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WO2001001174A1 - Procede de fabrication de reseau de fibres, composant pour communication optique et capteur de temperature - Google Patents

Procede de fabrication de reseau de fibres, composant pour communication optique et capteur de temperature Download PDF

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Publication number
WO2001001174A1
WO2001001174A1 PCT/JP2000/004219 JP0004219W WO0101174A1 WO 2001001174 A1 WO2001001174 A1 WO 2001001174A1 JP 0004219 W JP0004219 W JP 0004219W WO 0101174 A1 WO0101174 A1 WO 0101174A1
Authority
WO
WIPO (PCT)
Prior art keywords
grating
fiber
core
coating layer
temperature
Prior art date
Application number
PCT/JP2000/004219
Other languages
English (en)
Japanese (ja)
Inventor
Kazuo Imamura
Takeshi Genji
Norio Naka
Satoshi Uramatsu
Katsuaki Kondo
Original Assignee
Mitsubishi Cable Industries, Ltd.
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
Priority claimed from JP11183612A external-priority patent/JP2001013333A/ja
Priority claimed from JP11220826A external-priority patent/JP2001042142A/ja
Application filed by Mitsubishi Cable Industries, Ltd. filed Critical Mitsubishi Cable Industries, Ltd.
Publication of WO2001001174A1 publication Critical patent/WO2001001174A1/fr

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Classifications

    • 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
    • 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
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/02195—Refractive index modulation gratings, e.g. Bragg gratings characterised by means for tuning the grating
    • G02B6/02204—Refractive index modulation gratings, e.g. Bragg gratings characterised by means for tuning the grating using thermal effects, e.g. heating or cooling of a temperature sensitive mounting body
    • 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
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
    • G02B2006/02161—Grating written by radiation passing through the protective fibre coating

Definitions

  • the present invention relates to a method for manufacturing a fiber grating in which the core of an optical fiber has a striped refractive index distribution, an optical communication component having a fiber grating, and a temperature sensor.
  • a fiber grating is manufactured by forming a periodic refractive index modulation structure on the core of an optical fiber by a two-beam interference method or a phase mask method (Japanese Patent Application Laid-Open No. Hei 6-235808, Japanese Patent Application Laid-Open No. — Refer to Japanese Patent Application Laid-Open No. 140301 / Patent No. 2521078).
  • a coherent ultraviolet laser beam is applied to silica glass (core) doped with germanium (Ge) to cause a photo-induced refractive index change in a corresponding portion, thereby causing a change in the refractive index.
  • Fiber gratings used for these various applications are required to have predetermined transmission characteristics as a required function, and naturally have predetermined mechanical strength characteristics regardless of the application. Is important for practical use.
  • the optical fiber on which the grating is written is typically a core and a cladding.
  • the outer peripheral surface of the optical fiber consisting of the following is coated with a coating layer of an ultraviolet curable resin that absorbs ultraviolet rays and causes a curing reaction.
  • an interferometry or a phase mask method is used, the mechanical strength characteristic tends to decrease because the coating is usually performed in a state where the coating layer of the portion to be written is removed. For this reason, after the writing of the grating is completed, the portion where the coating layer is removed is re-coated.
  • a processing technique for re-coating such as re-coating or packaging is required.
  • the outer surface of the optical fiber comes into contact with the outside air, and the optical fiber is deteriorated due to contact with air during the writing operation. Transmission characteristics may be degraded.
  • the removal of the coating layer at the portion to be written is performed not by mechanical means but by a chemical treatment of dissolving with a chemical, for example, to prevent damage to the optical fiber. Therefore, it is a factor that hinders the efficiency of mass processing of grating writing.
  • the effective writing of the grating by irradiating ultraviolet rays from outside the coating layer without removing the coating layer requires the core of the optical fiber to be written. It is conceivable to increase the sensitivity (photosensitivity) to the light-induced refractive index change of the part.
  • photosensitivity photosensitivity
  • a normal density a relative refractive index difference between the core and the clad is, for example, 0.9%).
  • short-period gratings with a grating pitch of about 1 m or less reflect light of a specific wavelength (peak wavelength) corresponding to the grating pitch.
  • peak wavelength B of the reflected light from the grating is expressed by the following equation (1).
  • the peak wavelength of the reflected light from the fiber grating is, for example, a water wave, 0 plus E, No. 2 0 5, 8 1-84 (1996) and Gupta et al., Applied 0 ptics, 35 (2 5), 52 0 2-52 0 5 (1996) ing.
  • IB the reflection peak wavelength
  • the conventional temperature sensor for use near room temperature or for cryogenic temperature
  • a substrate with a large coefficient of thermal expansion for example, aluminum substrate or acrylic substrate
  • the quartz fiber was fixed.
  • a temperature sensor for high temperature (0 ° C to 800 ° C)
  • a temperature sensor having a structure in which a fiber is not fixed to a substrate is also known.
  • the sensor becomes relatively large and it becomes difficult to deform (for example, bend) the external shape of the sensor. There is a problem that the place to install is limited.
  • the conventional temperature sensors for low temperature and normal temperature described above use uncoated fibers, the mechanical strength at cryogenic temperatures is weak, handling is difficult, and it is difficult to use for a long period of time. there were.
  • the fiber has a large difference in thermal expansion coefficient between the substrate and the fiber.
