Alcatel-Lucent 9500 MXC User Manual page 643

Measuring the Fade Margin
3DB 23063 ADAA - Rev 004 July 2007
When coupled with an ability to measure receive signal level at the receiver
input, this procedure also provides an indication of receiver threshold, which can
be checked against receiver specifications.
For 9500 MXC, a fade margin test involves reducing the Tx power at one end of
the link, and checking the error performance at the other using the G.826 data
presented in the CT Performance Screen. However, achieving a threshold RSL is
only possible where there is sufficient adjustment available in Tx power.
• Tx power adjustment ranges apply down from the maximum power setting
supported by the frequency and bandwidth option configured for the link.
• Therefore, in situations where the expected fade margin is greater than the Tx
power-reduction range available within CT, it is not possible to reach threshold.
Nevertheless, reducing Tx power to its minimum and confirming error-free
operation should still provide an acceptable degree of confidence.
The CT screens used are:
• Configuration > Plug-ins > Link for Tx power and ATPC control.
• Diagnostics > Performance > Link for RSL and G.826 error data.
• Diagnostics > System Controls > Link to lock a protected link to one side.
To measure the fade margin:
1. Ensure ATPC is not selected, and for a protected link, force (lock) the link to
one side.
2. Note the Tx power setting, and the detected Tx power reading at one end of
the link.
3. Note the RSL at the other end of the link.
4. Prepare to monitor errored seconds in the receive-end Performance screen.
Alternatively, use a BER test on a looped tributary.
5. Reduce the Tx power in steps until the receiver threshold is reached as
indicated by the onset of errored seconds.
6. The fade margin is the difference in Tx power between the normal power and
the power at Rx threshold.
7. At threshold, the indicated receiver RSL in dBm can also be compared with
the receiver datasheet specifications as a direct check of receiver threshold.
9500 MXC User Manual
Vol. V-1-5