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WO1992007236A1 - Reflecteur a fibres optiques - Google Patents

Reflecteur a fibres optiques Download PDF

Info

Publication number
WO1992007236A1
WO1992007236A1 PCT/GB1991/001820 GB9101820W WO9207236A1 WO 1992007236 A1 WO1992007236 A1 WO 1992007236A1 GB 9101820 W GB9101820 W GB 9101820W WO 9207236 A1 WO9207236 A1 WO 9207236A1
Authority
WO
WIPO (PCT)
Prior art keywords
fibre
optical fibre
light
reflector
optical
Prior art date
Application number
PCT/GB1991/001820
Other languages
English (en)
Inventor
Christopher Lamb
Original Assignee
Gec-Marconi Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gec-Marconi Limited filed Critical Gec-Marconi Limited
Publication of WO1992007236A1 publication Critical patent/WO1992007236A1/fr

Links

Classifications

    • 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
    • G01D5/35383—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 multiple sensor devices using multiplexing techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
    • G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
    • 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
    • G02B6/24—Coupling light guides
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/241—Light guide terminations
    • G02B6/243—Light guide terminations as light absorbers
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers

Definitions

  • This invention relates to optical fibre reflectors for use in sensing systems such as for example are used in the detection of acoustic pressure waves e.g. hydrophone applications or temperature sensing.
  • Reflectometric arrays of interferometric sensors are formed by constructing a line of fibre transducers separated by a semi reflecting element such as is described in British Patent Specification No. 2126820B.
  • an optical fibre reflector comprising a pair of fibres interconnected intermediate of their ends to permit optical coupling therebetween, one of the fibres having a light reflective termination at one end and a light dispersive termination at the opposite end.
  • the invention also includes an optical sensing system comprising an optical fibre arranged to be subjected along its length to fibre deforming forces during operation of the system and means for producing coherent light signals for transmission along said optical fibre, in which the optical fibre is provided along its length with a plurality of equally spaced optical fibre reflectors as previously defined so that a small proportion of each light signal being transmitted along the fibre will be reflected back along the fibre from each of the reflectors whereby each reflected light signal after the first interferes with either the previously reflected signal from the preceding reflector or a reference light signal of the same frequency or a frequency with a constant difference frequency to the transmitted light signal to produce an electrical signal in square law photo-detection means of the system, the difference between respective electrical signals corresponding to successive fibre elements being dependant upon the length of the fibre elements so that changes in length of these elements produced by the incidence of deforming forces will result in changes in the electrical signals which will be detected.
  • FIG 1 shows an optical fibre reflector constructed in accordance with the invention employing two equal diameter fibres
  • Figure 3 shows a schematic diagram of a sensing system constructed in accordance with a second aspect of the invention.
  • Figures 4 and 5 show pulse diagrams relating to alternative systems for sensing optical fibre deformation.
  • the drawing of Figure 1 shows two optical fibres 10 and 11 which may be single or multimode and are of equal diameter.
  • the fibre 10 in this example is shown to be straight, although this is not essential, and is intended to form the main transmission path for coherent light pulses.
  • the fibre 11 in this example is shown curved, although this is not essential, and forms a reflector.
  • the second fibre adjoins the first fibre and is optically coupled thereto by for example fusion.
  • One end of the fibre 11 is provided with a reflective mirror 12 which may be a discrete device or alternatively the end surface may be adapted to reflect light back along the fibre by for example silvering of the end surface e.g. by dipping in a silver solution or vacuum coating by sputtering.
  • the other end of the fibre 11 is arranged to be dispersive so that significant light is not reflected.
  • Such dispersion can be effected by forming that end by a bad break of the fibre and/or by applying an adhesive which solidifies thereon and is light dispersive.
  • each two-pulse light signal reaches the first reflector 25 a small proportion of the signal will be reflected back along the fibre 24 to the beam splitter 23 which directs the signal to a photodetector 32.
  • the remaining part of the two-pulse signals travels on to reflector 26 at which a further small proportion thereof will be reflected back along the optical fibre 24 to the detector 32.
  • This procedure continues until that part of the two-pulse signal remaining reaches the last of the reflectors 31 and a small proportion of this signal is again reflected back along the optical fibre to the detector 32.
  • a further two-pulse optical transmission is then made and the cycle repeated.
  • FIG. 4 of the drawing shows by way of example reflections of the two-pulse signals from the reflectors 25, 26 and 27.
  • the reflection from the second reflector 26 in the present example is delayed with respect to the reflection from the first reflector 25 by time T.
  • the delay between the reflections is such that there is total coincidence or at least some overlap between the reflected pulse or frequency F of a later reflected signal with the pulse of frequency F + AF of the preceding reflected signal.
  • the reflected pulses are heterodyned in the square law photodetector 32 to produce beat or modulated signals as shown and the phase modulation of these signal will vary in dependence upon variations in length of the optical fibre elements. Accordingly, by detecting and measuring the phase modulation of the beat signals by means of a phase detector 33 changes in length of the optical fibre elements and thus deformation forces acting on these elements can be measured.
  • FIG. 5 of the drawings shows the pulse diagram of an alternative sensing system in which the pulsed laser will produce at predetermined intervals one or two closely spaced pulses of the same frequency which constitute the signals fed to the optical fibre 24 ( Figure 3) without the intervention of the optical switch means 22 ( Figure 3) .
  • the signals reflected from the reflectors 25, 26 and 27 will be as shown in Figure 5.
  • the reflected signals are homodyned and the changes in amplitude of the electrical signals produced by changes in length of the optical fibre elements will be detected by the photodetector 32 ( Figure 3) .
  • the phase detector 33 is not required for this embodiment.
  • the free end of the optical fibre including the reflectors 25 to 31 may be trailed through the water and provide a beamforming acoustic wave sensor array which responds to acoustic waves impinging on the optical fibre sensing elements to produce variations in the lengths thereof which will be measured in the manner described.
  • a beamforming acoustic wave sensor array which responds to acoustic waves impinging on the optical fibre sensing elements to produce variations in the lengths thereof which will be measured in the manner described.
  • this enables a single optical fibre sensor to be used as a beamforming array instead of using a plurality of separate sensors which can be inconvenient and expensive.
  • the simple and relatively cheap provision of a beamforming acoustic sensor array as described also has the advantage of requiring access to one end only of the optical fibre which facilitates trailing of the fibre behind a vessel and which is compatible with the desensitisation of that part of the optical fibre between the signal generating and phase detection means and the fibre sensing elements.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)

