JP2009025188A

JP2009025188A - Temperature compensation method of physical quantity and temperature compensation type optical fiber sensor

Info

Publication number: JP2009025188A
Application number: JP2007189509A
Authority: JP
Inventors: Akira Sakamoto; 明坂元; Keiichi Horimoto; 啓一堀本; Yoshikiyo Noguchi; 善清野口
Original assignee: Fujikura Ltd
Current assignee: Fujikura Ltd
Priority date: 2007-07-20
Filing date: 2007-07-20
Publication date: 2009-02-05
Anticipated expiration: 2027-07-20
Also published as: JP4932629B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature compensation method and a simple temperature compensation type optical fiber sensor capable of compensating temperature precisely in a three-core array system capable of measuring temperature inexpensively and precisely. <P>SOLUTION: In the measurement of physical quantity using a three-core array system optical fiber sensor, a temperature measurement means is provided at or near a measurement section. Based on temperature measured by the temperature measurement means, distance change temperature compensation for compensating distance variations where the distance between the measurement and reflection sections changes due to the temperature, angle change temperature compensation for compensating angle variations where the angle between the measurement and reflection sections changes due to the temperature, and nonlinear temperature compensation for compensating a nonlinear error generated because the relationship between the physical quantity to be measured and the ratio of light intensity measured by each optical fiber for reception is nonlinear are calculated, thus calculating the physical quantity measured after temperature compensation by (physical quantity measured after temperature compensation = basic physical quantity characteristic - distance change temperature compensation - angle change temperature compensation-nonlinear temperature compensation) according to the basic physical quantity characteristics measured at the temperature. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、光ファイバを用いて圧力などの物理量を測定するセンサ分野に関し、特に、３心アレイ方式において適切な温度補償を行うことで、高精度な測定が可能な物理量の温度補償方法と、該温度補償方法により物理量を高精度に測定可能な温度補償型光ファイバセンサに関する。 The present invention relates to a sensor field for measuring a physical quantity such as pressure using an optical fiber, and in particular, a temperature compensation method for a physical quantity capable of highly accurate measurement by performing appropriate temperature compensation in a three-core array system, and The present invention relates to a temperature compensation type optical fiber sensor capable of measuring a physical quantity with high accuracy by the temperature compensation method.

光ファイバを用い、測定部まで光を導波し、測定部での光状態の変化によりセンシングをする光センサは、測定部で電気を使わないことから防爆性・耐雷性・耐電磁雑音性に優れ、遠隔測定も容易であるなどの利点がある。このようなセンサにおいて、被測定対象が温度以外の物理量である場合、温度変化による特性変化は精度悪化要因となるため、高精度な測定を行う場合には温度変化による影響を補償する必要がある。 An optical sensor that uses an optical fiber to guide light to the measurement unit and senses it based on changes in the light state at the measurement unit, does not use electricity in the measurement unit, so it is explosion-proof, lightning-proof, and electromagnetic noise resistant. There are advantages such as excellent and easy telemetry. In such a sensor, when the object to be measured is a physical quantity other than temperature, the characteristic change due to the temperature change becomes a factor of deterioration in accuracy, so it is necessary to compensate for the influence of the temperature change when performing highly accurate measurement. .

このような温度補償型光ファイバセンサとしては、
・光の干渉を用いる方法（特許文献２参照）、
・光ファイバグレーティングの中心波長変化を測定する方法（特許文献３参照）、
などが提案されている。しかし、これらの方法は、測定原理として、光の波長変化や変調成分を測定するため、測定装置が高価になってしまうという問題があった。また、特許文献３に開示された従来技術では、特殊な構造体を作製したりする必要があり、これも価格が高くなる原因であった。 As such a temperature compensation type optical fiber sensor,
A method using optical interference (see Patent Document 2),
A method for measuring the change in the center wavelength of the optical fiber grating (see Patent Document 3),
Etc. have been proposed. However, these methods have a problem that the measuring apparatus becomes expensive because the measurement principle is to measure the wavelength change of light and the modulation component. Moreover, in the prior art disclosed by patent document 3, it was necessary to produce a special structure, and this was also a cause of a high price.

一方、光強度の変化で測定することで、より安価な測定装置を用いることが可能な方法も提案されている。例えば、特許文献１、特許文献４及び特許文献５などである。これらは、光源からの光をセンシング部まで導光する光ファイバからの出射光を被測定対象物で反射させ、同じ光ファイバに結合する光の強度を測定する方法である。この種の光ファイバセンサは、センシング部の構造が単純であり、強度変化を測定する測定器も比較的安価に実現できるという利点がある。
特開平５−１９６５２８号公報特開平９−５０２８号公報特開２００２−２６７５５７号公報特開２００２−３７２４７２号公報特開平８−６２０８０号公報特開２００７−２４８２６号公報特開２００７−３３０７５号公報 On the other hand, a method has also been proposed in which a cheaper measuring device can be used by measuring with a change in light intensity. For example, Patent Document 1, Patent Document 4, Patent Document 5, and the like. These are methods in which light emitted from an optical fiber that guides light from a light source to a sensing unit is reflected by an object to be measured, and the intensity of the light coupled to the same optical fiber is measured. This type of optical fiber sensor has an advantage that the structure of the sensing unit is simple and a measuring instrument for measuring the intensity change can be realized at a relatively low cost.
Japanese Patent Laid-Open No. 5-196528 Japanese Patent Laid-Open No. 9-5028 JP 2002-267557 A JP 2002-372472 A JP-A-8-62080 JP 2007-24826 A JP 2007-33075 A

