time of 1 s, the equivalent accuracy of the resonant frequency servo loop is improved to 0.18 deg/h.
A double closed-loop resonator fiber optic gyro (RFOG) with an improved digital serrodyne scheme is experimentally demonstrated. To overcome the effect of the imperfect serrodyne modulation, an improved frequency shifting module is designed and constructed on a single FPGA. The frequency resolution is improved to 0.01Hz, which is equivalent to a rotation rate of 0.04°/h. A bias stability of 2°/h is achieved in a double closed-loop RFOG with a 14.25-m long fiber ring resonator. This is the best result reported to date, to the best of our knowledge, for closed-loop RFOGs. Moreover, good linearity and large dynamic range are also experimentally demonstrated thanks to the closed-loop operation.
A frequency stabilization loop based on the proportional integrator is used in the resonator fiber optic gyro. Proper loop
parameters are important to the reciprocal noise suppression, the response speed improvement and loop stabilization. The
loop parameters such as the time constant of the low-pass filter, the loop gain, the integration time and the loop delay are
analyzed deeply and then optimized. A rotation result of ±0.05°/s has been carried out.
It is important to study the frequency noise of the laser characteristics in a resonator fiber optic gyro. A measurement of
the power spectral density of optic frequency noise is introduced into a resonator fiber optic gyro. An optic optimum
criterion for the frequency stabilization loop of the resonator fiber optic gyro is proposed, especially for the reduction of
the locking residual error and the widening of the gyro bandwidth.
A resonator fiber optic gyro (RFOG) based on a fiber-coupled semiconductor DFB-LD with an FPGA-based digital
processor is set up. A bias stability of 23deg/h over one hour is successfully demonstrated. This is the best result in long
time stability reported to date, to the best of our knowledge, for the RFOG based on a miniaturized laser source.
The resonance asymmetry in the waveguide ring resonator and its influence on the offset errors of the waveguide-type
optical passive resonator gyro (OPRG) are demonstrated experimentally and theoretically. The offset errors are produced
by the resonance asymmetry especially when the phase modulation spectroscopy technique is involved in the OPRG.
Modulation frequencies of both the clockwise and counterclockwise lightwaves are determined to decrease the offset
errors. The fundamental solution to eliminate the asymmetry influence on the OPRG is also proposed.
A resonator micro optic gyro (RMOG) with the proposed FPGA-based digital processor is set up. The double phase
modulation technique is applied to achieve high total carrier suppression. Rotation tests from ±0.1 °/s to ±5 °/s are tested,
where the processing circuit of RMOG is implemented by the instruments. The rotation test over a range of ±550 °/s has
been successfully obtained with all the processing circuit implemented in FPGA. To the best of our knowledge, these
results are the best results of RMOG ever demonstrated in silica resonator with the ring length as short as 7.9 cm.
The influence of the carrier suppression level on the gyro performance is demonstrated experimentally. Proportional
integrator is adopted in the frequency servo loop to eliminate the residual error at the lock-in frequency. Carrier
suppression is applied onto the clockwise and counterclockwise lightwaves at the same time. Total high carriersuppression
is realized with optical phase modulators. A bias stability of 0.46°/s in 50 seconds is demonstrated in a silica
waveguide ring resonator with the ring length of 7.9cm.
We report the first demonstration of silica waveguide optical passive ring resonator gyro (OPRG) based on the phase modulation spectroscopy technique. The ring resonator is composed of a 6-cm-long silica waveguide. Observed from the resonance curve, the free spectral range (FSR) of the resonator, the full width at half maximum (FWHM) of the resonance curve, the finesse (F) of the resonator, and the resonance depth are 3.4 GHz, 62 MHz, 54.8, and 70%, respectively. The detection sensitivity of this OPRG will be 7.3×10–5 rad/s. In the experiments, there is an acoustic-optical modulator (AOM) in each light loop. We lock the lasing frequency at the resonance frequency of the silica waveguide ring resonator for counterclockwise (CCW) lightwave; the frequency difference between the driving frequencies of the two AOMs is equivalent to the Sagnac frequency difference caused by gyro rotation. Thus, the gyro output is observed.
A novel optical waveguide rectangular ring resonator is designed and fabricated in silicon-on-insulator (SOl). The resonator is composed of four straight waveguides connected by four 90° directional change-turning mirrors. This merged structure allows compact size and low loss. The input and output waveguides to couple energy into and out from the resonator are also designed and optimized in this work.
This paper presents polarization-insensitive multimode interference (MMI) N X N Mach-Zehnder interferometer (MZI) optical switch. First we analyze the working principle of each component of the MMI-MZI optical switch. Then using the discrete spectral index method (DSIM) to optimize the access single-mode rib waveguide of the device, we design and fabricate a 4 X 4 MMI - MZI optical switch with simple digital driven circuitry, acceptable voltage (approximately 12 V) and low crosstalk (approximately -20 dB).
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