| Interferometric fiber-optic sensor is an important category of fiber-optic sensor because of its high sensitivity. However, before implementing such sensor into a practical application, the signal fading caused by polarization fluctuations and random phase-shift must be overcome to maintain the stable output signal.Mach-Zehnder structure and Michelson structure are two typical ones of interferometric fiber-optic sensors. The magnetic sensor based on Mach-Zehnder interferometer has poor stability. The random changes of optical polarization have large affection on it. We use the method to eliminate polarization-induced noise by inserting Faraday Rotator Mirror (FRM) into Michelson fiber interferometer. Results show that it is a simple way to implement a fiber interferometer independent of polarization change while no extra optical signal processing needed.In this paper, the PTDC technique is employed to diminish the signal attenuation caused by random phase shift. the linear system theory is used to analyze the PTDC system. In result the feedback control system shows the transmission function like one order high pass filter. According that the payload of PZT is capacitance, I add isolator in the system in order to avoid the self excitation. In my design I replace traditional low-pass filter by band-stop filter, which brings remarkable optimization to the system.The result of the experiment shows that PTDC system effectively solves the signal attenuation caused by random phase shift. Through large amount of tests experiments, the analysis and configurations of circuits and the whole sensor system result in the exciting improvement of the stability of system and the ability to test weak magnetic field. According to the measurement and analysis results, we have the polarization-induced stability of interferometerα≥97.7736%, variance ratio of system outputγ≈0.039, variety of system output per secondη≈1.1×10?6. The weakest magnetic field that can be sensed is 10nT. |
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