At the Optical Fiber Communication Conference here today, Silicon Valley startup Xros, Inc. (pronounced KAI-ros) announced the world's highest capacity optical cross-connect system for open optical networks, based upon the company's revolutionary silicon-based micro-mirror technology. The system addresses a crucial business problem faced by the telecommunications providers today: remaining competitive as they grow their networks in a rapidly-changing market environment.

Optical cross-connects are used in the "core" of the worldwide telecommunications network to connect high-capacity fiber optic communications channels coming into a particular location or "node" with any of hundreds or more outgoing channels. Their principal application is "provisioning" a circuit - the semi-permanent connection of numerous intermediate links to create a continuous pathway between endpoints anywhere in the network, and "protection" - the instantaneous re-routing of a circuit in the event of a catastrophic failure of an intermediate link.

The new Xros system, designated the X-1000, is capable of arbitrarily connecting up to 1152 pairs of inputs and outputs with an all-optical pathway from each input to output. The all-optical pathway makes the cross-connect completely independent of both the transmission speed or "bit rate" of the data, and the underlying format or "protocol" of the data. Such independence, often termed "transparency," is extremely desirable in a cross-connect, for it supports the notion of the optical network as an open system, into which a wide range of diverse equipment can "plug and play." Connections are established on demand, in less than 50 milliseconds, making the Xros cross-connect ideal for both provisioning and protection applications.

"Carriers are desperate for optical networking flexibility," said Dr. John Ryan, principal and chief analyst at RHK. "Provisioning lightpaths - either to build out the network or to respond to specific customer needs or competitive forces - can take upwards of six months today." Ryan adds, "the ability to instantly reconfigure the network means that carriers will be able to deploy their capacity where and when it is needed - enabling a wide range of new service offerings while simultaneously giving them significant operating economies."

The same capabilities that make the Xros' transparent optical cross-connect ideal for provisioning gives carriers a whole, new set of attractive options when designing protection schemes into the network to preclude interruption of service. "Protecting the network against widespread service outages due to fiber cuts or other such catastrophes is extremely expensive," said Ryan. "For such protection, the carriers keep on standby an amount of capacity nearly equal to that earning revenue, as well as require very expensive and specialized switching equipment. These inefficiencies drive up cost."

With the Xros cross-connect - where an incoming lightpath can literally be switched in a small fraction of a second to any of over 1100 outputs, planners can create a network architecture where dozens to hundreds of alternative paths are available to protect each link, rather than a single, redundant path that is kept "dark" until it is needed. According to Ryan, "shared protection capacity can permit more of the network to be revenue-producing, which can dramatically change network economics."

It's Done With Mirrors

At the heart of the Xros cross-connect is an all-optical switch core based upon a revolutionary micro-mirror technology invented by Xros, which is ideal for optical telecommunications applications.

Using two facing, 6-inch by 6-inch arrays of 1152 mirrors each, any incoming beam of light may instantly be directed to any destination by reflecting it off of two of these tiny, movable mirrors. In this way, an entire fiber optic communication channel, or "lightpath" entering by any input port may be switched as a unit to any specific output port, with essentially no losses, and no requirement to examine the underlying data.

The Xros mirror - about the size of a baby's fingernail - is fabricated out of pure silicon - the same material used in most micro-chip manufacture, and yields a highly-reliable device which can instantly be tilted in several dimensions by computer-controlled electrical signals, to a precision of one five-millionth of a degree. The Xros technology is the subject of numerous patent applications. According to Xros president and CEO Greg Reznick, the mirrors are "completely unique" and a "substantial improvement" over all prior attempts at mirror-based switching.

The Importance of Optical Cross-connects

Before fiber optics revolutionized telecommunications with virtually unlimited bandwidth availability, electrical-based circuits were switched with electronics - transistors specifically - and, prior to that - with electro-mechanical devices, such as reed switches or relays. However, while the technology for switching electrons (which is the foundation of every aspect of the electronics revolution) is mature and well understood, a commensurate technology for switching photons - the particles making up a beam of light - has been elusive.

As a consequence, cross-connects in the optical network have been forced to convert incoming optical signals to the electrical domain, switch them electronically, and then re-convert them back to light for output. This conversion, which is known in the industry as O-E-O for "optical-electrical-optical" vastly complicates optical cross-connect equipment, as the conversion must be performed on each of hundreds to thousands of input/output channels. Such additional complication has severe financial and logistic implications.

A true or transparent optical cross-connect switches the beams of light directly, such as with micro-mirrors, the technical breakthrough at the heart of Xros' system. This permits high-bandwidth optical data streams to pass through the cross-connect transparently - without necessitating any conversion to electronics. A particular and unique feature of Xros' transparent optical core is that it is scaleable, unlike previous attempts at optical switching. A scaleable system is one where if you need, for example, to double your capacity, you will require no more than twice the amount of equipment.

Both O-E-O approaches, as well as previous all-optical approaches, have not been scaleable. Either they suffered from fixed upper limits on capacity, or the complexity and cost of the equipment simply exploded out of the realm of the feasible when certain port counts were reached. This, in turn, has limited the ability of network planners to design an efficient, cost-effective optical core.

The Demand for True Optical Cross-connects

The compelling demand for true optical cross-connects of considerably high port capacity has arisen because of three trends.

First, because of recent technological breakthroughs in fiber optics - which have in some cases increased the capacity of existing fiber 100-fold, the core optical network has enjoyed a huge jump in total capacity without the necessity of laying additional fiber, a process which once accounted for 90 percent of the cost of building out the network. Additionally, new carriers have arisen that are installing new fiber - tens of thousand of miles of it - which adds to the core capacity. And finally, the communications revolution, as typified by the Internet explosion, has created an exponentially growing demand by end users for access to this capacity. As a case in point, each one percent increase in the number of DSL (Digital Subscriber Line) subscribers doubles the total traffic in the core of the network.

With these trends, it is crucial for carriers to be able to design and operate networks with substantially less than 50% redundancy built in for protection. They also need to be able to offer and provision new service "on demand", rather than with 6-month's lead-time. Finally, they require a future-proof, open optical network, which can grow smoothly, regardless of the nature of the data being transmitted or the source of the equipment being used at any point.

Pioneer Consulting, a Cambridge, MA telecommunications market research and analysis firm, estimates the worldwide market for optical cross connect systems to be $543 million in 2000, growing to $15 billion by 2004.

The Xros X-1000 Open Optical Cross-connect System Xros' new X-1000 is the first in a series of systems that reflect the company's strong commitment to open optical networks. The X-1000 is a standalone, scaleable, 1152x1152 transparent optical cross-connect system provided in three NEBS compliant telecommunications equipment bays. The system is fully redundant, and provides protection in less than 50 milliseconds.

The X-1000 supports standard single-mode optical fiber via standard optical port connectors on the front panel. The system incorporates state-of-the art management software to enable users to simply deploy and operate the X-1000 in their network. Power consumption is less than 1 kilowatt per bay, about one-third of the best available O-E-O cross-connect.

The X-1000 cross-connect system is completely scaleable, four ports at a time, starting from 4x4 ports all the way up to 1152x1152 ports. Xros is expecting to ship evaluation systems in September, with production availability by January, 2001.

"Xros has created for the carriers a future-proof system of unprecedented flexibility," said Reznick. "Not only has our cross-connect increased the port density by 2-to-4 times over any other solution, but we have simultaneously provided a truly scaleable, all-optical system with a dramatically lower cost per port, an incredibly small footprint for the capacity, and modest power requirements."

http://www.xros.com