JPH0440649B2 - - Google Patents
Info
- Publication number
- JPH0440649B2 JPH0440649B2 JP57042585A JP4258582A JPH0440649B2 JP H0440649 B2 JPH0440649 B2 JP H0440649B2 JP 57042585 A JP57042585 A JP 57042585A JP 4258582 A JP4258582 A JP 4258582A JP H0440649 B2 JPH0440649 B2 JP H0440649B2
- Authority
- JP
- Japan
- Prior art keywords
- polarization
- optical fiber
- temperature
- optical
- light
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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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
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Temperature Or Quantity Of Heat (AREA)
- Arrangements For Transmission Of Measured Signals (AREA)
- Radiation Pyrometers (AREA)
Description
【発明の詳細な説明】
本発明は、光フアイバを用いた温度センサに関
するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature sensor using an optical fiber.
従来、光フアイバを用いた温度センサとして、
第１図に示すようなものが提案されている。図に
おいて、光源１１からの光はビーム・スプリツタ
１２で２分岐され、それぞれ光フアイバ１３及び
光フアイバ１４に入射される。この２本の光フア
イバ１３，１４の長さの差により、光のコヒーレ
ンス長以内では、２本の光フアイバ１３，１４を
伝搬してくる光波によつて干渉縞１５が作られ
る。この干渉縞１５は、２光波の光路長差が変化
するとともに移動する。従つて、この干渉縞の移
動量から、２本の光フアイバ長の相対変化量を測
定することができる。一方、光フアイバは温度変
化によつて長さが伸縮するため、２本の光フアイ
バ１３，１４のうち１本を温度測定用として用い
ると、上述した原理により、温度変化に対して干
渉縞が変化し、その変化量から温度変動量が測定
できる。この方式は、２本の光フアイバを用いて
いることや、１本の光フアイバは温度変化を受け
ないように、恒温槽に入れておく必要がある等、
測定系が複雑化する欠点があつた。 Conventionally, as a temperature sensor using optical fiber,
Something like the one shown in FIG. 1 has been proposed. In the figure, light from a light source 11 is split into two by a beam splitter 12 and input into optical fibers 13 and 14, respectively. Due to the difference in length between the two optical fibers 13 and 14, interference fringes 15 are created by the light waves propagating through the two optical fibers 13 and 14 within the coherence length of the light. This interference fringe 15 moves as the optical path length difference between the two light waves changes. Therefore, the amount of relative change in the lengths of the two optical fibers can be measured from the amount of movement of the interference fringes. On the other hand, since the length of optical fibers expands and contracts due to temperature changes, if one of the two optical fibers 13 and 14 is used for temperature measurement, interference fringes will occur due to temperature changes due to the above-mentioned principle. The amount of temperature fluctuation can be measured from the amount of change. This method uses two optical fibers, and one optical fiber must be placed in a constant temperature bath to prevent temperature changes.
The disadvantage was that the measurement system became complicated.
本発明は、１本の光フアイバを用いるだけで簡
単に温度変化を測定できる温度センサを提供する
ものである。 The present invention provides a temperature sensor that can easily measure temperature changes using only one optical fiber.
本発明は、光学ガラスである偏波面保存光フア
イバの直交する２つの偏光軸にそれぞれ沿う２つ
の光伝送路を干渉計の２つの光路として用い、こ
の２つの光路長差が温度によつて直線的に変化す
ることを利用し、温度変化を干渉出力変化として
測定する点に特徴がある。 The present invention uses two optical transmission paths along two orthogonal polarization axes of a polarization-maintaining optical fiber, which is an optical glass, as two optical paths of an interferometer, and the difference in the length of these two optical paths is changed to a straight line depending on the temperature. It is characterized by the fact that temperature changes are measured as interference output changes by taking advantage of changes in temperature.