  • the rate of change of the reflection peak wavelength of the sensor with respect to temperature changes greatly depending on the temperature, there is a problem that the measurable temperature range is narrow.
  • the present invention has been made in view of the circumstances described above, and one of the main objects of the present invention is to provide a method of manufacturing a fiber grating in which a grating is written in a state where the photosensitivity of glass is increased. To provide.
  • Another main object of the present invention is to provide a component for optical communication that can more effectively utilize the performance of the fiber grating manufactured as described above.
  • another main object of the present invention is to provide a fiber grating which can be suitably used for a temperature sensor capable of measuring a temperature up to a very low temperature with a simple structure without requiring a package structure. —To provide a manufacturing method of a laser and a temperature sensor using such a fiber grating. Disclosure of the invention
  • a method of manufacturing a fiber grating according to the present invention includes a step of covering an outer peripheral surface of a fiber including a core on which a grating is to be written and a cladding surrounding the core with a coating layer formed of an ultraviolet-transmissive resin; Writing a grating in the core by irradiating the core from outside of the coating layer, wherein the grating is written in the core.
  • the core is irradiated with the ultraviolet ray in a state where a strain of + 0.8% or more and + 6% or less is generated in the direction.
  • the step of writing the grating on the core it is preferable to execute the writing of the grating while applying an axial tension to the core. After executing the writing of the grating, it is preferable to release the axial tension. .
  • An optical communication component is characterized by comprising: a fiber grating manufactured by any one of the fiber grating manufacturing methods described above; and means for supporting the fiber grating.
  • the means for supporting the fiber grating supports the fiber grating so that a strain smaller than an axial strain applied to the core is generated in a step of writing the grating on the core.
  • the method for manufacturing a fiber grating according to the present invention is a method for manufacturing a fiber grating, comprising: a fiber strand having a core and a cladding; and a coating layer covering a surface of the fiber strand.
  • the selection of the resin material and the setting of the thickness of the coating layer are performed based on the elastic modulus and the thermal expansion coefficient of the fiber and the elastic modulus and the thermal expansion coefficient of the resin material. The process may be performed.
  • the rate of change of the reflection peak wavelength with respect to temperature change may be constant in the range of 196 ° C. to + 170 ° C.
  • the rate of change of the reflection peak wavelength with respect to temperature change is the change of the reflection peak wavelength of the grating formed on the uncoated fiber strand with respect to the temperature change at ⁇ 20 ° (: to + 60 ° C.). It may be the same as the rate.
  • the temperature sensor according to the present invention includes: a fiber element having a core and a clad; a fiber grating having a coating layer covering a surface of the fiber element; a light source that emits light to the fiber element; A temperature sensor that receives the reflected light from the fiber grating and detects a wavelength of the reflected light, wherein a rate of change of the wavelength of the reflected light with respect to a temperature change is from ⁇ 196 ° C. It is constant within the range of 170 ° C.
  • FIG. 1 is a diagram illustrating a principle of manufacturing a fiber grating according to an embodiment of the present invention.
  • FIG. 2 is an enlarged cross-sectional view of the optical fiber.
  • FIG. 3 is a schematic diagram showing a manufacturing apparatus.
  • FIG. 4 is a graph showing the relationship between the applied tension at the time of writing the grating and the grating fabrication time.
  • FIG. 5 is a graph showing the relationship between the applied tension at the time of writing the grating and the grating formation speed.
  • FIG. 6 is a graph showing the relationship between the tension applied to the fiber to be irradiated, the final arrival reflectance during fabrication, and the reflectance when the tension of the fiber is released after fabrication.
  • Figure 7 is a graph showing the relationship between the applied tension and the increase (%) in reflectance due to release of the tension.
  • FIG. 8 is an enlarged explanatory view of the tension applying mechanism of FIG.
  • FIG. 9 is an enlarged sectional view taken along line AA of FIG.
  • FIG. 10 is a diagram showing a positional relationship between an optical fiber core and a cylindrical lens system.
  • FIG. 11 is a graph showing the temperature dependence of the reflection peak wavelength of the fiber grating according to the embodiment of the present invention.
  • FIG. 12 is a schematic diagram showing a temperature sensor using the fiber grating according to the embodiment of the present invention.
  • FIG. 1 shows an optical fiber core 1 of a predetermined length to be subjected to the grating writing.
  • the optical fiber core 1 is composed of a core 2 on which a grating 21 is written, a cladding 3 formed around the core 2, and a coating layer 4 covering the outer surface of the cladding 3.
  • the coating layer 4 was coated on the optical fiber 1 ′ composed of the core 2 and the clad 3 made by drawing from the optical fiber preform. Things.
  • Ultraviolet laser light as ultraviolet rays is irradiated from outside the coating layer 4 through the phase mask 5, so that the core 2 of the optical fiber core 1 has a periodic refractive index modulation in the fiber axis direction.
  • the stripes (gratings) are written to create a fire bug rating.
  • the interval between these many refractive index modulation fringes is the grating pitch.
  • the core 2 is doped with Ge having a concentration similar to that of the Ge contained in the core of the normal specification optical fiber.
  • the normal specification optical fiber is an optical fiber core connected to the optical fiber core 1.
  • Such an optical fire The core of the core wire is usually doped with Ge so that the relative refractive index difference is about 0.9%.
