Anisotropic metamaterial optical fibers: comment

Pratap et al. [Opt. Express23, 9074 (2015)10.1364/OE.23.009074] 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 (ε_r≠ε_z=ε_ϕ), the TE_z modes with E_z = 0 and TM_z modes with H_z = 0 could be decoupled, making Maxwell's equations separable. Contrary to their findings, our analysis demonstrates that under the specified condition (ε_r≠ε_z=ε_ϕ), the system cannot support the propagation of independent TE_z and TM_z 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.