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

A “Loss of Signal” (LOS) alarm is a critical alarm that indicates that there is no or very bad signal at the physical interface. LOS alarm is also raised when the signal level drops below the threshold, at which a high bit error rate (BER) is predicted. LOS alarm can be caused by physical damage, power outage, or misconfiguration of the equipment. LOS alarm can affect the service availability and performance of the optical network.  Therefore, it is typically assigned a critical severity level, which means that it requires immediate attention and resolution 2 . Other severity levels are major, minor, and warning, which indicate different degrees of impact and urgency of the alarms.  References :  Troubleshooting Guide for Cisco NCS 1002 ,  T1: A Survival Guide ,  M-series SONET/SDH alarms and troubleshooting tips

 The statement that an “Incoming SUPVY LOS” alarm is raised on the local node is NOT a characteristic of an Optical Supervisory Channel Loss of Signal (OSC LOS) issue, in case that no “LD Input LOS” alarms are raised against the involved amplifiers.  An “Incoming SUPVY LOS” alarm indicates that the input signal of the Optical Supervisory Channel (OSC) is lost or below the threshold 6 .  The OSC is a bidirectional channel that connects two adjacent nodes in a DWDM network and carries OAM information and other services 7 .  An OSC LOS issue can occur due to a fiber cut, a defective or dirty OSC fiber, or a faulty OSC transmitter or receiver 8 .  However, if there is no “LD Input LOS” alarm raised against the involved amplifiers, it means that there is no loss of signal on the line interface of the amplifier, which carries both service channels and OSC channels 9 .  Therefore, an “Incoming SUPVY LOS” alarm on the local node is not related to an OSC LOS issue, but rather to an OSC configuration issue or a faulty OSC card 10 .  References  :  Nokia Optical Diagnostics and Troubleshooting Course | Nokia ,  Optical User Guide - Nokia ,  Alcatel-Lucent 1830 PSS-8 and PSS-16 Photonic Service Switch

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

In bidirectional configurations, where the same fiber is used to transmit signals in both directions, power adjustments can be performed at both ingress and egress amplifiers. The ingress power adjustments are performed against the ingress amplifiers, which boost the incoming signals from the opposite direction.  The egress power adjustments are performed against the egress amplifiers, which boost the outgoing signals from the same direction 2 . Therefore, the statement A is correct.  References  :  Nokia Optical Diagnostics and Troubleshooting Course | Nokia ,  Optical amplifiers, explained by RP; optical amplification

A unidirectional amplification stage works by boosting the incoming optical signals by the ingress amplifier, while the outgoing optical signals do not pass through the ingress amplifier. This means that the ingress amplifier only amplifies the signals in one direction, hence the name unidirectional.  This configuration is typically used for point-to-point links or ring networks where bidirectional amplification is not required or desired 1 .  References  :  Nokia Optical Diagnostics and Troubleshooting Course | Nokia

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 switching 2 .  References  :  Nokia Optical Diagnostics and Troubleshooting Course | Nokia ,  Nokia 1830 Photonic Service Switch (PSS) | Nokia

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 command that should be used to configure the 10GbE client interface 1/7/C1 with a GFP-F encapsulation mode is  config interface 1/7/C1 encmode 10client gfp-f . This command will set the encapsulation mode of the interface to GFP-F, which is a frame-mapped generic framing procedure that encapsulates Ethernet frames with a GFP header. The command also specifies that the interface is a 10GbE client interface, which means that it supports 10 Gigabit Ethernet LAN signals. The other commands are incorrect because they either have invalid syntax or use incorrect parameters for the interface or the encapsulation mode.  References :  Nokia Optical Diagnostics and Troubleshooting Course ,  OAM and Diagnostics Guide

 The available output optical power range is the same as in question 5, since the EPT Power Management Report refers to the same ingress amplifier with the same settings and parameters. Therefore, the answer is also A, -0.6 to 1.72 dB.  References  :  Nokia Optical Diagnostics and Troubleshooting Course | Nokia ,  EPT Power Management Report | Nokia