BRX-XLR User Guide
34
180-0145-001-R05
6. The DSLAM and CPE successfully
establish synchronization but the
actual SNR is too low
Adjust the DSLAM configuration for the target
and minimum SNR in the downstream and
upstream directions
7. After inserting a BRX-XLR on a
copper loop, the performance of
other ADSL2+ / ADSL pairs in the
same binder is negatively impacted
The BRX-XLR does impact adjacent copper pairs in
the same binder when some pairs downstream from
the location of the BRX-XLR are not amplified.
Although the amplified signal from the BRX-XLR is
fully compliant with the allowed spectrum mask
defined for ADSL and ADSL2+, the interference is the
result of the amplified signal impacting the weaker
signal from the DSLAM on adjacent pairs not
amplified with a BRX-XLR. It is HIGHLY
recommended to amplify all pairs beyond the
installation point of the BRX-XLR.
8. The performance of the pairs is
unstable
Check for potential non-DMT signals in the binder
such as T1 or E1, HDSL, SHDSL.
The presence of these disturbers is known to
negatively impact the performance of ADSL and
ADSL2+ and the disturbance should have been there
prior to the installation of the BRX-XLR.
If you believe that the instability is the result of the
installation of the BRX-XLR, please refer to the other
problems covered in this table for the more likely
source of the issue and the steps to remediate it.
C. Power issues
9. The BRX-XLR unit does not seem to
power up
Verify that DSLAM and CPE pairs are not
mistakenly swapped. Only the pair labelled
DSLAM can be used to power the BRX-XLR
device.
Verify that there is POTS voltage (-40VDC to
-60VDC) on the DSLAM pair to power the BRX-
XLR.
With the POTS circuit in the ON-HOOK state, the
voltage measured between TIP and RING on the
DSLAM pair at the BRX-XLR should be greater
than |35Vdc|.
If any of these measurements are not met, you
should make the corrections as per your corporate
standard procedure and re-verify.
D. Pair Bonding issues
10. With the BRX-XLR installed on 2
pairs, the DSLAM and CPE can’t
achieve the expected bandwidth
(downstream and/or upstream)
Verify the DSLAM settings for each pair in the
bonding group and make sure they are the same
Verify the loop length of each pair. Significant
differences between pairs will induce
jitter/latency which will impact the achievable
total bandwidth
All pairs in the bonding group need to be
