对ITU-T G.654E光纤的传输性能进行了研究,总结了该类型光纤的一些新的特性。研究结果表明,G.654.E光纤的品质因子(FOM——Figure of merit)比常规G.652光纤高3 d B左右,实际400G系统测试结果显示G.654.E光纤比G.652光纤的传输距离提升...对ITU-T G.654E光纤的传输性能进行了研究,总结了该类型光纤的一些新的特性。研究结果表明,G.654.E光纤的品质因子(FOM——Figure of merit)比常规G.652光纤高3 d B左右,实际400G系统测试结果显示G.654.E光纤比G.652光纤的传输距离提升60%以上。同时也讨论了配有拉曼放大器的传输系统工作在G.654.E光纤(泵浦光工作在光纤截止波长以下)时出现的新特性。展开更多
The Galerkin and least-squares methods are two classes of the most popular Krylov subspace methOds for solving large linear systems of equations. Unfortunately, both the methods may suffer from serious breakdowns of t...The Galerkin and least-squares methods are two classes of the most popular Krylov subspace methOds for solving large linear systems of equations. Unfortunately, both the methods may suffer from serious breakdowns of the same type: In a breakdown situation the Galerkin method is unable to calculate an approximate solution, while the least-squares method, although does not really break down, is unsucessful in reducing the norm of its residual. In this paper we first establish a unified theorem which gives a relationship between breakdowns in the two methods. We further illustrate theoretically and experimentally that if the coefficient matrix of a lienar system is of high defectiveness with the associated eigenvalues less than 1, then the restarted Galerkin and least-squares methods will be in great risks of complete breakdowns. It appears that our findings may help to understand phenomena observed practically and to derive treatments for breakdowns of this type.展开更多
文摘对ITU-T G.654E光纤的传输性能进行了研究,总结了该类型光纤的一些新的特性。研究结果表明,G.654.E光纤的品质因子(FOM——Figure of merit)比常规G.652光纤高3 d B左右,实际400G系统测试结果显示G.654.E光纤比G.652光纤的传输距离提升60%以上。同时也讨论了配有拉曼放大器的传输系统工作在G.654.E光纤(泵浦光工作在光纤截止波长以下)时出现的新特性。
基金Supported by National Natural Science Foundation of China(60778041)Graduate Research and Innovation Program of ordinary university of Jiangsu(CXLX13 390)Hezhou college scientific research projects(2011ZRKY06 and 2012ZRKY04)
文摘The Galerkin and least-squares methods are two classes of the most popular Krylov subspace methOds for solving large linear systems of equations. Unfortunately, both the methods may suffer from serious breakdowns of the same type: In a breakdown situation the Galerkin method is unable to calculate an approximate solution, while the least-squares method, although does not really break down, is unsucessful in reducing the norm of its residual. In this paper we first establish a unified theorem which gives a relationship between breakdowns in the two methods. We further illustrate theoretically and experimentally that if the coefficient matrix of a lienar system is of high defectiveness with the associated eigenvalues less than 1, then the restarted Galerkin and least-squares methods will be in great risks of complete breakdowns. It appears that our findings may help to understand phenomena observed practically and to derive treatments for breakdowns of this type.
