Overview

This topic describes the basic concepts of the WDM service configuration.

Overview of Cross-Connections

The grooming function of electrical cross-connections of WDM equipment helps WDM networks to change from static networks to dynamic networks. Operations, such as pass-through, adding, dropping, loopback, can be performed on each sub-service on any station independently, without affecting the services in other channels. The electrical cross-connection realizes automatic configuration through remote management. No fiber jumper needs to be performed manually. In this manner, the operation cost and the possibility of misoperation are reduced.

Unlike the point-to-point multiplexing channel scheme of traditional WDM MUX/DMUX, the electrical cross-connections are added with, for example, GE and ODUk cross-connections and end-to-end management capability on the basis of the MUX/DMUX. In addition, the electrical cross-connection scheme is different from the ADM scheme that is based on wavelengths. It allows the cross-connection of services between wavelengths, providing service convergence and grooming of different wavelengths.

Electrical cross-connections are classified as follows:

According to the cross-connection level and granularity, electrical cross-connections are classified into, for example, GE, Any, and ODUk cross-connections.
According to the grooming mode, electrical cross-connections are classified into centralized cross-connections and distributed cross-connections.
Compared with the synchronous mode, the asynchronous mode does not support the ODU0 grooming and the internal logic port ODU0LP.
- The synchronous mode supports the XCH, XCT and SXM board.
According to the cross-connection mode, electrical cross-connections are classified into the synchronous mode and asynchronous mode.
According to the location of cross-connection, electrical cross-connections can be in straight-through mode or cross-connect mode.
- Straight-through mode:
  - Optical signals received at the RXn port on the client side pass through the cross-connect unit and directly travel to the corresponding channels on the WDM side. After multiplexing, signal processing and optical wavelength conversion, these signals are output from the OUT port. After wavelength conversion and signal processing, signals input from the IN port on the WDM side are demultiplexed into one or more channels of electrical signals that pass through the cross-connect unit and directly travel to the corresponding TXn on the client side.
- Cross-connect mode:
  Cross-connections in cross-connect mode are classified into intra-board cross-connections and inter-board cross-connections.
  - Intra-board cross-connection:
    Optical signals received at the RXn port on the client side are cross-connected by the cross-connect unit to the channels that correspond to other optical interfaces of the same board on the WDM side. After multiplexing, signal processing and optical wavelength conversion, these signals are output from the OUT port. After wavelength conversion and signal processing, signals input from the IN port on the WDM side are demultiplexed into multiple channels of electrical signals, one channel of which is cross-connected by the cross-connect unit to the client-side TXn port that corresponds to other channels of the same board.
  - Inter-board cross-connection:
    Optical signals received at the RXn port on the client side are cross-connected by the cross-connect unit to the channels that correspond to optical interfaces of another board on the WDM side. After multiplexing, signal processing and optical wavelength conversion, these signals are output from the OUT port. After wavelength conversion and signal processing, signals input from the IN port on the WDM side are demultiplexed into multiple channels of electrical signals, one channel of which is cross-connected by the cross-connect unit to the client-side TXn port that corresponds to other channels of another board.

The straight-through and cross-connect services should be configured on the U2000 Web LCT. That is, create cross-connect services.
Straight-through services are as shown in the following figure: 3 (RX1/TX1) (client-side optical interfaces) <-> 3 (channel number), 4 (RX2/TX2) <-> 4, 5 (RX3/TX3) <-> 5, 6 (RX4/TX4) <-> 6.
The cross-connect service is shown in the following figure: 5 (RX1/TX1) (client-side optical interfaces) <->3 (channel number), 3 (RX1/TX1) (client-side optical interfaces) <->6 (channel number).

Restrictions on Cross-Connection Configuration

Earlier version NE software does not support cross-connection creation between boards of different types.
As the NE software imposes restrictions on backplane cross-connections, the boards between which you want to create cross-connections must be in cross-connect slots. In the case of different types of equipment, boards, and the corresponding NE software versions, their cross-connect slots and cross-connect groups are different.
If you configure a cross-connection between the two optical ports on the OTU board, the source of a non-protection cross-connection can also serve as the source of other non-protection cross-connections, but its sink cannot be the sink of other cross-connections. The two sources of a singleSNCP cross-connection cannot be the sources of other cross-connections, and its sinks cannot be the sink of other cross-connections.

