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1. Analysis of Nonlinear Fiber Kerr Effects for Arbitrary Modulation Formats

   https://doi.org/10.1109/JLT.2022.3213182  

   Rabbani, Hami; Hosseinianfar, Hamid; Rabbani, Hamed; Brandt-Pearce, Maite (January 2023, Journal of Lightwave Technology)

   Coherent optical transmission systems can be modeled as a four-dimensional (4D) signal space resulting from the two polarization states, each with two quadratures. Recently, nonlinear analytical models have been proposed capable of capturing the impact of Kerr nonlinearity on 4D constellations. None of these addresses the inter-channel nonlinear interference (NLI) imposed by arbitrary modulation formats in multi-channel wavelength division multiplexed (WDM) systems. In this paper, we introduce a general nonlinear model for multi-channel WDM systems that is valid for arbitrary modulation formats, even asymmetric ones. The proposed model converges to the previous models, including the EGN model, in the special case of polarization multiplexed systems. The model focuses on the cross-phase modulation (XPM) nonlinear term that lies at the heart of the NLI in multi-channel WDM systems operating on standard high dispersion single-mode fiber. We show that strategic mappings of the modulation format's coordinates to the polarization states can reduce the NLI undergone by these formats. 

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2. Can NLI Models Verify QA Systems’ Predictions?

   https://doi.org/10.18653/v1/2021.findings-emnlp.324  

   Chen, Jifan; Choi, Eunsol; Durrett, Greg (January 2021, Findings of the Association for Computational Linguistics: EMNLP 2021)

   To build robust question answering systems, we need the ability to verify whether answers to questions are truly correct, not just “good enough” in the context of imperfect QA datasets. We explore the use of natural language inference (NLI) as a way to achieve this goal, as NLI inherently requires the premise (document context) to contain all necessary information to support the hypothesis (proposed answer to the question). We leverage large pre-trained models and recent prior datasets to construct powerful question conversion and decontextualization modules, which can reformulate QA instances as premise-hypothesis pairs with very high reliability. Then, by combining standard NLI datasets with NLI examples automatically derived from QA training data, we can train NLI models to evaluate QA models’ proposed answers. We show that our approach improves the confidence estimation of a QA model across different domains, evaluated in a selective QA setting. Careful manual analysis over the predictions of our NLI model shows that it can further identify cases where the QA model produces the right answer for the wrong reason, i.e., when the answer sentence cannot address all aspects of the question. 

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3. Enhancing Optical Network Emulation (ONE) with Fast Gaussian Noise Modeling of Nonlinear Interference

   https://doi.org/10.1109/ICTON67126.2025.11125290  

   Latha, Aparaajitha Gomathinayakam; Ridwanur_Rahim, Muhammad; Hui, Ron; Tacca, Marco; Fumagalli, Andrea (July 2025, IEEE)

   The Optical Network Emulation (ONE) engine is a real-time, multi-container software platform designed to model and emulate open optical transport networks with realistic fidelity. This paper introduces an enhanced version of the ONE engine that integrates a distributed implementation of a Gaussian Noise (GN) model for estimating nonlinear interference (NLI) in wavelength division multiplexing (WDM) systems. The inclusion of the GN model enables more realistic emulation of nonlinear signal degradation across diverse link configurations and operating conditions. The enhanced ONE package is then used to document the model’s impact on system performance under varying transmission conditions, including signal launched power and increased spectral loading. With this upgrade, the ONE engine expands its utility for research, development, and education, providing a scalable and flexible environment for testing physical-layer impairments and control strategies in software-defined optical networks. 

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4. Parametric study of the polarization dependence of nonlinear Breit–Wheeler pair creation process using two laser pulses

   https://doi.org/10.1063/5.0165788  

   Qian, Qian; Seipt, Daniel; Vranic, Marija; Grismayer, Thomas E; Blackburn, Thomas G; Ridgers, Christopher P; Thomas, Alexander_G R (October 2023, Physics of Plasmas)

   With the rapid development of high-power petawatt class lasers worldwide, exploring physics in the strong field QED regime will become one of the frontiers for laser–plasma interactions research. Particle-in-cell codes, including quantum emission processes, are powerful tools for predicting and analyzing future experiments where the physics of relativistic plasma is strongly affected by strong field QED processes. The spin/polarization dependence of these quantum processes has been of recent interest. In this article, we perform a parametric study of the interaction of two laser pulses with an ultrarelativistic electron beam. The first pulse is optimized to generate high-energy photons by nonlinear Compton scattering and efficiently decelerate electron beam through the quantum radiation reaction. The second pulse is optimized to generate electron–positron pairs by the nonlinear Breit–Wheeler decay of photons with the maximum polarization dependence. This may be experimentally realized as a verification of the strong field QED framework, including the spin/polarization rates. 

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5. Linear Polarization Optimization for Wideband MIMO Systems With Reconfigurable Arrays

   https://doi.org/10.1109/TWC.2023.3297130  

   Castellanos, Miguel R.; Heath, Robert W. (March 2024, IEEE Transactions on Wireless Communications)

   Reconfigurable arrays mold the propagation en- vironment to benefit wireless systems. We use single-port polarization-reconfigurable antennas in a wideband multiple- input multiple-output (MIMO) system and demonstrate the efficacy of reconfiguration techniques based on analytical channel models. We apply a double-directional channel model to show that polarization reconfiguration acts as an additional precoding step on an unpolarized channel. We use Jensen’s inequality to upper bound the spectral efficiency and leverage the relaxed objective to derive closed-form expressions for the optimal polarization angles at each antenna. We also derive upper bounds on the performance of a polarization reconfigurable system and develop an efficient procedure for polarization reconfiguration that aims to maximize these upper bounds. Numerical results show that the proposed simplified methods achieve near-optimal in wideband MIMO settings. 

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