er 500Gb/s Cloud Xpress 5x 100GbE 16x 10GbE Figure 1-1 Representation of dense wavelength division multiplexers used for connections between data centers. (Based on image courtesy of Infinera) The distance between the highest parts of each wavelength equate to the wavelength sizes. Wavelengths www.TechnicalPDF.com are SO small that they are measured in nanometers. A nanometer equals one billionth of a meter. A nanometer- sized object is not visible to the human eye. A fiber-optic cable is smaller than a strand of hair or thinner than a sheet of paper. The Cloud Xpress is a first generation 500Gbps Dense Wavelength Division Multiplexer that supports an aggregate speed of 500Gbps. The newer second generation Cloud Xpress 2 is smaller and faster. Its capacity is 1.2 terabits per second and requires only one RU (rack unit), about 1.75 inches (44.45 millimeters) high in a 19-inch wide computer rack. The older Cloud Xpress takes up 2RU, essentially two vertical shelf units. Lasers-Lighting Fiber Lasers (Light amplification by stimulated emission of radiation) are the source of light on long-distance fiber networks and on fiber networks within cities. A laser turns light pulses on and off over fiber cables. Most outside fiber-optic cabling is connected to lasers for generating their light pulses. Due to improvements in manufacturing and chips, lasers are SO small that they are now available as computer chips integrated into line cards connected to fiber-optic cables. Super Channels-For Even More Capacity Super channels are an advanced form of dense wavelength division multiplexing. Super channels essentially mix multiple gigabit per second wavelengths together to achieve higher gigabit or terabit speeds on a single circuit card. In some systems, one wavelength can transmit at 100Giga bits per second. For example, a fiber used for sending can combine five 100Gbps wavelengths to transmit at 500Gbps. The fiber sending in the other direction can transmit at 500Gbps, equaling a total of a terabit of capacity. Thus, super cha