on the roadm, again

IF SUPERCOMM 2005 IS ANY INDICATION, the momentum for ROADMs is picking up. More vendors announced support for remotely reconfigurable add/drop capability in their WDM product road maps while others logged carrier deployments. Cost continues to throw up roadblocks for the technology, but vendors are finding ever more creative ways to tear them down — greasing the skids for dynamic metro optical networks.

ROADMs support remote dynamic network reconfiguration on a per-wavelength basis without the need for a truck roll. They are designed to eliminate optical/electrical regeneration for pass-through wavelengths typical of first-generation DWDM systems and restriction of fixed optical ADMs, such as wavelength stranding, per-wavelength engineering and jumper cabling to interconnect filter packs, transponders and line interfaces.

Cisco Systems Inc. announced at SUPERCOMM more than 650 customers have purchased its two-degree ROADM solution, which was launched in October 2004 and is available on the Cisco ONS 15454 Multiservice Transport Platform (MSTP). “We have exceeded our expectations for how quickly it’s taking off,” says Rajiv Ramaswami, vice president and general manager of the optical transport group for Cisco.

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Mahi Networks Inc. also says it is gaining more traction with its ROADM-enabled Vx7 WDM system. Mahi, through its acquisition of ROADM pioneer Photuris last year, has been deploying ROADMs since summer 2003. Alan DiCicco, senior manager of product marketing for Mahi, says the company has 50 nodes deployed across seven networks in North America alone. The primary reason for the uptick, he says, is the move to provide Ethernet and video services. “Big, fat pipes need services managed at wavelength levels,” he says.

Indeed Mahi is convinced of the trend toward WDM in the metro and it plans to discontinue selling its SONET-based Mi7 Multiservice Core Aggregation System. “More and more traffic can skip SONET as a middle layer and go directly over waves,” DiCicco says, explaining the decision. He says the Mi7 technology will be leveraged as cards or a shelf in the Vx7.

Numbers from Infonetics Research Inc. confirm ROADM’s momentum. Worldwide ROADM revenue was more than $100 million in 2004 and is expected to nearly double in 2005 with continued explosive growth projected through 2008, the firm notes in a February 2005 report. “We expect to see the wholesale shift of core metro from fixed OADM to ROADM in most parts of the world by 2007,” says Michael Howard, principal analyst for Infonetics Research.

Indeed, ROADM’s ability to provision wavelength services dynamically lifts a barrier to WDM’s success in metro networks, says Rich Moran, director of product marketing for NEC America Inc.’s Optical Network Services Group.

NEC is leveraging its optical networking experience in core and long-haul networks to launch its first WDM system for metro and regional networks, the SpectralWave 4240. Initially, it will be available with a two-degree ROADM. In March 2006, a multidegree wavelength selectable switch (WSS) will be added.

Unlike other metro WDM vendors, NEC is taking its long-haul experience but not its product into the metro, Moran says, noting Spectral- Wave 4240 is a completely new system. It includes add/drop capability at any node, full-band tunable transponders, integrated SONET-on-a-blade multiplexers, and upgradeability to wavelength cross-connect configuration.

Among the functionality brought from the long-haul experience, says Moran, is the ability to manage the power of the optical signal, or automatic gain control. “This is something that has held metro WDM back,” he adds.

Philippe Morin, Nortel Networks’ general manager of optical networks, agrees. He says one of the downsides of switching waves is that the lasers’ dispersion limits can be reached. To address this, Nortel is adding electronic Dynamically Compensating Optics (eDCO) to its enhanced ROADM, or eROADM, announced at SUPERCOMM.

The eDCO dynamically adjusts the modulation of individual wavelengths when they are redirected to a new path, over a different fiber type, or over a longer distance. “Until you have the capability to dynamically compensate for dispersion, you can’t really deploy a ROADM network,” says Morin.

eROADM, which is under controlled release and will be generally available in October, is an upgrade to the version Nortel released last summer. Like its predecessor, eROADM is a functional module included in its 40gbps-ready Common Photonic Layer (CPL) platform. Instead of wavelength blocker technology, however, the new version uses a WSS to enable all-optical switching and redirection of a wavelength to up to five different rings in a network. “It’s completely ‘colorless,’” says Morin, explaining this means it can do branching or effect mesh networks.

Support for mesh networking via a multidegree WSS is the ultimate achievement for ROADMs. Equipment from Mahi, Fujitsu Network Communications Inc. and Meriton Networks Inc. already have such capability. NEC and ECI Telecom announced their systems would include it soon. Cisco also says it’s on its road map. “We absolutely are exploring mesh capabilities, and it’s something you can expect to see down the road,” says Cisco’s Ramaswami, noting 85 percent of today’s networks are rings. “We’d like to see the costs come down so they are more affordable and people will not think twice about deploying a mesh solution.”

In fact, he attributes much of the Cisco’s traction in the space — 90 percent of the filters purchased from Cisco in the last six months have been ROADMs — to not having charged a premium for the capability. “There has been a perception that ROADMs are a premium offering. Our view is that if ROADMs are priced on par with fixed devices, then it really becomes a no-brainer for people to deploy them,” he says.

For that reason, ECI Telecom announced at SUPERCOMM a range of ROADM solutions for its XDM 2000 MSTP/MSPP platform. The company will roll out at the end of the year a ROADM based on WSS as well as one using a wave blocker. While the blocker has less functionality than the WSS, it is more economical and it is sufficient for dropping up to 40 channels at hub sites, says Mano Nachum, ECI’s vice president of marketing for North America.

Meanwhile, he says ECI will continue to offer an entry-level pluggable ROADM whereby providers plug in a filter that can add and drop a wave. It cannot be managed remotely, but Nachum says the option provides a primary benefit — not requiring network preplanning — of ROADMs at around half the cost. ECI has filed a patent application for this installation solution.

Adva Optical Networking’s Per Hansen, director of business development, says ROADMs are not always necessary when traffic patterns are predictable. Adva is exploring development of a hybrid system that will allow carriers to migrate from CWDM to fixed DWDM and then onto dynamic DWDM when and if their traffic requirements dictate. “In many cases, service providers’ needs for fast return on investment goes against the fundamentals of ROADMs,” he says, explaining ROADMs require more capex upfront to gain engineering flexibility on the back end. “We want to enable carriers to start out with CWDM and static DWDM,” he says. “As traffic grows to a point that dynamic DWDM makes sense, they can do that.”

Mahi’s DiCiccio says ROADM’s cost issue is a red herring. “ROADM is both a component and a system description. As a component, a ROADM is more expensive, but more capable. But it also makes the rest of the system less expensive than fixed systems,” he says, noting the elimination of power monitoring, gain equalization and more expensive amplifiers. “ROADMs also provide service velocity. The network is engineered and deployed once. It’s the least stated but most important feature.”

Nortel estimates its new ROADM features can result in a savings of up to 55 percent in operating costs for service providers.