Fig. 1. Schematic of in-fiber Michelson interference sensor

Fig. 2. Light field distribution in SMF-MMF structure

Fig. 3. Calculated coupling coefficients of MMFs with different lengths

Fig. 4. Interference spectra of in-fiber Michelson interferometer based on MMFs with different lengths

Fig. 5. Spatial frequency spectra of in-fiber Michelson interferometer based on MMFs with different lengths

Fig. 6. Experimental setup of refractive index sensing

Fig. 7. Reflection spectra of sensing samples with different liquid refractive indexes. (a) L=7 mm; (b) L=11 mm; (c) L=22 mm

Fig. 8. Intensity versus liquid refractive index

Fig. 9. Reflection spectra of sensor samples in water with different temperatures. (a) L=7 mm; (b) L=11 mm; (c) L=22 mm

Fig. 10. Intensity versus temperature