Son T. Le

Nonlinear Fourier transform for optical data processing and transmission: advances and perspectives

The nonlinear Fourier transform is a transmission and signal processing technique that makes positive use of the Kerr nonlinearity in optical fibre channels. I will overview recent advances and some of challenges in this field.

Multicarrier Approaches for High-Baudrate Optical-Fiber Transmission Systems With a Single Coherent Receiver

In this paper, we show the remarkable timing error (TE) and residual chromatic dispersion (CD) tolerance improvements of the filte bank multicarrier (FBMC) over orthogonal frequency division multiplexing (OFDM) for high-baudrate spectral slicing transmitter and single coherent receiver transmissions. For a 512 Gb/s 16 quadrature amplitude modulated (16QAM) spectrum slicing system at 1600 km of fibe transmission, the FBMC-based system reduces TE and residual CD penalties by more than 1.5 dB and 3 dB, in comparison to the OFDM-based system, respectively.

Nonlinear frequency division multiplexed transmissions with 64QAM

Record data rate of 50 Gb/s in nonlinear frequency division multiplexing (NFDM) transmission is experimentally demonstrated using 64 overlapping orthogonal 0.5 Gbaud channels with 64 QAM format, showing an improvement of 1 dB over conventional system at 976 km.

Raman fibre laser based amplification in long-haul/unrepeatered coherent transmission systems

The paper reviews the basic principles and recent advances of Raman fibre laser (RFL) based amplification techniques in long-haul/unrepeatered coherent transmission systems. Different aspects of RFL based amplification have been characterised, including signal power distributions and relative intensity noise (RIN). Various RFL based amplifier designs have been evaluated in long-haul coherent transmission systems. The results shows the Fabry-Perot fibre laser based amplifier with two fibre Bragg gratings (FBGs) gives significant Q factor penalty using symmetrical bidirectional pumping, as the RIN of the signal is increased dramatically. However, random distributed feedback fibre laser based amplifier with a single FBG near the output section can mitigate the RIN of the signal, which enables the use of bidirectional second order pumping and therefore gives the best transmission performance up to 7915 km. Furthermore, using random DFB fibre laser based amplifier has been proven to be effective to combat nonlinear impairment. In addition, unrepeatered transmission over >350 km fibre length using RFL based amplification technique has been demonstrated experimentally using DP-QPSK WDM signals.

Energy based transmission optimisation in nonlinear Fourier domain

The systems employing nonlinear Fourier transform (NFT) as a method of nonlinearity mitigation have recently become the subject of intensive study (see e.g. [1-4] and references therein). In particular the so-called nonlinear inverse synthesis (NIS) method was proposed in [2]. Within this method the data is modulated using the continuous part of the NFT spectrum. Then the time domain waveform is generated using the inverse NFT (INFT) before being launched into the fiber. At the receiver NFT operation is performed to retrieve the continuous NFT spectrum (Fig. 1a, see [4]). We consider here the model channel when signal evolution is described by the lossless nonlinear Schrodinger equation (NLSE) with AWGN term arising due to ideal distributed amplification [5]. The signal-noise interaction inside the NFT domain was studied in [3] including the noise statistics.

Simplified extended Kalman filter phase noise estimation for CO-OFDM transmissions

We propose a flexible simplified extended Kalman filter (S-EKF) scheme that can be applied in both pilot-aided and blind modes for phase noise compensation in 16-QAM CO-OFDM transmission systems employing a small-to-moderate number of subcarriers. The performance of the proposed algorithm is evaluated and compared with conventional pilot-aided (PA) and blind phase search (BPS) methods via extensive an Monte Carlo simulation in a back-to-back configuration and with a dual polarization fiber transmission. For 64 subcarrier 32 Gbaud 16-QAM CO-OFDM systems with 200 kHz combined laser linewidths, an optical signal-to-noise ratio penalty as low as 1 dB can be achieved with the proposed S-EKF scheme using only 2 pilots in the pilot-aided mode and just 4 inputs in the blind mode, resulting in a spectrally efficient enhancement by a factor of 3 and a computational effort reduction by a factor of more than 50 in comparison with the conventional PA and the BPS methods, respectively.

Impact of timing mismatch in multicarrier spectral-slicing transmission system using single coherent receiver

In this paper, we investigate the impact of timing mismatch among different sub-bands on the performance of a multicarrier spectral-slicing OFDM system with a single coherent receiver, both in the back-to-back configuration and long-distance fiber transmission. Two different timing mismatch models, namely linear timing error and Gaussian timing error, are introduced and investigated. Furthermore, the trade-off between nonlinear performance penalty and timing mismatch induced performance penalty under the impact of the number of subcarriers is investigated for the first time.