薄包層光纖光柵理論及色散特性研究
發(fā)布時(shí)間：2018-10-13 19:47
【摘要】：本論文主要從以下三大部分進(jìn)行闡述:光纖光柵傳輸理論分析、均勻光纖光柵傳輸特性分析以及基于兩種介質(zhì)模型的啁啾長周期光纖光柵色散特性的數(shù)值分析。作為色散補(bǔ)償器件的一種,光纖光柵具有體積小、插入損耗低、色散補(bǔ)償值大等多方面優(yōu)點(diǎn),而在當(dāng)今光通信系統(tǒng)中應(yīng)用最為廣泛。通常,光纖可以看作三層介質(zhì)圓柱形光波導(dǎo),但由于三層光纖介質(zhì)模型纖芯模與包層模本征方程以及場分布均比較復(fù)雜,在一般情況下,可以簡化看作兩層光纖介質(zhì)模型來進(jìn)行計(jì)算分析。但是在光纖的包層很薄,即包層半徑較小時(shí),利用兩層、三層這兩種光纖介質(zhì)模型的本征方程計(jì)算所得的纖芯模有效折射率會(huì)有較大差別。本文主要以光纖光柵的耦合模理論和傳輸矩陣法為主要理論,結(jié)合兩種光纖介質(zhì)模型的本征方程所得纖芯模有效折射率的差別,對薄包層光纖光柵的傳輸與色散特性進(jìn)行仿真分析。本文的主要研究內(nèi)容包括:(1)為了更加準(zhǔn)確研究薄包層光纖光柵的傳輸特性,本文基于單軸晶體光纖的兩層介質(zhì)模型與三層介質(zhì)模型所得纖芯模有效折射率的差別,首先分別對基于兩種介質(zhì)模型的薄包層布拉格光纖光柵FBG的中心波長、帶寬的差別進(jìn)行仿真分析,后又仿真分析了基于兩種介質(zhì)模型的薄包層長周期光纖光柵LPFG的中心波長、帶寬的差別。并根據(jù)所得數(shù)據(jù),分別仿真了FBG和LPFG的透射譜、時(shí)延以及色散。結(jié)果表明:對于薄包層光纖,兩層、三層光纖介質(zhì)模型的中心波長和帶寬有較大差別,并且包層半徑越小,差別越大。并仿真分析光柵的長度以及折射率調(diào)制深度等參數(shù)對傳輸與色散性能的影響。發(fā)現(xiàn)光柵的長度越長、折射率調(diào)制深度越小,均有利于增大其色散補(bǔ)償能力。(2)為了進(jìn)一步研究兩種介質(zhì)模型薄包層光纖光柵的色散性能,本文對基于兩種介質(zhì)模型的啁啾長周期光纖光柵CLPFG色散進(jìn)行了數(shù)值分析。首先分析比較了低階模式下,光纖光柵包層半徑與包層模序數(shù)對兩種介質(zhì)模型色散的影響。發(fā)現(xiàn)包層模序相同時(shí),包層半徑越大,其色散值越小;包層半徑相同時(shí),包層模序越大,其色散值越大。在相同的包層半徑與包層模序時(shí),兩層光纖介質(zhì)模型的色散值始終略高于三層光纖介質(zhì)模型。其次利用分段均勻的傳輸矩陣法分別仿真分析啁啾系數(shù)和折射率調(diào)制深度對CLPFG傳輸譜、時(shí)延以及色散性能的影響。研究發(fā)現(xiàn),在一定條件下,適當(dāng)降低啁啾系數(shù)與折射率調(diào)制深度均可提高啁啾長周期光纖光柵的色散補(bǔ)償性能。
[Abstract]:In this paper, the transmission theory of fiber grating, the transmission characteristics of uniform fiber grating and the dispersion characteristics of chirped long-period fiber grating based on two kinds of dielectric models are analyzed. As a kind of dispersion compensation device, fiber grating has many advantages, such as small volume, low insertion loss, large dispersion compensation value and so on, but it is widely used in optical communication systems. Generally speaking, the fiber can be regarded as a cylindrical optical waveguide with three layers of dielectric. However, due to the complexity of the intrinsic equations and the field distribution of the core mode and the cladding mode of the three-layer fiber dielectric model, in general cases, It can be simplified as a two-layer fiber medium model for calculation and analysis. However, when the cladding of fiber is very thin, that is, the cladding radius is small, the effective refractive index of the core mode calculated by using the eigenequations of the two kinds of optical fiber media models is quite different. In this paper, the coupling mode theory of fiber grating and the transfer matrix method are taken as the main theories, and the difference of the effective refractive index of the core mode is obtained by combining the intrinsic equations of the two kinds of fiber media models. The transmission and dispersion characteristics of thin clad fiber gratings are simulated and analyzed. The main contents of this paper are as follows: (1) in order to study the propagation characteristics of thin cladding fiber grating more accurately, the difference of effective refractive index of core mode based on the two-layer dielectric model and three-layer dielectric model of uniaxial crystal fiber is presented in this paper. The central wavelength and bandwidth difference of thin cladding fiber Bragg grating (FBG) based on two kinds of dielectric models are simulated and analyzed, and then the center wavelength of thin cladding long-period fiber grating (LPFG) based on two kinds of dielectric models is simulated and analyzed. The difference in bandwidth. According to the obtained data, the transmission spectrum, delay and dispersion of FBG and LPFG are simulated respectively. The results show that for thin cladding fiber, the central wavelength and bandwidth of the two and three layers fiber dielectric model are different, and the smaller the cladding radius is, the greater the difference is. The effects of the grating length and refractive index modulation depth on the transmission and dispersion performance are analyzed by simulation. It is found that the longer the grating length, the smaller the refractive index modulation depth, which is beneficial to increase the dispersion compensation ability. (2) in order to further study the dispersion performance of the two kinds of dielectric model thin cladding fiber grating, In this paper, the CLPFG dispersion of chirped long-period fiber gratings based on two dielectric models is numerically analyzed. The influence of cladding radius and number of cladding modes on dispersion of the two dielectric models in low-order mode is analyzed and compared. It is found that the larger the cladding radius is, the smaller the dispersion value is when the cladding mode order is the same, and the larger the cladding mode sequence is, the greater the dispersion value is. At the same cladding radius and cladding mode sequence, the dispersion value of the two-layer fiber dielectric model is always slightly higher than that of the three-layer fiber dielectric model. Secondly, the effects of chirp coefficient and refractive index modulation depth on the transmission spectrum, delay and dispersion of CLPFG are simulated by the piecewise uniform transmission matrix method. It is found that the dispersion compensation performance of the chirped long-period fiber grating can be improved by decreasing the chirp coefficient and the refractive index modulation depth under certain conditions.
