本文選題：空分復(fù)用 + 模分復(fù)用��； 參考：《北京郵電大學(xué)》2015年碩士論文

【摘要】：高速光纖通信系統(tǒng)中的空分復(fù)用(Space division multiplexing, SDM)是一種全新的光纖信道復(fù)用方式。研究空分復(fù)用是為了解決日益緊缺的單模光纖的信道容量,它采用的復(fù)用方法是在多芯或少模／多模光纖中利用光纖在空間上的自由度來復(fù)用信道容量。其中,模分復(fù)用(Mode division multiplexing, MDM)是空分復(fù)用的一種實(shí)現(xiàn)方法,指的是在少模/多模中,采用互相正交的空間模式為信道,從而實(shí)現(xiàn)空間復(fù)用的方法。 模式轉(zhuǎn)換方法是實(shí)現(xiàn)模分復(fù)用方法的核心技術(shù),實(shí)現(xiàn)任意模式間高效、快速的精確轉(zhuǎn)換,對光模式的精確控制和選擇方法的研究是模分復(fù)用技術(shù)進(jìn)一步推廣的基礎(chǔ)。近幾年,從光纖通信系統(tǒng)中模分復(fù)用關(guān)鍵技術(shù)研究成果我們可以得出,目前對于模分復(fù)用中模式轉(zhuǎn)換方法的設(shè)計(jì)可以歸為兩類,即光波導(dǎo)類和空間光路類。模式轉(zhuǎn)換是光纖通信系統(tǒng)中模分復(fù)用技術(shù)的關(guān)鍵研究點(diǎn),本論文提出的基于空間光調(diào)制器的模式控制與選擇方案屬于空間光路型模式轉(zhuǎn)換方法,該方法對器件要求低,不需要針對每一種方案特殊定制專一的光路元件,更易于實(shí)現(xiàn)。 論文首先分析了國內(nèi)外對于模分復(fù)用這一課題的研究進(jìn)展,分析選題背景和選題依據(jù)。然后介紹了課題中涉及到的基本理論知識(shí),包括二維傅里葉變換相關(guān)理論、空間頻譜、傳遞函數(shù)及透鏡的傅里葉變換性質(zhì)、空間光調(diào)制器相關(guān)概念等。論文結(jié)合了光學(xué)傅里葉系統(tǒng)的結(jié)構(gòu)與光場分布模式特征,提出了利用空間光調(diào)制器和模擬退火優(yōu)化技術(shù)實(shí)現(xiàn)對模式間進(jìn)行精確控制和選擇的方法,并給出了其仿真結(jié)果。最后對研究方案的模式轉(zhuǎn)換效果和方案模型的執(zhí)行效率做橫向分析,并提出了局部退火、圖形處理器(Graphic Processing Unit, GPU)等進(jìn)一步優(yōu)化方案,完善仿真方案模型。結(jié)果表明,本文提出的“空分復(fù)用中利用空間光調(diào)制器實(shí)現(xiàn)對光模式的精確控制和選擇方法”能夠?qū)崿F(xiàn)任意模式間高效、快速的精確轉(zhuǎn)換。 本論文的研究內(nèi)容和創(chuàng)新點(diǎn)： 1、本論文提出基于光學(xué)傅里葉系統(tǒng)和空間光調(diào)制器的任意模式間自由轉(zhuǎn)換的仿真方案,并詳細(xì)記錄該方案的MATLAB仿真實(shí)現(xiàn)過程。 首先利用拉蓋爾-高斯函數(shù)可以推導(dǎo)出待轉(zhuǎn)換模式和目標(biāo)模式場分布的理論表達(dá)式。在此基礎(chǔ)上,基于透鏡的傅里葉變換性質(zhì)能夠推導(dǎo)出本仿真平臺(tái)中待轉(zhuǎn)換模式經(jīng)透鏡1到達(dá)空間光調(diào)制器左側(cè)的場分布和目標(biāo)模式經(jīng)透鏡2到達(dá)空間光調(diào)制器右側(cè)的場分布,方便下一步計(jì)算加載到空間光調(diào)制器上的模式間傳遞函數(shù)原型。理想的模式間傳遞函數(shù)的表達(dá)式是將空間光調(diào)制器右側(cè)和左側(cè)的光場分布做除法運(yùn)算,由此可以知道理想的模式間傳遞函數(shù)是因待轉(zhuǎn)換模式和目標(biāo)模式的不同而不同的,但是其計(jì)算方法都是一樣的,至此理論上的模式間自由轉(zhuǎn)換方案能夠被驗(yàn)證是可行的。 2、提出基于計(jì)算機(jī)模擬優(yōu)化算法的精確模式轉(zhuǎn)換控制和選擇方法 由于本仿真模型所對應(yīng)的實(shí)驗(yàn)方案選用的是僅能改變加載相位的反射型空間光調(diào)制器,而理想的模式間傳遞函數(shù)的表達(dá)式是攜帶幅度和相位信息的復(fù)數(shù)矩陣,如果簡單地去除幅度信息,剩下的相位部分作為模式間傳遞函數(shù)加載到空間光調(diào)制器上,會(huì)造成信息的大量缺失,模式間轉(zhuǎn)換的精確程度很低。所以如何調(diào)整相位信息以實(shí)現(xiàn)較為精確的任意模式轉(zhuǎn)換是本論文的一項(xiàng)關(guān)鍵問題。本論文提出了基于計(jì)算機(jī)模擬優(yōu)化算法-模擬退火算法對僅有相位信息的模式間傳遞函數(shù)進(jìn)行隨機(jī)逐點(diǎn)的相位變更,每一次變更后都依模擬退火算法選擇概率接受或放棄變更動(dòng)作,這樣能夠?qū)虞d到空間光調(diào)制器的模式間傳遞函數(shù)實(shí)現(xiàn)實(shí)時(shí)控制,光束通過這種實(shí)時(shí)變化的模式轉(zhuǎn)換方案模型后,利用模擬退火算法的全局優(yōu)化性能,能夠獲得最接近理想目標(biāo)模式的退火后目標(biāo)模式,最終實(shí)現(xiàn)模式間的精確轉(zhuǎn)換。 3、本論文對精確模式轉(zhuǎn)換方案的實(shí)現(xiàn)效果做了多方面分析,通過局部退火、改變終止條件、加入GPU等方式提高轉(zhuǎn)換方案效率和精度。 1)以局部退火代替全局退火：根據(jù)理想光斑尺寸,將計(jì)算范圍縮小為以光斑中心出發(fā)的小區(qū)域,避免無實(shí)際意義區(qū)域的運(yùn)算消耗,傳遞函數(shù)相位圖更改范圍也做相應(yīng)修正,可以有效縮短運(yùn)算時(shí)間。 2)退火終止條件自適應(yīng)化：退火終止條件根據(jù)模式和退火效果做自適應(yīng)化處理,當(dāng)多次迭代而相關(guān)程度沒有提升,即使沒有達(dá)到終止溫度也應(yīng)結(jié)束迭代,避免無意義的重復(fù)計(jì)算。 3)引入GPU：利用專用圖像處理核心處理器,實(shí)現(xiàn)并行處理。 通過上述算法優(yōu)化處理,算法的精確度和運(yùn)算效率都有大幅提高,進(jìn)一步優(yōu)化了模式精確控制和選擇方案。
[Abstract]:Space division multiplexing ( SDM ) in high speed optical fiber communication system is a new mode of optical fiber channel multiplexing .

