Infrastructure is everything to networks. If you have the proper infrastructure, you can build flexible networks that efficiently reach out to your users. On the other hand, if you don't, you need to build it before you can deploy the network you need.
Copper remains the infrastructure of choice for intrabuilding LANs. However, for enterprise networks, the infrastructure is increasingly fiber-based. Fiber supports Gigabit Ethernet, ATM, and Packet over SONET. With transceivers, even good old-fashioned 10/100 Mbps Ethernet can run over fiber links.
There are two primary kinds of fiber: single-mode and multimode. The main difference between the two is distance and cost. Multimode is typically used for shorter distances, such as within buildings, while single-mode is normally used to span long distances of up to several miles. Of the two, single-mode is more expensive and often more in demand.
Slicing up the fiber
Dark fiber is like pizza. As soon as people know you have it, everyone seems to want a slice because you can use it for everything from data to video connections. You can even run PBX T-1 emulation over fiber.
There's a finite number of strands in each sheath of fiber, and unused strands have a tendency to become increasingly scarce as your enterprise network grows. At first you think you have all the fiber in the world, so you aren't hesitant to give away unused strands for nonnetworking purposes. But as time passes and your network needs grow, you realize you can't expand your network without the expensive task of pulling more fiber.
The moral? Be careful about what you give away. If the requested application makes sense to you and you have enough reserve, that's fine. Otherwise, turn down the request. Giving out fiber strands is easy, particularly when you have fiber to burn, so to speak. However, as your network grows, getting it back can be extremely difficult.
Adding fiber is expensive, so treat your fiber infrastructure for what it is -- a rare and valuable commodity.