Polymeric buried core adiabatic optical spot-size transformer

Design, fabrication and characterisation of a polymeric optical spot-size transformer formed by a laterally tapered, buried core is described. Only standard photolithography and dry etching have been used to fabricate this transformer. A fibre to waveguide insertion loss of 0.7 dB has been measured, compared to 2.5 dB without the transformer     

Low-loss spot-size transformer by dual tapered waveguides (DTW-SST)

The reduction of the insertion loss of a spot-size transformer based on dual tapered waveguides (DTW-SST) by controlling the shape of the tapered portion is discussed. The transformer is easily fabricated using a shadow mask sputtering method. A method is described for controlling independently the parameters of the tapered portion, such as the maximum taper angle, and length, and the position of tapered portion with respect to the edge of the shadow mask. A large transformation ratio (5 and 1/5) and a low insertion loss (0.7 dB) have been obtained     

Fundamental mode spot-size measurement in single-mode optical fibres

We report a very simple method for measuring the mode spot size in single-mode fibres on the same apparatus as used for attenuation measurements without additional fibre handling. Measurements as a function of wavelength lead to the equivalent step index parameters allowing one to predict directly the splice, microbending and curvature losses.     

Spot-size converted laser diodes based on mode interference

A novel spot-size converted laser diode, which is based on the interference between guided and leaky modes, has been proposed and demonstrated. We achieved a minimum coupling loss of -3.0 dB to a single-mode fiber and good high-temperature characteristics in a diode with only an 80-μm conversion length     

变电站主变压器经济运行方式研究

本文对变电站主变压器的运行特点进行分析,对如何提高变电站主变压器运行经济性提出几点建议对策,以期提高变电站运行的经济效益和社会效益.     

Monolithic integration of DFB laser with spot-size transformer forhighly efficient laser fibre coupling

The monolithic integration of a mushroom type InGaAs-InGaAsP MQW DFB laser with a spot-size transformer based on a two-layer lateral taper is reported. Highly efficient coupling to a butt-joined dispersion shifted singlemode fibre with a coupling loss down to 0.9 dB and large alignment tolerances was achieved, maintaining the good spectral characteristics of an isolated DFB-laser structure     

一种新的基于共模扼流圈传导干扰模态分离网络

测试传导性干扰的模态噪声,是设计电磁干扰(EMI)滤波器的前提条件。共模扼流圈能够抑制共模模态,而不影响差模电流的输出。根据共模扼流圈这一特点,设计一种由两个共模扼流圈为核心的共模/差模分离网络,实现共模电压和差模电压的同时输出。仿真结果表明,在150 kHz³0 MHz的测试频带,输入端口阻抗基本在50Ω,并且共模传递比(CMTR)、差模抑制比(DMRR)、差模传递比(DMTR)及共模抑制比(CMRR)四个结果显示了该分离网络的良好模态分离效果。     

基于保偏光纤模式干涉的温度传感技术

基于Sagnac光纤干涉仪偏振非互易的光纤温度传感器的理论、方案和相关技术,利用光强度直接测量的信号检测技术,实现了单点温度传感并进行了实验验证.实验和测试表明:这种温度传感器达到了0.01℃的温度分辨率和稳定性,通过改变温度传感头的长度和传感保偏光纤的双折射率,可方便地调节其测量范围.同时又提出了一种新的反射型保偏光纤温度传感方案并研制出微小型保偏光纤温度传感头.在此基础上,实现了多点温度测量,研制出大型变压器绕组温度监控用多点温度传感系统,在0～200 ℃的温度范围内达到了0.5℃的测量精度和分辨率,研制的传感头满足高电压绝缘和热油、热蒸汽的恶劣环境要求.     

基于偏振模干涉的光纤光栅动态应变解调系统

基于保偏光纤中正交偏振模干涉,提出了一种简单、新颖的光纤光栅动态应变解调系统,并且通过实验证实了该方案的可行性。该解调系统光学核心部分仅由一段带有反射镜的高双折射光纤和一个光纤起偏器构成。实验中动态应变解调分辨率达到了 ,频率范围为0.1Hz~7.9kHz微纳振动幅度信号获得了保真拾取。实验表明,该系统适合宽频率范围、微纳幅度的动态应变检测,为光纤光栅传感提供了一种简单、经济、适用范围更广的解调方案。     

基于双光纤光栅传感的电压互感器的研究

介绍了一种新型的光纤电压互感器,针对FBG传感器在现实应用中的温度和应力的交叉敏感问题,设计了一个光纤双光栅温度、电压测量系统,对光纤双光栅的温度和电压传感特性进行了初步的实验研究.     

C-band fundamental/first-order mode converter based on multimode interference coupler on InP substrate

The design, fabrication and characterization of a fundamental/first-order mode converter based on multimode interference coupler on InP substrate were reported. Detailed optimization of the device parameters were investigated using 3D beam propagation method. In the experiments, the fabricated mode converter realized mode conversion from the fundamental mode to the first-order mode in the wavelength range of 1530-1565 nm with excess loss less than 3 dB. Moreover, LP₀₁ and LP₁₁ fiber modes were successfully excited from a few-mode fiber by using the device. This InP-based mode converter can be a possible candidate for integrated transceivers for future mode-division multiplexing system.     

