The industry appears to be transitioning from 10x10G to a more efficient 4X25G. The first standard for 25Gb/s signaling was the OIF-CEI with VSR, SR and LR standards. What I have been looking at recently are the Ethernet 802.3bm 100GBASE-KR4 backplane standard and the Ethernet interconnect standard 802.3bj. To achieve 100G there is CAUI10, which is 10 lanes of 10G = 100G, while CAUI4 is 4 lanes of 25G = 100G. 100GBASE-CR4 is 4 lanes of 25G using CAUI4 = 100G throughput.
