Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
  • G02B6/4439—Auxiliary devices
  • G02B6/4471—Terminating devices ; Cable clamps
  • G02B6/4477—Terminating devices ; Cable clamps with means for strain-relieving to interior strengths element
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
  • G02B6/4439—Auxiliary devices
  • G02B6/444—Systems or boxes with surplus lengths
  • G02B6/4441—Boxes

Definitions

• the invention relates to a device for monitoring a structure using optical cables, as well as to a method for connecting associated optical cables.
• optical cables There are known devices for measuring temperature or deformation using optical cables. Generally, these devices make it possible to perform "distributed” type measurements, based on backscattering techniques (in particular Brillouin or Raman), or of “distributed” type, when for example the optical cable comprises one or more fibers. provided with photo-inscribed Bragg gratings distributed along the fiber at regular intervals.
• the cable is placed along a structure to be monitored, for example a building, and makes it possible to obtain a measurement of the deformations or temperature variations of the structure, especially in case of ground settlement.
• An object of the invention is to provide a device for monitoring a structure using optical measurement cables to ensure mechanical continuity in the cable connection areas.
• a device for monitoring a structure comprising:
• a first cable comprising a first measurement optical fiber and a first carrier element
• a second cable comprising a second measurement optical fiber and a second carrier element
• connection box comprising a compartment inside which the first carrier element and the second carrier element extend, and an adhesive composition filling the compartment, the first carrier element and the second carrier element being embedded in the adhesive composition of to secure the carrier elements together.
• connection of the load-bearing elements ensures a mechanical continuity in the cable connection areas.
• the device makes it possible to connect the optical cables to the same Telec points as the connections of the sections.
• the housing comprises a base having walls surrounding the compartment, the walls comprising a first opening for the passage of the first carrier element and a second opening for the passage of the second carrier element,
• the first carrier element and the second carrier element extend parallel to each other inside the compartment, the first optical fiber has an end connected to one end of the second optical fiber by splicing, the device comprising a splice protection, and the housing comprises a second compartment in which the splice protection is received,
• the housing comprises a base having walls surrounding the second compartment, the walls comprising a first opening for the passage of the first optical fiber and a second opening for the passage of the second optical fiber,
• the housing comprises a tab for holding the splice protection in the second compartment
• the housing comprises a base having a curved wall for winding the first and / or second optical fiber around the wall,
• the wall has a radius of curvature greater than or equal to 10 millimeters, preferably greater than or equal to 15 millimeters,
• the device comprises a tab for holding the first optical fiber and / or the second optical fiber around the curved wall,
• the adhesive composition forms a single single block in which the first carrier element and the second carrier element are embedded
• the adhesive composition comprises an epoxy polymer
• the adhesive composition has an elongation at break of between 10 and 40%, preferably between 15 and 30%,
• the adhesive composition is able to withstand a tensile force exerted on the carrier elements resulting in an elongation of the supporting elements greater than or equal to 2%,
• the first cable comprises a first sheath surrounding the first optical fiber and the first carrier element, the first sheath being interrupted so as to form a sheath end, and the housing has a first recess in which the sheath end is housed,
• the second cable comprises a second cladding surrounding the second optical fiber and the second carrying element, the second cladding being interrupted so as to form a sheath end, and the casing has a second recess in which the end of the cladding is housed; sheath, the first and second recesses being arranged on either side of the compartment inside which extend the first carrier member and the second carrier member,
• the device comprises an analysis apparatus capable of measuring at each point of a plurality of points along the optical fibers a parameter representative of a parameter representative of a state of the optical fiber.
• the invention also relates to a method for connecting a first cable and a second cable, the first cable comprising a first optical measurement fiber and a first carrier element, and the second cable comprising a second optical measurement fiber and a second optical fiber.
• second carrier element the method comprising a step of:
• the method may further comprise a step of:
• the invention also relates to a structure comprising a series of elementary sections, each elementary section being connected to a following elementary section of the series, and being equipped with:
• the optical cable in contact with the elementary section, the optical cable comprising an optical measurement fiber and a carrier element
• connection box comprising a compartment inside which the optical cable carrying member extends and a carrier element of the optical cable fitted to the adjacent elementary section, and an adhesive composition filling the compartment, the carriers being submerged; in the adhesive composition so as to secure the carrier elements together.
