Optical Fiber Vibration Sensor With Wide Detection Range Based on STDS Structure Designed by Mach-Zehnder Interferometer

This article presents an optical fiber vibration sensor with a wide detection range based on the Mach-Zehnder interference principle, which is composed of single-mode fiber (SMF), two-mode step index fiber (TMSIF), and dispersion-compensated fiber (DCF) fused, and the optical fiber sensing structure fused is SMF-TMSIF-DCF-SMF, abbreviated as STDS sensor. In this work, the single-frequency response and dual-frequency response of this sensor are tested, and the test results indicate that the sensor can stably measure the extended single-frequency response in the range of 1-23 000 Hz (the maximum signal-to-noise ratio (SNR) is 61.2 dB) and the dual-frequency response. In addition, the amplitude-frequency response test results reveal a good linear relationship between the fast Fourier transform (FFT) amplitude and the vibration amplitude. Subsequently, a temperature test was performed on the sensor in the range of 25 degrees C-65 degrees C, and it was found that the spectral intensity shift induced by temperature was only 0.03501 dB/degrees, and the measured frequency was consistent with the applied frequency. Finally, the stability and repeatability tests were carried out on the sensor; the stability test results proved that the sensor measured consistently and without deviations for 60 min, and the repeatability test proved that the sensor could measure consistently for more than 40 days and that the measurement results were accurate. The sensor has the advantages of a wide detection range (the frequency measurement range is 1-23 000 Hz), excellent anti-interference to temperature fluctuations, reusability, and so on, and has great application prospects in various vibration signal monitoring.