Optical conductivity study of mixed-valent quasi-one-dimensional <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>CeIr</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">B</mml:mi> <

We present a combined theoretical and experimental study on the optical conductivity of ${\mathrm{CeIr}}_{3}{\mathrm{B}}_{2}$, where quasi-one-dimensional Ce chains form along the $c$ axis of the monoclinic crystal. Significant hybridization-induced features are observed along the Ce chains by broadband infrared spectroscopy, demonstrating mixed-valent behavior over a wide range of temperatures (6--300 K) and energies (up to 0.8 eV). The ferromagnetic transition at 41 K had no noticeable influence on the temperature evolution of the optical conductivity. A comparison with density functional theory plus dynamic mean-field theory calculations demonstrates the quasi-one-dimensional nature of ${\mathrm{CeIr}}_{3}{\mathrm{B}}_{2}$ and the local character of the interactions responsible for the electronic renormalization. Furthermore, we demonstrate how the spectroscopic signatures of this mixed-valent compound are captured by theory, providing a clear distinction from the response expected in the integer-valent Kondo regime.