ABSTRACT
The residual intensity modulation (RIM) is one of the major sources of instability in optical detection based on phase modulation. In resonator fiber optic gyroscopes (RFOGs), the RIM leads to a nonzero output signal at the resonance center frequency, which degrades the bias stability of the RFOG. While the origins of the RIM are not fully understood, we present experimental results of the RIM in the Y-branch waveguide modulator with triangular phase modulation. We establish a model to analyze the RIM-induced error in the RFOG with triangular phase modulation and pointed out that symmetrical acquisition in a triangular wave period can reduce the RIM-induced error. We experimentally study the equivalent modulation depth of the RIM with different acquisition times in a triangular wave period and symmetrical acquisition in a triangular wave period. The results show that symmetrical acquisition in a triangular wave period can eliminate the RIM-induced error.
ABSTRACT
This paper is concerned with the angular random walk (ARW) limited by Rayleigh backscattering in the resonator fiber optic gyro (RFOG) with a light source of arbitrary temporal coherence. First, a model of Rayleigh backscattering noise in RFOGs is established to predict the fluctuation characteristics of backscattered intensity and interference intensity. Next, the formula for the ARW limited by Rayleigh backscattering is derived, and the requirement of carrier suppression level is calculated to make sure the ARW is limited by the detector's shot noise rather than Rayleigh scattering noise. Finally, the influences of the cavity length, the linewidth, and the finesse on the ARW limited by Rayleigh backscattering are investigated. The results predict that the influence of the cavity length L and the laser linewidth ΔυL on the ARW is dominantly related to the factor e-2πΔυLneL/c, and under the finesse 88, the best ARW is obtained when there is a relation L·ΔυL≈4×105 m·Hz.
ABSTRACT
A method for the automated alignment of optical waveguides and fibers based on a multiobjective evolutionary algorithm is proposed. This algorithm reduces the number of parallel operations considerably compared to previous automation schemes. The automated alignment of a single-core input fiber with a channel waveguide and a single-core output fiber is completed using this system in less than 3 min. The alignment of a single-core input fiber with a 1x8 splitter coupler and an eight-core output fiber array is completed in less than 10 min. These results demonstrate the effectiveness of the proposed scheme for automated waveguide alignment, substantially outperforming previous automatic alignment methods.