しかしながら、前述した光強度の変化で測定する方式の光ファイバセンサは、被測定対象物に対し投光する光ファイバで受光も行うため、反射光をフォトダイオードなどの受光器に入射するためには、光カプラなどの光分岐素子を使用する必要があった。この光分岐素子は、温度依存性や光源の波長依存性があるため、温度や光源の波長変化によって分岐比が変化してしまう。このため、特許文献１，４及び５の構造では、光分岐比の変化により測定値が変化するため、精度悪化の要因となる問題があった。これを回避するために、特許文献４では、当該光分岐部の温度を一定にする機構を追加し、精度の安定化を図っているが、構造が複雑になり、温度制御機構も必要なため、装置が高価格になり、実用上問題となっていた。 However, since the optical fiber sensor of the type that measures by the change of the light intensity described above also receives light by the optical fiber that projects the object to be measured, in order to make the reflected light incident on a light receiver such as a photodiode. It was necessary to use an optical branching element such as an optical coupler. Since this optical branching element has temperature dependency and wavelength dependency of the light source, the branching ratio changes depending on temperature and wavelength change of the light source. For this reason, in the structures of Patent Documents 1, 4 and 5, the measurement value changes due to a change in the optical branching ratio, which causes a problem of deterioration in accuracy. In order to avoid this, in Patent Document 4, a mechanism for keeping the temperature of the optical branching portion constant is added to stabilize the accuracy, but the structure becomes complicated and a temperature control mechanism is also necessary. The device became expensive and practically problematic.

これらの問題を解決する方法として、例えば、特許文献６及び特許文献７に開示された技術が提案されている。これらの方法では、１本の光ファイバからの出射光を２本の光ファイバで受光し、それらの光ファイバに結合した光の強度比を測定することで、測定アレイと反射面との距離を正確に測定することができる（以下、本方式を３心アレイ方式と記す。）。このため、安価で高精度の測定が実現できる。ただし、３心アレイ方式でも、他の方式と同様に温度変化によって生じる基材の膨張などの影響で、光ファイバ端面と反射面との距離が変化してしまうなどが生じるため、精度の良い圧力測定などを行う場合は温度補償が必要であった。この時、３心アレイ方式では、光ファイバ位置と反射面の距離だけを考慮した温度補償方式では、精度の良い補償ができないことが分かった。このため、従来の温度補償方法の延長では、測定する全ての温度域で特性を測定し、対応表を作ることで温度補償する必要がある。この場合、温度補償に必要なデータ数が非常に多くなり、温度補償に必要なデータを取得するための測定に時間がかかることに加え、計算も複雑になるという問題があった。 As a method for solving these problems, for example, techniques disclosed in Patent Document 6 and Patent Document 7 have been proposed. In these methods, the light emitted from one optical fiber is received by two optical fibers, and the intensity ratio of the light coupled to these optical fibers is measured, so that the distance between the measurement array and the reflecting surface is reduced. Accurate measurement can be performed (hereinafter, this method is referred to as a three-core array method). For this reason, inexpensive and highly accurate measurement can be realized. However, even in the three-core array method, the pressure between the optical fiber end surface and the reflecting surface changes due to the expansion of the base material caused by the temperature change, as in the other methods. Temperature compensation was necessary when making measurements. At this time, it was found that with the three-core array method, accurate compensation cannot be achieved with the temperature compensation method considering only the distance between the optical fiber position and the reflecting surface. Therefore, in the extension of the conventional temperature compensation method, it is necessary to perform temperature compensation by measuring characteristics in all temperature ranges to be measured and creating a correspondence table. In this case, there is a problem that the number of data necessary for temperature compensation becomes very large, and it takes time to perform measurement for obtaining data necessary for temperature compensation, and the calculation is complicated.

本発明は、前記事情に鑑みてなされ、安価で高精度な測定を実現できる３心アレイ方式において、簡単でありながら高精度な温度補償が実現可能な温度補償型光ファイバセンサの提供を目的とする。 The present invention has been made in view of the above circumstances, and aims to provide a temperature-compensated optical fiber sensor capable of realizing temperature compensation with high accuracy in a simple manner in a three-core array system capable of realizing inexpensive and highly accurate measurement. To do.

