JP2007170918A - Optical waveguide device, temperature measuring instrument, and temperature measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide device that is suitably used in measuring temperature with high accuracy. <P>SOLUTION: This optical waveguide device 10 comprises optical wave guides 111 to 114 formed on a substrate 100. The waveguides 111 and 112 are optically coupled to each other by means of optical couplers 121 and 122, respectively, to form a first Mach-Zehnder interferometer, while the waveguides 113 and 114 are optically coupled to each other by means of optical couplers 123 and 124, respectively, to form a second Mach-Zehnder interferometer. The temperature dependence of the refraction index of a core in a partial zone 112B of the waveguide 112 is different from those of other optical waveguide portions 112A and 112C of the waveguides 111 and 112. The temperature dependence of the refraction index of a core in a partial zone 114B of the waveguide 114 is different from those of other optical wave guide portions 114A and 114C of the waveguides 113 and 114. The length of the zone 112B and the length of the zone 114B are different from each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus and method for measuring temperature, and an optical waveguide device used for temperature measurement.

As a temperature measurement technique using an optical waveguide such as an optical fiber, for example, those disclosed in Patent Documents 1 and 2 are known. The technique disclosed in Patent Document 1 allows light to be incident on one end of an optical fiber that has been subjected to non-reflective treatment at the terminal portion, and detects the optical power of a specific wavelength among the backscattered light generated in the optical fiber. The temperature distribution of the longitudinal method in the optical fiber is measured. In addition, the technique disclosed in Patent Document 2 guides the radiated light from the measurement target through an optical fiber, detects the optical power in each of two different wavelength bands of the guided radiated light, The temperature of the measurement object is measured based on these two optical powers.
Japanese Patent No. 2724246 Japanese Patent No. 3325700

  All of the temperature measurement techniques described in these documents can measure the temperature in a relatively wide temperature range, but the accuracy is poor. The present invention has been made to solve the above-described problems, and is a temperature measurement device and a temperature measurement method capable of measuring temperature with high accuracy, and an optical beam that can be suitably used in these devices or methods. An object is to provide a waveguide device.

In an optical waveguide device according to the present invention, a first optical waveguide, a second optical waveguide, a third optical waveguide, and a fourth optical waveguide are formed on a substrate, and the first optical waveguide and the second optical waveguide are the first light. Each of the coupler and the second optical coupler is optically coupled to form a first Mach-Zehnder interferometer, and a part of the second optical waveguide (length L ₂ ) between the first optical coupler and the second optical coupler. The temperature dependency of the refractive index of the core is different from that of other optical waveguide portions, and the third optical waveguide and the fourth optical waveguide are optically coupled in the third optical coupler and the fourth optical coupler, respectively. And the temperature dependence of the refractive index of the core in a part of the fourth optical waveguide (length L ₄ , where L ₂ ≠ L ₄ ) is different between the third optical coupler and the fourth optical coupler. It is different from the optical waveguide part.

In the optical waveguide device according to the present invention, when light is incident on one end of one of the first optical waveguide and the second optical waveguide, each of the first optical waveguide and the second optical waveguide passes through the first Mach-Zehnder interferometer. Although light is emitted from the end, the temperature dependency of the refractive index of the core in a partial section of the second optical waveguide is different from that of other optical waveguide portions, and each light transmission characteristic at that time varies depending on the temperature. . Similarly, when light enters one end of either the third optical waveguide or the fourth optical waveguide, light is emitted from the other end of each of the third optical waveguide and the fourth optical waveguide via the second Mach-Zehnder interferometer. However, since the temperature dependency of the refractive index of the core in a partial section of the fourth optical waveguide is different from that of the other optical waveguide portions, each light transmission characteristic at that time also changes depending on the temperature. Further, since the length of some sections of the second optical waveguide L ₂ and the fourth portion of the length L ₄ of the section of the optical waveguide different from each other, the light transmission in each of the first Mach-Zehnder interferometer and a second Mach-Zehnder interferometer The characteristics are different from each other. By utilizing such characteristics of the optical waveguide device, the temperature can be measured with high accuracy.

