Engineers and bankers measure efficiency differently; this is reasonable since their performance is measured differently. This analogy alludes to the many ways in which optical transmission and processing efficiency are measured. Efficiency is measured by the user, and can be optimized for one or a few metrics at once. It has been theoretically established that optical data transmission is more efficient than electrical data transmission, in units of energy per bit. Use of optical fiber and networking techniques open the potential of greatly increased speed and capacity. The telecommunications and computer industries are leading the way in use of new technology. The avionics industry follows, fulfilling more stringent environmental and reliability requirements. Inclusion of other types of constraints can sometimes confound observed efficiencies based solely on optical performance.