• FIG. 1 schematically represents, in cross-section, an exemplary structure to be monitored
• FIG. 2 schematically represents, in cross-section, an optical cable for measuring deformation and temperature, suitable for use in a monitoring device according to one embodiment of the invention
• FIG. 3 schematically represents, in perspective, a device for monitoring a structure, according to one embodiment of the invention, before application of the adhesive composition
• FIG. 4 schematically represents, in perspective, the device for monitoring a structure, after application of the adhesive composition
• the structure to be monitored 1 shown in FIG. 1 is a "pipe in pipe” pipe used for the submarine transport of crude oil.
• the pipe 1 is formed of a series of elementary sections 2, each elementary section 2 typically having a length of the order of 600 meters and an outer diameter of the order of 30 centimeters.
• Each elementary section 2 comprises an outer tube 3, an inner tube 4 concentrically disposed inside the outer tube 3, and an insulating layer 5 disposed between the outer tube 3 and the inner tube 4.
• the insulating layer 5 is in contact with the inner tube 4 and surrounds the inner tube 4.
• Each elementary section 2 is equipped with an optical cable 7 of measurement of a physical parameter of the section.
• the physical parameters measured are a deformation parameter and a temperature parameter.
• the optical cable 7 extends in a longitudinal direction of the elementary section 2, between the inner tube 4 and the insulating layer 5.
• the optical cable 7 can be wound helically around the inner tube 4.
• the optical cable 7 is shown in more detail in FIG.
• the optical cable 7 comprises a first optical element 8, a second optical element 9, two carrier elements 10 and 1 1, and a sheath 1 6 surrounding the optical elements 8, 9 and the carrier elements 10, 1 1.
• the first optical element 8 is a temperature measuring element.
• the first optical element 8 comprises a first optical fiber 12 and a first envelope 13 surrounding the first optical fiber 12.
• the first optical fiber 12 is disposed in the first envelope 13 leaving a gap between the optical fiber 12 and the envelope 13. so that the optical fiber 12 is free in the envelope 13.
• the first optical fiber 12 is disposed in the first envelope 13 with an excess of length relative to the first envelope 12. This makes it possible, in particular, to make the first optical fiber 12 insensitive to the stresses of elongation which are exerted on the optical cable 7.
• the excess length of the first optical fiber 12 relative to the first envelope 13 is between 0 and 0.5%.
• the first envelope 13 is formed of a thermoplastic material, such as a polyester for example.
• the first casing 13 has a cylindrical shape of revolution and has an internal diameter of between 0.6 and 2 millimeters, for example of the order of 1 millimeter, and an external diameter of between 1.3 and 3.5 millimeters, for example. example of the order of 1, 6 millimeters.
• the second optical element 9 is an optical element for measuring deformation.
• the second optical element 9 comprises a second optical fiber 14, identical to the first optical fiber 12, and a second envelope 15 surrounding the second optical fiber 14.
• the second optical fiber 14 is disposed in the second envelope 15 without leaving any gap between the optical fiber 14 and the envelope 15 so that the optical fiber 14 and the envelope 15 are integral with each other all along the optical fiber 14. In this way, the elongation stresses experienced by the the second envelope 15 are transmitted to the second optical fiber 14.
• the second envelope 15 is formed of a material having a low coefficient of expansion, such as a liquid crystal polymer (LCP) or a polymer blend comprising a liquid crystal polymer (LCP) and a polyester, such as a polybutylterephthalate (PBT) for example.
• LCP liquid crystal polymer
• PBT polybutylterephthalate
• the second casing 15 has a cylindrical shape of revolution and has an outer diameter of between 0.5 and 2 millimeters, for example of the order of 0.9 millimeters.
• the carrier members 10 and 11 are formed of a tensile-resistant material, such as a plastics material reinforced with reinforcing fibers.
• the reinforcing fibers are fibers of dielectric material, such as glass fibers, or poly-para-phenylene terephthalamide fibers (known under the trademark Kevlar).
• Each carrier element 10 and 11 is of elongate shape, cylindrical in revolution, and has a diameter of between 0.5 and 5 millimeters, for example of the order of 1.5 millimeters.
• the carrier elements 10 and 11 provide the optical cable 7 with tensile properties and limit the thermal expansion of the optical cable 7.
• the first optical element 8, the second optical element 9 and the carrier elements 10 and 11 are embedded in the sheath 16.
• the sheath 16 is of elongate shape.
• the sheath 1 6 has a cross section of flattened shape, having for example a width 11 of the order of 8 millimeters and a thickness e1 of the order of 3 millimeters.
• the sheath 1 6 is formed of a temperature-resistant material resistant to hydrocarbon exposure, such as a fluorinated thermoplastic material, for example polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA) or ethylene Tetrafluoroethylene (ETFE).
