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E-4
A
PPENDIX
E: C
ABLING
R
EQUIREMENTS
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.
Multi-mode Fiber
Standards
The MMF-PMD standards define the requirements for an ATM cable plant
to support an interstation distance of up to 2 kilometers (1.25 miles) of
multi-mode fiber. The cable plant includes all fiber optic components
between any two communicating ATM devices and their associated
“station-to-network” connectors at each end.
To determine whether the cable plant complies with the MMF-PMD
standard, do the following:
1
Compare the specifications of the fiber you are using to standard
specifications, as described in Table E-1 and Table E-2.
2
If unlike fibers are mated in the cable plant, calculate insertion losses to
see whether they exceed the maximum attenuation value allowed for a
link, as described in Table E-3 and Table E-4.
3
Verify that the fiber's modal bandwidth is within an acceptable range for
the length of the link, as described on page E-7.
The following sections describe each of these steps and give examples.
Comparing Fiber to Specifications
Compare the specifications of the fiber you are using to those in the
following tables. If the fiber does not meet the specifications, use a
different fiber or contact 3Com's Technical Support.
The fiber you use must meet the specifications listed in Table E-1, which
describes the standard set forth in MMF-PMD. Table E-2 describes
62.5/125 cable, commonly sold as “ATM Spec,” which meets all the
requirements of the MMF-PMD standard.