利用光学纤维的光缆在英国已做成世界上可能是最长的光通讯线路。英国邮政部把英格兰两个区两台电话交换机联结起来,而采用长21公里的双纤维光缆。光缆将铺设12公里,一个是5公里,另一条是7公里,两条之间用中继站。预计数据速率是8兆比特。梯度折射率纤维是由美国康宁玻璃工厂制造的 Fiber optic cables using optical fibers have been the longest possible optical communications line in the world in the United Kingdom. The British Post Department linked two telephone exchanges in two districts in England with a 21-km long fiber optic cable. Cable will be laying 12 km, one is 5 km, the other is 7 km, the relay station between the two. The expected data rate is 8 megabits. Gradient index fibers are manufactured by the Corning glassworks in the United States