The Nokia Optical Diagnostics and Troubleshooting Exam (4A0-265)

The available output optical power range is the difference between the maximum gain and the minimum gain range of the ingress amplifier. According to the EPT Power Management Report, the maximum gain is 25.7 dB and the minimum gain range is 14 dB. Therefore, the available output optical power range is 25.7 - 14 = 11.7 dB. To convert this to a logarithmic scale, we use the formula 10^(x/10), where x is the value in dB. Therefore, the available output optical power range in logarithmic scale is 10^(11.7/10) - 10^(14/10) = 14.68 - 25.12 = -0.6 to 1.72 dB.  References  :  Nokia Optical Diagnostics and Troubleshooting Course | Nokia ,  EPT Power Management Report | Nokia

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 channel 1 .  The command can be used on both OTs and amplifiers that support WT capability 2 .  References  :  Nokia Optical Diagnostics and Troubleshooting Course | Nokia ,  Optical User Guide - Nokia

The calculated span loss from Node A to Node B is 10.0 dB. Span loss is the difference between the optical power transmitted and received at two points in a network. It can be calculated by subtracting the received power from the transmitted power. In the exhibit, the transmitted power from Node A to Node B is +7.5 dBm, and the received power at Node B from Node A is -2.5 dBm. Therefore, the span loss is +7.5 dBm - (-2.5 dBm) = 10.0 dB. The other options are incorrect because they do not match the calculation.  References :  Nokia Optical Diagnostics and Troubleshooting Course ,  Pluggable Optical Modules: Transceivers for the Cisco ONS Family Data Sheet

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 issue 1 .

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 reference 2 .  The active clock source can be determined by using the command  show interface ot 1/1/lineout detail 3 .

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 faulty 4 .

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 replaced with a new one that has the same specifications and configuration as the original one 5 .  References  :  Nokia Optical Diagnostics and Troubleshooting Course | Nokia ,  Optical User Guide - Nokia ,  Alcatel-Lucent 1830 PSS-8 and PSS-16 Photonic Service Switch

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 threshold 3 . 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

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

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

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 that the user should enter to retrieve the OSC pluggable module type is  show interface 1/13/OSCSFP detail . This command will display detailed information about the OSC interface on slot 1/13, including the type of pluggable module that is installed in it. The pluggable module type can be either SFP or SFP+, depending on the speed and distance requirements of the OSC link. The command will also show other parameters, such as wavelength, frequency, transmit power, receive power, and status. The other commands are incorrect because they either do not show the pluggable module type or have invalid syntax.  References :  Nokia Optical Diagnostics and Troubleshooting Course ,  OSFP OCTAL SMALL FORM FACTOR PLUGGABLE MODULE