Programmable WDM

Open, disaggregation and programmability are now finding its way in optical transport networks. It allows the automation of the configurational and operational tasks on disaggregated photonic components, which are complex and analog in nature.

Network operators and service providers want their optical network to support multi-vendor interoperability and the disaggregation of software and hardware platforms. The main challenge is in taking care of the optical impairments (e.g. optical signal-to-noise ratio, modulation, cross talk, dispersion affect etc.) across the multi-vendor optical equipment. Because of this, every vendor has their own set of algorithm to configure the optical parameters of their set of system components, for a particular optical channel.

So, to manage these optical impairments across the multi-vendor equipment requires a standard algorithm to be followed across the optical components and that is possible when all optical hardware components expose their standard APIs to a common interface module and should also support standard protocols to exchange configurational and operational parameters.

Over the period of time, operators deployed multi-channel capacity (i.e. 2.5G, 10G, 40G, 100G and beyond) of optical networks and also multiple technologies e.g. ROADM, CD, CDC etc. to transport their optical traffic over different silos network. Each of their cluster networks is vendor specific and interoperability between the silo network domains is the biggest challenge for them.

To address these challenges, there are some models which are widely discussed in a number of open community forums, where the idea is to manage and control the transponders and optical line systems independently. So if line system is closed i.e. vendor specific, it should operate with any transponder or the transponder should operate with any optical line system. This is something called a partial disaggregation where a transponder is one system and complete line system act as another system and both these systems are controlled by a common controller module.

Another solution is complete disaggregation of the transponders and the optical line system components where every optical component provides an abstraction for optical functions to the common controller module.

For brownfield deployments (e.g. typically NLD networks), the OLS components remain unchanged and transponders will keep on augmenting as and when capacity enhancement takes place. Therefore, for this particular case, the open transponders would be a good fit and OLS as a vendor-specific unit shall be controlled by vendor-specific controller only. Further, both Transponders and vendor specific controller shall expose their API’s to a common controller module in order to provide seamless end-to-end control of the optical network.

On the other side, for Greenfield deployments, fully disaggregated system will be an effective solution, as it will provide vendor independent design, planning, provisioning and performance. Also, the end-to-end control on every optical component assures the enhanced performance and better network health.

Figure 1: Conventional & Next Gen Architectures of Optical Transport Networks