The demonstration took place during the Supercomputing Conference 2008 (SC08), in Austin, Texas, in late November, but was only announced recently (see Ciena demos leadership in 100G technology).
The single-wavelength claim is significant because previous 100 Gbit/s tests combined two 50 Gbit/s wavelengths or multiplexed multiple 10 Gbit/s optical signals, says Dimple Amin, Ciena's vice-president, products and technology.
In fact Ciena’s demo was the exact opposite of what Infinera, Ixia and XO Communications showed at NXTcomm in June, where they inversely multiplexed 100 Gigabit Ethernet (GbE) onto 10 wavelengths, each running at 10 Gbit/s (see Infinera, XO to demo 100G and Ixia demos pre-standard 100G).
At SC08, Ciena electrically combined ten 10 GbE signals from switches in the Caltech exhibit area onto a single wavelength for transmission over its CN 4200 RS FlexSelect DWDM platform, then returned the separated 10 GbE signals back to Caltech's booth.
The transmission featured an actual line rate of 112 Gbit/s and a true 100 Gbit/s OTN-framed payload using enhanced forward error correction (EFEC). The EFEC was developed in-house, and the OTN framing was based on a snapshot of the OTN standard. "We had to develop some kind of framing, some kind of interpretation of how OTN is developing," Amin notes.
What's more, Ciena packed the transponder components into two line cards on its platform, indicating that it was possible to put the equipment into a commercial form factor. "It's probably the highest-density form factor that has been demonstrated today," claims Amin.
The vendor picked dual-polarization differential quadrature phase-shift keying (DP-DQPSK) as the modulation scheme — the transmission format favoured by the Optical Internetworking Forum (OIF), but without coherent detection. Ciena plans to add the coherent piece to its solution, and has a 100 Git/s coherent test bed in the laboratory, but says that the technology is still "right at the edge of technical viability".
Ciena says it probably won't commercialize the 100 Gbit/s technology in its existing form. Right now, most interest in 100 Gbit/s is for long-haul applications, where the increased sensitivity of coherent detection is a must. But if operators developed a need for 100 Gbit/s in the metro, with its shorter distances, that would put a different perspective on things.
"What we plan on commercializing in the future is the coherent capabilities," says Amin. "We call this [demo equipment] 100G 1.0, but 2.0 is already in the works."
The transceiver cards — one for each polarization — in version 1.0 were built with discrete optical components (see Optics development lags demand in race to 100G). In future, the company hopes to benefit from the OIF's efforts to create multi-source agreements for integrated photonic components for 100 Gbit/s. A few components, such as integrated modulators, have become available already, Amin notes.
Previous 100 Gbit/s demonstrations like Infinera's took place over installed fibre. In contrast, Ciena chose to bring an 80 km reel of fibre to the SC08 show in order to "keep the kit portable". However, the vendor claims that 80 km is not the limit — it has done experiments in the labs that send 100 Gbit/s signals further than 500 km.