薄包层光纤光栅理论及色散特性研究
发布时间：2018-10-13 19:47
【摘要】：本论文主要从以下三大部分进行阐述:光纤光栅传输理论分析、均匀光纤光栅传输特性分析以及基于两种介质模型的啁啾长周期光纤光栅色散特性的数值分析。作为色散补偿器件的一种,光纤光栅具有体积小、插入损耗低、色散补偿值大等多方面优点,而在当今光通信系统中应用最为广泛。通常,光纤可以看作三层介质圆柱形光波导,但由于三层光纤介质模型纤芯模与包层模本征方程以及场分布均比较复杂,在一般情况下,可以简化看作两层光纤介质模型来进行计算分析。但是在光纤的包层很薄,即包层半径较小时,利用两层、三层这两种光纤介质模型的本征方程计算所得的纤芯模有效折射率会有较大差别。本文主要以光纤光栅的耦合模理论和传输矩阵法为主要理论,结合两种光纤介质模型的本征方程所得纤芯模有效折射率的差别,对薄包层光纤光栅的传输与色散特性进行仿真分析。本文的主要研究内容包括:(1)为了更加准确研究薄包层光纤光栅的传输特性,本文基于单轴晶体光纤的两层介质模型与三层介质模型所得纤芯模有效折射率的差别,首先分别对基于两种介质模型的薄包层布拉格光纤光栅FBG的中心波长、带宽的差别进行仿真分析,后又仿真分析了基于两种介质模型的薄包层长周期光纤光栅LPFG的中心波长、带宽的差别。并根据所得数据,分别仿真了FBG和LPFG的透射谱、时延以及色散。结果表明:对于薄包层光纤,两层、三层光纤介质模型的中心波长和带宽有较大差别,并且包层半径越小,差别越大。并仿真分析光栅的长度以及折射率调制深度等参数对传输与色散性能的影响。发现光栅的长度越长、折射率调制深度越小,均有利于增大其色散补偿能力。(2)为了进一步研究两种介质模型薄包层光纤光栅的色散性能,本文对基于两种介质模型的啁啾长周期光纤光栅CLPFG色散进行了数值分析。首先分析比较了低阶模式下,光纤光栅包层半径与包层模序数对两种介质模型色散的影响。发现包层模序相同时,包层半径越大,其色散值越小;包层半径相同时,包层模序越大,其色散值越大。在相同的包层半径与包层模序时,两层光纤介质模型的色散值始终略高于三层光纤介质模型。其次利用分段均匀的传输矩阵法分别仿真分析啁啾系数和折射率调制深度对CLPFG传输谱、时延以及色散性能的影响。研究发现,在一定条件下,适当降低啁啾系数与折射率调制深度均可提高啁啾长周期光纤光栅的色散补偿性能。
[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.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN253
本文编号：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.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN253
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，本文编号：2269709
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