The universe of infrastructure equipment makers and service providers can be divided into two types of people: those who believe optical switching technology will play a major role in the construction of next-generation networks in the immediate future, and those who think it will happen even faster.
Whether optical technology's ascension to network supremacy happens tomorrow or the next day, it's becoming increasingly clear that the Internet is growing so fast that nothing short of the speed of light will be able to keep up with it.
"If you think of how the network is growing, it needs to scale by thousands and thousands of times," says Jack Wimmer, vice president of network technology and planning at WorldCom.
The adoption of optical switching equipment, which is designed to divert wavelengths of bandwidth across the core of the Internet without first converting the information into an electronic format, is not just about accommodating growth. Although the public network must become bigger and faster, it must also be smarter and less expensive to operate.
'Lite' switch
To fulfill this triple-headed promise, optical switch makers are already beginning to optimise their equipment for certain types of applications and for deployment in specific parts of the network. Ciena, one of the first equipment makers to recognize that all optical switches are not created equal, earlier this month introduced a scaled-down version of its CoreDirector for midsized networks and the metropolitan area of the public network.
"Several carriers were looking at what we could do to push the benefits of the CoreDirector into smaller parts of their network," says Rick Dodd, director of marketing at Ciena. "We're taking the exact same software and packing it into a smaller form factor."
While Ciena might be the first of the handful of optical switch makers to introduce a complementary product, several start-ups in the past few weeks have unveiled optical switching products aimed at addressing a variety of growth issues in all four corners of a carrier's network.
Perhaps the most vexing of these problems is scalability, which describes an optical switch's ability to handle an increasing number of connections, or wavelengths, without requiring replacement of the entire system. In other words, scalability is a measure of a system's ability to grow.
Last week, newcomer Calient Networks introduced an all-optical switch designed to grow from about 1,000 ports to tens of thousands of separate connections.
"We build a technology that can pass a thousand beams of light in the volume of a sugar cube," says Tim Dixon, vice president of marketing at Calient. When the cables and other accoutrements that go into an optical switch are added to the mix, Calient's 1,000-wavelength system is roughly the size of a drawer in a kitchen cabinet, Dixon says. He claims Calient's Scalable Control of a Rearrangeable and Extensible Array of Mirrors technology ensures that the switch is several times smaller than the closest competitor's.
While the ability to support about 1,000 wavelengths is currently adequate for even the largest Internet junction point, where these switches will be required to sort out the jumble of optical circuits converging on regional data centers, major carriers will quickly outgrow those switches. Wimmer says WorldCom will soon require optical switches that can handle tens of thousands of wavelengths at a time.
For this reason, carriers appear to be leaning toward all-optical incarnations of optical switches for the backbone of their networks. Alcatel, Calient, Corvis, Lucent Technologies, Nortel Networks and others are working on optical switches based on tiny mirrors or some other type of passive technology that enables a wavelength from an incoming fiber to be switched to an outgoing fiber without converting the information in the signal to an electronic format.
The alternative to an all-optical switch is one that does a quick optical-to-electronic conversion in order to change the frequency of the wavelength carrying the data or to manipulate information inside the wavelength. BrightLink Networks, Ciena, Cisco Systems, Sycamore Networks and Tellium manufacture so-called optical-electronic-optical (O-E-O) switches.
The consensus in the industry is that all-optical switches are a better match for the network core because of their ability to scale and to accommodate a variety of traffic types and transmission speeds. By advocating an all-optical, or photonic, network foundation, Calient officials say carriers can eliminate the constant need to replace electronic-based gear.
The problem with electronic-based gear is that it is sensitive to changes in protocols and in the bit rate of optical transport gear. For example, a switch designed to handle wavelengths that operate at OC-48 (2.5 gigabits per second) could have to be upgraded or even replaced when carriers move up to OC-192 (10-Gbps) speeds.
Insurance policy
"Those switches differ because their ports are electronic and based on a specific bit rate," WorldCom's Wimmer says. "That proposes a challenge."
The primary shortcoming of electronic-based switches is that they must comply with the parameters of Moore's law, the computing axiom that states that the performance of a microprocessor doubles about every 18 months. While businesses and PC enthusiasts could weather the costs of replacing a PC every other year, the strain of a biannual infrastructure overall is just too much for a carrier to absorb.
"Things are moving so quickly that carriers have to churn electronic gear every two years or so," Calient's Dixon says. "It's killing them. With optical gear you don't have to deal with speeds and protocols. It's gives them an insurance policy for the future."
Many industry experts have also identified the lack of scalability as a limiting factor for O-E-O switches in the network's core. but at least one O-E-O switch maker, start-up BrightLink, claims its hybrid switch will scale well beyond 1,000 wavelengths.
As a result of the lack of flexibility and bit-rate transparency of O-E-O switches, several equipment makers see opportunity in the metro area of the network for these hybrid devices. Ciena's CoreDirector CI, for example, could be deployed in the metropolitan portion of the network to aggregate traffic from Synchronous Optical Network rings, Dodd says.
Wimmer sees the O-E-O switches having greater value in the metropolitan area than in the core. Deployed in metro environments, these types of switches would be suitable to supply bandwidth management and to aggregate customer traffic by replacing existing SONET gear, he adds.
Equipment makers also see a role for all-optical switches in the metro area. Earlier this month, Sorrento Networks and newcomer Network Photonics unveiled product plans for all-optical switches targeted at the access portion of the network.
"In the metro area, the protocol transparency is important," says Scott Clavenna, an analyst at research group Pioneer Consulting.
Several analysts consider O-E-O switches an interim step in the optical switching evolution. Based on familiar technologies, these switches are at least a year ahead of all-optical switches from Lucent, Nortel and others.
However, several makers of O-E-O switches, including Cisco, Ciena and Sycamore, have not ruled out the possibility of replacing their hybrid switching fabrics with an all-optical design down the road. The true value of their technologies, officials at these companies say, is wrapped around intelligent software, designed to provision optical circuits across the core of the Internet on the fly. Trading electronic switching components for all-optical gear would be a logical transition, they say.
