Laguerre Gauss Işınlarının Yüksek Dereceli Azimuthal İndekslerini Kullanan Yeni Bir Yörüngesel Açısal Momentum Kodlama Sistemi

Abstract

Optik vorteks (OV) ışınlarındaki yörüngesel açısal momentum (OAM), uzay modunun yeni bir boyutunu sunar çünkü farklı azimuthal OAM durumlarına sahip eş eksenli olarak yayılan optik vorteks ışınları karşılıklı olarak ortogonaldir. Optik iletişim sisteminin kapasitesini potansiyel olarak artırmak için ışınlar verimli bir şekilde çoğullanabilir ve çoklanabilir. Bu nedenle, şimdiye kadar, enine uzamsal modun azimutal ve radyal indeksleri birçok kez araştırılmıştır. Bu makale, Laguerre Gaussian (LG) ışınının azimuthal indislerine odaklanmaktadır. Optik iletişim sistemi için simülasyon yoluyla yüksek dereceli azimuthal indekslere sahip türbülans ve gürültü etkisi altında yeni bir OAM kodlama sistemi kurulmuştur. Vericide, farklı azimuthal indekslere sahip Laguerre Gaussian modunun bir dizi hologramı, her bir ışının bir veri bitini temsil ettiği çoklama ışınlarının koaksiyel iletimini sağlamak için kullanılır. Alıcıda, çoklanmış ışınları çoğullamadan arındırmak için iletilen ışınlara karşılık gelen eşlenik ışık alanının süperpozisyonu kullanılır. Faz kaydırma faktörü ve centroid algoritmasının kombinasyonu, her kanaldaki azimuthal indekslerin eş zamanlı olarak algılanmasını ve bilginin verimli bir şekilde çözülmesini gerçekleştirir. Makalede bir kodlama sisteminin performansına dair tartışmaları veriyoruz. Simülasyon sonuçları, dört ortogonal LG modu (M = 4) kullanıldığında 20 dB SNR’de 18,802 bit/s/Hz’lik bir MIMO kapasitesi elde edildiğini göstermektedir. Bu, tek modlu iletimlere göre yaklaşık üç kat artış sağlarken, türbülans mod saflığını −6,02 dB’den −1,25 dB’ye düşürür ve ortalama −4,77 dB’lik bir çapraz konuşma oluşturmuştur.

Keywords

• Serbest uzay haberleşmesi
• laguerre gauss ışınları
• yörüngesel açısal momentum
• çoklama ve çoklama çözme
• optik iletişim sistemi

A Novel Orbital Angular Momentum Coding System Using High Order Azimuthal Indices of Laguerre Gaussian Beams

Abstract

Orbital angular momentum in optical vortex beams offers a new dimension of space mode because coaxially propagating optical vortex beams with different azimuthal orbital angular momentum states are mutually orthogonal. The optical vortex beams can be efficiently multiplexed and demultiplexed to increase the capacity of the optical communication system. Therefore, the azimuthal and radial indices of the transverse spatial mode have been investigated many times. This paper focused on the azimuthal indices of the Laguerre Gaussian beams and a novel orbital angular momentum coding system under the influence of turbulence and noise with high order azimuthal indices was established through simulations of an optical communication system in free space. At the transmitter, a series of holograms of Laguerre Gaussian mode with different azimuthal indices were used to achieve coaxial transmission of multiplexed beams, where each beam represented a data bit. At the receiver, superposition of the conjugate light field corresponding to the transmitted beams was used to demultiplex the multiplexed beams. The combination of the phase shift factor and the centroid algorithm were realized for simultaneous detection of the azimuthal indices in each channel and efficient decoding of the information. In this article, for the first time, multiplex and demultiplex were investigated by using the centroid algorithm, keeping the radial index constant and taking different positive and negative values of the azimuthal index. Simulation results show that using four orthogonal LG modes (M = 4) achieves a MIMO capacity of 18.802 bits/s/Hz at 20 dB SNR, providing about a threefold increase over single-mode transmission, while turbulence reduces mode purity to −6.02 dB to −1.25 dB and induces an average crosstalk of −4.77 dB.

Keywords

• Free space communication
• laguerre gauss beams
• orbital angular momentum
• multiplexing and demultiplexing
• optical communication system

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