Modeling Light Transfer Through Optical Fibers for Illumination Applications.

A calculation model for light transfer through optical fibers was developed. The model consists of an analytical equation and a numerical algorithm. The numerical algorithm was written using the Monte Carlo ray tracing method. The algorithm allows the analysis of straight and bent optical fibers and provides losses due to critical angle and total Fresnel reflection as well as an average effective length for bound rays. A flexible format to represent bent fibers was used. This format permits several methods of representation for bent fibers. Thus, the program handles bent fibers of any shape and any representation. Both the random number generator and the Monte Carlo code were tested and found to be suitable for this research. The input flux was also modeled. A procedure was developed to handle input flux of any configurations. Thus, measured input flux can also modeled. The procedure is explained in detail and a method to calculate the efficiency of fibers is also presented. Experimental validation shows good agreement between the experimental and numerical results. The model was used to determine the losses through different bend radii and concentration values. It was found that the larger the bend radius relative to the radius of the fiber core the smaller the losses. Furthermore, for large values of bend radius relative to the radius of the fiber core a small change in that bend radius does not produce a significant change in the efficiency. Similarly, for highly concentrated emission, an increase in the concentration does not produce a significant change in the amount of losses. The effect of losses due to critical angle in bent fibers relative to straight fiber was found to be more significant for narrower beam spread.