單�！嗄９饫w合束器的傳輸特性研究
發(fā)布時間：2018-09-08 13:01
【摘要】：單模-多模光纖合束器,用于將多路單�；驕�(zhǔn)單模光纖激光輸出合束到一路多模光纖中,是全光纖非相干合成技術(shù)中的關(guān)鍵器件。目前,對于單模-多模光纖合束器的研究雖然取得了一定進(jìn)展,但是其中對于光場在合束器中的具體傳輸過程以及合束器設(shè)計規(guī)律等方面的研究仍非常有限。因此,本文針對套管法制作的單模-多模光纖合束器,以3×1單模-多模光纖合束器為例,從傳輸特性入手展開數(shù)值研究,分析光場在其中的傳輸過程,研究輸入、輸出光纖參數(shù)及拉錐參數(shù)對合束器性能的影響,給出單模-多模光纖合束器的設(shè)計規(guī)律。主要工作如下:首先,介紹了單根拉錐光纖的理論分析方法——幾何光學(xué)法和光束傳輸法。論文分別給出了兩種方法的理論思路和算法實現(xiàn),并結(jié)合單模-多模光纖合束器的特點和結(jié)構(gòu),分析對比了兩種方法的差異及適用范圍,指出研究單模-多模光纖合束器的傳輸特性需要使用光束傳輸法。其次,針對采用石英套管(折射率與包層折射率相等)拉制合束器的情況,建立了無限包層數(shù)值模型,研究了光場在合束器中的演化過程和規(guī)律,討論了合束器結(jié)構(gòu)及參數(shù)對傳輸效率的影響。結(jié)果表明,輸出光纖的數(shù)值孔徑對于傳輸效率的影響較小;輸出光纖的纖芯和拉錐長度應(yīng)該足夠大以保證傳輸效率。此外,需要匹配拉錐比和輸出光纖纖芯直徑,使輸出光纖纖芯盡可能小,以獲得較好的光束質(zhì)量輸出。最后,針對采用低折射率摻氟套管(折射率小于包層折射率)拉制合束器的情況,建立了有限包層數(shù)值模型,研究了有限包層及其他主要參數(shù)對合束器性能的影響。結(jié)果表明:第一,由于低折射率外部介質(zhì)的存在,使得有限包層在約束和分離光場中起到了重要作用,并提高了合束器的拉錐比和傳輸效率;第二,光場在輸入光纖包層中仍保持單模傳輸,使得在輸出光纖纖芯數(shù)值孔徑遠(yuǎn)小于熔融拉錐光纖束包層數(shù)值孔徑的情況下,合束器依然保持了高傳輸效率,因此可以通過減小輸出光纖纖芯數(shù)值孔徑的方式來提高輸出光亮度;第三,由于熔融拉錐光纖束中的損耗,合束器傳輸效率的提升存在一個極限值,該值隨拉錐比增大而減小;第四,拉錐長度應(yīng)足夠長以滿足絕熱拉錐條件,數(shù)值模擬結(jié)果顯示絕熱拉錐長度隨拉錐比增大而增大。此外,增大輸入光纖纖芯數(shù)值孔徑和纖芯包層比有利于提高合束器傳輸效率。以上結(jié)論對單模-多模光纖合束器的設(shè)計有著重要的指導(dǎo)意義。
[Abstract]:Single-mode and multi-mode fiber beam synthesizer is a key component in all optical fiber incoherent synthesis technology, which is used to output multiple single mode or quasi single mode fiber laser beam to a single mode fiber. At present, although some progress has been made in the study of single-mode and multi-mode optical fiber beam combiners, the research on the specific transmission process of light field in the beam combiner and the design rules of beam combiner are still very limited. Therefore, in this paper, for the single mode multimode fiber bundle combiner fabricated by casing method, taking 3 脳 1 single mode multimode fiber bundle combiner as an example, a numerical study is carried out from the transmission characteristics, the transmission process of the light field in it is analyzed and the input is studied. The influence of the output fiber parameters and the tapered parameters on the performance of the buncher is discussed. The design rule of the single-mode and multi-mode fiber bundle combiner is given. The main work is as follows: firstly, the theoretical analysis methods of single tapered fiber, geometric optics method and beam propagation method, are introduced. In this paper, the theoretical thinking and algorithm realization of the two methods are given, and the differences and application range of the two methods are analyzed and compared by combining the characteristics and structure of the single-mode and multi-mode fiber beam combiner. It is pointed out that the beam propagation method is needed to study the propagation characteristics of single-mode multimode optical fiber combiner. Secondly, an infinite cladding numerical model is established to study the evolution process and law of the light field in the beam combiner, aiming at the case that the quartz casing (the refractive index is equal to the cladding index) is used to fabricate the beam holder, and the infinite cladding numerical model is established. The influence of the structure and parameters of the beam combiner on the transmission efficiency is discussed. The results show that the numerical aperture of the output fiber has little effect on the transmission efficiency, and the core and tapered length of the output fiber should be large enough to ensure the transmission efficiency. In addition, it is necessary to match the tapered ratio and the diameter of the output fiber core to make the output fiber core as small as possible in order to obtain better beam quality output. Finally, a finite cladding numerical model is established to study the influence of the limited cladding and other main parameters on the performance of the beam binder by using a low refractive index fluoride-doped casing (refractive index less than the cladding index). The results show that: first, due to the existence of the external medium with low refractive index, the limited cladding plays an important role in restraining and separating the light field, and improves the tapered ratio and transmission efficiency of the beam combiner. The optical field still maintains a single mode transmission in the input fiber cladding, which makes the beam combiner maintain a high transmission efficiency when the output fiber core numerical aperture is much smaller than the melt tapered fiber cladding numerical aperture. Therefore, the output brightness can be improved by reducing the numerical aperture of the output fiber core. Thirdly, due to the loss in the fused tapered fiber bundle, there exists a limit value for the increase of the transmission efficiency of the beam combiner, which decreases with the increase of the tapered ratio. Fourthly, the tapered length should be long enough to satisfy the adiabatic cone condition. The numerical simulation results show that the adiabatic cone length increases with the increase of the tapered ratio. In addition, increasing the input fiber core numerical aperture and the core-cladding ratio can improve the transmission efficiency of the beam combiner. The above conclusions are of great significance to the design of single-mode-multi-mode fiber beam combiner.
