Actually, a single fiber strand can support over 1 Terebit per second in real world applications and even more in a lab setting. Fiber-to-the-Home ISPs today can easily provide 1 and 10 Gigabit per second connections using low cost optics on either end of the fiber cables (and some do!). When you see fiber Internet offerings like Verizon FiOS that has speeds of 50-500 Megabits per second, you are seeing the result of a business decision (price discrimination), not a technological or economic hurdle.