4A0-265 Nokia Optical Diagnostics and Troubleshooting Exam Questions and Answers

The alarm masking mechanism is a feature of the 1830 PSS that prevents unnecessary alarms from being displayed on the GUI or forwarded to an external NMS when they are caused by a known fault or maintenance activity. For example, if an optical link is down due to a fiber cut, there is no need to show alarms for all the downstream interfaces that are affected by the link failure. The alarm masking mechanism hides these alarms until the root cause is resolved, and then shows them again if they persist. The alarm masking mechanism preserves the events’ original time stamps when it masks/shows alarms, so that when an alarm is not masked anymore, the user can see the original date and time associated with the issue. This helps to identify and troubleshoot problems more accurately and efficiently. References : Optical User Guide - Nokia, Alcatel-Lucent 1830 PSS-8 and PSS-16 Photonic Service Switch

The statement that when multiple channels pass through a shared port (for example, an amplifier line interface), the total aggregated power reflects the number of channels currently present is TRUE. This means that the more channels are present, the higher the total output power will be, and vice versa. This is because each channel contributes to the total power by its own power level, and the amplifier tries to maintain a constant gain for each channel2. Therefore, the total output power depends on both the input power and the number of channels3. References : Nokia Optical Diagnostics and Troubleshooting Course | Nokia, Optical amplifiers, explained by RP; optical amplification, Amplifier chains, explained by RP; amplifier stages, preamplifier …

On a bidirectional optical amplifier configuration, the Wavelength Tracker detection points are the LINE and SIG interfaces. The Wavelength Tracker is a feature that monitors the wavelength of each channel on the optical amplifier and provides feedback to the control system. The Wavelength Tracker can detect wavelength drifts, channel failures, or channel additions or removals on both directions of the optical amplifier. The LINE interface is the input/output port for the optical line signal, while the SIG interface is the input/output port for the optical signal from/to the transponder. The other options are incorrect because the LINEOUT and SIGOUT interfaces are not Wavelength Tracker detection points, and an optical amplifier has Wavelength Tracker detection points. References: Nokia Optical Diagnostics and Troubleshooting Course, OAM and Diagnostics Guide

The command config powermgmt egress 1/2 adjust status is used to enable or disable the power adjustment feature on the specified egress amplifier. The power adjustment feature is a function that automatically adjusts the output power of an amplifier to compensate for changes in the input power or the number of channels. This feature can be enabled or disabled on both ingress and egress amplifiers, depending on the network configuration and requirements1. Therefore, the statement C is true. References : Nokia Optical Diagnostics and Troubleshooting Course | Nokia

The recommended order for the troubleshooting steps is A, as follows:

• Retrieve the channel power trace. This step is useful to identify the affected channel and its power level, as well as to check if there are any fluctuations or anomalies in the power trace that could indicate a clock source issue1.
• Determine the active clock reference source. This step is necessary to verify which clock source is currently used by the node, and if it matches the expected configuration. The clock source can be either a local oscillator (LO) or a phase-locked loop (PLL) that synchronizes with an external reference2. The active clock source can be determined by using the command show interface ot 1/1/lineout detail3.
• Switch to alternate clock source (PF). This step is helpful to isolate the problem and confirm if the suspect PF is indeed causing the channel-related alarm. By switching to an alternate clock source, such as another PF or an external reference, the node can recover from the alarm if the original clock source was faulty4.
• Replace the suspect PF. This step is the final solution to resolve the issue and restore the normal operation of the node. The suspect PF should be replacedwith a new one that has the same specifications and configuration as the original one5. References : Nokia Optical Diagnostics and Troubleshooting Course | Nokia, Optical User Guide - Nokia, Alcatel-Lucent 1830 PSS-8 and PSS-16 Photonic Service Switch

The command show wavekey wtsource power displays a list of the expected and measured output power for the channels whose admin state is up. This command is useful to monitor the power levels of the channels that are encoded with Wave Keys, which are unique identifiers for wavelength tracking. The command output shows the channel number, wavelength, Wave Key ID, Wave Key Code, expected output power, measured output power, and power difference for each channel1. The command can be used on both OTs and amplifiers that support WT capability2. References : Nokia Optical Diagnostics and Troubleshooting Course | Nokia, Optical User Guide - Nokia

The statement that is false is that no OSC-related alarms will raise on the local node. OSC stands for Optical Supervisory Channel, which is a dedicated wavelength used for out-of-band signaling and management of optical network elements. If a node is experiencing a little unexpected attenuation over the OSC transmit direction, it means that the OSC signal is weaker than expected when it reaches the adjacent node. This can cause a “Data Link Down” alarm to raise on the adjacent node, indicating that the OSC communication link is broken or degraded. However, this can also cause an “OSC Power Low” alarm to raise on the local node, indicating that the OSC transmit power is below the threshold. Therefore, there will be OSC-related alarms on both nodes. The other statements are true because a power adjustment action will fail on the local node due to insufficient OSC power, and traffic will pass between the nodes as long as there is no other issue affecting the data channels. References: Nokia Optical Diagnostics and Troubleshooting Course, Optical Supervisory Channel Module product data sheet

A passive component in a CDC-F network configuration is the MSH4-FSB Fiber Shuffle Module. This module is used to rearrange the fibers between the CDC-F modules and the wavelength routers, so that each wavelength router can access any of the 96 wavelengths in the C-band. The MSH4-FSB module does not require any power or active components, and it does not perform any optical amplification or switching2. References : Nokia Optical Diagnostics and Troubleshooting Course | Nokia, Nokia 1830 Photonic Service Switch (PSS) | Nokia

A single directional fiber cut is occurring between two amplifiers in unidirectional configuration with Raman pump. Multiple services are crossing the affected span. The node(s) that will report an Incoming Payload LOS alarm are both Node A and Node C. An Incoming Payload LOS alarm indicates that there is no or very low signal at the input port of a node. In the exhibit, Node A will report this alarm because it will not receive any signal from Node B due to the fiber cut. Node C will also report this alarm because it will not receive any signal from Node D due to the fiber cut. The Raman pump in Node A does not prevent this alarm, as it only amplifies the signal in the forward direction, not the backward direction. The other options are incorrect because they either ignore one of the nodes that will report the alarm or assume that the Raman pump has an effect on the backward direction. References: Nokia Optical Diagnostics and Troubleshooting Course, OAM and Diagnostics Guide