net and 802.3 u Fast Ethernet standards. Thus, Gigabit Ethernet retains the same framing, flow control, and link layer as do earlier versions of this networking technology and makes Fiber in the LAN Gigabit Ethernet compatible with 10BASE-T and 100BASE-T technologies supported by hubs, switches, and even repeaters. As a result, you can include existing Ethernet and Fast Ethernet network structures with the use of Gigabit Ethernet. Versions The IEEE 802.3z specification defines an 8B/10B encoding/decoding scheme that is used by each optical version of Gigabit Ethernet. The 802.3z standard is made up of two optical fiber specifications: one for low-cost copper jumpers or coaxial cable and one for twisted-pair media. Let's first briefly note the meaning of each of the Gigabit Ethernet standards, which define 1-Gbit/s operations over different media. Once this is accomplished, we see how Gigabit Ethernet can be integrated into a network. FIBER-OPTIC STANDARDS Two fiber-optic standards are associat- ed with Gigabit Ethernet: 1000BASE-SX and 1000base-LX. Because Gigabit Ethernet has a data transmission rate of 1 Gbits/s and a baud or signal- ing rate of 1.25 GHz, these speeds require the use of laser transceivers instead of LEDs, which have an operational cap of a few hundred megabits per second. 1000BASE-SX The 1000BASE-SX version of Gigabit Ethernet defines the use of an 850 nm laser transceiver operating on multimode fiber. Here the mnemonic SX is used to reference short-wave since the wavelength of the laser is 850 nm. 1000BASE-SX can operate on 50- and 62.5-um fibers, with a maximum transmission distance of 275 m for 62.5-um multimode fiber and 550 m when 50-um multimode fiber is used. The original intention of the IEEE 802.3z 1000BASE-SX standard was to support a trans- mission distance of up to 300 m for 62.5-um multimode fiber. Unfortu- nately, testing of the fiber indicated that the bandwidth of multimode 62.5-um fiber would not support the target transmission distance under worst-case conditions. Therefore, y