Performance of CO-OFDM system with RS-Turbo concatenated code

In this paper, the RS-Turbo concatenated code is applied to coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. RS(186,166,8) and Turbo code with code rate of 1/2 are employed for RS-Turbo concatenated code. Two decoding algorithms, which are Max-Log-MAP algorithm and Log-MAP algorithm, are adopted for Turbo decoding, and the iteration Berlekamp-Massey (BM) algorithm is adopted for RS decoding. The simulation results show that the bit error rate (BER) performance of CO-OFDM system with RS-Turbo concatenated code is significantly improved at high optical signal to noise ratio (OSNR), and the iteration number is reduced compared with that of the Turbo coded system. Furthermore, when the Max-Log-MAP algorithm is adopted for Turbo decoding, the transmission distance of CO-OFDM system with RS-Turbo concatenated code can reach about 400 km without error, while that of the Turbo coded system can only reach about 240 km when BER is lower than 10-4 order of magnitude.     

基于多模光纤偏振烧孔效应的双波长掺铒光纤激光器

基于多模光纤(MMF)引入的偏振烧孔(PHB)效应,研制了一种环形双波长掺铒光纤(EDF)激光器.单模光纤(SMF)-MMF-SMF组成的结构使MMF不同偏振方向的反射模在波长上分开,利用PHB效应实现双波长的输出,输出波长间隔可通过改变MMF的长度改变.实验对比了1.6 m和3.0 m长的MMF输出波谱特性,结果表明...     

Study on the sensing characteristics of a local micro-structured long period fiber grating

A simple and effective method employing a local micro-structured long period fiber grating （LMS-LPFG） for the simultaneous measurement of temperature and refractive index is proposed and investigated experimentally. The LMS-LPFG is formed by using the partial etching technique with hydrofluoric （HF） acid in a standard LPFG, in which there are discontinuities in the effective refractive index of cladding modes. Similar to the phase shift theory, a narrow passband and two stopbands are formed. The temperature and the surrounding refractive index （SRI） characteristics of the two stopbands and passband are studied. The temperature sensitivities of the two stopbands and passband are 0.05 nm/℃ approximately. The SRI sensitivity ofpassband （-61.56 nm/RIU） is bigger than that of the two stopbands （-35.62 nm/RIU）. Thus, with the sensitive matrix, we can simultaneously measure the changes of temperature and refractive index.     

某训练基地骨密度与饮用水硬度关系的研究

对我部驻甘肃集训练基地某站干部、战士、志愿兵及家属１０６人进行了骨密度调查。调查采用单光子骨矿分析仪，对尺、桡骨的骨密度进行测定。结果表明，骨密度良好者占 ６５．１％，与对照组 １０．１％相比，有非常显著性差异（Ｐ＜０．０１）。经调查，该地区饮用水硬度明显偏高，说明饮用水中钙含量与骨密度有直接关系。     

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.     

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。     

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.     

原子吸收法测定糖尿病人血清中微量元素

糖尿病是我国发病率较高的疾病之一,并主要通过其并发症威胁人类。测定糖尿病及其并发症血清中的微量元素,可为研究糖尿病发病机理、预防和诊治糖尿病提供依据。用常规的火焰原子吸收法,测定多个元素时所需样品量大,样品不易获得,而且测定过程中管路容易被堵塞。本文测定过程中结合使用微量脉冲进样法,测定了29例糖尿病病人和26例糖尿病并发症病人血清中的钙、镁、锌、铜、铁,并和28例健康人血清中相应元素进行了比较。方法简便、可靠,所需样品量小,可满足生物样品测定的实际要求。     

新型光纤光栅加速度传感器的设计与实现

利用光纤光栅作为基本传感元件，设计制作了一种基于悬臂梁结构的新型光纤光栅加速度传感器。测量范围＋／-10g，灵敏度10mg，测量频率小于100Hz。与光纤加速度传感器相比，光纤光栅加速度传感器具有更高的稳定性及抗干扰能力。并且由于光纤光栅本身的波分复用的特性，可以很方便地构成加速度传感网络进行测量。     

偏二甲肼动态配气系统稳定性研究

采用分光光度法研究了偏二甲肼动态配气系统的稳定性。实验结果表明,在环境温度、载气温度和流量恒定的情况下,该动态系统可稳定地输出0～100mg/m~3的偏二甲肼标准气体,可用于肼类推进剂监测仪器的标定与校验;该配气系统还可用于制备用静态法难以配制其它极性化合物标准气体。