Showing papers by "Norbert Hanik published in 2017"

Experimental Comparison of Probabilistic Shaping Methods for Unrepeated Fiber Transmission

Abstract: This paper studies the impact of probabilistic shaping on effective signal-to-noise ratios (SNRs) and achievable information rates (AIRs) in a back-to-back configuration and in unrepeated nonlinear fiber transmissions. For the back-to-back setup, various shaped quadrature amplitude modulation (QAM) distributions are found to have the same implementation penalty as uniform input. By demonstrating in transmission experiments that shaped QAM input leads to lower effective SNR than uniform input at a fixed average launch power, we experimentally confirm that shaping enhances the fiber nonlinearities. However, shaping is ultimately found to increase the AIR, which is the most relevant figure of merit, as it is directly related to spectral efficiency. In a detailed study of these shaping gains for the nonlinear fiber channel, four strategies for optimizing QAM input distributions are evaluated and experimentally compared in wavelength division multiplexing (WDM) systems. The first shaping scheme generates a Maxwell–Boltzmann (MB) distribution based on a linear additive white Gaussian noise channel. The second strategy uses the Blahut–Arimoto algorithm to optimize an unconstrained QAM distribution for a split-step Fourier method based channel model. In the third and fourth approach, MB-shaped QAM and unconstrained QAM are optimized via the enhanced Gaussian noise (EGN) model. Although the absolute shaping gains are found to be relatively small, the relative improvements by EGN-optimized unconstrained distributions over linear AWGN optimized MB distributions are up to 59%. This general behavior is observed in 9-channel and fully loaded WDM experiments.

Experimental Comparison of Probabilistic Shaping Methods for Unrepeated Fiber Transmission

Abstract: This paper studies the impact of probabilistic shaping on effective signal-to-noise ratios (SNRs) and achievable information rates (AIRs) in a back-to-back configuration and in unrepeated nonlinear fiber transmissions. For back-to-back, various shaped quadrature amplitude modulation (QAM) distributions are found to have the same implementation penalty as uniform input. By demonstrating in transmission experiments that shaped QAM input leads to lower effective SNR than uniform input at a fixed average launch power, we experimentally confirm that shaping enhances the fiber nonlinearities. However, shaping is ultimately found to increase the AIR, which is the most relevant figure of merit as it is directly related to spectral efficiency. In a detailed study of these shaping gains for the nonlinear fiber channel, four strategies for optimizing QAM input distributions are evaluated and experimentally compared in wavelength division multiplexing (WDM) systems. The first shaping scheme generates a Maxwell-Boltzmann (MB) distribution based on a linear additive white Gaussian noise channel. The second strategy uses the Blahut-Arimoto algorithm to optimize an unconstrained QAM distribution for a split-step Fourier method based channel model. In the third and fourth approach, MB-shaped QAM and unconstrained QAM are optimized via the enhanced Gaussian noise (EGN) model. Although the absolute shaping gains are found to be relatively small, the relative improvements by EGN-optimized unconstrained distributions over linear AWGN optimized MB distributions are up to 59%. This general behavior is observed in 9-channel and fully loaded WDM experiments.

Single-Carrier 400G 64QAM and 128QAM DWDM Field Trial Transmission Over Metro Legacy Links

Abstract: We report on the results of a field trial carried out on a Telecom Italia metro link, targeting short data center interconnect applications. The test-bed presented realistic transmission conditions, such as an average ~0.3-dB/km attenuation and usage of legacy erbium-doped fiber amplifier (EDFA) only. We transmitted a net bit rate of 400 Gb/s on a single carrier with 64 quadrature amplitude modulation (QAM) and 128QAM over 156 km. Error-free transmission over 80 km for single carrier dense wavelength-division multiplexing (DWDM) $30\times 400\text{G}$ 64QAM and $30\times 400\text{G}$ 128QAM (one half of the $C$ -band) is reported. The net spectral efficiency, for both schemes, is 7.11 b/s/Hz.

A memory polynomial based digital pre-distorter for high power transmitter components

Abstract: An adaptive digital pre-distortion method based on memory polynomials to compensate for non-linearities in high power optical transmitters is presented. Gains up to 2 dB in ROSNR are achieved beyond linear pre-distortion.

On the impact of probabilistic shaping on SNR and information rates in multi-span WDM systems

Abstract: Numerical simulations and the EGN model show that probabilistic shaping decreases SNR due to modulation-dependent nonlinear effects. This SNR loss, however, is less important than the rate increase from shaping, resulting in an overall gain.

A memory polynomial based adaptive digital pre-distorter for optical communication transmitters

Abstract: We present a robust adaptive digital pre-distortion technique to mitigate the linear and non-linear degradation of optical communication transmitter components. The proposed method is based on the principles of memory polynomial based pre-distortion and indirect learning architecture. Effectiveness of the presented algorithm is assessed across various higher order modulation formats and higher baud rates. Significant gains are reported in back-to-back measurements and various lab and field trial experiments.