  • the core 2 of the optical fiber core 1 shown in the figure in addition to Ge, Sn,! !
  • the core 2 is doped with dopants of Sn, Al, and B.
  • a concentration of 1000 O ppm or more, preferably 10,000 to 15000 ppm Sn or Sn at such a concentration and A 1 at a concentration of 1000 ppm or less may be co-doped.
  • Such de one-flop may be performed by various known methods, for example, when carried out by immersion, the compound of the Sn (For Sn, for example, S n C 1 2 ⁇ 2 H 2 0) of methyl alcohol And dipped in the solution.
  • the coating layer 4 is formed so as to have a thickness of at least about 30 ⁇ m by a single coating method following the step of drawing the optical fiber 1 ′ including the core 2 and the clad 3.
  • the material of the coating layer 4 has both a property of curing with ultraviolet light of a certain wavelength band (first ultraviolet light) and a property of transmitting ultraviolet light of another wavelength band (second ultraviolet light).
  • first ultraviolet light a certain wavelength band
  • second ultraviolet light another wavelength band
  • Such a resin may be referred to as “ultraviolet-transmissive ultraviolet-curable resin” in the present specification.
  • the ultraviolet-transmissive ultraviolet-curing resin transmits at least ultraviolet rays of a specific wavelength band (for example, a wavelength band of 240 nm to 270 nm) to be irradiated to the core for writing the grating 21 (preferably, almost all of the ultraviolet rays are absorbed) On the other hand, it absorbs ultraviolet light having a wavelength shorter or longer than the specific wavelength band to cause a curing reaction.
  • a specific wavelength band for example, a wavelength band of 240 nm to 270 nm
  • it absorbs ultraviolet light having a wavelength shorter or longer than the specific wavelength band to cause a curing reaction.
  • the same resin has different UV absorption characteristics depending on the wavelength, it is a UV-transmitting type resin in a specific wavelength band, and a UV-curable resin in a shorter or longer wavelength range than the above specific wavelength band.
  • the coating layer 4 is formed.
  • a photoinitiator (a photo-initiator (a photo-initiator) that initiates and promotes a curing reaction by receiving ultraviolet rays in a wavelength range shorter than 240 nm or a wavelength range longer than 270 nm is applied to urethane acrylate or epoxy acrylate. Initiator Evening)
  • the resin containing is used as “ultraviolet transparent ultraviolet curing resin”.
  • the coating layer is irradiated with first ultraviolet rays to cure the coating layer 4.
  • an ultraviolet curing resin is used.
  • the first ultraviolet irradiation step is omitted, and another resin curing step (for example, a curing step using heat) is performed. Will be executed.
  • the optical fiber core 1 is placed in a sealed container filled with hydrogen and left at room temperature under a pressure of about 2 OMPa for about 2 weeks.
  • the core 2 is written with the grating 21 by irradiating the second ultraviolet ray from outside the optical fiber core wire 1, that is, outside the coating layer 4. .
  • the writing of the grating 21 may be performed by using various known methods.
  • a lattice-shaped phase mask 5 is disposed immediately before the optical fiber core 1 as shown in FIG.
  • the Nd-YAG laser source 6 may irradiate, for example, a coherent ultraviolet laser beam having a fourth harmonic (4 ⁇ ) of 2666 nm, which is condensed by the cylindrical lens system 7.
  • the ultraviolet laser light passes through the phase mask 5 and the coating layer 4, the refractive index of the portion of the grating pitch corresponding to the grating pitch of the phase mask 5 with respect to the core 2 is increased, and the Bragg grating 21 is written. Will be.
  • reference numeral “8” is a beam expander that expands the ultraviolet laser beam into a parallel beam
  • reference numeral “9” is a portion where the power of the above-mentioned parallel laser beam is uniform.
  • the slit “10” is a movable reflecting mirror that can be moved in the longitudinal direction of the optical fiber core wire 1 (see the dashed line arrow), and the symbol “1 1” is light.
  • Spectrum analyzer, reference number “1 2” is optical isolator, reference number “1 3” is optical power blur.
  • the tension applying mechanism 30 shown in FIG. Is used to apply tension in the long axis direction to the optical fiber 1 to be written.
  • the specific method and effect of such tension application will be described later in detail with reference to the drawings.
  • an Nd—YAG laser source 6 (see Fig. 3) with a maximum average power of 100 mW, a pulse width of 50 ns, and a pulse frequency of 10 Hz can be used as an ultraviolet light source that can be used for grating writing.
  • Ultraviolet laser light of 266 nm, which is the fourth harmonic of this Nd-YAG laser, is irradiated onto the optical fiber core 1 on the coating layer 4 so that the irradiation energy density becomes, for example, 1.5 kJ / cm 2 .
  • the average power incident on the phase mask 5 is, for example, 10 mW
  • the dimension of the ultraviolet light applied to the optical fiber core 1 having an outer diameter of 200 m is about 2 mm (in the direction of the fiber axis). It is 2 mm (in the direction of the fiber).
  • phase mask 5 a mask having a grating pitch of, for example, 1065 nm and a length of 25 mm can be used. Then, by moving the movable mirror 10 smoothly and continuously in the fiber axial direction (longitudinal direction), a 24 mm long grating 25 can be written in the axial direction.
