Analysis of the Performance of a Pressure-Tolerant Light-Emitting Diode/Fiber Optic Cable Interface

A critical element of a pressure-tolerant fiber optic sonar link (FOSL) is the pressure tolerant electronic (PTE) light-emitting diode (LED)/fiber optic cable interface. The term PTE denotes that the interface is capable of meeting performance specifications without the use of a pressure vessel while exposed to hydro- static and hydrodynamic pressures external to the sub- marine hull. The paper begins with a description of the FOSL system and its requirements as well as a discussion of the PTE environmental requirements. The present PTE technology base is assessed briefly for its adequacy in meeting PTE FOSL system requirements. The design of the PTE LED/fiber optic inter- face was optimized by selecting the design with the best expected performance estimated by calculating total power coupled. The effects of temperature and pressure on the total power coupled were analyzed and compared with experimental measurements of power coupling at pressures up to 2 klbf/in.² gauge. It was concluded that the performance of a properly designed interface should be enhanced during operation under PTE conditions.