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Publication Date: 2010-Sep-04
Document File: 9 page(s) / 229K

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The Prior Art Database


A method is described to package fiber optic sensors in an economical way with improved performance.

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    A method is described to package fiber optic sensors in an economical way with improved performance.


    Fiber optics, flexible packaging, harsh environment, double wall and welded seam


    One type of optical detection method uses fiber optics as the main transducer. It would be useful in some applications for the fiber optic-based sensors to be functional in harsh environments and more particularly at high temperatures. In harsh environments, it is necessary to protect the fiber optic sensors from direct contact with the environment.

    One protection embodiment includes a double thin wall tubing which is more flexible than a single thick wall of equivalent total thickness. Figure 1 illustrates a packaging used to protect the fiber optic sensor in a harsh environment. The packaging includes an optical fiber 11, a protective coating 12, a double wall tubing 13, and a welded seam 14. The use of a double thin wall works well for shorter lengths of optical fiber, but, for longer lengths, the insertion of the optical fiber into the tubing becomes a challenge when the inner diameter of the tubing is close to the outer diameter of the optical fiber. It is desirable to have tubing as small in diameter as possible to ensure fast thermal response, minimum space requirements, and good flexibility. In some embodiments, the double wall tubing is left open along its entire length while the fiber is inserted


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and is then laser welded to ensure a seal. The process works well but requires the optical fiber to be shipped to a laser welding manufacturer which is time consuming and expensive.

    When optical fibers are used in jet engines, gas or steam turbines, gasification towers, or distillation towers, for example, long optical fibers are used with some extending beyond to forty meters, for example. In these embodiments, the protected optical fiber must be sufficiently flexible for manufacturing, installation, and use. .

    Therefore there is a need in the art for a flexible packaging of optical fiber for use in harsh environments. The packaging is designed to be thick enough to guarantee the proper protection to the fiber while being flexible enough to for handling and /or application purposes.

    Figure 2 illustrates a proposed alternative packaging including an optical fiber 21, a protective metal coating 22, sections of an inner tubing layer 23, sections of an intermediate tubing layer 24, and an outer continuous layer 25. The fiber 21 is typically of one hundred to few hundred micrometers in diameter with a length ranging up to one hundred meters. The fiber is made durable with a thin metal film 22. On top of the thin film 22, the inner tubing layer sections 23 are inserted which have inside diameters as small as possible while being l...