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
  • G02B6/4401—Optical cables
  • G02B6/4415—Cables for special applications
  • G02B6/4427—Pressure resistant cables, e.g. undersea cables
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
  • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
  • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
  • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
  • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
  • G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
  • G01D5/35354—Sensor working in reflection
  • G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
  • G01D5/35361—Sensor working in reflection using backscattering to detect the measured quantity using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering
• • 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
  • G02B6/4401—Optical cables
  • G02B6/4429—Means specially adapted for strengthening or protecting the cables
  • G02B6/443—Protective covering
  • G02B6/4432—Protective covering with fibre reinforcements
• • 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
  • G02B6/4401—Optical cables
  • G02B6/4415—Cables for special applications
  • G02B6/4416—Heterogeneous cables
• • 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
  • G02B6/4401—Optical cables
  • G02B6/4429—Means specially adapted for strengthening or protecting the cables
  • G02B6/443—Protective covering

Definitions

• the present invention relates to a telecommunications cable, in particular an underwater telecommunications cable. It also relates to a method for measuring mechanical deformations undergone by such a telecommunications cable.
• the field of the invention is, without limitation, that of telecommunications.
• Fiber optics can be used to implement sensors for various physical quantities.
• the light backscattered at scattering sites can be used to detect deformations, movements or vibrations of the fiber.
• Such fiber optic sensors find particular application in monitoring the degree of wear of electric current cables.
• Such cables can for example connect offshore floating installations, such as offshore wind turbines, to terrestrial installations. These submarine cables are subject in particular to the more or less permanent movement transmitted by the waves.
• one or more sensor optical fibers can be inserted into the cable to follow and detect its movements and stresses.
• fiber optic sensor is seismic monitoring.
• terrestrial or submarine telecommunication cables are used to detect slow movements of the ground or the seabed.
• one or more optical fibers dedicated to the transmission of telecommunication data are also intended to transmit measurement pulses.
• Techniques used to carry out such monitoring operations are of the reflectometry and laser interferometry type and include, for example, DAS (for distributed acoustic sensing ) and FMI (for Frequency Metrology Interferometry ). frequency).
• DAS distributed acoustic sensing
• FMI Frequency Metrology Interferometry
• any use of telecom fibers for DAS or FMI reduces cable bandwidth. This can lead to a risk of compromising the security or confidentiality of the telecom data transmitted.
• telecom operators do not allow access to their cables for scientific purposes or basic research.
• the object of the invention is to provide a telecommunications cable, in particular submarine, which can overcome these drawbacks.
• An object of the present invention is to provide a telecommunications cable that can be used in the context of scientific research without compromising the security of the telecom data transmitted.
• Another object of the present invention is to propose a telecommunications cable making it possible to monitor the mechanical integrity as well as the state of health thereof.
• a telecommunications cable, in particular submarine comprising:
• the cable further comprising at least one sensor optical fiber arranged between the core and the protective sheath.
• the telecommunications cable according to the present invention is a hybrid cable comprising both optical fibers in the core, dedicated to telecommunications, as well as at least one sensor optical fiber arranged between the core and the protective sheath.
• This at least one sensor optical fiber is an additional optical fiber which is not intended for the transmission of telecommunication data, but only for a sensor function.
• the arrangement of the sensor fiber both outside the core and inside the protective sheath provides good protection of the sensor fiber against the forces imposed on the telecommunication cable (bending, manipulation of the cable, possible shocks, etc. .), while maintaining good sensitivity of the sensor fiber to capture the stresses and stresses of the cable.
• Such a cable makes it possible in particular to carry out monitoring or measurements in places which are not otherwise accessible, in particular for seismic monitoring or for observing the movement of the seabed. It is also possible to control and monitor the state of health of the telecommunication cable, i.e. to monitor any progressive degradation over time, and to detect any voluntary or involuntary external degradation. All these degradations can indeed compromise the integrity of the cable and/or the confidentiality of the data transported.
• the telecommunications cable according to the invention makes it possible to completely decouple the transmission of telecom data from the environmental measurements of the cable.