  In the optical waveguide device according to the present invention, it is preferable that the cores of the partial section of the second optical waveguide and the partial section of the fourth optical waveguide are made of liquid. In each of the partial section of the second optical waveguide and the partial section of the fourth optical waveguide, at least two injection holes for injecting liquid into the core portion are provided from the core to the upper surface through the over clad. It is suitable. In addition, it is preferable that a liquid pool is provided around the opening of each injection hole on the overcladding in each of the partial section of the second optical waveguide and the partial section of the fourth optical waveguide.

  The temperature measuring device according to the present invention includes (1) the optical waveguide device according to the present invention, (2) a light source unit that outputs light, and (3) light output from the light source unit. And the light output from the light source unit is incident on one end of either the third optical waveguide or the fourth optical waveguide of the optical waveguide device. An incident optical system for incident light; and (4) a detector for detecting the power of light emitted from the other end of each of the first optical waveguide, the second optical waveguide, the third optical waveguide, and the fourth optical waveguide of the optical waveguide device. And (5) an output optical system for guiding light from the other end of each of the first optical waveguide, the second optical waveguide, the third optical waveguide, and the fourth optical waveguide of the optical waveguide device to the detection unit, and (6) the detection unit Of temperature of optical waveguide device based on detection results Characterized in that it comprises a and. In addition, it is preferable that each of the incident optical system and the output optical system includes an optical fiber that inputs and outputs light with respect to the optical waveguide device.

The temperature measurement method according to the present invention includes (1) using the optical waveguide device according to the present invention, and (2) making light incident on one end of either the first optical waveguide or the second optical waveguide, It detects the power P ₁ of the light emitted from the other end of the first optical waveguide via the first Mach-Zehnder interferometer, the power P ₂ of the light emitted from the other end of the second optical waveguide via the first Mach-Zehnder interferometer (3) The light power P ₃ emitted from the other end of the third optical waveguide through the second Mach-Zehnder interferometer after light is incident on one end of either the third optical waveguide or the fourth optical waveguide. And the power P ₄ of light emitted from the other end of the fourth optical waveguide through the second Mach-Zehnder interferometer is detected. (4) Based on these four optical powers P _{1 to} P ₄ , the optical waveguide type Measure device temperature In addition, it is preferable to use an optical fiber to input / output light to / from the optical waveguide device.

  According to the present invention, the temperature can be measured with high accuracy.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a configuration diagram of a temperature measuring apparatus 1 according to the present embodiment. The temperature measuring apparatus 1 shown in this figure includes an optical waveguide device 10, a light source unit 20, a detection unit 30, an analysis unit 40, incident optical fibers 51 and 53, and outgoing optical fibers 61 to 64.

  In the optical waveguide device 10, a first optical waveguide 111, a second optical waveguide 112, a third optical waveguide 113, and a fourth optical waveguide 114 are formed on a substrate 100. The first optical waveguide 111 and the second optical waveguide 112 form a first optical coupler 121 and a second optical coupler 122 at an interval where they can be optically coupled to each other at two locations in the middle of each optical path. That is, the first optical waveguide 111 and the second optical waveguide 112 are optically coupled in the first optical coupler 121 and the second optical coupler 122, respectively, and constitute a first Mach-Zehnder interferometer. The third optical waveguide 113 and the fourth optical waveguide 114 are spaced apart from each other at two locations along the optical path to form the third optical coupler 123 and the fourth optical coupler 124. Yes. That is, the third optical waveguide 113 and the fourth optical waveguide 114 are optically coupled in the third optical coupler 123 and the fourth optical coupler 124, respectively, and constitute a second Mach-Zehnder interferometer.

