What is ROADM network?

Latest reply: Feb 1, 2020 07:03:04 189 7 6 1


I would like to share with you this important topic which describes ROADM network.

With ROADM technology, the OptiX OSN supports flexible optical-layer grooming in one to nine degrees. The ROADM solution realizes reconfiguration of wavelengths by blocking or cross-connecting of wavelengths. This ensures that the static distribution of the wavelength resource is flexible and dynamic. ROADM with U2000 can remotely and dynamically adjust the status of wavelength adding/dropping and passing through for a maximum of 80 wavelengths, and support 1-degree to 9-degree optical-layer grooming.

The OptiX OSN delivers flexible-grid ROADM features in addition to traditional fixed-grid ROADM features.

Basic Concepts

ROADM application scenarios include colored & directioned, colored & directionless, and colorless & directionless. For concepts about colored, colorless, directioned, and directionless, see Table 1.

Table 1 Basic Concept

The M40, D40, and M40V boards are used to add and drop wavelengths. Each add port or drop port can add or drop fixed wavelengths only.

  • Colored add/drop ports(fixed wavelength) have the advantages of lower insertion loss and lower cost. If new wavelengths need to replace the existing wavelengths, a site visit is necessary to connect the line card/OTU colored port to the matching add/drop port.

  • On an ASON network, the services can be rerouted only on the same wavelength, so the wavelengths may be blocked.


The WSM9+WSD9, WSM9+RDU9, TM20+TD20, WSMD4, WSMD9 boards are used to add and drop wavelengths. Any wavelengths can be added at a port on the board and dropped at the port.


The following figure shows a non-coherent system that uses WSM9+WSD9 boards. For the applications of a coherent system that uses TM20+TD20 boards, see 3-Degree ROADM4-Degree ROADM, and 9-Degree ROADM.

  • Colorless add/drop ports(tunable) allow remotely provisioned reconfigurability of the ROADM. However, the OTU/line boards must be installed in the subrack in order to automatically provision new services. If the OTU/line boards are not physically present in the subrack, a site visit is necessary to install the required boards for the new services.

  • On an ASON network, if a wavelength-tunable OTU or line board is used in the colorless scenario, service wavelengths can be flexibly converted during rerouting to avoid a wavelength congestion.


A local wavelength carrying services can be transmitted to a specific direction.

  • In a directioned scenario, the current path cannot be adjusted flexibly. If the current path must be adjusted, a site visit is required to adjust the fiber connections for the network.

  • A directioned scenario applies to non-ASON networks.


A local wavelength carrying services can be transmitted to any directions.

  • On a non-ASON network, the current path cannot be automatically adjusted in the directionless scenario. When services are adjusted or the protection path is used in case of a faulty working path, manually configure optical cross-connections to achieve flexible service grooming.

  • On an ASON network, the rerouting function automatically finds a path and automatically creates an optical cross-connection.

Flexible ROADM Application

The beyond 100G system supports flexible grid bandwidth grooming in addition to the 50 GHz and 100 GHz bandwidth grooming supported by traditional ROADM. Flexible grid supports flexible allocation and grooming of n x 12.5 GHz and n x 50 GHz bandwidth.

The future beyond 100G system requires more flexible spectrum allocation for high-rate optical signals and different bandwidths for signals in different modulation formats. The current ROADM technology uses the fixed grid technique, in which the bandwidth is fixed to 50 or 100 GHz. Hence, this technique cannot provide flexible bandwidth allocation.

Flexible ROADM uses the flexible grid technique to allocate different bandwidths for different signals, improving spectrum utilization and addressing the flexible signal grooming requirements of future beyond 100G systems.

Flexible ROADM is compatible with existing networks and supports fixed 50 GHz and 100 GHz bandwidth defined in ITU-T Recommendations.

Figure 1 shows the networking of an example 2-degree flexible ROADM. Flexible grid wavelengths are received, and the bandwidth of the wavelengths is not fixed to 50 or 100 GHz but can be configured. Flexible ROADM allocates different bandwidths for different signals and grooms the signals to the specified direction based on network configurations.

Figure 1 Networking of a flexible ROADM
icon-note.gif NOTE:

OTU boards that use the flexible grid technique will be provided in future versions.

1-Degree ROADM

This configuration generally applies to a terminal node. Services are not interrupted during expansion.

2-Degree ROADM

On a 2-degree ROADM network, services can be transmitted in two directions. To smoothly upgrade a network to one with over four degrees, configure RDU9+WSM9, WSD9+WSM9, WSMD2, or WSMD9.

3-Degree ROADM

On a 3-degree ROADM network, services can be transmitted in three directions. To smoothly upgrade a network to one with over four degrees, configure RDU9+WSM9, WSD9+WSM9, or WSMD9.

4-Degree ROADM

On a 4-degree ROADM network, services can be transmitted in four directions. To smoothly upgrade a network to one with over four degrees, configure RDU9+WSM9, WSD9+WSM9, or WSMD9.

9-Degree ROADM

On a 9-degree ROADM network, services can be transmitted in nine directions. Each node must use RDU9+WSM9 boards, WSD9+WSM9 boards, or WSMD9 boards

20-Degree ROADM

On a 20-degree ROADM network, services can be transmitted in twenty directions. Each node must use DWSS20+DWSS20 boards

OTN + ROADM Feature

The OTN + ROADM feature cross-connects a client service in any optical direction while ensuring high bandwidth utilization.

Figure 1 illustrates how OTN and ROADM effectively transmit client services.

  • A tributary board receives client services at any bit rate. After OTN mapping and ODUk cross-connection are complete, the client signals are flexibly cross-connected on the electrical layer and share bandwidth. A line board then outputs the signals over different wavelengths.

  • Along the optical cross-connections on the ROADM board, the signals over different wavelengths can be transmitted in any optical direction.

  • If the signals in an optical direction do not need to be locally terminated, they can be directly transmitted to another optical direction through the optical cross-connections on the ROADM board.

Figure 1 OTN + ROADM application

Reference : https://support.huawei.com/hedex/hdx.do?lib=EDOC110010073131188578&docid=EDOC1100100731&lang=en&v=01DP02&tocLib=EDOC110010073131188578&tocV=01&id=tc_wdm_ng_pln_9227&tocURL=resources%2fhelp%2fwdm%2fngwdm%2fpd%2ftc%5fwdm%5fng%5fpln%5f9227%2ehtml&p=t&fe=1&ui=3&keyword=ROADM


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Created Jan 21, 2020 06:35:08 Helpful(1) Helpful(1)

Excellent sharing, thank you
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Created Jan 21, 2020 06:38:37 Helpful(1) Helpful(1)

Clear & useful
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Created Jan 21, 2020 17:34:49 Helpful(1) Helpful(1)

Well explained, thank you
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Created Jan 24, 2020 18:02:44 Helpful(2) Helpful(2)

Great, thank you.
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Created Jan 26, 2020 23:23:28 Helpful(1) Helpful(1)

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Created Jan 27, 2020 13:04:55 Helpful(0) Helpful(0)

Can you elaborate about CDCG roadms design using above mentioned board
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Created Feb 1, 2020 07:03:04 Helpful(0) Helpful(0)

Nice share
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