Thursday, March 8, 2012

Fujitsu Develops DSP Algorithm for 100G Long-haul Optical Distortion

Researchers at Fujitsu have developed a digital signal processing algorithm to compensate for waveform distortion in long-haul transmission systems operating over several hundred kilometers. The method is aimed at 100 Gbps transmissions, which tend to suffer from waveform distortion caused by nonlinear optical effects over distance.

Fujitsu said a key advantage of its new technology is that it does not require signal regenerators. The nonlinear compensation technology can restore the signal received with distortion to a clean waveform.

The company claims roughly a twenty-fold improvement in the compensation ability per circuit size compared to typical existing technology. The design also cuts the energy consumption of compensation circuits by two-thirds.

The receiving-side digital signal processing LSI used to measure and verify the effectiveness of the developed technology was developed under a project sponsored by Japan's Ministry of Internal Affairs and Communications.

The new technology takes a new approach in that it transmits additional inverse distortion in order to "clean up" distorted waves. Unlike receiver-end compensation circuits, waveforms from compensation circuits located on the transmission end do not contain noise or distortion, thereby enabling simpler computation. Fujitsu has narrowed its focus on DP-QPSK modulation.

Fujitsu reported that in a transmission test at 112 Gbps, the new technology was shown to achieve, using a one-stage circuit, even higher signal quality than that obtained using a 20-stage compensation circuit in conventional technology.

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