Vasileios Gkamas Konstantinos Christodoulopoulos Emmanouel A. Varvarigos Energy-aware multi-layer flexible optical network operation. 16-21 2015 SoftCOM https://doi.org/10.1109/SOFTCOM.2015.7314088 conf/softcom/2015 db/conf/softcom/softcom2015.html#GkamasCV15