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Creating Multi-Degree ROADM Nodes

 

This topic describes how you can interconnect the TCX1000-RDM20 to deploy multi-degree ROADM nodes by using pass-through fiber connections on the universal ports of the TCX1000-RDM20 to interconnect ROADM degrees in multi-degree nodes. It includes the following subjects:

Refresher: Pass-Through Versus Directly Add/Drop Channels

Before we discuss how you create multi-degree ROADM nodes using pass-through, recall how pass-through and add/drop connections work:

  • Pass-Through Connections — Enables you to pass through channels from one ROADM degree to another within a multi-degree node. Pass-through is therefore multi-directional. Pass-through is possible between any ROADM degrees that have universal port to universal port connectivity (which may not be every degree in every multi-degree ROADM node).

  • Add/Drop Connections — Directly connected channels are always routed out the same ROADM element that they are physically connected to and are therefore, single direction.

    Best Practice

    TCX1000-RDM20 ROADM nodes are capable of switching any directly connected channels to any degree the node serves as long as you connect your transceiver to the correct ROADM element within the node.

    In addition, it is important to take note of which ROADM degree you attach your transceivers to in multi-degree nodes (sites), to ensure the channel traverses the shortest path between source and destination.

In the following sections, we look at multi-degree ROADM node configurations and what their pass-through and add/drop capabilities are.

Creating 2-Degree ROADM Node Configurations

Using TCX1000-RDM20 pass-through, you can create 2-degree ROADM node configurations by interconnecting two ROADM degrees in a single node.

Figure 1: 2-Degree ROADM Node
2-Degree ROADM Node

Figure 1 shows a two-degree ROADM node. The top portion shows the physical interconnections needed to create the ROADM node. The bottom portion shows the logical node configuration.

To create this ROADM node configuration, you can use two TCX1000-RDM20 ROADM elements. In this example: RDM20-A and RDM20-B are interconnected with a fiber cable between a single universal port on each ROADM degree, allowing you to pass-through channels between direction 1 and 2. This creates a single ROADM node with two line directions (ROADM degree 1 and 2) and leaves 19 universal ports on RDM20-A and 19 universal ports on RDM20-B that you can use to directly add/drop traffic: 19 channels to/from degree 1 and 19 channels to/from degree 2.

Understanding the Pass-Through Capabilities in This Configuration

In Figure 1, a single pass-through fiber connection exists between ROADM degrees: RDM20-A and RDM20-B. The proNX Optical Director automatically selects the pass-through path for services running between direction 1 and 2.

Understanding the Add/Drop Capabilities in This Configuration

The ROADM node configuration in Figure 1 enables single direction colorless multiplexing:

  • Channels connected to RDM20-A are always routed out degree 1.

  • Channels connected to RDM20-B are always routed out degree 2.

You can add/drop channels in either direction 1 or 2. However, you must physically connect the channel to the appropriate ROADM degree. Make sure to connect the channel to a universal port on the ROADM degree that is responsible for the direction in which you want the channel to be switched.

For example, to add/drop a channel to/from direction 1, you must connect the transceiver to a universal port on RDM20-A. Conversely, to add/drop a channel to/from direction 2, you must connect the transceiver to a universal port on RDM20-B.

Creating 3-Degree ROADM Node Configurations Using Pass-Through

Using the TCX1000-RDM20, you can create 3-degree nodes like the one shown in Figure 2.

Figure 2: 3-Degree ROADM Node Using Pass-Through
3-Degree ROADM Node Using Pass-Through

In Figure 2, shows a 3-degree ROADM node configuration. The top portion of this figure shows the physical interconnections needed to create the ROADM node and the bottom portion shows the logical node configuration.

To create this 3-degree ROADM node, you can use three TCX1000-RDM20s that are each interconnected with fiber cables between two universal ports on each ROADM degree, allowing you to pass-through channels between all three directions in the node. This leaves 18 universal ports on each ROADM element that you can use for add/drop traffic.

Understanding the Pass-Through Capabilities in This Configuration

Figure 2 has three pass-through paths:

  • Path between RDM20-A and RDM20-B

  • Path between RDM20-A and RDM20-C

  • Path between RDM20-B and RDM20-C

These pass-through paths enable any-to-any directional switching:

  • Channels to/from direction 1 can be switched to/from direction 2

  • Channels to/from direction 1 can be switched to/from direction 3

  • Channels to/from direction 2 can be switched to/from direction 3

Understanding the Add/Drop Capabilities in This Configuration

In Figure 2 you can add/drop channels in three possible directions: 1, 2, and 3. However, in order to do so, you must connect the channel transceiver to the appropriate ROADM degree within the node. Make sure to connect the channel transceiver to a universal port on the ROADM degree that is responsible for the direction in which you want the channel to be switched.

  • To add/drop a channel to/from direction 1, connect the channel transceiver to a universal port on RDM20-A.

  • To add/drop a channel to/from direction 2, connect the channel transceiver to a universal port on RDM20-B.

  • To add/drop a channel to/from direction 3, connect the channel transceiver to a universal port on RDM20-C.

Creating 4-Degree ROADM Nodes Using Pass-Through

Using the TCX1000-RDM20, you can create 4-degree ROADM node configurations like the one in Figure 3. The top portion of the figure shows the physical interconnections needed to create the ROADM node. The bottom portion shows the logical node configuration.

To create this node, you can use four TCX1000-RDM20s that are each interconnected with fiber cables between three universal ports on each ROADM degree, allowing you to pass-through channels between all four directions in the node. This leaves 17 universal ports on each ROADM degree that you can use to add/drop traffic.

Figure 3: 4-Degree ROADM Node Using Pass-Through
4-Degree ROADM Node Using Pass-Through

Understanding the Pass-Through Capabilities in This Configuration

The ROADM node in Figure 3 has the following pass-through paths:

  • Path between RDM20-A and RDM20-B

  • Path between RDM20-A and RDM20-C

  • Path between RDM20-A and RDM20-D

  • Path between RDM20-B and RDM20-D

  • Path between RDM20-B and RDM20-C

  • Path between RDM20-C and RDM20-D

The ROADM node in Figure 3 enables any-to-any directional switching including:

  • Channels to/from direction 1 can connect to/from direction 2

  • Channels to/from direction 1 can connect to/from direction 3

  • Channels to/from direction 1 can connect to/from direction 4

  • Channels to/from direction 2 can connect to/from direction 3

  • Channels to/from direction 2 can connect to/from direction 4

  • Channels to/from direction 3 can connect to/from direction 4

Understanding the Add/Drop Capabilities in This Configuration

In Figure 3, you can add/drop channels in all four directions: 1, 2, 3 and 4. However, in order to do so, you must connect the channel transceiver to the appropriate ROADM degree within the node. Make sure to connect the channel transceiver to a universal port on the ROADM degree that is responsible for the direction you want the channel switched.

  • To add/drop a channel to/from direction 1, connect the channel transceiver to a universal port on RDM20-A.

  • To add/drop a channel to/from direction 2, connect the channel transceiver to a universal port on RDM20-B.

  • To add/drop a channel to/from direction 3, connect the channel transceiver to a universal port on RDM20-C.

  • To add/drop a channel to/from direction 4, connect the channel transceiver to a universal port on RDM20-D.