Taking the circularfibres for the example, the first order correction local field and field shift in the fundamental mode peak field are discussed.
以圆光纤为例，讨论了一阶近似本地场形式及基模场在最大值处的场位移。
2
The cross section of the fibres changes from kidney shaped to circular. This is because the fibres swell markedly when treated with a concentrated sodium hydroxide solution.