All-optical hydrophone that is not sensitive to temperature or static pressure

Abstract

The invention consists of: an optical hydrophone; and a fiber-optic element which forms a laser cavity and is housed inside a mechanical structure comprising an open rigid cylindrical body that defines a cavity containing a fluid, in which cavity the fiber-optic element is housed, said rigid body being sealed at the ends thereof by means of two stoppers that keep the fiber-optic element permanently under tension in a longitudinal rectilinear position inside the cavity. The stoppers are configured such as to: deform when the external pressure varies, thereby varying the length of the fiber-optic element; and deform when the temperature varies, thereby varying the length of the fiber-optic element and compensating for the variation experienced by the element as a result of the temperature variation. The mechanical structure also includes one or more openings that allow the static pressures to be balanced.

Description

technical field [0001] The present invention relates to the general field of underwater acoustic transducers or hydrophones. In particular, the invention relates to optical hydrophones based on fiber lasers. Background technique [0002] With regard to the production of underwater acoustic transducers, the use of optical fibers is a known solution that exhibits recognized advantages, including above all the small size of the hydrophones produced with such technology, and the ability to produce The possibility of an ensemble of hydrophones by multiplexing on the same optical fiber the pressure change information detected by the individual hydrophones making up the ensemble of hydrophones, wherein each Hydrophones are associated with a given wavelength. [0003] However, in order to obtain a sensitivity sufficient to be able to detect very low levels of acoustic signals (usually levels below sea state noise 0 on the knudsen scale), it is known that the passage pressure The ...

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Problems solved by technology

[0012] However, there is DSP (density spectral power) about the intrinsic noise of the laser which limits the noise of the demodulation system ( to the order of 1 kHz), the axial deformation caused by the sound pressure applied directly to the outer surface of the laser cavity is insufficient to obtain a hydrophone sensitivity compatible with levels less than sea state noise 0

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