4. Towards Next-Generation OAM Fibers: Inverse Raised Cosine Few-Mode Fiber: Design and Performance Evaluation

This chapter delves into the design and performance evaluation of the Inverse Raised Cosine Few-Mode Fiber (IRC-FMF), a novel optical fiber designed to enhance data transmission capacity and spectral efficiency. The text begins with an introduction to the increasing demand for high-capacity optical communication systems and the role of space division multiplexing (SDM) in meeting this demand. The chapter then focuses on the design methodology of the IRC-FMF, highlighting its unique refractive index profile and the incorporation of the raised cosine function from digital filters. A detailed modal analysis is performed, examining the number of supported modes, modal separation, and the impact of various fiber parameters. The chapter also assesses the quality of supported Orbital Angular Momentum (OAM) modes, including their purity and intrinsic crosstalk. Performance metrics such as differential group delay (DGD), chromatic dispersion, effective mode area, and nonlinearity are evaluated across the C and L communication bands. The resilience of the IRC-FMF to structural perturbations like ellipticity and birefringence is analyzed, along with the effects of bending on mode count, separation, walk-off behavior, and bending-induced losses. The chapter concludes by comparing the IRC-FMF with other OAM fibers and discussing its potential applications in next-generation optical communication systems. This comprehensive analysis provides valuable insights into the IRC-FMF's capabilities and its potential to revolutionize optical networking.