Design of Optimization Method for Light Energy Utilization in Fiber Optic Day-lighting System

【Objective】Effectively collecting sunlight and transmitting it through optical fibers to illuminate areas that require lighting can replace some traditional light sources. The fiber optic day lighting system is significantly affected by the angle of incident light and the coupling efficiency of incident light. In order to improve the light energy utilization of the fiber optic day lighting system, it is necessary to optimize and improve it from two aspects: self-alignment of sunlight direction and improving the coupling efficiency of spatial light to the fiber optic.【Methods】A fiber optic probe structure is designed to address the issue of real-time alignment of sunlight, targeting the nonlinear response of zenith angle. It is used to track the direction of sunlight incidence and control the orientation of the lighting structure through an adaptive mechanical structure. Due to the use of multiple fiber optic probes, the corresponding testing angle is pre-fixed, solving the problem of uneven variation of solar intensity with zenith angle. Meanwhile, the combination of multiple fiber optic probes can significantly improve the detection field of view, ensuring consistency in testing accuracy throughout the entire time period. Addressing the issue of coupling efficiency from space light to optical fibers, a dual-lens structure and fiber-optic spherical end-face encapsulation have been designed to enhance the effective numerical aperture of the optical fiber, significantly expanding the angular range of incident light.【Results】The influence of radius modulation ratio and fiber spherical radius on coupling efficiency is simulated and analyzed. The simulation results show that when the radius modulation value is 0.61 and the fiber spherical radius is 228.75 μm, the coupling efficiency reaches its maximum value. The experiments are conducted to test and analyze the coupling efficiency and illuminance. The experimental results show that when the focal length f of the second lens is 8.0 mm, the maximum optical power reaches 352.14 mW. The optical power attenuation of the spherical end face structure within 8° is less than 5%, which is significantly better than the traditional planar end face structure. On sunny days, the average illumination of the spherical end face fiber is 10 392 lx, and the light energy conversion rate during the entire period is 38.82%. The planar end face type is only 23.69%.【Conclusion】This system is improved and optimized in the two main aspects of solar azimuth detection and spatial optical coupling to optical fibers. Simulation analysis and experimental results have verified the feasibility of the system design. From the perspective of light stability and light energy conversion rate, this design can further improve the system's light energy utilization efficiency without changing the outer diameter size.