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

When troubleshooting possible generic fiber cuts, the recommended first step is to review alarms at nodes where power loss occurs. This can help identify the location and extent of the fiber cut and the affected services. The next recommended step is to perform network power traces to attempt to determine the point of power loss. Network power traces are graphical representations of the optical power levels along a span or a path. They can be used to compare the measured power levels with the expected power levels and to pinpoint any significant deviations or drops that indicate a fiber cut. The other options are incorrect because they either do not help locate the fiber cut or are not as effective as network power traces. References: Nokia Optical Diagnostics and Troubleshooting Course, OAM and Diagnostics Guide

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 …

A power adjustment has succeeded conditionally because of gain settings set to higher levels than expected by design. This means that the optical power levels of the amplifier have been adjusted within the acceptable range, but the gain values are higher than the design values. This can cause a performance degradation or instability of the optical signal. The alarm that will raise in this case is “Amplifier Gain Tilt Adjustments Suspended” (PWRTILTSUSP). This alarm indicates that the gain tilt adjustments, which are used to compensate for the wavelength-dependent loss of the optical signal, have been suspended due to high gain values. The alarm also suggests lowering the gain values manually or using the EPT tool. The other alarms are incorrect because they either indicate a different type of power adjustment issue or do not exist. References: Nokia Optical Diagnostics and Troubleshooting Course, OAM and Diagnostics Guide

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

The recommended order for the troubleshooting steps is B, 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 channel absent issue1.

Retrieve the cross-connection (XC) details and see what Wave Keys should be present. This step is necessary to verify which Wave Keys are expected to be present on the node, card, and port based on the XC configuration2. Wave Keys are unique identifiers for wavelength tracking that are encoded by Optical Transponders (OTs) into each service wavelength direction3.

Go to the suspected troubled node / card / port and look at Wave Keys (in / out). This step is helpful to compare the observed Wave Keys with the expected Wave Keys, and to locate the source of the problem. If a Wave Key is missing or mismatched, it means that there is a channel absent issue on that node, card, or port4.

Check observed Wave Keys against expected Wave Keys. This step is the final solution to resolve the issue and restore the normal operation of the node. The observed Wave Keys should match the expected Wave Keys based on the XC configuration. If not, the XC configuration should be corrected or the faulty node, card, or port should be replaced5. References : Nokia Optical Diagnostics and Troubleshooting Course | Nokia, Optical User Guide - Nokia, Alcatel-Lucent 1830 PSS-8 and PSS-16 Photonic Service Switch

1-Day PMs are one of the types of PM data that can be retrieved from an optical network element. 1-Day PMs show measurements collected over the preceding 24 hours, with each hour being a bin. Up to 8 bins are available for data storing, which means that only the most recent 8 hours of data can be accessed. The other types of PM data are 15-Minute PMs, which show measurements collected over the preceding 15 minutes, with each minute being a bin, and Total PMs, which show measurements collected since the last reset of the PM counters. References: Nokia Optical Diagnostics and Troubleshooting Course, Nokia 1830 PSS-32 and PSS-16 Photonic Service Switch Release 8.0 Performance Monitoring Reference 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 exhibit shows a diagram of a network of nodes and edges, where a single directional fiber cut is occurring between two amplifiers in bidirectional configuration. The node that will report a “LD Input LOS” alarm is node B only. A “LD Input LOS” alarm indicates that the input signal to the laser diode (LD) of an amplifier is lost or below the threshold3. In this case, node B will not receive any signal from node A due to the fiber cut, and will generate this alarm. Node A will not report this alarm, because it can still receive a signal from node C through the other fiber. Node C will not report this alarm either, because it is not directly affected by the fiber cut between node A and node B. References : Nokia Optical Diagnostics and Troubleshooting Course | Nokia, Troubleshooting Guide for Synchronous Digital Hierarchy - Cisco

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