Internal spatial modes in glass microring resonators

We have used near-field scanning optical microscopy to measure the internal optical modes inside glass waveguides and microring resonators. The period of the observed standing modes provides a direct measure of the local effective index. The measured effective index and modal shape determines the values of all components of the wave vector. The observed standing modes inside the ring resonator are unexpected, but are caused by the standing modes in the coupling waveguide. Last, we describe a technique that can obtain detailed information about the locations of the dielectric interfaces     

Digitally tunable ring laser using ladder filter and ring resonator

We propose a digitally tunable ring laser incorporating a ladder filter and a ring resonator. The widely tunable ladder filter consists of two input-output waveguides and a waveguide array, and it selects one channel from the periodic outputs of the ring resonator. With this device, the passband of the ladder filter is important in terms of obtaining stable lasing operation and it becomes narrower with increasing diffraction order. However, the free-spectral range of the filter is reduced with increasing diffraction order and this induces lasing mode instability. We therefore optimize the diffraction order of the ladder filter. The device is monolithically integrated by using the InP-InGaAsP material system. We achieved 37 channel 1000-GHz spacing digitally tunable laser operation. A promising way of improving the device performance is to use a chirped ladder filter because this filter has one dominant passband.     

Fabrication-tolerant active-passive integration scheme for vertically coupled microring resonator

The large-scale photonic integration of microring resonators in three dimensions made possible by recent developments in vertical coupling and wafer bonding technology is shown to be sensitive to lateral mask misalignment for the ring and bus waveguides introduced during the fabrication process. For a typical 20-/spl mu/m radius, vertically coupled microring calculations reveal a linear relationship between deviation in the coupling coefficient and lateral misalignment. A coupling coefficient reduction of 50% is predicted for a lateral misalignment of 0.3 /spl mu/m, which is typical for an alignment accuracy limited by the current state-of-the-art mask alignment process. The use of a wide multimode bus waveguide is proposed to ameliorate this alignment sensitivity. The mode-expanded bus waveguide, together with its physically wider structure, reduces the dependence of modal overlap and coupling length on precise alignment, resulting in significantly relaxed fabrication tolerance. Deviation of coupling coefficient decreases by an order of magnitude for the new ring coupler geometry, where a sole reduction of 5% is obtained for the same amount of misalignment. The implications of the proposed structure are subsequently investigated for microring laser performance. The differential slope efficiency is shown to be at least five times less sensitive to lateral misalignment for the proposed structure within a small misalignment regime. This readily adaptable coupler geometry based on existing vertical coupling architectures is transferable to any fabrication scheme with multiple waveguide layers coupled vertically, and is of particular importance to microring resonators with small radii.     

基于方形开环的双模滤波器设计

在传统方形开环谐振器的基础上,设计了一种新型的双模微带滤波器,该滤波器包含两个方形开环谐振器,在每个传统谐振器内部添加微带支路结构,通过微扰来实现频响特性的改善,由仿真结果可以看出,该设计的带内特性良好,带内波纹小于0.3dB,通带边沿均插入了传输零点,且传输零点处的S21〈40dB,截止边沿陡峭,实现了6%的相对带宽,整个滤波器的尺寸大小约为30mm×20mm,改进后的结构与传统结构相比降低了0.5GHz的中心频率,相对减小了16%的面积,进一步实现了小型化。     

Microring Resonators Made in Poled and Unpoled Chromophore-Containing Polymers for Optical Communication and Sensors

Poled and unpoled chromophore-containing polymers offer some unique advantages in device functionality and fabrication. UV light and electron beam (e-beam) can bleach out the color of chromophores and reduce the index of refraction of the polymer. The photobleaching and e-beam bleaching methods form optical waveguides in a single step and do not involve solvents or wet chemicals, and can be applied to polymers that are not compatible with other waveguide fabrication techniques. A variety of microring resonator devices for fiber-optic telecommunication and sensors have been realized with chromophore-containing polymers. A novel broadband fiber-optic electric field sensor is presented as an example. The sensor uses a polymer with chromophores preferentially aligned after electric poling, and the microring resonator is directly coupled to the core of optical fiber. The feasibility of vertical integration of a poled electrooptic polymer waveguide device interfaced with silicon microelectronic circuits is also demonstrated.     