• the at least one sensor optical fiber can be arranged in a metal tube, the metal tube forming part of the inner frame.
• the sensor optical fiber is particularly well protected from any mechanical damage.
• the construction of the cable is only slightly changed compared to a standard cable.
• At least two sensor optical fibers are arranged in a metal tube, the metal tube forming part of the inner frame.
• the presence of at least two sensor fibers provides redundancy in the event of any failure of one of the sensor fibers.
• the sensor optical fibers can be arranged tightly against each other, according to a so-called tight configuration.
• the tight configuration is particularly well suited for implementing the BOTDR technique (for Brillouin Optical Time Domain Reflectometry ).
• the BOTDR technique is particularly suitable for the detection of seabed deformation due to the activity of submarine faults, as well as for establishing and monitoring the state of health of the telecommunications cable itself.
• the BOTDR technique makes it possible in particular to observe sudden or gradual/slow changes (for example of the order of a few centimeters per day, per month or per year). In general, the BOTDR makes it possible to measure changes on base frequencies lower than 1 Hz.
• the tight configuration is called tightly bound in English.
• the sensor optical fibers can be arranged freely with respect to each other, according to a so-called free configuration.
• the free configuration is particularly well suited to implement the technique of DAS (distributed acoustic detection) or IMF (frequency metrology interferometry).
• DAS and FMI techniques are particularly suitable for seismic monitoring.
• it is possible to detect earthquakes occurring at great distances, for example several hundred kilometers, from the coast, or in places without seismological stations. Seismic monitoring and the performance of seismic warning systems can therefore be improved.
• the DAS technique also allows monitoring of the telecommunications cable itself, by detecting involuntary damage and/or voluntary intrusions.
• DAS and IMF make it possible in particular to observe rapid changes, for example stresses shorter than one second, i.e. with a frequency of >1 Hz).
• At least two sensor optical fibers can be arranged tightly against each other, according to the so-called tight configuration, in a first metal tube, and at least two sensor optical fibers can be arranged freely with respect to each other, according to the so-called free configuration, in a second metal tube.
• the first and second metal tubes are part of the inner frame, the empty space in the tube in the tight configuration being filled with a material such as a resin or a gel.
• This configuration of the telecommunications cable makes it possible to perform measurements of deformations and/or slow and rapid changes in the cable with a single cable, using the appropriate measurement technique(s).
• the intermediate sheath may comprise a metal sheath suitable for transmitting electrical signals.
• Electrical signals are required in particular to power repeaters installed at regular intervals along the telecommunications cable.
• the metal sheath may be copper.
• the telecommunications cable may also comprise an additional reinforcement arranged radially around the protective sheath, and an additional protective sheath arranged radially around the additional reinforcement.
• Such a cable with a double armor is particularly robust and well suited to protect the optical fibers in the core when the cable is deployed in areas at risk, for example due to strong anthropogenic activity (fishing, trawling, etc.).
• the steel wires of the frame and/or the tubes containing the sensor optical fibers can be made of stainless steel.
• This material is not or very little subject to corrosion.
• the mechanical deformations undergone by a telecommunications cable, in particular submarine can include in particular elongations and axial compressions.
• the deformations can come from natural origins (earthquake, submarine slide or other movement of the seabed, etc.), from involuntary anthropogenic stresses (trawling, ship's anchor, etc.) or even from voluntary intrusions (espionage ). Cable deformations can be slow or fast.
• the term "mechanical deformation” can also mean damage or any other mechanical modification of the cable.
• the at least one sensor fiber present in the telecommunications cable makes it possible to establish a follow-up of the state of health of said cable and to monitor the environment of the cable.
• The is a schematic representation of an example of an underwater telecommunications cable, seen in cross section, according to one embodiment of the invention.
• the cable 1 comprises a core 2 with a plurality of optical fibers 3. These optical fibers 3 are dedicated to the transmission of data for telecommunications.
• the core 2 is surrounded by a sheath of gel 4 for the mechanical protection of the optical fibers 3 and the watertightness.
• the gel layer 4 is surrounded by a copper sheath 5. This metallic sheath 5 makes it possible to transmit electric current.
