RF signals in the L-Band frequency range (950 MHz to 2150 MHz), between a central control room and a satellite antenna at a satellite earth station. By so doing, high frequency equipment can be centralized and high-loss, heavy and expensive coaxial cables can be replaced. Typically this RF-over-Fiber technology is considered for transmission distances starting at about 50 meters. With the use of DWDM RF-over-Fiber systems even the low loss bi-directional transmission of multiple RF signals over one optical fiber with transmission distances up to 100 km is enabled. Ka-Band Earth Station Diversity in Satellite Communication State-of-the art satellite communication systems at the highest data rates are operated on the Ka band . As transmission quality on Ka band frequencies is heavily dependent on weather conditions, suitable system configurations need to be carefully planned and chosen. In Ka band Site Diversity configurations signal transmission is redirected from the Main Site to a Diverse Site in case of adverse weather conditions. These Site Diversity configurations, often rely on DWDM RF-over-Fibre transmission systems, as those are the most cost efficient solutions and ensure good signal quality. Cable Television One popular use for RF over fiber is for cable TV systems. Content providers may transport their entire CATV channel lineup over a single-fiber optic cable, because this way they can transport the signal for hundreds of km. It works like this: An electrical RF signal usually in the range of 54–870 MHz is converted to modulated light using RF 1310 nm or 1550 nm laser optics. The light travels over single-mode fiber to the fiber optic RF receiver where is converted back to electrical RF. Electrical RF is directly connected to a TV or set-top box. 1550 nm is more popular because it has less losses in the fiber and by using fiber-optic amplifier known as EDFA it is possible to extend the transport distance. 1310 nm is losing about 0.35 dB/km of optical signal, 1550 nm is losing only 0.25 dB/km. Optical budget between transmitter and receiver varies depending on the transmitter power and receiver sensitivity. Deployment As of April 2012, AT&T had 3000 systems deployed in the USA in places like stadiums, shopping malls and inside buildings. "We continue to go very, very aggressively on distributing the antenna system solutions", said CEO Randall Stephenson in 2012. In China, systems are being widely deployed in industrial zones, harbors, hospitals and supermarkets. Plans