Investigation of microdeformation-induced attenuation spectra in a photonic crystal fiber.

We investigate both theoretically and experimentally the induced spectral attenuation in an all-silica photonic crystal fiber subjected to periodic axial microdeformations. The induced attenuation spectra show discrete attenuation peaks with a spectral position that is dependent on the period of the induced deformation. The peaks are assumed to be the result of mode coupling between the fundamental mode and a highly lossy higher-order mode. This assumption is verified through numerical calculation of the beat length between these two modes. Excellent agreement between experiment and numerical predictions of the spectral position of the attenuation peaks is obtained.