Résumé
The goal of this presentation is to provide first results concerning the optical noise of a fiber laser used as an underwater acoustic sensor: hydrophone. The main sensor characteristics are: (1) A sensitivity allowing to detect all noise levels above background sea noise (the so-called deep-sea state 0). Among other applications, one may mention: seismic risk prevention, oil prospection, ship detection, etc. (2) An optical noise reduced to its minimal value: it is the lower bound below which no acoustic pressure variation is detectable.We therefore present here the first results for the expected sensitivity of the acousto-optic sensors, the frequency and amplitude of optical noises induced by the fiber laser and all the devices on the optical line. These results exemplify the possible detection of signal levels as low as the deep-sea state noise 0, especially for low frequency bandwidths, from several Hertz up to several kiloHertz.