Optical's Metro Reach
Smart, cheap silicon to drive metro optical networking
By David Iler
from the April 16, 2001 issue of Broadband Week
"Smaller, faster, cheaper" historically has been the rallying cry for silicon chip makers, but for those addressing the sprawling optical networking sector, "smarter" is becoming just as important an attribute.
Despite slowdowns in capital spending by large network operators, growing consumer broadband demand and an anticipated surge in enterprise bandwidth use is driving technological innovation for the silicon powering optical networking components.
As pure optical switching techniques slowly mature and technologies such as Dense Wavelength Division Multiplexing migrate from long haul to metropolitan and access networks, gear makers will be turning to silicon providers who can offer more integration, functionality and intelligence at the chip level.
The move of DWDM and other optical technologies to the metro model is dependent, Aberdeen Group analyst Elizabeth Bruce suggests, on declining costs for long-haul and ultra-long-haul components dropping. At the same time, the advantages of optical technologies in both the metro and access portions of today's telecom networks make the overall pie bigger for components and silicon makers, says Jeremey Donovan, principal analyst for Gartner Dataquest.
The industry's enthusiasm for silicon answers to optical systems is reflected in an announcement from optical semiconductor start-up Genoa Corp., which on the day the tech-heavy NASDAQ fell below 2000 for the first time since 1998, announced it had raised $75 million in venture financing. On the same day, the Fremont, Calif.-based company announced customer tests of a single-chip linear optical amplifier.
The chip is targeted for optical cross-connects, high-speed routers, optical add-drop multiplexers, transponders and DWDM systems, particularly in metropolitan applications.
Genoa's funding illustrates the need to more intelligently manage the rivers of data that flow through networks. Seizing upon this opportunity, start-ups and firmly established chipmakers are racing to bring to market optical silicon technologies for optical networking gear.
Chip giant Intel Corp. has aimed its considerable might at the goal of giving original equipment manufacturers the building blocks to allow service providers to maximize the revenue potential of their networks, according to Tony Stelliga, general manager, strategic marketing and business planning for Intel's telecom components group. Intel recently introduced seven optical networking semiconductors designed to add extended reach to optical transmissions. Two of the chips are "digital wrapper" devices capable of transmitting and receiving data over multiple communications protocols, including Asynchronous Transfer Mode (ATM), Gigabit Ethernet and packet over SONET (Synchronous Optical Network).
These chips also utilize Intel's version of Forward Error Correction, a technique which corrects errors that corrupt data packets as they traverse long distances on a network. Intel's FEC supports the 10 Gigabit per second data rates (OC-192) that are becoming more and more prevalent on telecom networks.
In addition to long haul applications, the importance of FEC, says Stelliga, is that it can "reach beyond the footprint of a currently budgeted plant," to reach customers without adding amplifiers or other components, or leasing fiber. SONET rings typically are constructed within 20 kilometers of a central office, making customers outside those rings--and outside the reach of traditional transceivers--lost to the operator. FEC functionality, built into line cards that reside behind optical transponders, lets operators capture those enterprise customers.
Yet FEC can add significant overhead to data transmissions. But Stelliga contends, "Service providers are willing to sacrifice bandwidth for reach." He adds that with FEC, operators can more easily create point-to-point networks instead of more expensive SONET ring topologies.
Plus, with FEC functionality in the line cards that make up network nodes, "we know where errors are occurring," says Stelliga, thus adding performance monitoring to FEC's list of credentials. The new chips are part of Intel's Internet Exchange Architecture, which counts Internet business infrastructure provider Narus Inc. as a customer. Intel also has customers, which it won't identify, who use its platform for high-performance legacy optical cross-connects.
Management of the electrical signals that traverse today's networks is the focus of Burnaby, British Columbia-based PMC-Sierra, a well-established chip supplier that counts Cisco Systems, Lucent Technologies, Nortel Networks, Ciena and Juniper Networks among its customers. In February, the company released a packet processor designed to provide intrusion detection, load balancing and Quality of Service in Internet Protocol switches and routers.
Steve Perna, PMC-Sierra's vice president and general manager of its optical networking division, says his company's focus is on metro network applications. MANs offer unique challenges because of the multiple data rates and protocols that either are handed off or directed to the access portions of networks its core. Perna says the company is designing chips that can handle both multi-protocol, low-speed access network traffic in addition to wavelength-based traffic at the metro core at rates from 2.5 Gbps to 40 Gbps.
PMC-Sierra's latest processors are designed to provide the ability to groom or manage lower-speed access traffic into an optical network, with the help of an optimized packet inspection engine and classification algorithms. Earmarked for switches, routers and service management gear that resides at the edge of metro networks, the new processor also includes support for Virtual Private Networks and e-commerce security.
Seeking to bridge the electrical domain, where packet processing at optical nodes and cross-connects occurs, and the optical domain, is Conexant's Mindspeed Internet infrastructure business. Earlier this year, Mindspeed's Integrated Circuits for Optical Networking Group (ICON) introduced a crosspoint switch device using semiconductor technology that it says allows 136 independent channels to switch traffic at 3.3 Gbps per channel.
Despite the attractiveness of pure optical switching, particularly for very high-speed network configurations, Achim Hill, vice president and general manager of Mindspeed's ICON group, points out "there's still a large market for electrical switches," that would among other things perform restoration functions. Mindspeed's high-density crosspoint switch devices use clock data recovery (CDR) to clean up signals and require a low 9.5 watts of power.
Mindspeed also has introduced semiconductors that can implement resilient packet ring (RPR) technology for IP ring-based metro and intra-point-of-presence networks. According to Mindspeed, both Cisco and Nortel have promised support for RPR technology.
Trying to capitalize on the growth of single-mode fiber optic components, Agilent Technologies in March released a 2.5 Gbps, small-form-factor fiber optic transceiver targeted for short- and intermediate-reach SONET links. In addition, the company's 68-by-68 port, 3.125 Gbps cross-point switch is designed to push higher capacity and high data rates in the metro market by aggregating OC-48 links within the metro core, according to Christine Liu, Agilent's product marketing manager for integrated circuits.
Tom Fawcett, marketing manager for Agilent's optical systems interconnect, expects the metro market to explode just as bandwidth demand in the enterprise has, and will leverage its expertise in Gigabit Ethernet transceivers for the enterprise market as Gig-E becomes more and more prevalent in metro applications.
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