提出求解有缓冲层的多层金属包层介质光波导的一个准解析方法，它应用渐近展开理论将传播常数展开成一个小参数的级数。这一方法本身是精确的，它能达到任意所需的精度，然而四层和五层波导结构的数值计算实例表明，仅二阶近似解就足够精确了。这一方法的优点是简单并且不同层数波导结构以及TE和TM模的解有相同的表达式形式。

In this paper we present an essentially analytic method for solving multilayer metallic optical waveguides using the asymptotic theory. The wave number is expanded into asymptotic series in terms of a small parameter. This method is exact and can approach any accuracy desired. However, the numerical results for four layer and five layer structures show that the second order solution is accurate enough. It is simple and has the same form of expressions for TE and TM mdes and different layer structures.