  The light source unit 20 outputs light to be incident on one end (incident end) of each of the first optical waveguide 111 and the third optical waveguide 113 of the optical waveguide device 10. The optical fiber 51 enters the light output from the light source unit 20 at one end, guides the light incident on the one end to the other end, emits the light from the other end, and outputs the first light of the optical waveguide device 10. The light is incident on the incident end of the waveguide 111. Further, the optical fiber 53 enters the light output from the light source unit 20 at one end, guides the light incident on the one end to the other end, emits the light from the other end, and outputs the light from the optical waveguide device 10. The light is incident on the incident end of the three optical waveguides 113.

  The detection unit 30 calculates the power of light emitted from the other end (outgoing end) of each of the first optical waveguide 111, the second optical waveguide 112, the third optical waveguide 113, and the fourth optical waveguide 114 of the optical waveguide device 10. To detect. The optical fiber 61 enters light emitted from the emission end of the first optical waveguide 111 of the optical waveguide device 10 at one end, guides light incident on the one end to the other end, and emits light from the other end. Then, the light is incident on the light receiving element of the detection unit 30. The optical fiber 62 enters light emitted from the emission end of the second optical waveguide 112 of the optical waveguide device 10 at one end, guides light incident on the one end to the other end, and emits light from the other end. Then, the light is incident on the light receiving element of the detection unit 30. The optical fiber 63 enters light emitted from the emission end of the third optical waveguide 113 of the optical waveguide device 10 at one end, guides light incident on the one end to the other end, and emits light from the other end. Then, the light is incident on the light receiving element of the detection unit 30. Further, the optical fiber 64 enters light emitted from the emission end of the fourth optical waveguide 114 of the optical waveguide device 10 at one end, guides the light incident on the one end to the other end, and transmits light from the other end. Is incident on the light receiving element of the detection unit 30.

The analysis unit 40 emits light P _{1 in} from the light source unit 20 and enters the incident end of the first optical waveguide 111 of the optical waveguide device 10, and the optical waveguide device 10 emitted from the light source unit 20. The power P3 _{, in} of the light incident on the incident end of the third optical waveguide 113 is input. The analysis unit 40 also outputs the power P _{1, out} of the light emitted from the emission end of the first optical waveguide 111 of the optical waveguide device 10 and detected by the detection unit 30, and the second optical waveguide 112 of the optical waveguide device 10. The light power P _{2, out} emitted from the light emitting end of the optical waveguide device 10 and detected by the detecting unit 30, and the light power P ₃ emitted from the light emitting end of the third optical waveguide 113 of the optical waveguide device 10 and detected by the detecting unit 30 _{, out} , and the power P _{4, out} of light emitted from the emission end of the fourth optical waveguide 114 of the optical waveguide device 10 and detected by the detection unit 30 are input.

Further, the analyzing unit 40 transmits light loss α ₁ from the incident end of the first optical waveguide 111 to the output end of the first optical waveguide 111 based on the input optical power P _{1, in} and the output optical power P _{1, out.} And a transmission loss α ₂ of light from the incident end of the first optical waveguide 111 to the output end of the second optical waveguide 112 based on the input optical power P _{1, in} and the output optical power P _{2, out} , Based on the optical power P _{3, in} and the output optical power P _{3, out} , the transmission loss α ₃ of light from the incident end of the third optical waveguide 113 to the output end of the third optical waveguide 113 is obtained, and the input optical power Based on P _{3, in} and output light power P _{4, out} , a transmission loss α ₄ of light from the incident end of the third optical waveguide 113 to the output end of the fourth optical waveguide 114 is obtained. And the analysis part 40 calculates | requires the temperature of the optical waveguide device 10 based on said transmission loss (alpha) _{1- (} alpha) ₄ .

  For the optical fibers 51, 52, 61 to 64, for example, an 8-core optical fiber ribbon can be used. When such a tape fiber is used, even if the loss of each optical fiber fluctuates due to local bending of each optical fiber, almost the same fluctuation is applied to the six optical fibers.

