Linear and Nonlinear Frequency-Division Multiplexing

Two signal multiplexing schemes for optical fiber communication are considered: Wavelength-division multiplexing (WDM) and nonlinear frequency-division multiplexing (NFDM), based on the nonlinear Fourier transform. Achievable information rates (AIRs) of NFDM and WDM are compared in a network scenario with an ideal lossless model of the optical fiber in the defocusing regime. It is shown that the NFDM AIR is greater than the WDM AIR subject to a bandwidth and average power constraint, in a representative system with one symbol per user. The improvement results from nonlinear signal multiplexing

Inter-Channel Interference in Non-Linear Frequency-Division Multiplexed Networks on Fibre Links with Lumped Amplification

There has been some interest in the Non-linear Frequency-Division Multiplexing (NFDM) in optical fibre communication systems, because it promises interference-free or weak-interference between channels in an optical routed network. NFDM scheme uses Non-linear Fourier Transform (NFT) to bring a time-domain signal into the non-linear frequency domain (NFD), where the spectra evolve in a linear manner during signal propagation in the fibre channel. The successful application of NFT relies heavily on the "channel's integrability" that is only fulfilled by an ideal distribution-Raman amplification. However, most of the optical fibre links are amplified by Erbium-doped fibre amplifiers (EDFAs). The impact of the non-integrability in NFDM networks is unclear. In such a network, one key device is the Non-linear Add-drop Multiplexer (NADM) that adds or drops channels in the NFD. Simulating such device that processes many channels simultaneously is still difficult due to a high complexity and inaccuracy of the current INFT-NFT algorithm. To get around this difficulty, we adopt a different approach to estimate the inter-channel interference (ICI) in NFDM networks

Spectral Broadening of Gaussian Process in Optical Fibre and Implication on the Spectral Efficiency

We characterise the spectral evolution of Gaussian process in optical fibre using the Kolmogorov-Zakharov model. At high power regime, the spectrum at receiver is calculated by iteratively solving KZ-model at shorter distance. It questions the possibility of monotonically increasing spectral efficiency

Impact of Perturbations on Nonlinear Frequency-Division Multiplexing

Nonlinear frequency-division multiplexing (NFDM) is a communication scheme in which users' signals are multiplexed in the nonlinear Fourier domain. The contributions of this paper are twofold. First, the achievable information rates (AIRs) of NFDM based on an integrable model of the optical fiber are summarized. For this ideal model, it is shown that the AIR of the NFDM is greater than the AIR of the wavelength-division multiplexing (WDM) for a given bandwidth and signal power, in a representative system with five users and one symbol per user. The improvement results from nonlinear signal multiplexing. Second, the impact of some of the main perturbations on NFDM are investigated, including the fiber loss, polarization effects, and the third-order dispersion. For a realistic nonideal model, it is shown that the WDM AIR with joint dual-polarization back-propagation and third-order dispersion compensation is approximately equal to the NFDM AIR with two independent single-polarization demodulations and without third-order dispersion compensation. Using a joint dual-polarization receiver and perturbations compensation is expected to increase the NFDM AIR

400 Gbps Dual-Polarisation Non-Linear Frequency-Division Multiplexed Transmission with B-Modulation

We demonstrate, for the first time, a b-modulated dual-polarisation NFDM transmission in simulation, achieving a record net data rate of 400 Gbps (SE of 7.2 bit/s/Hz) over 960 km. The proposed scheme shows 1 dB Q-factor improvement over q c -modulation scheme

400 Gbps Dual-polarisation Non-linear Frequency-division Multiplexed Transmission with b-Modulation

We demonstrate, for the first time, a b-modulated dual-polarisation NFDM transmission in simulation, achieving a record net data rate of 400 Gbps (SE of 7.2 bit/s/Hz) over 960 km. The proposed scheme shows 1 dB Q-factor improvement over qc-modulation scheme

Dual-Polarization Non-Linear Frequency-Division Multiplexed Transmission With b-Modulation

