This paper describes an optoelectronic oscillator (OEO) capable of accepting CW light as input and providing radio-frequency (RF) carriers as output. To the best of our knowledge, we are the first to describe an easy-to-assemble and low-cost OEO that uses visible LED sources with a standard 1 mm diameter plastic optical fiber as part of the oscillation ring. The gain is solely provided by a transimpedance pre-amplifier integrated with a photodetector. Self-oscillations occurred. Fundamental frequencies in the 7.7-26.5 MHz range were generated, since the length of the fiber and the bias current feeding the LED are both correctly tuned. A comprehensive approach is used to explain the operation of the OEO. The proposed OEO may be didactically useful for use in research or teaching laboratories by untrained people.