Cable Fault Isolation; Method 1: By Inference - HP 27115A Installation Manual

Table 3-3. LED Pattern on a Good PCA with a Loopback Cable Installed
LED
(color) Pattern Meaning
Self-test (red) off On-board self-test passed
C (red) on Normal result of
S (red) off self-test with loopback
R (red) off cable installed.
P (green)
onlblinking The
peA
is operational.
A (green) blinking The
peA
shows activity, requests remote
ID
value.
Note
Successfulloopback fiber tests may not mean the
peA
is good - a marginal
transmitter or receiver may go undetected. See the "Fault Not Found" section
later in this chapter.
Cable Fault Isolation
If the
peA
passes the self-test using the loopback cable, check the installed
duplex cable. You can check the duplex cable for damage in a variety of ways.
The method you use depends on what tools are available to you.
Method 1: By Inference
The simplest method to test the duplex cable is by inference. If either device on
the cable indicates a fault when connected (the S or R
LED
remains on after
self-test), but both devices operate properly when individually tested with a
loopback cable, then you can logically conclude the duplex cable is faulty.
(However, this may not be true with a marginal optical transmitter or receiver
on the
peA
or remote device.)
• To test the
HP-FL peA,
use the
peA
fault isolation procedure - with the
loopback cable - described above.
• To test the remote device's interface with a loopback cable, refer to the
applicable device service manual.
Troubleshooting and Diagnostics 3-11