16QAM transmission with 52 bits/s/Hz spectral efficiency over transoceanic distance Zhang, H. ; Cai, J. -X. ; Batshon, H. G. ; Davidson, C. R. ; Sun, Y. ; Mazurczyk, M. ; Foursa, D. G. ; Pilipetskii, A. ; Mohs, G. ; Bergano, Neal S. Abstract Publication: Optics Express Pub Date: May 2012 DOI: 10.1364/OE.20.011688 Bibcode: 2012OExpr..2011688Z