$B in Corning fiber optic cable implies $4-7B in total cost. Verizon April 21 commitment to the huge fiber buy implies a much larger network build. The actual fiber is almost always less than 30% of the total cost and sometimes < 10%. This should cover more than 100,000 miles of network.
Verizon just spent $1.8B to purchase XO and 20,000 miles of fiber around the country (map on left and larger below.) They have massive amounts of fiber in place in their territory, ~25% of the U.S. They also have extensive fiber to support their nationwide and international long distance network.