光纤传像系统中的耦合技术研究

由于柔软传像束光纤优良的传像特性和可以任意弯曲的特殊性能,因而使其被广泛地应用于医学、工业用显微镜,及科研、航天、军事等多种场合中,光纤束在成像系统中的精密耦合又是其中的重点.在总结了光纤束的传像特性及其应用背景的基础上,从数值孔径匹配的角度对异型光纤束的前后端耦合进行了一组优化设计,并给出了在可见光波段的实验图片及结果分析.     

异型石英光纤传像束光学性能分析

讨论了异型石英光纤传像束作为光学成像探测器的重要意义，利用排丝叠片法制备了一种线面转换异型石英光纤传像束，并利用测试平台进行了透过率和串像率测试。该光纤传像束在450～850 nm波段的透过率为40%～60%,串像率为4%。通过实验研究和数据分析，明确了制备过程中提高传像束性能的有效方法，确定了一套排丝叠片制备光纤传像束的工艺和流程，这对光纤传像束产品的广泛应用具有一定指导意义。     

提高光纤成像系统传像质量的研究方法

针对提高超长异型光纤传像束系统的传像质量,提出一种研究方法,综合分析了光纤的排列、光纤填充系数、数值孔径以及后续图像合成算法.制造光纤时光纤束采用六角形的排列.使用折射率小的包层.在图像数据处理时,使用抽样定理、三次样条图像信号重建和亚像元配准等图像处理算法,最终提高了光纤成像系统的传像质量.实验证明,通过信号的重建以及错位的校正等方法,能够有效地改善成像光纤束的传像质量.     

光纤传像束的传光特性表征

本文分析了光纤传像束的传光特性，提出了采用单根光纤的光透射率予以表征。     

高分辨率光纤传像束的制备及其光学性能

从酸溶法光纤传像束所需原料的配方确定开始,合理设计了纤芯玻璃、包层玻璃和酸溶玻璃三种材料之间物化性能的匹配性.这三种玻璃材料的物化性能将直接影响到所制备的高分辨率光纤传像束的成像质量.通过开展酸的浓度、温度、酸的种类以及酸溶时间等量化关系研究,确定了最适合光纤传像束酸溶的一系列工艺参数,这对于降低传像束的断丝率,提高光纤传像束的成像质量有较大作用.通过大量的实验研究、性能测试和理论分析,确定了多种提高传像束光学性能的有效方法,为光纤传像束的广泛应用奠定了良好的基础.     

光纤传像束断丝率的自动检测

介绍了光纤传像束在试验鉴定中断丝率指标的自动检测方法.将一束均匀的平行白光注入光纤传像束输入端,在输出端成像于高分辨率数码相机的CCD面阵上,采集的检测图像传输到计算机中.利用图像预处理和模糊平均方法,通过自适应阈值比较,标识出光纤传像束断丝像点的大体位置,然后以最短欧氏距离为判据,采用系统聚类法对断丝像点进行聚类和识别,统计出断丝数和断丝率.此图像处理算法可以克服传像束胶缝暗纹的干扰,具有计算量小,可靠性高的优点,能够快速地对光纤传像束进行质量评估和综合鉴定.     

光纤传像束研究进展

光纤传像束是一种可任意弯曲的传输图像的无源器件,与传统的光学成像器件相比,它具有重量轻、使用自由度大、易实现复杂空间结构的图像传递等优点。由于其优良的传像特性和可任意弯曲的特殊性能,使其被广泛地应用于医学、工业及科研、航天、军事等多种领域。本文给出了光纤传像束与其它成像系统相比所具有的优点,详细分析了影响光纤传像束传像性能的一些因素,介绍了传像束的制作方法,阐述了不同类型传像束的特点及应用,并指出了目前面临的问题。     

红外光纤传像系统像质优化方法研究

红外光纤传像系统在红外探测领域具有重要的学术价值和广阔的应用前景。文中采用理论分析与实验验证相结合的方法,对其像质优化问题进行研究。基于系统工作原理和特点,建立了其调制传递函数的理论模型,分析了影响其像质的主要因素。结果表明:为保证系统成像质量,前置物镜及后继耦接镜在系统Nyquist频率处的MTF值应大于0.8,且耦接镜所成光纤像与探测器像元的对准偏差应小于0.5像元。为进一步分析光纤传像束自身缺陷对像质影响,特搭建了成像实验装置,对两种不同规格光纤传像束推扫成像结果对比发现:通过使用合适后继耦接镜、多层光纤TDI模式成像、传像束前后端镀增透膜、准确的均匀性校正处理等方法,可有效改善系统的成像质量。以上研究为该类系统的研制提供了必要的技术储备。     

光纤传像束原理及其应用

光纤是现代通信网络的骨干,尤其是在大容量数据通信中.光纤作为传感器材料也得到了广泛应用,但却很少有人知道光纤还有一个特殊的作用,那就是传像.传像就是指将影像通过光纤直接传输,而中间不再经过类似于光通信那样的信号转换过程.本文阐述了光纤传像束的工作原理并着重介绍了光纤传像束在工业、医疗以及军事等方面的应用.     

