In-situ sensitivity calibration for a fiber Bragg grating Fabry–Perot interferometric pressure sensor in a side-hole fiber

We demonstrate an in-situ pressure-sensitivity calibration method for a fiber Bragg grating Fabry-Perot interferometric pressure sensor inscribed in a side-hole fiber. The calibration of pressure sensitivity is achieved by applying pressure internally to the sensor through the side holes in the fiber cladding. Both simulations and experiments confirm that the pressure sensitivity under internal pressurization closely matches that under external loading, enabling direct in-situ calibration. The sensor system maintains a resolution better than 1 psi up to 300°C and good repeatability. We also discuss exploiting the method for resolving measurement ambiguity arising from the rotation of the principal polarization axes of the sensor.