This document draws from, summarizes, and explains existing broadly accepted engineering best practices. This document defines the process and procedure for application of various best practice methods. This document is specifically intended as a standard for the engineering practice of development and execution of a link loss power budget for a general aerospace system related digital fiber optic link. It is not intended to specify the values associated with specific categories or implementations of digital fiber optic links. This document is intended to address both existing digital fiber optic link technology and accommodate new and emerging technologies. The proper application of various calculation methods is provided to determine link loss power budget(s), that depend on differing requirements on aerospace programs.