In this paper we present the design of an optical transmission system, using plastic optical fiber (POF), which operates in the visible range of the electromagnetic spectrum. The optical signals are generated by modulated visible LEDs, transmitted through POF and at the reception end a pin-pin photodetector is implemented. A computer simulation tool dedicated to the analysis of optical circuits was used for preliminary analysis of the optical system. The performance of the optical link was analyzed by BER prediction variation on the transmission rate. The tested optical system was assembled using high efficiency LEDs of the same wavelengths, a commercial POF and a pin-pin photodetector based on a-SiC:H/a-SI:H. This detector behaves as an optical filter with controlled wavelength sensitivity. Different optical signals, obtained by adequate modulation of LED optical sources, were coupled into the POF and the combined optical signal at the fiber termination was directed onto the photodetector active area. The output photocurrent was measured with and without optical bias. Results compare the use of a pin-pin transducer device in free space and in a POF transmission link.