This document provides information on active devices used for avionics fiber optic applications. The main body of the document begins with the scope and rationale. It continues with a technology introduction to optoelectronic active devices and then a selection guide that would enable a system design engineer to use the documents in the Fiber Optics series to select or specify suitable optoelectronic active devices for avionics applications. The main document also includes environmental guidelines for active devices to be used in avionics applications. These are included as guidance for commercial aircraft use and are included with the caveat that the requirements of any particular aircraft platform or customer would supersede these generic guidelines.