本発明の原理を説明するための原理図を第２図
及び第３図に示した。第２図において、光波２１
はビーム・スプリツタ２２で２分岐され、光波２
６と光波２７とに別れる。これらの２光波は、ミ
ラ２３，２４で折り返され、再びビーム・スプリ
ツタ２５で合成される。この合成波２８の光出力
Ｉは、２光波２６，２７の光パワーをI1，I2とす
ると一般に次式で表わされる。 Principle diagrams for explaining the principle of the present invention are shown in FIGS. 2 and 3. In FIG. 2, light wave 21
is split into two by the beam splitter 22, and the light wave 2
6 and light wave 27. These two light waves are reflected by mirrors 23 and 24 and combined again by beam splitter 25. The optical output I of this composite wave 28 is generally expressed by the following equation, where I 1 and I 2 are the optical powers of the two optical waves 26 and 27.
Ｉ＝I1＋I2＋2γ√1・2cos (1)
ここで、γは光源の干渉度を表わし、一般に０＜
γ＜１である。は光波２６の伝搬する光路長
と、光波２７の伝搬する光路長との差Δdから生
じる光波２６と光波２７との位相差で、次式で表
わされる。 I=I 1 +I 2 +2γ√ 1・2 cos (1) Here, γ represents the degree of interference of the light source, and generally 0<
γ<1. is the phase difference between the light waves 26 and 27 resulting from the difference Δd between the optical path length of the light waves 26 and the optical path length of the light waves 27, and is expressed by the following equation.
＝2π・Δd／λ (2) λは光の波長である。 =2π・Δd／λ (2) λ is the wavelength of light.
従つて、光遅延路２９を動かすことにより合成
信号２８の光出力Ｉは、(1)式により正弦波状に変
化する。この干渉計は一般にマツハ・ツエンダの
干渉計と呼ばれている。この干渉計は、偏波面保
存光フアイバを用いて第３図のように構成するこ
とができる。第３図において、直線偏光波３１を
偏波面保存光フアイバ３５の直交する２軸３３，
３４の中間に入るように傾けて入射させる。直線
偏光波を任意の角度に回転するには、半波長板３
２の直線偏光波に対する角度を変えることで可能
である。こうすると、直線偏光波３１０の偏波面
保存光フアイバ３５の直交する２軸３３，３４へ
の成分である光波３８，３９は、それぞれ独立に
偏波面保存光フアイバ３５を伝搬することにな
る。直交した光波間では干渉は生じないので、出
力側では偏波面保存光フアイバ３５の直交する２
軸３３，３４の中間に検光子３１１の軸がくるよ
うにセツトしておく。この結果、光波３８と光波
３９との検光子３１１の軸への成分による合成波
３６が得られ、この光出力Ｉは(1)式によつて与え
られる。これは、第２図に示した干渉計と等価で
あり、第２図のビーム・スプリツタ２２及びビー
ム・スプリツタ２５は、第３図の偏波面保存光フ
アイバ３５の入射面３７及び検光子３１１に相当
する。 Therefore, by moving the optical delay path 29, the optical output I of the composite signal 28 changes sinusoidally according to equation (1). This interferometer is generally called the Matsuha-Zenda interferometer. This interferometer can be constructed as shown in FIG. 3 using a polarization maintaining optical fiber. In FIG.
34 so that it enters the beam at an angle. To rotate a linearly polarized wave to an arbitrary angle, use a half-wave plate 3.
This is possible by changing the angle with respect to the linearly polarized light wave. In this way, the light waves 38 and 39, which are the components of the linearly polarized light wave 310 toward the two orthogonal axes 33 and 34 of the polarization-maintaining optical fiber 35, propagate through the polarization-maintaining optical fiber 35 independently. Since no interference occurs between orthogonal light waves, on the output side, two orthogonal light waves of the polarization maintaining optical fiber 35
The analyzer 311 is set so that its axis is located between the axes 33 and 34. As a result, a composite wave 36 is obtained by the components of the light wave 38 and the light wave 39 toward the axis of the analyzer 311, and the light output I is given by equation (1). This is equivalent to the interferometer shown in FIG. 2, and the beam splitter 22 and beam splitter 25 in FIG. Equivalent to.
