Simultaneous Measurement of Axial Strain and Temperature Based on Twin-core Single-hole Fiber with Vernier Effect

An ultrasensitive optical fiber sensor based on the Vernier effect is proposed for simultaneous axial strain and temperature measurement. The sensor structure comprises two cascaded Mach-Zehnder interferometers (MZIs) with different free space ranges. The MZI is built up by fusion splicing a segment of ~3 mm Twin-core Single-hole fiber (TCSHF) between two pieces of ~5 mm None core fibers (NCF). The sensor can respond linearly to the axial strain change with a sensitivity of ~17 pm/με in the range of 0 to 2000 με and high-temperature sensitivity of ~1.16 nm/℃ in the range from 30 to 70 ℃. Moreover, the cascaded structure can simultaneously measure the axial strain and temperature change with acceptable error ranges.