Gents,
For your own comprehension, please take a short look at this presentation from 2011.
http://www.ieee802.org/3/100GNGOPTX/public/jul11/CFI_01_0711.pdf
At that time, 25 G VCSEL were not market ready.
Avago shipped more than 1 Million unit of 25 G VCSEL in 2015.
Datacenters are changing and will alway require more bandwith, lower power usage, costs reductions, POET, etc.
Regards,