<b>Development of optical fiber Light-Transmitting Concrete (LTC):</b> <b> A narrative review.</b><b></b>

Light-transmitting concrete (LTC) containing optical fibers allows natural light to pass through structural elements while maintaining the mechanical characteristics of conventional concrete. This property offers potential applications in energy-efficient buildings, architectural façades, pavements, and infrastructure where daylight utilization is desirable. The present narrative review summarizes published research on optical fiber light-transmitting concrete, focusing on material composition, fabrication methods, optical performance, mechanical properties, durability, and microstructural characteristics. Evidence from previous studies indicates that light transmission in LTC is strongly influenced by fiber parameters such as volume fraction, diameter, and spacing. Increased fiber content generally improves light transmittance, whereas larger fiber diameters and wider spacing tend to reduce transmission efficiency. Mechanical properties, particularly compressive and flexural strength, depend on the interaction between optical fibers and the cement matrix, where weak interfacial bonding and increased porosity may affect structural performance. Durability aspects, including water absorption, permeability, and environmental exposure, remain insufficiently investigated in the existing literature. Although optical fiber LTC demonstrates promising architectural and energy-saving applications, challenges remain in fabrication complexity, cost, and long-term durability. Future research should address fiber–matrix interfacial behavior, standardized testing methods for optical performance, and optimization of fiber parameters to balance structural strength with light transmission efficiency.