Fig. 1. Microscope images of three-core optical fiber. (a) Cross-sectional view; (b) longitudinal tapered-fiber structure profile

Fig. 2. Schematic diagram of strain measuring device (the inset is the basic principle of the sensor)

Fig. 3. Interference spectrum, strain fitting and spatial spectrum. (a) Interference spectra of three-core optical fibers with different lengths; (b) strain fitting diagram of three-core optical fibers with different lengths and tapered waist diameter of 42.60 μm; (c) spatial frequency spectrum diagram of sensor with tapered waist diameter of 41.20 μm

Fig. 4. Strain interference spectra of optical fibers with different tapered waist diameters in the same strain range and the linear fitting of wavelength drift caused by strain. (a) 125-μm tapered waist diameter; (b) 42.60-μm tapered waist diameter; (c) 41.90-μm tapered waist diameter; (d) 41.20-μm tapered waist diameter

Fig. 5. Schematic diagram of temperature measuring device

Fig. 6. Interference spectra of different waist diameters and temperatures. (a) 42.60-μm tapered waist diameter; (b) 41.20-μm tapered waist diameter

Table 1. Performance comparison of the different optical fiber strain sensors