前記目的を達成するため、本発明は、光源と、反射面を有し光ファイバ端面との相対距離が物理量に応じて変化する測定部と、光源からの光を測定部に伝送する投光用光ファイバと、測定部反射面で反射した光を複数の受光部にそれぞれ伝送する複数本の受光用光ファイバと、受光部からの電気信号の比から前記物理量を算出する演算処理回路とを有する光ファイバセンサを用いた物理量測定における物理量の温度補償方法であって、
測定部又はその近傍に温度測定手段を設け、該温度測定手段で測定した温度を元に、
測定部と反射部の距離が温度により変化する距離変動を補償する距離変化温度補償と、測定部と反射部の角度が温度により変化する角度変動を補償する角度変化温度補償と、測定される物理量と各受光用光ファイバで測定される光強度の強度比との関係が線形でないために生じる非線形誤差を補償する非線形温度補償とを算出し、
該温度で測定された基本物理量特性から、次式（Ａ）：
温度補償後測定物理量＝基本物理量特性−距離変化温度補償−角度変化温度補償−非線形温度補償 …（Ａ）
によって温度補償後測定物理量を算出することを特徴とする物理量の温度補償方法を提供する。 In order to achieve the above object, the present invention provides a light source, a measuring unit that has a reflecting surface and a relative distance between the end face of the optical fiber changes according to a physical quantity, and for light projection that transmits light from the light source to the measuring unit. An optical fiber, a plurality of light receiving optical fibers that respectively transmit light reflected by the measurement unit reflection surface to the plurality of light receiving units, and an arithmetic processing circuit that calculates the physical quantity from a ratio of electrical signals from the light receiving units. A temperature compensation method for a physical quantity in physical quantity measurement using an optical fiber sensor,
Based on the temperature measured by the temperature measuring means provided in the measuring part or its vicinity,
Distance variation temperature compensation that compensates for the distance variation in which the distance between the measurement unit and the reflection unit varies with temperature, angle variation temperature compensation that compensates for the angle variation in which the angle between the measurement unit and the reflection unit varies with temperature, and the physical quantity to be measured And non-linear temperature compensation that compensates for non-linear errors caused by the non-linear relationship between the intensity ratio of the light intensity measured by each light receiving optical fiber,
From the basic physical quantity characteristics measured at the temperature, the following formula (A):
Measurement physical quantity after temperature compensation = basic physical quantity characteristics-distance change temperature compensation-angle change temperature compensation-nonlinear temperature compensation (A)
A temperature compensation method for a physical quantity is provided, characterized in that a measured physical quantity after temperature compensation is calculated by:

本発明の物理量の温度補償方法において、以下の手順：
１．各受光用ファイバで測定される光強度（Ｐ１，Ｐ２）の強度比Ｆ（Ｐ１，Ｐ２）＝（Ｐ１−Ｐ２）／（Ｐ１＋Ｐ２）と物理量Ｐ_Ｔ０の関係を測定部の環境温度Ｔ_０で測定し、
２．Ｆ値と物理量Ｐ_Ｔ０の関係を表す関数ｇ（Ｆ）を求め、これを基本物理量特性とし、
Ｐ_Ｔ０＝ｇ（Ｆ） …（１）
３．測定部の異なる環境温度をＴ_ｎとし、強度比Ｆ（Ｐ１，Ｐ２）＝（Ｐ１−Ｐ２）／（Ｐ１＋Ｐ２）と物理量Ｐ_Ｔｎの関係を測定し、
４．各温度で測定した物理量Ｐ_Ｔｎと測定した全ての温度Ｔ_ｎを用い、Ｐ_Ｔｎ温度補償がなされるように、式（２）の温度補償関数、Ａ（Ｔ）、Ｂ（Ｔ），Ｃ（Ｔ）を決定すること、
Ｐ（Ｔ）＝ｇ（Ｆ）−Ａ（Ｔ）−Ｂ（Ｔ）＊Ｆ−Ｃ（Ｔ）＊ｇ’（Ｆ） …（２）
（式中、ｇ’（Ｆ）は（１）式のＦ値での１次微分であり、Ａ（Ｔ）、Ｂ（Ｔ）、Ｃ（Ｔ）は温度Ｔを変数とした関数であり、右辺第２項は距離変化温度補償項、右辺第３項は角度変化温度補償項、右辺第４項は非線形温度補償をそれぞれ表す。）
によって温度補償後測定物理量を算出することが好ましい。 In the physical quantity temperature compensation method of the present invention, the following procedure is performed:
1. Intensity ratio F of the light intensity measured by the light receiving fiber (P1, P2) (P1, P2) = (P1-P2) / (P1 + P2) and measured at ambient temperature _{T 0} of the measuring section the relationship of the physical quantity _{P T0} And
2. A function g (F) representing the relationship between the F value and the physical quantity _PT0 is obtained, and this is used as a basic physical quantity characteristic.
P _T0 = g (F) (1)
3. The environmental temperature of different measuring unit and _{T n,} the intensity ratio F (P1, P2) = ( P1-P2) / (P1 + P2) and to measure the relationship between the physical quantity _{P Tn,}
4). Using all temperature _{T n} and the measured physical quantity _{P Tn} measured at each _temperature, as _{P Tn} temperature compensation is made, the temperature compensation function of equation (2), A (T) , B (T), C ( T),
P (T) = g (F) −A (T) −B (T) * FC (T) * g ′ (F) (2)
(In the formula, g ′ (F) is a first derivative at the F value of the formula (1), A (T), B (T), C (T) are functions with the temperature T as a variable, (The second term on the right side represents the distance change temperature compensation term, the third term on the right side represents the angle change temperature compensation term, and the fourth term on the right side represents the nonlinear temperature compensation.)
The measured physical quantity after temperature compensation is preferably calculated by

本発明の物理量の温度補償方法において、受光用光ファイバの損失（β_１，β_２）を測定し、損失補償定数β（ただし、β＝β_１／β_２）を算出し、この損失補償定数βで測定物理量を更に補償することが好ましい。 In the physical quantity temperature compensation method of the present invention, the loss (β ₁ , β ₂ ) of the light receiving optical fiber is measured to calculate a loss compensation constant β (where β = β ₁ / β ₂ ), and this loss compensation constant It is preferable to further compensate the measured physical quantity with β.

