IBM System Storage DS3500 Introduction And Implementation Manual page 64

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Figure 3-6 Small Form Pluggable (SFP) with LC connector fiber cable
Obviously, the particular connectors used to connect a fiber cable to a component will depend
upon the receptacle into which they are being plugged.
LC connector
Connectors that plug into SFF or SFP devices are called LC connectors. The two fibers each
have their own part of the connector. The connector is keyed to ensure correct polarization
when connected, that is, transmit to receive and vice-versa.
The main advantage that these LC connectors have over the SC connectors is that they are of
a smaller form factor, and so manufacturers of Fibre Channel components are able to provide
more connections in the same amount of space.
All DS3500 series products use SFP transceivers and LC fiber cables. See Figure 3-7.
Figure 3-7 LC fiber cable connector
Best practice: When you are not using an SFP, it is best to remove it from the port on the
DS3500 storage controller and replace it with a cover. Similarly, unused cables must be
stored with ends covered, which will help eliminate risk of dirt or particles contaminating
the connection while not in use.
Interoperability of 2 Gbps, 4 Gbps, and 8 Gbps devices
The Fibre Channel standard specifies a procedure for speedy auto-detection. Therefore, if a
4 Gbps port on a switch or device is connected to a 2 Gbps port, it must negotiate down and
the link will run at 2 Gbps. If there are two 8 Gbps ports on either end of a link, the negotiation
runs the link at 8 Gbps if the link is up to specifications. A link that is too long or "dirty" can end
up running at 4 Gbps, even with 8 Gbps ports at either end, so care must be taken with cable
lengths distances and connector quality is sound.
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IBM System Storage DS3500: Introduction and Implementation Guide
Draft Document for Review March 28, 2011 12:24 pm