基于辐射定标的某型红外光纤传像束双波段透过率测定

由于目前国内尚没有针对红外光纤传像束的波段透过率测试的规范标准和设备。提出了一种考虑光纤孔径角和光纤芯径的热像仪定标方法和某型光纤传像束的双波段透过率测试方法。通过在冷屏两端分别设置直径为8 mm和62 μm的两个光阑孔,确保定标条件和所测光纤的孔径角和光纤芯径相同;再通过在光路中插入波段滤光片来选择需要定标的波段。建立了基于最小二乘的红外热像仪定标模型,并采用该方法进行了定标实验。根据定标结果,测量了某型光纤传像束的红外光纤在2.0 μm～2.6 μm波段和3.4 μm～4.8 μm波段的透过率,其平均透过率大于70%。     

一种含同轴电缆的线束内部串扰高效分析方法

为了高效分析含同轴电缆的线束内部串扰,提出了一种新的简化电缆束模型的方法. 该方法把简化电缆束的过程分为两步:首先,为了解决同轴电缆编织屏蔽层难以仿真的问题,利用内外传输线转移矩阵简化同轴电缆,将含同轴电缆的电缆束转化为全由单芯线组成的三维电缆束模型;然后,使用等效线束法将全单芯线的电缆束进一步简化,减少需要分析的单芯线数量. 简化后的模型可用于任何三维电磁仿真软件中的电缆束内部串扰仿真分析,而无需考虑基于经典传输线理论的等效电路法的局限性. 将提出的方法与等效电路法分别应用于电缆束内部串扰的分析,两者的仿真结果一致性良好,说明文中提出的方法是准确可行的,能够实现含同轴电缆的线束内部串扰的高效分析.     

复式大截面光纤屏的实验研究

阐述了酸溶法光纤传像束的工艺原理及特点,并提出了用酸溶法光纤传像束复合成复式大截面光纤屏.针对发光管制做光纤屏点状结构明显,塑料光纤制做光纤屏易老化、不耐高温等缺点,采用了酸溶法拉制光纤传像束来制作光纤屏.该光纤屏具有分辨率高、成像好、耐老化等特点,有很好的观察视角,使用自由度大,易实现大截面、大范围传像.     

Delay and crosstalk reliability issues in mixed MWCNT bundle interconnects

Multi-walled carbon nanotube (MWCNT) bundles have potentially provided attractive solution in nanoscale VLSI interconnects. In current fabrication process, it is not trivial to grow a densely packed bundle having MWCNTs with similar number of shells. A realistic nanotube bundle, in fact, is a mixed CNT bundle consisting of MWCNTs of different diameters. This research paper presents an analytical model of mixed CNT bundle wherein MWCNTs having different number of shells are densely packed. Two different types of MWCNT bundles are presented: (1) MB that contains MWCNTs with similar number of shells (i.e., uniform diameters) and (2) MMB wherein MWCNTs having different number of shells (i.e., non-uniform diameters) are mixed. Multi-conductor transmission line theory is used to present an equivalent single-conductor (ESC) model of different MB and MMB configurations. Using the ESC model, performance is analyzed to address the effect of propagation delay, crosstalk and power dissipation that explores the reliability of an interconnect wire. It is observed that using an MMB arrangement, the overall reduction in delay and crosstalk are 15.33% and 29.59%, respectively, compared to the MB for almost similar power dissipation.     

一种分析线束串扰的等效方法

使用传统方法分析线束串扰存在内存消耗大、计算时间长的问题,研究其快速仿真技术有着重要的工程应用价值。提出了一种快速仿真线束串扰的"等效线束"方法,其基本思想是:除干扰线和受扰线外,剩余线缆(不论是属于线束的还是不属于线束的)按照线束的共模阻抗与线束端接阻抗相对大小进行分组,每一组用一根等效线缆表示,并保证等效线缆间不发生重叠。缩减后的多导体传输线串扰仿真模型,因等效线束的数目远少于实际线束中线缆的数目,从而能实现线束串扰的快速仿真。仿真结果表明该方法是合理可行的。     

