热循环加载条件下焊点形态参数对板级光互连模块对准偏移影响分析

建立光互连模块有限元分析模型并进行热循环加载有限元分析,获取了垂直腔面发射激光器(Vertical Cavity Surface Emitting Laser,VCSEL)与耦合元件间的位置偏移;采用正交实验设计法设计了不同焊点结构参数组合并建立有限元模型,计算相应焊点形态参数组合下的位置偏移数据并进行方差分析.结果表明:在一个热循环周期内低温保温结束时刻位置偏移最大;外端光通道的位置偏移比中间光通道的偏移值大;在置信度为95%时VCSEL焊点高度对对准偏移具有显著影响,因素显著性排序由大到小依次为:VCSEL焊点高度、陶瓷基板焊点高度、VCSEL焊点体积和陶瓷基板焊点体积;单因子变量分析表明,位置偏移随VCSEL焊点高度增加而增大.     

同轴型激光器焊后偏移的理论与实验研究

为了研究同轴型激光器激光焊接产生的焊后偏移(PWS),采用基于有限元热-结构耦合理论的分析方法,建立了同轴型激光器3束激光焊接模型,分析了激光焊接工艺参量对焊后偏移的影响规律,并进行了激光锤校正实验研究,获得了同轴型激光器激光焊接前后及校正后的耦合光功率值。结果表明,同轴型激光器的焊后偏移受到3个焊点功率分布和位置分布等因素的影响;耦合光功率在激光锤校正后整体呈上升趋势,最大耦合光功率可恢复至94%,有限元仿真分析对PWS的方向预测合理。这一结果对激光焊接同轴型激光器的生产具有一定的指导意义。     

用于VCSEL与光纤对准的新型集成微光学系统

半导体激光器与光纤耦合封装模块是光网络中最重要和关键的元器件之一。文章介绍了用于VCSEL与光纤对准的一种新型集成微光学系统。该微光学系统用于控制VCSEL光束方向相当有效,能极大提高耦合效率,而且具有很好的对准重复性。它采用MEMS和光电子学封装技术,可用于目前低成本的耦合模块。     

瞬态温度变化对大口径光学元件的影响

温度瞬变是影响惯性约束聚变(ICF)驱动器中大口径光学元件结构稳定性的一个重要的激励因素.采用多通道高精度温度监测仪对原型装置中编组站大口径光学元件环境温度进行了24 h监测,得到了编组站光学元件环境温度24 h温度变化曲线;采用有限元分析软件建立了光学元件的有限元模型,把温度监测结果作为载荷,对光学元件进行了热结构耦合分析.分析得到了大口径光学元件面形在24 h内的变化曲线,光学元件环境温度24 h内最大变化范围为0.45 ℃,24 h光学元件最大转角变化为1.12 μrad.分析结果表明,光学元件转角最大变化已超过打靶对光学元件稳定性的要求,但通过调整打靶时间,缩短光路准直之后打靶的等待时间可有效提高打靶的成功率.     

基于MPLC提高空间光-单模光纤耦合效率技术研究

在空间激光通信实际应用过程中，受到对准误差的影响，单模光纤耦合效率低，需要对其进行精确校正。在理想条件下，首先分析不存在对准误差及其他影响因素时平面波-单模光纤耦合效率及高斯光-单模光纤耦合效率模型，然后分别研究了光纤横向偏移和纵向偏移两种对准误差对单模光纤耦合效率的影响。在此基础上，提出了一种基于多平面光转换（MPLC）技术提高单模光纤耦合效率的方法，数值仿真了使用MPLC将平面波转化为高斯光前后及校正对准误差前后耦合效率的变化情况。仿真结果表明：使用MPLC将平面波转换为与高斯光高度相似的光束后，耦合效率会比平面波直接耦合进入单模光纤提高18.54%；使用MPLC分别校正横向偏移和纵向偏移后，耦合效率均提升至99%以上。该方法突破了空间光与单模光模式不匹配的限制，可以有效校正对准偏移误差，对于提高空间光到单模光纤的耦合效率具有一定的理论意义。     

30Gbit/s并行光发射模块制作过程中的光耦合及封装

介绍了并行光发射模块制作过程中,垂直腔面发射激光器列阵与列阵光纤的对准及固定方法.对斜面光纤折弯耦合和垂直耦合两种方法进行了实验研究,得到的平均耦合效率均达70%以上.比较了两种耦合方式的利弊.针对列阵光纤耦合的特点,介绍了列阵光纤耦合过程中光纤的位置、角度的调整方法和特点.     

