What are the light sources that transmit signals in optical fiber communication cables

Fiber optic transmitters convert electrical signals into optical signals and then inject these optical signals into light- conducting cable. They use light emitting diodes (LED) or laser diodes as their optical source, and are designed for use with either single-mode or multi-mode. The four main types of optical sources are LEDs, Fabry-Perot (FP) lasers, Distributed Feedback (DFB) lasers, and Vertical Cavity Surface-Emitting Lasers (VCSELs). LEDs are tiny semiconductor devices. Fiber-optic communication systems require a light source to generate the signal that the fiber transmits. [pdf]