Enhancement of wavelength detection accuracy in fiber Bragg grating sensors by using a spectrum correlation technique

A digital post-processing technique based on spectrum correlation is developed and applied to determining the Bragg wavelength shift accuracy in fiber Bragg grating (FBG) sensors. Theoretical analysis shows that the enhancement factor is proportional to the square root of the number of the independent sampling points within the 3d B bandwidth of the FBG. A wavelength detection accuracy of better than 1 pm in terms of standard deviation was experimentally demonstrated, representing an enhancement factor of 7.3 over the conventional peak detection technique. This technique may also be used for applications such as white light interferometer sensors where the interferometric pattern shifts with applied measurand while the shape of the pattern remains unchanged.