They allow access to any of the wavelengths going through a node (or, in more limited R-OADM implementations, access to a set of the transiting wavelengths) for use of the data on the chosen wavelength and the possibility of adding to, or modifying, the data on that wavelength for transmitting it on to the next node(s). They also allow the interconnection of multiple intersecting networks (multiple degree nodes) at the optical level, avoiding the expense and complexity of OEO conversions to achieve the interconnection. The device offers the promise of substantial savings in operations costs, and many operational benefits.

We have been writing about R-OADMs and their coming importance almost since the beginning of the technology. This is the fourth R-OADM report in our Lightwave series. Four years ago, we prepared our first report on R-OADMs - “R-OADMs - the Lightwave under Control.” At the time, very few authors were writing much about R-OADMs. As stated in that report it was, “… a report about a device that did not exist; whose technology was unselected; and whose market was very unclear.”

We followed our first report on this subject with a new discussion a year later with “R-OADMs - Still Here in 2004!” By then a few of the smaller DWDM system vendors had a Reconfigurable Optical Add/Drop Multiplexer (R-OADM) offering, none of the major vendors (90%, or so, of the total market) had yet announced a product. Our next update, a year later, (“R-OADMs - Key to Upgrading the Newly Merged Networks,”) of that report noted, “Every major system vendor has a R-OADM offering, and more are on the way. This is very good timing because the RBOC-IXC mergers of early 2005 will require a great deal of network consolidation, and R-OADMs will be key.”

Now in early 2008, the R-OADM has become a standard part of long-haul networks - to be included as a matter of course in any new network, and they have become a major update objective for existing networks. They have also become of important to metro networks. Now the application that is driving cost savings is the use of low cost ROADMs on the Edge of the network. (See the material on Nistica, particularly, in the Systems Vendors' section.) In addition to the maturity of application, R-OADMs have also developed a third generation technology base - the Wavelength Selective Switch (WSS) that has quickly become the ‘gold standard.'

This is a complete update of our earlier reports with an emphasis on WSS, and how the WSS technology approach to R-OADMs will facilitate the interconnection of multiple networks. The interconnection of long haul and metro networks takes on a new importance with the SBC-ATT-BellSouth and Verizon-MCI mergers. This report contains completely new forecast scenarios, expanded technical material, many added vendors, and updates on deployment activities since the previous work. It also includes new material on Wavelength Selective Switches, and many more figures, explaining the various types of approaches available for R-OADMS. This is a completely stand-alone report, containing all of the background material from the earlier reports.

A number of technologies are involved in the R-OADM. The report presents several different architectures, with an emphasis on WSS but also including the switch version and the broadcast version. Technologies involved in each approach are described. The vendors associated with the various approaches are identified, and market forecasts are developed on a component/subsystem level as well as on a system level.

There are many applications for the R-OADM. The applications of various degree nodes (‘two degree nodes' for example have two fiber routes, three degree have three, etc.), that are common in the network are depicted. As will be noted, some of these applications will have particular use in merging the long-haul networks of the IXCs and the metro networks of the RBOCs.

The main market driver for R-OADMs is the desire to save operating expenses by the carriers. The new video thrusts by the major combined RBOCs are a new driver to R-OADM deployment. These companies are in the process of deploying nationwide networks to deliver video on their fiber access local networks. R-OADMs are the perfect adaptation to control these video distribution services. In addition, the forecasted increase in wavelength services is going to greatly facilitate the deployment of networks based on R-OADMs.