Optical fiber for sensors including holes in cladding
First Claim
1. An optical fiber, in particular for use as a sensor, comprisinga cylindrical core which extends in the longitudinal direction of the fiber and is located centrally in the fiber,a cladding which surrounds the core, is connected to the core and has a substantially cylindrical exterior surface, anda hole located completely in the cladding and extending in the longitudinal direction of the fiber,and a substance which changes its volume for variations of physical parameters characteristic of a region where the fiber is intended to be used,the longitudinal hole being completely or partly filled with the substance.
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Accused Products
Abstract
An optical fiber intended to be used as a sensor is of the kind suitable for communication and has a longitudinal cavity or hole which can be intentionally closed or has a more narrow shape at definite positions in the longitudinal direction of the fiber. The cavity, the diameter of which can be of the magnitude of order of 5 μm-50 μm, is filled with a material changing its volume depending on physical quantities in the fiber environment. The hole can be closed or made narrower at different positions in the longitudinal direction of the fiber for instance by locally heating the fiber by a pulsed laser beam.
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Citations
21 Claims
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1. An optical fiber, in particular for use as a sensor, comprising
a cylindrical core which extends in the longitudinal direction of the fiber and is located centrally in the fiber, a cladding which surrounds the core, is connected to the core and has a substantially cylindrical exterior surface, and a hole located completely in the cladding and extending in the longitudinal direction of the fiber, and a substance which changes its volume for variations of physical parameters characteristic of a region where the fiber is intended to be used, the longitudinal hole being completely or partly filled with the substance.
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5. An optical fiber, in particular for use as a sensor, comprising
a cylindrical core which extends in the longitudinal direction of the fiber and is located centrally in the fiber, a cladding which surrounds the core, is connected to the core and has a substantially cylindrical exterior surface, and a hole located completely in the cladding and extending in the longitudinal direction of the fiber, wherein the hole has several first longitudinal segments and second longitudinal segments located between the first longitudinal segments and having smaller diameters or having smaller dimensions as measured linearly in a cross section of the hole than the first longitudinal segments, so that the diameter of or the dimension, in a cross section, of the longitudinal hole varies in the longitudinal direction of the fiber.
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14. A method for preparation of an optical fiber, in particular for use as a sensor, comprising the steps of:
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drawing an optical fiber in a drawing direction from a suitably heated preform assembly, where the preform assembly contains a core region, which in the drawing forms the core of the fiber and has a longitudinal direction, this longitudinal direction being parallel to the drawing direction, and further contains a cladding region surrounding the core region, making before the drawing, a cavity in the preform assembly outside the core region and substantially in parallel to the longitudinal direction of the core region, so that after the drawing operation an optical fiber is obtained having an elongated core formed from the core region and having a longitudinal direction, a cladding formed from the cladding region and located around the core, and a cavity located completely in the cladding extending along and essentially in parallel to the core, wherein during and/or after the drawing of the preform assembly to form the fiber, the fiber is influenced over several regions which are limited in the longitudinal direction of the fiber for forming segments having a smaller diameter or a smaller cross-sectional dimension of the cavity than that of non-influenced segments of the fiber. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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Specification