[1] Chien-Jen and W. S. Wong, Electron. Lett. 37, 371 (2001).
[2] L. Zhang, S. H. Wang, and C. C. Fan, Proc. SPIE 4581, 222 (2001).
[3] W. Shieh, in Proceeding of OFC2002 511 (2002).
[4] Z. Tong, H. Wei, and S. S. Jian, Opt. Commun. 218, 105 (2003).
[5] Y. Sugaya, S. Muro, Y. Sato, and E. Ishikawa, in Proceedings of ECOC2002.
[6] S. Gray, in Proceedings of OFC2002 512 (2002).