Reconfigurable Optical Add/Drop De-multiplexers (ROADMs) is the enabling technology for modern telecom network, where wavelength division multiplexed (WDM) signals can be flexibly routed throughout the network optically in a reconfigurable fashion.
Wavelength selective switches (WSSs) are the key building block of a ROADM. The ability of the ROADMap WSS module to simultaneously support multiple 1×N WSSs has several advantages in terms of the design of the ROADM. A ROADMap WSS module can potentially integrate all the Colourless, Directionless, and Contentionless (CDC) switching functions of a ROADM into a single, low loss, low cost module, which would enable network operators to scale up the capacity in a cost-effective way.
In the transit part of the ROADM as shown in Fig. 1, the wavelength division multiplexed (WDM) signals are currently being routed to any of the output directions by using multiple 1xN WSSs. A ROADMap stacked WSS module is able to integrate these independent 1×N WSSs into a single module. This results in significant cost, spacing and operating power savings.
At the add/drop part of the ROADM, multicasting switches are currently being used to either add or drop data from the core network to a local network. As illustrated in Fig. 1, a multicasting switch real can realise CDC add/drop features by pairing a splitter array with a corresponding space switch (SS) array. As shown in Fig. 2, a ROADMap WSS module (the blue block) is able to replace all the splitters in the multicasting switch. This will significantly reduce the insertion loss and therefore eliminate the need for additional amplifiers in both add and drop directions. Ultimately, the add/drop structure can be scaled up to higher capacity in an energy-efficient and cost-effective way.
A detailed case study can be found in our white paper, which shows three ROADMap WSS modules can be used to realise a four-degree ROADM with 96 CDC add/drop transponder ports
Data Centre Applications
Data centres are undergoing a rapid growth in both their storage and cloud computing capacity (12.5% and 35% CAGR respectively)1. Data centre operators are building multiple data centres in the metro areas and interconnecting them via high-capacity fibre links. Such data centre interconnect (DCI) networks allows shared resource utilisation that enables new services and operations in a flexible and cost-effective way. WSS and WDM technologies have been extensively used in DCI networks. The ROADMap stacked WSS technology platform is well positioned to suit the fibre-rich environment of DCI networks, where WDM signals need to be routed throughout the parallel fibres linking the distributed data centres.
Inside a typical warehouse scale data centre, between 50,000 and 100,000 servers are connected via several tiers of high speed electronic switches and single wavelength transceivers. There is increasing interest in adopting the same WDM technology used in the telecom industry for these fibre links. As in the case of telecoms, the use of multiple wavelengths offers a way of overcoming challenges related to data rate, fibre management, network costs, and power requirements. The WSS technology platform being developed by ROADMap Systems can also be configured to support a low-power switch routing 1000×1000 data channels, greatly exceeding the port count of current commercially available data centre switches.