5. Inverse Gaussian Fibers for Future OAM-MDM-WDM Optical Networking Systems

To meet the growing demand for transmission capacity and spectral efficiency in optical communication systems, significant attention has shifted toward utilizing the orbital angular momentum (OAM) of light for information encoding and transmission through optical fibers. This trend has spurred the development of advanced specialty fibers tailored to support OAM channels with improved performance characteristics. In this chapter, we focus on a class of optical fibers specifically engineered for OAM mode propagation. We examine various design approaches and review recent advancements in this area. Furthermore, we introduce our custom-designed OAM-supporting fibers, inverse Gaussian fibers (IGFs). A comprehensive numerical investigation is carried out to analyze the key structural and optical parameters of IGFs that enable stable OAM mode guidance. We propose and optimize four IGF configurations that demonstrate enhanced intermodal separation, achieving a minimum effective refractive index difference of \(\varDelta n_{eff} = 2.74 \times 10^{-4}\). This large separation helps suppress unwanted mode coupling and significantly reduces inter-channel crosstalk. Additionally, we evaluate the transmission characteristics of the designed IG-FMFs in terms of differential group delay and chromatic dispersion across the ITU-T C\(+\)L wavelength bands. Comparative results reveal that our IGF designs offer superior performance relative to state-of-the-art specialty fibers, positioning them as strong candidates for future high-capacity optical communication networks incorporating wavelength-division multiplexing (WDM). This chapter aims to provide valuable insights and serve as a stimulus for further research and development within the optical fiber design community.