【學(xué)位授予單位】：國防科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN253
本文編號：2230599
[Abstract]:Single-mode and multi-mode fiber beam synthesizer is a key component in all optical fiber incoherent synthesis technology, which is used to output multiple single mode or quasi single mode fiber laser beam to a single mode fiber. At present, although some progress has been made in the study of single-mode and multi-mode optical fiber beam combiners, the research on the specific transmission process of light field in the beam combiner and the design rules of beam combiner are still very limited. Therefore, in this paper, for the single mode multimode fiber bundle combiner fabricated by casing method, taking 3 脳 1 single mode multimode fiber bundle combiner as an example, a numerical study is carried out from the transmission characteristics, the transmission process of the light field in it is analyzed and the input is studied. The influence of the output fiber parameters and the tapered parameters on the performance of the buncher is discussed. The design rule of the single-mode and multi-mode fiber bundle combiner is given. The main work is as follows: firstly, the theoretical analysis methods of single tapered fiber, geometric optics method and beam propagation method, are introduced. In this paper, the theoretical thinking and algorithm realization of the two methods are given, and the differences and application range of the two methods are analyzed and compared by combining the characteristics and structure of the single-mode and multi-mode fiber beam combiner. It is pointed out that the beam propagation method is needed to study the propagation characteristics of single-mode multimode optical fiber combiner. Secondly, an infinite cladding numerical model is established to study the evolution process and law of the light field in the beam combiner, aiming at the case that the quartz casing (the refractive index is equal to the cladding index) is used to fabricate the beam holder, and the infinite cladding numerical model is established. The influence of the structure and parameters of the beam combiner on the transmission efficiency is discussed. The results show that the numerical aperture of the output fiber has little effect on the transmission efficiency, and the core and tapered length of the output fiber should be large enough to ensure the transmission efficiency. In addition, it is necessary to match the tapered ratio and the diameter of the output fiber core to make the output fiber core as small as possible in order to obtain better beam quality output. Finally, a finite cladding numerical model is established to study the influence of the limited cladding and other main parameters on the performance of the beam binder by using a low refractive index fluoride-doped casing (refractive index less than the cladding index). The results show that: first, due to the existence of the external medium with low refractive index, the limited cladding plays an important role in restraining and separating the light field, and improves the tapered ratio and transmission efficiency of the beam combiner. The optical field still maintains a single mode transmission in the input fiber cladding, which makes the beam combiner maintain a high transmission efficiency when the output fiber core numerical aperture is much smaller than the melt tapered fiber cladding numerical aperture. Therefore, the output brightness can be improved by reducing the numerical aperture of the output fiber core. Thirdly, due to the loss in the fused tapered fiber bundle, there exists a limit value for the increase of the transmission efficiency of the beam combiner, which decreases with the increase of the tapered ratio. Fourthly, the tapered length should be long enough to satisfy the adiabatic cone condition. The numerical simulation results show that the adiabatic cone length increases with the increase of the tapered ratio. In addition, increasing the input fiber core numerical aperture and the core-cladding ratio can improve the transmission efficiency of the beam combiner. The above conclusions are of great significance to the design of single-mode-multi-mode fiber beam combiner.
【學(xué)位授予單位】：國防科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN253
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