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WO1998018030A1 - Fibre optique a reseau de diffraction a sa surface terminale - Google Patents

Fibre optique a reseau de diffraction a sa surface terminale Download PDF

Info

Publication number
WO1998018030A1
WO1998018030A1 PCT/GB1997/002903 GB9702903W WO9818030A1 WO 1998018030 A1 WO1998018030 A1 WO 1998018030A1 GB 9702903 W GB9702903 W GB 9702903W WO 9818030 A1 WO9818030 A1 WO 9818030A1
Authority
WO
WIPO (PCT)
Prior art keywords
fibre
arrangement
signals
face
grating
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/GB1997/002903
Other languages
English (en)
Inventor
Nicolas François René SCHMITT
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Balfour Beatty PLC
Original Assignee
BICC PLC
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 BICC PLC filed Critical BICC PLC
Priority to AU47152/97A priority Critical patent/AU4715297A/en
Publication of WO1998018030A1 publication Critical patent/WO1998018030A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/30—Measuring the intensity of spectral lines directly on the spectrum itself
    • G01J3/36—Investigating two or more bands of a spectrum by separate detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/0218—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using optical fibers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/12—Generating the spectrum; Monochromators
    • G01J3/18—Generating the spectrum; Monochromators using diffraction elements, e.g. grating
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/12—Generating the spectrum; Monochromators
    • G01J3/18—Generating the spectrum; Monochromators using diffraction elements, e.g. grating
    • G01J3/1895—Generating the spectrum; Monochromators using diffraction elements, e.g. grating using fiber Bragg gratings or gratings integrated in a waveguide
    • 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
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02061—Grating external to the fibre and in contact with the fibre, e.g. evanescently coupled, gratings applied to the fibre end