  FIG. 2 is a plan view of the optical waveguide device 10 according to the present embodiment. In the optical waveguide device 10, a first optical waveguide 111, a second optical waveguide 112, a third optical waveguide 113, and a fourth optical waveguide 114 are formed on a substrate 100, and the first optical waveguide 111 and the second optical waveguide are formed. 112 is optically coupled in each of the first optical coupler 121 and the second optical coupler 122 to form a first Mach-Zehnder interferometer, and the third optical waveguide 113 and the fourth optical waveguide 114 are the third optical coupler. 123 and the fourth optical coupler 124 are optically coupled to constitute a second Mach-Zehnder interferometer.

Further, in the first Mach-Zehnder interferometer, the temperature dependence of the refractive index of the core of the partial section 112B of the second optical waveguide 112 between the first optical coupler 121 and the second optical coupler 122 is the first optical waveguide 111. The other optical waveguide portions 112A and 112C are different from the second optical waveguide 112. In addition, the temperature dependence of the refractive index of the core of the partial section 114B of the fourth optical waveguide 114 between the third optical coupler 123 and the fourth optical coupler 124 in the second Mach-Zehnder interferometer is the third optical waveguide 113. And different from the other optical waveguide portions 114A and 114C of the fourth optical waveguide 114. Further, the length _{L 2} of a partial section 112B of the second optical waveguide 112, the length _{L 4} of a partial section 114B of the fourth optical waveguide 114 differ from each other _{(L 2} ≠ _L 4).

Such an optical waveguide device 10 is preferably composed of quartz glass as a main component for the portions excluding the partial section 112B of the second optical waveguide 112 and the partial section 114B of the fourth optical waveguide 114. A core with a refractive index increasing material (for example, GeO ₂ ) added thereto. On the other hand, the cores of the partial section 112B of the second optical waveguide 112 and the partial section 114B of the fourth optical waveguide 114 are preferably made of liquid.

  FIG. 3 is a cross-sectional view of optical waveguides at various points in the optical waveguide device 10 according to the present embodiment. FIG. 5A is a cross-sectional view of the optical waveguides (first optical waveguide 111 as a representative example) at portions other than the partial section 112B of the second optical waveguide 112 and the partial section 114B of the fourth optical waveguide 114. As shown in this figure, a core having a rectangular cross section is formed on a substrate 100, and an over clad 130 is formed thereon, thereby forming an optical waveguide. Each of these regions is mainly composed of quartz glass.

  FIG. 6B shows the portions of the second optical waveguide 112 except for the vicinity of both ends in the partial section 112B of the second optical waveguide 112 or the partial section 114B of the fourth optical waveguide 114 (partial section 112B of the second optical waveguide 112 as a representative example). Sectional drawing (AA 'cross section in FIG. 2) is shown. As shown in this figure, a core having a rectangular cross section is provided on a substrate 100, and an overclad 130 is formed thereon, and a partial section 112B of the second optical waveguide 112 and the fourth optical waveguide 114 are formed. Each partial section 114B is configured. The substrate 100 and the overclad 130 are mainly composed of quartz glass. On the other hand, the region where the core is to be provided is a cavity, and liquid is injected into the cavity to form the core.

  FIG. 6C shows an end of the partial section 112B of the second optical waveguide 112 or the partial section 114B of the fourth optical waveguide 114 (as an example, the end of the partial section 112B of the second optical waveguide 112). Sectional drawing (BB 'cross section in FIG. 2) is shown. As shown in this figure, at both end portions of the partial section 112B of the second optical waveguide 112, an injection hole 112D for injecting liquid into the core portion passes through the overcladding 130 from the core and is the top surface. Is provided. A liquid reservoir 140 is provided around the opening of each injection hole 112D on the over clad 130. The same applies to both end portions of the partial section 114B of the fourth optical waveguide 114. FIG. 4D is a modification of FIG. In the cross section shown in this figure, the liquid portion in the partial section 112 </ b> B of the second optical waveguide 112 is a part of the core cross section of the second optical waveguide 112.

