x-Can send or full fiber for sending and and receive on same duplex receiving cable In older networks, once high-quality fiber is installed in trenches, newer lasers and dense wavelength division multiplexing can be added to increase its capacity to handle the growing amounts of traffic, including high- definition video transmitted along its routes. Dark Fiber Because of the high cost of laying fiber underground and digging trenches, organizations that build new fiber optic networks often lay more fiber than they need when they build the original network. They don't add fiber multiplexers or lasers needed to "light" the fiber on the extra fiber pairs. This fiber that does not have multiplexers or lasers connected to it is referred to as dark fiber. It has not been "lit" with equipment such as lasers needed to operate the fiber. See Figure 1-2 for an example of dark fiber. www.TechnicalPDF.com University campus Hosting Center k fiber Figure 1-2 A fiber-optic cable with DWDMs and dark fiber. For example, a university in the Northeastern United States installed two fiber runs to a hosting center where many of their computer servers were located. They added dense wavelength division multiplexing (DWDM) to one fiber run, and left the second one as an alternate route to their hosting center, to be used in the event of a cable cut in the main fiber pairs. Infinera: A Vertically Integrated Fiber-Optic Manufacturer Infinera, headquartered in Sunnyvale, California was founded in 2000 and was initially funded by venture capital companies. In 2007, the company raised an additional $300 million in an initial public offering. During the years between 2000 and 2005 when Infinera developed their fiber- www.TechnicalPDF.com optic technology, there was a glut of fiber-optic capacity. However, by the time they first began shipping their products in 2005, the glut was ending. Infinera's goal in designing their products was to enable network providers to bring up denser fiber- optic capacity in a single operation. They have a fully v