Olaf Schulz’s research while affiliated with Kiel University and other places

We present add-drop multiplexing for full spectrum modulated WDM nonlinear frequency division multiplexed transmission systems, in which spectral overlap between channels is used to eliminate nonlinear inter-channel crosstalk.

We present an add-drop multiplexer for WDM nonlinear frequency division multiplexed transmission systems, capable of replacing channels in a modulated spectrum that uses spectral overlap to stitch the nonlinear spectrum to avoid guard bands.

We experimentally investigate the problem of monitoring the Kerr-nonlinearity coefficient γ from transmitted and received data for a single-mode fiber link of 1600km length. We compare the accuracy and speed of three different approaches. First, a standard split-step Fourier method is used to predict the output at various γ values, which are then compared to the measured output. Second, a recently proposed nonlinear Fourier transform (NFT)-based method, which matches solitonic eigenvalues in the transmitted and received signals for various γ values. Third, a novel fast version of the NFT-based method, which only matches the highest few eigenvalues. Although the NFT-basedmethodsdonotscalewithlinklength,wedemonstrate that the SSFM-based method is significantly faster than the basic NFT-based method for the considered link of 1600km, and outperforms even the faster version. However, for a simulated link of 8000km, the fast NFT-based method is shown to be faster than the SSMF-based method, although at the cost of a small loss in accuracy.

We present a highly scalable PIC-based nonlinear frequency division multiplexed transmission system in which b-modulated channels are wavelength division multiplexed with spectral overlap so as to obtain a seamless spectrum without frequency guard bands.

We present a full spectrum modulated nonlinear frequency division multiplexed transmission system in which b-modulated channels are wavelength division multiplexed with spectral overlap to compensate for nonlinear inter-channel crosstalk.

We demonstrate a silicon photonic transmitter for soliton-based communications enabling the interleaving of QPSK and APSK modulated soliton pulses overlapping in both the time and frequency domains. The nonlinear Fourier transform is used to both determine adequate soliton launch conditions and facilitate nonlinear equalization at the receiver. A spectral efficiency of 0.5 b/s/Hz per polarization is reached over a 5400 km transmission distance and constitutes, to the best of our knowledge, a record for soliton transmission over such long distances. Linear and nonlinear minimum mean square error and artificial neural network-based equalizers are also experimentally benchmarked, with artificial neural networks resulting in particularly effective equalization in this system.

Recently, a nonlinear Fourier transform-based Kerr-nonlinearity identification algorithm was demonstrated for a 1000 km NZDSF link with accuracy of 75%. Here, we demonstrate an accuracy of 99% over 1600 km SSMF. Reasons for improved accuracy are discussed.