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
  • G02B6/24—Coupling light guides
  • G02B6/42—Coupling light guides with opto-electronic elements
  • G02B6/4201—Packages, e.g. shape, construction, internal or external details
  • G02B6/4246—Bidirectionally operating package structures
• • 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
  • G01D5/3537—Optical fibre sensor using a particular arrangement of the optical fibre itself
  • G01D5/3538—Optical fibre sensor using a particular arrangement of the optical fibre itself using a particular type of fiber, e.g. fibre with several cores, PANDA fiber, fiber with an elliptic core or the like
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
  • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
  • G01N21/43—Refractivity; Phase-affecting properties, e.g. optical path length by measuring critical angle
  • G01N21/431—Dip refractometers, e.g. using optical fibres
• • 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
  • G02B6/02052—Optical fibres with cladding with or without a coating comprising optical elements other than gratings, e.g. filters
• • 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
  • G02B6/255—Splicing of light guides, e.g. by fusion or bonding
• • 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
  • G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
  • G02B6/266—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting the optical element being an attenuator
• • 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
  • G02B6/2821—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 using lateral coupling between contiguous fibres to split or combine optical signals
  • G02B6/2835—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 using lateral coupling between contiguous fibres to split or combine optical signals formed or shaped by thermal treatment, e.g. couplers
• • 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
  • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
  • G02B6/29331—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by evanescent wave coupling
  • G02B6/29332—Wavelength selective couplers, i.e. based on evanescent coupling between light guides, e.g. fused fibre couplers with transverse coupling between fibres having different propagation constant wavelength dependency
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/011—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/011—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass
  • G02F1/0115—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass in optical fibres
  • G02F1/0118—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass in optical fibres by controlling the evanescent coupling of light from a fibre into an active, e.g. electro-optic, overlay