基于多级广义自适应形态学滤波的电力信号消噪

针对传统数学形态学滤波器存在的统计偏移现象和对结构元素选取的局限,提出了一种多级结构元素的改进方法,并采用变步长的方法构建了一种多级广义自适应形态学滤波器,在提高滤波精度的同时,降低了对结构元素选取的限制,并且该滤波器的使用更加灵活。最后,将该滤波器应用到含有多种噪声叠加的电力信号消噪中,通过算例仿真,验证了提出的多级广义自适应形态学滤波器相比于传统的数学形态学滤波器,在电力信号消噪中具有更好地滤波效果。     

Silicon-Based Microring Resonator Modulators for Intensity Modulation

We numerically analyze the characteristics of silicon-based microring modulators consisting of a single-ring resonator. Performance of the devices as digital intensity modulators is examined in terms of extinction ratio, pulsewidth, frequency chirp, spectral broadening, and signal quality. Three types of the modulators built in single-waveguide under-/overcoupling and dual-waveguide configurations are discussed. We show that cavity dynamics significantly affect the modulation properties. Data transmission performance over single-mode fibers is also presented. A silicon microring modulator with negative chirp could achieve 0.8 dB power penalty in 80-km fiber transmission without dispersion compensation.      

基于多层带状线谐振子结构的带通滤波器设计

采用多层耦合带状线谐振子结构和高介电常数材料实现带通滤波器的微型化设计.谐振子的谐振频率采用Sonnet软件计算得出,谐振子的耦合系数采用Sonnet和HFSS仿真计算得到,最后采用HFSS进行结构调整以实现设计优化.该方法设计过程简便易行,得到的滤波器结构简单,易于制作.采用该设计方法设计并制作了一个L波段的5阶低温...     

错时采样空间矢量调制的级联型多电平变流器及其在并联有源电力滤波器中的应用

介绍了错时采样空间矢量调制的基本原理,讨论了组合变流器与级联型多电平变流器的等价关系,提出了错时采样空间矢量调制在级联型多电平变流器中的实现方法,并进行了实验验证.给出了基于错时采样空间矢量调制级联型多电平变流器的并联电力有源滤波器的拓扑结构,设计了其交、直流控制系统,并以仿真和实验结果加以验证.仿真和实验结果表明,基于错时采样空间矢量调制级联型多电平变流器的并联有源滤波器可以在较低的开关频率下准确、有效地补偿负载谐波和无功功率.     

Modeling of ring resonators with tunable couplers

Controlling the characteristic response of the ring resonator through adjustable coupling can be useful in variety of applications, such as add-drop filters, modulators, lasers, switches, sensors and others. Coupled mode theory (CMT) is effectively utilized for modeling of a generic micro-resonant cavity with two independently adjustable add/drop couplers and integrated phase-shifter(s). It is shown that for a lossy cavity the non-identical input/output coupling values are required to satisfy a resonance condition. The critical coupling and coupling/loss optimization is discussed for the regular and /spl delta//spl beta/-reversal tunable couplers. Resonance coupling diagram is derived for passive and perturbed resonator structure for these types of tunable couplers.     

Optically Tunable Delay Line in Silicon Microring Resonator Based on Thermal Nonlinear Effect

We experimentally demonstrate optically tunable delay line in a silicon microring resonator with a 20- m radius. The delay-tuning mechanism is based on the red shift of the resonance induced by thermal nonlinear effect. We investigate the delay performance of three modulation formats-non-return-to-zero (NRZ), return-to-zero (RZ), and differential phase-shift keying (DPSK) signals at different data rates. Tunable delay is achieved by controlling the power of the continuous-wave (CW) pump with very low tuning threshold, which could be used in microring-resonator-based slow-light structure.     

Generalized interdigital filters made of multilayer striplines

In the first part of this paper is presented a relatively simple loss analysis method for many coupled line structures. The corresponding equivalent circuit consists of uncoupled lossy transmission lines whose parameters are determined relatively easily without a complex numerical field analysis by using fringing-capacitance curves for rectangular strips. In the narrowband case further approximations are possible. The increase of the accuracy is most significant if the couplings between strips are tight. In the second part a realization of the generalized interdigital filter using a multilayer structure consisting of polyphenyleneoxide plates is discussed. The repeatability of the filters is improved with the aid of thin polyethylene films. The shorts are made by the copper coating that also effectively suppresses higher-order modes. The fine tuning of the filter can be made by tuning screws. The improvement of the design accuracy without tuning elements using a computer simulation is also discussed. Finally, the effects of the losses are studied, connecting the loss analysis presented with ring resonator measurements.     

