【摘要】：攜帶軌道角動量的光束擁有許多奇異的特性,比如:螺旋型的波前相位和圓環(huán)型的光強分布等,基于這些特性,攜帶軌道角動量的光束在許多領(lǐng)域都有巨大的應(yīng)用價值。在光通信方面,光波的軌道角動量被認(rèn)為是除了幅度、相位、波長和偏振外的一種新的調(diào)制自由度,有望為光纖信道復(fù)用提供一個新的緯度。本論文在結(jié)合多種軌道角動量模式傳輸波導(dǎo)的研究分析下,設(shè)計了一種具有多層結(jié)構(gòu)的軌道角動量模式光纖,并利用一款有限元仿真軟件COMSOL Multiphysics對其進了行模擬仿真,驗證了軌道角動量模式在該多層結(jié)構(gòu)的軌道角動量模式光纖中的穩(wěn)定性及走離長度。取得以下工作成果:1)通過研究該多層結(jié)構(gòu)的軌道角動量模式光纖的模式有效折射率之差,矢量模的2π走離長度和10ps走離長度,發(fā)現(xiàn):該多層結(jié)構(gòu)的軌道角動量模式光纖能夠支持比較多的軌道角動量模式穩(wěn)定傳輸,至少支持60個軌道角動量模式,拓?fù)浜蓴?shù)可從1到15。同時,部分模式的10ps走離長度能夠達(dá)到10km以上。2)通過研究該光纖的第四層介質(zhì)的厚度和折射率與模式有效折射率之差,2π走離長度和10ps走離長度的關(guān)系,發(fā)現(xiàn):當(dāng)增大第四層介質(zhì)的厚度時,會增加所支持的軌道角動量模式的數(shù)量;當(dāng)增大第四層介質(zhì)的折射率時,會增加所支持的軌道角動量模式的數(shù)量,而且會增大模式有效折射率之差,提高軌道角動量模式的穩(wěn)定性。但是伴隨著第四層介質(zhì)的厚度和折射率的增大的同時,大多數(shù)模式的2π走離長度和10ps走離長度也會減小。3)通過研究基于該多層結(jié)構(gòu)的軌道角動量模式光纖的定向耦合器,發(fā)現(xiàn):當(dāng)兩個光纖的第四層之間的間距為1μm時,模式HE_(10,1)、EH_(8,1)、HE_(11,1)和EH_(9,1)的耦合長度都小于6mm,當(dāng)間距增大時,模式的耦合長度呈增大的趨勢�？偟膩碚f,本文提出并研究了一種新型多層結(jié)構(gòu)的軌道角動量模式光纖,發(fā)現(xiàn)具有五層結(jié)構(gòu)的光纖能夠支持60個軌道角動量模式的穩(wěn)定傳輸,并具有良好的模式穩(wěn)定性指標(biāo)。該結(jié)果比參考文獻中的三層結(jié)構(gòu)的光纖多支持24個軌道角動量模式,這表明該五層結(jié)構(gòu)的軌道角動量模式光纖對于模式復(fù)用更為有利。
[Abstract]:Beams carrying orbital angular momentum have many strange properties, such as helical wavefront phase and toroidal intensity distribution. Based on these characteristics, orbital angular momentum beams have great application value in many fields. In optical communication, orbital angular momentum of optical wave is considered as a new modulation degree of freedom besides amplitude, phase, wavelength and polarization, which is expected to provide a new latitude for fiber channel multiplexing. In this paper, a kind of orbital angular momentum mode optical fiber with multilayer structure is designed, and a finite element simulation software COMSOL Multiphysics is used to simulate it. The stability and walking length of orbital angular momentum mode in the multilayer orbital angular momentum mode fiber are verified. The results are as follows: 1) the difference of the effective refractive index of the orbital angular momentum mode fiber, the 2 蟺 walk length of vector mode and the 10ps walk length of the multilayer structure are studied. It is found that the multilayer orbital angular momentum mode fiber can support more stable orbital angular momentum modes, at least 60 orbital angular momentum modes, and the topological charge number can range from 1 to 15. At the same time, the 10ps walk length of partial mode can reach above 10km. 2) by studying the difference between the thickness and refractive index of the fourth layer of the fiber and the effective refractive index of the mode, the relationship between the walk length of 2 蟺 and the walk length of 10ps is studied. It is found that when the thickness of the fourth layer medium is increased, the number of supported orbital angular momentum modes will be increased, and when the refractive index of the fourth layer medium is increased, the number of supported orbital angular momentum modes will increase. Moreover, the difference of the effective refractive index of the mode will be increased, and the stability of the orbital angular momentum mode will be improved. However, with the increase of the thickness and refractive index of the fourth layer medium, the 2 蟺 walk length and the 10ps walk length of most modes will also decrease. 3) the directional coupler of orbital angular momentum mode fiber based on the multilayer structure is studied. It is found that when the distance between the fourth layers of the two fibers is 1 渭 m, the coupling lengths of the mode HE_ (10 ~ 1), EH_ (8 ~ 1), HE_ (11 ~ 1) and EH_ (9 ~ 1) are all less than 6 mm. When the spacing increases, the coupling length of the mode increases. In general, a novel multilayer orbital angular momentum mode fiber is proposed and studied. It is found that the fiber with five layers structure can support the stable transmission of 60 orbital angular momentum modes and has good stability index. The results support 24 orbital angular momentum modes more than the three-layer optical fibers in the reference, which indicates that the orbital angular momentum mode fibers with this five-layer structure are more favorable for mode multiplexing.
【學(xué)位授予單位】：深圳大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN253

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本文編號：2279178