3com 10005622 Manuel D’Utilisation

C

HAPTER

 3: C

ABLING

 S

WITCH

 3900 P

ORTS

The back panel of the Switch 3900 has one fixed 
Gigabit Ethernet port and slots for two optional 
Gigabit Ethernet modules.

Both versions of the Switch 3900 (24 port and 36 
port) have:

■

One fixed port designated for 1000BASE-SX 
multimode fiber (MMF) cable with paired SC 
connectors. 

■

Two expansion slots on the back panel to hold 
optional Gigabit Ethernet modules. Each slot 
supports either the 1000BASE-LX module (SMF) or 
the 1000BASE-SX module (MMF).

Follow these guidelines when cabling SC connectors:

■

Verify that the length of the fiber cable from the 
system to any location does not exceed these 
recommended distances:

■

Use 1000BASE-LX over 8-micron to 10-micron 
SMF fiber for distances of up to 3 kilometers 
(1.86 miles).

■

Use 1000BASE-SX over 62.5-micron MMF fiber 
for distances of up to 260 meters (852 feet).

■

Use 1000BASE-SX over 50-micron MMF fiber 
for distances of up to 525 meters (1722 feet).

■

Each Gigabit Ethernet fiber cable terminates in a 
pair of SC connectors. The 1000BASE-LX cable 
connectors are blue; the 1000BASE-SX cable 
connectors are black. The connectors are made so 
that you can only insert them correctly.

■

Keep the ports and connectors free of dust. Keep 
dust covers over each empty port. See also 
“Cleaning Dirty Fiber Optic Ports and Connectors” 
on page 6-4 for details.