Contiguous fiber Bragg grating arrays produced on-line during fiber draw

摘要

Arrays of fiber Bragg gratings (FBGs) have been produced on-line during fiber draw using a KrF excimer laser and a computer-controlled interferometer. A table of the desired Bragg wavelengths $lambda$-B$/ of the gratings is used by the computer to appropriately vary the intersection angle of the two interfering beams, maintain focus and beam intersection at the proper position relative to the fiber, and trigger the laser. A large number of narrow-line Type I gratings have been produced, and in some instances small Type II gratings have been found to overlap the Type I FBGs. The reflectance of the gratings in one series was found to be polarization-dependent, lending further support to our previous model whereby the index change induced by the excimer laser occurs at the core-clad interface asymmetrically on one side of the core.