Cisco NCS 1010 and NCS 1020 Datapath Configuration Guide, IOS XR Releases 26.x.x

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Optical channel monitoring

Updated: June 19, 2026

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This section explains how ASE loads are used to stabilize optical transmission systems by filling the spectrum when channels are unavailable.

The Optical Channel Monitor (OCM) blocks in the OLT and ILA cards provide perchannel optical power monitoring.

Each OCM refreshes approximately every 200ms. The device reports the channel power based on the OCM power. If the channel power is above the threshold (TH), the channel is declared as Active. If the channel power is below the threshold (TH), the channel is declared as Failed. The dynamic OCM scheduling algorithm creates a list of OCM ports based on the used and unused add/drop ports. Each add/drop port is connected to an OCM port. When creating a cross-connect, the used add/drop port is considered as a used OCM port, and the rest of the ports are considered as unused. Based on the used add/drop ports, the device creates a sequence of used and unused OCM ports. This allows the used OCM ports to refresh the maximum number of times. This approach ensures faster channel recovery.

OCM in OLT-C

The OLT-C card has a single OCM device with 37 OCM measuring points (OCM1 - OCM37). You can read the OCM data for all the OCM blocks through the IOS-XR commands, except OCM1, OCM4, and OCM7.

The measuring points in the OLT-C card are:

  • LINE-TX

  • LINE-RX

  • 2x33 ports of WSS in the multiplexer section of the OLT-C card

See OLT Functional Layout for details of the ports.

Table 1. Optical specifications for OCM in OLT-C
Parameter Unit Minimum Typical Maximum Note
Dynamic ranges dBm/12.5GHz –10 10 Ports: LINE-TX, COM-RX-1 and internal Noise Loader port
–30 0 Port LINE-RX
–35 0 Ports: ADD-RX-1 and ADD-RX-2
–35 5

Ports ADD/DROP-i (i=3..32)

(on DROP ports OCM is virtual)
Accuracy dB ± 0.5 ± 2 Depending on the adjacent channel relative power
Frequency range THz

191.175

191.150

 196.175 Out-of-band channel frequency 191.150 - 191.3375 THz are available only as row-data values.
Frequency accuracy (absolute) GHz ± 5
Frequency accuracy (relative) GHz +/-3
Resolution Bandwidth GHz 12.5
Frequency step GHz 3.125
Scan Time ms 250 Single port

OCM in ILA-C

The ILA-C card has a single OCM device with 4 OCM measuring points.

The measuring points in the ILA-C card are:

  • Input port of EDFA1

  • Input port of EDFA2

  • Output port of EDFA1

  • Output port of EDFA2

See ILA Functional Layout for details of the ports.

Table 2. Optical specifications for OCM in ILA-C
Parameter Unit Min. Typical Max Note
Dynamic ranges dBm/12.5GHz –30 0 LINE-RX ports
–10 10 LINE-TX ports
Accuracy dB ± 0.5 ± 2 Depending on the adjacent channel relative power
Frequency range THz 191.175 196.175
Frequency accuracy (absolute) GHz ± 5
Frequency accuracy (relative) GHz ± 3
Resolution Bandwidth GHz 12.5
Frequency step GHz 3.125
Scan Time ms 250 Single port

OCM in OLT-L

The measuring points in the OLT-L card are:

  • Input and output of preamplifier

  • ADD-i-RX ports

  • COM1-TX ports

  • Output of booster amplifier and noise loader

All OCM specs like accuracy, resolution, and more in L-band are the same as those in C band.

Table 3. Optical specifications for OCM in OLT-L
Parameter Unit Minimum Typical Maximum Note
Frequency range THz

186.05

191.125

 Out-of-band channel frequency 190.8875 - 191.125 THz are available only as row-data values.

OCM in ILA-L

The ILA-L card has a single OCM device with 4 OCM measuring points.

The measuring points in the ILA-L card are:

  • Input port of EDFA1

  • Output port of EDFA2

All OCM specs like accuracy, resolution, and more in L-band are the same as those in C band.

Table 4. Optical specifications for OCM in ILA-L
Parameter Unit Minimum Typical Maximum Note
Frequency range THz

186.05

191.125

 Out-of-band channel frequency 190.8875 - 191.125 THz are available only as row-data values.

View OCM data

You can view the raw OCM data (slice level channel power) using these commands:

RP/0/RP0/CPU0:ios#sh controllers ots 0/0/0/0 spectrum-info 
Fri Feb 4 13:12:49.841UTC​
Spectrum Slices spacing        :            3.125 GHz​
Spectrum Slices Range          :            1 - 1548​
Slice start wavelength         :            1566.82 nm​
Slice start frequency          :            191337.50 GHz​
Spectrum power information :​
Rx power :​
----------------------------------------------------------------------------------​
spectrum-slice num                        Rx-power values (dBm)​
----------------------------------------------------------------------------------​
   1 - 12               -88.8  -88.8  -88.8  -88.8      -88.8  -88.8  -88.8  -88.8      -88.8  -88.8  -88.8  -88.8​
  13 - 24               -88.8  -88.8  -88.8  -88.8      -88.8  -88.8  -88.8  -88.8      -88.8  -88.8  -88.8  -88.8​
…....​
…....​
…....​
1537 - 1548             -88.8  -88.8  -88.8  -88.8      -88.8  -88.8  -88.8  -88.8      -88.8  -88.8  -88.8  -88.8​
----------------------------------------------------------------------------------​
Tx power :​
----------------------------------------------------------------------------------​
spectrum-slice num                        Tx-power values (dBm)​
----------------------------------------------------------------------------------​
1 - 12                -9.5   -7.3   -6.0   -5.2       -4.9   -4.8   -4.6   -4.4       -4.4   -4.4   -4.4   -4.4​
13 - 24                -4.4   -4.5   -4.6   -4.8       -5.1   -5.5   -6.4   -7.7       -9.6  -12.0  -13.2  -11.4​
25 - 36                -9.2   -7.7   -6.7   -6.2       -6.0   -5.9   -5.7   -5.6       -5.6   -5.5   -5.4   -5.4​
37 - 48                -5.3   -5.3   -5.4   -5.5       -5.8   -6.1   -6.6   -7.3       -8.6  -10.4  -12.2  -11.8​
…...​
…...​
…...​
1525 - 1536              -2.4   -2.4   -2.4   -2.4       -2.4   -2.3   -2.3   -3.0       -4.2   -6.5  -10.3  -14.9​
1537 - 1548             -19.3  -22.6  -24.3  -25.3      -26.1  -26.6  -27.1  -27.6      -27.9  -28.2  -28.4  -28.6​
​