一方、第３図において、偏波面保存光フアイバ
３５の２軸３３，３４に沿う光導波路は、屈折率
が互いに異なるため、入力側で同時に入つた２光
波３８，３９も、出力側では次式で表わされる時
間差Δτが生じる。 On the other hand, in FIG. 3, since the optical waveguides along the two axes 33 and 34 of the polarization maintaining optical fiber 35 have different refractive indexes, the two light waves 38 and 39 that entered simultaneously on the input side will also form the following equation on the output side: A time difference Δτ occurs.
Δτ＝１／Ｃ・Ｌ・Cp・ａ・（T0−Ｔ） (3)
ここで、Ｃは空気中での光速、Ｌは偏波面保存光
フアイバ３５の長さ、Cpは偏波面保存光フアイ
バ３５の光弾性定数、ａは偏波面保存光フアイバ
３５のヤング率とポアソン比及び熱膨張係数に関
係する比例係数は、T0はシリカガラスの軟化温
度で約1000℃、また、Ｔは偏波面保存光フアイバ
の置かれている雰囲気温度である。Δτは、２光
波３８，３９の位相差と次式で与えられる関係
がある。 Δτ=1/C・L・Cp・a・(T 0 −T) (3) Here, C is the speed of light in air, L is the length of the polarization maintaining optical fiber 35, and Cp is the polarization maintaining optical fiber 35. The photoelastic constant of the fiber 35, a is the proportionality coefficient related to the Young's modulus, Poisson's ratio, and coefficient of thermal expansion of the polarization preserving optical fiber 35, T0 is the softening temperature of silica glass, which is approximately 1000°C, and T is the polarization This is the ambient temperature in which the wavefront preserving optical fiber is placed. Δτ has a relationship with the phase difference between the two light waves 38 and 39 given by the following equation.
＝Δτ・Ｃ・2π／λ (4)
(3)式を(4)式に代入すると、位相差は次式で与え
られる。 =Δτ・C・2π/λ (4) When formula (3) is substituted into formula (4), the phase difference is given by the following formula.
＝2π／λ・Ｌ・Cp・ａ・（T0−Ｔ） (5)
(5)式は、偏波面保存光フアイバ３５の雰囲気温
度が変化すると光波３８、光波３９の位相差が変
化することを示している。このことは、第３図に
おける偏波面保存光フアイバ３５の雰囲気温度の
変化が、第２図における光遅延路２９の動きに相
当することを意味している。従つて、第３図にお
いて、偏波面保存光フアイバ３５の雰囲気温度の
変化に対して、検光子３１１の出力は(1)式に従つ
て変化する。偏波面保存光フアイバ３５の雰囲気
温度変化に対する検光子３１１の出力変化の実験
結果の１例を第４図に示した。温度変化に対して
光出力が正弦波状に変化している様子が分る。 =2π/λ・L・Cp・a・(T 0 −T) (5) Equation (5) shows that when the ambient temperature of the polarization preserving optical fiber 35 changes, the phase difference between the light waves 38 and 39 changes. It shows. This means that the change in the ambient temperature of the polarization maintaining optical fiber 35 in FIG. 3 corresponds to the movement of the optical delay path 29 in FIG. 2. Therefore, in FIG. 3, the output of the analyzer 311 changes according to equation (1) with respect to changes in the ambient temperature of the polarization-maintaining optical fiber 35. FIG. 4 shows an example of experimental results of changes in the output of the analyzer 311 with respect to changes in the ambient temperature of the polarization preserving optical fiber 35. It can be seen that the optical output changes sinusoidally in response to temperature changes.
