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SEHI100TX User’s Guide 3-3
Propagation Delay
Propagation delay is the amount of time it takes data to travel from the
sending device to the receiving device. Total propagation delay allowed
for the network is 256 bit times (2.56 µs) in one direction (5.12 µs round
trip). If the total propagation delay between any two nodes on the network
exceeds 2.56 µs, then use bridges or other devices to further segment the
network.
Temperature
The attenuation of PVC insulated cable varies significantly with
temperature. At temperatures greater than 40°C (104°F), Cabletron
Systems recommends the use of plenum-rated cables to ensure that cable
attenuation remains within specification.
3.1.3 Multimode Specifications for the EPIM-100FX
The SEHI supports the Cabletron Systems EPIM-100FX. The
EPIM-100FX meets IEEE 802.3u standards. When connecting a fiber
optic segment to the SEHI EPIM-100FX module, the network must meet
the following requirements:
Cable Loss
Test the fiber optic cable with a fiber optic attenuation test set adjusted for
an 850 nm wavelength. This test verifies that the signal loss in a cable is
within an acceptable level. The maximum loss for a multimode fiber optic
cable is 11.0 dB.
Fiber Optic Budget and Propagation Delay
Determine the maximum fiber optic cable length by calculating the fiber
optic budget delay and total network propagation before fiber optic cable
runs are incorporated in any network design.
Fiber optic budget is the combination of the optical loss due to the fiber
optic cable, in-line splices, and fiber optic connectors.
Propagation delay (collision delay) is the amount of time it takes data to
travel from the sending device to the receiving device. Total propagation
delay allowed for the entire network is 256 bit times (2.56 µs) in one
direction (5.12 µs round trip). If the total propagation delay between any
two nodes on the network exceeds 2.56 µs, then use bridges or other
devices to further segment the network.
SEHI Book Page 3 Wednesday, May 15, 1996 10:42 AM