The preceding sample displays the Rx-power values (OCM3 raw data) and Tx-power values (OCM2 raw data) at the line sides. Similarly, you can view the OCM raw data for the COM side controllers OTS0/0/0/2 to 0/0/0/33.

You can also view the grid OCM data (per channel power level) for a particular channel in the ILA-C and OLT-C cards. By default, the channels are not created. Create a channel using these commands:

configure

hw-module location location terminal-ampli grid-mode mode

channel-id channel id centre-freq frequency width channel-width

commit

This is a sample to configure the channel on an OLT-C card:

RP/0/RP0/CPU0:ios#config
Fri Feb 4 13:14:49.841 UTC
RP/0/RP0/CPU0:ios(config)#
RP/0/RP0/CPU0:ios(config)#hw-module location 0/0/NXR0 terminal-ampli grid-mode flex
RP/0/RP0/CPU0:ios(config-hwmod-olt-flexi)#channel-id 1 centre-freq 196.1 width 75
RP/0/RP0/CPU0:ios(config-hwmod-olt-flexi)# commit
Fri Feb 4 13:15:12.841 UTC

RP/0/RP0/CPU0:ios(config-hwmod-olt-flexi)#end

This sample shows the OTS OCH controller channel parameters such as Total Rx power and Total Tx power.

RP/0/RP0/CPU0:ios#sh controllers ots-och 0/0/0/0/1
Fri Feb 4 13:15:59.125 UTC
Controller State: Up
Transport Admin State: In Service
LED State: Yellow
Parameter Statistics:
---------------------
Total RX Power = -10.50 dBm
Total TX Power = -10.50 dBm
Configured Parameters:
-------------
RP/0/RP0/CPU0:ios#

To view the grid OCM data for a particular channel in the ILA-C card, create a channel using these commands:

configure

hw-module location location inline-ampli grid-mode mode

channel-id channel id centre-freq frequency width channel-width

commit

This is a sample to a configure the OTS-OCH controller on an ILA-C card:

RP/0/RP0/CPU0:ios#config
Fri Feb 4 13:15:49.841 UTC
RP/0/RP0/CPU0:ios(config)#
RP/0/RP0/CPU0:ios(config)#hw-module location 0/0/NXR0 inline-ampli grid-mode flex
RP/0/RP0/CPU0:ios(config-hwmod-ila-flexi)#channel-id 1 centre-freq 196.1 width 75
RP/0/RP0/CPU0:ios(config-hwmod-ila-flexi)# commit
Fri Feb 4 13:15:12.841 UTC

RP/0/RP0/CPU0:ios(config-hwmod-olt-flexi)#end

This sample shows the OTS OCH controller channel parameters such as Total Rx power and Total Tx power.

RP/0/RP0/CPU0:ios#sh controllers ots-och 0/0/0/2/1
Fri Feb 4 13:15:59.125 UTC
Controller State: Up
Transport Admin State: In Service
Alarm Status:
-------------
Detected Alarms: None
Alarm Statistics:
-----------------
RX-LOS-P = 0
TX-POWER-FAIL-LOW = 0
Parameter Statistics:
---------------------
Total RX Power = -10.50 dBm
Total TX Power = -10.50 dBm
Configured Parameters:
-------------
RP/0/RP0/CPU0:ios#

Dynamic OCM scheduler

Table 5. Feature History

Feature name

Release information

Feature description

Dynamic OCM Scheduler

 Cisco IOS XR Release 24.4.15

Introducing the Dynamic OCM Scheduler, an enhanced OCM scheduler that is designed to optimize optical channel monitoring by replacing static scheduling with a dynamic algorithm. This accelerates the refresh rate of OCM points on the cross-connect ports, significantly boosting power monitoring and failure detection capabilities. By prioritizing cross-connected ports, the dynamic scheduler reduces polling times, effectively capturing micro flaps and alarm fluctuations.

Dynamic OCM scheduler optimizes the refresh rate of OCM points on the cross-connect ports and nonconfigured ports within OLT nodes. It refreshes the monitoring rate of the OCM points on the cross-connect ports at a higher frequency. This enhancement improves monitoring of channel power, failure detection, alarm fluctuations, and micro flaps.

How the dynamic OCM schedule works

Dynamic OCM scheduler treats cross-connect ports as medium priority and nonconfigured ports as low priority.

If you configure port 1 as a cross-connect port, the OCM scheduler treats the remaining 33 ports as low priority. In this combination, the polling time for OCM points on port 1 takes approximately one second to complete two OCM refreshments. When you increase the number of cross-connect ports, the refresh rate of the OCM points changes accordingly.