30Gbit/s并行光发射模块制作过程中的光耦合及封装

介绍了并行光发射模块制作过程中,垂直腔面发射激光器列阵与列阵光纤的对准及固定方法.对斜面光纤折弯耦合和垂直耦合两种方法进行了实验研究,得到的平均耦合效率均达70%以上.比较了两种耦合方式的利弊.针对列阵光纤耦合的特点,介绍了列阵光纤耦合过程中光纤的位置、角度的调整方法和特点.     

基于MT光纤适配器的光垂直耦合器件制备技术研究北大核心

针对光波导互连背板中的光纤-光波导垂直(90°转向)耦合技术,提出了一种基于MT光纤适配连接器的光垂直耦合器件制备方法。详细阐述了紫外光固化胶在光纤适配连接器上的涂膜方法,通过准分子激光器的阶梯刻蚀法对固化胶薄膜顶部端面进行45°微反射镜制备;分析了所制备样品参数如斜面粗糙度、斜面几何尺寸以及耦合元件垂直耦合性能。     

30Gbit/s并行光发射模块制作过程中的光耦合及封装

介绍了并行光发射模块制作过程中，垂直腔面发射激光器列阵与列阵光纤的对准及固定方法. 对斜面光纤折弯耦合和垂直耦合两种方法进行了实验研究，得到的平均耦合效率均达70%以上. 比较了两种耦合方式的利弊. 针对列阵光纤耦合的特点，介绍了列阵光纤耦合过程中光纤的位置、角度的调整方法和特点.     

基于梯度折射率透镜的850 nm光互连模块的研究

设计了波长为850 nm的4×4阵列光互连模块,利用ZEMAX软件对使用双柱面透镜和梯度折射率透镜的系统光路进行了模拟计算,通过比较,设计最终采用了对准容差更大的850 nm梯度折射率透镜.利用1×4的梯度折射率透镜阵列将1×4的850 nm垂直腔表面发射激光器(VCSEL)阵列和2×4的Si探测器阵列连接起来,经对准后组装成了1×4的线列光互连模块,模块的信号电流/串扰电流比大于0.53×105.     

1310nm FP TO-CAN偏心封装耦合效率的研究

文章应用ZEMAX软件模拟了管芯与光纤在不同偏移量下的耦合效率,并进行了实验验证.结果表明,6.5 mm焦距的TO-CAN(晶体管外壳封装)与端面倾斜8°的光纤,在管芯偏移100μm时,耦合效率最大,模拟值为21.9％,实验值为21.32％;5.8 mm焦距的TO-CAN与端面倾斜6°的光纤,在管芯偏移80 μm时,耦...     

MIMO OFDM系统中同步和信道的联合估计

提出了一种MIMO OFDM系统的定时恢复、频率同步和信道估计的联合算法。为了减少算法的复杂度，算法分两步完成：首先利用接收信号的自相关函数进行粗同步和信道估计，得到时延和频偏的粗估计，然后在粗估计基础上采用最大似然准则进行精确的同步和信道估计。仿真结果表明，该算法能够达到很好的效果，系统误码率接近已知信道响应时的情况。     

A Gate Leakage Feedback Element in an Adaptive Amplifier Application

This brief presents a method to exploit gate leakage (GL) to create a feedback element for an input offset insensitive and output offset programmable inverting amplifier. Measurements are shown from a test circuit produced in a 90-nm multithreshold CMOS process where a GL element uses thin oxide and a amplifier input stage uses thick oxide. The feedback element has very high nonlinear impedance from about 100 M to several gigaohms depending on the applied voltage, and is suitable for adaptive applications where long time constants (1 ms to 1s) are required and small, slowly wandering offsets can be tolerated.     

