Modeling the Breakdown in Degeneracy for High-Index-Contrast Ring Core Fiber

Banawan, Mai; Wang, Lixian; LaRochelle, Sophie; Rusch, Leslie A.

doi:10.1364/ofc.2020.w1b.2

Cited by 3 publications

(7 citation statements)

References 8 publications

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“…Several studies in the literature corroborate predictions from our model. First, the formalism introduced in [12] and extended here agrees with the theoretical formulation newly introduced in [13] for fiber eigenmodes. Second, our results for coupling between A(AA) OAM mode pairs being low for high mode orders are compatible with predictions in [6].…”

Section: Discussionmentioning

confidence: 63%

“…Using complex space inner product properties the rotated electric field of mode (±) lA, described in (2), can be written as OAM ± ±l,rotated = f l+1 e ±jlϕ e ±jθσ ± + g l+1 e ±j(l+2)ϕ e ∓jθσ ± = f l+1 e ±jl(ϕ +θ) e ±jθσ ± + g l+1 e ±j(l+2)(ϕ +θ) e ∓jθσ ± = OAM ± ±l e ±j(l+1)θ (12) where ϕ is the azimuthal angle in the new, rotated frame. From (12), rotating an OAM mode only introduces a phase shift to the field profile.…”

Section: Appendix B Monte Carlo Prediction Of Propagation Effectsmentioning

confidence: 99%

“…In [12], we proposed an updated numerical approach that predicts and quantifies these missing effects. In this paper, we extend our work, using our model to compare and contrast the performance of various fiber designs.…”

Section: Introductionmentioning

confidence: 99%

“…The authors assumed that perturbed fiber eigenmodes can be expanded as a superposition of unperturbed modes. The authors limited their study to an analytical formulation, without quantifying the coupling coefficients as we did in [12]. They did not examine numerical mode propagation and XT assessment.…”

Section: Introductionmentioning

confidence: 99%

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Quantifying the Coupling and Degeneracy of OAM Modes in High-Index-Contrast Ring Core Fiber

Banawan

Wang

LaRochelle

et al. 2021

J. Lightwave Technol.

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We study orbital angular momentum (OAM) mode coupling in ring-core fibers (RCFs) due to elliptical shape deformation. We introduce a coupling model based on numerical mode solver outputs of perturbation. We show improved predictions in calculating coupling strength compared to the classical modeling approach. Our model captures and quantifies the disparate behaviors of coupling in lower and higher order degenerate OAM modes. The ideal orthogonality of modes is undermined by fiber imperfections. Our model predicts the OAM order at which the orthogonality within OAM mode pair is maintained despite elliptical deformation. We use our coupling model to simulate propagation effects and compare the performance of two fibers (thin and thick RCF) designed under the same constraints. Our numerical propagation results show different performance for the two fibers under the same level of elliptical deformation. This model uncovers distinct digital signal processing requirements for these two types of fiber, and predicts their signal-to-noise ratio penalty. For each fiber, we examine the large number of supported modes and find the optimal subset of mode groups, i.e., the groups with the lowest penalty. We show that this optimal subset is different from that predicted during the fiber design optimization.Index Terms-Orbital angular momentum (OAM), ring core fiber (RCF), coupled-mode equations (CMEs), elliptical deformation, mode coupling, crosstalk (XT), multiple-input multipleoutput (MIMO), digital signal processing (DSP)

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Section: Discussionmentioning

confidence: 63%

Section: Appendix B Monte Carlo Prediction Of Propagation Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantifying the Coupling and Degeneracy of OAM Modes in High-Index-Contrast Ring Core Fiber

Banawan

Wang

LaRochelle

et al. 2021

J. Lightwave Technol.

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“…We assume that the network traffic demand requires 16 spatial channels (4 OAM MGs). Under these conditions and assigning QPSK to all channels, [26] found the SNR penalty due to XT. Unlike that work, we use available SNR margin after XT to increase modulation beyond QPSK , i.e., a bit allocation.…”

Section: A Xt When Allocating Complete Mgsmentioning

confidence: 99%

OAM Mode Selection for High-Speed Optical Communications: A Bit Loading Approach

Nejad¹,

Banawan²,

Rusch³

2022

J. Lightwave Technol.

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Occupying more channels increases transmission rate, however, crosstalk increases to an unacceptable level long before all 24 channels can be exploited. The crosstalk is not uniform between modes, hence occupying different subsets of channels leads to vastly different achievable transmission capacities. In addition to optimizing occupied subsets of channels, we adopt a bit loading approach.We examine several resource allocation strategies in a coherent detection system, starting with typical OAM mode group granularity (all channels in a group occupied) and ending with single channel granularity. By exhaustive search at mode group granularity, we find a bit load increasing the total capacity by ∼15% compared to a minimax solution for mode group allocation. Single channel granularity imposes great computational effort to optimize bit loading. We propose search algorithms that are computationally tractable and improve capacity by ∼30% vis-àvis the minimax solution for mode groups. Finally, we examine the impact of signal-to-noise ratio (SNR) and receiver digital signal processing (DSP) complexity on the overall capacity. We include a discussion of DSP with limited or with no multi-input, multioutput (MIMO) processing.Our algorithms could be applied to any mode multiplexing fiber, as it only relies on knowledge of the crosstalk matrix across modes.

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Crosstalk Aware OAM Mode Selection for Space Division Multiplexed Optical Networks

Nejad

Banawan

Rusch

2020

2020 IEEE Photonics Conference (IPC)

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Modeling the Breakdown in Degeneracy for High-Index-Contrast Ring Core Fiber

Abstract: Our numerical model of elliptical deformation of ring cores uncovers distinctly different behaviors of lower and higher order OAM modes. Degeneracy of modes, across topological charge and polarization are laid bare in simulations.

Cited by 3 publications

References 8 publications

Quantifying the Coupling and Degeneracy of OAM Modes in High-Index-Contrast Ring Core Fiber

Quantifying the Coupling and Degeneracy of OAM Modes in High-Index-Contrast Ring Core Fiber

OAM Mode Selection for High-Speed Optical Communications: A Bit Loading Approach

Crosstalk Aware OAM Mode Selection for Space Division Multiplexed Optical Networks

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