• the gel sheath 4 and the metal sheath 5 constitute an intermediate sheath 6.
• a reinforcement 7 is arranged radially around the intermediate sheath 6.
• the reinforcement 7 protects the optical fibers from mechanical stresses and gives the cable its mechanical stability.
• the armature 7 consists of a ring arrangement of a plurality of steel wires 8.
• the wires are made of stainless steel.
• a protective sheath 9 made of polymer material is arranged radially around the reinforcement 7, constituting the outer, waterproof barrier of the cable 1.
• the cable 1 also includes fiber optic sensor.
• Three sensor fibers 10 are arranged tightly against each other in a metal tube 11 forming part of the frame 7.
• Three other sensor fibers 12 are arranged loosely relative to each other in a another metal tube 13 also forming part of the frame 7.
• the empty space in the metal tube 11 is filled with a resin or gel 14.
• the metal tubes 11, 13 are preferably made of stainless steel, like the other wires of the frame 7.
• The is a schematic representation of another example of an underwater telecommunications cable, seen in cross-section, according to another embodiment of the invention.
• the cable 100 according to the embodiment shown in the includes all the elements of the cable 1 according to the embodiment of the .
• the 100 cable of the further comprises a second reinforcement 15 arranged radially around the metal sheath 5.
• This additional reinforcement 15 is, like the inner reinforcement 7, made up of a plurality of steel wires arranged in a ring.
• An additional protective sheath 16 made of polymer is arranged radially around the additional reinforcement 15.
• the protective sheath or sheaths may in particular be made of polyethylene.
• the diameter of the cables according to the embodiments of Figures 1 and 2 is approximately between 10 and 20 mm.
• the measurement method makes it possible to measure the mechanical deformations undergone by a telecommunication cable according to the invention, for example by the cables according to the embodiments described with reference to Figures 1 and 2.
• the interrogator comprises a laser source as well as a light sensor.
• a laser pulse 21 is coupled into each sensor optical fiber of the cable at its proximal end. Pulse 21 propagates in the sensor fiber and is partially backscattered by scatter sites in the fiber. The backscattered light 22 interferes with the light reflected from the distal end of the sensor fiber.
• the backscattered light 22 is detected by the sensor of the interrogator 20.
• the signal captured includes the signature of a scattering site whose evolution can then be observed. It is thus possible to detect or determine a mechanical deformation undergone by the cable from the optical signal.
• the interrogator 20 is equipped with a processor or equivalent.
• the ends of two sensor fibers can be soldered together at the distal end of the cable.
• a laser pulse can be injected into one of the sensor fibers, and both fibers can be interrogated simultaneously.
• This embodiment is particularly suitable for short distances traveled ( ⁇ 50 km). It allows duplication of the measurement, this redundancy increasing the reliability of the measurements.
• the interrogator 20 can be of the DAS type.
• the interrogator is coupled to one or more sensor fibers in a tight configuration.
• the interrogator 20 can also be of the BOTDR type.
• the interrogator 20 can also be of the FMI type.
• a DAS interrogator can be coupled to one or more sensor fibers in free configuration for seismic monitoring and/or cable monitoring to detect voluntary or involuntary damage.
• a BOTDR interrogator can be coupled to one or more sensor fibers in a tight configuration to detect slow deformations of the seabed due to the activity of underwater faults and/or to detect voluntary or involuntary degradations.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Insulated Conductors (AREA)
• Optical Transform (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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• 2020
  • 2020-12-22 FR FR2013882A patent/FR3118205A1/fr active Pending
• 2021
  • 2021-12-20 WO PCT/EP2021/086699 patent/WO2022136217A1/fr active Application Filing
  • 2021-12-20 CN CN202180087408.5A patent/CN116710824A/zh active Pending
  • 2021-12-20 US US18/258,818 patent/US20240045163A1/en active Pending
  • 2021-12-20 JP JP2023563151A patent/JP2024501375A/ja active Pending
  • 2021-12-20 EP EP21840915.9A patent/EP4268001A1/fr active Pending

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