Cisco NCS 1010 Optical Applications Configuration Guide, IOS XR Release 25.x.x

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Link tuner

Updated: February 5, 2026

Overview

This topic explains the parameters, operational status values, and important considerations for the link tuner application used in network spans. It provides details on how the link tuner computes Power Spectral Densities (PSDs) and outlines its status indicators and operational requirements.

Link tuner computes the target Power Spectral Densities (PSD) for APC by calculating the optimal PSDs for a span. PSD represents the power for each 12.5 GHz segment of the spectrum. Link tuner is enabled if automatic link bring up is enabled. It is specific to the span and computes the target PSDs for channels entering the span.

Parameters used by link tuner

Link tuner uses these parameters to compute the target PSD:

  • Fiber type

  • Span loss measurement

  • Spectral density

  • Connector losses

  • Span length, and

  • Raman gain (only on Raman spans).

Link tuner status

This table describes the different link tuner status values.

Table 1. Link tuner status
Status Description
Operational The link tuner is active and operational.
Blocked The link tuner is active but unable to compute target PSDs and noise.
Disabled The link tuner is disabled.

Operational considerations

The link tuner application finds the target PSD for the best performance for channels entering a span. You have to manually configure drop-psd. The drop-psd is the target PSD for OLT drop ports.

Link tuner monitors the span loss and total noise in the link. When the link tuner detects changes in span loss, span length, or connector loss, it recomputes the target PSDs. However, it applies the new target PSDs only if it detects a change of 0.1 dB or more in the total noise value.

Link tuner computes the target PSDs and total noise whenever a link goes down and comes back up. Any action that impacts traffic triggers the link tuner.

From Cisco IOS XR Release 7.9.1, NCS 1010 supports C+L band networks. In Cisco IOS XR Release 7.9.1, link tuner support is not available for C+L band networks. In Cisco IOS XR Release 7.9.1, link tuner is available only for C band only networks. If you are deploying a C+L band configuration for your network, you can obtain the PSD profiles (single band and dual band) from Cisco Optical Network Planner.

Use this task to control whether the link tuner application on the optical line controller is activated or deactivated.

Procedure

Use the link-tuner enable command to enable the link tuner.

Example:


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:ios(config)#optical-line-control 
RP/0/RP0/CPU0:ios(config-olc)#controller ots 0/0/0/0
RP/0/RP0/CPU0:ios(config-olc-ots)#link-tuner enable
RP/0/RP0/CPU0:ios(config-olc-ots)#commit
RP/0/RP0/CPU0:ios(config-olc-ots)#end

Use the link tuner disable command to disable the link tuner.

Use this task to set the necessary parameters for accurate link tuning in the link tuner application.

Use the fiber-type command to configure the fiber type. SMF is the default fiber type.

You can configure these fiber types using the fiber-type command:

  • E-LEAF

  • FREE-LIGHT

  • METRO-CORE

  • SMF

  • SMF-28E

  • TERA-LIGHT

  • TW-RS

  • TW-Reach

  • TW-minus

Use the link-tuner spectrum-density command to configure the spectrum density. You can configure a spectrum density as a percentage value from 1 to 100. The default value is 81.

Use the connector-loss command to configure the connector loss for both the Tx and Rx ports. The supported range for each port is 0 to 20 dB.

The default connector loss is

  • 0.25 dB for ports without Raman module.

  • 0.3 dB for ports with Raman module.

Use the span-length command to configure the span length. You can specify a value from 0.1 km to 200 km in increments of 0.1 km. If you do not configure the span length, the link tuner calculates the span length based on span loss.

Procedure

Use these commands to configure the link tuner parameters.

Example:


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:ios(config)#optical-line-control 
RP/0/RP0/CPU0:ios(config-olc)#controller ots 0/0/0/0
RP/0/RP0/CPU0:ios(config-olc-ots)#fiber-type SMF
RP/0/RP0/CPU0:ios(config-olc-ots)#link-tuner spectrum-density 80
RP/0/RP0/CPU0:ios(config-olc-ots)#connector-loss rx 1
RP/0/RP0/CPU0:ios(config-olc-ots)#connector-loss tx 1
RP/0/RP0/CPU0:ios(config-olc-ots)#span-length 100
RP/0/RP0/CPU0:ios(config-olc-ots)#commit
RP/0/RP0/CPU0:ios(config-olc-ots)#end

When you configure the fiber type, spectrum density, connector losses, and span length, the link tuner calculates the target PSDs for the span. This calculation helps optimize channel performance by selecting the best PSD values based on your settings.

