A novel U-shaped, packaged, and microchanneled optical fiber strain sensor based on macro-bending induced whispering gallery mode

Abstract A novel U-shaped, packaged, and microchanneled optical fiber strain sensor (MOFSS) based on the macrobending-induced whispering gallery mode (WGM) is presented in this paper. The MOFSS consists of etched optical fiber placed into a U-shaped, microchanneled photoresist mold and packaged with polydimethylsiloxane (PDMS) materials. This fabrication process not only can accurately control the bending radius of the entire fiber, but can also save a lot of time and cost in producing the MOFSS. A four-point bending experiment was conducted for strain calibration to compare the MOFSS with a traditional coil strain gauge. Due to the bending strain and the resulting change in the radius of the U-shaped fiber, the spectra of the MOFSS were deformed and shifted with differing strain increments. The results showed that when the MOFSS was placed under tensile strain, the resonant wavelength of the MOFSS generated a blue shift, and the tensile strain sensitivity of the sensor reached 0.0046 nm/μe.