Fiber Interferometer Spectrum Recognition Strategy for Sensitivity Enhancement and Wide-Range Wavelength Measurements.

Fiber interferometers are widely used in sensing, including temperature, refractive index (RI), liquid level, pressure, sound wave, and strain. Since those structures are able to provide high sensitivity leading to wide-range peak shifting, optical spectrum analyzer (OSA) with 600-1700-nm spectral window is conventionally used in their measurement. However, the OSA cannot capture interferometer spectrum change information efficiently due to its slow scanning speed, which cannot meet the simultaneous requirement of wide-range and fast detection. The realization of wide-range, high-sensitivity, and fast measurement of interferometer has become an urgent demand in this field. In this article, we propose spectral processing strategy based on fast Fourier transform (FFT) frequency filtering and dynamic time warping (DTW) spectral matching recognition to achieve high-sensitivity, wide-range wavelength measurements. The experimental results show that the interrogator-based strategy proposed in this article improves the sensitivity by 2-3 times compared with the OSA-based measurement. In addition, this strategy can expand the measurement range of the sensor by 10 times, without being limited by the range of the measuring instrument.