Error Analysis and Measurement Uncertainty for a Fiber Grating Strain-Temperature Sensor

A fiber grating sensor capable of distinguishing between temperature and strain, using a reference and a dual-wavelength fiber Bragg grating, is presented. Error analysis and measurement uncertainty for this sensor are studied theoretically and experimentally. The measured root mean squared errors for temperature T and strain epsilon were estimated to be 0.13 degrees C and 6 mu epsilon, respectively. The maximum errors for temperature and strain were calculated as 0.00155 T + 2.90 x 10(-6) epsilon and 3.59 x 10(-5) epsilon + 0.01887 T, respectively. Using the estimation of expanded uncertainty at 95% confidence level with a coverage factor of k = 2.205, temperature and strain measurement uncertainties were evaluated as 2.60 degrees C and 32.05 mu epsilon, respectively. For the first time, to our knowledge, we have demonstrated the feasibility of estimating the measurement uncertainty for simultaneous strain- temperature sensing with such a fiber grating sensor.