Configuration Guide for Cisco NCS 1014, IOS XR Releases 26.x.x

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Configuration Guide for Cisco NCS 1014, IOS XR Releases 26.x.x

OTDR baseline

Updated: June 18, 2026

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This section explains what an OTDR baseline is, its key attributes, and its role in maintaining and troubleshooting optical networks.

Table 1. Feature History Table

Feature Name

Release Information

Description

OTDR baseline

Cisco IOS XR Release 25.2.1

OTDR saves a baseline with the scan results the first time a link is up. This baseline captures essential data about the fiber characteristics at the time of initial installation. The baseline is used as a benchmark for future OTDR scans to identify changes or degradation in the optical fiber span, facilitating maintenance and troubleshooting efforts. It helps verify the integrity and performance of the optical network over time.

An OTDR baseline is the initial set of OTDR scan results that are saved as a reference point for evaluating the condition and performance of an optical fiber span over time. It captures essential data about the fiber characteristics at the time of initial installation or configuration, including:

  • SOR filename: The filename of the SOR file that documents the scan results.

  • Optical Return Loss (ORL): Measurement of the reflected optical power, indicating the quality of the fiber connection.

  • Detected events: Any anomalies, reflections, or changes detected during the scan, such as splices, bends, or breaks.

  • Scan timestamp: The specific date and time when the baseline scan was performed.

You can find the OTDR baseline SOR files in the /harddisk:/otdr/baseline directory.

Purpose of the baseline

The baseline is used as a benchmark for future OTDR scans to identify changes or degradation in the optical fiber span, facilitating maintenance and troubleshooting efforts. It helps verify the integrity and performance of the optical network over time.

Baseline creation

  • The OTDR baseline is saved after the automatic OTDR scan when the link is up for the first time.

  • If the OTDR-ABS-REFLECTANCE-EXCEEDED-TX or OTDR-ABS-REFLECTANCE-EXCEEDED-RX alarms are active on a link, the OTDR baseline is not saved. In such cases, clear the alarm and save the baseline manually.

Baseline storage location

Save a new OTDR baseline

Set the current OTDR scan results as a baseline in these situations.

  • The OTDR-ABS-REFLECTANCE-EXCEEDED alarm is active. The system did not save the baseline during the initial scan.

  • OTDR scan status is:

    • Unknown

    • Stopped, or

    • Error

  • If you upgrade or expand the network, you may need to save a new baseline.

You must run an OTDR scan again to save a new baseline.

Procedure

1.

Use the otdr-start controller ots R/S/I/P rx|tx command to start the OTDR scan manually

Example:

RP/0/RP0/CPU0:ios#otdr-start controller ots 0/0/0/0 rx
Wed Feb 9 05:49:39.178 UTC
OTS OTDR Scan Started at RX
2.

Use the otdr save baseline controller ots R/S/I/P rx|tx command to set the current OTDR scan results as the baseline.

Example:

RP/0/RP0/CPU0:ios#otdr save baseline controller ots 0/0/0/0 rx

Example:

This sample output is an example of a failure to save a baseline.

RP/0/RP0/CPU0:P2B_DT_04#otdr save baseline controller ots 0/0/0/0 tx
Thu Apr  3 17:38:02.833 +0530
'optics' detected the 'warning' condition 'OTDR baseline cannot be saved due to unavailability of scan results'

The system saves the current OTDR scan as the new baseline. If scan results are unavailable, the system displays an error and the baseline is not saved.

View OTDR baseline

Follow this step to view the OTDR baseline.

Procedure

Enter the show controller ots R/S/I/P  otdr-info tx|rx  baseline command to view the OTDR baseline.

Example:

RP/0/RP0/CPU0:ios#show controller ots 0/1/0/0 otdr-info rx baseline 
Mon May 19 16:27:41.912 IST

        Display Baseline Info: 

        Scan Direction: RX

        Scan Status: Data Ready 

        Optical Return Loss: 48.0 dB

        SOR file: /harddisk:/otdr/baseline/kepler-230-220_OTDR_Ots0_1_0_0_RX_20250319-093155.sor

        Total Events detected: 6

        Scan Timestamp: Wed Mar 19 09:29:19 2025 UTC

        Event Type Legend:  NR:Non-Reflective  R:Reflective  FE:Fiber-End  ER:Excess-Reflection EA:Excess-Attenuation

        Event#      |  Detected Event(s)       |  Location(m)     |  Accuracy(m)     |  Magnitude(dB)   |  Attenuation/km(dB)
        1           |  NR EA                   |  2106.8600       |  34.44           |  24.48           |  0.00            
        2           |  NR                      |  5250.7200       |  501.86          |  1.17            |  0.14            
        3           |  NR                      |  6416.0500       |  501.86          |  0.39            |  0.30            
        4           |  NR                      |  10208.9400      |  501.86          |  2.54            |  0.00            
        5           |  R FE                    |  22424.7200      |  1000.78         |  -26.08          |  0.14            
        6           |  NR FE                   |  22424.7200      |  4756.43         |  3.50            |  0.14