(5)式を温度Ｔで微分すると、単位温度変化に対
する位相変化量の割合が求められ次式で表わされ
る。 By differentiating equation (5) with respect to temperature T, the ratio of the amount of phase change to a unit temperature change is obtained and is expressed by the following equation.
d／dT＝−2π／λ・Ｌ・Cp・ａ (6)
(6)式より、温度変化と位相変化とは線型の関係に
あることが分る。従つて、位相の変化に伴う光出
力レベルの変化から温度変化量を測定することが
できる。 d/dT=-2π/λ・L・Cp・a (6) From equation (6), it can be seen that there is a linear relationship between temperature change and phase change. Therefore, the amount of temperature change can be measured from the change in the optical output level due to the change in phase.
本発明の基本構成図を第５図に示す。第５図の
構成は上で述べた原理にもとづいている。図にお
いて、光源５１からの光波は、偏光板５２により
直線偏光となる。この直線偏光波は、半波長板５
３により温度測定対象物５８の中におかれた偏波
面保存光フアイバ５４の直交する２軸の中間に傾
けられる。出力側では、検光子５５によつて直交
している２光波の検光子５５の軸方向成分だけ
が、受光器５６によつて受けられる。この出力
は、例えばレコーダ５７等によつて連続的にモニ
ターすることができる。このような構成により、
上述の原理に基づいて温度変化を測定することが
できる。 A basic configuration diagram of the present invention is shown in FIG. The configuration of FIG. 5 is based on the principles described above. In the figure, a light wave from a light source 51 becomes linearly polarized light by a polarizing plate 52. This linearly polarized light wave is transmitted to the half-wave plate 5
3, the polarization-maintaining optical fiber 54 placed in the temperature measurement object 58 is tilted to the middle of two orthogonal axes. On the output side, only the axial components of the two light waves, which are orthogonal to each other by the analyzer 55, are received by the light receiver 56. This output can be continuously monitored, for example by a recorder 57 or the like. With such a configuration,
Temperature changes can be measured based on the principles described above.
以上のように本発明は、光学ガラスである偏波
面保存光フアイバの直交する２つの伝送路を干渉
計の２つの光路として用い、この２つの光路長の
差が温度によつて直線的に変化することを利用
し、温度変化を干渉出力変化として測定する点に
特徴があるので、次のような効果を有する。 As described above, the present invention uses two orthogonal transmission paths of a polarization-maintaining optical fiber, which is an optical glass, as two optical paths of an interferometer, and the difference in the length of these two optical paths changes linearly depending on the temperature. It is characterized by the fact that temperature changes are measured as interference output changes by taking advantage of the fact that
恒温槽が不要であるなど、構成が従来のもの
と比較すると簡単である。 The configuration is simpler than conventional ones, such as not requiring a constant temperature bath.
(6)式に示されているように単位温度変化に対
する位相の変化率が一定しているという直線的
変化であるから測定温度範囲が広い温度センサ
が容易に得られる。 As shown in equation (6), since the change is a linear change in which the rate of change in phase with respect to unit temperature change is constant, a temperature sensor with a wide measurement temperature range can be easily obtained.
フアイバの長さを長くすることにより、温度
測定感度を大きくすることができる。例えば、
第４図の例では、点線で示す周期は、フアイバ
長を1mにしたときのものであり、実線で示す
周期は、フアイバ長を20mにしたときのもので
ある。このようにフアイバ長が20倍になると、
温度変化に対する光出力変化の周期が20分の１
になり、温度測定感度が20倍になる。 By increasing the length of the fiber, temperature measurement sensitivity can be increased. for example,
In the example of FIG. 4, the period shown by the dotted line is when the fiber length is 1 m, and the period shown by the solid line is when the fiber length is 20 m. In this way, when the fiber length increases by 20 times,
The period of light output change due to temperature change is 1/20th
, temperature measurement sensitivity is increased by 20 times.