When configuring the electrical cross-connection for a service on the OptiX OSN 3800A, OptiX OSN 6800A, OptiX OSN 8800 T16(NA), OptiX OSN 8800 T32(NA) and OptiX OSN 8800 T64(NA), you must make sure that the WDM-side optical channel numbers at the transmit and receive ends of the service in a direction must be the same. Otherwise, the service fails.

The OptiX OSN 3800A provides mesh cross-connections in the four-slot group based on the GE service, ODU1 signal, and Any service.

Normal cross-connections on the OptiX OSN 6800A are classified into centralized cross-connections and distributed cross-connections.

Centralized cross-connection: If the XCS board is configured during the cross-connection creation, the cross-connection can be realized through the XCS. The boards where you want to create cross-connections can be placed in any slots that support the boards. If you want to delete the XCS board on the U2000 Web LCT, first delete the cross-connections that are related to the XCS board.
Distributed cross-connection: If no XCS board is configured during the cross-connection creation, the boards where you want to create cross-connections can be placed in paired slots.

On the OptiX OSN 8800 T16(NA), OptiX OSN 8800 T32(NA) and OptiX OSN 8800 T64(NA), non-protection cross-connections support centralized cross-connections based on the ODU0, ODU1 ODU2, and ODU3 signal only.

The OptiX OSN 1800(NA) adopts mesh cross-connections and paired-slot 8 x GE cross-connections.

OptiX OSN 1800(NA) I chassis IU1 and IU3, IU1 and IU4 form the mesh cross-connection. IU3 and IU4 form a group of paired slots.
OptiX OSN 1800(NA) II chassis IU3 and IU4, IU3 and IU6, IU5 and IU6, IU5 and IU4 form the mesh cross-connection. There are three groups of paired slots: IU1 and IU2, IU3 and IU5, and IU4 and IU6.

Signal Flow of Electrical Cross-Connections

In the case of the WDM equipment, the OTU board, tributary board, and line boardthe OTU board work together to complete the cross-connect grooming of services. The client services are transmitted from the client side of the WDM equipment, and then modulated to the WDM system for transmission after service grooming and convergence. Figure 1 taking the OTU board that supports GE, Any, and ODUk cross-connections as a model, the following describes the signal flow of electrical cross-connections.Figure 2 taking the OTU board that supports GE cross-connections as a model, the following describes the signal flow of electrical cross-connections.

Figure 1 Signal flow of electrical cross-connections

The signals are cross-connected in the following process:

The optical signals are transmitted to the OTU board through the TX/RX interface and become electrical signals. After the possible Layer 2 processing, the electrical signals are transmitted to the GE/Any cross-connect module through the AP interface and work with the possible cross-connect signals from the backplane, to realize the GE/Any cross-connections.
The electrical signals are transmitted to the ODUk cross-connect module through the LP interface and work with the possible ODUk signals from the backplane, to realize the ODUk cross-connections. Then, the signals are transmitted to the optical module through an OP interface and then added to the WDM line for transmission.

NOTE:

The boards that support the grooming of electrical cross-connections have both the external interfaces and internal interfaces. These interfaces are classified into the following types:

TX/RX interface: client-side optical interface of the board that receives and transmits signals.
IP interface: internal interface that corresponds to the TX/RX interface. It can be regarded as a TX/RX interface.
AP interface: convergence interface that represents the internal interface of the Layer 2 module. In this case, the corresponding IP interface is an external interface.
LP: logical interface that functions as the connection point of cross-connections.
OP interface: internal interface that corresponds to the IN/OUT interface. It can be regarded as an IN/OUT interface.
IN/OUT interface: line-side optical interface of the board that receives and transmits signals.

Figure 2 Signal flow of electrical cross-connections

The signals are cross-connected in the following process:

The optical signals are transmitted to the OTU board through the TX/RX interface and become electrical signals. The electrical signals are transmitted to the GE cross-connect module work with the possible cross-connect signals from the backplane, to realize the GE cross-connections. Then, the signals are transmitted to the optical module through an OP interface and then added to the WDM line for transmission.

NOTE:

The boards that support the grooming of electrical cross-connections have both the external interfaces and internal interfaces. These interfaces are classified into the following types:

TX/RX interface: client-side optical interface of the board that receives and transmits signals.
LP: logical interface that functions as the connection point of cross-connections.
OP interface: internal interface that corresponds to the IN/OUT interface. It can be regarded as an IN/OUT interface.
IN/OUT interface: line-side optical interface of the board that receives and transmits signals.