The 10Gbase-LX standard requires the use of high performance multi-mode fiber. The majority of multi-mode fiber installed today is 5 - 10 year old FDDI grade cabling. The 10Gbase-LX4 technology sends and receives data as four WDM signals on the MMF and SMF fiber. These signals are sent at 0.25 the speed of 10Gbase-SX that allows the use of FDDI-grade cable. Foundry's 10GBASE-LX4 XENPAK optical transceiver will enable 10-GbE applications using legacy physical fiber plants.