Considering disadvantages of artificial lighting, e.g. huge amount of energy consumption and undesirable physical effects on human body, and advantages of sunlight, application of sunlight, especially in offices is desirable, therefore investigation on sunlight conveying will be useful. Previous studies have shown the potential of optical fibers for this purpose. Optical fibers are easy to install and flexible in comparison with solar tubes and mirrors. In this project, we try to design a simple and inexpensive system for sunlight transmission. For this purpose, a set up has been made which comprises a convex lens of low-focal length to collect light, optical fiber(s) for light transmission, a structure to locate lens and optical fibers and a dark box for measuring the light being transferred by. The performance of optical fiber is based on the total internal reflection (TIR) process that lets light transmit along the fiber. The two most important variables for optical fibers are defined as numerical aperture (NA) and attenuation along their length (?). Numerical aperture refers to an angle that light can be transmitted along the fiber with total internal reflection. Optical fiber attenuation depends on fiber’s material and its defects. Two lenses of 32 and 42 mm in diameter were used to compare the performance of Concentrators. Also, the effect of fiber length on light transmission, fibers of 1 and 1.5 mm in diameter were examined. In order to track the sun, a manually controlled two axis solar tracker was made and employed. For performance calculations, energy and exergy analysis were applied on the system from the lens’s input to the optical fiber output. Then to assess the validity of the equations, different tests were done. The system variables, i.e. fiber length, fiber diameter, number and sharpness of the optical fiber, diameter and the focal length of the lenses and the influence of the sun's energy intensity were studied. To eliminate the influence of other variables on the tests results, the variable sunlight illumination ratio (SIR) which is defined as the ratio of illumination at the test box to the outdoor illumination on a flat horizontal surface, was used. Also, luminous efficacy and irreversibility were calculated. Luminous efficacy is defined as the ratio of output luminance to the output power of the optical fiber. In addition, difference between exergy of lens input and optical fiber output offers irreversibility. Increasing length, number of optical fiber bends and reduction in diameter can result in increase in the loss in the system. By increasing the diameter of the lens a significant increase in the amount of light energy occurs and also changes in the size of focal diameter that leads to the difference between the area of fibers cross section and focal point causes decrease in the output luminous of the system. Luminous efficacy increases with increasing the number of optical fibers. Additionally, total irreversibility will increase when the optical fiber’s length and diameter of the lens increases. Due to the variables luminous efficacy and output luminance of the system at several experiments, the bigger lens, the optical fiber with larger diameter and greater number of them can be selected as the optimal system. Keywords: Sunlight Transmission, Optical Fiber, Exergy Analysis, Energy Analysis.