本発明の物理量の温度補償方法において、測定する物理量は、圧力であることが好ましい。 In the physical quantity temperature compensation method of the present invention, the physical quantity to be measured is preferably pressure.

また本発明は、光源と、反射面を有し光ファイバ端面との相対距離が圧力や温度などの物理量に応じて変化する測定部と、光源からの光を測定部に伝送する投光用光ファイバと、測定部反射面で反射した光を複数の受光部にそれぞれ伝送する複数本の受光用光ファイバと、受光部からの電気信号の比から前記物理量を算出する演算処理回路とを有する光ファイバセンサであって、
測定部又はその近傍に温度測定手段が設けられ、
演算処理回路は、該温度測定手段で測定した温度を元に、前述した本発明に係る物理量の温度補償方法を実行し、温度補償後測定物理量を算出するプログラムを有していることを特徴とする温度補償型光ファイバセンサを提供する。 The present invention also provides a measuring unit in which the relative distance between the light source and the end face of the optical fiber having a reflecting surface changes in accordance with a physical quantity such as pressure and temperature, and light for projection that transmits light from the light source to the measuring unit Light having a fiber, a plurality of light receiving optical fibers that respectively transmit light reflected by the reflection surface of the measurement unit to a plurality of light receiving units, and an arithmetic processing circuit that calculates the physical quantity from the ratio of electrical signals from the light receiving units A fiber sensor,
A temperature measuring means is provided at or near the measuring unit,
The arithmetic processing circuit has a program for executing the physical quantity temperature compensation method according to the present invention described above based on the temperature measured by the temperature measuring means and calculating the measured physical quantity after temperature compensation. A temperature compensated optical fiber sensor is provided.

本発明の温度補償型光ファイバセンサにおいて、投光用光ファイバと２本の受光用光ファイバとのそれぞれの先端部が、反射面に対する法線を基準として固定角度θで対称に固定された３心アレイ構造を有していることを特徴とする請求項５に記載の温度補償型光ファイバセンサ。 In the temperature-compensated optical fiber sensor of the present invention, the tip ends of the light projecting optical fiber and the two light receiving optical fibers are fixed symmetrically at a fixed angle θ with respect to the normal to the reflecting surface. 6. The temperature compensated optical fiber sensor according to claim 5, wherein the temperature compensated optical fiber sensor has a core array structure.

本発明の温度補償型光ファイバセンサにおいて、温度測定手段が前記３心アレイ構造を有する光ファイバセンサであることが好ましい。 In the temperature-compensated optical fiber sensor of the present invention, it is preferable that the temperature measuring means is an optical fiber sensor having the three-core array structure.

本発明の温度補償型光ファイバセンサにおいて、予め測定した物理量換算定数、温度補償定数及び温度換算定数を記録しておく不揮発性記憶媒体を演算処理回路に接続したことが好ましい。 In the temperature-compensated optical fiber sensor of the present invention, it is preferable that a nonvolatile storage medium that records physical quantity conversion constants, temperature compensation constants, and temperature conversion constants measured in advance is connected to the arithmetic processing circuit.

本発明によれば、安価で高精度な測定を実現できる３心アレイ方式において、簡単でありながら高精度な温度補償が実現可能となる。 According to the present invention, it is possible to realize temperature compensation with high accuracy while being simple in a three-core array system that can realize inexpensive and highly accurate measurement.

以下、図面を参照して本発明の実施形態を説明する。
なお、以下の記載では、１本の投光用光ファイバと２本の受光用光ファイバを組み合わせた３心アレイ方式光ファイバセンサを例示しているが、本発明の光ファイバセンサは本方式にのみ限定されるものではなく、使用する各光ファイバの本数や配置方法等は適宜変更可能である。また、以下の記載では、物理量として圧力を測定する光ファイバセンサを例示しているが、測定する物理量は圧力にのみ限定されず、他の物理量の測定に適用させることが可能である。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following description, a three-core array type optical fiber sensor in which one light projecting optical fiber and two light receiving optical fibers are combined is illustrated, but the optical fiber sensor of the present invention is applied to this system. However, the number of optical fibers to be used, the arrangement method, and the like can be changed as appropriate. Moreover, although the optical fiber sensor which measures a pressure as a physical quantity is illustrated in the following description, the physical quantity to measure is not limited only to a pressure, It can be applied to the measurement of another physical quantity.