• PVDF polyvinylidene fluoride
• PFA perfluoroalkoxy
• ETFE ethylene Tetrafluoroethylene
• the sheath 1 6 was formed by extruding the thermoplastic material around the optical elements 8 and 9 and the reinforcing elements 10 and 1 1, in order to bind the elements 8, 9, 10 and 1 1 to the sheath 1 6. Of this way, the elongation stresses experienced by the cable 7 are transmitted to the envelopes 13 and 15 of the optical elements.
• the first optical element 8, the second optical element 9 and the carrier elements 10 and 1 1 extend parallel to each other.
• the first optical element 8, the second optical element 9 and the carrier elements 10 and 11 have longitudinal axes extending in the same plane, which is preferably the median plane P of the sheath 16 extending perpendicular to the thickness e of the sheath.
• the carrier elements 10 and 11 are arranged on either side of the optical elements 8 and 9.
• the small thickness e of the cable 7 makes it easy to integrate it between the inner tube 4 and the insulating layer 5 of the structure 1 to be monitored.
• the monitoring device 17 of the structure 1 comprises a first optical cable 7A and a second optical cable 7B, each optical cable 7A, 7B being integral with an elementary section 2 of the structure to be monitored 1, and a junction box 18 for connecting the optical cables 7A and 7B to each other.
• Each of the optical cables 7A, 7B is identical to the cable 7 illustrated in FIG.
• the first optical cable 7A comprises a temperature measuring element 8A, a deformation measuring element 9A, two carrying elements 10A and 11A and a sheath 1 6A.
• the first optical cable 7A has been stripped at one end. Specifically, the sheath 1 6A has been removed over a predetermined length of the first cable 7A, so as to reveal the elements 8A, 9A, 10A and 1 1 A. Thus, the first sheath 16A is interrupted to form a first sheath end 19A.
• the second optical cable 7B comprises a temperature measuring element 8B, a deformation measuring element 9B, two carrier elements 10B and 11B and a sheath 16B.
• the second optical cable 7B has been stripped at one end. Specifically, the sheath 1 6B has been removed over a predetermined length of the second cable 7B, so as to reveal the elements 8B, 9B, 10B and 1 1 B.
• the second sheath 1 6B is interrupted so as to form a second sheath end 19B.
• connection box 18 comprises a base 20 for receiving the optical cables 7A and 7B and a cover 21 adapted to be fixed on the base 20 to close the housing 18.
• the base 20 has a generally elongate shape, of small thickness.
• the base 20 has a length L2 at least 5 times greater than its width 12, for example a length of about 250 millimeters, a width of the order of 35 millimeters, and a low thickness e2, of the order of 5 millimeters.
• the base 20 is formed of a temperature resistant material, such as a thermoplastic polymer loaded with glass fibers for example.
• the base 20 comprises a first recess 22, in which is housed the first sheath end 19A and a second recess 23, in which is housed the second sheath end 19B.
• the first recess 22 and the second recess 23 are not arranged facing each other, but are slightly offset relative to a longitudinal central axis X of the base 20, so that the first cable 7A and the second cable 7B extending parallel to each other without being aligned with each other.
• the optical elements 8A, 9A, 8B, 9B and the reinforcing elements 10A, 11A, 10B, 11B without sheath extend inside the base 20.
• the base 20 comprises a first wall 24 delimiting a first compartment 25 (or central compartment) intended to receive the first carrier elements 10A, 11A and the second carrier elements 10B, 11B.
• the first wall 24 comprises four openings 26 to 29 including two first openings 26, 27 for the passage of the first carrier members 10A, 11A and two second openings 28, 29 for the passage of the second carrier members 10B, 1 B.
• the first openings 26, 27 are slightly offset from the second openings 28, 29, so that each first carrier member 10A, 11A extends inside the first compartment 25 parallel to a second carrier member. 10B, 1 1 B, being in contact therewith.
• the base 20 further comprises second walls 30 defining a second compartment 31 and third walls 32 defining a third compartment 33.
• the second compartment 31 and the third compartment 33 (or side compartments) are arranged on either side of the first compartment 25, symmetrically with respect to the longitudinal axis X of the base 20.
• the second compartment 31 is intended to receive splice protection connection between the first optical fiber 12A of the first cable 7A and the first optical fiber 12B of the second cable 7B.
• the base 20 comprises tabs 34 for holding the splice protection in the second compartment 31.
