Moire Apodization of Fiber Bragg Grating

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Because fiber Bragg gratings (FBGs) have very sharp, narrow-band reflection spectra, they are well suited to applications involving narrow-band optical signals, such as optical filters in optical telecommunication systems, fiber laser cavities, and various types of fiber sensors. There, the effective apodization techniques are ever strongly desired for spectrum shaping such as suppressing side-lobes.We have developed novel technique of the apodization using two-beam interference method that controls the angle of mirror reflection by very small amount in step-wise or continuously during the time of the FBG formation by UV laser irradiation, which consequently forms superposition of FBGs of slightly different grating period and hence achieves the apodization. Experiments by two-step control of the minor angle have demonstrated very clear spectrum shaping in suppressing side-lobes. Thus the new technique appears to provide very powerful apodization technique for the FBG fabrication.We have published the result to Japanese Journal of Applied Physics about our novel technique on two-beam interference method of FBG fabrication, to oral presentation to the conference of Japanese Applied Physics Society, and Japanese Journal of Optics about the new technique of apodization.