Communications network operators have only recently begun to roll out optical transmission equipment supporting speeds of 100 Gbps. But we’ve already seen the first commercial deployment of 400 Gbps equipment. France Telecom - Orange (News - Alert) recently upgraded a connection between Paris and Lyon to 400 Gbps using equipment from Alcatel-Lucent.
In an interview, Olivier Gombert, director of Orange’s Transmission Factory, said the company was able to upgrade previously installed Alcatel-Lucent (News - Alert) equipment by upgrading the device’s muxponder. As Gombert explained, the 400 Gbps connection uses the equivalent of two wavelengths to support the higher data rate.
The Paris-to-Lyon route was a good candidate for the upgrade because it is one of the busiest routes in France, connecting the nation’s two largest markets. In addition, the two markets are only about 560 kilometers apart, eliminating the need to add regeneration capability, said Gombert. With 100 Gbps service, optical transmissions on the France Telecom (News - Alert) – Orange network can travel as far as 2,000 kilometers without regeneration, but with 400 Gbps that distance is reduced, he said.
As Gombert explained, optical transmission is evolving from wavelength definitions based on a fixed grid to definitions based on a flexible grid. “The job of telecom operators will be to play with the flexible grid to [balance] bit rate and distance and customer demand,” he said. “With the arrival of the flexible grid, we will have a choice of increasing bandwidth and reducing the length of the span or increasing the length of the span” and reducing the bandwidth.
Kevin Drury, senior director of optical product and solutions marketing for Alcatel-Lucent, said the company’s 400 Gbps solution reduces power requirements by about 50 percent in comparison with using four 100 Gbps connections. And while four 100 Gbps connections would require eight slots in Alcatel-Lucent’s optical transport system, a single 400 Gbps connection requires only three slots. Those considerations should make the 400 Gbps option appealing to network operators that need increased capacity on busy routes that are not separated by great distances, Drury said.
As 400 Gbps links are rolled out, Drury believes network operators will put a greater push behind 100 Gbps services than they have to date. France Telecom – Orange, for example, has sold one 100 Gbps connection on its 400 Gbps Paris-to-Lyon link to research and education network Renater, which means that France Telecom – Orange could easily support three additional customers each requiring 100 Gbps.
Toward a terabit
Network operators and equipment manufacturers already have begun to explore the next anticipated incremental improvement in optical transmission, with the goal of supporting speeds of at least one terabit per second (1 Tbps).
Perhaps not surprisingly, the advent of the flexible grid has given rise to a variety of approaches to boost bandwidth. Alcatel Lucent’s (News - Alert) research organization Bell Labs has tested several options for achieving 1 Tbps speeds including using eight subcarriers over spans up to 5600 km and using two subcarriers over 3200-km spans.
A subcarrier is essentially equivalent to a wavelength, but the amount of optical spectrum required per subcarrier may vary from one proposed solution to another when a flexible grid is used.
Drury noted that Alcatel-Lucent research shows that 80 percent of the fiber routes around the world are 1,600 km or less. He said the company hopes to be ready to bring a terabit product to the market near the end of this decade.
Edited by Brooke Neuman