Highly sensitive torsion senor based on dual-side-hole fiber Mach-Zehnder interferometer

We experimentally demonstrate a highly sensitive directional torsion sensor based on a helical dual side-hole fiber (DSHF). The sensor is constructed by splicing a fraction of DSHF in between two short lengths of multi-mode fibers (MMFs), which forms a Mach-Zehnder interferometer (MZI) based on the interference between the core and cladding modes in the DSHF. The middle part of the DSHF is heated and twisted to get a spiral cladding, so that the cladding mode in the DSHF travels along a helical path. The introduction of the helical structure can greatly improve the torsion sensitivity of the senor and enables it to recognize the twist direction. Experimental results show that the torsion sensitivity can reach as high as 1.666 nm/(rad/m) and -1.413 nm/(rad/m) in the range of 0 ± 5.517 rad/m. Besides, strain sensitivity of the sensor is about -4.5 pm/µɛ.