In recent years , we can conclude that the design of mode conversion method based on spatial light modulator can be classified into two categories , namely optical waveguide type and spatial light path .

This paper first analyzes the research progress of this subject , analyzes the background of selection and the basis for choosing the topic . Then the paper introduces the basic theory knowledge involved in the subject , including two - dimensional Fourier transform correlation theory , spatial frequency spectrum , transfer function , Fourier transform property of lens , spatial light modulator correlation concept , etc . The paper combines the structure of optical Fourier transform and simulated annealing optimization technology to realize precise control and selection between modes . Finally , the paper puts forward some further optimization schemes , such as local annealing , graphic processor ( GPU ) and so on . The results show that the precise control and selection method of optical mode by using spatial light modulator in space division multiplexing is able to realize efficient and fast accurate conversion between arbitrary modes .

The research content and innovation points of this thesis are as follows :

1 . The simulation scheme of free transition between arbitrary modes based on optical Fourier system and spatial light modulator is proposed in this paper , and the realization process of MATLAB simulation of the scheme is recorded in detail .

On the basis of the Fourier transform property of the lens , the field distribution and the target pattern on the left side of the spatial light modulator via the lens 1 can be deduced . The expression of the ideal inter - mode transfer function is to divide the light field distribution on the right side and the left side of the spatial light modulator .

2 . The precise mode switching control and selection method based on computer simulation optimization algorithm are proposed .

In this paper , we propose a computer simulation optimization algorithm - simulated annealing algorithm to carry out random point - by - point phase change of the transfer function between modes . So how to adjust the phase information to achieve more accurate arbitrary mode conversion is a key problem in this paper .

3 . In this paper , the realization effect of the precise mode conversion scheme is analyzed , and the efficiency and accuracy of the conversion scheme are improved by means of local annealing , changing the termination condition , adding the GPU and the like .

1 ) local annealing is used instead of global annealing : according to the ideal spot size , the calculation range is reduced to a small area starting from the center of the light spot , the operation consumption of the non - practical significance area is avoided , the change range of the phase map of the transfer function is also modified accordingly , and the operation time can be effectively shortened .

2 ) self - adaptive annealing termination condition : the annealing termination condition is self - adaptive processing according to the mode and the annealing effect , and when the correlation degree is not improved after multiple iterations , the iteration can be finished even if the termination temperature is not reached , and the meaningless repeat calculation is avoided .

and 3 ) introducing a GPU : utilizing a special image processing core processor to realize parallel processing .

Through the optimization of the algorithm , the accuracy and the operation efficiency of the algorithm are greatly improved , and the mode precise control and selection scheme is further optimized .

【學(xué)位授予單位】：北京郵電大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN929.11

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相關(guān)期刊論文 前2條

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2 王永強(qiáng);劉太剛;;空間光調(diào)制器簡介及其應(yīng)用[J];焦作大學(xué)學(xué)報(bào);2007年03期

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本文編號(hào)：1758905