温度和振动对光纤马赫-曾德干涉仪的影响与动态补偿研究

环境温度变化和振动会引起光纤马赫-曾德干涉仪两臂相差随机性变化,致使干涉仪输出不稳定.本文研究了自然条件下外界温度和振动对基于3×3耦合器干涉仪的影响,分析结果表明,温度和振动所引起的干扰主要集中于100Hz以下的低频成分中.为了消除这些干扰,设计了单臂补偿的反馈回路以稳定输出信号,并提出了一种利用象限判决方法来区分反馈正负性的动态补偿方法.实验中利用3×3耦合器3个输出端中其中2个进行光电变换、差分放大等反馈电路后驱动管状压电陶瓷,使缠绕在其上的光纤伸缩,动态补偿干涉仪相差的漂移,稳定干涉仪输出即3×3耦合器第三输出端口的信号.针对自然环境下温度和振动引起的干扰,本文研制了一种稳定的动态补偿装置,能有效抑制160Hz以下的低频干扰,实时补偿干涉仪两臂的相差漂移,干涉仪输出稳定的干涉信号,波动幅度小于5.64%.     

基于全反射的发光二极管-照明光纤耦合器的设计与研制

光纤照明由于具有成本低、安全性高、便携性好和装饰性强等优势,已经逐渐进入了人们的视野。然而,现阶段的光源[特别是发光二极管(LED)]由于辐射发散角大,与照明光纤的耦合效率普遍较低。为了解决这个问题,根据全反射原理,设计并制作了一种LED-照明光纤耦合器。经过实验验证,该耦合器具有聚光性强、耦合效率高、体积小、制备简便和成本低等优点,是一种能够有效提升LED-光纤耦合效率的方式。     

RF thermal and new cold part design studies on a TTF-Ⅲ input coupler for Project-X

An RF power coupler is one of the key components in a superconducting (SC) linac. It provides RF power to the SC cavity and interconnects different temperature layers (1.8 K, 4.2 K, 70 K and 300 K). The TTF-Ⅲ coupler is one of the most promising candidates for the High Energy (HE) linac of Project X, but it cannot meet the average power requirements because of the relatively high temperature rise on the warm inner conductor, so some design modifications will be required. In this paper, we describe our simulation studies on the copper coating thickness on the warm inner conductor with RRR values of 10 and 100. Our purpose is to rebalance the dynamic and static loads, and finally lower the temperature rise along the warm inner conductor. In addition, to get stronger coupling, better power handling and less multipacting probability, one new cold part design was proposed using a 60 mm coaxial line; the corresponding multipacting simulation studies have also been investigated.     

Measuring the performance of the coaxial HOM coupler on a 2-cell TESLA-shape copper cavity

Coaxial High Order Mode (HOM) couplers have been fabricated at Peking University and their RF performance has been measured on a test device consisting of a coaxial transmission line and a 2-cellTESLA-shape copper cavity. The test results on the 2-cell TESLA-shape copper cavity with HOM couplers indicate that the coupler can cut off the fundamental mode TM010 and absorb HOMs effectively after a careful adjustment. The optimal angle of the HOM coupler with the beam tube is found. The initial test results of HOM couplers are presented in this paper.     

Fabrication of the high power input coupler for BEPCⅡ superconducting cavities

The BEPCII storage ring adopts two 500 MHz superconducting cavities (SCC). Each one is equipped with a 500 MHz input power coupler. The coupler is to feed 150 kW power in continuous wave (CW) mode with both standing and traveling wave modes. Due to high power feeding and high frequency of the coupler, its fabrication is a big challenge. The fabrication started with two key components, the window and the antenna. Up to now, two sets including windows and antennas have beam made by IHEP. And a 270 kW RF power in CW has passed through the coupler during the high power test. The fabrication details are presented in this paper.     

High efficiency and broad bandwidth grating coupler between nanophotonic waveguide and fibre

A high efficiency and broad bandwidth grating coupler between a silicon-on-insulator (SOI) nanophotonic waveguide and fibre is designed and fabricated. Coupling efficiencies of 46\% and 25\% at a wavelength of 1.55~μ m are achieved by simulation and experiment, respectively. An optical 3~dB bandwidth of 45~nm from 1530~nm to 1575~nm is also obtained in experiment. Numerical calculation shows that a tolerance to fabrication error of 10~nm in etch depth is achievable. The measurement results indicate that the alignment error of ±2~μ m results in less than 1~dB additional coupling loss.     

用统一耦合模理论分析含布拉格光栅的对称光纤耦合器的传输特性

利用由麦克斯韦方程组直接导出的统一耦合模理论分析各类型的含布拉格光栅的对称光纤耦合器的传输特性。与以前发表的分析方法不同,对于含布拉格光栅的耦合区域,统一耦合模型理论同时考虑了布拉格光栅和耦合的耦合作用。模拟结果证明它能精确地模拟和解释各种类型的含布拉格光栅的对称光纤耦合器的有关实验现象。     

宽带消波长依存波导耦合器的统计优化设计

提出了一种适合于宽带消波长依存波导耦合器的统计优化设计方法。使用该方法 ,在 12 80nm～ 165 0nm带域内 ,对Si基SiO2 光波导作了包括偏振变动优化在内的 5 0 %和 2 0 %功率耦合比的消波长依存波导耦合器的设计。两个器件经三维波束传播法 (BPM)模拟运行验证 ,结果表明 ,在 370nm宽带内 ,两个直交偏振态均实现了功率耦合比为 (5 0± 2 .1) %和 (2 0± 1.4) %、偏振变动量分别小于 0 .65 %和 0 .2 0 %的良好特性     

A Novel Acoustic Emission Fiber Optic Sensor Based on a Single Mode Optical Fiber Coupler

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Influence of group—velocity mismatch on soliton switching in a nonlinear fibre coupler

In this work, the influence of group-velocity mismatch on soliton self-routing pulse switching in a nonlinear fibre coupler is discussed in detail by the use of both variational approach and numerical simulation. The results obtained show that the group-velocity mismatch leads to the relative displacement between the two orthogonal polarization modes, increase of the critical power, and reduction of the elimination-light ratio. For sub-ps pulse, the influence cannot be neglected.