Definitions

  • This invention relates to optical fibres, and especially to arrangements for separating signals at different wavelengths that are carried by the optical fibre.
  • an arrangement which comprises an optical fibre that has a Bragg grating written on an end face thereof, and detecting means located at the end face of the fibre to detect electromagnetic radiation emerging from the end face at different angles with respect to the axis of the fibre, the fibre carrying optical signals at at least two different wavelengths, which signals are diffracted by the Bragg grating so that different signals are detected by the detecting means.
  • the arrangement according to the invention has the advantage that it is possible to separate and detect light of different wavelengths directly from the end of the optical fibre using a single Bragg grating simply by appropriate positioning of the detecting means.
  • the detecting means may, for example, comprise a plurality of detectors oriented at different angles with respect to the axis of the fibre or may, for example, comprise an array of detecting elements (e.g. an array of CCD detecting elements).
  • the grating may be formed by exposing the optical fibre to beams of ultraviolet radiation that may interfere with one another so as to generate a physical periodic structure or a periodic variation of refractive index of the fibre core across its face.
  • the gratings may be formed by a number of methods, for example by a light induced method e.g. as described in US patent No. 4,474,427, a two beam interferometry method e.g. as described in international patent application No. WO 86/01303 or a phase mask method e.g. as described in US patent No. 5,367,588, the disclosures of which are also incorporated herein by reference.
  • the gratings may be written by a point-by-point method in which the radiation is focused to a spot that is moved along the end face of the fibre, thereby enabling gratings with longer pitches to be written.
  • the arrangement according to the invention may be employed with silica (multimode) fibres or with plastics fibres, but is particularly applicable to use with plastics fibres since, among other reasons, it is difficult in the extreme at the present date to couple plastics fibres with other fibres.
  • Such an arrangement may for example, be used in monitoring equipment, for example for monitoring temperature, strain, humidity, presence of specific chemicals, (the measurand) in which the optical fibre transmits one signal that carries information about the measurand, and another signal at a different wavelength for reference pu ⁇ oses in order to compensate the measurand signal for changes in the intensity of the light source, macrobending of the fibre, temperature, strain or any other variation that would affect the output intensity.
  • the measurand in which the optical fibre transmits one signal that carries information about the measurand, and another signal at a different wavelength for reference pu ⁇ oses in order to compensate the measurand signal for changes in the intensity of the light source, macrobending of the fibre, temperature, strain or any other variation that would affect the output intensity.
  • d is the grating period
  • ⁇ is the diffracted angle
  • m is the order of diffraction
  • ⁇ is the wavelength of the radiation.
  • the arrangement according to the invention can, however, be employed in telecommunications applications for wavelength demultiplexing of signals.
  • Figure 1 is a schematic view of the end of a plastics optical fibre having a Bragg grating written thereon;
  • Figure 2 is a schematic view of the end of the optical fibre of figure 1 when light of a single wavelength is sent along it together with a graphical indication of the light intensity;
  • Figure 3a is a schematic view of a measuring system that employs an arrangement according to the invention.
  • Figure 3b is a schematic view of a measuring system which is a modification of the system of Fig. 3a;
  • Figure 4a is a schematic view of a system showing the principle of wavelength demultiplexing according to the invention.
  • Figure 4b is a schematic view of a measuring system which is a modification of the system of Fig. 4a.
  • figure 1 shows the end of a plastics optical fibre 1 having a core 2 of diameter of 980 ⁇ m formed from polymethyl methacrylate (PMMA) and a 10 ⁇ m thick cladding 4 thereon formed from fluorinated PMMA.
  • the end face 6 of the fibre has a Bragg grating written thereon by shining ultraviolet radiation of wavelength 248 nm from an excimer laser at the face through a phase mask.
  • the phase mask has a relief pattern etched written thereon to cause the ultraviolet radiation to form an intensity modulated interference pattern on the end face of the fibre.
  • the period of the interference pattern depends only on the period of the phase mask, so that the resultant photo induced grating has a period equal to half that of the phase mask.
  • Figure 2 shows the effect of transmitting monochromatic light at a wavelength of about 500 nm along the fibre. Most of the light that exits the optical fibre at the end face 6 thereof falls within a light cone 12 whose shape is defined by the numerical aperture of the fibre, while a small part of the light, corresponding to first order diffraction, will fall within a further cone 14 located on either side of the light cone 12 and can be picked up by detectors (not shown).
  • Figure 2 shows, in addition, the intensity of the light that exits the fibre with the intensity shown on the horizontal axis and with the lateral dimensions shown on the vertical axis with the dimensions corresponding to the fibre as shown.
  • Figure 3a shows a measuring system that employs an optical fibre arrangement according to the invention.
  • the system comprises a pair of plastics optical fibres 20 and 21, and a detection zone 22 which contains material to be detected.
  • One of the fibres 20 launches light into the detection zone 22, while the second fibre 21, which is of the type shown in figure 1 having a Bragg grating written on the end thereof remote from the detection zone, collects the light from the detection zone.
  • the fibres are cleaved and kept aligned with a 1mm distance between the fibre ends.
  • detectors in this case detectors 24 and 26
  • detectors 24 and 26 are placed at the end of the second fibre at angles that match the diffracted angles of each of two wavelengths of the light sent along the fibres.
  • the output of one of the detectors 24 and 26 will depend on the concentration of the material that is being detected together with other parameters such as light intensity, macrobending of the fibres, temperature etc. while the output of the other detector will depend only on the other parameters, and can be used as a reference.
  • the system was employed to measure the concentration of methylene blue by employing radiation at wavelengths of 633 nm (to detect the methylene blue) and radiation at a wavelength of 800 nm as a reference.
  • the measuring system of Fig. 3b is very similar to that of Fig. 3a and the same reference numerals have been used for the same features.
  • the modification is that the discrete detectors 14, 26 of Fig. 3a have been replaced with an array 30 of photo detecting elements 32, for example CCD (charge coupled device) photo detectors.
  • CCD charge coupled device
  • Figure 4a shows the principle of wavelength demultiplexing according to the invention in which three signals 41, 42 and 43 which are transmitted along the plastics optical fibre 1 at three different wavelengths.
  • photodetectors 44, 45 and 46 By setting photodetectors 44, 45 and 46 at appropriate angles with respect to the axis of the fibre 1 , the signals in the fibre may be demultiplexed to separate the three original signals 41 ,42 and 43.
  • the measuring system of Fig. 4b is very similar to that of Fig. 4a and the same reference numerals have been used for the same features.
  • the modification is that the discrete detectors 44, 45 and 46 of Fig. 4a have been replaced with an array 30 of photo detecting elements 32, for example CCD (charge coupled device) photo detectors.
  • CCD charge coupled device
  • any number of wavelengths may be transmitted along the optical fibre and subsequently detected after diffraction at the fibre end, subject to the appropriate number of detectors 24, 26, 44, 45 46 or subject to the provision of an appropriate array of detecting elements 32.

