暗光纤 Dark fiber
暗光纤指的是已经铺设但是没有投入使用的光缆。很多时候通信公司会铺设多余其需求的光纤数量，以适应将来的需要而避免反复的光纤铺设带来的高额成本。暗光纤可能被租用给个人或者其他公司，用于在他们自己的场所之间建立光连接。在这种情况下，光纤既不受电信公司控制也没有连接到电信公司，而是由公司或者个人提供必要的设备使得其正常运作。
Dark fiber refers to unused fiber-optic cable. Often times companies lay more lines than what's needed in order to curb costs of having to do it again and again. The dark strands can be leased to individuals or other companies who want to establish optical connections among their own locations.
In this case, the fiber is neither controlled by nor connected to the phone company. Instead, the company or individual provides the necessary components to make it functional.