US 4,525,818 A · Stable fiber-optic hydrophone

Abstract

An optical fiber hydrophone system in which a single optical fiber is used for all of the acoustical sensors in the system. A signal source and detector provides an optical signal in selected form, such as continuous or pulsed and detects and extracts an identifiable output signal. Each sensor is in the form of a sensing portion of the single optical fiber. Each sensing portion includes two optical reflectors separated one from another by a predetermined length of said optical fiber. Variations in acoustical pressure incident on the sensing portion causes a change in the predetermined length. This causes reflected portions of the optical signal to interfere with one another. Such interference is detectable for extraction of the identifiable output signal. In one form each sensing portion has two terminal branches of a mechanically deformable material, deformable in response to the fluctuations in acoustical pressure. Preferably, the optical fiber has two portions, a sensing portion thereof underwater and having a first optical cavity, and another portion thereof on board a vessel and having a second optical cavity, typically tunable with respect to the optical length thereof to maximize the interference in the detected optical signal.

Claims17

Dependent claims

An optical fiber hydrophone system adapted to process variations in local acoustical pressure in a fluid body and provide an identifiable output signal, comprising:

signal source and detecting means for providing an optical signal in a selected form, and for detecting and extracting said indentifiable output signal;
a single optical fiber connected at one end to said source and detecting means and operable for conducting optical signals from said source and to said detecting means;
a sensing means in said optical fiber remote from said source and detecting means, said sensing means being adapted for immersion in said body and including two optical reflector means incorporated into said fiber and spaced one from the other by a predetermined length of said optical fiber, at least one of said reflector means being partially reflective and partially transmissive, said variations in acoustical pressure incident on said sensing portion causing a change in said predetermined length thereof and thus a phase and intensity modulation in the portion of said optical signal reflected back and forth between said two optical reflector means and,
means connected to said source and detecting means for processing the intensity modulated optical signal transmitted back to said source and detecting means in said optical fiber for extraction therefrom of said identifiable output signal.

1 more element

Dependencies are inferred from the claim text.

Stable fiber-optic hydrophone

Life of this patent

Stable fiber-optic hydrophone

Life of this patent

Abstract

Claims17