Landscapes

  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Transform (AREA)

Abstract

L'invention concerne une fibre (1) optique qui comporte une surface (6) terminale présentant un réseau de Bragg formé sur celle-ci. Un dispositif comprenant ladite fibre présente une multiplicité de détecteurs (24, 26; 44, 45, 46; 28, 30), situés sur la surface terminale de la fibre, afin de détecter la lumière qui émerge à des angles différents par rapport à l'axe de ladite fibre. Cette fibre est porteuse de signaux optiques à au moins deux longueurs d'onde différentes. Ces signaux sont diffractés par le réseau de Bragg, de sorte que différents signaux sont détectés par les moyens de détection. Un dispositif similaire peut être utilisé pour le démultiplexage de signaux à des longueurs d'onde différentes, ou dans des applications de détection, dans lesquelles la lumière de différentes longueurs d'onde est utilisée pour porter des signaux contenant des informations sur la mesure et pour porter des signaux de référence.
PCT/GB1997/002903 1996-10-21 1997-10-21 Fibre optique a reseau de diffraction a sa surface terminale Ceased WO1998018030A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU47152/97A AU4715297A (en) 1996-10-21 1997-10-21 Optical fibre with a grating on its end face

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9621907A GB2318412A (en) 1996-10-21 1996-10-21 Optical fibre arrangement incorporating Bragg grating
GB9621907.6 1996-10-21

Publications (1)

Publication Number Publication Date
WO1998018030A1 true WO1998018030A1 (fr) 1998-04-30

Family

ID=10801749

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1997/002903 Ceased WO1998018030A1 (fr) 1996-10-21 1997-10-21 Fibre optique a reseau de diffraction a sa surface terminale

Country Status (3)

Country Link
AU (1) AU4715297A (fr)
GB (1) GB2318412A (fr)
WO (1) WO1998018030A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2385426A (en) * 2001-11-26 2003-08-20 Bookham Technology Plc Optic chip control method and system
EP1376790A1 (fr) * 2002-06-28 2004-01-02 Agilent Technologies, Inc., a corporation of the State of Delaware Dispositif de verrouillage de longeurs d'onde pour un laser accordable
US8730466B2 (en) 2011-07-14 2014-05-20 Thermo Electron Scientific Instruments Llc Optical spectrometer with underfilled fiber optic sample interface

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4567366A (en) * 1982-09-25 1986-01-28 Showa Denko Kabushiki Kaisha Method and apparatus for measuring methane concentration in gas
JPS61122613A (ja) * 1984-11-20 1986-06-10 Fujitsu Ltd 光分波素子
GB2189901A (en) * 1986-04-25 1987-11-04 Stc Plc Laser-induced fibre grating devices
JPH01193805A (ja) * 1988-01-29 1989-08-03 Sharp Corp 光通信装置
EP0352751A2 (fr) * 1988-07-26 1990-01-31 Fuji Photo Film Co., Ltd. Dispositif de conversion de longueur d'onde optique et module convertisseur de longueur d'onde optique
US4911516A (en) * 1989-02-27 1990-03-27 General Electric Company Optical device with mode selecting grating
EP0395060A2 (fr) * 1989-04-28 1990-10-31 Nippon Telegraph and Telephone Corporation Récepteur optique
US5245404A (en) * 1990-10-18 1993-09-14 Physical Optics Corportion Raman sensor

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4274706A (en) * 1979-08-30 1981-06-23 Hughes Aircraft Company Wavelength multiplexer/demultiplexer for optical circuits
GB2219869B (en) * 1988-06-15 1992-10-14 British Telecomm Optical coupling device
US5082629A (en) * 1989-12-29 1992-01-21 The Board Of The University Of Washington Thin-film spectroscopic sensor

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4567366A (en) * 1982-09-25 1986-01-28 Showa Denko Kabushiki Kaisha Method and apparatus for measuring methane concentration in gas
JPS61122613A (ja) * 1984-11-20 1986-06-10 Fujitsu Ltd 光分波素子
GB2189901A (en) * 1986-04-25 1987-11-04 Stc Plc Laser-induced fibre grating devices
JPH01193805A (ja) * 1988-01-29 1989-08-03 Sharp Corp 光通信装置
EP0352751A2 (fr) * 1988-07-26 1990-01-31 Fuji Photo Film Co., Ltd. Dispositif de conversion de longueur d'onde optique et module convertisseur de longueur d'onde optique
US4911516A (en) * 1989-02-27 1990-03-27 General Electric Company Optical device with mode selecting grating
EP0395060A2 (fr) * 1989-04-28 1990-10-31 Nippon Telegraph and Telephone Corporation Récepteur optique
US5245404A (en) * 1990-10-18 1993-09-14 Physical Optics Corportion Raman sensor

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 010, no. 308 (P - 508) 21 October 1986 (1986-10-21) *
PATENT ABSTRACTS OF JAPAN vol. 013, no. 488 (P - 954) 7 November 1989 (1989-11-07) *

Also Published As

Publication number Publication date
GB2318412A (en) 1998-04-22
AU4715297A (en) 1998-05-15
GB9621907D0 (en) 1996-12-11

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