1. E. Ip, J.M. Kahn, Carrier synchronization for 3- and 4-bit-per-symbol optical transmission. J. Lightwave Technol. 23, 4110–4124 (2005).
2. N. Kikuchi, K. Mandai, K. Sekine, S. Sasaki, First experimental demonstration of single-polarization 50-Gbit/s 32-level (QASK and 8-DPSK) incoherent optical multilevel transmission. in Tech. Digest of the Conference on Optical Fiber Communication, Postdeadline paper PDP21, 2007.
3. J. Yu, X. Zhou, M.-F. Huang, Y. Shao, D. Qian, T. Wang, M. Cvijetic, P. Magill, L. Nelson, M. Birk, S. Ten, H. B. Mathew, S. K. Mishra, 17 Tb/s (161 × 114 Gb/s) PolMux-RZ-8PSK transmission over 662 km of ultra-low loss fiber using C-band EDFA amplification and digital coherent detection. ECOC Postdeadline paper Th.3.E.5, 2008.
4. M. Nakazawa, M. Yoshida, K. Kasai, J. Hongou, 20 Msymbol/s, 64 and 128 QAM coherent optical transmission over 525 km using heterodyne detection with frequency-stabilized laser. Electron. Lett. 42, 710–712 (2006).
5. M. Nakamura, Y. Kamio, T. Miyazaki, Linewidth-tolerant 10-Gbit/s 16-QAM transmission using a pilot-carrier based phase-noise canceling technique, Opt. Express. 16, 10611–10616 (2007).