• the second walls 30 comprise a first opening 48 for the passage of the optical fiber 12A and a second opening 49 for the passage of the optical fiber 12B.
• the third compartment 33 is intended to receive splice splice protection between the second optical fiber 14A of the first cable 7A and the second optical fiber 14A of the second cable 7B.
• the base 20 also comprises tabs 35 for holding the splice protection in the third compartment 33.
• the third walls 32 comprise a first opening 50 for the passage of the optical fiber 12B and a second opening 51 for the passage of the optical fiber 14B.
• the base 20 further comprises a fourth wall 36 and a fifth wall 37 forming guide walls for winding the optical fibers 12 and 14 inside the base 20.
• the fourth wall 36 and the fifth wall 37 are arranged on either side of the first compartment 25, symmetrically with respect to a transverse axis Y of the base 20, perpendicular to the longitudinal axis X.
• the fourth wall 36 and the fifth wall 37 each have curved winding portions 38, 39 on which the optical fibers can be wound. .
• the winding portions 38 and 39 have a radius of curvature greater than or equal to 10 millimeters (preferably greater than or equal to 15 millimeters), in order to limit the curvature of the optical fibers in the casing and prevent their damage.
• the base 20 also includes holding tabs 40 of the optical fibers around the curved walls 36 and 37.
• the base 20 comprises a sixth wall 41 and a seventh wall 42 (or fixing wall) for fixing the cover 21 to the base 20.
• the sixth wall 41 and the seventh wall 42 each have a circular shape.
• the sixth wall 41 and the seventh wall 42 are arranged on either side of the first compartment 25, symmetrically with respect to the transverse axis of the base.
• the sixth wall 41 and the seventh wall 42 are respectively surrounded by the fourth wall 36 and the fifth wall 37.
• the fourth wall 36, the fifth wall 37, the sixth wall 41 and the seventh wall 42 each have openings 43 allowing the carrying elements 10A, 11A, 10B, 11B to pass through the walls 36,
• the cover 21 comprises a plate 44 of generally flat shape, an eighth wall 45 and a ninth wall 46 projecting from the plate 44.
• the eighth wall 45 and the ninth wall 46 each have a circular shape.
• the plate 44 is able to cover the base 20 so as to close the housing 18.
• the eighth wall 45 of the cover 21 is adapted to engage the sixth wall 41 of the base 20, and the ninth wall 46 of the cover 21 is adapted to engage the seventh wall 42 of the base 20, so as to fix the cover 21 on the base 20.
• the eighth wall 45 and the ninth wall 46 are adapted to be inserted into the sixth wall 41 and the seventh wall 42 respectively.
• the presence of the openings 43 in the sixth wall 41 and the seventh wall 42 promotes an elastic deformation of these walls for the insertion of the eighth wall 45 and the ninth wall 46.
• the first compartment 25 is filled with an adhesive composition 47.
• the adhesive composition forms a single single block of material filling the first compartment 25.
• the first carrier elements 10A, 10B and the second carrier elements 11A , 1 1 B are embedded in the adhesive composition 47. In this way, the carrier elements 10A, 10B, respectively 1 1 A, 1 1 B, are joined together.
• the adhesive composition 47 used is, for example, an ultraviolet-curable epoxy composition, such as a composition sold under the reference UV EPOXY 020507 by the company Resin Design, LLC.
• the adhesive composition 47 preferably has an elongation at break of between 15 and 30%.
• the adhesive composition 47 is able to withstand a tensile force exerted on the carrier elements generating an elongation of the supporting elements greater than or equal to 2%.
• the mounting of the device 17 is performed according to the following steps.
• a first step the sheath 1 6A of the first cable 7A is removed over a predetermined length of the first cable, so as to reveal the optical elements 8A and 9A and the carrier elements 10A and 11A.
• the same operation is performed on the second cable 7B so as to reveal the optical elements 8B and 9B and the carrier elements 10B and 11B.
• the predetermined length is for example of the order of 1, 5 meters.
• the first envelope 13A, 13B, surrounding the first optical fiber 12A, 12B, of temperature measurement is removed over the predetermined length, so as to reveal the first optical fiber 12A, 12B temperature measurement.
• the second envelope 15A, 15B surrounding the second optical fiber 14A, 14B of stress measurement is removed over the predetermined length, so as to reveal the second optical fiber 14A, 14B of stress measurement.
• the carrier elements 10A, 10B, 11A and 11B are cut so as to be shortened.
• the carrier elements 10A, 10B, 11A and 11B then have a stripped portion having a length of 15 centimeters for example.
