# Polarization-ring-switching for nonlinearity-tolerant geometrically-shaped four-dimensional formats maximizing generalized mutual information

Bin Chen, Chigo Okonkwo, Hartmut Hafermann, Alex Alvarado

Research output: Contribution to journalArticleAcademic

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### Abstract

In this paper, a new four-dimensional 64-ary polarization ring switching (4D-64PRS) modulation format with a spectral efficiency of $6$~bit/4D-sym is introduced. The format is designed by maximizing the generalized mutual information (GMI) and by imposing a constant-modulus on the 4D structure. The proposed format yields an improved performance with respect to state-of-the-art geometrically shaped modulation formats for bit-interleaved coded modulation systems at the same spectral efficiency. Unlike previously published results, the coordinates of the constellation points and the binary labeling of the constellation are \emph{jointly} optimized. When compared against polarization-multiplexed 8-ary quadrature-amplitude modulation (PM-8QAM), gains of up to $0.7$~dB in signal-to-noise ratio are observed in the additive white Gaussian noise (AWGN) channel. For a long-haul nonlinear optical fiber system of $8,000$~km, gains of up to $0.27$~bit/4D-sym ($~5.5$\% data capacity increase) are observed. These gains translate into a reach increase of approximately $16\%$ ($1,100$~km). The proposed modulation format is also shown to be more tolerant to nonlinearities than PM-8QAM. Results with LDPC codes are also presented, which confirm the gains predicted by the GMI.
Original language English 1901.06878v1 11 arXiv Published - 21 Jan 2019

## ICONIC: Increasing the Capacity of Optical Nonlinear Interfering Channels

Alvarado, A., Alvarado, A., Oliari, V., Keijzers, A., Keijzers, A., Gerrits, E., Willems, F. M. J., Sanders, R., Alvarado, A., Barreiro, A., Wu, K. & de Jonge, M.

1/08/1731/07/22

Project: Research direct

## NLCAP: Multi-dimensional coded modulation for Maximizing NonLinear CAPacity in the Optical Channel

Okonkwo, C. M., Alvarado, A., Croes, S., Willems, F. M. J., Sanders, R., Alvarado, A., Barreiro, A. & Chen, B.

1/06/1731/03/19

Project: Research direct

## High Capacity Optical Transmission Lab

Chigo Okonkwo (Manager), Sjoerd van der Heide (Operator), Menno van den Hout (Operator), Sebastiaan Goossens (Operator) & John J.A. van Weerdenburg (Operator)

Department of Electrical Engineering

Facility/equipment: Research lab