A resonator integrated optic gyro (RIOG) employing trapezoidal phase modulation (TZPM) technique is proposed, analyzed, and demonstrated for the first time. This technique can provide more information about the whole gyro system without complicating the light circuit structure, making it possible to compensate the gyro output in real time. The experimental results of the RIOG prototype show that the standard deviation is greatly reduced after compensation, which proves the viability and effectiveness of the TZPM technique. A bias stability of 0.09 deg/s with an integration time of 10 s over 3000 s is achieved, which is, to our knowledge, the best long-term performance that ever been reported in a RIOG based on a silica waveguide ring resonator.

A transmissive resonator optic gyro (TROG) based on silica waveguide ring resonator with improved long-term bias stability is reported in this paper. The modeling of a transmissive resonator used in optic gyro is carried out. The polarization dependence of resonator and the influences of phase modulator's residual intensity modulation on the gyro output are analyzed. The resonator is simulated, designed, fabricated, tested and used to build up a TROG prototype. A bias stability of 0.22°/s over one hour test with an integration time of 10s is successfully demonstrated. No obvious drift has been found from the Allan variance analysis result of a 10000s test data, which means that the TROG prototype has an improved long-term drift characteristic.

A high carrier suppression level is required to reduce the backscattering noise of a resonator integrated optic gyro (RIOG). This paper proposes a double triangular phase modulation (DTPM) technology for backscattering noise reduction. The principle of the DTPM is described and the carrier suppression of the DTPM is theoretically analyzed and simulated. Based on the numerical simulations, the modulation parameters of the DTPM are optimized. Compared with single triangular phase modulation technology, the DTPM can not only achieve higher carrier suppression but also relax the requirements of modulation amplitude accuracy and temperature stability. The advantage of the DTPM for carrier suppression is validated by experiments, demonstrating that the DTPM is helpful in backscattering noise reduction. As a result, the experimental setup of the RIOG based on the DTPM is established: a bias stability of 0.22  deg/s (10 s integrated time) is achieved for 1 h. To our knowledge, this is the best long-term bias stability of an RIOG reported to date.

An external-optical-cavity-based laser frequency-locking method with second-harmonic demodulation was proposed, analyzed, and demonstrated. The second-harmonic component of the cavity output was demodulated to feed back to the frequency-locking loop, resulting in a high sensitivity, great carrier suppression, and large modulation bandwidth. The experimental demodulation curve was consistent with the simulation result. A distributed feedback fiber laser was then locked using this technique. A carrier wave suppression ratio of -67  dB and a laser frequency noise floor of 1  Hz/Hz level above 1 Hz were achieved. This technique has great potential to be used in resonator optic gyroscopes.

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