Figure 2. Operation and characterization of the nanofiber-based pressure-sensor unit (NFPSU): a) Working principle of the NFPSU. b) Simulated optical-transmission distribution of 630-nm-wavelength light guided along an 800-nm-diameter optical nanofiber with bending radius 20 μm. c) SEM image of optical nanofiber. d) Micrograph of a U-shaped optical nanofiber guiding 633-nm light. e) NFPSU’s wavelength-dependent transmittance response to pressure in the range 0-31.8 kPa. Inset: Transmittance response at 630 nm wavelength. f) 6000 repeated cycles of stability test. g) Response to a pressure signal with a frequency of 800 Hz.