A photonic crystal fiber (O-PCF) with a novel structure consisting of five octagonal-shaped layers of circular air holes in the cladding region and two elliptical air holes in the core region is presented for application in different communication fields for terahertz (THz) wave propagation. The O-PCF fiber is investigated using perfectly matched layers by applying the finite element method. Based on the results of the simulations, the proposed O-PCF fiber shows a low effective material loss of 0.0162 cm⁻¹, a higher effective area of 5.88 × 10^–8 m², a core power fraction of 80%, a scattering loss of 1.22 × 10^–10 dB/km, and a confinement loss of 3.33 × 10^–14 dB/m in the target region of 1 terahertz (THz). Due to its excellent characteristics, the proposed O-PCF fiber offers excellent transmission characteristic across a broad band of the terahertz region. Moreover, the suggested O-PCF fiber will be ideal for use in the terahertz (THz) region for different kinds of optical communication and biomedical applications.