  • FIG. 4 shows the relationship between the applied tension at the time of writing the grating and the grating fabrication time.
  • FIG. 5 shows the relationship between the applied tension at the time of writing the grating and the grating forming speed.
  • the applied tension is represented by axial strain (%).
  • the fiber grating formation speed increases more rapidly when the tension is 0.8% or more than when no tension is applied, and the grating formation time is shortened.
  • the tension is 1.0% or more
  • the fiber grating forming speed increases 2 to 6 times compared to the case where the tension is 0.2% or less.
  • the tension exceeds 1.0%, the fiber grating formation speed is almost saturated.
  • the applied tension is preferably 0.8% or more, and more preferably 1.0% or more.
  • a preferable upper limit of the applied tension is 6%. If the tension exceeds 6%, the fiber may break mechanically.
  • the horizontal axis shows the tension applied to the fiber to be irradiated
  • the horizontal axis shows the final arrival reflectance during fabrication
  • the applied tension was set in four steps within an elongation ratio of about 1% to 3%. For all tensions, the reflectance after releasing the tension exceeds the ultimate reflectance at the time of fabrication.
  • the horizontal axis shows the applied tension
  • the vertical axis shows the increase (%) in reflectance due to release of the tension. It can be seen that the greater the applied tension during fabrication, the greater the increase in reflectance after releasing the tension. Irradiation on the coating using UV-transmitting resin can apply a maximum of about 6% tension to the fiber during fiber grating production, making it possible to significantly increase the reflectance after releasing the tension. . This, in combination with the above-mentioned sensitivity enhancement, makes it possible to efficiently produce a high-performance grating in a shorter time.
  • the tension applying mechanism 30 for applying a tension in the fiber axis direction to the optical fiber core 1 will be described below.
  • the tension applying mechanism 30 includes a frame 31 disposed so as to surround the ultraviolet irradiation region of the optical fiber core 1, and A pair of arm members 32, 33 protruding from the frame 31 on both sides of the optical fiber core 1 in the fiber axial direction, and a pair of arm members 32, 33 supported at the distal ends of the arm members 32, 33, respectively. It is provided with winding cylinders 34 and 35 as fixing means, and a motor 36 (see FIG. 9) for rotating and driving the winding cylinder 35 on one side in the axial direction of the fiber (the right side in FIG. 8).
  • the frame 31 has an opening 311 through which the ultraviolet laser light can pass at least at a side portion (upper portion in FIG. 8) of the optical fiber core 1, and the pair of arm members 32, 3 There is no restriction on the shape and the like as long as 3 can be maintained.
  • Each of the arm members 32 and 33 is formed in an L shape, and one end is fixed to the frame 31 and the other end is connected to the winding drums 34 and 35.
  • Each of the above winding cylinders 34, 35 is composed of a mandrel 341, 351, which constitutes a winding drum main body, and a pair of flanges 34, 32, 35 2 disposed on both sides thereof. ing.
  • the winding cylinder 35 on one side in the fiber axis direction (the right side in FIG.
  • the motor 36 is constituted by a pulse motor, and its output shaft is directly connected to the mandrel 351 or connected via a connecting member.
  • the motor 36 receives a control signal from a controller (not shown) and forcibly rotates the mandrel 351 by a set rotation amount.
  • a tension applying step In order to fabricate a fiber grating, a tension applying step, an irradiation step, a tension releasing step, and a screening step are sequentially performed. That is, in the tension applying step, first, the optical fiber core wires 1 on both sides of the writing area of the grating 21 are attached to the outer peripheral surfaces of the mandrels 341, 351 of the winding drums 34, 35 with respect to each other. Wrap it twice or three times (see Fig. 9) so that it does not overlap, and set the optical fiber core wire 1 in a state where it extends in a straight line.
  • the optical fiber core 1 is moved by the frictional resistance between the outer peripheral surface of the mandrel 341, 351 of each of the winding drums 34, 35 and the outer surface of the optical fiber core 1.
  • the mandrel is fixed so that it does not move relative to the outer peripheral surface of the mandrel 3 4 1, 3 5 1 in the fiber axis direction.
  • activate the mode 3 6 Forcibly rotate the drain 3 5 1 by the set amount of rotation to maintain this state.
  • the optical fiber core wire 1 between the pair of mandrels 341, 351 is forcibly extended in the fiber axial direction by a circumferential length corresponding to the forcible rotation amount of the mandrel 351.
  • the tension is applied, and the core 2 is in a state in which elastic strain (elongation strain) on the tensile side is generated. In this state, the next irradiation step is performed.
  • the phase mask 5 is set with respect to the writing area of the grating 21 of the optical fiber core 1, and one end to the other end of the phase mask 5 in the fiber axis direction.
  • Ultraviolet laser light from an ultraviolet irradiation system is applied to the optical fiber core 1 through the phase mask 5 over a range up to.
  • the change of the irradiation position of the ultraviolet laser light in the above-mentioned fiber axis direction range is performed by moving the reflection mirror 10 in the fiber axis direction.
  • the grating 21 having a grating pitch corresponding to the grating pitch of the phase grating 5 is written into the core 2 in a state where the above-described elongation distortion occurs due to the irradiation of the ultraviolet laser light.