［３心アレイ測定原理］
まず、３心アレイ方式光ファイバセンサの測定原理について、図１を参照して説明する。
３心アレイ方式光ファイバセンサによる測定は、図１に示すように、反射面５を有し光ファイバ端面との相対距離が圧力や温度などの物理量に応じて変化する測定部６と、光源１からの光を測定部６に伝送する投光用光ファイバ２と、測定部６の反射面５で反射した光を２つの受光部７Ａ，７Ｂにそれぞれ伝送する２本の受光用光ファイバ３，４と、受光部７Ａ，７Ｂで光電変換された電気信号の比をとり、物理量を算出する演算処理回路９とから構成されており、反射面５に対向させた３本の光ファイバ端面は、光ファイバ長手方向と反射面に対する法線とのなす角度がθとなるように固定されていることを特徴としている。 [Three-core array measurement principle]
First, the measurement principle of the three-core array type optical fiber sensor will be described with reference to FIG.
As shown in FIG. 1, the measurement using the three-core array type optical fiber sensor includes a measuring unit 6 having a reflecting surface 5 and a relative distance from the end face of the optical fiber that changes in accordance with a physical quantity such as pressure and temperature, and the light source 1. The light projecting optical fiber 2 for transmitting the light from the measuring unit 6 and the two light receiving optical fibers 3 for transmitting the light reflected by the reflecting surface 5 of the measuring unit 6 to the two light receiving units 7A and 7B, respectively. 4 and an arithmetic processing circuit 9 that calculates the physical quantity by taking the ratio of the electrical signals photoelectrically converted by the light receiving portions 7A and 7B, and the three optical fiber end faces opposed to the reflecting surface 5 are: It is characterized in that the angle formed between the longitudinal direction of the optical fiber and the normal to the reflecting surface is fixed to be θ.

図２は前記測定部の拡大図である。図２に示すように、２本の受光用光ファイバ３，４は平行であり、投光用光ファイバ２と受光用光ファイバ３，４とは、反射板５Ａの反射面５に対する法線を基準として固定角度θで対称に固定されている。投光用光ファイバ２からの出射光は、反射面で反射され、受光用光ファイバ３，４にそれぞれ結合した反射光が受光部７Ａ，７Ｂに伝送される。それぞれの受光部７Ａ，７Ｂでは、フォトダイオードなどを用い、光強度を電気信号に変換する。 FIG. 2 is an enlarged view of the measurement unit. As shown in FIG. 2, the two light receiving optical fibers 3 and 4 are parallel, and the light projecting optical fiber 2 and the light receiving optical fibers 3 and 4 are normal to the reflecting surface 5 of the reflecting plate 5A. It is fixed symmetrically at a fixed angle θ as a reference. The outgoing light from the light projecting optical fiber 2 is reflected by the reflecting surface, and the reflected light coupled to the light receiving optical fibers 3 and 4 is transmitted to the light receiving portions 7A and 7B. Each of the light receiving portions 7A and 7B uses a photodiode or the like to convert light intensity into an electric signal.

投光用光ファイバ２及び受光用光ファイバ３，４は、全長にわたり、使用波長においてシングルモードで伝搬する光ファイバを使用している。これは、使用する光ファイバがマルチモードであると、モード間のパワー分布の変化により測定精度が悪化するためである。ここで使用波長とは、使用する光源１における強度スペクトルのピーク波長のことである。シングルモードで伝搬する光ファイバを使用すると、コア径が小さいため光強度を大きくとることが困難となるが、Ａ／Ｄ変換した後にデジタル高速フーリエ変換（ＦＦＴ）を行ったり、測定値演算の積分時間を長くしたりするなど、電気処理により精度良く測定することが可能であり、そのための演算処理回路も安価で入手可能である。 The light projecting optical fiber 2 and the light receiving optical fibers 3 and 4 use optical fibers that propagate in a single mode at the wavelength used over the entire length. This is because if the optical fiber to be used is a multimode, the measurement accuracy deteriorates due to a change in power distribution between modes. Here, the used wavelength is the peak wavelength of the intensity spectrum in the light source 1 to be used. When an optical fiber that propagates in a single mode is used, it is difficult to increase the light intensity because the core diameter is small. However, digital fast Fourier transform (FFT) is performed after A / D conversion, and measurement value calculation is integrated. It is possible to measure with high accuracy by electrical processing such as extending the time, and an arithmetic processing circuit for that purpose can be obtained at low cost.