Definitions

• optical fibre couplers can be fabricated by imparting a biconical taper to a monomode optical fibre. With the aid of such tapering the core HE-., mode can couple into the HE-- mode of the tube waveguide, which is formed due to the cladding, in an efficient manner.
• the present invention has for an object to utilise optical fibres having such biconical tapers to form devices, including sensing devices and tuneable attenuators, which are simple to manufacture and which incorporate low cost electronics.
• the present invention consists in an optical fibre device comprising a monomode optical fibre having an optical coupler fabricated therein in the form of a biconical tapered portion, means for modifying the refractive index of a medium surrounding the tapered portion so that for a specified wavelength travelling along the fibre the power transmitted will vary in accordance with variation in the refractive index of the medium, and means for detecting light transmitted by the core of the optical fibre.
• Figure 1 shows various refractive index profiles taken across the diameter of optical fibres suitable for use in sensors according to the present invention
• Figure 2 is a plot of transmitted power against extension of an optical fibre dum ' ng the process of producing a biconical taper in the fibre
• Figure 3 is a plot similar to Figure 2 showing the effect of stopping extension at a selected point
• Figure 4 is a plot showing the refractive index response of the taper, the refractive index varying in response to temperature variations
• Figure 5 is a diagram showing how a temperature-linked refractive index variation can be applied to a tapered fibre to make a fuseable attenuator
• Figure 6 is a plot of the refractive index response of a tapered fibre at a second wavelength
• Figure 7 is a diagram of a sensing device
• Figures 8 to 10 are vaious plots again showing the responses obtained to varying degrees of taper and surrounding refractive indices.
• the refractive index profiles shown in Figure 1 show some of the types of single mode optical fibres which can be utilised in carrying out the present invention.
• the profiles a, b, c, d, e and f respectively relate to Matched, Depressed, Quadruple Clad, Segmented Core and Raised Cladding optical fibres.
• All these types of fibre can be formed into coaxial couplers by the process described in our co-pending U.K. Application No. 8519086 entitled "Coaxial Couplers".
• laser light is launched into one end of an optical fibre and the transmitted power detected at the other end. Whilst the light is being transmitted a portion of the fibre is simultaneously heated and elongated, generating a biconical taper in the fibre.
• the light guided in the core of the single mode fibre is directed into the tapered section.
• the tapering being applied causes the tapered portion to become a multi-mode section, and interference of thelocal HE.. and HE-- modes causespower transfer along the taper.
• a tapered optical coupler produced by this procedure can be incorporated in a range of sensing devices by utilising the refractive index response of the tapers. Then if the tapered portion is immersed in a liquid such as silicone oil, which has a higher refractive index than silica, and the liquid is heated so that its refractive index varies the response of the taper to light of a particular wavelength will vary. This variation is shown in the plot of Figure 4. From this plot it can be seen that there is maximum power transmission at point A. This is at a temperature of 29 C. At higher temperatures the power throughput decreases almost linearly as temperature rises. Thus point B shows power transmission at 55 C.
• the section A-B of the plot can be used to provide a sensor with relatively low sensitivity and good dynamic range in which a change of refractive index of the order of 10 corresponds to a change in temperature of approximately 30 C, and requiring a detection sensit- ivity range of ⁇ " ⁇ 20 dB.
• These figures provide the basis for an intensity sensor for the measurement of temperature, refractive index, acoustic, biological and other sensors which directly or indirectly use this refractive index and intensity relation.
• FIG. 6 is a plot of the refractive index response of the same taper at a second wavelength when subjected to the same changes in refractive index as caused the plot of Figure 4. It will be seen here that the linear slope A-B of Figure 4 has been replaced by a substantially constant plateau. It is the ability of a single fibre to give two such separate results which enables a compensating factor to be built in to a sensor.
• Such a compensated sensor is shown" in Figure 7.
• Laser light at two differing wavelengths , A- is launched down a single monomode optical fibre 10 which has a biconical taper imparted to it at 11 and which is surrounded by a sensor area generally indicated at 12.
• This sensor area could, for example, be a capillary tube filled with silicone oil as in the embodiment shown in Figure 5.
• the tapered portion 11 will give power transmission plots of the kind shown in Figures 4 and 6 in response to changes in the refractive index of the surrounding sensor area, and in response to light of wavelengths r and respectively.
• the two wavelengths can be launched into the fibre by means of a coupler.
• FIG. 5 shows a tuneable attenuator.
• a monomode optical fibre 1 has a biconical taper fabricated in it in the region generally indicated at 2. This region is housed in a capillary glass tube 3 filled with a liquid such as silicone oil the refractive index of which varies with temperature over the required ranges. The ends of capillary 3 are sealed with UV-cured epoxy resin. The tube is coated with resistive material and provided with electrodes 4 and 5. The application of a voltage across the electrodes causes the heat released to heat the liquid and lower its refractive index, hence varying the transmission through the fibre 1. In this manner a tuneability of >30 dB can be achieved.
• an optical modulator can be constructed using this fact.
• a monomode fibre is surrounded with a material having a refractive index which has.a value selected to provide maximum power transmission.
• the transmission power is rapidly reduced to a minimum, a loss of approximately 30 dB.
• Figure 4 shows a plot which has been derived using a tapered biconical fibre the elongation of which has been stopped after l ⁇ power oscillations. If instead the fabrications of the taper had been extended to two complete power oscillations, as shown in Figure 8, then using this biconiclly tapered fibre to produce a plot in response to changes of refractive index results in the plot of Figure 9. Similarly extending the number of oscillations to 12 produces the equivalent plots of Figures 7 and 8.
• variable refractive index surrounding medium various types of material can be used for the variable refractive index surrounding medium.
• the monomode fibre could be fabricated from a material having a high enough refractive index to match an electro-optic crystal such as KDP. The electro-optic effect could then be used so that the tapered fibre portion and the crystal together act as a modulator. If an electro-optic crystal is used as a cladding medium surrounding the taper it must be grown carefully around the taper. It is possible to grow single KDP crystals long enough to clad the taper region and also to enclose the modulating electrodes.
• low refractive index liquid crystals are used with Si ⁇ 2 guides or with high refractive index glass fibre tapers.
• the necessary change of refractive index of the surrounding medium is 10 "3 .

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Nonlinear Science (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Measuring Temperature Or Quantity Of Heat (AREA)

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• 1986
  • 1986-12-04 EP EP86906909A patent/EP0248052A1/de not_active Withdrawn
  • 1986-12-04 GB GB8629038A patent/GB2184859B/en not_active Expired
  • 1986-12-04 WO PCT/GB1986/000738 patent/WO1987003676A1/en not_active Ceased

Non-Patent Citations (1)

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