There has been much interest in the non-linear frequency-division multiplexing (NFDM) transmission scheme in the optical fiber communication system. Up to date, most of the demonstrated NFDM schemes have employed only single polarization for data transmission. Employing both polarizations can potentially double the data rate of NFDM systems. We investigate in simulation a dual-polarization NFDM transmission with data modulation on the b-coefficient. First, a transformation that facilitates the dual-polarization b-modulation was built upon an existing transformation in [M. Yousefi and X. Yangzhang, “Linear and nonlinear frequency-division multiplexing,” in Proc. Eur. Conf. Opt. Commun., Dusseldorf, Germany, Sep. 2016, pp. 342344]. Second, the q c -and b-modulation for dual polarization were compared in terms of Q-factor, spectral efficiency (SE), and correlation of sub-carriers. The correlation is quantified via information theoretic metrics, joint and individual entropy. The polarization-multiplexed b-modulation system shows 1-dB Q-factor improvement over q c -modulation system due to a weaker correlation of sub-carriers and less effective noise. Finally, the b-modulation system was optimized for high data rate, achieving a record net data rate of 400 Gb/s (SE of 7.2 b/s/Hz) over 12 × 80 km of standard single-mode fiber with erbium-doped fiber amplifiers. Based on the aforementioned simulation results, we further point out the drawbacks of our current system and quantify the error introduced by the transceiver algorithms and non-integrability of the channel

Experimental Demonstration of Dual-Polarization NFDM Transmission With b-Modulation

Dual-polarization nonlinear frequency-division multiplexing (DP-NFDM) transmission has been intensively investigated recently due to its potential of doubling the capacity in comparison with single-polarization NFDM systems. However, up to now, due to many challenges in design and practical implementation, the demonstrated data rates of DP-NFDM transmission systems in experiments are still much lower than the record data rate of single-polarization NFDM transmissions (125 Gb/s). In this letter, by employing the concept of b-modulation and developing effective digital signal processing (DSP), we have experimentally demonstrated for the first time a high-capacity DP-NFDM transmission system, achieving a net data rate of 220 Gb/s with a spectral efficiency (SE) of 4 bits/s/Hz

Study of two-photon decays of pseudoscalar mesons via J/Psi radiative decays

Using a sample of 4.48 x 10(8) Psi(3686) events collected with the BESIII detector at the BEPCII collider, we study the two-photon decays of the pseudoscalar mesons pi(0,) eta , eta' , eta(1405), eta(1475), eta(1760), and X(1835) in J/Psi radiative decays using Psi(3686) -> pi(+) pi(-) J/Psi events. The pi(0), eta, and eta' mesons are clearly observed in the two-photon mass spectra, and the branching fractions are determined to be B(J/Psi -> gamma pi(0) -> 3 gamma) = (3.57 +/- 0.12 +/- 0.16) x 10(-5), B(J/Psi -> gamma eta -> 3 gamma) = (4.42 +/- 0.04 +/- 0.18) x 10(-4), and B(J/Psi -> gamma eta' -> 2 gamma) = (1.26 +/- 0.02 +/- 0.05) x 10(-4), where the first error is statistical and the second is systematic. No clear signal for eta(1405), eta(1475), eta(1760) or X(1835) is observed in the two- photon mass spectra, and upper limits at the 90% confidence level on the product branching fractions are obtained

Search for Baryon and Lepton Number Violation in J/ψ→Λc+e−+c.c.J/\psi\to\Lambda_c^+e^-+c.c.

Using $1.31\times10^9$ $J/\psi$ events collected by the BESIII detector at the Beijing Electron Positron Collider, we search for the process $J/\psi\to\Lambda_c^+e^-+c.c.$ for the first time. In this process, both baryon and lepton number conservation is violated. No signal is found and the upper limit on the branching fraction $\mathcal{B}(J/\psi\to\Lambda_c^+e^-+c.c.)$ is set to be $6.9\times10^{-8}$ at the 90\% Confidence Level