General

Fun with Big Pipes

When Belgium's ILEC needed a multi-gigabit fiber optic upgrade to prepare it to deliver regular and HDTV over Ethernet—especially for sports—it called on equipment provider Ekinops and integrator SEE Telecom. This is not IPTV, but it may be the future.

by Gerry Blackwell [November 7, 2008]

It's not sexy. It's not top of mind. Most of us take it entirely for granted. But the transport layer—the optical fiber that carries data and voice thousands of miles, and the gear that interconnects fiber to routers and switches—underlies and informs everything that happens on the Net, and on most other kinds of networks.

"In the case of the internet, you have transport everywhere," says Rob Adams, U.S.-based vice president of global marketing and product line management for Ekinops, a French manufacturer of optical transport equipment. "Any connection that you make to any website anywhere on the internet or whenever you send e-mails, it's going to traverse transport somewhere."

Transport technology has evolved in recent years, with mind-boggling growth in capacity and capability, but interfacing to transport networks can get complicated. Nowhere is this better illustrated than a recent project Ekinops worked on for Belgacom, the former PTT in Belgium, which today offers phone, Internet, television and other communications services.

Belgacom also owns the rights to distribute TV broadcasts of premier league soccer games in Belgium. Earlier this year, with confirmation that its soccer contract had been renewed by the league, it faced a major challenge. Belgacom was committed to making the switch to carrying games in high definition (HD), and with the summertime Europe 2008 games looming, it had to make the transition fast.

Not a simple task
There were several challenges, not the least of them the tight time frame. Belgacom had to get signals from HD video cameras at each stadium to its switching center in Brussels, and from there to broadcasters. It already had a nation-wide backbone network in place but had to build new fiber links from the stadiums to the backbone and from the backbone to broadcaster sites. It was the interfaces between those links and the backbone that created many of the challenges.

One requirement was that signals go end-to-end in uncompressed HD video to avoid any loss of quality. Each HD stream requires about 1.5 gigabits per second (Gbps) of bandwidth. And Belgacom had to carry four from each stadium—one per camera. It also needed to carry one 10 Mbps Ethernet stream, one 1 Gbps Ethernet stream—for data transfer and control—and an IP telephony channel to link the stadiums to engineers at the Brussels switching center.

But this head-spinning bandwidth requirement was really the least of Belgacom's challenges, given the huge advances in wavelength division multiplexing (WDM), the technology that allows optical fiber networks to send multiple streams of data over the same piece of glass fiber at different frequencies.

Digital data is sent over fiber as light pulses from a laser—at the simplest level, one is on, zero is off. Originally, you could only send one stream of pulses over a single strand.

"The rate at which you transmitted [data] was dependent on how fast you could flash that laser," Adams explains. "But at some point, somebody said, 'instead of flashing the laser faster, let's just put multiple lasers on the same pipe.' Now, where I was shining one laser that was flashing really fast, I've got 180 of them on the same pipe. So I get 180 times the bandwidth."

WDM keeps improving, yielding more and more bandwidth. 10 Gbps transport—used in this project—is now fairly common. Technology is coming soon that will deliver 40 Gbps and 100 Gbps is on the horizon, says Jan Van Hoecke, business development manager at SEE Telecom, the Belgian systems integrator on the Belgacom project.

This project wasn't just about mustering more bandwidth to accommodate HD, but that was certainly part of it. Before going HD, Belgacom only had to carry standard definition streams, each requiring about a fifth the bandwidth needed for HD. For that, it used many protocols and transmission media, mainly ATM (Asynchronous Transfer Mode) and SONET (Synchronous optical networking), the traditional technologies of the transport world. "Whatever was available was used," says Van Hoecke.

But Belgacom was also committed to following the trend of recent years, which has seen traditional transport protocols such as SONET and ATM replaced by Ethernet. So another requirement of the project was that the HD video, data and IP voice all had to be woven together—multiplexed—and carried as a single 10 gigabit Ethernet stream.

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