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We demonstrate real-time CD equalization (CDE) for coherent optical transmission systems using a low complexity time-domain (TD) multiplierless finite-impulse response (FIR)-based equalizer, based on a field-programmable gate array (FPGA) implementation. The real-time operation is performed for a single-channel 2.5 Gb/s QPSK optical signal with a performance penalty of only ∼0.15 dB with respect to...
Stokes space based digital signal processing (DSP) techniques can improve polarization demultiplexing, polarization dependent losses compensation, and other polarization-related tasks in coherent receivers, particularly in terms of convergence speed and transparency to higher-level M-ary modulated signals. This paper reports recent advances on Stokes space based DSP for coherent optical communications...
In this paper, we review our recent advances in the implementation of quantum communication systems. We start by discussing two types of optical quantum sources. A source based on a fainted semiconductor laser and another based on the four-wave mixing process. Afterwards, we discuss information encoding techniques in quantum states suitable to be used in fibre-optic quantum communication systems....
We experimentally demonstrate a PM-16QAM/64QAM triple-carrier 400G superchannel compatible with the 62.5 GHz grid. The optimum power ratio between carriers is analytically determined using the EGN model, enabling a maximum reach of 1700 km.
We experimentally demonstrate a flexible coherent UDWDM system with support to optical-wireless links and adaptive DP-QPSK/DP-16QAM modulation, enabled by Stokes-based polarization-demultiplexing. The system is shown to be resilient to dynamic power ranges of >12 dB.
We experimentally demonstrate a reduced complexity time-domain CD equalizer in a dual-carrier 400G PM-16QAM system, yielding hardware savings of over 99% in terms of multipliers, and a latency reduction of ∼80% over standard frequency-domain CD equalization.
We report a hardware optimization for frequency and phase recovery algorithms based on Mth-order power schemes, evaluating the accuracy of the reported architecture with an 8-bit DSP in real-time for a 1.25 and 2.5 Gb/s DQPSK signal.
Random polarization rotations caused by residual fiber birefringence is an important physical effect in optical coherent systems employing polarization-division multiplexing. The specificity of the large penalties induced by polarization-related impairments make polarization-dedicated equalization subsystems mandatory for the design of flexible coherent receivers. It has recently been shown that 3-dimensional...
We report our recent advances in the implementation of very high-speed optical channels (targeting 400 Gbps and 1 Tbit) based on multi-carrier super-channels supported by intense digital signal processing. We present results on modulation format agnostic polarization demultiplexing, computationally efficient chromatic dispersion equalization, and digital compensation of nonlinear impairments.
In this work, we experimentally implement an adaptive polarization demultiplexing (PolDemux) technique based on the representation of the state of polarization (SOP) of the signal in the Stokes space in bidirectional ultra-dense wavelength-division-multiplexed (U-DWDM) optical metro networks. BER measurement is used to assess the quality of DP-QPSK and DP-16QAM signals in back-to-back and after 80...
We experimentally assess the performance of dual- and triple-carrier 5×400G superchannels (5.33 b/s/Hz) for ultra-long-haul transmission (>6000 km). Using digital backpropagation with a coupled equations approach, we demonstrate an extended propagation reach of up to 1600 km.
We report a field-trial of bidirectional coherent Nyquist UDWDM-PON using off-the-shelf real-time FPGA-based transceivers, coexisting with GPON, RF Video and NG-PON2. A sensitivity of −44.5 dBm is achieved for 64×2.5 Gb/s DQPSK, with a 17 dB dynamic power range for US channels.
We experimentally demonstrate a parallel split-step Fourier method in an ultra-long-haul dual-carrier 400G transmission system. For a reach enhancement of 500–800 km over linear equalization, we demonstrate a 5× reduction of the step-size when compared to the standard split-step Fourier method.
A best fitting plane method and its application for Stokes space based polarization demultiplexing of a PDM-QPSK signal is presented. In particular, we investigate the dynamics of the normal vector to the plane, and the way its orientation depends on the step-size parameter of the method, among other parameters. It is also analysed how the performance of the method calculating the best fitting plane...
We demonstrate an hardware implementation of nonlinear equalization algorithms, numerically assessed using a polarization-multiplexed 16 quadrature amplitude modulation (PM-16QAM) transmission system. Nonlinear equalization is based on split-step Fourier (SSF) method and on a simplified Volterra series nonlinear equalizer (simVSNE). Hardware implementation is performed using a co-simulation strategy...
Digital signal processing (DSP) is nowadays a key enabling technology in coherent optical transmission systems, triggering an increasing research effort on the development and optimization of DSP subsystems. The first DSP development step is often based on the use of simulation tools and offline processing of experimental data. Complementarily, real-time implementation is a critical implementation...
We propose a novel split-step method for digital backpropagation in which the linear and nonlinear steps are applied in parallel, favouring hardware implementation. Numerical results show significant performance advantage over the classic split-step Fourier method.
This paper reports the first coherent WDM-PON (16×2.5 Gb/s QPSK) experimental demonstration with real-time Nyquist OLT transmitters and real-time ONU receivers. Both transmitters/receivers implemented in FPGA use a simple 8-bit DSP architecture. An optimal transmitted power of −7 dBm per channel is achieved for 50 km, 1∶16 split and 2.5 GHz grid.
To overcome the shortage of 3He detectors for subcritical experiments in the IPEN/MB-01 reactor, some experiments were performed using less sensitive detectors, such as BF3, and a logic input module, which sum the counts from different detectors. Through macroscopic neutron noise technique, the Auto Power Spectral Densities (APSD) were obtained for each detector configuration and various subcritical...
Multiplying Subcritical Systems were for a long time poorly studied and its theoretical description remains with plenty open questions. Great interest on such systems arose partly due to the improvement of hybrid concepts, such as the Accelerator-Driven Systems (ADS). Along with the need for new technologies to be developed, further study and understanding of subcritical systems are essential also...
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