[1] [1] H. Ruan and C. Gan, Chin. Opt. Lett. 8, 564 (2010).

[2] [2] F. Tian, L. Xi, X. Zhang, X. Weng, G. Zhang, and Q. Xiong, Chin. Opt. Lett. 8, 816 (2010).

[3] [3] C. Xie, Chin. Opt. Lett. 8, 844 (2010).

[4] [4] P. S. Andre and A. N. Pinto, Opt. Commun. 246, 303 (2004).

[5] [5] P. S. Andr′e, B. Neto, R. Nogueira, J. L. Pinto, A. L. Teixeira, M. J. Lima, and F. Da Rocha, in Proceedings of Lasers and Electro-Optics/International Quantum Electronics Conference and Photonic Applications Systems Technologies CWA1 (2004).

[6] [6] H. Bourdoucen, J. High Speed Networks 1, 51 (2008).

[7] [7] K. Yonenaga, A. Hirano, S. Kuwahara, Y. Miyamoto, H. Toba, K. Sato, and H. Miyazawa, Electron. Lett. 36, 343 (2000).

[8] [8] M. A. Roelens, J. A. Bolger, D. Williams, and B. J. Eggleton, Opt. Express 16, 10152 (2008).

[9] [9] T. Gong, F. Yan, D. Lu, M. Chen, P. Liu, P. Tao, M. Wang, T. Li, and S. Jian, Opt. Commun. 282, 3460 (2009).

[10] [10] H. Weber, R. Ludwig, S. Ferber, C. Schmidt-Langhorst, M. Kroh, V. Marembert, C. Boerner, and C. Schubert, J. Lightwave Technol. 24, 4616 (2006).

[11] [11] N. Jia, T. Li, K. Zhong, M. Wang, M. Chen, D. Lu, W. Peng, and J. Chi, Chin. Opt. Lett. 8, 741 (2010).