LEDs can be used for either free-space communication or for fiber communication applications. Free-space communication applications include the remote control of appliances such as television sets and stereos, and data communication between a computer and peripheral devices. LEDs used in optical fiber communication applications are suited for distances of a few km and bit rates up to about 1 Gbit/s. Most fibers used with LEDs are multimode (step-index and graded - index) fibers. However, some applications employ single-mode fibers.