A refractive index (RI) sensor based on perfluorinated plastic optical fiber (PF-POF) is introduced in this paper. The PF-POF as multi-mode fiber was side-polished (SP) to form a macro-bending single-mode-multimode-single-mode (SMS) structure. Both ends of the sensor were closely connected to single-mode quartz optical fiber (SMF). The spectral characteristics of the sensor are measured, analyzed and discussed. The results show that when the length of PF-POF is 8 cm, the macro-bending radius is 3 cm, and the SP-depth is 20 μm. The intensity sensitivity reaches −219.504 dBm/RIU in the range of RI = 1.330 ~ 1.356. A reference is provided for the application of PF-POF in RI sensor in the future. The sensor is featured with low-cost, good flexibility and high efficiency.
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Schematic diagram of SP-area. (a) Structural equivalence. (b) Optical transmission.
The relationship between the energy of reflected and refracted light and the relative RI when the incident angle is θ.
The variation of reflected light intensity with incident angle; the dotted line indicates n01 = 0.9, and the solid line indicates n01 = 1.1.
Schematic diagram of the experimental setup.
(a) Cross section of the POF. (b) Connection between POF and SMF using ceramic ferrule and ceramic mating sleeve.
Schematic of experimental setup for polishing fibers.
Transmission spectra of the RI sensor with different POF length.
Transmission spectra of different SP-depths. (a) D=0 μm. (b) D=10 μm. (c) D=20 μm. (d) D=30 μm.
Macro-bending diagram. (a) SDB. (b) ODB.
Transmission spectra of different macro bending.
Schematic diagram of stress change. (a) SDB. (b) ODB. The dotted line is evenly stressed and the solid line is not evenly stressed.
Intensity response of RI sensor.
Transmission response of the perfluorinated POF-based RI sensor at different temperature. (a) Output power response. (b) Wavelength response.