Strain Sensor Based on a Long Period Fiber Grating with Dual-Resonance Closed in the Interferometric Structure

Spectral characteristics and amplitude tunabilitity of a long period grating with a dual-resonance inside fiber loop mirror are studied in terms of applied stress caused by the elongation. Inserting the polarization controller between grating and the loop structure enables tuning of resonance and interferometric peaks. The maximum sensitivity of demonstrated sensor is 1.943 dB/mμ for the range of 1.1-4.4 mμ. Combination of these two optical components enables to measure strain in wider range in comparing with sensors based on standard long period grating.