図３に、光ファイバ端面と反射面５との相対距離Ｄの変化に対する、受光用光ファイバ３，４のそれぞれの反射光強度Ｐ１，Ｐ２および強度比Ｆ（Ｐ１，Ｐ２）を示す（以下、距離依存性と記す。）。強度比Ｆの演算式としては、Ｐ１／Ｐ２、Ｐ２／Ｐ１、（Ｐ１−Ｐ２）／（Ｐ１＋Ｐ２）、（Ｐ２−Ｐ１）／（Ｐ１＋Ｐ２）などが挙げられる。今回は、強度比Ｆ（Ｐ１，Ｐ２）＝（Ｐ１−Ｐ２）／（Ｐ１＋Ｐ２）を用い検討した。これは、本方式では、分母に（Ｐ１，Ｐ２）の和、分子にＰ１，Ｐ２の差をとることで、強度比Ｆ値の距離依存性がより線形に近い特性が得られ、精度良く測定できるためである。図３は横軸が相対距離Ｄ，縦左軸が光強度、縦右軸が強度比を示す。反射光強度Ｐ１とＰ２は、それぞれ異なる位置でピークをもつ曲線となる。これにより、それぞれのピークの間で得られる強度比は、単調変化を有する曲線となる。物理量変化による反射面５と３心アレイの光ファイバ先端との相対距離Ｄの変化を測定する場合は、この単調変化部が使用される。また測定感度は、この曲線の傾きΔ＝ｄＦ（Ｐ１，Ｐ２）／ｄＤで表され、Δが大きい方が測定感度は良くなる。 FIG. 3 shows the respective reflected light intensities P1, P2 and intensity ratios F (P1, P2) of the light receiving optical fibers 3 and 4 with respect to changes in the relative distance D between the end face of the optical fiber and the reflecting surface 5 (hereinafter, It is written as distance dependency.) Examples of the calculation formula of the intensity ratio F include P1 / P2, P2 / P1, (P1-P2) / (P1 + P2), (P2-P1) / (P1 + P2), and the like. This time, the intensity ratio F (P1, P2) = (P1-P2) / (P1 + P2) was used for examination. In this method, by taking the sum of (P1, P2) in the denominator and the difference between P1, P2 in the numerator, the distance dependence of the intensity ratio F value is more linear and the measurement is accurate. This is because it can. In FIG. 3, the horizontal axis represents the relative distance D, the vertical left axis represents the light intensity, and the vertical right axis represents the intensity ratio. The reflected light intensities P1 and P2 are curves having peaks at different positions. Thereby, the intensity ratio obtained between the respective peaks becomes a curve having a monotonous change. When measuring a change in the relative distance D between the reflecting surface 5 and the tip of the optical fiber of the three-core array due to a change in physical quantity, this monotonous change portion is used. The measurement sensitivity is represented by the slope of this curve Δ = dF (P1, P2) / dD, and the larger the Δ, the better the measurement sensitivity.

本方法では、測定値として光強度Ｐ１及びＰ２の強度比Ｆを用いるため、光源の光強度が変化しても測定値が変化せず、安定した測定ができる。また、測定部６から受光部７Ａ，７Ｂの間に光分岐素子を使用しないことにより、光源１の波長変化による影響も小さく、高精度の測定が実現できる。これにより、比較的安価に入手可能なＬＥＤ光源などを用いても、高精度の測定が実現できる。 In this method, since the intensity ratio F of the light intensities P1 and P2 is used as the measurement value, the measurement value does not change even when the light intensity of the light source changes, and stable measurement can be performed. Further, by not using an optical branching element between the measuring unit 6 and the light receiving units 7A and 7B, the influence of the wavelength change of the light source 1 is small, and high-accuracy measurement can be realized. Thereby, even if it uses the LED light source etc. which can be obtained comparatively cheaply, a highly accurate measurement is realizable.

図４に、光ファイバ固定角度θが異なる、３心アレイ方式光ファイバセンサを用いて測定した強度比Ｆの距離依存性を示す。図４に示すように、固定角度θを大きくするとΔは大きくなり、逆にθを小さくするとΔは小さくなる。このように、固定角度θを変化させるとΔが変化するため、これを利用し測定感度を容易に選択することが可能となる。ここで測定範囲、つまり距離依存性において線形のスロープが存在する相対距離範囲は、測定感度とトレードオフの関係にあり、測定感度が大きくなると測定範囲は狭く、逆に測定感度が小さくなると測定範囲は広くなる。 FIG. 4 shows the distance dependency of the intensity ratio F measured using a three-core array type optical fiber sensor having different optical fiber fixing angles θ. As shown in FIG. 4, when the fixed angle θ is increased, Δ increases, and conversely, when θ is decreased, Δ decreases. Thus, since Δ changes when the fixed angle θ is changed, it is possible to easily select the measurement sensitivity using this. Here, the measurement range, that is, the relative distance range in which a linear slope exists in the distance dependence, has a trade-off relationship with the measurement sensitivity. The measurement range becomes narrower when the measurement sensitivity increases, and conversely, the measurement range decreases when the measurement sensitivity decreases. Becomes wider.

ここで、図４の測定に用いた３心アレイ方式光ファイバセンサは、光通信に用いられるシングルモード光ファイバ（ＩＴＵ−ＴＧ．６５２．Ｂ相当）と石英ガラス製のＶ溝アレイ基板を使用し作製した。図２のように各光ファイバを固定角度θで固定する場合、光ファイバが収まるようにＶ溝加工を行った基板を用いることで精度良く光ファイバを固定することができる。光ファイバの固定方法としては、Ｖ溝アレイ基板の各Ｖ溝に沿って光ファイバを仮止めし、上部からＶ溝加工なしの石英板（光ファイバ押え蓋）で挟んだ状態で樹脂によって固定する。これにより３本の光ファイバは、同一平面上に精度良く固定することができ、高さばらつきによる強度変動がなく、測定精度の悪化を防ぐことができる。ここで、Ｖ溝アレイ基板に石英ガラス基板を用いるのは、光ファイバが同じ石英ガラス製であり、両者の線膨張係数を同じにするためである。図５は、図２中のＡ−Ａ’断面図であり、この図５中、符号１０Ａ，１０Ｂ，１０Ｃは光ファイバ、１１Ａ，１１Ｂ，１１Ｃは各光ファイバのコア、１２はＶ溝アレイ基板、１３は光ファイバ押え蓋をそれぞれ表している。以下、図２及び図５に示す３心アレイ方式光ファイバセンサの先端部分を３心アレイと略記する。 4 uses a single-mode optical fiber (equivalent to ITU-T G.652.B) used for optical communication and a quartz glass V-groove array substrate. And made. When each optical fiber is fixed at a fixed angle θ as shown in FIG. 2, the optical fiber can be fixed with high accuracy by using a substrate that has been V-grooved so that the optical fiber can be accommodated. As a method of fixing the optical fiber, the optical fiber is temporarily fixed along each V groove of the V groove array substrate, and is fixed with resin in a state of being sandwiched from above by a quartz plate (optical fiber presser cover) without V groove processing. . As a result, the three optical fibers can be accurately fixed on the same plane, there is no fluctuation in strength due to height variations, and deterioration in measurement accuracy can be prevented. Here, the reason why the quartz glass substrate is used for the V-groove array substrate is that the optical fibers are made of the same quartz glass, and the linear expansion coefficients of both are the same. 5 is a cross-sectional view taken along the line AA 'in FIG. 2. In FIG. 5, reference numerals 10A, 10B, and 10C are optical fibers, 11A, 11B, and 11C are cores of the respective optical fibers, and 12 is a V-groove array substrate. , 13 represent optical fiber pressing covers. Hereinafter, the tip portion of the three-core array type optical fiber sensor shown in FIGS. 2 and 5 is abbreviated as a three-core array.

