[1] [1] P. J. Winzer, R. J. Essiambre. Advanced modulation formats for high-capacity optical transport networks［J］. J. Lightwave Technol., 2006, 24(12): 4711～4728

[2] [2] He Jing, Liu Limin, Chen Lin et al.. Generation of advanced modulation formats based on Mach-Zehnder modulators［J］. Chinese J. Lasers, 2008, 35(8): 1185～1190

[3] [3] Gao Junming, Chang Qingjiang, Wang Tao et al.. A cost-effective 100-Gb/s transmitter with low-speed optoelectronic devices and high spectral efficiency［J］. Chin. Opt. Lett., 2008, 6(8): 550～552

[4] [4] He Jing, Chen Lin, Wen Shuangchun. Performance research on 40 Gb/s DPSK format against polarization-mode dispersion［J］. Acta Photonica Sinica, 2009, 38(3): 660～664

[5] [5] S. Walklin, J. Conradi. Multilevel signaling for increasing the reach of 10 Gb/s lightwave systems［J］. J. Lightwave Technol., 1999, 17(11): 2235～2248

[6] [6] M. L. F. Abbade, E. A. M. Fagotto, R. S. Braga et al.. Optical amplitude multiplexing through four-wave mixing in optical fibers［J］. IEEE Photonic. Technol. L., 2005, 17(1): 151～153

[7] [7] Huo Li, Zhao Jian, Lin Chinlon et al.. Experimental demonstration of a novel all-optical multilevel 4-amplitude-shifted-keying coding/decoding scheme［C］. Optical Fiber Communication Conference and National Fiber Optic Engineers Conference, 2006, JThB41

[8] [8] David Dahan, Uri Mahlab, David Levy. Novel all-optical quaternary amplitude shift keying modulation technique based on cross gain modulation in a semiconductor optical amplifier［J］. Opt. Engng., 2009, 48(5): 055007～0550011

[9] [9] H. Soto, A. Gutiérrez. All-optical 2-to-4 level encoder based on cross polarization modulation in a semiconductor optical amplifier utilized to develop an all-optical 2 input digital multiplexer［J］. Opt. Express, 2006, 14(20): 9000～9005

[10] [10] Han Bingchen, Yu Jinlong, Luo Jun et al.. Multi-channel all-optical non-return-to-zero to return-to-zero format converter based on fiber optical parametric amplifier［J］. Chinese J. Lasers, 2009, 36(11): 2962～2965

[11] [11] Yu Yu, Zhang Xinliang, Wang Fei et al.. Multilevel all-optical format conversion from NRZ signal to RZ signal［C］. Asia Communications and Photonics Conference and Exhibition, 2009, FY2

[12] [12] M. Fujiwara, J. Kani, H. Suzuki et al.. Flattened optical multicarrier generation of 12.5 GHz spaced 256 channels based on sinusoidal amplitude and phase hybrid modulation［J］. Electron. Lett., 2001, 37(15): 967～968

[13] [13] Y. Takita, F. Futami, M. Doi et al.. Highly stable ultra-short pulse generation by filtering out flat optical frequency components［C］. CLEO, 2004, CTuN1

[14] [14] Huo Li, Dongyi, Lou Caiyun et al.. Clock extraction using an optoelectronic oscillator from high-speed NRZ signal and NRZ-to-RZ format transformation［J］. IEEE Photon. Technol. Lett., 2003, 15(7): 981～983