  Next, an example of a method for manufacturing the optical waveguide device 10 will be described. FIG. 4 is a process diagram illustrating a method for manufacturing the optical waveguide device 10 according to the present embodiment. This drawing particularly shows the manufacturing method for the first optical waveguide 111 and the second optical waveguide 112.

  First, a substrate 100 made of quartz glass is prepared, and a Ge-added quartz glass film 110 having a predetermined thickness to serve as a core is deposited on the substrate 100 by a method such as plasma CVD, FHD, or sputtering ((a) in the figure). ). The Ge-added quartz glass film 110 is processed to have a predetermined width and a predetermined height by the first photolithography and reactive ion etching ((b) in the figure). A first overcladding 131 having a predetermined thickness is further deposited thereon by plasma CVD or FHD (FIG. 4C).

  Further, by a second photolithography and reactive ion etching, a groove 115 having a predetermined width and a predetermined depth is dug in a portion to be a partial section 112B of the second optical waveguide 112 (FIG. 4D). A second over clad 132 having a predetermined thickness is deposited thereon by plasma CVD, and the upper part of the groove is closed to form a cavity 116 (FIG. 4E). The first overclad 131 and the second overclad 132 become the above-described overclad 130.

  A liquid inlet / outlet 117 having a predetermined diameter and penetrating to the cavity 116 is formed by the third photolithography and reactive ion etching (FIG. 4F). A film 140 is affixed around the opening of the liquid inlet / outlet hole 117 on the upper surface of the over clad 132, and holes are made with needles at portions corresponding to both ends of the cavity 116 to penetrate the film 140, thereby forming a liquid reservoir having a predetermined diameter ( FIG. 4 (g)). The liquid reservoir in the final process can also be formed by processing the overclad glass by photolithography and reactive ion etching. The liquid is poured from one side of the liquid inlet / outlet around the liquid inlet / outlet, and the liquid reaches the other end of the liquid inlet / outlet.

  Next, an example of a specific configuration and operation of the temperature measurement apparatus 1 and the optical waveguide device 10 according to the present embodiment will be described. Each of the substrate 100 and the overclad 130 is made of quartz glass. Each of the first optical waveguide 111 and the third optical waveguide 113 is made of quartz glass to which Ge is added. As for the second optical waveguide 112, a part section 112B is made of index matching oil, and the other section is made of Ge-added quartz glass. As for the fourth optical waveguide 114, a partial section 114B is made of index matching oil, and the other section is made of Ge-added quartz glass.

The refractive index of pure quartz glass is 1.444. The refractive index of the Ge-added quartz glass core is 1.447. The index matching oil has a refractive index of 1.45. These refractive indexes are all values at a temperature of 25 ° C. and a wavelength of 1.55 μm. The temperature dependence of the refractive index of each of the Ge-added quartz glass and quartz glass is 8 × 10 ⁻⁶ ° C. The temperature dependence of the index matching oil refractive index is -0.0002 / ° C.

The cross-sectional shape of the core of each of the optical waveguides 111 to 114 is a square of 7.5 μm × 7.5 μm. The minimum curvature radius of each curved portion of the optical waveguides 111 to 114 is 2.5 mm. Each of the optical couplers 121 to 124 has a branching ratio of 1: 1 at a wavelength of 1.55 μm. The lengths of the straight portions of the first optical waveguide 111 and the second optical waveguide 112 between the first optical coupler 121 and the second optical coupler 122 are 5 mm. The lengths of the straight portions of the third optical waveguide 113 and the fourth optical waveguide 114 between the third optical coupler 123 and the fourth optical coupler 124 are 5 mm. The length _{L 2} of a partial section 112B of the second optical waveguide 112 is 0.5 mm, the length _{L 2} of a partial section 114B of the fourth optical waveguide 114 is 5 mm.

