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

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

Omnidirectional topologies

Updated: September 1, 2026

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An omnidirectional topology is a network architecture that

  • enables each optical channel to be dynamically routed through any available degree of a multidegree node,

  • allows channel rerouting after fiber cuts without requiring physical fiber reconnections, and

  • supports flexible and scalable add/drop configurations for redundancy or increased capacity.

Omnidirectional topologies are often implemented in optical networks using open-line terminal (OLT) hardware and compatible passive modules. They are supported over C+L bands and can scale beyond four network degrees. Dual omnidirectional add/drop configurations provide increased reliability and add/drop bandwidth.

NCS2K-MF-4x4-COFS based colorless omnidirectional topologies

A colorless omnidirectional topology is an optical network configuration that

  • uses colorless modules to add or drop channels without wavelength constraints,

  • aggregates and routes channels from multiple degrees using compatible passive hardware assemblies, and

  • enables retuning of channel frequencies or wavelengths from connected transponders or muxponders without physical cabling changes.

Topology components

To build this topology, you need these hardware:

  • NCS 1010 OLT devices

  • NCS2K-MF-4x4-COFS modules

  • NCS2K-MF-MPO-8LC modules

  • NCS1K-BRK-8 modules

Specific cable configurations for interconnecting the modules:

  • The MF-4x4-COFS modules are interconnected using standard MPO 8 or 12 fibers (15454-MPO-MPO-x or ONS-12MPO-MPO-x )

  • The MF-4x4-COFS modules and NCS1K-BRK-8 module are interconnected using standard LC-LC fibers.

This image shows the COFS-based colorless omnidirectional topology

Figure 1. MF-4x4-COFS based colorless omnidirectional topology

Limitations

  • This configuration is supported only for C-band ROADM.

  • This configuration is scalable only up to a maximum of 4 degrees. More OSNR penalty is induced by the MF-4x4-COFS as you add more degrees.

  • One MF-4x4-COFS module can support up to only four channels. To scale up to 32 channels, you would require 8 MF-4x4-COFS modules.

  • The terminal node in this configuration can be connected only to NCS 1004 line cards, line cards with CFP2-400G-DCO as a trunk interface, and DP04QSDD pluggable.

OLT-based omnidirectional add/drop topologies

OLT-based omnidirectional add/drop topologies are optical network designs that

  • implement omnidirectional routing by interconnecting OLT devices such as OLT-C and OLT-L back-to-back,

  • enable multiple add/drop stages within a single ROADM site, improving flexibility and scalability, and

  • support integration with a variety of transponders and trunk interfaces without major restrictions.

Topology components

To build this topology, you need these hardware:

  • NCS 1010 OLT-C devices

  • NCS 1010 OLT-L devices

  • NCS1K-BRK-24 modules

  • NCS1K-BRK-8 modules

  • NCS1K-MD32-C modules

Specific configurations and applications that are required for this configuration:

  • The interconnection between the terminal OLT-C, where the traffic is terminated and the omnidirectional degree is managed as a 0dB span.

  • OSC-C and OSC-L controllers can be used with unnumbered IP on OSC interfaces of the omni span.

  • Link tuner and Gain estimator must be disabled on the Omni span.

  • APC must be enabled on Omni span.

  • ASE loading is enabled (both static and dynamic).

  • Specific configuration for optical applications such as span length and fiber type are not required.

  • To have the Preamplifier of OLT-C working in proper condition (minimum gain 12dB), the Line-Tx PSD must be set to –12.9 dBm/12.5 GHz (considering 80% CH_SD).

Figure 2. Omnidirectional configuration with OLTs
Figure 3. Dual omnidirectional configuration
Figure 4. C+L omnidirectional configuration

Limitations

  • Link tuner and gain estimator features must be disabled on Omni spans.

  • Proper functioning of terminal OLT-C preamplifiers requires precise power spectral density (PSD) settings.

  • Optical supervisory channel controllers (OSC-C and OSC-L) can be used with unnumbered IP addressing.