Cabletron Systems 100BASE-FX, Cabling Manual

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LCF-PMD 12-3
FDDI Network Requirements
Length
If all other cable quality specifications are met, the FDDI SMF-PMD allows a
single mode fiber optic link to be no longer than 58 km from station to station.
This total length must include all connector and patch panels between the two
stations. Keep in mind when determining the maximum length of an FDDI fiber
optic link that the FDDI network may not exceed a total length of 100 km. If the
sum of all cable lengths within the network exceeds this 100 km limit, the FDDI
network will experience errors in token rotation timing and other operations, and
be unable to effectively recover from certain cable faults.
Emitted Power
The SMF-PMD specification requires that links meet transmission power
requirements. If these power requirements are not met, the strength of the FDDI
signal will be insufficient for proper recognition and reception. If an FDDI
transmitter does not produce signals with an emitted power of -20 dBm or better,
the signal will have difficulty propagating through the cable effectively and may
not be received properly at the termination of the link.
LCF-PMD
Cable Type
The LCF-PMD specification requires the use of 62.5/125
µ
m multimode fiber
optic cabling. While some other sizes of fiber optic cabling are permitted and may
partially interoperate with LCF-PMD devices, their use is nonstandard and not
recommended.
Attenuation
The LCF-PMD specification allows any FDDI link made over low-cost fiber optic
cabling a total end to end loss of 7 dB at a wavelength of 1300 nm. The same
penalties apply to the cable segment for splices and optical bypass switches that
apply to MMF-PMD links as discussed earlier.