Frequency-Domain Hybrid Modulation Formats for High Bit-Rate Flexibility and Nonlinear Robustness

Since the deployment of the first commercial polarization-multiplexed (PM) QPSK 100G systems, the evolution of coherent optical communications in the last decade has been largely dominated by single-carrier quadrature amplitude modulation (QAM) based modulation of increasing constellation size. However, as the data traffic becomes more dynamic and heterogeneous, an efficient use of the optical link requires more flexible modulation schemes, capable of adapting data-rate and distance with fine granularity. While typical multi-carrier modulation schemes composed of hundreds of subcarriers may be inadequate for optical transmission, namely due its high peak-to-average power ratio and increased nonlinearity penalties, it has been recently shown that few-carrier modulation (with symbol rate in the order of 2-4 GBaud) can provide an increased robustness to nonlinear propagation impairments. In this paper, we exploit the concept of frequency-domain hybrid modulation formats (FDHMF) based on electronic subcarrier multiplexing with the use of different QAM formats on each subcarrier to simultaneously enhance the data-rate flexibility and the nonlinear propagation performance of the optical link. In addition, by properly designing the FDHMF signal, an increased tolerance against optical filtering can also be achieved. Using the enhanced Gaussian noise model, we report a comprehensive theoretical study on the performance of FDHMF, considering independent-and joint-subcarrier forward-error correction strategies, optimization of power ratio between subcarriers, and corresponding impact of fiber nonlinearities. These theoretical insights are then validated by a broad range of wavelength-division multiplexing experiments with per-channel bit-rates in the range of 150G to 250G. The obtained results demonstrate that FDHMF is an effective solution for the implementation of flexible transponders capable of adapting the data rate to the lightpath quality of transmission: An enabling technology for the introduction of future elastic optical networks

Combining probabilistic shaping and nonlinear mitigation: Potential gains and challenges

We experimentally compare different options for transmission at 200G net bit-rate and demonstrate that the benefits of probabilistic shaping and nonlinear mitigation via SRO and/or DBP can be effectively combined to enable propagation reach enhancement of > 40%

Effectiveness of Digital Back-Propagation and Symbol-Rate Optimization in Coherent WDM Optical Systems

We apply DBP to an experimental WDM system where multisubcarrier transmission provides a 12% reach gain vs. single-carrier. DBP provides further gain for both single- and multisubcarrier systems but significantly underperforms ideal theoretical predictions

Low-Complexity Time-Domain DBP Based on Random Step-Size and Partitioned Quantization

We propose and experimentally validate a low-complexity time-domain (TD) digital backpropagation (DBP) algorithm for fiber nonlinearity compensation, targeting an optimized hardware implementation. To counteract the coherent accumulation of numerical quantization errors between DBP steps, we propose a random step-size distribution along the optical link (with pm5% interval around the optimal step-size). In addition, to further reduce the average quantization bit precision requirements, we propose a partitioned quantization technique, enabling to quantize the finite-impulse response (FIR) filter tail coefficients with significantly lower precision. The proposed low-complexity DBP algorithm is experimentally demonstrated over a 2592 km long-haul wavelength division multiplexing transmission system with 21 imes32 GBaud PM-16QAM optical channels. Employing the proposed step-size randomization together with dual-time-slot quantization, we demonstrate penalty-free operation at an average of sim4 b per FIR coefficient, leading to a 60% complexity reduction when compared to the standard TD-DBP implementation

Theoretical and experimental assessment of nonlinearity mitigation through symbol rate optimization

We investigated the reach increase obtained through non-linearity mitigation by means of transmission symbol rate optimization (SRO). We did this first theoretically and simulatively. We show that for PM-QPSK systems at full-C-band the reach increase may be substantial, on the order of 10%-25%, with optimum symbol rates on the order of 2-to-6 GBaud. We extended the investigation to PM-16QAM, where we found a qualitatively similar effect, although the potential reach increase is typically only about half that of PM-QPSK. We then set up an experiment to obtain confirmation of the theoretical and simulative predictions. We demonstrated a reach increase of 11% in a 19-channel, 128Gbit/s per channel, PM-QPSK experiment, when going from single-carrier per channel to multi-subcarrier (up to 16 subcarriers per channel) transmission. The experiment reached 14,100 km over PSCF, with 110 km spans and EDFA-only amplification. The results matched well the model predictions

Current status of Drosophila suzukii classical biological control in Italy

For over a decade, the invasive pest Drosophila suzukii (Matsumura) has threatened the soft-skinned fruit production worldwide, causing increased management costs and yield losses. Current integrated pest management (IPM) exploits different control tools but relies mainly on insecticides. The local natural enemy community mostly consists of generalist species, mainly parasitoids attacking the puparia of the fruit fly. These antagonists resulted unable to control the pest efficiently, regardless the adoption of conservative or augmentative approaches. By contrast, in the native area of D. suzukii, sympatric larval parasitoids have co-evolved with the pest and provide a stable control of its population. Foreign explorations and quarantine risk assessment studies for classical biological control programs have identified different species of parasitoids characterized by a variable level of specificity. The Japanese G1 lineage of the larval endoparasitoid Ganaspis brasiliensis (Ihering) has proved to be much more selective and efficient than other larval parasitoids, including Leptopilina japonica Novković & Kimura recently reported in Europe. In this context, a voluntary partnership of Italian researchers imported a colony of the G1 lineage of G. brasiliensis into Italian quarantine facilities and proposed its release in Italian fields. A three-year working program has been set up in several locations of nine Italian regions/provinces. Field releases of laboratory-reared parasitoids have been planned. Pre- and post-release samplings of fresh and fallen fruits around the release points will be undertaken to assess the impact of the exotic G. brasiliensis on D. suzukii and its potential interactions with other non-target insects in the field. The possible establishment of this efficient and specific biological control agent would promote a long-lasting control of this invasive species less dependent on the use of chemicals, reducing the negative effects associated with the