Colorless Wavelength Switching - Is It Enough?

Service providers have traditionally used ROADMs (Reconfigurable Add-Drop Multiplexer) for colorless wavelength switching. ROADM's allow optical network operators to switch any color wavelength on a single fiber to connect to any add-drop transponder that is associated with that fiber.  Using Wavelength Selective Switches (WSS's) some service providers have added directionless capabilities.  However the complexities of implementation, provisioning, management and maintenance have severely limited this architecture. 

Ever increasing bandwidth demand (at a lower cost per bit), more stringent customer demand for network services that are reconfigurable and even more reliable, and continuing operational cost pressures are forcing service providers to seek even more flexibility, servicablity and reliability from their optical infrastructures.  As a result, they are continuing to pursue new ways to make their networks more efficient and cost effective.

At this juncture, service providers are looking a three possible architectures. 

1. Colorless (Status Quo)- any color wavelength on a single fiber can connect to any add/drop transponder associated with that fiber. 
2. Partial Colorless/Directionless - a compromise architecture with some level of blocking such that not all of the waves on all of the fibers can always connect to all transponders. A cost reduction only solution.
3. Colorless/Directionless/Non-Blocking - extends the concept to any color wavelength on any fiber from any direction. All can be connected to any add/drop transponder, with no blocking.

 

Each approach has its strengths and weaknesses.  In our next blog, we'll review the plusses and minuses of each approach, and why we believe that Colorless/Directionless/Non-Blocking is the ultimate goal.