Cabletron Systems 100BASE-FX, Cabling Manual

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IEEE 802.5j (Multimode Fiber Optics) 10-9
Token Ring Network Requirements
Attenuation
Multimode fiber optic cables must be tested for attenuation with a fiber optic
attenuation test set. The test set must be configured to determine attenuation of
the cable at a wavelength of 850 nm. The attenuation test will confirm or deny that
the cable falls within an acceptable level. The acceptable level of attenuation for a
cable is dependent upon the type of multimode fiber optic cable being tested. The
acceptable levels of attenuation for the types of multimode fiber optic cabling
supported by Cabletron Systems products are listed in Table 10-1:
Link Length
The IEEE 802.5j specification sets the maximum length of a multimode fiber optic
link in a Token Ring installation at 2 km (6,560 ft). This maximum length assumes
that all other requirements for a Token Ring fiber optic link as detailed above are
met.
Trunk Cable Length
The maximum length of a multimode fiber optic trunk cable is identical to the
maximum allotment for station connections using the same media.
Table 10-1. Multimode Fiber Optic Attenuation Limits
Cable Type
Maximum
Attenuation
50/125
µ
m 13.0 dB
62.5/125
µ
m 16.0 dB
100/140
µ
m 19.0 dB