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Understanding Direct Multiplexing on the TCX1000-RDM20 ROADM

 

This topic describes how you an use the universal ports on the TCX1000-RDM20 for direct multiplexing.

Direct ROADM Multiplexing With the TCX1000-RDM20

Figure 1 shows a 2-degree linear multi-span ROADM node. The top portion shows the physical interconnections needed to create the ROADM node. The bottom portion shows the logical node configuration.

Figure 1: Single Direction Add/Drop Colorless Direct Multiplexing with TCX1000-RDM20 ROADM
Single Direction Add/Drop Colorless
Direct Multiplexing with TCX1000-RDM20 ROADM

The 2-degree ROADM node in Figure 1 provides single direction add/drop colorless multiplexing and demultiplexing. A single universal port on each ROADM element is used for a pass-through connection, leaving 38 ports for direct add/drop traffic: 19 universal ports on RDM20-A and 19 universal ports on RDM20-B for directly connected, single direction add/drop traffic.

The following sections describe how multiplexing and demultiplexing works for directly connected add/drop channels and for pass-through connections in this configuration.

Multiplexing

Add/Drop Channels

The thing to keep in mind with channels that are directly connected to the TCX1000-RDM20 universal ports, is that they are always switched over the Line port of the TCX1000-RDM20 the channel is physically connected to.

Channels directly connected to the TCX1000-RDM20 are multiplexed and sent out the Line port of their respective ROADM degree:

  • Channels directly connected to ROADM degree: RDM20-A are multiplexed and sent out direction 1.

  • Channels directly connected to ROADM degree: RDM20-B are multiplexed and sent out direction 2.

Pass-Through Channels

Pass-through channels act differently than directly add/dropped channels. Channels that you configure to take a pass-through connection are multiplexed as:

  • Pass-through channels coming in from direction 1 are demultiplexed by RDM20-A and passed to the RDM20-B pass-through port. The pass-through channels are then multiplexed by RDM20-B and sent out direction 2.

  • Pass-through channels coming in from direction 2 are demultiplexed by RDM20-B and passed to the RDM20-A pass-through port. The pass-through channels are then multiplexed by RDM20-A and sent out direction 1.

In summary, pass-through channels are simply passed through the node, in one Line port and out a different Line port; they are never dropped at the node.

Demultiplexing

Add/Drop Channels

  • Channels arriving from direction 1, arrive on the line port of RDM20-A and are demultiplexed by RDM20-A and dropped to their appropriate universal ports.

  • Channels arriving from direction 2, arrive on the line port of RDM20-B and are demultiplexed by RDM20-B and dropped to their appropriate universal ports.

Pass-Through Channels

Channels that you configure to take the pass-through connection are demultiplexed as:

  • Pass-through channels from direction 1 arrive on the line port of RDM20-A. The channels are demultiplexed and sent to the RDM20-A pass-through port and passed to the RDM20-B pass-through port. The pass-through channel is then multiplexed by RDM20-B and sent out direction 2.

  • Pass-through channels from direction 2 arrive on the line port of RDM20-B. The channels are demultiplexed and sent to the RDM20-B pass-through port and passed to the RDM20-A pass-through port. The pass-through channel is then multiplexed by RDM20-A and sent out direction 1.

Summary of Direct ROADM Multiplexing

Figure 2: Summary of Direct ROADM Multiplexing
Summary of Direct ROADM
Multiplexing

Referring to Figure 2, coherent transceiver interfaces connect directly to the universal (Ux) ports on the TCX1000-RDM20. This provides channel ports which are:

  • Colorless

  • Single direction (defined by TCX1000-RDM20 direction)

  • Supports non-coherent channels

The number of Ux ports available at a node depends on what is used for other connections. For example are pass-through connections configured on the universal ports. To calculate the available universal ports on each ROADM degree, use the following:

There are 20-(N-1) universal ports available on the ROADM degree, where N is the number of directions at a ROADM node.

For example:

  • In a 1-degree site (terminal) there are 20 available universal ports on the ROADM

  • In 2-degree site (terminal) there are 19 available universal ports on each ROADM degree for a total of 2x19=38 universal ports for the ROADM node

  • In 3-degree site (terminal) there are 18 available universal ports on each ROADM degree for a total of 3x18=54 universal ports for the ROADM node