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

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

A “Loss too low” message can be displayed after a power adjustment has been provided if there is an issue with unstable optical power levels. Unstable optical power levels can be caused by various factors, such as environmental conditions, fiber aging, equipment malfunction, or configuration errors. Unstable optical power levels can affect the accuracy and reliability of the power adjustment process, which relies on measuring the optical loss between two points in the network. A “Loss too low” message means that the measured optical loss is lower than the expected value, which can indicate a problem with the optical signal quality or integrity. The other issues are incorrect because they either cause a different type of message or do not affect the power adjustment process. References: Nokia Optical Diagnostics and Troubleshooting Course, OAM and Diagnostics Guide

The statement that WT uses a unique identifier based on a pair of numbers encoded by Optical Transponders (OTs) into each service wavelength direction is TRUE. WT is a feature of the 1830 PSS that allows for automatic identification and tracking of wavelengths across different network elements and domains. WT uses Wave Keys, which are unique identifiers composed of two numbers: a Wave Key ID and a Wave Key Code. The Wave Key ID identifies the OT that generates the wavelength, while the Wave Key Code identifies the wavelength itself within a given OT6. The Wave Keys are encoded by OTs into each service wavelength direction using phase modulation, and can be decoded by other OTs or amplifiers that have WT capability. WT enables various applications and benefits, such as simplified commissioning, automated wavelength routing, enhanced fault localization, and improved network security. 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 wtmonitor 1/6/LINE summary displays a list of all channels detected against the selected interface (in and out); it shows if a Wave Keys pair is expected, if a Wave Keys pair is received, and if the received Wave Keys pair is unexpected. A Wave Keys pair is a pair of unique identifiers that are transmitted along with an optical channel to provide channel identification and monitoring functions. The command can be used to verify the presence and correctness of the Wave Keys pairs on an interface and to detect any mismatch or misconfiguration. The other options are incorrect because they either describe a different command or provide incorrect information. References: Nokia Optical Diagnostics and Troubleshooting Course, OAM and Diagnostics Guide

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

 A Threshold Crossing Alert (TCA) alarm is a type of alarm that indicates that a monitored parameter has crossed a predefined threshold. For example, a TCA alarm can be triggered when the optical power received at a port is too high or too low. The default severity level for a TCA alarm is warning, which means that it does not affect the service but may require attention. The other severity levels are critical, major, and minor, which indicate different degrees of impact and urgency of the alarms. The severity level of a TCA alarm can be changed by the user using the Nokia 1830 Engineering and Planning Tool (EPT) or the Nokia 1350 Optical Management System (OMS). References: Nokia Optical Diagnostics and Troubleshooting Course, Nokia 1830 PSS-32 and PSS-16 Photonic Service Switch Release 8.0 Alarms and Conditions Reference Guide

The exhibit shows a diagram of an OT module with a client port and a DWDM port. The client port is looped back to itself with an OEO (Optical-Electrical-Optical) device. This means that the signal received by the client port is converted to an electrical signal, then back to an optical signal, and then transmitted back to the same port. This type of loopback is called a client portterminal loopback. It is used to test the functionality of the client port without involving the DWDM port or any other network element4. A client port facility loopback would involve looping back the signal from the DWDM port to the client port. A line port facility loopback would involve looping back the signal from another OT module or network element to the DWDM port. A line port terminal loopback would involve looping back the signal from the DWDM port to itself5. References : Nokia Optical Diagnostics and Troubleshooting Course | Nokia, Loopback - Wikipedia