Bessel Mode Optical Links for Secure Free-Space Transmission

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Solution Overview

Problem

Existing optical communication systems lack effective physical layer security, particularly in free-space optical networks, where conventional methods such as quantum key distribution and chaotic cryptography face limitations in data rate, transmission distance, and security efficacy.

Innovation Solution

Employing Bessel modes in optical communications systems, which utilize a step-index multi-mode fiber to generate diffraction-free beams that enhance secrecy and spectral efficiency, and incorporate multidimensional signaling to improve security against eavesdropping attacks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional security methods (quantum key distribution, chaotic cryptography) are used in optical communication systems, then security is provided, but data rate is limited and transmission distance is constrained

Engineering Contradiction:

ImprovesecurityVSAvoiddata rate

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent transitions from conventional 2D modulation schemes to 3D spatial modulation using Bessel modes. By utilizing the radial dimension (mth order Bessel functions) in addition to azimuthal and axial dimensions, the system achieves multidimensional signaling that simultaneously improves security through mode diversity and data rate through increased degrees of freedom, resolving the contradiction between security and productivity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent changes the fundamental parameter space by employing Bessel modes with varying orders (m=0,1,2,...) and radial indices. This parameter transformation allows the system to encode information in the spatial distribution of optical fields, achieving both enhanced security through mode-specific encryption and higher data rates through parallel mode transmission

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional security methods are used in optical communication systems, then security is provided, but transmission distance is constrained

Engineering Contradiction:

ImprovesecurityVSAvoidtransmission distance

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

By introducing spatial dimensionality through Bessel modes, the system creates additional transmission channels that are inherently more robust to atmospheric turbulence. The higher-order Bessel modes provide diversity against channel fading, enabling secure communication over longer free-space optical links where conventional methods fail

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If Bessel modes are employed to improve secrecy capacity, then atmospheric turbulence effects benefit beam splitting attacks, but conventional schemes are vulnerable to such attacks

Engineering Contradiction:

Improvesecrecy capacityVSAvoidbeam splitting attacks

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts atmospheric turbulence, which normally degrades optical signals, into a security advantage. The random phase variations caused by turbulence create unique channel realizations for different Bessel modes, making eavesdropping through beam splitting attacks more difficult while the legitimate receiver can compensate for turbulence effects using channel state information

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Productivity

If multidimensional signaling is used to enhance security, then spectral efficiency improves, but system complexity increases

Engineering Contradiction:

Improvespectral efficiencyVSAvoidsystem complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent employs 3D spatial modulation using Bessel modes characterized by radial index and azimuthal order, adding spatial dimensions to the signal space. This enables parallel transmission of multiple data streams through orthogonal modes, achieving high spectral efficiency while the mode orthogonality naturally simplifies receiver design compared to other multidimensional approaches

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Bessel modes significantly improve secrecy capacity and spectral efficiency, effectively resisting beam splitting attacks and atmospheric turbulence, outperforming conventional schemes by enabling higher secret key rates and secure data transmission over longer distances.

Implementation Method 1

Bessel modes are employed—significantly outperform conventional schemes with respect to secrecy and advantageously and surprisingly benefit from atmospheric turbulence effects with respect to beam splitting attacks

Methodology Applied

Scientific EffectDiffraction-free beam propagation: Diffraction

Data Source

PatentUS10291318B2Physical layer security in optical communications using Bessel modes

Publication Date: 2019.05.14 NEC CORP

AI summary

Aspects of the present disclosure describe physical layer security in optical communications wherein Bessel modes are employed and significantly outperform conventional schemes with respect to secrecy and advantageously benefit from atmospheric turbulence effects with beam splitting attacks.