Cabletron Systems SEH-22 Manual De Usuario

A-7

The following subsections provide cable specifications for the various 
EPIMs use in the SEH.

Table A-1 shows Multimode Fiber Optic Cable specifications for the 
EPIM-F1 and EPIM-F2 modules.

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. Table A-1 shows the attenuation for each 
Multimode cable type.

When determining the maximum fiber optic cable length, take into 
consideration 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 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 must not exceed 25.6 

µ

s in one direction (51.2 

µ

s 

round trip). If the total propagation delay between any two nodes on the 
network exceeds 25.6 

µ

s, use bridges.

Table A-1. Multimode Fiber Optic Cable Specifications

50/125 

µ

m

13.0 dB or less

The maximum allowable fiber 
optic cable length is 2 km 
(2187.2 yds). However, IEEE 
802.3 specifications allow for a
maximum of 1 km (1093.6 yds).

62.5/125 

µ

m

16.0 dB or less

100/140 

µ

m

19.0 dB or less

SEH Book  Page 7  Tuesday, March 19, 1996  4:12 PM