ANAHEIM, Calif. As cable operators beef up delivery of voice and data services, their networks are increasingly intertwining with optical ones to give a new look to cable's infrastructure. Capitalizing on that new look, Alcatel has developed a passive optical network (PON) scheme, which it demonstrated at the cable industry's Western Show this past week.
Alcatel put the industry's first ITU standard-compliant "fiber to the user" (FTTU) products on display, hoping they'll "take us into the cable access market," said Alcatel executive Mark Klimek. Alcatel believes all-optical PONs can make a so-called "triple play" over one network delivering voice, data and video both feasible and affordable for service operators, he said.
Alcatel does not expect incumbent cable operators to switch from heavily invested hybrid-fiber-coax (HFC) networks to PONs anytime soon. Rather, the targets are the so-called overbuilders like WINfirst, RCN Corp. and Grande Communications, which are building new networks to offer a service bundle of voice, high-speed data and cable TV to overlay existing networks. Other potential customers include small independent phone companies and second-tier cities now neglected by cable operators or phone companies for cable modem or DSL services, said Klimek, director of marketing and business development for advanced systems at Alcatel USA (Raleigh, N.C.).
Alcatel's not alone among telco and Internet equipment vendors scouting for business in cable. Some like Cisco Systems Inc. have had a cable foothold for years, while others such as Riverstone Networks Inc. are just moving in.
Better known for telco and DSL products, Alcatel was attending the Western Show for the first time. "They actually have a good bit of the market share in North America for access, with the purchase of DSC [Communications Corp. in 1998] . . . for the digital loop carriers, so it doesn't surprise me to see them go further in this area," said Jeff Gwynne, senior vice president of marketing for equipment vendor Quantum Bridge Communications Inc.
A PON uses a passive splitter to separate a single fiber-optic signal into smaller streams, creating a "fan-out" network. One advantage over copper or HFC arrangements is the speed of the fiber. More importantly, proponents say, the passive nature of the setup holds down both equipment and maintenance costs.
"There are no active electronics components on the field," said Alcatel's Klimek. "The passive optical network requires no amplifiers or fiber nodes that often demand high maintenance, [a factor that also translates into] a very low loss of data in the field," he said.
It also means low cost, which was a motivation for SBC Communications Inc. to begin PON trials in California after killing off Project Pronto, the carrier's initiative to spread DSL to residences. SBC's chief technical officer, Ross Ireland, told the IEEE Globespan Conference last week that the cost of active electronics contributed to Project Pronto's demise.
Capacity is an issue, too. While the average HFC network may give the user 1.5-Mbit/second downstream and 380-kbit/s upstream data, the FTTU over broadband passive optical network can provide an average of 20 Mbits/s of downstream data and 5 Mbits/s of upstream data, according to Alcatel.
Lining up equipment
Companies like Salira Optical Network Systems Inc. and Alloptic Inc. have been developing equipment for Ethernet-based PONs. Others like Alcatel and Quantum Bridge are concentrating on PONs for asynchronous transfer mode (ATM), the protocol favored by incumbent voice networks because of its inherent quality-of-service features that can prioritize urgent traffic such as voice calls.
Officials at Quantum Bridge claim their focus on PON access for businesses has caught the attention of cable operators. Since cable companies' fiber lines pass by offices and business parks that typically aren't wired for cable, some operators are turning to PONs to connect those businesses to their network.
In this case, the PON's splitter would create a detour, steering some of the bandwidth to businesses. Cable companies see this as a way to get data and even telephone services to businesses, Gwynne said.
Alcatel targets a scenario in which a newer cable competitor chooses to substitute an all-optical FTTU infrastructure for the traditional HFC. But because PONs use no active electronics in the field, the burden of converting optical signals to electronics and the intelligence needed to process a few other critical protocols sits with a residential network interface device, called a home optical network terminal (H-ONT).
At the Western Show, Alcatel said it has the industry's first ITU G.983-compliant H-ONT. G.983 is a newly standardized protocol for PONs to deliver voice, video and data.
Called the Alcatel 7340 H-ONT, the residential-access device is deployed on the outside of a subscriber's home. It has an interface to the broadband passive optical network fiber as well as four twisted-pair interfaces for voice. It includes a coaxial interface to provide video service and a 10/100 Base T interface for data. The H-ONT device also offers an option of home networking based on Home Phoneline Networking Alliance protocol over the twisted-pair lines used to provide voice.
The H-ONT's three major components are a triplexer that converts optical signals sent via three wavelengths into electronics signals; a broadband PON processing device, equivalent to a media-access-control layer; and a voice gateway processor to process packetized voice into analog voice. While Alcatel designed its own ASICs for the broadband PON processor, the company teamed up with unnamed component vendors to design the voice gateway processor and the triplexer.
The cost per subscriber of providing FTTU including a packet optical line terminal, video optical line terminal and voice gateway installed at a headend together with H-ONT on a residential side is about $1,300, according to Klimek. The biggest portion of that cost is the H-ONT, which is about $1,000.
Despite the high price tag, Klimek said, "Service operators need to install H-ONT only when they get a customer. They don't have to make that investment up front."
Alcatel is putting its H-ONT through three laboratory trials, and expects to launch commercial H-ONT devices in the second quarter of 2002.
Meanwhile, an industry consortium called Full Service Access Network composed of large global service operators such as NTT Communications Corp., France Telecom and SBC has been developing next-generation access technology for a broadband passive optical network. While initial efforts now reside in the ITU G.983 standard, the consortium is not sitting still, according to Alcatel. The group meets in the coming week to discuss an enhanced version of the broadband passive optical network by improving the bandwidth to a gigabit rate, while maintaining backward compatibility, Klimek said.