 to the way light propagates through the fiber conductor. In multimode transport, the light wave travels down the fiber in multiple modes or through more than one route or path to get to the other end. In the process, the light waves traveling the different paths take slightly different amounts of time to reach the end. The behavior of the light is said to exhibit dispersion, or dis- perse, as it travels down the fiber. The dispersion and difference in travel time cause interference and distortion, which can impair signal integrity. Multimode fiber is the physically larger of the two, ranging from 125 to 400 microns in diameter. Losses in multimode fiber are the greater of the two, restricting its use to local applications such as LANs and building or campus environments. Single-mode fiber is physically smaller than multimode fiber, 8 to 10 microns in diameter. This fact is the reason it's called single mode PRACTICAL IP AND TELECOM FOR BROADCAST ENGINEERING AND OPERATIONS because the way to reduce dispersion and control the way the light behaves as it travels down the conductor is to reduce its size. Single mode fiber attenuation characteristics are a fraction of multimode fiber, making longer transmission distances without amplification possible. Both types of fiber are clad with reflective material on the outside surface. This guides the light down the fiber much like a microwave radio signal travels along a round or rectangular waveguide. There are three windows in the spectrum used in light wave transmis- sion. Short distance multimode transmission uses light in the 850-nM range. Single mode transmission runs in the range around 1310 nM and at the upper end between 1510 and 1600 nM. Early wave division multiplexing (WDM) mixed a 1310 lambda and a 1510 lambda on a common fiber in short-range applications and two widely spaced lambdas in the 1510 band such as 1538 and 1558 nM. WDM also enables bidirectional transmission on a common fiber. An extension of WDM is dense wave division multiplexing (DWDM). Distingu