I've been working with 40 gig for a few years. When I first ordered a switch, one of the first publicly available with full 40 gig, I was appalled that I was going to have to use 4 pair of multimode fiber for each of my connections. I had planned on using single mode because I can do that with 1 pair. Even today, we're still looking at MM fiber instead of SM, even with the horrendous limitations and cost issues of MM. For instance, if you need to go 301 meters or more, you've got to go OM4 which is very expensive. You have to lay 4 times the number of pairs as SM and when we move to 100G, it'll be even worse because they're still doing things in 6,12,etc... SM can do 100G easily, up to 1K with the lower grade fiber, so in the SM 100G world, you'd be installing 1/12 the strands as you would in multi mode. I just can't figure where this makes sense.... I am aware that single mode has more expensive optics, and I know how much they cost when I first looked at this, but if this were the standard, that price would drop enormously. Anyone know why the industry has their head stuck on MultiMode?