Review on fibre-optic-based daylight enhancement systems in buildings

The lighting load can be reduced either by improving the efficiency of artificial lighting or by supplementing daylight to the building interiors with Innovative Daylighting Systems (IDS). Fibre optic daylighting system is an up-and-coming IDS that utilises direct and diffused sunlight to illuminate deep-plan buildings without location and orientation constraints. The system can benefit both building occupants and owners by attaining comfort conditions, improving productivity, saving cost and contributing to sustainable goals. This paper aims to review and summarise previous studies on fibre-optic daylighting system by categorising it into five individual subsystems: light-carrying optical fibre cable, suitable collectors, diffusers, fibre–collector interface and fibre diffuser interface. Each subsystem is reviewed and analysed based on its material property, geometrical parameters, output measurements and performance. The advantages and shortcomings of the types of optical fibre cable are explained after investigating the material characteristics and transmission efficiency parameters. Collectors used in conjunction with fibre cable are classified and analysed based on the principle, mode of study, design specification, concentration achieved and output performance. Diffusers at the fibre end used for even distribution of light have been studied to compare the sizing, spacing and output spectral characteristics. Additionally, the collector–fibre and fibre–diffuser interfaces have been reviewed. We conclude the paper by identifying the shortcomings of the system and giving some pointers towards gap in the literature that needs to be addressed to improve the system's present state and aid its widespread implementation.