Methods for improving fiber Bragg grating wavelength measurement precision

Two Fiber Bragg Grating (FBG) sensors with fixed Bragg wavelength were used as reference. The narrow band light from tunable filter driven by saw waveform voltage scanned sensing FBG and reference FBG respectively. Driving voltage corresponding to reflected peak wavelength of reference FBG can be calculated by employing Gaussian peak-seek algorithm. In the given reference wavelength range, wavelength of the tunable filter was calibrated by reference wavelength with high accuracy, and the relationship between the wavelength and the driving voltage was constructed, and Bragg wavelength of sensing FBG can be obtained with the linear interpolation method. In temperature sensing experiment, the temperature measurement precisions of ±1℃, ±0.5℃ and ±0.3 ℃ are achieved by applying Centroid method, differential method and Gaussian-fit method to calculate peak position. Corresponding wavelength error is ±10pm, ±5pm and ±3pm respectively. The experiment results show that wavelength calibration and good Gaussian peak-seek algorithm reduce the wavelength measurement error caused by wavelength nonlinearity of tunable filter and low scanning wavelength resolution.