［温度補償方法］
この３心アレイ方式光ファイバセンサを用い、圧力測定を行った場合の温度特性について検討を行った。
圧力測定には、圧力が加わると変形するダイアフラムを使用した。図６に示すように、筒部１４の端にダイアフラム１５を設け、該筒部１４内にその先端をダイアフラム１５に向けて圧力測定用の３心アレイ１６を配置した。この時、測定部の温度が上昇するとダイアフラム１５及び筒部１４の材料が熱膨張し、３心アレイ１６先端とダイアフラム１５の距離が変化する。通常、従来のセンサにおいては、この距離変化を補償する計算を実行していたが、高精度に補償が必要な場合は、それだけでは補償できないことが分かった。 [Temperature compensation method]
Using this three-core array type optical fiber sensor, the temperature characteristics when pressure was measured were examined.
For the pressure measurement, a diaphragm that deforms when pressure is applied was used. As shown in FIG. 6, a diaphragm 15 is provided at the end of the cylindrical portion 14, and a three-core array 16 for pressure measurement is arranged in the cylindrical portion 14 with the tip thereof facing the diaphragm 15. At this time, when the temperature of the measurement part rises, the material of the diaphragm 15 and the cylinder part 14 is thermally expanded, and the distance between the tip of the three-core array 16 and the diaphragm 15 changes. Usually, in the conventional sensor, the calculation for compensating for this change in distance is executed, but it has been found that if compensation with high accuracy is required, it cannot be compensated by itself.

これは、３心アレイ方式では、他の方法に比べ、３心アレイと反射面の角度変化によっても、特性が大きく変わるためである。
例えば、図７に示すように、ダイアフラム１５の変形中心と３心アレイ１６の位置がずれている場合、距離変化と共に角度変化も生じる。
また、図８に示すように、３心アレイ１６自体の角度が温度により変化してしまう場合、距離変化を補償するだけでは、温度変化による特性を完全には補償できない。 This is because the characteristics of the three-core array system are greatly changed by changing the angle between the three-core array and the reflecting surface as compared with other methods.
For example, as shown in FIG. 7, when the deformation center of the diaphragm 15 and the position of the three-core array 16 are deviated, an angle change occurs as well as a distance change.
Also, as shown in FIG. 8, when the angle of the three-core array 16 itself changes with temperature, the characteristics due to temperature change cannot be completely compensated only by compensating for the distance change.

そこで、本発明者らは、前述したような３心アレイ方式光ファイバセンサにおける温度補償に必要な要素を、距離変動（ゼロ点変動）、角度変動（スパン変動）、非線形補償の３項目に分け、それぞれの項について温度による影響を補償することで精度の高い補償を実現できることを見出した。
すなわち、本発明に係る温度補償方法では、前述したような３心アレイ方式光ファイバセンサにおいて物理量として圧力を測定する場合に、測定部又はその近傍に温度測定手段を設け、該温度測定手段で測定した温度を元に、測定部と反射部の距離が温度により変化する距離変動を補償する距離変化温度補償と、測定部と反射部の角度が温度により変化する角度変動を補償する角度変化温度補償と、測定される物理量と各受光用光ファイバで測定される光強度の強度比との関係が線形でないために生じる非線形誤差を補償する非線形温度補償とを算出し、該温度で測定された基本圧力特性から、次式（Ａ’）：
温度補償後測定圧力＝基本圧力特性−距離変化温度補償−角度変化温度補償−非線形温度補償 …（Ａ’）
によって温度補償後測定圧力を算出することを特徴としている。このように計算すると、少ないパラメータにより、精度の高い温度補償が行える。
以下に、具体的な手順を説明する。 Therefore, the present inventors divided the elements necessary for temperature compensation in the above-described three-core array type optical fiber sensor into three items of distance variation (zero point variation), angle variation (span variation), and nonlinear compensation. It was found that highly accurate compensation can be realized by compensating the influence of temperature for each term.
That is, in the temperature compensation method according to the present invention, when the pressure is measured as a physical quantity in the above-described three-core array type optical fiber sensor, a temperature measuring unit is provided at or near the measuring unit, and the temperature measuring unit measures the pressure. Based on the measured temperature, distance change temperature compensation that compensates for distance fluctuations in which the distance between the measurement part and the reflection part changes with temperature, and angle change temperature compensation that compensates for angle fluctuations in which the angle between the measurement part and the reflection part changes with temperature And a non-linear temperature compensation that compensates for a non-linear error caused by a non-linear relationship between the measured physical quantity and the intensity ratio of the light intensity measured by each light receiving optical fiber. From the pressure characteristics, the following formula (A ′):
Measured pressure after temperature compensation = basic pressure characteristics-distance change temperature compensation-angle change temperature compensation-nonlinear temperature compensation (A ')
Is used to calculate the measured pressure after temperature compensation. If calculated in this way, highly accurate temperature compensation can be performed with a small number of parameters.
A specific procedure will be described below.

