ADSL loop extender

A DSL loop extender is a device that a telephone company can place between subscriber premises equipment and central office interfaces to extend the distance and increase the channel capacity of digital subscriber line (DSL) connections. ADSL repeaters are deployed by rural telephone companies trying to provide rural Internet service to farms and small towns where it is impractical to place the DSLAM closer to the subscriber. Typical distance improvements with a loop extender are shown in the diagram below, with rate in megabits per second and distance in thousands of feet. Multiple loop extenders can be placed on a line, effectively making the reach of the ADSL signal infinite. That is, it is possible to reach any subscriber with any ADSL speed if one uses multiple loop extenders. A repeater can either be an amplifier or a re-generator. Amplifiers increase the signal level of the analog transmission signal; re-generators demodulate the signal to binary, then re-modulate it into the original transmission frequency. Because regeneration restores the signal to binary, an indefinite number of re-generators can be placed on a line and is the preferred choice for services like T1 (Digital Signal 1) that have no distance limits. Because of the simplicity of the amplifier circuits, amplifiers are of lower cost than re-generators. Before the development of ADSL loop extenders and remote DSLAMs, ADSL was limited to 3–6 miles (5–10 km) from the Central Office depending on the wire gauge used. An ADSL Loop Extender works as an amplifier, boosting the signal level so it can travel longer distances. In some cases, service can now be established as far as 10 miles from the Central Office. In 2006, US telco promoted Fiber to the Home. This was driven by a rapidly growing housing sector that was creating the "greenfield" customers that are needed to make fiber to the home profitable. Later, with the housing sector in a serious recession, that "greenfield" seems to be drying up fast.