A microwave photonic filter based on multi-wavelength fiber laser and infinite impulse response

A microwave photonic filter (MPF) based on multi-wavelength fiber laser and infinite impulse response (IIR) is proposed. The filter uses a multi-wavelength fiber laser as the light source, two sections of polarization maintaining fiber (PMF) and three polarization controllers (PCs) as the laser frequency selection device. By adjusting the PC to change the effective length of the PMF, the laser can obtain three wavelength spacings, which are 0.44 nm, 0.78 nm and 1.08 nm, respectively. And the corresponding free spectral ranges (FSRs) are 8.46 GHz, 4.66 GHz and 3.44 GHz, respectively. Thus changing the wavelength spacing of the laser can make the FSR variable. An IIR filter is introduced based on a finite impulse response (FIR) filter. Then the 3-dB bandwidth of the MPF is reduced, and the main side-lobe suppression ratio (MSSR) is increased. By adjusting the gain of the radio frequency (RF) signal amplifier, the frequency response of the filter can be enhanced.     

Tunable and switchable dual-wavelength erbium-doped fiber laser based on in-line tapered fiber filters

A tunable and switchable dual-wavelength erbium-doped fiber laser(EDFL) based on all-fiber single-mode tapered fiber structure has been demonstrated. By adjusting the variable optical attenuator(VOA), the laser can be switched between the single-wavelength mode and the dual-wavelength mode. When the temperature applied on the tapered fiber structure varies, the pass-band varies and the wavelength of the output laser shifts correspondingly. When the temperature changes from 30 °C to 180 °C, the central wavelength of the EDFL generated by branch A shifts from 1 550.7 nm to 1 560.3 nm, while that of branch B shifts from 1 530.8 nm to 1 540.4 nm, indicating the wavelength interval is tunable. These advantages enable this laser to be a potential candidate for high-capacity wavelength division multiplexing systems and mechanical sensors.     

便携式NO2检测报警仪的研制

研制了能满足航天发射场推进剂泄漏检测需要的便携式NO2检测报警仪。仪器采用电化学原理,量程范围为1～500×10^-6（V／V）,分辨率为1×10^-6（V／V）,响应时间小于30s,使用寿命为2年。仪器体积小巧,操作方便,可随身佩戴。当火箭推进剂作业环境中NO2气体的浓度超限时,仪器可自动报警,便于作业人员尽早采取科学的安全防护措施,防止事故发生。     

肼类推进剂渗透管研制过程中的影响因素

肼类推进剂渗透管是用来为自行研制的肼类推进剂标准气体发生装置提供准确、稳定、连续的标准气源,通过二级稀释可以制备不同浓度的标准气体用于肼类传感器校准或实验.但是由于肼类燃料强吸附性、强腐蚀性、易在空气中氧化分解等劣性性质,常规渗透管法无法满足其特性要求.为此,笔者在常规制备方法的基础上予以改进,成功研制渗透率范围宽且均匀性稳定性满足规范要求的肼类推进剂渗透管,本文就研制过程中影响渗透率值的主要因素进行了较为详细的阐述.     

分数阶不确定奇异系统的镇定

研究阶数0α1的分数阶不确定奇异系统的鲁棒镇定问题.利用矩阵奇异值分解和线性矩阵不等式方法提出新的基于观测器的鲁棒状态反馈镇定的充分条件,同时给出该条件下观测器和状态反馈控制器的具体求解方法.最后通过数值例子验证该方法的有效性.     

动臂式贴片机贴装轨迹的可视化仿真

贴片机是电子制造业中最重要的生产设备,针对贴片机试贴过程资源浪费大、成本高、效率低的问题,开发了一种模拟贴片机贴装轨迹的可视化仿真系统。在分析研究贴片机结构与贴装工艺流程的基础上,结合使用外部模型导入与OpenGL绘图两种方式,构造了复杂的贴片机模型以及参数化原件模型库,并在用VC++开发的人机界面下由数据库提供贴装参数,OpenGL函数显示控制模型运动,实现了贴片机贴装过程在计算机虚拟环境下的可视化仿真,从而提高了贴片机程序的可视化程度,降低试贴成本。     

基于多模-单模-多模结构和光纤布拉格光栅同时测量温度和折射率

利用单模光纤(SMF)中的包层模与纤芯导模之间的干涉,提出了一种基于多模-单模-多模(MSM)结构与布拉格光栅(FBG)级联可同时测量温度和折射率的传感器.基于MSM结构的干涉谱和FBG的透射峰对温度和折射率具有不同响应灵敏度的特点,利用敏感矩阵实现了对温度和折射率的同时测量.实验测得MSM结构和FBG的温度灵敏度分别为0.055 2 nm/℃和0.015 8 nm/℃,MSM结构的折射率灵敏度为109.702 nm/RIU,而FBG对折射率变化不敏感.温度和折射率的测量精度分别为士0.32℃和士0.002 3.实验显示提出的MSM结构的温度灵敏度比单模-多模-单模(SMS)结构传感器提高了5倍,同时由于SMF中的包层模对外界环境的变化较敏感,该MSM结构也可应用于其他传感领域.     

Highly birefringent photonic crystal fibers with flattened dispersion and low confinement loss

A highly birefringent index-guiding photonic crystal fiber (PCF) with flattened dispersion and low confinement loss is proposed by introducing two small air holes with the same diameter in the core area. The fundamental mode field, birefringence, confinement loss, effective mode area and dispersion characteristic of the fibers are studied by the full-vector finite element method (FEM). Simulation results show that a high birefringence with the order of 10 -3 and a low confinement loss of 0.001 dB/km are obtained at 1550 nm. Furthermore, flattened chromatic dispersion from 1450 nm to 1590 nm is obtained.     

厚度对室温沉积ZnO:Al薄膜光电特性的影响

利用直流磁控溅射法, 在室温玻璃衬底上制备了具有良好附着性的多晶ZnO∶ Al(ZAO)薄膜. 比较了室温下获得的薄膜与衬底加热条件下所得薄膜的结晶程度, 研究了厚度对室温条件下制备的ZAO薄膜表面形貌、电学性能及紫外-可见-近红外光区透光性的影响. 结果表明, 室温条件下制备的ZAO薄膜也具有(002)面择优取向, 随着膜厚的增加薄膜晶粒化程度提高, 载流子浓度和迁移率增大, 电阻率下降, 薄膜在紫外光区的吸收边发生红移, 在可见光区的平均透过率降低, 在近红外光区的透过率随厚度的增加而减小. 厚度为1200 nm的ZAO薄膜具有最佳光电综合性能, 其电阻率为7.315×10~(-4) Ω·cm, 方块电阻为6.1 Ω/□, 可见光区平均透过率达到82%, 波长为550 nm处的透过率为87%.     

基于多模干涉和长周期光纤光栅的温度及折射率同时测量

基于多模干涉理论和长周期光纤光栅(LPFG)的传感特性,提出了一种单模-多模-单模(SMS)结构与LPFG级联的光纤传感器,实现了温度和折射率的同时测量。实验结果表明,SMS结构的干涉谱和LPFG对温度和折射率具有不同响应灵敏度,其温度灵敏度分别为0.017nm/℃和0.060nm/℃;SMS结构对折射率不敏感,而LPFG的折射率灵敏度为-35.60nm/RIU(RIU为折射率单位)。因此利用敏感矩阵,实现对温度和折射率的同时测量,得到温度和折射率的最大测量误差分别为±0.59℃和±0.0013。该结构灵敏度高、结构简单,且不易受电磁等干扰。实验结果具有良好的线性度,在生物化学领域应用前景良好。