Form factor of a planar light source and its application in optical fiber
光斑的形状因子及其在光纤定解问题中的应用

By comparing the radiation field excited by a multipole point source with that excited by a cylindrical planar light source,the form factor of the planar light source is defined.The form factor is determined by the distribution of the source strength on the plane.A general formula for form factor is obtained,and several examples of form factor are given.Introduction of form factor in fiber optics completes the formulation of the boundary value problem.The influences of the distribution of the source strength to the modes propagating in a fiber are discussed briefly by using the form factor.