RFP activity boosts ROADM development

Reconfigurable optical add/drop multiplexers (ROADMs) are the new hot topic in the industry, thanks to a flurry of carrier RFPs and a plethora of vendors showcasing their ROADM components and subsystems at OFC in February. The buzz is reminiscent of the hype surrounding tunable lasers a few years ago. Once touted for their ability to deliver dynamic provisioning on the fly, tunable lasers are still used mostly for inventory management and sparing. The industry continues to wait for prices to drop and the technology to mature before widespread deployment can occur. Are ROADMs destined for a similar fate?

Five years ago, the big promise of an ROADM was its ability to deliver optical wavelength services. "Everyone was going to have an optical signal to their business," recalls Rob Lane, vice president of marketing and business development at ROADM startup Tropic Networks (Ottawa). "But that didn't quite happen as it was planned five years ago, so ROADM started to get a bad name for itself." He believes ROADMs have reemerged now because the business case has fundamentally changed. While ROADMs will still be used to deliver wavelength services in the future, today they are viewed as a means to efficiently scale the underlying infrastructure.

Most carriers feature a stacked SONET ring architecture, but as bandwidth demand continues to grow, stacked SONET rings don't prove-in from a capital or operational perspective. While fixed OADMs solve some of the bandwidth capacity issues, they are not scalable enough to meet core network requirements, nor do they fit into existing operational support systems.

"But what if I could reconfigure those wavelengths and make the wavelength layer network look like SONET?" muses Ben Bacque, Tropic's vice president of product-line management. "It's a familiar operation model from the perspective of looking a lot like SONET, but now I can allocate a full line rate of capacity between any two sites on the ring. That's really what the evolution has been and why ROADMs are starting to make a lot of sense from the capex and opex perspective."

ROADMs deliver any-to-any connectivity and a single-wavelength granularity of add/drop without engineering involvement. "Carriers can drop wavelengths where they want, when they want, and they have complete control over that essentially from a keyboard," notes Paul Bonenfant, chief architect at Photuris Networks (Piscataway, NJ). Any-to-any connectivity not only simplifies the network by removing jumper cables from the provisioning process, but it saves carriers from having to dispatch engineers and equipment to the field for manual provisioning. With an ROADM, carriers can pre-engineer their networks to take into account the number of amplifiers and optical filters, for example, as well maintain an optimum optical-signal-to-noise ratio and ensure the residual dispersion is within the normal operating bounds of the transponder.

Adaptive per-wavelength power control is another critical feature of the ROADM. "If I don't know where the wavelengths are going beforehand, I need to have an adaptive power management scheme that will automatically control the power levels for me, making sure my optical amplifiers are happy and the power arrives at my transponders at the appropriate level," says Lane. The ROADM adapts to variations in power levels as well as simple fiber bends, stresses induced along the fiber, temperature-related effects, and defective or non-ideal components.

Photuris co-founder and marketing vice president Ashish Vengsarkar believes carriers are serious about implementing ROADM technology for two reasons. First, he says, carriers are under constant pressure to reduce operating costs. A recent RHK report indicates that carriers will need to reduce their operational expenditures by 32% annually to succeed in the current market. "As a result, carriers are looking for ways to scale the network operationally and simplify the network by combining different elements into one," he explains.

Vengsarkar also cites the maturity of the supply base and the availability of components and subsystems necessary for ROADM development. The recent OFC exhibition was a testament to this fact. PhoXtal Communications (Kista, Sweden), for example, launched its OADM wavelength switch, Alphion (Eatontown, NJ) unveiled the Photonic 2R (P2R) transponder, and Polychromix (Wilmington, MA) introduced the Dynamic Channel Orchestrator (P-DCO), which the company claims is currently shipping to tier one systems houses. Lynx Photonic Networks (Calabasas Hills, CA), meanwhile, demonstrated six new products in its LightLEADER 3000 family of photonic switches, including the LL-3515 and -3511, which can be used to add reconfigurability to static OADMs. JDS Uniphase (San Jose, CA) discussed its ROADM work at the show as well, and sources at Gemfire (Fremont, CA) say they've received ROADM inquiries focused on their variable-optical-attenuator technology and the planar-lightwave-circuit expertise recently acquired from Avanex (Fremont), which has been working on ROADMs for several years itself.

The declining cost of components is also enabling further development of ROADM devices. According to Tropic's Lane, there is still an incremental price difference for reconfigurability—roughly a 10–20% premium. "That premium is obviously very different from what it was a few years ago when the [cost of] ROADM componentry was somewhere between two and five times that of fixed componentry."

Not all ROADMs are created equal, of course. In fact, there are almost as many different ways to achieve the ROADM functionality as there are ROADM vendors—and the market is about to get even more crowded, as those who don't currently offer ROADM technology will likely develop it. In addition to startups like Photuris, Tropic, and Movaz Networks, the big names in the DWDM market include Nortel Networks,

According to the vendors, carriers are expressing genuine interest in the equipment. Photuris claims to have equipment in three RBOC labs today, for example—no small feat when you consider that "the RBOCs don't have the resources right now to experiment with new technologies just for the heck of it," says Vengsarkar. Photuris made headlines last September when Verizon chose its V32000 optical distribution system for use in a new network connecting multiple nodes at Texas A&M University and other sites in the metro area of College Station, TX. The industry's first live deployment of an ROADM, the device has been running live traffic error-free since last August. Photuris could parlay this successful deployment into a longer-term contract; Verizon has issued a metro DWDM RFP that reportedly includes ROADM technology.

SBC has had a DWDM RFP on the table for some time, and it specifies ROADM functionality as well. MCI, meanwhile, recently announced a nationwide DWDM long-haul network and two suppliers, Siemens and Ciena, both of which feature ROADM functionality in their systems.

Despite the spate of RFPs, there are some who remain skeptical about the carriers' deployment plans, at least in the near-term. The folks at JDS Uniphase, for example, are "somewhat dubious," admits Jo Major, senior vice president and general manager of JDSU's Component Product Group. While he agrees that every RFP he has seen requires ROADM functionality, "it's a bit of a stretch to imagine [carriers] putting that functionality into every node," he says. "We think the architectures that go in will be a mixed model for a while. There will still be a lot of play for fixed OADMs because they will be cheaper than the full-blown functionality of the ROADM for a while."

JDSU examined the elasticity of the market and found the current demand to be rather small. "We're assuming—and we're getting validation from the customers—that as the price for the functionality goes down, the interest in the functionality itself goes up," Major reports. "As the price of an ROADM drops, how far can ROADM functionality be pushed into the network? And the other thing is, as the price for the ROADM starts to drop, we find that it starts to compete against traditional OADM technologies in the node."

Major agrees that the economic argument for ROADMs is akin to that of tunable lasers. "It's our belief that as soon as the availability of tunable lasers increases and the price points are comparable to fixed-wavelength solutions, there will be a very dramatic market shift." Sounds eerily like the arguments of a few years ago.

Meghan Fuller is the news editor at Lightwave.

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