The normalized propagation constant, which determines the number of the modes and mode cutoff is obtained for a PCF: with a certain structure parameters.

对于给定结构的PCF，计算得到了决定模式数量及模式截止的归一化传播常数。

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The index of the core is a little smaller than that of the cladding base material, so the fundamental mode loss of short wavelength increases rapidly and leads to the mode cutoff.

这种光纤的纤芯折射率比包层基质折射率小，所以短波长时基模损耗迅速增大，使得光传输截止。

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The index of the core is a little smaller than that of the cladding base material, so the fundamental mode loss of short wavelength increases rapidly and leads to the mode cutoff.

这种光纤的纤芯折射率比包层基质折射率小，所以短波长时基模损耗迅速增大，使得光传输截止。

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