3Com CoreBuilder 3500 Installation Manual page 8

8 70-km Gigabit Ethernet GBIC Transceiver Installation Guide
Calculating the Link
Budget for the 70-km
GBIC Transceiver
Incorrect Value in the Ethernet Display Field (CoreBuilder 3500)
An incorrect value appears in the Ethernet display field when all of these
conditions are true:
Your CoreBuilder 3500 is running system software at Release 2.1 or
earlier.
You have installed or reinstalled a new or replacement GBIC (for
example, Model Number 3CGBIC91, 3CGBIC92 or 3CGBIC97).
You enter the
ethernet summary
for the first time.
When all of these conditions are true, the text
appears in the
portType
GBIC is qualified and functions properly. Disregard this incorrect value.
The 70-km GBIC has an optical budget of 20 dB and operates at a
wavelength of 1550 nm. Calculate potential link distances as follows:
Minimum launch power is –4 dBm.
Minimum receive sensitivity is –24 dBm.
The optical budget is arrived at by subtracting the minimum receive
sensitivity of –24 dBm from the minimum launch power of –4 dBm,
which yields an optical budget of 20 dB.
Allow 0.25 dB attenuation per kilometer of single-mode fiber at
1550 nm.
Allow 0.5 dB attenuation per mating connector.
or the
ethernet detail
field of the Ethernet display even though the
command
(GBIC) Non-qualified