@gsuberland @azonenberg @brouhaha @petrillic 12 strand MPO existed before IB used it. There is also 144 to aggregate 12 12 strand cables, used for building-building and WAN. I suspect this all goes back to the "networking does everything in multiples of 12", for example, 24 and 48 port switches. As far as I've been able to determine, the L-carrier system inherited the multiple of 12 thing from an earlier carrier system, that could multiplex 12 voice channels per wire.