The peak reflectance wavelengths of gratings with reflectance maxima separated by less than 2 nm can be accurately determined through a demultiplexing method based on Hilbert transforms of interferograms. We demonstrate a wavelength demultiplexing of three fiber Bragg gratings (FBG's) with less than 4 pm crosstalk and repeatability and less than 19 pm uncertainty. We anticipate that a large number of gratings can be demultiplexed with a single broadband source and a single receiving interferometer, provided that the interferogram is sampled at accurate intervals slightly above the Nyquist rate.
Kent B. Rochford and Shellee D. Dyer, "Demultiplexing of Interferometrically Interrogated Fiber Bragg Grating Sensors Using Hilbert Transform Processing," J. Lightwave Technol. 17, 831- (1999)