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ATM Cabling
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3Com supports multi-mode fiber (MMF-PMD) 62.5/125 µm and Category
one (1) single mode fiber (short reach) (SMF-PMD). When deciding
whether to use multi-mode or single mode fiber, determine the maximum
interstation distance (the distance from the CoreBuilder 7000 to any
potential end station):
■
If the maximum interstation distance is less than or equal to 2
kilometers (1.25 miles), use multi-mode fiber (MMF-PMD).
■
If the maximum interstation distance is greater than 2 kilometers (1.25
miles) and less than or equal to 14.4 kilometers (8.6 miles), use single
mode fiber (short reach) (SMF-PMD).
Caring for Fiber Optic
Transceivers
Fiber optic transceivers are sensitive optical devices that need careful
handling. The following information offers suggestions about caring for
fiber optic cable.
Dirt on the Fiber Optic Lens
If dirt collects on the fiber optic lens, you may notice that the LED for an
ATM port either does not light or lights yellow. You may also notice
degraded performance of that port, as indicated by a decrease in the Link
Error Rate (LER) estimate for that port.
To prevent dust from collecting on the fiber optic lens, keep the dust
covers on the ports at all times when they are not in use. To clean a fiber
optic lens when it becomes dirty, see “Cleaning dirty fiber optic cables”
on page 95.
Damaged Transceiver Due to Excessive Insertion Force
The ATM specification for insertion force on the connector into an ATM
SC receptacle is 3.5 lbs. However, it is possible to exert up to 30 lbs. of
insertion force on the transceiver if you are too forceful while inserting
the SC connector into the receptacle. This can cause failure of the
transceiver's mechanical joints, permanently damaging the part and
disabling the port.
When inserting connectors into the ATM ports, gently insert the SC
connector into the receptacle until you hear the connector click into
place. Use only enough force to engage the connector in the receptacle -
no more than 3.5 lbs. This will avoid damage to the transceiver.