Theoretical Investigation of Polarization-Insensitive Multimode Interference Splitters on Silicon-on-Insulator

An ultracompact polarization-insensitive 1times2 multimode interference (MMI) splitter based on silicon-on-insulator is investigated theoretically. The impact of the insulator index on the size of the MMI and the polarization-dependent performance is analyzed. A polarization-insensitive 1times2 MMI splitter of 4 mum by 16.5 mum is shown as an example. Relaxed tolerances on MMI width (> plusmn100 nm) and length (> plusmn0.7 mum) are obtained for both polarizations while the polarization differential loss is kept in range of 0.1 dB and its excess loss is kept below 0.5 dB. In addition, a wide operation wavelength window of 150 nm is obtained for both polarizations as well.     

Shortened Polarization Beam Splitters With Two Cascaded Multimode Interference Sections

This letter presents a design for shortening the length of a polarization beam splitter (PBS) by using two cascaded multimode interference (MMI) sections with different widths. By optimizing the MMI parameters, a short PBS of good performance is achieved. The total length of the PBS is reduced to about 1/28 of that of a conventional design.      

Tapered Multimode Interference Combiners for Coherent Receivers

报道了一个新的基于锥形多模干涉的相干光波合波器.对锥形多模波导中的模式行为给出了完整的理论分析,并给出了该锥形合波器在不同结构下的输出特性.在一个绝缘体上硅的基板上实现了该器件.鉴于无后向反射,容易扩展为多口配置,对实验误差有大的允许度和尺寸紧凑等优点,这种锥形多模干涉的合波器是大型光子集成中所用的相干光波合波器的理想选择.     

用于相干接收的锥形多模干涉合波器

报道了一个新的基于锥形多模干涉的相干光波合波器.对锥形多模波导中的模式行为给出了完整的理论分析,并给出了该锥形合波器在不同结构下的输出特性.在一个绝缘体上硅的基板上实现了该器件.鉴于无后向反射,容易扩展为多口配置,对实验误差有大的允许度和尺寸紧凑等优点,这种锥形多模干涉的合波器是大型光子集成中所用的相干光波合波器的理想选择.     

渐变折射率多模光纤中的多模干涉应用研究

论述了SMS(单模-多模-单模)光纤结构的多模干涉基本理论,利用FD-BPM(有限差分光束传播法)对渐变折射率多模光纤和阶跃折射率多模光纤进行数值模拟,将自聚焦位置、激发模式等特征进行对比,给出渐变折射率多模光纤的优点。利用自聚焦效应,对渐变折射率多模光纤的聚焦和发散作用进行了理论分析,以较短的长度充当透镜的功能,并总结了现阶段的主要应用。     

短波宽带波形干扰抑制技术

短波宽带波形是现代短波通信的最新研究成果,采用带宽扩展方式实现短波高速通信。短波信道存在的各种各样强干扰信号使得干扰抑制成为现代短波宽带通信急待解决关键问题之一。针对这种现象,提出了一种基于变换域选择的双门限干扰抑制方法,该算法可以有效地选择最佳变换域去抑制干扰。仿真结果表明这种干扰抑制方法能够抑制不同类型干扰信号,在干扰环境下短波宽带波形具有较好传输性能。     

Research Progress on Multimode Interference Switches

Optical switches are key components for constructing optical communication networks, so it is necessary to design optical switches and optical switch arrays with high performance and low cost. As one type of optical switches, the multimode interference（MMl） switches have received considerable attention due to their unique merits. The structures and operation principles of various types of MMI switches are introduced, and the recent progresses of MMI switches are also discussed.     

赝态结构多模干涉波分复用器的研究

为了减小波分复用器的器件长度,在聚酰亚胺材料的基础上,设计了一种赝态结构的2×2多模干涉波分复用器,并用精确导模分析法对其进行模拟分析和优化设计.结果表明,赝态结构波分复用器可以有效地对980 nm和1 550 nm光进行解复用,而器件尺寸只有传统设计的1/5;且器件在器件长度和波长变动中显示出良好的容差性,能够与掺铒放大器和激光器实现集成.其中,赝态结构多模干涉聚酰亚胺波分复用器的干涉区宽度和长度以及输入口宽度和距离对其性能均有影响.     

基于多模干涉的光学逻辑编码器

根据多模干涉（MMI）器件的重叠成像理论,提出了基于MMI结构的光学逻辑编码器件,借助于区域相位调制方法,具体设计了一维2^3 bit光学逻辑编码器。根据光束传输理论,用Beamprop软件进行了输出态的模拟和输人参数的优化,通过不同的相位调制方法,得到了消光比大于11dB的各种布尔逻辑态。     

蝶形多模干涉耦合器的数值分析

设计蝶形多模干涉(MMI)耦合器时,需要根据所要求的功率分割比率确定器件的结构参量。作为矩形多模干涉耦合器的特征参量的耦合长度,通过数值分析对称干涉型矩形多模干涉耦合器的成像位置而得到,从而可利用模传输分析(MPA)法的公式设计出蝶形多模干涉耦合器的理论预期结构。使用有限差分波束传输法(FD-BPM)对设计参量进行校正,并且数值算出器件实际实现的功率分割比率。针对基于SOI晶片的设计实例表明,仿真得到的蝶形多模干涉耦合器的长度较理论预期大2～4 μm,实际实现的功率分割比率较理论预期值低且器件形状越偏离矩形,其值相差越大。     

可调谐高分子MMI光波导功率分配器的研究

设计了一种基于多模干涉(MMI)波导结构的可调谐功率分配器,利用高分子含氟聚酰亚氨材料的热光效应,调节多模波导中局部区域的折射率,可实现两单模输出导模的输出功率比在较大范围内连续可调谐.BPM防真证实了这一结果.     

