The business case for embedded DWDM over ELWL
Several methods are available for connecting data center infrastructure at different sites in an enterprise network. Companies can run the network by themselves in a private network or have an operator run it for them through a managed service. Building a private network requires access to fiber, either owned or leased, between the sites. Various technology choices are possible depending on the total amount of traffic required throughout the lifetime of the network and the distance between sites. This article focuses on comparing two of them: an eight-channel 16G FC embedded DWDM and an eight single-channel extended long wavelength (ELWL) solution.
Single-channel connectivity, ELWL, means that a single channel of traffic is run over a single dark fiber connection. Here, the ELWL optical transceiver is connected in to the host switch (Ethernet or Fibre Channel) at each site. The line fiber — the dark fiber that is connected between the sites — then connects directly in to the transceiver, creating an end-to-end connection between the data center infrastructure at each site. It’s a simple solution, but one that contains some fundamental flaws.
- ELWL is typically limited to 10km by the OEM vendors.
- The fiber asset is unable to be used for any other data traffic.
- Operating expense (opex) for multiple fiber leases increases linearly per channel.
Embedded DWDM features the simplicity of the ELWL approach but with the benefit of being able to transport many traffic signals over a single dark fiber. The ELWL transceiver is replaced by a DWDM transceiver that is connected directly in to the host switch. Instead of being connected on to the line fiber, the DWDM signals are connected by an LC patch cable to a passive multiplexer. As the signals are multiplexed, they are gathered and transported together over a single dark fiber link, providing a much more efficient solution for connecting, for example, data center infrastructure at different sites.