Holography for underwater detection – HYDRE

The objective of the project HYDRE is to realize an optical sensor for the detection of underwater acoustic waves (optical hydrophone). The proposed sensor allows reaching high sensitivities and presents an intrinsically low frequency cutoff that permits to filter out the noise from the environment. HYDRE is a continuation of the MEDUSE project developed in the framework of the program ASTRID 2011. It will be based on the same approach originally demonstrated and validated under the initial project MEDUSE: the use of optical fibers in conjunction with adaptive holography.
Optical fiber hydrophones constitute an important technological breakthrough with respect to more conventional technologies, as those based on piezoelectric sensors. Actually, optical fiber sensors are electromagnetically immune, and do not require underwater electronics. Their very small diameter and reduced weight have a direct impact on the size of the torons, hence, on the size of the vessels required for their deployment (either local starting from a ship, or in coastal networks).
HYDRE will evolve from the initial prototype, realized on optical table in a demonstrative laboratory version, to a sensor integrated, transportable, operating at 1.55µm, calibrated and tested in media representative of the underwater application. The use of the optical fiber at 1.55µm will allow benefitting from the development of telecom components, and to combine multiple functions: sensor, multiplexing, remote sensing and signal transport. The optimization of the sensor will be realized in terms of sizing, holographic heart, calibration. HYDRE results will allow assessment of this technology for acoustic antennas.