Robustness of OAM fiber modes to geometric perturbations

Ma, Zelin; Prabhakar, Gautam; Gregg, Patrick; Ramachandran, Siddharth

doi:10.1364/cleo_si.2018.sw3k.1

Cited by 5 publications

(7 citation statements)

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“…Among various fiber perturbations, moving or lifting the fiber out of the plane (i.e., out-of-plane fiber movement) is of great interest, since it introduces an extra Pancharatnam–Berry phase, also known as the geometric phase 43 , 44 . It is associated with the topological nature, which is different from the conventional propagation dynamic phase dependent on the fiber length.…”

Section: Concept Principle and Theorymentioning

confidence: 99%

“…Another impactful way to form an MDM system without MIMO-DSP is to employ OAM modes in an air-core fiber (ACF) 21 , 25 , 41 – 44 Note that the ACF retains its cylindrical symmetry, while the degeneracy between EH/HE modes in the same mode group is lifted due to the high-contrast index of the ACF 21 , 25 , 41 – 44 …”

Section: Introductionmentioning

confidence: 99%

“… – 44 Note that the ACF retains its cylindrical symmetry, while the degeneracy between EH/HE modes in the same mode group is lifted due to the high-contrast index of the ACF 21 , 25 , 41 – 44 …”

Section: Introductionmentioning

confidence: 99%

“…21,25,[41][42][43][44] Note that the ACF retains its cylindrical symmetry, while the degeneracy between EH/HE modes in the same mode group is lifted due to the high-contrast index of the ACF. 21,25,[41][42][43][44] Notably, diverse spatial mode bases, such as LP modes, linearly polarized orbital angular momentum (LP-OAM) modes, vector modes, and circularly polarized orbital angular momentum (CP-OAM) modes, have been successfully demonstrated in MDM fiber-optic communications, even for cylindrically symmetric fibers. However, to the best of our knowledge, there has been limited research on their detailed comparison, especially from a system-level point of view.…”

Section: Introductionmentioning

confidence: 99%

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Finding the superior mode basis for mode-division multiplexing: a comparison of spatial modes in air-core fiber

Wang,

Ai,

et al. 2023

Adv. Photon.

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Diverse spatial mode bases can be exploited in mode-division multiplexing (MDM) to sustain the capacity growth in fiber-optic communications, such as linearly polarized (LP) modes, vector modes, LP orbital angular momentum (LP-OAM) modes, and circularly polarized OAM (CP-OAM) modes. Nevertheless, which kind of mode bases is more appropriate to be utilized in fiber still remains unclear. Here, we aim to find the superior mode basis in MDM fiber-optic communications via a system-level comparison in air-core fiber (ACF). We first investigate the walk-off effect of four spatial mode bases over 1-km ACF, where LP and LP-OAM modes show intrinsic mode walk-off, while it is negligible for vector and CP-OAM modes. We then study the mode coupling effect of degenerate vector and CP-OAM modes over 1-km ACF under fiber perturbations, where degenerate even and odd vector modes suffer severe mode cross talk, while negligible for highorder degenerate CP-OAM modes based on the laws of angular momentum conservation. Moreover, we comprehensively evaluate the system-level performance for data-carrying single-channel and two-channel MDM transmission with different spatial mode bases under various kinds of fiber perturbations (bending, twisting, pressing, winding, and out-of-plane moving). The obtained results indicate that the CP-OAM mode basis shows superiority compared to other mode bases in MDM fiber-optic communications without using multiple-input multiple-output digital signal processing. Our findings may pave the way for robust shortreach MDM optical interconnects for data centers and high-performance computing.

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Section: Concept Principle and Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Finding the superior mode basis for mode-division multiplexing: a comparison of spatial modes in air-core fiber

Wang,

Ai,

et al. 2023

Adv. Photon.

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“…As such, LP modes of L ≠ 0 are never stable in a fiber, and their use necessarily requires pre-or post-processing, optically or electronically, for information recovery. Figure 5(a) shows the experimental setup [82] used for studying the mixing of two degenerate OAM or vector modes, in a 4-m long ring-core fiber [72] supporting stable propagation (i.e., without SOa-SOaa mixing) of high-|L| modes (|L| = 5, 6, 7). The incoming Gaussian beam at 1550 nm from an external cavity laser (ECL) is converted into the desired OAM or vector mode using a PBOE called q-plate [52,83].…”

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confidence: 99%

Propagation stability in optical fibers: role of path memory and angular momentum

Ramachandran

2020

Nanophotonics

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With growing interest in the spatial dimension of light, multimode fibers, which support eigenmodes with unique spatial and polarization attributes, have experienced resurgent attention. Exploiting this spatial diversity often requires robust modes during propagation, which, in realistic fibers, experience perturbations such as bends and path redirections. By isolating the effects of different perturbations an optical fiber experiences, we study the fundamental characteristics that distinguish the propagation stability of different spatial modes. Fiber perturbations can be cast in terms of the angular momentum they impart on light. Hence, the angular momentum content of eigenmodes (including their polarization states) plays a crucial role in how different modes are affected by fiber perturbations. We show that, accounting for common fiber-deployment conditions, including the more subtle effect of light’s path memory arising from geometric Pancharatnam–Berry phases, circularly polarized orbital angular momentum modes are the most stable eigenbasis for light propagation in suitably designed fibers. Aided by this stability, we show a controllable, wavelength-agnostic means of tailoring light’s phase due to its geometric phase arising from path memory effects. We expect that these findings will help inform the optimal modal basis to use in the variety of applications that envisage using higher-order modes of optical fibers.

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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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Robustness of OAM fiber modes to geometric perturbations

Cited by 5 publications

References 0 publications

Finding the superior mode basis for mode-division multiplexing: a comparison of spatial modes in air-core fiber

Finding the superior mode basis for mode-division multiplexing: a comparison of spatial modes in air-core fiber

Propagation stability in optical fibers: role of path memory and angular momentum

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

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