Molex’s Loopbacks are high performance duplex serial data links used in communications. It is designed for high speed data rates from 2.5 to 12 Gbps (depending on which loopback you use) to support applications such as Fibre Channel, InfiniBand, and Gigabit Ethernet. The hot pluggable feature allows changing to/from another compatible module without having to remove system power. Each module provides complete serial ID compliance. Molex loopbacks are used to test host I/O system external ports. They help manufacturers ensure gigabit links are operational before systems ship out. Some loopbacks, QSFP and SFP+, have additional port testing capabilities. In addition to testing high speed signals, Molex loopbacks can test low speed functions such as, loss of signal, Tx disable, and ModPresL. They also can be used to load power lines.