  • a tension release step is performed. In this tension release step, the motor 36 is rotated in the reverse direction by the above-mentioned set rotation amount, and the optical fiber core is rotated. Line 1 is restored to its original state before the tension was applied, and there is no load.
  • the elongation strain generated in the core 2 is restored to its original state, that is, contracted, and the grating pitch of the written grating 21 is reduced in accordance with the contraction. Therefore, the wavelength characteristic of the grating 21 is shifted to the shorter wavelength side by the narrower grating pitch.
  • the reflectance of the grating is improved as compared to before the release of the tension.
  • the fabrication of the fiber grating is completed, but in the present embodiment, the screening step is performed subsequently.
  • this screening step a constant elongation strain is given to the fiber grating in the fiber axis direction for a predetermined time by operating the motor 36 of the tension applying mechanism 30 to screen for mechanical strength characteristics. Perform the test. Then, defective fiber gratings are eliminated from the product, and fiber gratings without defects are used as products. Fiber gratings that have passed the screening test will be combined with members supporting fiber gratings and other components to form optical communication components.
  • the relationship between the applied tension and the shift amount of the wavelength characteristic to the shorter wavelength side is determined in advance by a test, and based on this relationship, the relationship between the shift amount of the wavelength to be shifted and the wavelength is controlled.
  • the applied tension is set, and the set rotational speed of the motor 36 is determined so that the applied tension is generated in the optical fiber core 1.
  • irradiation of the ultraviolet laser light is performed as follows. You may do so.
  • the irradiation with the ultraviolet laser light is performed so that the irradiation energy density becomes about 1.5 kJ / cm 2 .
  • the ultraviolet laser light is irradiated from the outside of the coating layer 4, even if the coating layer 4 has a considerably thick film thickness of about 30 / m or more, the ultraviolet light is transmitted through the coating layer 4.
  • high-refractive-index modulation is generated on the core 2 to enable writing of the high-reflection Bragg grating 21.
  • the optical fiber to be written ⁇ the core 1 is positioned at a specific position with respect to the beam pattern BP of the ultraviolet laser light focused by the cylindrical lens system 7, and in this state, the ultraviolet laser Irradiation of light is performed.
  • the beam pattern BP is obtained by converging the parallel beam incident on the cylindrical lens system 7 so as to be directed to the focal point F.
  • the entirety of the optical fiber core 1 is the beam pattern BP.
  • the optical fiber 1 is positioned so that the outer peripheral surface of the coating layer 4 of the optical fiber 1 is inscribed in the outer edge of the beam pattern BP.
  • the optical fiber core 1 is located in front of the focal point F as shown by a solid line in FIG. 10 as indicated by a dashed line in FIG. It does not matter if it is behind the focus F.
  • the focal length L1 is 100 mm
  • the optical fiber core wire 1 with an outer diameter of 200 m is placed on the optical axis at a distance L2 of approximately 2 mm from the focal point F. Just set it.
  • the entire coating layer 4 can be irradiated with ultraviolet laser light at a uniform irradiation energy density. And be able to.
  • the application of the tension by the tension applying mechanism is performed by rotatably supporting one of the winding drums 35 with respect to the arm member 33 and forcibly rotating the winding drum 35 with the motor 36.
  • the present invention is not limited to this, and both winding cylinders 34 and 35 are fixed to the arm members 32 and 33 so as not to rotate together, and one end 33 of one arm member 33 is fixed. 8 is guided and supported movably in the fiber axis direction with respect to the frame 31 as shown by a dashed line in FIG.
  • this arm member 33 is combined with a transmission mechanism such as a rack and a binion and a motor, or
  • the tension may be applied to the optical fiber core 1 by configuring the apparatus such that the hydraulic cylinder or the like is forcibly moved to the right in FIG.
  • the method for manufacturing a fiber grating of the present embodiment is suitably applied to the manufacture of both a short-period grating and a long-period grating.
  • the short-period grating has a pitch of about 1 m or less
  • the long-period grating is a grating having a pitch of about several hundred m.
  • a method of manufacturing a fiber grating that can be suitably used for a temperature sensor and an embodiment of a temperature sensor using such a fiber grating will be described.
  • a coating layer hereinafter referred to as a “coated fiber grating”.
  • the coating layer of the coated fiber grating uniformly compresses the fiber at low temperatures.
  • the reflection peak wavelength of the grating formed on the fiber strand is Shifts under the influence of compression force.
  • the compressive force of the coating layer is mainly determined by the coefficient of thermal expansion and elastic modulus of the fiber strand, and the elastic modulus, coefficient of thermal expansion and thickness of the coating layer. Therefore, by appropriately selecting the material of the coating layer and forming the coating layer of an appropriate thickness, the rate of change of the reflection peak wavelength of the fiber grating with respect to temperature change (hereinafter simply referred to as the “temperature coefficient of the reflection peak wavelength”) ) May be set to a predetermined value.
  • the coating layer uniformly compresses the fiber in the low temperature region, non-uniform stress is not applied to the fiber unlike the package structure, so that the coating has stable mechanical strength even at a low temperature. Also, unlike a packaged sensor, it is small and can be bent, so it can be placed in various locations.
  • the temperature coefficient of the reflection peak wavelength of the grating is kept constant over a wide temperature range (particularly from a temperature above room temperature to a very low temperature). be able to.
  • a wide temperature range can be easily measured.