第１図は従来の温度センサの例を示す系統図、
第２図は本発明の原理を説明するための系統図、
第３図は本発明に用いる光干渉計の原理を説明す
るための斜視図、第４図は本発明の動作を説明す
るための特性図、第５図は本発明の実施例を示す
構成図である。
１１……光源、１２……ビーム・スプリツタ、
１３，１４……光フアイバ、１５……干渉縞、２
１，２６，２７……光波、２２，２５……ビー
ム・スプリツタ、２３，２４……ミラ、２８……
合成波、２９……光遅延路、３１……直線偏光
波、３２……半波長板、３３，３４……光軸、３
５……偏波面保存光フアイバ、３６……合成波、
３７……入射面、３８，３９……光波、３１０…
…直線偏光波、３１１……検光子、５１……光
源、５２……偏光板、５３……半波長板、５４…
…偏波面保存光フアイバ、５５……検光子、５６
……受光器、５７……レコーダ、５８……温度測
定対象物。
Figure 1 is a system diagram showing an example of a conventional temperature sensor.
FIG. 2 is a system diagram for explaining the principle of the present invention,
Fig. 3 is a perspective view for explaining the principle of the optical interferometer used in the present invention, Fig. 4 is a characteristic diagram for explaining the operation of the present invention, and Fig. 5 is a configuration diagram showing an embodiment of the present invention. It is. 11...Light source, 12...Beam splitter,
13, 14...Optical fiber, 15...Interference fringe, 2
1, 26, 27...Light wave, 22, 25...Beam splitter, 23, 24...Mira, 28...
Combined wave, 29... Optical delay path, 31... Linearly polarized light wave, 32... Half-wave plate, 33, 34... Optical axis, 3
5...Polarization preserving optical fiber, 36...Synthetic wave,
37...Incidence plane, 38, 39...Light wave, 310...
...linear polarized light wave, 311 ... analyzer, 51 ... light source, 52 ... polarizing plate, 53 ... half-wave plate, 54 ...
...Polarization preserving optical fiber, 55...Analyzer, 56
...Receiver, 57...Recorder, 58...Temperature measurement object.
Claims (1)
の偏光軸を有する光学ガラスである偏波面保存光
フアイバと、前記直線偏光波をその偏波面が前記
直交する２つの偏光軸のほぼ中間に位置するよう
に該偏波面保存光フアイバに入射する入射手段
と、前記２つの偏光軸成分を合成する手段を備
え、前記偏波面保存光フアイバの前記２つの偏光
軸にそれぞれ沿う２つの光伝送路の光路長差が該
偏波面保存光フアイバの雰囲気温度に対応して直
線的に変化することを利用して、温度変化に対応
してレベル変化する出力光をとり出すように構成
された温度センサ。1. A light source that generates a linearly polarized light wave, a polarization preserving optical fiber that is an optical glass having two orthogonal polarization axes, and a polarization plane of the linearly polarized light located approximately midway between the two orthogonal polarization axes. comprising an input means for inputting the light into the polarization-maintaining optical fiber and a means for synthesizing the two polarization axis components, the two optical transmission lines respectively extending along the two polarization axes of the polarization-maintaining optical fiber. A temperature sensor configured to take out output light whose level changes in response to temperature changes by utilizing the fact that the optical path length difference changes linearly in response to the ambient temperature of the polarization preserving optical fiber.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57042585A JPS58160827A (en) | 1982-03-19 | 1982-03-19 | Temperature sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57042585A JPS58160827A (en) | 1982-03-19 | 1982-03-19 | Temperature sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS58160827A JPS58160827A (en) | 1983-09-24 |
| JPH0440649B2 true JPH0440649B2 (en) | 1992-07-03 |
Family
ID=12640139
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP57042585A Granted JPS58160827A (en) | 1982-03-19 | 1982-03-19 | Temperature sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS58160827A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60135732A (en) * | 1983-12-23 | 1985-07-19 | Nippon Telegr & Teleph Corp <Ntt> | Temperature measuring device |
| JPS62194428A (en) * | 1986-02-21 | 1987-08-26 | Fujikura Ltd | Temperature detector due to interference type optical fiber sensor |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6055011B2 (en) * | 1978-07-17 | 1985-12-03 | 三菱電機株式会社 | temperature detection device |
-
1982
- 1982-03-19 JP JP57042585A patent/JPS58160827A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58160827A (en) | 1983-09-24 |
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