【學(xué)位授予單位】：天津理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN253
本文編號(hào)：2269709
[Abstract]:In this paper, the transmission theory of fiber grating, the transmission characteristics of uniform fiber grating and the dispersion characteristics of chirped long-period fiber grating based on two kinds of dielectric models are analyzed. As a kind of dispersion compensation device, fiber grating has many advantages, such as small volume, low insertion loss, large dispersion compensation value and so on, but it is widely used in optical communication systems. Generally speaking, the fiber can be regarded as a cylindrical optical waveguide with three layers of dielectric. However, due to the complexity of the intrinsic equations and the field distribution of the core mode and the cladding mode of the three-layer fiber dielectric model, in general cases, It can be simplified as a two-layer fiber medium model for calculation and analysis. However, when the cladding of fiber is very thin, that is, the cladding radius is small, the effective refractive index of the core mode calculated by using the eigenequations of the two kinds of optical fiber media models is quite different. In this paper, the coupling mode theory of fiber grating and the transfer matrix method are taken as the main theories, and the difference of the effective refractive index of the core mode is obtained by combining the intrinsic equations of the two kinds of fiber media models. The transmission and dispersion characteristics of thin clad fiber gratings are simulated and analyzed. The main contents of this paper are as follows: (1) in order to study the propagation characteristics of thin cladding fiber grating more accurately, the difference of effective refractive index of core mode based on the two-layer dielectric model and three-layer dielectric model of uniaxial crystal fiber is presented in this paper. The central wavelength and bandwidth difference of thin cladding fiber Bragg grating (FBG) based on two kinds of dielectric models are simulated and analyzed, and then the center wavelength of thin cladding long-period fiber grating (LPFG) based on two kinds of dielectric models is simulated and analyzed. The difference in bandwidth. According to the obtained data, the transmission spectrum, delay and dispersion of FBG and LPFG are simulated respectively. The results show that for thin cladding fiber, the central wavelength and bandwidth of the two and three layers fiber dielectric model are different, and the smaller the cladding radius is, the greater the difference is. The effects of the grating length and refractive index modulation depth on the transmission and dispersion performance are analyzed by simulation. It is found that the longer the grating length, the smaller the refractive index modulation depth, which is beneficial to increase the dispersion compensation ability. (2) in order to further study the dispersion performance of the two kinds of dielectric model thin cladding fiber grating, In this paper, the CLPFG dispersion of chirped long-period fiber gratings based on two dielectric models is numerically analyzed. The influence of cladding radius and number of cladding modes on dispersion of the two dielectric models in low-order mode is analyzed and compared. It is found that the larger the cladding radius is, the smaller the dispersion value is when the cladding mode order is the same, and the larger the cladding mode sequence is, the greater the dispersion value is. At the same cladding radius and cladding mode sequence, the dispersion value of the two-layer fiber dielectric model is always slightly higher than that of the three-layer fiber dielectric model. Secondly, the effects of chirp coefficient and refractive index modulation depth on the transmission spectrum, delay and dispersion of CLPFG are simulated by the piecewise uniform transmission matrix method. It is found that the dispersion compensation performance of the chirped long-period fiber grating can be improved by decreasing the chirp coefficient and the refractive index modulation depth under certain conditions.
【學(xué)位授予單位】：天津理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN253
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