Link Tuner

This chapter describes the Link Tuner optical application for Cisco NCS 1010.

Overview of Link Tuner

Link tuner computes the target Power Spectral Densities (PSD) for APC by calculating the optimal PSDs for a span. Power Spectral Density represents power per 12.5 GHz of spectrum. Link tuner is enabled if automatic link bring up is enabled.. Link tuner is span-specific and computes the target PSDs for channels entering the span. Link tuner uses the following parameters to compute the target PSD:

  • Fiber-type

  • Span loss measurement

  • Spectral density

  • Connector losses

  • Span length

  • Raman gain (only on Raman spans)

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 link tuner detects changes in the span loss, span length, or connector loss, link tuner 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. All traffic impacting actions trigger link tuner.

The following table describes the different link tuner status.

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

To view link tuner status and PSD computation information, use show olc link-tuner command.

The following sample is an output of show olc link-tuner command.

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             
To view link tuner status, PSD computation information, and computed total noise, use show olc link-tuner detail command.

The following sample is an output of show olc link-tuner detail command.

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         


You can view the target PSDs configured for all setpoints using the show olc apc-local target-psd-profile command. The output shows the source of the PSD configuration also. The target PSD source can be Link Tuner or Configuration.

The following sample is an output of show olc apc-local target-psd-profile command.

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             

Configure Link Tuner

The following configurations are available for the link tuner:

Enable Link Tuner

You can enable link tuner for a controller. Use the following commands to enable link tuner.

configure

optical-line-control

controller ots Rack/Slot/Instance/Port

link-tuner enable

commit

end

The following is a sample configuration that enables link tuner.

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

Disable Link Tuner

You can disable link tuner for a controller. Use the following commands to disable link tuner.

configure

optical-line-control

controller ots Rack/Slot/Instance/Port

link-tuner disable

commit

end

The following is a sample configuration that disables link tuner.

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 disable
RP/0/RP0/CPU0:ios(config-olc-ots)#commit
RP/0/RP0/CPU0:ios(config-olc-ots)#end

Configure Link Parameters

Configure fiber-type, spectrum density, connector losses, and span length for accurate link tuning.

To configure fiber type, use fiber-type command. SMF is the default fiber-type.

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

  • E-LEAF

  • FREE-LIGHT

  • METRO-CORE

  • SMF

  • SMF-28E

  • TERA-LIGHT

  • TW-RS

  • TW-Reach

  • TW-minus

  • TW-plus

  • ULL-SMF28

To configure spectrum density, use link-tuner spectrum-density command. You can configure a spectrum density as a percentage value in the range of 1-100. The default spectrum density is 81.

To configure connector loss, use the connector-loss command. You can configure Tx and Rx connector loss in the range 0–20 dB. The default connector loss is:

  • 0.25 dB for ports without Raman module

  • 0.3 dB for ports with Raman module

To configure span length, use the span-length command. You can configure span length in the range of 0.1 to 200 km as multiples of 0.1 km. In the absence of span length configuration, link tuner computes span length using span loss.

The following example is a sample configuration that configures the link tuner parameters.

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