• the first sheath end 19A is positioned in the first housing 22 and the second sheath end 19B is positioned in the second housing 23.
• the carrier elements 10A, 10B, 11A and 11 B extend in part inside the first compartment 25.
• the first compartment 25 is filled with the adhesive composition 47 in liquid form, so as to embed the carrier elements 10A, 10B, 11A and 11B in the adhesive composition 47.
• the adhesive composition 47 is solidified by subjecting the adhesive composition 47 to ultraviolet radiation.
• the first optical fiber 12A of the first cable 7A is connected to the first optical fiber 12B of the second cable 7B by splicing.
• the splice can be made by fusion.
• the junction zone between the optical fibers 12A and 12B is protected by a splice protection device in the form of a protective sleeve surrounding the fused ends of the optical fibers, such as a sleeve of heat-shrinkable material. for example.
• the splice can be made mechanically.
• the optical fibers 12A and 12B are connected to each other by a mechanical connection device also fulfilling a role of splice protection device.
• the second optical fiber 14A of the first cable 7A is connected to the second optical fiber 14B of the second cable 7B by splicing.
• the optical fibers 12A, 12B, 14A and 14B are arranged in the base 20, being wound around the fourth wall 36 and the fifth wall 37 (that is to say around the guide walls ), and the splice protection devices are inserted into the second and third compartments 31 and 33.
• FIGS. 5 to 7 schematically represent different possible configurations for routing the optical fibers inside the base 20.
• first optical fiber 12A of the first cable 7A has been shown.
• other fibers 12B, 14A and 14B are routed identically.
• the optical fiber 12A is wound only around the fourth wall 36, making for example 6, 25 turns, then its end is directed towards the second compartment 31 where it is spliced with the optical fiber 12B.
• the optical fiber 12A is wound around the fourth wall 36, along the second compartment 31, then is wound around the fifth wall 37, then its end is directed towards the third compartment 33 where it is spliced with optical fiber 12B.
• 12A optical fiber is wound up, for example, 4, 25 turns around the fourth wall 36 and 0.5 turns around the fifth wall 37.
• the optical fiber 12A is wound around the fourth wall 36 forming small loops, then around the fourth wall 36 and the fifth wall 37, along the second compartment 31 and the third compartment 33, forming large loops, and its end is directed to the third compartment 33 where it is spliced with the optical fiber 12B.
• the optical fiber 12A is wound by making, for example, 2.25 turns around the fourth wall 36 and 1.75 turns around the fourth wall 36 and the fifth wall 37.
• the cover 21 is fixed on the base 20.
• the eighth wall 45 and the ninth wall 46 of the cover 21 are introduced into the sixth wall 41 and the seventh wall 42 of the base 20.
• the device 17 thus allows the connection of the first cable 7A and the second cable 7B, while simultaneously providing optical continuity from one cable to the other, a splice protection between the optical fibers 12A and 12B, 14A and 14B , and a continuity of the mechanical characteristics (in particular a continuity of the resistance of the cable in traction).
• a large number of optical cables can thus be connected in series.
• the end optical cables of the series are connected to an analysis apparatus.
• the analysis apparatus is capable of measuring at each point of a plurality of points along each optical element a value of the Brillouin frequency.
• the sensitivity of the first optical element to temperature variations - the ratio between the temperature of the optical element and the variation of the resulting Brillouin frequency - being known, it is possible to deduce, at each point along the first optical element a temperature variation value.
• the sensitivity to the elongation of the second optical element - the ratio between the imposed elongation (in percentage) and the variation of the resulting Brillouin frequency - being known, it is possible to deduce, at each point along the optical element, an elongation value of the second optical element.
• the variation of the Brillouin frequency also depends on the temperature of the optical element.
• the measurement of the elongation can be distorted in the event of temperature variation of the optical element.
• each cable is closely related to the structure whose temperature and deformation are to be measured, the elongation and temperature values measured along the optical cables are considered as deformation and temperature values of the structure to be monitored.
• each cable would comprise an optical fiber for measuring pressure or an optical acoustic measurement fiber.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Light Guides In General And Applications Therefor (AREA)

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Citations (2)

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• 2014
  • 2014-03-11 FR FR1452019A patent/FR3018617A1/fr active Pending
• 2015
  • 2015-03-11 EP EP15709904.5A patent/EP3117256A1/de not_active Withdrawn
  • 2015-03-11 WO PCT/EP2015/055103 patent/WO2015136007A1/fr active Application Filing

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