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Manufacturers ride the PON wave

Posted: 21 Jun 2007 ?? ?Print Version ?Bookmark and Share

Keywords:passive optical networks? PONs? IPTV? broadband PON? Wi-Fi?

It's June, and passive optical networks (PONs) has been busting out all over at the NxtComm telecommunications trade show in Chicago.

The success of Verizon Communications Inc.'s FiOS network is a factor in the explosion of interest in PONs. But there's also a growing realization among telephony carriers and cable TV multisystem operators that triple- and quadruple-play services must offer a full suite of TV optionsincluding an RF overlay for standard- and high-definition (HD) broadcast channels, as well as sufficient Internet Protocol bandwidth for IPTV.

'The only option'
While fiber based on active optics could provide plenty of bandwidth for any mix of services, a true active fiber interface to the home has been attempted only in Japan. PONs are the only other alternative for homes with multiple HDTV sets. A dedicated switched digital fiber interface could provide 100Mbps or more to each home. A PON line card offers 2.5Gbps downstream and 1.25Gbps upstream, split among one to 64 subscribers at a density that fits the carrier's profit plans.

"As consumers become familiar with HDTV quality, they add a second HD set in the home and all the assumptions of bandwidth break down," said Chris Bernard, engineering product manager at Zhone Technologies Inc. "DSL and traditional HFC [hybrid fiber coaxial] cable fall short. PON is really the only option."

North America has become a strong home for the International Telecommunication Union transition from first-generation broadband PON (based on an asynchronous transfer mode interface) to Gigabit PON (GPON). Asia is making an Ethernet-centric transition from EPON to GbE PON. A global company, whether an OEM or a chipset supplier, must be prepared to follow either track.

Two important nodes in the PON require standard silicon. To be cost-effective, the optical line terminal (OLT) at the central office usually requires multiple-channel PHY transceiver support, along with high-layer QoS traffic management. The optical network terminal (ONT) at the customer premises requires multiple processor cores for control plane, data path and DSP support. It also must be flexible enough to be used in an outdoor interface device on the side of a house, or in a residential gateway that might require Wi-Fi or security functions in the home. OLT and ONT devices can be very complex SoCs.

Segment players
PMC-Sierra, which acquired PON startup Passave Inc. last year, has turned to multiprocessing MIPS cores to handle advanced processing at low cost. BroadLight Inc. has moved to a PONrunner ONT chip with dual data path processors, a MIPS control plane core and a DSP for VoIP.

Gigabit PON lowers FTTH costs with premium triple-play services.

The PON infrastructure between central office and residence requires only splitters and wave-division mux combiners. While the equipment is simple, Zhone Technologies considers passive elements important enough to offer them to customers through an OEM partner.

NxtComm activity this year is skewed toward GPON, but EPON is by no means dying. Network processor supplier Cortina Systems Inc., which acquired PON startup ImmenStar last spring, will launch an EPON-based suite of optical-line-terminal and optical-network-terminal chips.

Access system vendor Wave7 Optics Inc., a PON pioneer in the late 1980s, claimed last week to be the first to ship an aggregation system that supports EPON and GPON simultaneously.

Some larger carriers have committed billions to the creation of green-field PON networks, with Verizon setting the tone. But second-tier carriers need an easy strategy to move from VDSL or HFC to PON. Zhone is attempting to solve that problem at the system level by offering GPON line cards that are inserted directly into its multi-access line concentrator (MALC) multiservice broadband loop carrier. The MALC chassis already supports DSL services, and fiber-to-the-home can be added with the new GPON boards.

Hitachi Telecom USA Inc. designed its AMN1220 aggregator to integrate into cable MSO headends and the results were announced just ahead of NxtComm. The Hitachi systems are being used in what is believed to be the first MSO deployment of GPON, by Falcon Broadband.

Because MSOs and telco carriers may have radically different ideas on what functions stay inside and outside the home, BroadLight director of marketing Dan Parsons said PON chip designers cannot bet on a sole residential-gateway or outdoor-pod strategy. "There are some basic functions that will be integrated, outdoors or indoors," he said. "But you have to plan on flexible PON designs."

Too many PONs?
Even if millions of homes adopt PON ONTs of some type, carrier market consolidation will likely mean that only a lucky few OEMs and semiconductor suppliers will make PON infrastructure a viable business.

One developer who has watched the first round of consolidation, as Passave was snapped up by PMC-Sierra, said he expects more fireworks as Conexant Systems Inc., Ikanos Communications and other players enter a crowded market.

"In the first place, the chip market itself is getting as crowded as Ethernet switching was in the early days," said the source, who asked not to be identified. "Ethernet switching has pretty much boiled down to just Broadcom and Marvell. As for the customers they serve, the early PON TEMs [telecom equipment manufacturers] are either loop carrier specialists or ones with internal projects they've served, like Hitachi."

He adds, "Once a Cisco or an Alcatel gets really serious here, how much room will there be for end equipment? And how many carriers could really be as serious in PON purchases as a Verizon or an AT&T?"

- Loring Wirbel
EE Times

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