Raman Tuning Algorithm calculates and sets the different pump power values across five Raman pumps to obtain the target Raman Gain on a span. Raman tuning runs in both directions of the span independently at the node level. Raman tuning requires communication between peer nodes. Hence, OSC communication between the two nodes is a prerequisite for Raman Tuning.

Raman tuning algorithm uses the following parameters to calculate the pump powers necessary to achieve the target Raman gain.

• Fiber type

• Fiber length

• Loss on the fiber at each pump wavelength

• Loss on the fiber at the signal wavelength

If you configure a span length value, Raman tuning uses this value.

Raman tuning is disabled by default. Raman tuning is enabled if automatic link bring up is enabled. You can manually trigger Raman tuning if necessary. The NCS 1010 initiates the tuning process under the following circumstances:

• During the initial link bring up

• After a fiber cut

• After a power cycle event

• After a line card cold reload event

• After a DFB shut or unshut event

• After an OTS controller shut or unshut event on near end or far end node

• After modification of span length configuration

Raman tuning is traffic impacting. When Raman tuning is in progress, the amplifier on the far end of the span is turned off to block traffic. The Optical Safety Remote Interlock (OSRI) feature allows turning off the amplifier on the peer node for Raman tuning. Only the OSC is active on the link while Raman tuning is in progress.

At the LINE-TX port on the far end of the span, the dedicated Raman probe (DFB) is combined with the transmitted optical channels. The DFB laser at 191.1 THz is used to perform a link continuity check on the Raman span for optical safety. The DFB laser is used during Raman tuning.

At the LINE-RX port, five wavelengths between 1424 nm and 1495 nm are inserted in the counter propagating direction of the signal to provide amplification using the Raman effect for both C and L band optical channels.

The system triggers Raman tuning when a link goes down and comes back up. After completing Raman tuning successfully, soft reloads, RP reloads, Raman OSRI change, and Raman Force APR change do not retrigger Raman tuning.

The following table lists and describes the different Raman Tuning Status.

Raman tuning works in the following three modes:

• Auto mode: Raman tuning defines the target gain and sets the pump powers and DFB VOA attenuation to achieve the target gain overwriting user configuration.

• Gain mode: User defines the gain target and Raman tuning sets the pump powers and DFB VOA attenuation to achieve the target gain.

• Manual mode: User disables Raman tuning and manually configures the Raman pumps and DFB VOA attenuation.

When Raman tuning is in progress, the node performing Raman tuning triggers the RAMAN-TUNE-IN-PROGRESS alarm. From Cisco IOS XR Release 7.9.1, NCS 1010 supports C+L band networks. In a C+L band configuration, the RAMAN-TUNE-IN-PROGRESS alarm is raised at the C-band OLT or ILA node performing Raman tuning as well as the far end L-band node. OSRI disables the EDFA amplifiers on both the C and L band devices in the peer node during Raman Tuning.

Note

If Raman back reflection (BR) is high, Raman tuning turns the Raman pumps off and goes into blocked state. High BR can damage the optics. When you clear the high BR and BR is at acceptable levels, the system triggers Raman tuning and turns the Raman pumps on. If a Raman span has a span loss value less than 14 dB, Raman tuning goes into the BLOCKED state. The NCS 1010 performs a span loss check at system startup to verify if you can use Raman amplification effectively on the span.

View Raman Tuning Status

You can view the Raman tuning status using show olc raman-tuning command. The following sample is an output of the show olc raman-tuning command.

RP/0/RP0/CPU0:ios#sh olc raman-tuning 
Tue Mar 21 06:11:36.944 UTC

Controller : Ots0/0/0/0
Raman-Tuning Status : TUNED
Tuning Complete Timestamp : 2023-03-20 07:54:00
Estimated Max Possible Gain : 19.8 dB
Raman Gain Target : 16.0 dB
Gain Achieved on Tuning Complete : 15.7 dB

You can view the Raman tuning status for individual controllers using show olc raman-tuning controller ots r/s/i/p command. The following sample is an output of the show olc raman-tuning controller ots r/s/i/p command.

RP/0/RP0/CPU0:ios#sh olc raman-tuning controller ots 0/0/0/0
Tue Mar 21 06:13:26.535 UTC

Controller : Ots0/0/0/0
Raman-Tuning Status : TUNED
Tuning Complete Timestamp : 2023-03-20 07:54:00
Estimated Max Possible Gain : 19.8 dB
Raman Gain Target : 16.0 dB
Gain Achieved on Tuning Complete : 15.7 dB

You can view detailed Raman tuning status using show olc raman-tuning details command. The following sample is an output of the show olc raman-tuning details command.

RP/0/RP0/CPU0:ios#show olc raman-tuning details
Tue Mar 21 06:27:13.302 UTC

Controller : Ots0/0/0/0
Raman-Tuning Status : TUNED
Tuning Complete Timestamp : 2023-03-20 07:54:00
Estimated Max Possible Gain : 19.8 dB
Raman Gain Target : 16.0 dB
Gain Achieved on Tuning Complete : 15.7 dB
Last Run Fail Reason : [ Peer node is unreachable ]
Last Run Fail Timestamp : 2023-03-19 12:20:37
Last Successful Tuning Gain : 15.7 dB
Last Successful Tuning Timestamp : 2023-03-20 07:54:00

You can view detailed Raman tuning status for individual controllers using show olc raman-tuning details controller ots r/s/i/p command. The following sample is an output of the show olc raman-tuning details controller ots r/s/i/p command.

