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US 7,116,850 B2Granted
Hydrophone mandrel for precise placement of gratings
AssigneeWeatherford/Lamb, Inc.
InventorDaniel Ming Kwong Woo
Life of this patent
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Abstract
A method and apparatus for reducing the difficulty of controlling the length of a section of optical waveguide wrapped around a mandrel separating Bragg gratings forming an interferometric sensor are provided. The section of optical waveguide may be wrapped on a mandrel having at least two different outer diameters. The mandrel may also include one or more bores for receiving and protecting the Bragg gratings.
Claims23
An interferometric sensor comprising:
- a mandrel having a first portion with a first diameter and a second portion with a second diameter;
- two Bragg gratings formed in an optical waveguide;
- and
- a section of optical waveguide between said Bragg gratings with the section defining an interferometric path length to enable sensing acoustic pressures impingent on the mandrel, wherein said section of optical waveguide is wound on said mandrel such that a length of the optical waveguide section is determined by a number of turns wrapped around each of the first and second portions.
1 more element
An acoustic sensing system comprising:
- a source for generating light pulses;
- an acoustic sensor having two Bragg gratings separated by an optical waveguide section wrapped around a mandrel with a first portion with a first diameter and a second portion with a second diameter, wherein a length of the optical waveguide section is determined by a number of turns wrapped around each of the first and second portions;
- and
- signal processing equipment for detecting variations in phase between light pulses reflected from the two Bragg gratings caused by changes in length of the optical waveguide section due to acoustic energy impinging on the mandrel.
1 more element
A method of controlling a length of an optical waveguide section during manufacture of an interferometric sensor, comprising:
- providing a mandrel having at least a first section with a first outer diameter and a second section with a second outer diameter;
- wrapping the optical waveguide section a first number of times around the first section and a second number of times around the second section;
- and
- controlling the wrapped length of the optical waveguide section by varying the first number and the second number.
1 more element
Dependencies are inferred from the claim text.