[1] Xuan H J, Wang Y P, Xu Z Q et al. Node security-aware spectrum allocation algorithm in elastic optical networks[J]. Chinese Journal of Lasers, 43, 1206002(2016).

[2] Jiang X K, Zhao F, Fan Y Q et al. Frequency assignment algorithm for elastic optical network with multi-cores considering crosstalk[J]. Laser & Optoelectronics Progress, 54, 060601(2017).

[3] Xuan H J, Wang Y P, Xu Z Q et al. Core selection algorithm for multi-core elastic optical networks[J]. Acta Optica Sinica, 36, 1206005(2016).

[4] Gringeri S, Bitar N, Xia T J. Extending software defined network principles to include optical transport[J]. IEEE Communications Magazine, 51, 32-40(2013). http://ieeexplore.ieee.org/xpls/icp.jsp?arnumber=6476863

[5] Roberts K, Laperle C. Flexible transceivers[C]. IEEE 38th European Conference and Exhibition on Optical Communications (ECOC), 14028857(2012).

[6] Bosco G, Curri V, Carena A. et al. On the performance of Nyquist-WDM terabit superchannels based on PM-BPSK, PM-QPSK, PM-8QAM or PM-16QAM subcarriers[J]. Journal of Lightwave Technology, 29, 53-61(2011). http://www.opticsinfobase.org/abstract.cfm?uri=JLT-29-1-53

[7] Winzer P J. High-spectral-efficiency optical modulation formats[J]. Journal of Lightwave Technology, 30, 3824-3835(2012). http://ieeexplore.ieee.org/document/6280581/

[8] Teipen B, Eiselt M H, Grobe K. et al. Adaptive data rates for flexible transceivers in optical networks[J]. Journal of Networks, 7, 776-782(2012). http://www.oalib.com/paper/2848235

[9] Zhuge Q B, Xu X, Morsy-Osman M. et al. Time domain hybrid QAM based rate-adaptive optical transmissions using high speed DACs[C]. Optical Fiber Communication Conference, Optical Society of America, OTh4E, 6(2013).

[10] Guiomar F P, Li R X. Fludger C R S, et al. Hybrid modulation formats enabling elastic fixed-grid optical networks[J]. Journal of Optical Communications and Networking, 8, A92-A100(2016). http://ieeexplore.ieee.org/document/7522667/

[11] van den Borne D, Jansen S L. Dynamic capacity optimization using flexi-rate transceiver technology[C]. 17th IEEE Opto-Electronics and Communications Conference (OECC), 769-770(2012).

[12] Zhou X, Nelson L E, Magill P. Rate-adaptable optics for next generation long-haul transport networks[J]. IEEE Communications Magazine, 51, 41-49(2013). http://ieeexplore.ieee.org/xpls/icp.jsp?arnumber=6476864

[13] Zhou X, Nelson L E, Magill P. et al. High spectral efficiency 400 Gb/s transmission using PDM time-domain hybrid 32-64 QAM and training-assisted carrier recovery[J]. Journal of Lightwave Technology, 31, 999-1005(2013). http://www.opticsinfobase.org/abstract.cfm?uri=jlt-31-7-999

[14] Gho G H, Klak L, Kahn J M. Rate-adaptive coding for optical fiber transmission systems[J]. Journal of Lightwave Technology, 29, 222-233(2011). http://ieeexplore.ieee.org/document/5667034/

[15] Gho G H, Kahn J M. Rate-adaptive modulation and coding for optical fiber transmission systems[J]. Journal of Lightwave Technology, 30, 1818-1828(2012). http://ieeexplore.ieee.org/document/6159047/

[16] Gho G H, Kahn J M. Rate-adaptive modulation and low-density parity-check coding for optical fiber transmission systems[J]. Journal of Optical Communications and Networking, 4, 760-768(2012). http://www.opticsinfobase.org/abstract.cfm?URI=jocn-4-10-760

[17] Arabaci M, Djordjevic I B, Saunders R. et al. Polarization-multiplexed rate-adaptive non-binary-quasi-cyclic-LDPC-coded multilevel modulation with coherent detection for optical transport networks[J]. Optics Express, 18, 1820-1832(2010). http://europepmc.org/abstract/MED/20174010

[18] Arabaci M, Djordjevic I B, Schmidt T. et al. Rate-adaptive nonbinary-LDPC-coded modulation with back propagation for long-haul optical transport networks[C]. IEEE 12th International Conference on Transparent Optical Networks (ICTON), 11475238(2010).

[19] Arabaci M, Djordjevic I B, Xu L. et al. Nonbinary LDPC-coded modulation for rate-adaptive optical fiber communication without bandwidth expansion[J]. IEEE Photonics Technology Letters, 24, 1402-1404(2012). http://ieeexplore.ieee.org/document/6218753/

[20] Fischer J K, Schmidt-Langhorst C, Alreesh S. et al. Generation, transmission, and detection of 4-D set-partitioning QAM signals[J]. Journal of Lightwave Technology, 33, 1445-1451(2015). http://ieeexplore.ieee.org/xpls/icp.jsp?arnumber=6983529

[21] Renaudier J, Bertran-Pardo O, Ghazisaeidi A. et al. Experimental transmission of Nyquist pulse shaped 4-D coded modulation using dual polarization 16QAM set-partitioning schemes at 28 Gbaud[C]. IEEE Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), 13582316(2013).

[22] Fischer J K, Alreesh S, Elschner R. et al. Bandwidth-variable transceivers based on four-dimensional modulation formats[J]. Journal of Lightwave Technology, 32, 2886-2895(2014). http://www.opticsinfobase.org/jlt/abstract.cfm?uri=jlt-32-16-2886

[23] He Z L, Liu W T, Shen B L. et al. Flexible multidimensional modulation formats based on PM-QPSK constellations for elastic optical networks[J]. Chinese Optics Letters, 14, 040602(2016). http://www.opticsjournal.net/Articles/Abstract?aid=OJ160412000285Xu1x4z

[24] Zhang Y Q, Arabaci M, Djordjevic I. Rate-adaptive four-dimensional nonbinary LDPC-coded modulation for long-haul optical transport networks[C]. National Fiber Optic Engineers Conference, Optical Society of America, JW2A, 46(2012).

[25] Alreesh S, Schmidt-Langhorst C, Emmerich R. et al. Four-dimensional trellis coded modulation for flexible optical communications[J]. Journal of Lightwave Technology, 35, 152-158(2017). http://ieeexplore.ieee.org/document/7755767/

[26] Kashero E L, Hu G J, Song Z X. Increased dimensionality of SP-MQAM modulation higher than 4D to 8D[J]. Optics Communications, 396, 15-18(2017). http://www.researchgate.net/publication/315121189_Increased_dimensionality_of_SP-MQAM_modulation_higher_than_4D_to_8D

[27] Ishimura S, Kikuchi K. Multi-dimensional permutation-modulation format for coherent optical communications[J]. Optics Express, 23, 15587-15597(2015). http://europepmc.org/abstract/MED/26193538

[28] Millar D S, Koike-Akino T, Arık S Ö. et al. High-dimensional modulation for coherent optical communications systems[J]. Optics Express, 22, 8798-8812(2014). http://europepmc.org/abstract/med/24718249

[29] Conway J H. Sloane N J A. Sphere packings, lattices and groups[M]. New York: Springer Science & Business Media(2013).

[30] Koike-Akino T, Millar D S, Kojima K. et al. Eight-dimensional modulation for coherent optical communications[C]. IET 39th European Conference and Exhibition on Optical Communication (ECOC 2013), 13841929(2013).