Optical fiber sensor for measuring physical properties of fluids

• US 5,115,127 A
• Filed: 09/17/1990
• Issued: 05/19/1992
• Est. Priority Date: 01/03/1990
• Status: Expired due to Fees

• Current Assignee: The Government Of The United States As Represented By The Secretary Of The Navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Davis, Jon P., Samouris, Arthur, White, Barbara J., Bobb, Lloyd C.
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): ALLEN, STEPHONE B
• Application Number:
  US07/585,331
• Time in Patent Office: 610 Days
• Field of Search: 250/227.19, 250/231.1, 324/96, 350/96.29, 356/44, 356/72, 356/357-359
• US Class Current: 250/227.19
• CPC Class Codes: G01J 2009/0226 Fibres
• CPC Class Codes: G01J 2009/0288 Machzehnder
• CPC Class Codes: G01M 11/33 with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
• CPC Class Codes: G01M 11/331 by using interferometer
• CPC Class Codes: G01N 21/45 using interferometric methods; using Schlieren methods
• CPC Class Codes: G01N 25/18 by investigating thermal conductivity by calorimetry G01N25/20; by measuring change of resistance of an electrically-heated body G01N27/18

Abstract

A physical property of a fluid or of any optical fiber is measured using anptical fiber interferometer. A conductive material is disposed upon the surface of a region of a light tranmitting optical fiber and the region having the conductive material is disposed in the fluid. Light energy is applied to one end of the fiber and transmitted light is received at the other end of the fiber. Electrical energy is applied to the conductive material disposed upon the surface of the fiber to heat the region of the fiber and cause a change in the optical path length of the light transmitted through the fiber. The physical property of the fluid or optical fiber is determined in accordance with the change in the optical path length or phase of the received light caused by applying the electrical energy to the conductive material. Thermal conductivity is measured using a series of short energy pulses and determining the average phase change. The flow rate of a fluid is measured by measuring the phase change and applied electrical energy upon heating the fiber to an equilibrium temperature. The conductive material is gold and it encircles the fiber. The gold may be disposed on the jacket of the fiber or the jacket may be removed before disposing the gold.

Claims

1. A method for measuring the flow rate of a fluid using a light transmitting optical fiber, comprising the steps of:

(a) disposing a conductive material upon the surface of a region of the light transmitting optical fiber;

(b) disposing at least a portion of said fiber region having said conductive material in the fluid;

(c) applying light energy to a first end of the light transmitting optical fiber;

(d) applying electrical energy to said conductive material for a period of time long enough for the fiber to achieve temperature equilibrium;

(e) receiving transmitted light at a second end of said optical fiber;

(f) measuring the change in phase of said transmitted light during said period of time; and

(g) determining the flow rate in accordance with said change in phase and said applied electrical energy.

2. The method of claim 1, wherein the conductive material is gold.