  • the change in the temperature coefficient of the reflection peak wavelength of the grating caused by the stress caused by the coating layer offsets the change caused by other factors such as external distortion of the temperature coefficient of the reflection beak wavelength of the fiber grating.
  • a layer can be formed, and a temperature sensor that can easily measure the temperature can be obtained.
  • a constant temperature coefficient is shown in each of a plurality of temperature ranges.
  • the respective temperature coefficients may be different. That is, if the temperature dependence of the reflection peak wavelength can be approximated by a plurality of continuous straight lines, a temperature sensor that can easily measure the temperature in each temperature range that can be approximated by a straight line can be obtained. It is preferable that the temperature range of each is wide, but it may be set appropriately in consideration of the temperature range of the object to be measured and the required measurement accuracy.
  • the fiber grating of the present embodiment is formed by using the optical fiber 1 in which the surface of the optical fiber 1 ′ having the core 2 and the clad 3 is covered with the coating layer 4.
  • the dope of Sn, or 3] 1 and 81, or Sn, A 1 and B is used. It is preferable to use a material to which the light is added in order to constantly increase the photoinduced refractive index change.
  • the coating layer 4 is formed by a single coating following the step of drawing the optical fiber 1 '.
  • the material for forming the coating layer 4 and the thickness of the coating layer 4 are selected and the thickness is determined so that the temperature coefficient of the reflection peak wavelength of the grating becomes a predetermined value.
  • the coating layer 4 having a large coefficient of thermal expansion the temperature coefficient of the reflection peak wavelength of the grating can be increased, and conversely, by using the coating layer 4 having a small coefficient of thermal expansion, the reflection peak of the grating can be increased.
  • the temperature coefficient of the wavelength can be reduced.
  • the degree of contribution of the reflection peak wavelength by the coating layer 4 to the temperature coefficient can be changed.
  • This coating layer design process includes the elastic modulus (Young's modulus E), thermal expansion coefficient (linear thermal expansion coefficient), temperature coefficient of refractive index (thermo-optic coefficient), and material of the coating layer of the optical fiber 1 '.
  • the thickness of the coating layer is determined.
  • the fiber grating is designed so that the temperature coefficient of the reflection peak wavelength is constant from a temperature above room temperature (for example, 1 10 ° C) to a very low temperature (for example, -196 ° C).
  • As a material for forming the coating layer 4 it is preferable to use an ultraviolet ray transmitting type ultraviolet curable resin as in the first embodiment.
  • the writing process of the grating is performed while applying tension (or strain) to the fiber core 1 using the fiber grating manufacturing apparatus shown in FIG. 3 to reduce the shift amount of the reflection peak wavelength of the grating. Can be controlled. It should be noted that the writing itself of the grating 21 by ultraviolet irradiation may be performed by using various well-known methods, and FIG. 3 shows an example in which the writing is performed by, for example, a phase mask method.
  • Fiber 1 as,, and G e and S n using a co-doped quartz glass-based fiber (diameter: 1 2 5 zm, thermal expansion coefficient:. 0 5 5 X 1 0- 6 ( room temperature) Zd eg , Modulus: 73 GPa (room temperature)).
  • the relative refractive index difference ( ⁇ ) of this fiber was 0.97%, the cut-off wavelength (person c) was 1.27 ⁇ m, and the Sn concentration was 15,000 ppm.
  • the surface of the fiber strand 1 ′ was coated with a UV-transmissive UV-curable resin having a high transmittance to ultraviolet rays for the writing of a grating to form a coating layer 4.
  • an aliphatic urethane acrylate having a transmittance of about 10% or more for ultraviolet rays having a wavelength of about 240 nm to about 270 nm (photopolymerization initiator: 2,4,6,1-trimethylbenzoyldiphne)
  • a coating layer 4 single layer: thickness of about 75 ⁇ m on both sides
  • a thickness of about 37.5 ⁇ m using enylphosphine oxide 200 m.
  • the thermal expansion coefficient of the coating layer 4 is 1 ⁇ 10 " 4 / deg, and the elastic modulus is 54 OMPa (normal temperature).
  • the coated fiber core 1 was left in a high-pressure hydrogen gas of about 2 OMPa for about 2 weeks, and was filled with hydrogen.Grating was written on the coated fiber core using the phase mask method. The writing of the grating was performed using the fiber grating manufacturing apparatus shown in Fig. 3. No tension was applied to the fiber core 1 (concrete example 1), and the tension was applied in the axial direction of the fiber core 1 ( While applying 3.9 N) (Specific Example 2), a fourth harmonic (266 nm, intensity 10 mW) of the Nd-YAG laser was swept and irradiated (about 22 mm). The laser irradiation time was adjusted so that the levels were the same.
  • Example 1 and Example 2 produced by the above method
  • the fiber gratings from which the coating layer was removed were referred to as Comparative Examples 1 and 2, respectively.
  • FIG. 11 shows the results of measuring the temperature dependence of the reflection peak wavelengths of the fiber gratings of Examples 1 and 2 and Comparative Examples 1 and 2.
