
transmission capabilities. For example, EDC [21], tunable laser [25], and duobin-
ary [26] modulated transmitters have been incorporated in commercial 300-pin
modules. These improved capabilities simplify the job of transport system
integrators.
Link Diagnosis in 10 Gb/s Ethernet Traditionally, for cost and simplicity,
Ethernet does not include much diagnosis capabilities besides CRC frame integrity
check and PHY layer link-up/link-down verification. This was adequate when
Ethernet was mainly used in LAN environments. 10-Gigabit Ethernet was intended
for MAN applications. To improve network troubleshooting capabilities, for the
first time, the IEEE