49 research outputs found
Eight-dimensional Polarization-ring-switching Modulation Formats
We propose two 8-dimensional (8D) modulation formats (8D-2048PRS-T1 and
8D-2048PRS-T2) with a spectral efficiency of 5.5 bit/4D-sym, where the 8
dimensions are obtained from two time slots and two polarizations. Both formats
provide a higher tolerance to nonlinearity by selecting symbols with
nonidentical states of polarization (SOPs) in two time slots. The performance
of these novel 8D modulation formats is assessed in terms of the effective
signal-to-noise ratio (SNR) and normalized generalized mutual information.
8D-2048PRS-T1 is more suitable for high SNRs, while 8D-2048PRS-T2 is shown to
be more tolerant to nonlinearities. A sensitivity improvement of at least 0.25
dB is demonstrated by maximizing normalized generalized mutual information
(NGMI). For a long-haul nonlinear optical fiber transmission system, the
benefit of mitigating the nonlinearity is demonstrated and a reach increase of
6.7% (560 km) over time-domain hybrid four-dimensional two-amplitude
eight-phase shift keying (TDH-4D-2A8PSK) is observed
Increasing Achievable Information Rates via Geometric Shaping
Achievable information rates are used as a metric to design novel modulation
formats via geometric shaping. The proposed geometrically shaped 256-ary
constellation achieves SNR gains of up to 1.18 dB.Comment: Additional references have been adde
From Hubbard bands to spin-polaron excitations in the doped Mott material NaCoO
We investigate the excitation spectrum of strongly correlated sodium
cobaltate within a realistic many-body description beyond dynamical mean-field
theory (DMFT). At lower doping around =0.3, rather close to Mott-critical
half-filling, the single-particle spectral function of NaCoO displays
an upper Hubbard band which is captured within DMFT. Momentum-dependent
self-energy effects beyond DMFT become dominant at higher doping. Around a
doping level of , the incoherent excitations give way to
finite-energy spin-polaron excitations in close agreement with optics
experiments. These excitations are a direct consequence of the formation of
bound states between quasiparticles and paramagnons in the proximity to
in-plane ferromagnetic ordering.Comment: 5 pages, 3 figures; supplementary materia