Redundant optical fiber system and method for remotely monitoring the condition of a pipeline

Patent metadata

Field	Value
Publication number	US-9784642-B2
Application number	US-200913119231-A
Country	US
Kind code	B2
Filing date	Sep 23, 2009
Priority date	Sep 23, 2008
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

An optical fiber sensor system and method for monitoring a condition of a linear structure such as a pipeline is provided which is capable of providing continuous monitoring in the event of a break in the sensing optical fiber or fibers. The system includes at least one sensing fiber provided along the length of the linear structure, and first and second interrogation and laser pumping sub-systems disposed at opposite ends of the sensing fiber, each of which includes a reflectometer. The reflectometer of the first interrogation and laser pumping sub-system is connected to one end of the sensing fiber. The reflectometer of the second interrogation and laser pumping sub-system is coupled to either (i) an end of a second sensing fiber provided along the length of the linear structure which is opposite from the one end of the first sensing fiber, or (ii) the opposite end of the first sensing fiber. Before any break of the sensing fiber or fibers occurs, each reflectometer redundantly monitors the condition of the linear structure over its entire length. After any such break occurs, each reflectometer will continue to receive signals up to the point of the break from opposite ends of the structure.

First claim

What is claimed is:

1. An optical fiber sensor system for monitoring a condition of a linear structure, the system comprising:
a sensor cable comprising first and second sensing fibers provided along the length of the linear structure and decoupled from each other,
first and second interrogation and laser pumping sub-systems disposed at opposite ends of the sensor cable, each of which includes a reflectometer,
the first sensing fiber being coupled only to the reflectometer of the first interrogation and laser pumping sub-system at one end such that the reflectometer of the first interrogation and laser pumping sub-system is configured to send optical signals and receive reflections of the optical signals through the first sensing fiber, and
the second sensing fiber being coupled only to the reflectometer of the second interrogation and laser pumping sub-system at one end opposite from the one end of the first sensing fiber such that the reflectometer of the second interrogation and laser pumping sub-system is configured to send optical signals and receive reflections of the optical signals through the second sensing fiber.

2. The system of claim 1 , wherein the first and second sensing fibers include one or more fiber optic amplifier stages along their lengths that are coupled to pump laser fibers of the first and second interrogation and laser pumping sub-systems, respectively.

3. The system of claim 2 , wherein each coupling between each of the one or more fiber optic amplifier stages of the first sensing fiber and a pump laser fiber from both the first and second laser pumping sub-system is implemented through an optical demultiplexer.

4. The system of claim 3 , wherein the sensor cables are configured to run in parallel to the structure, and are deployed, on either side of the structure, and/or in a same trench as the structure.

5. The system of claim 1 , wherein the linear structure includes one of a pipeline structure, a railway structure, a border structure, and a power cable structure.

6. The system of claim 1 , wherein the reflectometers of the system are Brillouin optical time domain reflectometers.

7. An optical fiber sensor system for monitoring a condition of a linear structure, the system comprising:
a sensor cable comprising first and second sensing fibers provided along the length of the linear structure and decoupled from each other, the first and second sensing fibers each including one or more fiber optic amplifier stages along its length, and
first and second interrogation and laser pumping sub-systems disposed at opposite ends of the sensor cable, each of which includes a reflectometer and pump laser fibers,
the first sensing fiber and the one or more fiber optic amplifier stages being coupled only to the reflectometer and the pump laser fibers of the first interrogation and laser pumping sub-system at one end, respectively, such that the reflectometer of the first interrogation and laser pumping sub-system is configured to send optical signals and receive reflections of the optical signals through the first sensing fiber, and
the second sending fiber and the one or more fiber optic amplifier stages being coupled only to the reflectometer and the pump laser fibers of the second interrogation and laser pumping sub-system at one end opposite from the one end of the first sensing fiber such that the reflectometer of the second interrogation and laser pumping sub-system is configured to send optical signals and receive reflections of the optical signals through the second sending fiber and the reflectometers of the first and second interrogation and laser pumping sub-systems redundantly monitor the length of the sensor cable.

8. A method for monitoring a length of a linear structure with an optical fiber sensor system comprising the steps of:
providing a sensor cable comprising first and second sensing fibers along the length of the linear structure with the first and second sensing fibers decoupled from each other,
transmitting optical signals and receiving reflections of the optical signals through one end of the first sensing fiber with a first interrogation and laser pumping sub-system coupled only to the one end of the first sensing fiber; and
transmitting optical signals and receiving reflections of the optical signals through one end of a second sensing fiber that is opposite from the one end of the first sensing fiber with a second interrogation and laser pumping sub-system coupled only to the one end of the second sensing fiber.

Assignees

• Strong Andrew
• Lees Gareth
• Hampson Roger
• Williams Kevin
• Hartog Arthur
• Onesubsea Ip Uk Ltd

Inventors

• Strong Andrew
• Lees Gareth
• Hampson Roger
• Williams Kevin
• Hartog Arthur

Classifications

• G01M11/39

  in which light is projected from both sides of the fiber or waveguide end-face · CPC title

• G01M11/083 Primary

  by using an optical fiber in contact with the device under test [DUT] · CPC title

• G01M11/3154

  Details of the opto-mechanical connection, e.g. connector or repeater · CPC title