ata centers. To get closer to subscribers and large business clients, Internet content providers locate data centers in large cities as well as locations near plentiful electricity sources such as in Lulea, Sweden. Sweden offers the advantage of requiring less power for www.TechnicalPDF.com cooling because of its cold climate. Google has bought many buildings in New York City and other major cities SO that it can be closer to its many customers in these cities. This minimizes delays in responses to users that access Google. Fiber links to duplicate data centers enable cloud- based data centers to function even if one of their centers is disabled due to an equipment or software malfunction or a natural disaster such as a hurricane. Fiber links importantly enable cloud-based data centers to continuously back up their entire sites in real time to ensure that customer data is not lost during a disaster or malfunctions. The duplicate data center may be hundreds of miles away or nearby within the same city. Each data center that is linked to another data center and to subscribers has redundant fiber cabling connected to their facilities SO that if one group of fiber cables is damaged or cut, the other is still intact. For example, one bundle of fibers may be located on the eastern side of their building and another on the western side. Duplicate power sources are also installed at these data centers. Splitting Capacity of Individual Fiber Strands into Wavelengths Dense wavelength division multiplexers (DWDMs) add capacity to individual strands of fibers connected to fiber strands by dividing each fiber into numerous channels called wavelengths. See Figure 1-1 below. Dense wave division multiplexers divide the fiber into wavelengths using frequency division multiplexing, where each stream of light uses a different frequency within the fiber strand. In some networks, each wavelength is capable of transmitting a 100Gb stream of light pulses. www.TechnicalPDF.com Cloud X press 2 12x 100GbE 1.2Tb/s Super-channel port to fib