Simultaneous measurement sensor of temperature and stress based on UV lithography phase-shifted grating

The traditional fiber grating sensors are cross-sensitive to temperature stress and cannot simultaneously measure the change of the temperature stress of the measured object. In view of this situation, a new method of lithographing phase-shifted gratings using ultraviolet light was proposed. Before lithographing the gratings, the method of electrode discharge was used to remove the photosensitivity of a very small section of the optical fiber, so that the original uniform periodic distribution of the fiber was destroyed to form a phase-shifted grating, and its theoretical analysis was carried out. There were two distinct resonance peaks in the transmission spectrum of this phase-shifted grating. Using the properties of two peaks with different sensitivity to temperature and dependent variable, the simultaneous measurement of temperature and stress could be achieved by establishing the demodulation matrix. The experimental results show that the phase-shifted Bragg grating made by this method can realize the simultaneous measurement of temperature and stress accurately. The maximum temperature sensitivity of the sensor can reach to 9.51 pm/℃, and the sensitivity variance is lower than 2.125×10⁻⁷. The maximum strain sensitivity can reach to 0.767 pm/με, and the sensitivity variance is lower than 2.156×10⁻¹⁰.