2m主镜主动支撑优化设计

结合某空间光学系统的任务需求,对其2m口径主镜的支撑难点作了详细的论述。为了使主镜达到光学设计所要求的面形精度,运用了结构有限元法和优化设计方法对主镜进行了支撑位置优化;并分别针对主镜轴向1 g 重力载荷、轴向1 g 重力载荷耦合1℃均匀温升两种工况,以主镜镜面RMS 为目标函数、力驱动器驱动力为优化变量进行了多参数优化。通过优化获得了最佳的驱动力组合,镜面RMS 分别达到19 nm、43 nm。该方法具有一定的应用价值。     

Quasi-exact optical analysis of oxide-apertured microcavity VCSELsusing vector finite elements

We report a new full vector finite element model for analyzing the optical properties of azimuthally symmetric oxide-apertured vertical-cavity surface emitting lasers (VCSELs). Our model allows for quasi-exact calculation of the lasing mode blueshift, threshold gain, and field profile. Through a detailed analysis of a sample VCSEL, we ascertain the physical effects which determine diffractive or parasitic mode loss. They are: 1) the background density of parasitic modes and 2) the coupling strength between the lasing mode and the parasitic mode continuum. The coupling strength is in turn determined by the relative alignment between the lasing and parasitic mode propagation vectors and the lasing mode penetration into the oxide region. This analysis improves our understanding of the optical physics of apertured VCSELs and should enable the next leap down in lasing threshold     

Fiber misalignment in silicon V-groove based optical modules

The use of anisotropically etched silicon optical benches (SiOB) and optical adhesives have attracted much attention for the low cost assembly of optical modules. In this paper, the effect of attachment process parameters (such as the amount of bulk adhesive, and the thickness/symmetry of the adhesive layer between the fiber and V-groove walls) on the alignment of the fiber with the laser diode assembled on SiOB, is studied. Finite element analysis (FEA) on the fiber displacement within the V-groove at a given temperature, increases significantly for different thicknesses of adhesive layers, present on either side of the fiber but does not change much with the total amount of adhesive in the module. Validation of the FEA data was accomplished by the use of in situ micro moiré interferometry, involving determination of the displacement of the centre of the fiber in the V-groove exposed to a temperature excursion ranging from room temperature to 125 °C. Maximum displacements of the fiber centre in the vertical and horizontal directions relative to the SiOB were found to range between 0.69–1.21 and 0.36–0.42 μm, respectively at 100 °C. The misalignment results obtained by moiré interferometry matched favorably with the finite element data. The simulation and experimental data in this study indicates that fiber misalignment due to temperature cycling can be reduced significantly if the fiber is located equidistant from the two inclined walls of the Si V-groove.     

Reliability by Robust Design for optical alignment in a CD pickup

Micron-level alignment of optical components in the laser pickup of a compact disc (CD) system is critical for its performance. The robustness of the rotational alignment of the laser/diffraction grating unit (LDGU) is studied in detail using finite element analysis and Robust Design tools. Robust design simulations were constructed in terms of the process capability indices C_p, C_pk, and yield of the clamping arms used to hold the LDGU in place. Effects of force and torsional load from the actual process were taken into consideration during the simulations. Experimental measurement was used to verify the finite element analysis. The results from both experimental and theoretical analyzes were applied to concurrently modify the design of the clamping arms, reducing the fall-off rate in the production of the laser pickup by 10%. It is demonstrated that the finite element analysis together with the Robust Design approach form a very powerful tool for the designer to achieve the required reliability targets for the product     

Joint Time-Domain Tracking of Channel and Frequency Offsets for MIMO OFDM Systems

In this paper we address the problem of joint channel and frequency offset estimation and tracking in multiple-input multiple-output (MIMO) OFDM systems for mobile users. The proposed method stems from extended Kalman filtering and is suitable for time-frequency-space selective channels. Separate offset for each MIMO channel branch is considered because of the mobility and rich scattering. The channel taps and the frequency offsets are estimated in time-domain while the equalization is performed in frequency domain. Simulation results demonstrate that the proposed method tracks time-varying channels and frequency offsets with high fidelity. Realistic channel models are used in mobile scenarios. The proposed time-domain approach has improved performance and robustness in comparison to purely frequency domain processing. Computational complexity is lower as well.     

Design and analysis of a novel tunable optical filter

In this paper, an improved design of a tunable optical filter device which is driven by a piezoelectric actuator is proposed. The device can be used either as a tunable optical filter for discrete wavelength alignment or as a dynamic optical filter. The tunable filter is electrostatically driven and consists of three main parts: The electromechanical stage, the suspension and the thin film optical filter. The electromechanical stage and the suspension were designed using graph presentation methods, studied numerically using the finite element method (FEM). The thin film optical filter was designed by a thin film design software. The electromechanical stage was integrated with the suspension and tested as an angular driver of thin-film tilt interference filter for dense-wavelength division demultiplexing system applications.