Use this task to view key link tuner operational parameters and power spectral density (PSD) details for optical links.

Procedure

1.

Use the show olc link-tuner command to view the link tuner status and PSD computation information.

Example:

RP/0/RP0/CPU0:ios#show olc link-tuner 
Controller          : Ots0/0/0/0
Link Tuner Status   : OPERATIONAL
Last PSD computation: 2022-05-06 10:59:51
----------------------------------------------------------------------
Setpoint            : Computed PSD
                     (dBm/12.5 GHz)
---------------------------s-------------------------------------------
01                    -5.7             
02                    -5.6             
03                    -5.6             
04                    -5.5             
05                    -5.5             
06                    -5.4             
07                    -5.4             
08                    -5.3             
09                    -5.3             
10                    -5.2             
11                    -5.2             
12                    -5.1             
13                    -5.1             
14                    -5.0             
15                    -5.0             
16                    -4.9             
17                    -4.9             
18                    -4.8             
19                    -4.8             
20                    -4.7             
21                    -4.7             
22                    -4.6             
23                    -4.6             
24                    -4.5             
25                    -4.4             
26                    -4.4             
27                    -4.3             
28                    -4.3             
29                    -4.2             
30                    -4.2             
31                    -4.1             
32                    -4.1             
33                    -4.0
2.

Use the show olc link-tuner detail command to view the link tuner status, PSD computation information, and computed total noise.

Example:

RP/0/RP0/CPU0:ios#show olc link-tuner detail
Controller          : Ots0/0/0/0
Link Tuner Status   : OPERATIONAL
Last PSD computation: 2022-05-06 10:59:51
Computed Total Noise: -35.4 dB
----------------------------------------------------------------------
Setpoint            : Computed PSD
                     (dBm/12.5 GHz)
----------------------------------------------------------------------
01                    -5.7             
02                    -5.6             
03                    -5.6             
04                    -5.5             
05                    -5.5             
06                    -5.4             
07                    -5.4             
08                    -5.3             
09                    -5.3             
10                    -5.2             
11                    -5.2             
12                    -5.1             
13                    -5.1             
14                    -5.0             
15                    -5.0             
16                    -4.9             
17                    -4.9             
18                    -4.8             
19                    -4.8             
20                    -4.7             
21                    -4.7             
22                    -4.6             
23                    -4.6             
24                    -4.5             
25                    -4.4             
26                    -4.4             
27                    -4.3             
28                    -4.3             
29                    -4.2             
30                    -4.2             
31                    -4.1             
32                    -4.1             
33                    -4.0
3.

Use the show olc apc-local target-psd-profile command to view the target PSDs configured for all the setpoints. The output also shows the source of the PSD configuration. The target PSD source can be link tuner or configuration.

Example:

RP/0/RP0/CPU0:ios#show olc apc-local target-psd-profile 
Mon Jun 20 06:40:32.779 UTC
Controller          : Ots0/0/0/0
Target PSD source   : Link Tuner
-------------------------------------------------------------------------------
Setpoint                Frequency                        Target PSD             
                          (THz)                        (dBm/12.5 GHz)            
-------------------------------------------------------------------------------
01                    191.337494                           -6.3             
02                    191.488495                           -6.3             
03                    191.639496                           -6.2             
04                    191.790497                           -6.2             
05                    191.941498                           -6.2             
06                    192.092499                           -6.1             
07                    192.243500                           -6.1             
08                    192.394501                           -6.1             
09                    192.545502                           -6.0             
10                    192.696503                           -6.0             
11                    192.847504                           -5.9             
12                    192.998505                           -5.9             
13                    193.149506                           -5.8             
14                    193.300507                           -5.8             
15                    193.451508                           -5.8             
16                    193.602493                           -5.7             
17                    193.753494                           -5.7             
18                    193.904495                           -5.7             
19                    194.055496                           -5.6             
20                    194.206497                           -5.6             
21                    194.357498                           -5.5             
22                    194.508499                           -5.5             
23                    194.659500                           -5.5             
24                    194.810501                           -5.4             
25                    194.961502                           -5.4             
26                    195.112503                           -5.3             
27                    195.263504                           -5.3             
28                    195.414505                           -5.3             
29                    195.565506                           -5.2             
30                    195.716507                           -5.2             
31                    195.867493                           -5.1             
32                    196.018494                           -5.1             
33                    196.169495                           -5.1