e fiber, extending the transmission distance of the LAN to over 2 km. Figure 5.9 illustrates the use of a pair of 10BASE-T-multimode fiber extenders. Note that in this example one extender is attached to the port of a hub and uses fiber to enable a remote LAN user to join the LAN even though it is outside the 100-m diameter of the network. Figure 5.9 Using a pair of 10BASE-T extenders. multimode fiber 100 m network diameter legend workstation 10BASE-T to multimode fiber extender Chapter Five FOIRL AND 10BASE-F Two standards govern the transmission of Ethernet across dual-fiber cable: an original standard referred to as the fiber-optic inter-repeater line (FOIRL) and the more recent 10BASE-F, which is backward-compatible with the older standard and supports multiple Ethernet connections at distances up to 2000 m (6600 ft) from one anoth- er. FOIRL supports distances of up to 1000 m, while 10BASE-F devices double the distance to 2000 m. However, the ability to exceed 1000 m requires the use of 10BASE-F devices at both ends of the fiber. Under both FOIRL and 10BASE-F standards, an optical transceiver consists of a pulse generating LED, a photodetector, and associated trans- mit and receive circuitry. Figure 5.10 illustrates a stand-alone repeater, which includes a transceiver, housing, and connectors. Note the two opti- cal connectors that support the connection of two optical fiber cables, enabling one to be used for transmission while the second is used for reception of data. The physical dimensions of the FOIRL or 10BASE-F repeater/extender are normally equivalent to a pack of cigarettes, and the unit usually costs under $200. A second type of transceiver is commonly built into a fiber hub, permitting several optical ports to be available for use in the hub. In addition to providing optical ports, the fiber hub can contain one or more 10BASE-T ports and an AUI (attachment unit interface) port. Because all ports share a common power supply and circuitry, the cost on a per port basis can be less than the cost of us