Compact High-Performance Multimode Interference Couplers in Silicon-on-Insulator

We demonstrate compact multimode interference (MMI) couplers on silicon-on-insulator that exhibit both high performance and relaxed tolerances. The devices are fabricated with a single shallow etch step on 1.5-mum-thick silicon, and have a footprint of 12.8 mum times 456 mum, including 100-mum-long tapers at input and output. In a Mach-Zehnder configuration, we achieve an extinction ratio larger than 22 dB for transverse-electric polarization and larger than 20 dB for transverse-magnetic polarization. This extinction ratio is maintained in the full 1520- to 1580-nm band and for MMI width variations in a range of 0.45 mu m. We also show appreciable tolerance differences between paired and general excitation MMIs.     

Compact Dual‐Wideband Bandpass Filter with Multimode Resonator

A microstrip dual‐wideband bandpass filter using a multimode resonator (MMR) is proposed in this letter. The proposed MMR loaded with a T‐shaped open‐ended stub and a short‐ended stub exhibits triple mode characteristics, and a synthesis method is developed to illustrate the wide passband with independently controllable center frequencies and bandwidths. To verify this design methodology, a dual‐wideband filter with fractional bandwidths of 19.1% and 27.9% is designed and fabricated. The measured results agree with the simulations.     

Multi-access Interference Cancellation Receiver for Time-Hopping Ultra Wideband Communication

In this paper, a low complexity coherent joint maximum-likelihood detection receiver is developed for canceling multi-access interference in impulse radio (IR) based ultra wideband (UWB) wireless communication systems. Unlike previous joint demodulation receivers, where the complexity is enormous and the other users’ codes are required, the proposed approach does not need to know the time hopping (TH) codes of the other users which makes it a very attractive solution. The performance of joint demodulation receiver depends on the ability to estimate the channel coefficients of desired and interfering users. A novel and practical algorithm for estimating multiple users’ channel responses is developed. The performance of the proposed algorithms are tested through computer simulations and the results are compared with the performance of the conventional single user UWB receiver. It is observed that the proposed joint demodulation receiver provides significant performance gains with respect to conventional single user receiver. This paper is presented in part in IEEE International Conference on Communications (ICC) 2004, Paris, France.     

多模干涉型集成光学器件研究进展

基于自镜像效应(SIE)的多模干涉(MMI)型集成光学器件是集成光学中具有广泛用途的重要器件。本文详细而系统地综述了近几年来MMI器在国内外的研究进展，特别是其在集成光学中的应用。     

多模干涉耦合器重叠成像特性分析

根据多模干涉(MMI)耦合器的自映像原理,研究了输入场位置、位置数对重叠成像个数和成像位置的影响,总结出重叠成像规律,给出了重叠成像位置和成像个数的有关计算公式。用导模传输分析法验证了计算公式和重叠成像规律的正确性。     

A Wideband and High Rejection Multimode Bandpass Filter Using Stub Perturbation

A novel multimode bandpass filter with high and wide rejection band is proposed by using an open stub. The open-stub has two functions in the filter: (1) perturbation for the multimode operation and (2) zero point generation at the stopband for the stopband control. With proper input/output coupling, additional two poles, i.e., four poles, can be generated for the proposed filter structure. The design is then verified by experiment. The single structure four-mode filter has low insertion loss, good stopband performance, and compact size and linear phase.     

宽带通信中的干扰抑制处理方法研究

综述了DS/FH宽带通信系统中的干扰抑制预滤波处理方法，并侧重时频域的干扰消除技术，基于有关处理算法的适用条件和性能，探讨多系统共存环境下AIC（自适应干扰消除）处理的使用。     

短波宽带信道中噪声与干扰建模

短波通信系统依靠电离层传播,具有通信距离远,灵活性高,抗干扰性强,成本低廉等特点,是一种重要的国防军事通信手段。传统短波通信受电离层特性影响而有效带宽较窄,导致数据传输速率极低。因此,提高信道容量实现高速数据传输的短波宽带通信系统越来越受到重视。短波宽带信道建模是短波宽带通信系统正常发挥性能的关键,对短波宽带通信系统的设计与实际应用具有重要的实际意义。结合现有短波宽带信道的衰落特性模型,介绍了短波宽带信道噪声和干扰模型,并进行了比较和可靠性分析,发现现有模型形式比较单调统一,但和实际测量数据一致,能有效描述短波宽带通信中信道噪声与干扰特性,模型已经比较完善。最后,提出了进一步研究的重点方向。     

A Design Procedure for High-Performance, Rib-Waveguide-Based Multimode Interference Couplers in Silicon-on-Insulator

Single mode silicon-on-insulator rib waveguides offer a weak lateral confinement, which makes it difficult to design high-performance multimode interference couplers (MMIs) based on these waveguides. Here, a complete design procedure for single etch step MMIs with tapered rib access waveguides is presented, which yields low excess loss (0.1 dB) and good imbalance (0.02 dB). Furthermore, polarization dependence is low, and high fabrication tolerances are achieved, especially with respect to etch depth.