Side-Polished D-Type Fiber SPR Sensor for RI Sensing With Temperature Compensation

We propose and demonstrate a dual-channel surface plasmon resonance (SPR) sensor based on the side-polished D-type optical fiber, which is available for simultaneous measurement of refractive index (RI) and temperature. The single mode fiber (SMF) is side-polished to remove the fiber cladding and plated a layer of gold film on the polished surface to excite SPR effect. The RI sensing characters are researched by simulation and experiment. The sensitivity increases from 1543 nm/RIU to 6300 nm/RIU as RI increasing from 1.333 to 1.410. Besides, the resonance wavelength red-shifts about 40 nm as the gold film thickness increasing from 40 nm to 60 nm. Based on the above, we design the temperature compensated RI sensor by modifying the side-polished D-type fiber. One half of the side-polished region is applied for RI sensing and the other half is additionally coated a layer of polydimethylsiloxane (PDMS), which is high sensitive to temperature variation, for temperature sensing. In addition, the resonance wavelengths of two sensing channels can be controlled by adjusting the film thickness to avoid crosstalk. In the range from 1.333 to 1.390, the RI sensitivity reaches as high as 2260.1 nm/RIU. In the range from 20 °C to 60 °C, the temperature sensitivity reaches as high as -2.41 nm/°C. Finally, by temperature compensation, the RI measurement accuracy can be greatly improved.