  The cross-sectional shape of the index matching oil portion is also a 7.5 μm × 7.5 μm square. At both ends of the index matching oil part, an inlet / outlet hole is provided from the upper surface of the overclad 130 to the core through the overclad 130, and a liquid reservoir is provided around the opening so that the liquid can enter and exit. It is possible. With this penetrating structure and the liquid reservoir, even if the volume of the index matching oil changes due to, for example, a change in temperature around the optical waveguide device 10, it is possible to prevent bubbles from entering the index matching oil.

  A temperature measuring apparatus 1 as shown in FIG. 1 is configured using the optical waveguide device 10 configured as described above. The light source unit 20 includes a semiconductor laser element that outputs laser light having a wavelength of 1.55 μm. The detection unit 30 includes a photodiode as a light receiving element.

  The laser light having a wavelength of 1.55 μm output from the light source unit 20 is guided by the optical fiber 51 and enters the incident end of the first optical waveguide 111 of the optical waveguide device 10, and is guided by the optical fiber 53 and guided by the light. The light enters the incident end of the third optical waveguide 113 of the waveguide device 10. Light incident on the incident end of the first optical waveguide 111 of the optical waveguide device 10 is output from the exit end of the first optical waveguide 111 and the exit end of the second optical waveguide 112 via the first Mach-Zehnder interferometer. . Light incident on the incident end of the third optical waveguide 113 of the optical waveguide device 10 is output from the exit end of the third optical waveguide 113 and the exit end of the fourth optical waveguide 114 via the second Mach-Zehnder interferometer. .

  The light output from the emission end of the first optical waveguide 111 is guided by the optical fiber 61 and the power is detected by the detection unit 30. The light output from the emission end of the second optical waveguide 112 is guided by the optical fiber 62 and the power is detected by the detection unit 30. The light output from the emission end of the third optical waveguide 113 is guided by the optical fiber 63 and the power is detected by the detection unit 30. The light output from the emission end of the fourth optical waveguide 114 is guided by the optical fiber 64 and the power is detected by the detection unit 30.

Then, the analyzing unit 40, the power P ₁ of the light incident on the entrance end of the first optical waveguide _{111, in} the power of light incident on the entrance end of the third optical waveguide 113 P _{3, in,} first optical The power P _{1, out of} light emitted from the exit end of the waveguide 111, the power P _{2, out of} light emitted from the exit end of the second optical waveguide 112, and the light emitted from the exit end of the third optical waveguide 113 From the incident end of the first optical waveguide 111 to the output end of the first optical waveguide 111 based on the power P _{3, out} of the first optical waveguide 114 and the power P4 _{, out} of the light emitted from the output end of the fourth optical waveguide 114 transmission loss alpha ₁ of _light emission of the first transmission loss alpha ₂ of light from the incident end to the exit end of the second optical waveguide 112 of the optical waveguide _111, third third optical waveguide 113 from the incident end of the optical waveguide 113 transmission loss alpha ₃ of the light to the edge, and the third optical waveguide 113 Transmission loss alpha ₄ of light to the exit end of the fourth optical waveguide 114 is obtained from the incident end, further, the temperature of the optical waveguide device 10 is determined on the basis of these transmission losses alpha ₁ to? _4.

FIG. 5 is a graph showing the temperature dependence of the transmission losses α ₁ and α ₂ in the optical waveguide device 10 according to the present embodiment. FIG. 6 is a graph showing the temperature dependence of the transmission losses α ₃ and α ₄ in the optical waveguide device 10 according to this embodiment. These relationships are measured in advance using a furnace whose temperature is known.

