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

Raman tuning

Updated: February 5, 2026

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Overview

Purpose of Raman tuning
Conditions that trigger automatic Raman tuning
Raman tuning parameters
Raman tuning modes
Raman tuning initiation conditions
Raman tuning status

Overview

This topic explains the concept of Raman tuning, its purpose, and operational behavior, and the conditions under which automatic tuning is initiated.

Raman tuning is a process that adjusts the power and wavelength of Raman pump lasers to optimize optical signal amplification over a fiber span.

Controls Raman pump power and wavelength.
Targets a specific fiber span to achieve the required Raman gain.
Optimizes end-to-end signal performance.

Purpose of Raman tuning

The primary purpose of Raman tuning is to achieve the desired Raman gain across a fiber span while maintaining optimal signal quality.

Raman tuning follows these operational principles:

Raman tuning is performed independently in both directions of a fiber span.
Peer nodes communicate to coordinate tuning and achieve the target gain across the span.

When Raman tuning is configured in automatic mode, the NCS 1010 system initiates the tuning process without manual intervention to maintain optimal signal amplification.

Conditions that trigger automatic Raman tuning

The NCS 1010 automatically initiates Raman tuning under these conditions:

After the initial link bring-up.
After a fiber cut is detected and cleared.
After a device power cycle.
After a line card cold reload.
During a Distributed Feedback (DFB) shut or unshut event.
After an OTS controller is shut or unshut on the near-end or far-end node.
After a span length configuration change.
After high back reflection conditions return to acceptable levels.
During a span loss check at system startup.

Raman tuning parameters

This section describes the parameters used by the Raman tuning algorithm to optimize Raman amplifier performance.

The Raman tuning algorithm uses the following parameters to achieve the target signal amplification across an optical fiber span.

Target Raman gain defines the required level of signal amplification.
Raman pump power controls the strength of the Raman amplification.
DFB VOA attenuation fine-tunes the amplified signal to meet gain requirements.

Table 1. Raman tuning parameters
Parameter	Description	Usage
Target Raman Gain (dB)	It is the desired level of amplification the Raman amplifier aims to achieve. This gain is the increase in optical signal power resulting from Raman scattering when the signal passes through the medium with co-propagating or counter-propagating pump lasers.	The desired Raman gain is typically used for compensating for signal losses in the optical fiber, ensuring signal integrity and strength over long distances.
Raman Pump Powers (mW)	It is the power levels of the Raman pump lasers used in the Raman amplification process. Higher pump power results in a higher gain but also increases the risk of fiber damage.	The power from Raman pumps is used to inject laser at specific wavelengths into the fiber, which then interacts with the signal through the Raman scattering effect to amplify it.
DFB VOA Attenuation (dB)	It is the attenuation settings of the Variable Optical Attenuator (VOA) used with Distributed Feedback (DFB) lasers. DFB lasers provide high-precision, stable-wavelength light emission, commonly used in telecommunications.	DFB VOA attenuation is used to fine-tune the signal power levels to ensure the amplified signal meets the target gain requirements. Adjusting the attenuation helps balance the pump power and signal power.

Raman tuning modes

This section describes the Raman tuning modes available on the NCS 1010 and how each mode affects tuning behavior.

Use Raman tuning modes to control when Raman tuning runs and which parameters are set automatically.

Automatic mode starts Raman tuning based on system events and sets key parameters automatically.
Manual and disable modes provide more operator control over when tuning starts and how parameters are set.

Table 1. Raman tuning modes
Raman tuning modes	Description
Enable (Automatic mode)	In this mode, the system automatically initiates Raman tuning when a link goes down and comes back up. Raman tuning calculates and sets the values of the following parameters automatically: Raman target gain Raman power DFB VOA attenuation However, this mode also allows you to manually set the target gain, which triggers Raman tuning to adjust pump powers and DFB VOA attenuation values to achieve the target gain. For more details about the conditions that trigger Raman tuning automatically, see Raman tuning initiation conditions.
Disable	In this mode, you must manually set the values Raman tuning parameters. After configuring these values, you must manually initiate Raman tuning. It may be necessary to manually configure these parameters to troubleshoot network issues or fine-tune the system for improved performance.
Manual	In this mode, Raman tuning must be manually initiated when a link goes down and comes back up. Once initiated, the system automatically calculates the desired gain and adjusts both pump powers and DFB VOA attenuation to achieve the specified target gain.

Raman tuning initiation conditions

This section describes the conditions under which the NCS 1010 automatically initiates Raman tuning.

When Raman tuning is configured in automatic mode, the system initiates tuning after the following events:

An initial link bring-up.
A fiber cut and subsequent recovery.
A device power cycle.
A line card cold reload.
A Distributed Feedback (DFB) shut or unshut event.
An OTS controller shut or unshut event on either the near-end or far-end node.
A change in the span length configuration.
Clearance of high back reflection conditions.
A span loss check during system startup.

Raman tuning status

This section describes the possible Raman tuning status values and what each status indicates during the tuning process.

The Raman tuning status reflects whether the system is actively tuning, has completed tuning, or cannot perform tuning.

Working states indicate active measurement, calculation, or optimization.
Non-working states indicate completion, blockage, or disabled tuning.

Table 1. Raman tuning status
Raman tuning status	Description
WORKING—MEASUREMENT	Raman tuning is measuring the span loss on the link.
WORKING—CALCULATION	Raman tuning is calculating the gain target and required pump powers.
WORKING—OPTIMIZATION	Raman tuning is optimizing the pump powers.
TUNED	Raman tuning is complete.
BLOCKED	The system cannot perform Raman tuning because the link is down or there is a high Raman back reflection.
DISABLED	Raman tuning is disabled.

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