  • the reflection peak wavelength of the fiber grating of Example 1 changes almost linearly from about -70 ° C to about 170 ° C, and its slope (temperature coefficient: ⁇ / ⁇ ) Was 0.012 nm / ° C. Further, this temperature coefficient was the same as the temperature coefficient of the reflection beak wavelength of Comparative Example 1 at ⁇ 20 ° C. to + 60 ° C. Furthermore, the temperature dependence from the room temperature of Example 1 (here, 20 ° C) to -196 ° C The property was well approximated by a straight line, and the temperature coefficient was 0.013 nm / ° C. Note that here, the force at room temperature of 20 ° C is not limited to this, but “room temperature” refers to the ambient temperature of the fiber (the temperature of the area other than the temperature measurement target, the temperature of the working environment).
  • the temperature coefficient of the reflected peak wavelength from -70 ° C to 1-96 ° C (liquid nitrogen temperature) in Specific Examples 1 and 2 can be approximated by a straight line. 0.013 nm / ° C, which is a value close to the temperature coefficient on the high temperature side (0.012 nm / ° C).
  • the temperature coefficient on the low temperature side can be increased, so that a single temperature coefficient can be obtained over a wide temperature range (for example, -196 ° C to 10170 ° C).
  • ⁇ / ⁇ 0.012 nm / ° C
  • a fiber grating with a temperature dependence of the reflection peak wavelength that can be approximated well can be obtained.
  • the temperature coefficient (0.005 nm / ° C) of the reflection peak wavelength on the low temperature side (approximately ⁇ 75 ° C or less) of Comparative Example 1 is the temperature coefficient (0.012 nm / ° C), indicating a different temperature dependence from the high temperature side.
  • a decrease in the temperature coefficient on the low temperature side is also observed in Comparative Example 2. This phenomenon is thought to be due to the fact that the temperature change of the refractive index of the core forming the grating becomes smaller on the low temperature side.
  • the reflection at the low temperature side is controlled by controlling the magnitude of the compressive stress applied to the fiber by the coating layer, which increases as the temperature decreases.
  • the temperature coefficient of the peak wavelength is adjusted.
  • the adjustment of the temperature coefficient on the low temperature side is not performed so as to match the temperature coefficient on the high temperature side, but may be adjusted so as to increase the temperature coefficient depending on the application.
  • a large temperature coefficient means high temperature measurement sensitivity, so if accurate measurement of cryogenic temperatures (for example, less than 10 oC) is required, May be designed so as to increase the temperature coefficient of the coating layer.
  • the temperature coefficient in a temperature range of ⁇ 100 ° C. or less is preferably larger than 0.01 nm / ° C.
  • the temperature dependence of the reflection peak wavelength be expressed by a single temperature coefficient (it can be approximated by a straight line), because the temperature can be easily obtained from the measured wavelength. Even if it cannot be expressed by a single temperature coefficient, for example, if a graph as shown in Fig. 11, that is, a calibration curve is created in advance, and the temperature is determined from the measured reflection peak wavelength of the fiber grating and the calibration curve, Good.
  • FIG. 12 schematically shows an embodiment of a temperature sensor 50 using a fiber grating according to the present embodiment.
  • the temperature sensor 50 receives the reflected light from the optical fiber 1 on which the grating 21 is formed, the light source 52 for emitting light to the optical fiber 1, and the grating 21 and detects the wavelength of the reflected light.
  • An optical spectrum analyzer 58 is provided. If necessary, an optical isolator 54 may be provided to select light having a specific wavelength from the light emitted from the light source 52. Further, an optical coupler 56 is provided to couple an optical path for transmitting light from the light source 52 to the grating 21 and an optical path for guiding the light reflected from the grating 21 to the optical spectrum analyzer 58. You may.
  • the fino 1 on which the gratings 21a and 21b are formed is arranged, for example, in a tank 60 filled with liquefied methane gas (1183 ° C).
  • the gratings 21a and 21b are formed using the above-described tension application method, and have mutually different reflection peak wavelengths. Therefore, by detecting the reflection peak wavelength, it is possible to determine which of the gratings 21a and 21b is the reflected light. Therefore, by using one fiber having a plurality of gratings, it is possible to easily measure temperatures at different positions. Of course, it is not necessary to provide a plurality of gratings.
  • the temperature sensor of the present embodiment does not have a package structure for fixing the fiber, it can be easily installed on a curved surface, a narrow place, or the like.
  • the coated fiber has high mechanical strength and does not break, especially at low temperatures. Therefore, the temperature sensor of the present embodiment is suitably used as a temperature sensor for measuring the temperature of a curved surface at a low temperature like the above-mentioned liquefied natural gas tank.
  • the core when the grating is written, the core is distorted in the axial direction, thereby increasing the photosensitivity to ultraviolet light.
  • the rate of change of the refractive index due to irradiation increases. Therefore, the time required for the writing operation can be reduced.
  • the increase in the refractive index is promoted. If the fiber grating is used with a tension smaller than the above applied tension, the reflectance will be higher than the reflectance when the grating is manufactured. High reflectivity can be realized.
  • the temperature coefficient of the reflection peak wavelength of the grating formed on the coated fiber can be adjusted to a desired value. Therefore, a package structure is not required, and a simple structure is realized.
  • a fiber grating that can be suitably used for a temperature sensor capable of measuring a temperature down to a low temperature can be manufactured.
