A FBG Intensity Modulation System Combined with an Optical Whispering Gallery Mode Edge Filter

In this study, we demonstrated an edge filter–based fiber Bragg grating (FBG) intensity modulation system to realize strain measurement. In order to establish a precise and highly sensitive intensity modulation system, we utilized a bent single-mode fiber to induce whispering gallery mode (WGM) interference as an edge filter and combined that with a FBG sensor. The interference spectra of the attenuation band for the WGM edge filter were tuned by adjusting the bending radii. In addition, we compared and analyzed the signals from the proposed vibration interrogating system and a strain gauge. The measured voltage signals from the proposed interrogation system were in close agreement with measured strains of the strain gauge. The experimental results showed that when the resonant wavelength of the WGM edge filter was 1535.10 nm, the filtration was better and the noise was lower within 100 Hz. Moreover, as the frequency of piezoelectric transducer (PZT) was at 400 and 1000 Hz, the better signal-to-noise ratios (SNRs) of 28.54 and 25.97 were measured at wavelength 1542.05 nm of the edge filter.