Specifications

1-54
Cisco ONS 15454 Troubleshooting and Maintenance Guide
November 2001
Chapter 1 Alarm Troubleshooting
1.3.75 LOS (BITS)
• Major, Service affecting
The TCC+ card has a loss of signal (LOS) condition from the BITS timing source. An LOS occurs when
a SONET receiver detects an all-zero pattern for 10 microseconds or longer. An LOS (BITS-N) means
the BITS clock or the connection to the BITS clock failed.
Caution Always use the supplied electrostatic discharge wristband when working with a powered ONS 15454.
Plug the wristband cable into the ESD jack located on the lower-right outside edge of the shelf
assembly.
Procedure: Clear the LOS Alarm
Step 1 Verify the wiring connection from the ONS 15454 backplane BITS clock pin fields to the timing source.
Step 2 Check that the BITS clock is operating properly.
1.3.76 LOS (OC-N)
• Critical, Service affecting
A port on the reporting OC-N card has a loss of signal (LOS) condition. An LOS occurs when a SONET
receiver detects an all-zero pattern for 10 microseconds or longer. An LOS means the upstream
transmitter has failed. If an OC-N LOS alarm is not accompanied by additional alarms, a fiber break is
usually the cause of the alarm. The condition clears when two consecutive valid frames are received.
Warning Invisible laser radiation may be emitted from the aperture ports of the single-mode fiber optic
modules when no cable is connected. Avoid exposure and do not stare into open apertures.
Caution Always use the supplied electrostatic discharge wristband when working with a powered ONS 15454.
Plug the wristband cable into the ESD jack located on the lower-right outside edge of the shelf
assembly.
Procedure: Clear the LOS Alarm on an OC-N Card
Step 1 Verify fiber continuity to the port.
Step 2 Verify that the correct port is in-service.
Step 3 Use an optical test set to verify that a valid signal exists on the line.
Test the line as close to the receiving card as possible.
Step 4 Clean the fiber:
a. Clean fiber according to local site practice.