Abstract

Un réflecteur à fibres optiques comprend une paire de fibres (10, 11) mutuellement reliées en un point intermédiaire par rapport à leurs extrémités afin de permettre un couplage optique entre elles. L'une des fibres (11) comporte une terminaison réflectrice (12) à une extrémité et une terminaison dispersant la lumière à l'extrémité opposée.
PCT/GB1991/001820 1990-10-19 1991-10-17 Reflecteur a fibres optiques WO1992007236A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9022739A GB2248928A (en) 1990-10-19 1990-10-19 Optical fibre reflector
GB9022739.8 1990-10-19

Publications (1)

Publication Number Publication Date
WO1992007236A1 true WO1992007236A1 (fr) 1992-04-30

Family

ID=10683990

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1991/001820 WO1992007236A1 (fr) 1990-10-19 1991-10-17 Reflecteur a fibres optiques

Country Status (3)

Country Link
AU (1) AU8730891A (fr)
GB (1) GB2248928A (fr)
WO (1) WO1992007236A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2734373A1 (fr) * 1995-05-19 1996-11-22 Gaz De France Coupleur optique a taux de derivation variable et utilisation en tant que capteur
EP0895075A3 (fr) * 1997-07-31 1999-10-20 Litton Systems, Inc. Réseau de capteurs de pression optiques, non-acoustiques, à multiplexage par division de temps
WO2000012977A1 (fr) * 1998-09-01 2000-03-09 Input/Output, Inc. Systeme optoacoustique recursif de detection sismique
EP1912049A1 (fr) * 2006-10-13 2008-04-16 AT&T Corp. Procédé et appareil pour la capture acoustique à l'aide d'impulsions optiques multiples
EP1912050A1 (fr) * 2006-10-13 2008-04-16 AT&T Corp. Procédé et appareil pour la capture acoustique à l'aide d'impulsions optiques multiples

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5297224A (en) * 1992-08-14 1994-03-22 Litton Systems, Inc. Optically switched sensor array