基于H桥级联型变流器的有源电力滤波器

提出了一种基于H桥级联型变流器的有源电力滤波器(APF)系统的电路拓扑结构,分析其闭环控制策略和主电路系统参数。对APF样机进行了无功补偿试验和不平衡补偿功能试验。试验结果表明,APF系统动态响应速度快、补偿性能良好,验证了理论分析和样机装置设计的正确性。     

风力发电机特性测试方法的对比

针对双馈式风力发电机一类变速驱动的感应电动机性能参数的标准测试方法在精确度和灵敏度方面存在的不足,对几种测试方法进行了对比分析,以提高发电机的效率。结果表明:与标准IEEE 112规定的测试方法相比,应用串联耦合测试方法能够更好地估算发电机的参数和预测发电机的稳态性能。     

Power-handling capability for RF filters

A simplified method for evaluating the power-handling capability inside an RF filter has been introduced based on the general cross-coupled prototype network theory, modern EM modeling techniques, and well-established breakdown threshold analysis. The electrical field strength and voltages evaluated using either the single-cavity resonator (eigen mode) model or simply the prototype model have been presented and compared against the direct EM computation of the complete filter structure. Close agreement has been found between the full EM modeling and the scaling of a single resonator or even prototype network analysis only. This procedure is expected to simplify the multipaction and ionization breakdown analysis of filters and filter-based diplexers and multiplexers. The method presented is general and is applicable to all filter types that can be described in a circuit model. Practical issues such as the multicarrier operation, sharp edge condition, design margin, and prevention techniques are also covered.     

Comparative Study of Losses in Ultrasharp Silicon-on-Insulator Nanowire Bends

Ultrasharp silicon-on-insulator (SOI) nanowire bends (with a bending radius of R < 2 mu m) are analyzed numerically. It is shown that the calculated bending losses for ultrasharp bends are overestimated when using a modal analysis method based on finite-difference method. In this case, reliable estimation of the bending loss can be made with a 3-D finite-difference time-domain (3-D-FDTD) method. By using 3-D-FDTD simulation, the losses in SOI nanowire bends with different structures and parameters are studied. By increasing the core width or height of the waveguide, one can reduce the bending loss at longer wavelengths for TE mode while the bending performance at shorter wavelengths degrades due to the multimode effect. Increasing the core height is much more effective to reduce the bending loss of TM mode than increasing core width. The relationship between the intrinsic Q-factor of a microring resonator and the bending radius is also obtained.     

Microring-Resonator-Based Widely Tunable Lasers

We describe widely tunable lasers incorporating microring resonators. By using a double-ring-resonator-coupled filter, a wide wavelength tuning range is achieved with a low tuning current. A double-ring-resonator-coupled tunable laser has series-connected microring resonators in the laser cavity. A tuning range of 50 nm is achieved with injection current of less than 5.2 mA. This low injection current reduces the frequency drift caused by thermal transients to less than 5 GHz. We also describe an integrated filtered feedback tunable laser consisting of a Fabry–Perot (FP) laser and integrated filtered feedback sections. In this device, the filter section is removed from the laser cavity. The device exhibits a 24-nm tuning range with a side-mode suppression ratio of 50 dB. The frequency drift is less than 1 GHz because the longitudinal mode of the laser is mainly determined by the FP laser section. We have also developed a filter-free widely tunable wavelength converter by monolithically integrating a tunable laser and a wavelength converter based on a semiconductor optical amplifier. Wavelength conversion for a 10-Gb/s nonreturn-to-zero signal is also demonstrated, tunable over a 40-nm range.      

载波相移SPWM级联H型变流器及其在有源电力滤波器中的应用

提出了基于CPS-SPWM技术的级联H桥型多电平变流器,它是CPS-SPWM技术与级联H型变流器拓扑结构的结合。这种变流器能在较低的器件开关频率下实现较高等效开关频率的效果,具有结构简单、传输频带宽、动态响应好等优点。文中将这种变流器用在有源电力滤波器这样大功率场合,在并联有源电力滤波器系统中,由于直流侧不需要提供有功功率,级联型多电平变流器的优势可以得到充分的发挥;而载波相移PWM技术良好的谐波传输特性也可以得到良好的利用。仿真和实验结果表明基于CPS-SPWM技术级联 H桥型多电平变流器的SAPF系统能够在较低的器件开关频率下实现较好补偿效果,具有良好的工业应用前景。     

Tuneable Two-Pole One-Dielectric-Resonator Filter with Elliptic Characteristics

A frequency tuneable microwave filter based on a dual mode dielectric resonator has been developed. Tuning of the filter was realised by using metal plate located over the dielectric resonator and moved along the resonator axis by a piezoelectric bimorph. The main parameters of the filter were: central frequency in the middle of the range of tuning—2.35 GHz, bandwidth for 1dB level—～ 0.5%, range of tuning—～ 10%. The insertion losses in the whole tuning range were below ～ 1 dB.     

基于FPGA实现高插入CIC滤波器

为了产生调制信号的码元速率能在大范围内实时可变,采用插值滤波技术——多级积分梳状滤波器。在分析多级CIC滤波器的结构和特性的基础上,阐述了一种利用Hogenauer＂剪除＂理论实现多级CIC滤波器的高效FPGA实现方法,并通过XILINX的时序仿真分析验证了该方法的正确性和可行性,实际中可以推广应用。