Sensitivity-variable fiber optic pressure sensors using microbend fiber gratings

We report on sensitivity control of fiber optic sensors using microbend long-period fiber gratings. By tuning the phase difference between a pair of periodically aligned rod arrays that sandwiches a single-mode fiber, we can change the coupling strength of the core mode with radiating cladding modes, resulting in variable pressure sensitivity of the transmission power through the fiber. This technique enables control of the measurable range of pressure. When the phase difference is shifted from π toward 0, the measurable range is expanded from 1.7 to 3.3 N/cm and higher using a light-emitting diode as an input light source.