1. T. Horiguchi, T. Kurashima and M. Tateda: IEEE Photon. Technol. Lett. 1 (1986) 107.
2. N. Yasue, H. Naruse, K. Hiramatsu, H. Kino, T. Nakamura and T. Yamaura: Opt. Fiber Technol. 99 (1999) 1.
3. H. Naruse, Y. Uchiyama, T. Kurashima and S. Unno: IECE Trans. Electron. E83-C (2000) 462.
4. T. Kurashima, T. Horiguchi, H. Izumita and Y. Koyamada: IEICE Trans. Commun. E76-B (1993) 382.
5. H. Naruse and M. Tateda: Appl. Opt. 38 (1999) 6516.