5) Y. Suzaki, H. Iwata, K. Nakayama, Y. Mizutani, M. Yamauchi, E. Izumikawa, T. Yokouchi and S. Ejima, “Apodization method owing to the finite length of UV laser coherence in fabricating fiber bragg gratings”, Japanese Journal of Applied Physics, Vol.45, No.12, pp.9100-9102 (2006).