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Appendix A: Cable Requirements
Page A-2 EMC39-12 User’s Guide
Attenuation
You must test the fiber optic cable with a fiber optic attenuation test set
adjusted for a 1300 nm wavelength. This test verifies that the signal loss
in a cable falls within the acceptable level of 10.0 dB or less for any given
single mode fiber optic link.
Budget and Propagation Delay
When you determine a maximum fiber optic cable length, you must
calculate and consider the fiber optic budget (a total loss of 10.0 dB or
less between stations) and total network propagation delay.
To determine the fiber optic budget, combine the optical loss due to the
fiber optic cable, in-line splices, and fiber optic connectors. Typical loss
for a splice and connector (together) equals 1 dB or less.
Network propagation delay is the amount of time it takes a packet to
travel from the sending device to the receiving device. Total propagation
delay for the entire network must not exceed 25.6 µs in one direction
(51.2 µs round trip). If the total propagation delay exceeds 25.6 µs, you
must use bridges or switches to re-time the signal.
Length
If you meet all system budgets, the fiber optic ports will drive the signal a
minimum distance of 5 km and comply with the IEEE 802.3 10BASE-FL
specification.
emc39bk Page 2 Monday, February 12, 1996 4:21 PM