Cabletron Systems 100BASE-FX, Cabling Manual

Page: 132 / 192

FDDI Network Requirements
12-2 SMF-PMD
Length
As long as all other cable quality specifications are met, the FDDI PMD allows a
multimode fiber optic link to be no longer than 2 km from station to station. This
2 km 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 maximum 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 FDDI 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.
SMF-PMD
Cable Type
The FDDI SMF-PMD specification requires the use of 8.3/125
µ
m single mode
fiber optic cabling which is designed for use with 1300 nm wavelengths. Other
sizes of single mode fiber optic cabling may be used with SMF-PMD compliant
products, but the performance of links made with these nonstandard cables will
be reduced.
Attenuation
The SMF-PMD specification allows any FDDI link made over single mode fiber
optic cabling a total end to end loss of 10 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.