基于色散光学的光波束形成网络

为了实现大波束指向范围和精细步进调节的光波束形成网络,采用了基于光学色散实现光真延时的方法.通过光开关实现N路高色散光纤路径切换获得大步进等延时差,实现了波束指向的大范围和大步进调节;通过调谐线性啁啾光纤光栅色散系数连续调谐获得小步进等延时差,实现了波束指向的小范围和小步进调节.结果表明,波束指向角度范围为-73.74...     

基于色散器件的光真延时线中的色散限制

利用强度-频率混合调制模型研究了基于色散器件的光真延时线中色散导致的延时误差的变化规律.基于对延时误差的分析,研究了色散对系统性能的限制,为光真延时线的设计提供了理论参考.     

相控阵天线中的光波束形成技术

光控相控阵的研究是相控阵天线研究的一个热点领域。本文介绍了相控阵天线中光波束形成的几个关键技术,以及天线扫描的控制、参考信号的产生和分配技术。     

宽带数字波束形成雷达的高精度延时补偿新方法

采用宽带信号的相控阵雷达可获得很高的距离分辨率,将广泛用于下一代多功能雷达系统中。传统窄带相控阵体制很难解决宽带相控阵雷达的空间色散和孔径渡越问题,尤其在宽带相控阵雷达做宽角扫描时,必须在阵元或子阵间使用精确的时延补偿。文中提出了一种实现高精度宽带相控阵延时补偿的新方法。该方法采用一种有效的可变分数延时滤波器新结构,即泰勒结构。该结构相对于传统的Farrow结构的主要优点是减少了乘法器和加法器的数量,降低了可变延时滤波器系数的计算难度。试验证明,新的方法能实现精确的宽带波束扫描,可应用于接收和发射数字波束形成的工程实现。     

基于高阶统计量的自适应非线性波束形成新算法

本文提出了一种新的基于高阶统计量的自适应非线性波束形成器，与常规的基于２阶相关矩阵自适应数字波束形成器相比，它的有效阵列孔径得到扩展，可抑制多于阵元数个有源干扰，对主瓣干扰抑制的性能及波束保形得到明显的提高，对阵元误差具有更强的容差能力。计算机仿真结果验证了这些结论。     

基于光子晶体光纤的宽带相控阵雷达多波束形成技术

提出了基于光子晶体光纤（PCF）的光学多波束形成网络,利用光子晶体光纤的高色散值和色散平坦特性实现了光学真延时（TTD）,并采用光波分复用技术形成了多个射频波束的独立控制和扫描。仿真结果表明,通过改变工作波长能够有效实现射频信号的相对延时,且延时差与理论计算值相符。     

色散管理和非线性管理控制光孤子群的传输

从描述光孤子传输的非线性薛定谔(NLS)方程出发,给出了色散管理和非线性管理的光孤子的传输方程,利用对称分步傅里叶方法对方程进行数值求解,模拟研究了色散管理和非线性管理控制光孤子在光纤中的传输演化特性。结果表明,只有色散管理控制光孤子群在光纤中的传输,随着传输距离增加,孤子间的相互作用逐渐加剧,如色散管理和非线性管理同时控制光孤子群在光纤中的传输,可极大地抑制孤子间的相互作用,且随着距离增加相邻孤子间的作用几乎不变,这一结果可应用于光孤子群远距离的传输。     

光控相控阵波束接收网络

文中提出了一种基于光纤色散真时延技术的光控相控阵雷达多波束接收网络。该网络制作原理是根据光纤的色散特性,主要由密集波分复用器(DWDM)和光纤延时模块构成。DWDM 实现对多通道光合成,多个光开关和光纤延时环组成的光纤延时模块实现对合成的多路光载波进行延时量调节,从而实现波束扫描。依据原理方案,研制了一套16通道光接收、双波束形成网络,实现从-40°到+45°的16个不同波束指向扫描,切换速度≤30us。暗室测试证明了其波束形成能力。     

超短光脉冲在高阶非线性色散介质中的波群分解法

本文给出非线性介质中超短光脉冲传输时计及二阶色散的波群分解法，并在不同ＳＰＭ、ＧＶＤ及啁啾条件下作了详细推导和讨论，在振幅极值、延时和波群频率三维表象中，描述脉冲传输的振幅包络具有明确的物理图像。该法亦可用于数值计算中。     

Coherent optical beam forming with passive millimeter-wave arrays

Passive millimeter-wave imaging requires large apertures to achieve an angular resolution comparable to that of typical infrared imagers. Aperture synthesis offers a route to achieving high resolution without using a single large aperture, by interferometrically combining the signals from a number of smaller distributed apertures. In such a system the individual millimeter-wave signals must be transported to a common location with good phase fidelity and combined to form the image. This paper discusses a technique called coherent optical beam forming which performs optical transport of the up-converted millimeter-wave signal and direct image formation at the optical frequency. Proof of principle experiments are described that demonstrate coherent optical beam forming with a point source and a method of self-calibrating the array to remove phase errors     

