High sensitivity, pressure compensated optical hydrophone

Fiber optic sensor systems are a key element in the Navy's plan for meeting cost, reliability and performance objectives for future towed and fixed arrays. A cost effective optical hydrophone that provides performance over the full operating environmentis needed to meet future requirements and mitigate technical risk in several ongoing development programs. Multiple candidate designs are presented that overcome limitations in current optical hydrophones with a minimal increase in overall complexity.Additionally, pressure compensated solutions are described which maintain compatibility with thin line towed array design constraints. These candidate implementations will be fully evaluated during phase 1 efforts. Engineering evaluation includesmodeling, analysis, prototype fabrication and in water tests to quantify trade offs early in development. Consideration of application specific derived requirements including sensor interrogation methods, optical noise floor performance, durability duringhandling, insensitivity to vibration and compatibility with automated array manufacturing techniques are also critical to ensure a successful integration into current development projects such as the fiber optic TB-29 thin-line towed array. The range ofalternatives identified provides increased sensitivity over the entire range of operating environments resulting in suppression of other noise mechanisms inherent in optical sensor systems. The primary benefit is improved sensor sensitivity resulting insuppression of noise mechanisms that may limit fiber optic sensor performance. This performance benefit is achieved while maintaining compatibility with physical packaging constraints and production cost objectives. The higher sensitivity hydrophone willmake all optical interrogation systems more practical and will have application in both towed and fixed arrays used by the Navy and the seismic industry.