47 research outputs found
Experimental Comparison of Probabilistic Shaping Methods for Unrepeated Fiber Transmission
\u3cp\u3eThis 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.\u3c/p\u3
Experimental Verification of Rate Flexibility and Probabilistic Shaping by 4D Signaling
The rate flexibility and probabilistic shaping gain of -dimensional
signaling is experimentally tested for short-reach, unrepeated transmission. A
rate granularity of 0.5 bits/QAM symbol is achieved with a distribution matcher
based on a simple look-up table.Comment: Presented at OFC'18, San Diego, CA, US
A Simple Nonlinearity-Tailored Probabilistic Shaping Distribution for Square QAM
A new probabilistic shaping distribution that outperforms Maxwell-Boltzmann
is studied for the nonlinear fiber channel. Additional gains of 0.1 bit/symbol
MI or 0.2 dB SNR for both DP-256QAM and DP-1024QAM are reported after 200 km
nonlinear fiber transmission
Experimental Demonstration of Geometrically-Shaped Constellations Tailored to the Nonlinear Fibre Channel
A geometrically-shaped 256-QAM constellation, tailored to the nonlinear
optical fibre channel, is experimentally demonstrated. The proposed
constellation outperforms both uniform and AWGN-tailored 256-QAM, as it is
designed to optimise the trade-off between shaping gain, nonlinearity and
transceiver impairments
Performance of Probabilistic Shaping Coherent Channels in Hybrid Systems
We present the performance comparison of probabilistically shaped 64QAM with uniform 16/32QAM in hybrid systems. The results show that the PS signal can increase the maximum reach and is more tolerant to strong nonlinear interference. Nevertheless, when the nonlinear interference is weak, uniform formats can provide higher performance
First Experimental Demonstration of Probabilistic Enumerative Sphere Shaping in Optical Fiber Communications
We transmit probabilistic enumerative sphere shaped dual-polarization 64-QAM
at 350Gbit/s/channel over 1610km SSMF using a short blocklength of 200. A reach
increase of 15% over constant composition distribution matching with identical
blocklength is demonstrated
Exponentially-Weighted Energy Dispersion Index for the Nonlinear Interference Analysis of Finite-Blocklength Shaping
A metric called exponentially-weighted energy dispersion index (EEDI) is
proposed to explain the blocklength-dependent effective signal-to-noise ratio
(SNR) in probabilistically shaped fiber-optic systems. EEDI is better than
energy dispersion index (EDI) at capturing the dependency of the effective SNR
on the blocklength for long-distance transmission