Mode dispersion and delay characteristics of optical waveguides using equivalent TL circuits

A new analysis leading to an exact and efficient algorithm is presented for calculating directly and without numerical differentiation the mode dispersion characteristics of cylindrical dielectric waveguides of arbitrary refractive-index profile. The new algorithm is based on the equivalent transmission-line (T-L) technique. From Maxwell's equations, we derive an equivalent T-L circuit for a cylindrical dielectric waveguide. Based on the TL-circuit model we derive exact analytic formulas for a recursive algorithm which allows direct calculation of mode delay and dispersion. We demonstrate this technique by calculating the fundamental mode dispersion for step, triangular, and linear chirp optical fiber refractive index profiles. The accuracy of the numerical results is also examined. The proposed algorithm computes dispersion directly from the propagation constant without the need for curve fitting and subsequent successive numerical differentiation. It is exact, rapidly convergent, and it results in savings for both storage memory and computing time.     

Impedance behaviour and scan performance of microstrip patch arrayconfigurations suitable for optical beam forming networks

The authors propose two microstrip array configurations suitable for integration with optical beam forming networks. Rigorous full wave analyses of both array configurations, based on the spectral domain technique and incorporating accurate modelling of the coaxial feeds are implemented to investigate the impedance behaviour, scan performance, beam efficiency and cross polarization levels of each proposed array     

基于全光波长变换和色散介质的可调谐光延迟线

对基于四波混频全光波长变换与色散介质组合的可调谐光延迟线进行了实验研究。将420m长的高非线性光纤(HNLF)分别与普通单模光纤(SMF)和色散补偿光纤(DCF)组合,依次实现了1ns和3ns的可调谐光延迟,实验结果与理论结果非常一致。     

Parabolic-array beam forming for nonsinusoidal waves

A beamforming method for nonsinusoidal waves using parabolic arrays is described. Antenna patterns for rectangular and sinusoidal pulses are given. Patterns for radiated signals with arbitrary time variations are shown to be derivable through function approximation by sums of linear ramp functions. In addition, the related far-field transient of signals that are zero for t<0 and have an arbitrary time variation for t⩾0 is described. A number of computer simulations are also given     

Nonlinear dynamics of femtosecond optical solitary wave propagationat the zero dispersion point

A perturbed nonlinear Schrodinger equation, describing nonlinear pulse propagation of femtosecond duration in optical fibers at the zero dispersion point, is considered. This equation is reduced to an ordinary differential equation, which is treated by means of Hamiltonian dynamics techniques. Conditions for solitary wave formation, as well as the solutions themselves, namely, a bright soliton, a rarefaction soliton, and a pair of dark solitons, are derived analytically. The shifts of the solitary wave velocity, the angular frequency, and the wavenumber, as well as the peak power required to launch a bright soliton are also obtained. The connection among the point initial conditions of the pulse and the type of solitary wave that can be excited is finally presented     

Nonlinear influence on PM-AM conversion measurement of groupvelocity dispersion in optical fibres

The authors propose a method for measuring the group velocity dispersion, including the polarity, of optical fibre by using a single wavelength light source. The method is based on the interplay between phase modulation-amplitude modulation (PM-AM) conversion and self-phase modulation (SPM)     

高功率激光作用下光学元件非线性热效应研究

为了研究高功率激光作用下光学元件热效应的非线性特性对光束质量的影响, 基于热传导、热弹性力学、物理光学等基础理论, 采用有限元分析方法, 进行了高功率连续激光(功率密度约为500kW/cm2)作用下光学元件的温度场和位移场的计算; 分析对比了各个参数的非线性特性对光学元件热效应的影响; 探讨了不同材料、不同形状光斑辐照下的光学元件非线性热效应。结果表明, 高功率连续激光作用下光学元件所反映出的热学、力学和光学吸收存在着不同程度的非线性效应, 其强弱取决于光学元件材料、光斑形状等因素; 高斯激光辐照熔石英样品且吸收率为100×10-6时, 考虑物性参数和温度边界条件的非线性, 会引起表面最大温升16%的相对误差和表面变形峰谷值10%的相对误差。这一结果为开展与此相关的研究提供了一些新思路。     

发射波束部分阵元置零综合分析

针对选择阵列部分单元控制的情况,分析了发射波束零点形成的两种方式,即部分阵元的幅相加权综合和部分阵元的唯相位综合加权方式。通过对这两种置零综合的算法研究和仿真分析,并从形成零陷的深度及对副瓣扰动等方面,比较了这两种发射波束置零综合方法的性能。     

Nonlinear optical glasses for ultrafast optical switches

In this paper we report degenerate four-wave-mixing measurements of the nonlinear coefficient of rutile and a number of optical glasses at 1.06 μm. We define a figure of merit which measures the suitability of a material for nonlinear waveguide switches and show that the best glasses have figures of merit substantially higher than any other material. We include a brief discussion of the types of switching elements that could be made with these materials.