Military avionics optical fiber data buses with active-coupler configurations

Military avionics optical fiber data buses of high reliability are discusse d in this paper. Because Light Emitting Diodes (LED's) have better temperat ure performance and require less complex driver circuits than laser diodes, the former is normally chosen as an optical source in the severe aircraft environment at present. In this case, optical power budget becomes a critic al factor which can significantly limit the number of terminals in a data b us. To effectively solve this problem while maintaining a high reliability, we present several configurations of all-active couplers and hybrid passiv e/active couplers for avionics optical fiber data buses using PIN photodiod es and LED's, The system design is also described, which incorporates a mod ulation scheme called Partial Trilevel Manchester II Pi-Phase Coding.