  • manufacturing fiber gratings used in temperature sensors that can measure low temperatures with high sensitivity and temperature sensors that can easily measure a wide temperature range from high to extremely low temperatures. Can be.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)

Abstract

L'invention concerne un procédé de fabrication d'un réseau de fibres par l'augmentation de la photosensibilité du verre et par la gravure d'un réseau. La surface extérieure d'une fibre optique est recouverte d'une couche de revêtement constituée de résine laissant passer le rayonnement ultraviolet. Le rayonnement ultraviolet est appliqué sur le noyau dans lequel la distorsion dans le sens axial est de l'ordre de +0,8 % à +6 % pour la gravure du réseau. Ainsi, la vitesse de formation d'un réseau est accrue ainsi que la réflectance de ce dernier après la disparition de la tension. Un procédé de fabrication d'un réseau de fibres de préférence utilisées pour un capteur de température de structure simple et conçu pour mesurer la température jusqu'à la température cryogénique et un capteur de température sont décrits. Avant l'étape de formation de la couche de revêtement de la fibre optique, le matériau de la résine et l'épaisseur de la couche de revêtement sont déterminés, de manière que la vitesse de changement (coefficient de température) de la longueur d'onde crête de réflexion du réseau à produire avec la température puisse être une valeur prédéterminée.
PCT/JP2000/004219 1999-06-29 2000-06-27 Procede de fabrication de reseau de fibres, composant pour communication optique et capteur de temperature WO2001001174A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP11183612A JP2001013333A (ja) 1999-06-29 1999-06-29 ファイバグレーティングの製造方法および光通信用コンポーネント
JP11/183612 1999-06-29
JP11220826A JP2001042142A (ja) 1999-08-04 1999-08-04 ファイバグレーティングの作製方法およびファイバグレーティングを用いた温度センサ
JP11/220826 1999-08-04

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Publication number Priority date Publication date Assignee Title
CN102169028A (zh) * 2011-01-20 2011-08-31 中国电力科学研究院 晶闸管壳内温度实时测量系统
RU2695286C1 (ru) * 2018-12-17 2019-07-22 Федеральное государственное автономное образовательное учреждение высшего образования "Новосибирский национальный исследовательский государственный университет" (Новосибирский государственный университет, НГУ) Устройство для создания периодических структур показателя преломления внутри прозрачных материалов

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WO1991010151A1 (fr) * 1989-12-26 1991-07-11 United Technologies Corporation Dispositif pour guide d'ondes optique a compensation thermique, a filtre de bragg incorpore
WO1992008999A1 (fr) * 1990-11-08 1992-05-29 British Telecommunications Public Limited Company Procede de formation de reseaux de fibres optiques
EP0650083A2 (fr) * 1993-10-22 1995-04-26 AT&T Corp. Empaquetage pour fibre optique
JPH08286040A (ja) * 1995-04-17 1996-11-01 Sumitomo Electric Ind Ltd 光ファイバ型回折格子
JPH08286056A (ja) * 1995-04-18 1996-11-01 Sumitomo Electric Ind Ltd ファイバグレーティングの製造方法及び製造装置
WO1997014983A1 (fr) * 1995-10-16 1997-04-24 Sumitomo Electric Industries, Ltd. Reseau de diffraction a fibre optique, procede de fabrication et source lumineuse laser
JPH1082919A (ja) * 1996-07-15 1998-03-31 Sumitomo Electric Ind Ltd ファイバグレーティングの作成方法及び光ファイバ
WO1999027399A1 (fr) * 1997-11-26 1999-06-03 Mitsubishi Cable Industries, Ltd. Reseau de fibres, son procede et son dispositif de fabrication
WO2000000858A1 (fr) * 1998-06-26 2000-01-06 The Furukawa Electric Co., Ltd. Procede pour former un reseau de fibres et reseau de fibres forme selon ce procede

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WO1992008999A1 (fr) * 1990-11-08 1992-05-29 British Telecommunications Public Limited Company Procede de formation de reseaux de fibres optiques
EP0650083A2 (fr) * 1993-10-22 1995-04-26 AT&T Corp. Empaquetage pour fibre optique
JPH08286040A (ja) * 1995-04-17 1996-11-01 Sumitomo Electric Ind Ltd 光ファイバ型回折格子
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WO1997014983A1 (fr) * 1995-10-16 1997-04-24 Sumitomo Electric Industries, Ltd. Reseau de diffraction a fibre optique, procede de fabrication et source lumineuse laser
JPH1082919A (ja) * 1996-07-15 1998-03-31 Sumitomo Electric Ind Ltd ファイバグレーティングの作成方法及び光ファイバ
WO1999027399A1 (fr) * 1997-11-26 1999-06-03 Mitsubishi Cable Industries, Ltd. Reseau de fibres, son procede et son dispositif de fabrication
WO2000000858A1 (fr) * 1998-06-26 2000-01-06 The Furukawa Electric Co., Ltd. Procede pour former un reseau de fibres et reseau de fibres forme selon ce procede

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102169028A (zh) * 2011-01-20 2011-08-31 中国电力科学研究院 晶闸管壳内温度实时测量系统
RU2695286C1 (ru) * 2018-12-17 2019-07-22 Федеральное государственное автономное образовательное учреждение высшего образования "Новосибирский национальный исследовательский государственный университет" (Новосибирский государственный университет, НГУ) Устройство для создания периодических структур показателя преломления внутри прозрачных материалов

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