High-sensitivity pressure sensors based on mechanically induced long-period fiber gratings and fiber loop ring-down

A transverse pressure sensor with high-sensitivity based on a mechanically induced long-period fiber grating (MLPFG) and fiber loop ring-down technique is presented. When a MLPFG is spliced into a fiber loop, an extra loss is introduced, which leads to a decrease of the ring-down time. The results demonstrate that the difference between the reciprocals of the ring-down time with and without pressure increases exponentially with increasing the pressure in the range of 0–23.4 MPa. This sensor shows good repeatability, and the least detectable pressure is only 0.0068 MPa which is about 18 times less than detecting the output light intensity directly.