When embedded WDM networking isn’t possible
As we have seen, embedded xWDM (CWDM or DWDM) networking offers a simple, easy to manage and cost-efficient solution for transporting large amounts of data over short to mid-range distances. Today (2020), standard transceivers are available for up to 400G Ethernet and 32G FC connectivity with xWDM functionality. This means that as long as the data switch accepts these, an embedded CWDM or DWDM network can be built.
Still, there are certain circumstances that don’t allow embedded networking and you need to take additional steps to build an xWDM network. Some of these scenarios are:
- When the selected data switch vendor has CWDM or DWDM transceivers in their equipment but does not allow alternative transceivers from other vendors to be used, or if a switch vendor has not verified CWDM or DWDM transceivers in their equipment and does not have them in their portfolio. In both instances a third-party transceiver can be used. A third-party transceiver, often referred to as a compatible transceiver, can be used to make the connection. The challenge is that this might cause problems if something goes wrong in the networking setup. Switch vendors tend to limit the support to solutions involving non-verified components, making it a risky option.
- When a signal needs to be encrypted over an optical network. Since optical transceivers do not support encryption, an alternative solution is needed.
- When an internet service provider needs to hand off a grey (i.e. non-xWDM) signal to the end user, a setup that is in many cases used by ISPs to control or even restrict the bandwidth of the optical connection.
- When a preferred transceiver form factor used in a data switch does not support CWDM or DWDM. While standard transceivers, typically offer the perfect fit for data handling and transfer within the data centers, problems arise when traffic needs to be transported in an efficient way over longer distances since xWDM is not supported.
- When transporting 100G signals over a DWDM network. Until recently the only 100G transceiver type with DWDM support was the CFP. The challenge is that due to its large size, by optical transceiver standards, not many data switch vendors use it with their equipment, opting for smaller, more popular QSFP transceivers. This means that an alternative solution is needed to convert the transceiver output signal to a DWDM signal for long-haul connectivity.
Transponders and muxponders address the limitations of embedded solutions
For each of the described scenarios, the alternative to creating an embedded xWDM solution is to deploy an active transponder-based solution. With the help of a transponder, the short-range SR/LR signal from the switch can be converted to a long-range xWDM signal via a so-called optical to electrical to optical (OEO) conversion. The converted xWDM signal can then be transmitted over an optical fiber with the help of transceivers and multiplexers. Transponders also support encryption of the traffic.
Transponders make the ideal solution for any of the described challenges: for the ISPs who needs to hand off an SR/LR signal to their end user, when an encrypted signal is required and for overcoming situations where transceivers for CWDM or DWDM are for some reason not an available option.