Modal Squeeze in Depressed-Clad Photonic Crystal Fibers

We had presented a modal squeeze effect in dual-concentric-core photonic crystal fibers (DCC-PCF). The modal squeeze effect causes difficulty in achieving a single-mode operation in the DCC-PCF. In this paper, we verify that the modal squeeze occurs in depressed-clad photonic crystal fibers (DcPCF) too. And then three types of DcPCFs (Type A, B, and C) are used to be examples to show the relationship between the parameters of DcPCFs and severity level of modal squeeze, and the dispersion value. Base on the results of this work, one can appropriately trade the dispersion value off for achieving single mode operation. The numeric results indicate that, for DcPCF, the larger the dispersion coefficient, the harder the severity level of modal squeeze, and the more difficult the single mode operation is achieved.