Transverse-load, strain, temperature, and torsion sensors based on a helical photonic crystal fiber

In this Letter, we demonstrate a fabrication method of a helical photonic crystal fiber (HPCF) and an inflated HPCF (IHPCF) by use of an inflation-assisted hydrogen-oxygen flame heating technique. The transverse load, strain, temperature, and mechanical torsion properties of the HPCF and IHPCF were investigated experimentally to develop high-sensitivity sensors. The experimental results show that the transverse-load sensitivity could be greatly enhanced by means of enlarging the size of the air holes in the IHPCF; that is, the transverse-load sensitivity, i.e., 15.50  nm/(N·mm^-1), of the IHPCF is two times higher than the transverse-load sensitivity of the HPCF, i.e., 4.45  nm/(N·mm^-1). Moreover, both the HPCF and IHPCF exhibit high strain, temperature, and torsion sensitivities. Hence, such an HPCF/IHPCF could have great potential in sensing applications.