13 research outputs found
Polarization-ring-switching for nonlinearity-tolerant geometrically-shaped four-dimensional formats maximizing generalized mutual information
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 jointly optimized. When compared with
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.Comment: 12 pages, 12 figure
High-Cardinality Geometrical Constellation Shaping for the Nonlinear Fibre Channel
This paper presents design methods for highly efficient optimisation of
geometrically shaped constellations to maximise data throughput in optical
communications. It describes methods to analytically calculate the
information-theoretical loss and the gradient of this loss as a function of the
input constellation shape. The gradients of the \ac{MI} and \ac{GMI} are
critical to the optimisation of geometrically-shaped constellations. It
presents the analytical derivative of the achievable information rate metrics
with respect to the input constellation. The proposed method allows for
improved design of higher cardinality and higher-dimensional constellations for
optimising both linear and nonlinear fibre transmission throughput.
Near-capacity achieving constellations with up to 8192 points for both 2 and 4
dimensions, with generalised mutual information (GMI) within 0.06 bit/2Dsymbol
of additive white Gaussian noise channel (AWGN) capacity, are presented.
Additionally, a design algorithm reducing the design computation time from days
to minutes is introduced, allowing the presentation of optimised constellations
for both linear AWGN and nonlinear fibre channels for a wide range of
signal-to-noise ratios
Analysis and Experimental Demonstration of Orthant-Symmetric Four-dimensional 7 bit/4D-sym Modulation for Optical Fiber Communication
We propose a new four-dimensional orthant-symmetric 128-Ary modulation format (4D-OS128) with a spectral efficiency of 7 bit/4D-sym. The proposed format fills the gap between polarization-multiplexed 8-and 16-Ary quadrature-Amplitude modulation (PM-8QAM and PM-16QAM). Numerical simulations show that 4D-OS128 outperforms two well-studied 4D geometrically-shaped modulation formats: 128SP-16QAM and 7b4D-2A8PSK by up to 0.65 dB for bit-interleaved coded modulation at the same spectral efficiency. These gains are experimentally demonstrated in a 11×233 Gbit/s wavelength division multiplexing (WDM) transmission system operating at 5.95 bit/4D-sym over 6000 and 9000 km for both EDFA-only and hybrid amplification scenarios, respectively. A reach increase of 15% is achieved with respect to 128-Ary set-partitioning 16QAM. Furthermore, the proposed 4D-OS128 is also compared to lattice-based constellation, 16QAM and probabilistically-shaped 16QAM with finite blocklength via simulation
Analysis and experimental demonstration of orthant-symmetric four-dimensional 7 bit/4D-sym modulation for optical fiber communication
We propose a new four-dimensional orthant-symmetric 128-ary modulation format (4D-OS128) with a spectral efficiency of 7 bit/4D-sym. The proposed format fills the gap between polarization-multiplexed 8-ary and 16-ary quadrature-amplitude modulation (PM-8QAM and PM-16QAM). Numerical simulations show that 4D-OS128 outperforms state-of-the-art geometrically-shaped modulation formats by up to 0.65 dB for bit-interleaved coded modulation at the same spectral efficiency. These gains are experimentally demonstrated in a 11233 Gbit/s wavelength division multiplexing (WDM) transmission system operating at 5.95 bit/4D-sym over 6000 km and 9000 km for both EDFA-only and hybrid amplification scenarios, respectively. A reach increase of 15% is achieved with respect to 128-ary set-partitioning 16QAM