Ultra-sensitive current sensor based upon a thermal-sensitive FPI and conductive material combination

This paper introduces an ultra-high sensitivity current sensor based upon a thermal-sensitive Fabry–Perot interferometer (FPI) and a conductive material. First, FPI 1 and FPI 2 with different cavity lengths were prepared by canning the heat-sensitive material, polydimethylsiloxane (PDMS), into a capillary tube. Experiments have shown that both FPI 1 and FPI 2 are very sensitive to temperature, with temperature sensitivities of 2.30 and 1.75 nm/°C, respectively. Then, FPI 1 and FPI 2 are respectively attached to thin copper rods, conducting current through the copper rods to generate abundant heat, which is converted into temperature changes on FPI 1 /FPI 2 to measure the current. The experiment exhibited that the current square sensitivity of FPI 1 and FPI 2 reached 4.56 and 2.43nm/A 2 . To further improve the current square sensitivity of FPI 2 , a current-insensitive reference interferometer, FPI 3 , was linked in parallel with FPI 2 to construct the sensor S 1 . Experiments had shown that S 1 had a vernier effect (VE) spectrum, which enhanced the current square sensitivity to 28.97nm/A 2 . Comparison showed that it improves the current square sensitivity of FPI 2 by nearly 12 times. The experiment also showed that S 1 has good measurement repeatability and static stability. In addition, S 1 offers low cost, easy manufacturing, and repeatable manufacturing, providing an innovative design method and a structural solution for manufacturing high-sensitivity current sensors.