A mode transformer using fin-line array for spatial power-combiner applications

A new TE/sub 10/-to-TE/sub 20/-mode transformer has been developed on the basis of a fin-line array for waveguide spatial power-combiner applications. The fin-line array is designed such that the input TE/sub 10/ mode is split in space into multiple segments, then subject to different signal paths, which effectively converts the TE/sub 10/ mode into a TE/sub 20/ mode, while eliminating the TE/sub 10/ mode at the output. Our Ku-band (14-15 GHz) design indicates that the proposed mode converter makes it possible to obtain the TE/sub 20/ mode with greater than 22-dB suppression of the TE/sub 10/ mode over the band of interest. This converter was used in the design of a waveguide spatial power amplifier involving four monolithic microwave integrated circuit power chips and an output power of 31 dBm has been obtained with a combining efficiency of 80%. A measurement technique has been also developed to measure the electric-field profile inside the rectangular waveguide. A good agreement between measured and simulated results has been observed, showing an effective suppression of the TE/sub 10/ mode, as well as a good TE/sub 20/-mode formation judging from its amplitude and phase.     

Quasi planar spot-size transformer for efficient coupling between acleaved fibre and an InP/InGaAsP rib waveguide

A spot-size transformer structure is proposed for InP/InGaAsP double-heterostructure (DH) rib waveguide. Vertical expansion of a factor of 7 is achieved with 3 dB internal loss. Coupling from standard cleaved fibre (11 μm diameter mode) to a DH rib waveguide (5.8×0.8 μm large mode), is achieved with 4.5 dB polarisation independent loss. Coupling tolerances are highly relaxed. The fabrication method uses a thin cladding layer which ends up to a quasi-planar structure suitable with further integration process     

基于模式分组的帧内预测模式快速选择算法

针对高效率视频编码(HEVC)帧内预测中增加的预测模式引起的的粗选择模式(RMD)与率失真优化(RDO)算法计算复杂度高的问题。本文充分利用候选模式集中排列第一的预测模式与最优预测模式之间的强相关性,提出了一种基于模式分组的帧内预测模式快速选择算法,有效的降低了HEVC帧内预测算法的计算复杂度。实验表明本文所提出的算法与HEVC的测试模型HM10.0相比,在保证视频质量和码率基本不变的前提下(码率仅增加了0.78%,Y-PSNR只降低了0.12dB),减少了41.8％的编码时间,提高了编码效率。     

A compact photonic horizontal spot-size converter realized in silicon-on-insulator

We present a compact planar coupler connecting two optical waveguides with highly different widths. The coupler consists of various nonperiodic waveguide sections, whose dimensions are determined using a genetic optimization algorithm. Efficiencies that exceed those of the more conventional designs with similar lengths, like gradual linear tapers, were obtained in silicon-on-insulator using 248-nm-deep ultraviolet lithography.     

A soft-switching mode rectifier with power factor correction andhigh frequency transformer link

This paper presents a soft-switching mode rectifier (SSMR) consisting of a power factor correction zero-voltage-transition-pulse-width-modulated (PFC ZVT-PWM) converter and a high-frequency transformer-coupled DC/DC zero voltage switching clamped voltage (ZVS-CV) converter. An easily implemented ZVT soft-switching mechanism is developed to reduce the switching losses and stresses of the power switches in the PFC ZVT-PWM converter. The operations of the proposed SSMR in various modes are analyzed in detail and the associated governed equations are derived. Then accordingly, a quantitative design procedure is developed to find the values of soft-switching circuit components. In the control aspect, the dynamic model of the SSMR is derived and a current waveform controller is designed, such that sinusoidal line current with low harmonics and near unity power factor is obtained. Under this condition, a voltage controller is also designed for yielding good DC output voltage control characteristics. Validity of the designed SSMR is verified experimentally     

一种基于模数混合的强干扰抑制方法

本文提出了一种新型强干扰抑制方法。该方法通过改变接收机前端传统采样方式,以及自适应调整模拟端测量信号,可在采样前抑制强干扰,从而达到从大动态范围混合信号中分离出微弱目标信号的目的。理论分析与仿真都表明:当干扰信号功率与微弱目标信号功率差大于接收系统瞬时动态范围时,采用该方法可有效抑制干扰从而大幅提高微弱目标信号的采样精度。     

一种基于频控阵预编码的干扰抑制技术

目前阵列雷达目标探测技术大多依赖传统的相控阵技术,但其所产生的波束只与角度有关. 而近年来频控阵（frequency diverse array, FDA）的提出,使得波束不仅与角度有关还与距离和时间有关. 基于FDA技术,通过最大化接收信号的信噪比（signal-to-noise ratio, SNR）作为优化目标,提出了最优发射信号的预编码和FDA频偏的设计方法,从而把对其他无线设备的干扰降低到最小. 预编码的设计使得FDA的波束在目标处产生一个角度-距离维上的孤立点,而FDA的优化算法是基于一种变种的梯度下降法,通过回溯法线性搜索出最佳迭代步长. 数值仿真结果显示,该算法成功地在目标处产生了点状波束,且算法可在10次以内完成收敛,从而可以在角度-距离维进行干扰抑制.