RP/0/RP0/CPU0:ios#show olc raman-tuning details controller Ots 0/0/0/0
Tue Mar 21 06:27:58.213 UTC

Controller : Ots0/0/0/0
Raman-Tuning Status : TUNED
Tuning Complete Timestamp : 2023-03-20 07:54:00
Estimated Max Possible Gain : 19.8 dB
Raman Gain Target : 16.0 dB
Gain Achieved on Tuning Complete : 15.7 dB
Last Run Fail Reason : [ Peer node is unreachable ]
Last Run Fail Timestamp : 2023-03-19 12:20:37
Last Successful Tuning Gain : 15.7 dB
Last Successful Tuning Timestamp : 2023-03-20 07:54:00

To view the individual Raman pump information and other parameters, use the show controllers ots r/s/i/p raman-info command.

RP/0/RP0/CPU0:ios#show controllers ots 0/0/0/0 raman-info 
Fri Apr  1 06:40:33.849 UTC

         Alarm Status:
         -------------
         Detected Alarms: None


         Alarm Statistics:
         -----------------
         RAMAN-AUTO-POW-RED = 0          
         RAMAN-1-LOW-POW = 0          
         RAMAN-2-LOW-POW = 0          
         RAMAN-3-LOW-POW = 0          
         RAMAN-4-LOW-POW = 0          
         RAMAN-5-LOW-POW = 0          
         RAMAN-1-HIGH-POW = 1          
         RAMAN-2-HIGH-POW = 0          
         RAMAN-3-HIGH-POW = 0          
         RAMAN-4-HIGH-POW = 0          
         RAMAN-5-HIGH-POW = 0          

         Parameter Statistics:
         ---------------------
         Raman Safety Control mode = auto 
         Raman Osri = OFF 
         Raman Force Apr = OFF 
         Composite Raman Power = 886.60 mW

         RAMAN Pump Info:
         ---------------------
         Instance        Wavelength(nm)  Power(mW)
          1               1424.00                 257.60
          2               1438.00                 255.10
          3               1457.00                 71.60
          4               1470.00                 127.50
          5               1495.00                 170.10



         Configured Parameters:
         -------------
         Raman Safety Control mode = auto 
         Raman Osri = OFF 
         Raman Force Apr = OFF 

         RAMAN Pump Info:
         ---------------------
         Instance        Power(mW)
          1               45.00
          2               40.00
          3               40.00
          4               40.00
          5               35.00

The following sample output

Note

In the previous output, there are two sections for Raman Pump Info that show different values. The first Raman Pump Info section displays operational data (current pumps power values). The second Raman Pump Info section displays Raman Pump Power configuration. In this case, the default pump powers are displayed. Use the raman-tx-power pumpvaluevalue command to configure individual Raman pump powers.

The Raman tuning application locks the OTDR scan at both fiber ends before the tuning starts, and releases the lock after the tuning completes. Therefore, when you try to start the OTDR scan when Raman tuning is running, your request gets rejected. The following example explains the OTDR start request rejection. The OTDR scan request that has been rejected already does not run automatically after the lock is released, so you have to create a new request to start the OTDR again.

The OTDR scan and Raman tuning cannot be simultaneously executed on the same fiber. To resolve this issue, Raman tuning application locks the OTDR at both ends of the fiber before the tuning process starts and releases the lock after the tuning completes.

If the OTDR scan is in progress, the lock request is rejected and the Raman tuning application retries every minute to acquire the OTDR lock. The Raman tuning starts only when OTDR scan lock is acquired at both ends of the fiber. If the Raman tuning application is running, user request to start OTDR scan is rejected. See Start OTDR.

The following sample shows the blocked status of the Raman Tuning due to OTDR running in remote node.

RP/0/RP0/CPU0:ios#show olc raman-tuning 
Tue Feb 28 10:32:12.648 UTC

Controller                       : Ots0/0/0/0
Raman-Tuning Status              : BLOCKED
Blocked Reason Details           : [ Raman peer response OSRI ON/OTDR LOCK ON failure ]
Tuning Complete Timestamp        : N/A
Estimated Max Possible Gain      : N/A dB
Raman Gain Target                : N/A dB
Gain Achieved on Tuning Complete : N/A dB

The following sample shows the blocked status of the Raman Tuning due to OTDR running in local node.

P/0/RP0/CPU0:ios#sh olc raman-tuning 
Tue Feb 28 10:39:18.055 UTC
Controller                       : Ots0/0/0/0
Raman-Tuning Status              : BLOCKED
Blocked Reason Details           : [ Raman local OTDR LOCK ON failure ]
Tuning Complete Timestamp        : N/A
Estimated Max Possible Gain      : N/A dB
Raman Gain Target                : N/A dB
Gain Achieved on Tuning Complete : N/A dB