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2152689A (en) * 1984-01-11 1985-08-07 Plessey Co Plc Optical fibre sensing apparatus
US4545253A (en) * 1983-08-29 1985-10-08 Exxon Production Research Co. Fiber optical modulator and data multiplexer
US4673270A (en) * 1985-06-28 1987-06-16 Amp Incorporated Channel add/drop filter-coupler
EP0231635A2 (fr) * 1986-01-07 1987-08-12 Litton Systems, Inc. Dispositif de dérivation pour ligne de bus bidirectionnelle à fibre optique
EP0277698A2 (fr) * 1987-02-02 1988-08-10 Litton Systems, Inc. Méthode et arrangement de mesure avec des détecteurs fibreoptiques

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4545253A (en) * 1983-08-29 1985-10-08 Exxon Production Research Co. Fiber optical modulator and data multiplexer
GB2152689A (en) * 1984-01-11 1985-08-07 Plessey Co Plc Optical fibre sensing apparatus
US4673270A (en) * 1985-06-28 1987-06-16 Amp Incorporated Channel add/drop filter-coupler
EP0231635A2 (fr) * 1986-01-07 1987-08-12 Litton Systems, Inc. Dispositif de dérivation pour ligne de bus bidirectionnelle à fibre optique
EP0277698A2 (fr) * 1987-02-02 1988-08-10 Litton Systems, Inc. Méthode et arrangement de mesure avec des détecteurs fibreoptiques

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2734373A1 (fr) * 1995-05-19 1996-11-22 Gaz De France Coupleur optique a taux de derivation variable et utilisation en tant que capteur
EP0895075A3 (fr) * 1997-07-31 1999-10-20 Litton Systems, Inc. Réseau de capteurs de pression optiques, non-acoustiques, à multiplexage par division de temps
WO2000012977A1 (fr) * 1998-09-01 2000-03-09 Input/Output, Inc. Systeme optoacoustique recursif de detection sismique
EP1912049A1 (fr) * 2006-10-13 2008-04-16 AT&T Corp. Procédé et appareil pour la capture acoustique à l'aide d'impulsions optiques multiples
EP1912050A1 (fr) * 2006-10-13 2008-04-16 AT&T Corp. Procédé et appareil pour la capture acoustique à l'aide d'impulsions optiques multiples
US7742157B2 (en) 2006-10-13 2010-06-22 At&T Intellectual Property Ii, L.P. Method and apparatus for acoustic sensing using multiple optical pulses
US7764363B2 (en) 2006-10-13 2010-07-27 At&T Intellectual Property Ii, L.P. Method and apparatus for acoustic sensing using multiple optical pulses
US9768863B2 (en) 2006-10-13 2017-09-19 At&T Intellectual Property Ii, L.P. Method and apparatus for acoustic sensing using multiple optical pulses
US9787394B2 (en) 2006-10-13 2017-10-10 At&T Intellectual Property Ii, L.P. Method and apparatus for acoustic sensing using multiple optical pulses
US10447388B2 (en) 2006-10-13 2019-10-15 At&T Intellectual Property Ii, L.P. Method and apparatus for detecting a disturbance in a medium
US10454573B2 (en) 2006-10-13 2019-10-22 At&T Intellectual Property Ii, L.P. Method and apparatus for detecting a disturbance in a medium
US10623091B2 (en) 2006-10-13 2020-04-14 At&T Intellectual Property Ii, L.P. Method and apparatus for detecting a disturbance in a medium using threshold based detection
US10623092B2 (en) 2006-10-13 2020-04-14 At&T Intellectual Property Ii, L.P. Method and apparatus for detecting a disturbance in a medium using threshold based detection
US10972180B2 (en) 2006-10-13 2021-04-06 At&T Intellectual Property Ii, L.P. Method and apparatus for detecting a disturbance in a medium
US10972181B2 (en) 2006-10-13 2021-04-06 At&T Intellectual Property Ii, L.P. Method and apparatus for detecting a disturbance in a medium
US11431409B2 (en) 2006-10-13 2022-08-30 At&T Intellectual Property Ii, L.P. Method and apparatus for detecting a disturbance in a medium based on shifted filtered phase information for a plurality of fixed locations
US11438059B2 (en) 2006-10-13 2022-09-06 At&T Intellectual Property Ii, L.P. Method and apparatus for detecting a disturbance in a medium based on shifted filtered phase information for a plurality of locations

Also Published As

Publication number Publication date
GB2248928A (en) 1992-04-22
GB9022739D0 (en) 1991-06-12
AU8730891A (en) 1992-05-20

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