Large Dynamic Range and High Sensitivity PGC Demodulation Technique for Tri-Component Fiber Optic Seismometer

Abstract

Three-component fiber optic seismometers are widely used in the detection of seismic signals. The arctangent approach of phase-generated carrier (PGC-Arctan) demodulation algorithm is one of the commonly used demodulation techniques in FOISs. Nonlinear factors such as phase modulation depth( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> ) variation and light intensity disturbance (LID) have an important impact on performance of traditional PGC demodulation algorithms. This paper introduces a new demodulation algorithm called Kalman filtering ellipse (PGC-Arctan-EKF) demodulation algorithm, which can improve the robustness of the fitting. In order to meet the requirements of high performance and low power consumption of seafloor sensing, Tri-Component fiber optic seismometer based on SoC(ARM +FPGA) is proposed in this paper. The phase self-noise of the system is better than −115 dB re rad/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> ,and the large signal can reach 66 dB re rad/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> @220Hz with the THD is −61.22 dB.