Fig. 1. Schematic diagram of the microcavities-based MZI.

Fig. 2. Microscopic image of (a) the PCF cross-section, (b) microcavity 1 of sensor 2, (c) microcavity 1 of sensor 3, (d) microcavity 1 of sensor 4, and (e) microcavity and collapse area.

Fig. 3. Transmission spectra of the sensors 1, 2, 3, and 4.

Fig. 4. Wavelength shifts of interference spectrum of (a) sensor 1, (b) sensor 2, (c) sensor 3, and (d) sensor 4.

Fig. 5. Relations between wavelength shifts and the surrounding RI of different sensors.

Fig. 6. Spatial frequency spectra of sensors 1 and 4.

Fig. 7. Wavelength shifts with the increase of the temperatures for sensor 4.