Improvements In Reflectometric Fibre Optic Hydrophones

The usefulness of optical fibre hydrophones, and their practicality in phased arrays, is critically dependent upon the technology and systems philosophy adopted for their implementation. Previous work has demonstrated the principles of pulsed ref lectometric techniques in this context, and modifications to the basic system have improved its performance in three respects: that of the acoustic design of the sensor, that of the optical loss budget, and that of the ambient noise performance. In the range of 100Hz to lkHz, the system noise has been reduced to below ambient sea noise under most conditions. The system has been demonstrated with 2.2km of fibre lead between the sensor head and the optical system, with no discernible loss of performance.