The optical waveguide device 10 is installed at a place where the temperature is to be measured, and the temperature is measured. It is known by other simple thermometers that the temperature of this place is in the range of 40 ° C. to 50 ° C. For example, when the transmission loss α ₁ is 6.2 dB and the transmission loss α ₂ is 1.4 dB, the temperature is 43.3 ° C. Furthermore, when the transmission loss α ₃ is 1.3 dB and the transmission loss α ₄ is 6.3 dB in the same temperature state, it can be seen that the temperature is 43.25 ° C. When an optical measurement system having an optical output measurement accuracy of about ± 0.2 dB is used, the temperature measurement accuracy is ± 0.006 if the value of transmission loss α _{4 having} a large slope of the tangent of the curve is used in this temperature range. It becomes about ℃.

  In the Mach-Zehnder interferometer, the temperature that gives the same optical output is periodically cycled as can be seen from FIGS. If only one Mach-Zehnder interferometer is used, it is not possible to know which temperature range is being measured.

That is, in the optical waveguide device 10, α ₁ is 6.2 dB and α ₂ is 1.4 dB, as can be seen from FIG. 5, in addition to around 43.3 ° C. and around 37 ° C. (FIG. 5, There are a plurality of points A), around 25 ° C. (FIG. 5, point B). Whether the temperature being measured is 25 ° C., 37 ° C., or 43 ° C. can be sufficiently measured by another simple thermometer. Knowing the value, more accurate temperature can be known from α ₁ and α ₂ .

In the optical waveguide device 10, α ₃ is 1.3 dB and α ₄ is 6.3 dB, as can be seen from FIG. 6, in addition to 43.25 ° C., around 42.6 ° C. (FIG. C), around 41.3 ° C. (FIG. 6, point D), and around 40.6 ° C. (FIG. 6, point E). Since the measurement temperature range is known to be around 43.3 ° C. from the values of α ₁ and α ₂ , it is possible to determine that the temperature of the measurement target is 43.25 ° C. from α ₃ and α _4. it can.

  Assuming that an optical measurement system with an optical output measurement accuracy of about ± 0.2 dB is used, the longer the length of a section of the Mach-Zehnder interferometer, the greater the loss change with respect to the temperature change near a target temperature. Therefore, it is possible to perform temperature measurement with high sensitivity to temperature, that is, with higher accuracy.

On the other hand, the longer the partial section, the shorter the period of loss change with respect to temperature change. The temperature interval giving the same “α ₁ and α ₂ ” or “α ₃ and α ₄ ” is reduced. Therefore, the length of the partial section of the first Mach-Zehnder interferometer is set so that the temperature period giving the same “α ₁ and α ₂ ” does not become smaller than the temperature accuracy that can be measured by another simple thermometer. Is preferred. At this time, some sections should not be too long. Similarly, the length of the partial section of the second Mach-Zehnder interferometer is set so that the temperature period that gives the same “α ₃ and α ₄ ” is not too small than the temperature accuracy that can be measured by the first Mach-Zehnder interferometer. It is preferable to do this. At this time, some sections should not be too long.

The first Mach-Zehnder interferometer sets the length of the partial section so that the period of temperature change of α ₁ and α ₂ is about 5 to 10 ° C., and the second Mach-Zehnder interferometer is the length of the partial section. Is preferably set to be about 5 to 20 times that of the first Mach-Zehnder interferometer.

It is a lineblock diagram of temperature measuring device 1 concerning this embodiment. 1 is a plan view of an optical waveguide device 10 according to the present embodiment. It is sectional drawing of the optical waveguide of each place in the optical waveguide device 10 which concerns on this embodiment. It is process drawing explaining the manufacturing method of the optical waveguide device 10 which concerns on this embodiment. It is a graph which shows the temperature dependence of each of transmission loss (alpha) ₁ , (alpha) ₂ in the optical waveguide device 10 which concerns on this embodiment. It is a graph which shows the temperature dependence of each of transmission loss (alpha) ₃ , (alpha) ₄ in the optical waveguide device 10 which concerns on this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Temperature measuring apparatus, 10 ... Optical waveguide type device, 20 ... Light source part, 30 ... Detection part, 40 ... Analysis part, 51, 53 ... Optical fiber for incidence, 61-64 ... Optical fiber for output, 100 ... Substrate, DESCRIPTION OF SYMBOLS 111 ... 1st optical waveguide, 112 ... 2nd optical waveguide, 113 ... 3rd optical waveguide, 114 ... 4th optical waveguide, 121 ... 1st optical coupler, 122 ... 2nd optical coupler, 123 ... 3rd optical coupler, 124 ... 4th optical coupler, 130 ... Over clad.

