Acreo, Ericsson in 16-QAM 100G DWDM field trial

The trial saw the transmission of 112 Gbps over a single wavelength on 824 km of installed fiber between Kista and Hudiksvall in Sweden provided by Skanova. Ericsson and Acreo developed the technology demonstrated during the trial via joint research projects.

A 100G upgrade scenario was tested by connecting the dual-polarization 112-Gbps wavelength to an existing 10G engineered DWDM system, operated by Acreo, without touching any of the optical amplifiers or dispersion compensation modules, Acreo says. The fiber link connects Kista to Hudiksvall where the fiber was looped back for a total of 12 spans.

The tests involved what Acreo described as “broadband radio technology” to modulate and demodulate electronic subcarriers. Acreo asserts the approach enables operation at low symbol rates compared to single-carrier approaches (such as the dual-polarization quadrature phase-shift keying the Optical Internetworking Forum has promoted), simplifying A/D-converters and digital signal processing (DSP). Two subcarriers were modulated onto each orthogonal polarization of a single transmitter laser and detected using a single local oscillator laser in the coherent receiver. By leveraging electronics integration the number and complexity of optical components can be reduced, thereby saving cost, Acreo adds.

For this trial, offline DSP algorithms implemented by Acreo were employed. “Our tests show the feasibility of spectrally efficient 16-QAM modulation together with coherent detection and DSP for mitigating transmission impairments under realistic conditions”, said Jonas Mårtensson, project manager at Acreo.

The funding for Acreo’s participation in research projects leading to these results was partly provided by Sweden’s innovation agency VINNOVA.