8,730 research outputs found
Demodulation and Detection Schemes for a Memoryless Optical WDM Channel
It is well known that matched filtering and sampling (MFS) demodulation
together with minimum Euclidean distance (MD) detection constitute the optimal
receiver for the additive white Gaussian noise channel. However, for a general
nonlinear transmission medium, MFS does not provide sufficient statistics, and
therefore is suboptimal. Nonetheless, this receiver is widely used in optical
systems, where the Kerr nonlinearity is the dominant impairment at high powers.
In this paper, we consider a suite of receivers for a two-user channel subject
to a type of nonlinear interference that occurs in
wavelength-division-multiplexed channels. The asymptotes of the symbol error
rate (SER) of the considered receivers at high powers are derived or bounded
analytically. Moreover, Monte-Carlo simulations are conducted to evaluate the
SER for all the receivers. Our results show that receivers that are based on
MFS cannot achieve arbitrary low SERs, whereas the SER goes to zero as the
power grows for the optimal receiver. Furthermore, we devise a heuristic
demodulator, which together with the MD detector yields a receiver that is
simpler than the optimal one and can achieve arbitrary low SERs. The SER
performance of the proposed receivers is also evaluated for some single-span
fiber-optical channels via split-step Fourier simulations
Information Transmission using the Nonlinear Fourier Transform, Part III: Spectrum Modulation
Motivated by the looming "capacity crunch" in fiber-optic networks,
information transmission over such systems is revisited. Among numerous
distortions, inter-channel interference in multiuser wavelength-division
multiplexing (WDM) is identified as the seemingly intractable factor limiting
the achievable rate at high launch power. However, this distortion and similar
ones arising from nonlinearity are primarily due to the use of methods suited
for linear systems, namely WDM and linear pulse-train transmission, for the
nonlinear optical channel. Exploiting the integrability of the nonlinear
Schr\"odinger (NLS) equation, a nonlinear frequency-division multiplexing
(NFDM) scheme is presented, which directly modulates non-interacting signal
degrees-of-freedom under NLS propagation. The main distinction between this and
previous methods is that NFDM is able to cope with the nonlinearity, and thus,
as the the signal power or transmission distance is increased, the new method
does not suffer from the deterministic cross-talk between signal components
which has degraded the performance of previous approaches. In this paper,
emphasis is placed on modulation of the discrete component of the nonlinear
Fourier transform of the signal and some simple examples of achievable spectral
efficiencies are provided.Comment: Updated version of IEEE Transactions on Information Theory, vol. 60,
no. 7, pp. 4346--4369, July, 201
Information Transmission using the Nonlinear Fourier Transform, Part I: Mathematical Tools
The nonlinear Fourier transform (NFT), a powerful tool in soliton theory and
exactly solvable models, is a method for solving integrable partial
differential equations governing wave propagation in certain nonlinear media.
The NFT decorrelates signal degrees-of-freedom in such models, in much the same
way that the Fourier transform does for linear systems. In this three-part
series of papers, this observation is exploited for data transmission over
integrable channels such as optical fibers, where pulse propagation is governed
by the nonlinear Schr\"odinger equation. In this transmission scheme, which can
be viewed as a nonlinear analogue of orthogonal frequency-division multiplexing
commonly used in linear channels, information is encoded in the nonlinear
frequencies and their spectral amplitudes. Unlike most other fiber-optic
transmission schemes, this technique deals with both dispersion and
nonlinearity directly and unconditionally without the need for dispersion or
nonlinearity compensation methods. This first paper explains the mathematical
tools that underlie the method.Comment: This version contains minor updates of IEEE Transactions on
Information Theory, vol. 60, no. 7, pp. 4312--4328, July 201
Nonlinear Bloch-wave interaction and Bragg scattering in optically-induced lattices
We study, both theoretically and experimentally, the Bragg scattering of
light in optically-induced photonic lattices and reveal the key physical
mechanisms which govern nonlinear self-action of narrow beams under the
combined effects of Bragg scattering and wave diffraction, allowing for
selecting bands with different effective dispersion.Comment: 4 pages, 6 figure
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