In Oct 2015 Journal of Lightwave Technology a nice paper is published comparing various form of modulation for single carrier 100 Gb/s optical PMD.
Title: Modulation Schemes for Single-Laser 100 Gb/s Links: Single-Carrier
Authors: Sharif, M. ; Dept. of Electr. Eng., Stanford Univ., Stanford, CA, USA ; Perin, J.K. ; Kahn, J.M.
The paper actually reference several our contributions in the IEEE 802.3bm/bs, the conclusion of the paper is more or less in line with the IEEE decision to go with PAM modulation.
