This is a course to introduce the students to a basic optical link. An optical link has three main components, each with a specific function. The transmitter contains a light source, e.g., a light‐emitting diode (LED), an edge‐emitting laser diode (LD), or a vertical cavity surface‐emitting laser (VCSEL) that converts an electrical current into an optical signal. The receiver contains a photodiode or a PIN photodiode that converts the light back into an electrical signal, an amplifier that makes the signal easier to detect and a discriminator that is able to recognize if the bit received is a low or a high. The fiber‐optic cable carries the optical signal between them. © 2003 American Institute of Physics