Another transmission record on the data highway


Sat 28-10-2006
No speed limit yet, say researchers at Berlin's HHI, as they transmit data at 2.56 Tbit/s through single fibre

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 fibre link of 160 km> They claim this breaks the previous transmission record of 1.2 Tbit/s which had been good 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 Gbps data packets modulated by DPQSK together with OTDM technique," explained Wolf von Reden, of Fraunhofer-HHI. "The medium is a dispersion managed fibre, fabricated by OFS, Denmark. We were able to make the measurement, 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 fibres. 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."

Typical problems overcome include: polarization mode dispersion in the fibre, which was achieved by using a special dispersion compensated fibre from OFS Denmark. Also essential for the transmission is an amplifier with a gain, which 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 Terabit per second over a glass fibre link with a length of 240 km and data transmission of 160Gbit/s over a glass fibre link with a length of 4000 km.