Difference between WDM vs OTN

Difference between WDM vs OTN

The constant demand for Internet-based services makes operator networks an even more important social infrastructure. Operators need to deliver higher speed, higher capacity and higher reliability networks.
Therefore, two technology come into our sight: DWDM vs. OTN, the technologies that can expand existing bandwidth. To learn more about them and the difference between OTN and DWDM, this article may be of some help.

What Is WDM?

Wavelength division multiplexing (WDM): The WDM technology multiplexes optical signals of different wavelengths into one fiber for transmission (each wavelength carries one service signal). The WDM technology is mainly used for transmission and multiplexing.
Before the WDM technology, all transmission technologies allow one fiber to transmit only one wavelength, whereas WDM technologies allow one fiber to transmit multiple wavelengths. Currently, a common WDM system includes 8 (coarse wavelength division multiplexing, CWDM), 40, 80, 96, or 120 wavelengths. Carrying more wavelengths is one of the future evolution trends of WDM.

Features of traditional WDM:

  • Significance of traditional WDM: (solving the problems of capacity and distance)
  • Solve the problem of insufficient SDH network capacity. The maximum bandwidth of metro WDM can support 80 × 10G, while the maximum bandwidth of the SDH network is 10G.
  • Limitations of traditional WDM: (inadequate scheduling, protection, and management functions)
  • Similar to the PDH system, the WDM system can only form point-to-point chains. The wavelength cannot be flexibly scheduled, and complex networks cannot be formed. Therefore, it is not suitable for the development of IP networks.
  • It does not support ASON intelligent features and cannot evolve to an intelligent optical network, which is not the development direction of the next-generation transport network.

What Is OTN?

The WDM technology solves the problem of insufficient fiber resources. However, it lacks OAM, flexible grooming, and incomplete protection. Therefore, the optical transport network (OTN) is developed.
OTN: It is a network that uses optical fibers as transmission media to transmit information, in compliance with ITU-T G.709, G.872, and G.798.
An OTN performs the following functions for client signals based on optical channels: transmission, multiplexing, routing, management, monitoring, and protection.
Based on the traditional WDM, the OTN integrates some advantages of the SDH and supports flexible optical-layer grooming and electrical-layer grooming, intensive OAM overheads, and comprehensive protection schemes.

Features of the OTN :

  • The large bandwidth transmission capability of WDM
  • The flexible networking capability of SDH
  • ASON intelligent features can be loaded and upgraded to intelligent optical network

WDM vs. OTN–What are the Differences?

  1. In WDM, traditional transport functions such as switching, grooming, configuration, and restoration are eliminated from the SONET/SDH layer and moved to the IP layer which is supposed to be enhanced by MPLS. Alternatively, the optical layer is the one that deals with the aforementioned, exploiting the intelligence of OXCs.
  2. OTN solution is more scalable than IP/WDM since the core of the network is based on the more scalable OXCs rather than IP routers.
  3. OTN is more flexible to traffic changes than WDM.
  4. OTN, the optical transport layer provides the restoration services in a fast and scalable way (optical shared mesh restoration), whereas in WDM restoration is achieved by IP rerouting which is a slow process and may lead to instability in the network.
  5. When comparing the cost, WDM appears to be a more cost-prohibitive solution than the OTN architecture. Furthermore, as years go by and total traffic increases, the cost difference between both architectures is more severe.

Development of Optical Network Technology:

PDH and SDH are both TDM technologies, and proper overhead processing makes the point-to-point chain into an end-to-end network;
The current WDM is still a point-to-point chain. To adapt to the IP-based network in the future, it must develop into an end-to-end network, and add appropriate overhead processing, which illustrates the development of OTN;
ASON (GMPLS) is the control layer. It cooperates with the channel-layer SDH, OTN, and AON successively during its development to control the cross-scheduling of VC4, ODUk, and wavelength in a unified way.
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