40Gbit/s相干偏振复用QPSK传输中基于 Manakov方程的非线性补偿

在40 Gbit/s相干偏振复用正交相移键控(QPSK)传输系统中,为了补偿由于光纤中非线性效应引起的传输信号损伤,采用了基于Manakov方程的反向传播非线性补偿算法.传统的基于标量非线性薛定谔方程(NLSE)的反向传播算法忽略了偏振模色散(PMD)的作用,因此在偏振复用系统中不能补偿由于PMD引起的信号损伤;而基于...     

基于优化电子散斑光谱的三维物体测量研究

用激光光束直接照射到测试表面,再用CCD采其变形前后表面散斑颗粒干涉形成的条纹,条纹图解析为测量点的位移量和变形量,进而得到其离面位移,在优化算法的时候采用π位相技术获取另一个π相移的变形条纹图像,将面内位移与离面位移分离,为了消除零级分量,让投影光栅移动1/2个周期.通过Matlab和四步位相算法给出了三维空间模型,得出变形后物体的离面位移数据.实验仿真数据表明其能够稳定地测量物体变形场三维分量,误差较低.     

Point source equilibrium problems with connections to weighted quadrature domains

We explore the connection between supports of equilibrium measures and quadrature identities, especially in the case of point sources added to the external field $Q\left(z\right)={\left|z\right|}^{2p}$ with $p\in \mathbb{N}$. Along the way, we describe some quadrature domains with respect to weighted area measure ${\left|z\right|}^{2p}d{A}_z$ and complex boundary measure ${\left|z\right|}^{?2p}dz$.     

Bypassing the quadrature exactness assumption of hyperinterpolation on the sphere

This paper focuses on the approximation of continuous functions on the unit sphere by spherical polynomials of degree n via hyperinterpolation. Hyperinterpolation of degree n is a discrete approximation of the $L^2$-orthogonal projection of the same degree with its Fourier coefficients evaluated by a positive-weight quadrature rule that exactly integrates all spherical polynomials of degree at most 2n. This paper aims to bypass this quadrature exactness assumption by replacing it with the Marcinkiewicz–Zygmund property proposed in a previous paper. Consequently, hyperinterpolation can be constructed by a positive-weight quadrature rule (not necessarily with quadrature exactness). This scheme is referred to as unfettered hyperinterpolation. This paper provides a reasonable error estimate for unfettered hyperinterpolation. The error estimate generally consists of two terms: a term representing the error estimate of the original hyperinterpolation of full quadrature exactness and another introduced as compensation for the loss of exactness degrees. A guide to controlling the newly introduced term in practice is provided. In particular, if the quadrature points form a quasi-Monte Carlo (QMC) design, then there is a refined error estimate. Numerical experiments verify the error estimates and the practical guide.