Until recently, Optical networks were hard to change. The routes traffic took were fixed and inefficient and bandwidth was not being optimised. That was until Reconfigurable Optical Add-Drop Multiplexers (ROADMs) came along.
Before ROADMs, optical network operators have faced the challenge of extending and modifying their networks. A ROADM is a piece of software that provides the ability to remotely provision traffic from a Wavelength Division Multiplexer (WDM), at the wavelength layer, without the need for network redesigns and can be done in almost real-time. This means that assigning how the entire bandwidth will function does not need to be done at the deployment stage – it can be configured and changed as and when it is needed.
When ROADM technology was first launched its functionality was as an add/drop design whereby one wavelength would be added or dropped from a network at a time, ROADMs can now route and reroute any wavelength in any direction – this is known as CDC-ROADM. Where previously ROADMs were only really used in long-haul Dense WDM (DWDM) networks, as the need for greater capacity has increased it is now also more commonly found in major metropolitan networks too.
ROADMs have a number of components to help ensure greater efficiency for a fast and responsive network:
- Wavelength Selective Switch (WSS) – this is the part that enables a wavelength to be switched. The network manager can route any wavelength to and from any port to seamlessly change connectivity as needed.
- Optical Channel Monitoring (OCM) – This monitors the optical power of each wavelength to ensure they are operating as efficiently as possible.
- Variable Optic Attenuators (VOAs) – configures the power level of each wavelength to minimise signal loss.