WO1998018030A1 - Optical fibre with a grating on its end face - Google Patents
Optical fibre with a grating on its end face Download PDFInfo
- 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
Links
- 239000013307 optical fiber Substances 0.000 title claims abstract description 18
- 239000000835 fiber Substances 0.000 claims abstract description 37
- 230000003287 optical effect Effects 0.000 claims abstract description 5
- 239000004033 plastic Substances 0.000 claims description 8
- 229920003023 plastic Polymers 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- 238000005253 cladding Methods 0.000 claims description 3
- 230000005670 electromagnetic radiation Effects 0.000 claims description 2
- 239000000377 silicon dioxide Substances 0.000 claims description 2
- 230000005855 radiation Effects 0.000 description 8
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 7
- 239000004926 polymethyl methacrylate Substances 0.000 description 7
- 238000001514 detection method Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 5
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- RBTBFTRPCNLSDE-UHFFFAOYSA-N 3,7-bis(dimethylamino)phenothiazin-5-ium Chemical compound C1=CC(N(C)C)=CC2=[S+]C3=CC(N(C)C)=CC=C3N=C21 RBTBFTRPCNLSDE-UHFFFAOYSA-N 0.000 description 2
- 229960000907 methylthioninium chloride Drugs 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 1
- 238000005305 interferometry Methods 0.000 description 1
- 239000011295 pitch Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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.
Abstract
Description
Claims
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 |
---|---|---|---|
GB9621907.6 | 1996-10-21 | ||
GB9621907A GB2318412A (en) | 1996-10-21 | 1996-10-21 | Optical fibre arrangement incorporating Bragg grating |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1998018030A1 true WO1998018030A1 (en) | 1998-04-30 |
Family
ID=10801749
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1997/002903 WO1998018030A1 (en) | 1996-10-21 | 1997-10-21 | Optical fibre with a grating on its end face |
Country Status (3)
Country | Link |
---|---|
AU (1) | AU4715297A (en) |
GB (1) | GB2318412A (en) |
WO (1) | WO1998018030A1 (en) |
Families Citing this family (3)
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 (en) * | 2002-06-28 | 2004-01-02 | Agilent Technologies, Inc., a corporation of the State of Delaware | Tunable laser wavelength locker |
US8730466B2 (en) * | 2011-07-14 | 2014-05-20 | Thermo Electron Scientific Instruments Llc | Optical spectrometer with underfilled fiber optic sample interface |
Citations (8)
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 (en) * | 1984-11-20 | 1986-06-10 | Fujitsu Ltd | Optical demultiplexing element |
GB2189901A (en) * | 1986-04-25 | 1987-11-04 | Stc Plc | Laser-induced fibre grating devices |
JPH01193805A (en) * | 1988-01-29 | 1989-08-03 | Sharp Corp | Optical communication equipment |
EP0352751A2 (en) * | 1988-07-26 | 1990-01-31 | Fuji Photo Film Co., Ltd. | Optical wavelength converter device and optical wavelength converter module |
US4911516A (en) * | 1989-02-27 | 1990-03-27 | General Electric Company | Optical device with mode selecting grating |
EP0395060A2 (en) * | 1989-04-28 | 1990-10-31 | Nippon Telegraph and Telephone Corporation | Optical receiver |
US5245404A (en) * | 1990-10-18 | 1993-09-14 | Physical Optics Corportion | Raman sensor |
Family Cites Families (3)
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 |
-
1996
- 1996-10-21 GB GB9621907A patent/GB2318412A/en not_active Withdrawn
-
1997
- 1997-10-21 WO PCT/GB1997/002903 patent/WO1998018030A1/en active Application Filing
- 1997-10-21 AU AU47152/97A patent/AU4715297A/en not_active Abandoned
Patent Citations (8)
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 (en) * | 1984-11-20 | 1986-06-10 | Fujitsu Ltd | Optical demultiplexing element |
GB2189901A (en) * | 1986-04-25 | 1987-11-04 | Stc Plc | Laser-induced fibre grating devices |
JPH01193805A (en) * | 1988-01-29 | 1989-08-03 | Sharp Corp | Optical communication equipment |
EP0352751A2 (en) * | 1988-07-26 | 1990-01-31 | Fuji Photo Film Co., Ltd. | Optical wavelength converter device and optical wavelength converter module |
US4911516A (en) * | 1989-02-27 | 1990-03-27 | General Electric Company | Optical device with mode selecting grating |
EP0395060A2 (en) * | 1989-04-28 | 1990-10-31 | Nippon Telegraph and Telephone Corporation | Optical receiver |
US5245404A (en) * | 1990-10-18 | 1993-09-14 | Physical Optics Corportion | Raman sensor |
Non-Patent Citations (2)
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 |
---|---|
AU4715297A (en) | 1998-05-15 |
GB9621907D0 (en) | 1996-12-11 |
GB2318412A (en) | 1998-04-22 |
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