Claims (8)

A first optical waveguide, a second optical waveguide, a third optical waveguide, and a fourth optical waveguide are formed on the substrate;
The first optical waveguide and the second optical waveguide are optically coupled in each of the first optical coupler and the second optical coupler to form a first Mach-Zehnder interferometer,
Unlike the other optical waveguide portions, the temperature dependence of the refractive index of the core in the partial section (length L ₂ ) of the second optical waveguide between the first optical coupler and the second optical coupler is different.
The third optical waveguide and the fourth optical waveguide are optically coupled in the third optical coupler and the fourth optical coupler to form a second Mach-Zehnder interferometer,
Between the third optical coupler and the fourth optical coupler, the temperature dependence of the refractive index of the core in a partial section (length L ₄ , where L ₂ ≠ L ₄ ) of the fourth optical waveguide is different. Different from the optical waveguide part,
An optical waveguide device characterized by that.   2. The optical waveguide device according to claim 1, wherein a core of each of the partial sections of the second optical waveguide and the partial sections of the fourth optical waveguide is made of a liquid.   In each of the partial section of the second optical waveguide and the partial section of the fourth optical waveguide, at least two injection holes for injecting liquid into the core portion pass through the overcladding from the core. 3. The optical waveguide device according to claim 2, wherein the optical waveguide device is provided up to the upper surface.   In each of the partial section of the second optical waveguide and the partial section of the fourth optical waveguide, a liquid pool is provided around the opening of each injection hole on the over clad. The optical waveguide device according to claim 3. The optical waveguide device according to any one of claims 1 to 4,
A light source unit that outputs light;
The light output from the light source unit is incident on one end of either the first optical waveguide or the second optical waveguide of the optical waveguide device, and the light output from the light source unit is the optical waveguide type An incident optical system that is incident on one end of either the third optical waveguide or the fourth optical waveguide of the device;
A detector for detecting the power of light emitted from the other end of each of the first optical waveguide, the second optical waveguide, the third optical waveguide, and the fourth optical waveguide of the optical waveguide device;
An emission optical system for guiding light from the other end of each of the first optical waveguide, the second optical waveguide, the third optical waveguide, and the fourth optical waveguide of the optical waveguide device to the detection unit;
An analysis unit for obtaining a temperature of the optical waveguide device based on a detection result by the detection unit;
A temperature measuring device comprising:   The temperature measuring apparatus according to claim 5, wherein each of the incident optical system and the output optical system includes an optical fiber that inputs and outputs light to and from the optical waveguide device. Using the optical waveguide device according to any one of claims 1 to 4,
Light is incident on one end of either the first optical waveguide or the second optical waveguide, and the power P ₁ of light emitted from the other end of the first optical waveguide is detected via the first Mach-Zehnder interferometer. to together, to detect the power P ₂ of the light emitted from the other end of said second optical waveguide via said first Mach-Zehnder interferometer,
Light is incident on one end of either the third optical waveguide or the fourth optical waveguide, and the power P ₃ of light emitted from the other end of the third optical waveguide is detected via the second Mach-Zehnder interferometer. And detecting the power P ₄ of light emitted from the other end of the fourth optical waveguide via the second Mach-Zehnder interferometer,
Measuring the temperature of the optical waveguide device based on these four optical powers P _{1 to} P ₄ ;
A temperature measurement method characterized by that.   8. The temperature measuring method according to claim 7, wherein light is incident on and emitted from the optical waveguide device using an optical fiber.

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