Anisotropic metamaterial optical fibers: comment

Pratap et al. [Opt. Express 23, 9074 (2015)] examined the propagation characteristics of electromagnetic waves in an anisotropic optical fiber with concentric inner and outer surfaces acting as perfect electric conductors. Their study concluded that when the permittivities satisfy the condition (sr not equal sz = s phi), the TEz modes with Ez = 0 and TMz modes with Hz =0 could be decoupled, making Maxwell's equations separable. Contrary to their findings, our analysis demonstrates that under the specified condition (sr not equal sz = s phi), the system cannot support the propagation of independent TEz and TMz modes. As a result, the conclusions drawn by Pratap et al. are incorrect and lack physical validity. This correction is essential for accurately designing and applying metamaterial-based optical fibers, particularly in advanced photonic and communication systems.