Attenuation; Insertion Loss; Delay - Cabletron Systems 100BASE-FX Cabling Manual

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 6-1 below:

Insertion Loss

The 10BASE-F specification allows for a total dB loss of 10.0 dB or less between
any two stations or devices connected by fiber optic cabling. When calculating
insertion loss, you must consider and count any loss introduced by fiber optic
splices, barrel connectors, distribution boxes or other cable management devices.
The typical dB loss for a splice or a connector is less than 1 dB. The loss statistics
for any fiber optic cable management hardware should be available from the
manufacturer.

Delay

As is the case with Full-Duplex 10BASE-T operation, Full-Duplex 10BASE-F
operation eliminates the possibility of collisions on a network link. Again, for
interoperability with the half-duplex 10BASE-F specifications, Cabletron Systems
recommends that a 10BASE-F link not exceed 5 km in length or 25.6 s of total
one-way propagation delay.
10BASE-F (Multimode)
Table 6-1. Multimode Fiber Optic Attenuation Limits
Cable Type
50/125 m
62.5/125 m
100/140 m
Full-Duplex Ethernet Network Requirements
Maximum
Attenuation
13.0 dB
16.0 dB
19.0 dB
6-5