为实现大气温度全天时和高精度主动遥感探测,转动拉曼测温激光雷达的分光系统需要滤除强烈的背景光噪声,以及对Mie-Rayleigh散射提供70 d B以上的带外抑制率.本文提出了以可见光波段取样光纤布拉格光栅为核心的多级级联的特征光谱提取光...为实现大气温度全天时和高精度主动遥感探测,转动拉曼测温激光雷达的分光系统需要滤除强烈的背景光噪声,以及对Mie-Rayleigh散射提供70 d B以上的带外抑制率.本文提出了以可见光波段取样光纤布拉格光栅为核心的多级级联的特征光谱提取光路,构建高抑制率的全光纤拉曼测温分光系统,以实现大气温度的全天时和高精度探测.根据分光系统光路的传输特性,采用传输矩阵模型,优化设计了影响取样光纤布拉格光栅带外抑制率的主要因素(折射率调制深度、栅区总长度、取样周期和占空比),得到了优化的光谱分光系统参数.利用该分光系统可实现太阳背景光强度和Mie-Rayleigh散射信号强度分别比转动拉曼散射信号强度弱40 d B和50 d B,信噪比高于100时,白天探测高度可达1.6 km.该全光纤分光系统具有小型化、抗干扰和稳定性高的优点,可为陆基及星载拉曼测温激光雷达提供一种全新的解决方案.展开更多
One of the most basic characteristics of photonic crystal is frequency band gap. When defects are introduced into the periodic photonic crystal, a number of defect modes appear in the stop band.In this paper, we explo...One of the most basic characteristics of photonic crystal is frequency band gap. When defects are introduced into the periodic photonic crystal, a number of defect modes appear in the stop band.In this paper, we exploit transfer matrix method based on photonic crystal theory, and assume the sampled fiber Bragg grating as one-dimensional dual photonic crystal with a large size defect. Characteristics of the sampled fiber Bragg grating are analyzed. Experimental results show that the sampled fiber Bragg grating has many reflective peaks. Its reflectivity, center wavelength, reflective peak intervals and band width all change with the grating parameters, including grating length, duty ratio of the material with high dielectric constant, and index modulation depth and period. Results agree with the conventiona1 couple mode theory which can be used when analyzing other characteristics of the sampled fiber Bragg grating or applying it into practice.展开更多
Multi-π-phase-shifted fiber Bragg gratings and π-phase-shifted sampled fiber Bragg gratings(SFBGs) with dual wavelength filtering properties are compared.Results show that both of these gratings have the dual wavele...Multi-π-phase-shifted fiber Bragg gratings and π-phase-shifted sampled fiber Bragg gratings(SFBGs) with dual wavelength filtering properties are compared.Results show that both of these gratings have the dual wavelength reflective spectra.However,the side lobe of the reflective spectrum of π-phase-shifted SFBGs is lower than that of multi-π-phaseshifted gratings.By adjusting the duty cycle in the range of 0.66-0.80,the filtering properties of π-phase-shifted SFBGs are optimized,and the side lobe suppression ratio(SLSR) is the lowest when the duty cycle is 0.75.The application of the π-phase-shifted SFBGs in the dual-wavelength laser is also demonstrated.展开更多
文摘为实现大气温度全天时和高精度主动遥感探测,转动拉曼测温激光雷达的分光系统需要滤除强烈的背景光噪声,以及对Mie-Rayleigh散射提供70 d B以上的带外抑制率.本文提出了以可见光波段取样光纤布拉格光栅为核心的多级级联的特征光谱提取光路,构建高抑制率的全光纤拉曼测温分光系统,以实现大气温度的全天时和高精度探测.根据分光系统光路的传输特性,采用传输矩阵模型,优化设计了影响取样光纤布拉格光栅带外抑制率的主要因素(折射率调制深度、栅区总长度、取样周期和占空比),得到了优化的光谱分光系统参数.利用该分光系统可实现太阳背景光强度和Mie-Rayleigh散射信号强度分别比转动拉曼散射信号强度弱40 d B和50 d B,信噪比高于100时,白天探测高度可达1.6 km.该全光纤分光系统具有小型化、抗干扰和稳定性高的优点,可为陆基及星载拉曼测温激光雷达提供一种全新的解决方案.
文摘One of the most basic characteristics of photonic crystal is frequency band gap. When defects are introduced into the periodic photonic crystal, a number of defect modes appear in the stop band.In this paper, we exploit transfer matrix method based on photonic crystal theory, and assume the sampled fiber Bragg grating as one-dimensional dual photonic crystal with a large size defect. Characteristics of the sampled fiber Bragg grating are analyzed. Experimental results show that the sampled fiber Bragg grating has many reflective peaks. Its reflectivity, center wavelength, reflective peak intervals and band width all change with the grating parameters, including grating length, duty ratio of the material with high dielectric constant, and index modulation depth and period. Results agree with the conventiona1 couple mode theory which can be used when analyzing other characteristics of the sampled fiber Bragg grating or applying it into practice.
基金supported by the National Natural Science Foundation of China (No.60808004)the Fund of New Century Excellent Talents in University (No.NCET-07-0611)Tianjin Natural Science Foundation (No.08JCYBJC14500)
文摘Multi-π-phase-shifted fiber Bragg gratings and π-phase-shifted sampled fiber Bragg gratings(SFBGs) with dual wavelength filtering properties are compared.Results show that both of these gratings have the dual wavelength reflective spectra.However,the side lobe of the reflective spectrum of π-phase-shifted SFBGs is lower than that of multi-π-phaseshifted gratings.By adjusting the duty cycle in the range of 0.66-0.80,the filtering properties of π-phase-shifted SFBGs are optimized,and the side lobe suppression ratio(SLSR) is the lowest when the duty cycle is 0.75.The application of the π-phase-shifted SFBGs in the dual-wavelength laser is also demonstrated.
