Another transmission record on the data highway

27 Oct 2006

No speed limit yet, say researchers at Berlin's HHI, as they transmit data at 2.56 Tbit/s through a single fiber.

Researchers at the Fraunhofer Institute for Telecommunications, Heinrich-Hertz-Institut (HHI) in Berlin in co-operation with colleagues at Japan's Fujitsu Laboratories have succeeded in transferring a data rate of 2.56 Tbit/s over a glass fiber link of 160 km> They claim this breaks the previous transmission record of 1.2 Tbit/s that had stood for five years.

This data rate means the transmission of 2,560 billion bits or the contents of approximately 60 DVDs in one second. The results were presented to the public for the first time by the HHI scientists at the European Conference on Optical Communications 2005 in Glasgow.

"In this particular experiment, we packed 32 channels loaded with 40 Gbit/s data packets modulated by DPQSK together with OTDM technique," explained Wolf von Reden, of Fraunhofer-HHI. "The medium is a dispersion-managed fiber, fabricated by OFS, Denmark. From knowing what we put into each channel, we had only to measure the bit-error rate at each channel at the receiver."

"As an institute of the Fraunhofer Gesellschaft group, we do such research to find the limiting capacity of fibers. This is of interest because the data rate in the backbone of the [communications] optical networks will increase. This will mean moving beyond the so-called DWDM-region and entering a CWDM region with heterogeneous payloads due to QoS demands in the different channels."

The researchers overcame the problem of polarization-mode dispersion in the fiber by using a special dispersion-compensated fiber from OFS Denmark. Also essential for the transmission was an amplifier with a gain that is smooth across the used spectrum.

Apart from the speed record the Berlin scientists are now also holding two distance records: data transmission at 1.28 Tbit/s over a glass fiber link with a length of 240 km, and data transmission of 160 Gbit/s over a glass fiber link with a length of 4000 km.