线列光纤传像束的对比度调制传递函数

根据对比度传递函数的定义, 推导出线列光纤传像束对比度调制传递函数的表达式, 采用数值计算的方式, 仿真分析了线列光纤传像束的对比度调制传递函数。仿真结果表明, 输入信号与光纤束位相匹配对对比度调制传递函数结果有一定的影响, 对比度调制传递函数值随位相呈周期性变化。在输入的空间频率小于Nyquist 频率时, 对比度调制传递函数值随频率的增大而减小。     

Crosstalk Prediction of Single- and Double-Walled Carbon-Nanotube (SWCNT/DWCNT) Bundle Interconnects

The crosstalk effects in single- and double-walled carbon-nanotube (SWCNT and DWCNT) bundle-interconnect architectures are investigated in this paper. Some modified equivalent-circuit models are proposed for both SWCNT and DWCNT bundles, where capacitive couplings between adjacent bundles are incorporated. These circuit models are further used to predict the performance of SWCNT and DWCNT bundle interconnects in comparison with the Cu wire counterpart at all interconnect levels for advanced future technology generations. It is found that, compared with the SWCNT bundle, the DWCNT bundle interconnect can lead to a reduction of crosstalk-induced time delay, which will be more significant with increasing bundle length, while the peak voltage of the crosstalk-induced glitch in SWCNT and DWCNT bundle interconnects is in the same order as that of Cu wires. Due to the improvement in time delay, it is numerically confirmed that the DWCNT bundle interconnect will be more suitable for the next generation of interconnect technology as compared with the SWCNT bundle counterpart.      

环形铥光纤激光器中脉冲簇及其簇群的产生

本文研究了基于非线性偏振旋转锁模的铥光纤激光器中脉冲簇及脉冲簇群的产生.通过在环形腔内引人两段长度分别为100 m和350 m的SMF-28光纤来增强腔内非线性和色散,从而产生了脉宽为30～50 ns的束缚态脉冲簇.一个束缚态脉冲簇可以产生12个振幅不同但时间间隔相同的子脉冲.发现调节偏振控制器角度可以改变脉冲簇宽度以...     

Modeling of in-band crosstalk in WDM optical networks

In this paper, we analyze three different simulation models which allow the impact of in-band crosstalk on the transmission performances of wavelength division multiplexing (WDM) optical networks to be evaluated: an accurate simulation (AS), a Gaussian correlated noise (GCN) model, and a Gaussian white noise (GWN) model. In the AS, an interfering channel is generated at each node and added to the signal after an optical filtering. The final result must be averaged with respect to the message transmitted on the interfering channels and to the phases of the optical carriers. In the GCN the crosstalk term is modeled as a Gaussian correlated noise, whose spectrum coincides with that of the interfering channel. This model can be further simplified if the noise is also assumed uncorrelated (GWN approximation). The results obtained by these simulation models are also compared with those produced by an analytical model allowing to evaluate the in-band crosstalk penalty     

Extending transmission distance of high-density WDM systems usingpost transmitter fiber Raman amplifiers

The authors investigate the behavior of multichannel signals in a high-density wavelength division multiplexing (WDM) system with the consideration of stimulated Raman scattering. A parameter to evaluate the depth of Raman crosstalk is provided, and the transmission distance limitation imposed by Raman crosstalk is analyzed. To extend the system transmission distance, a post-transmitter fiber Raman amplifier is used. The allocation of signal channels on the pump gain profile is discussed. It is found that there exists an optimum pump power which results in a maximum amplifier gain. The example shows that the transmission distance limitation imposed by Raman crosstalk can be extended by 20 km for a 30-channel system with 0.25-dB/km fiber loss     

Tissue characterization of equine tendons with clinical B-scan images using a shock filter thinning algorithm

The fiber bundle density (FBD) calculated from ultrasound B-scan images of the equine superficial digital flexor tendon (SDFT) can serve as an objective measurement to characterize the three metacarpal sites of normal SDFTs, and also to discriminate a healthy SDFT from an injured one. In this paper, we propose a shock filter algorithm for the thinning of hyper-echoic structures observed in B-scan images of the SDFT. This algorithm is further enhanced by applying closing morphological operations on filtered images to facilitate extraction and quantification of fiber bundle fascicles. The mean FBD values were calculated from a clinical B-scan image dataset of eight normal and five injured SDFTs. The FBD values measured at three different tendon sites in normal cases show a highest density on the proximal site (five cases out of eight) and a lowest value on the distal part (seven cases out of eight). The mean FBD values measured on the entire tendon from the whole B-scan image dataset show a significant difference between normal and injured SDFTs: 51 (±9) for the normal SDFTs and 39 (±7) for the injured ones (p = 0.004) . This difference likely indicates disruption of some fiber fascicle bundles where lesions occurred. To conclude, the potential of this imaging technique is shown to be efficient for anatomical structural SDFT characterizations, and opens the way to clinically identifying the integrity of SDFTs.