１．３心アレイ方式で測定される強度比Ｆ（Ｐ１，Ｐ２）＝（Ｐ１−Ｐ２）／（Ｐ１＋Ｐ２）と圧力Ｐ_Ｔ０の関係を測定部の環境温度Ｔ_０で測定する。
２．Ｆ値と圧力Ｐ_Ｔ０の関係を表す関数ｇ（Ｆ）を求める。これが基本圧力特性となる。
Ｐ_Ｔ０＝ｇ（Ｆ） …（１）
例えば、ｇ（Ｆ）が４次関数の場合、Ｐ_Ｔ０＝ａ＋ｂ＊Ｆ^２＋ｄ＊Ｆ^３＋ｅ＊Ｆ^４
となる。ただし、ａ〜ｅは圧力換算定数を表す。
３．測定部の環境温度をＴ_ｎとし、強度比Ｆ（Ｐ１，Ｐ２）＝（Ｐ１−Ｐ２）／（Ｐ１＋Ｐ２）と圧力Ｐ_Ｔｎの関係を測定する。ここで、Ｔ_ｎはＴ_０とは異なる温度を表し、異なる温度で測定した場合ｎを増やす。
４．各温度で測定したＰ_Ｔｎと測定した全ての温度Ｔ_ｎを用い、Ｐ_Ｔｎ温度補償がなされるように、式（２）の温度補償関数、Ａ（Ｔ）、Ｂ（Ｔ），Ｃ（Ｔ）を決定する。
Ｐ（Ｔ）＝ｇ（Ｆ）−Ａ（Ｔ）−Ｂ（Ｔ）＊Ｆ−Ｃ（Ｔ）＊ｇ’（Ｆ） …（２）
ただし、ｇ’（Ｆ）は、（１）式のＦ値での１次微分であり、Ａ（Ｔ）、Ｂ（Ｔ）、Ｃ（Ｔ）は温度Ｔを変数とした関数を示す。
例えば、１次関数の場合、
Ａ（Ｔ）＝（Ａ_０＋Ａ_１Ｔ），Ｂ（Ｔ）＝（Ｂ_０＋Ｂ_１Ｔ），Ｃ（Ｔ）＝（Ｃ_０＋Ｃ_１Ｔ）
となる。ただし、Ａ_０，Ａ_１，Ｂ_０，Ｂ_１，Ｃ_０，Ｃ_１は定数であり、ここでは、温度補償定数と呼ぶ。 Intensity ratio is measured in 1.3 heart array type F (P1, P2) = measured by (P1-P2) / (P1 + P2) and the ambient temperature _{T 0} of the measuring section the relationship of the pressure _{P T0.}
2. A function g (F) representing the relationship between the F value and the pressure _PT0 is obtained. This is the basic pressure characteristic.
P _T0 = g (F) (1)
For example, when g (F) is a quartic function, P _T0 = a + b * F ² + d * F ³ + e * F ⁴
It becomes. However, ae expresses a pressure conversion constant.
3. The environmental temperature of the measuring unit and _{T n,} the intensity ratio F (P1, P2) = ( P1-P2) / (P1 + P2) and to measure the relationship between the pressure _{P Tn.} Here, T _n represents a temperature different from T _0, and n is increased when measured at a different temperature.
4). The temperature compensation function of equation (2), A (T), B (T), C (T, is used so that P _Tn temperature compensation is performed using P _Tn measured at each temperature and all measured temperatures T _n. ).
P (T) = g (F) −A (T) −B (T) * FC (T) * g ′ (F) (2)
However, g ′ (F) is a first derivative at the F value in the equation (1), and A (T), B (T), and C (T) indicate functions using the temperature T as a variable.
For example, for a linear function:
A (T) = (A ₀ + A ₁ T), B (T) = (B ₀ + B ₁ T), C (T) = (C ₀ + C ₁ T)
It becomes. However, A ₀ , A ₁ , B ₀ , B ₁ , C ₀ , C ₁ are constants, and are called temperature compensation constants here.

ここで、各項の物理的意味について考察する。式（２）において、右辺第２項は、３心アレイ１６とダイアフラム１５の距離が温度により変化することが主因であるゼロ点変動（距離変動）を補償する項であり、ここでは距離変化温度補償項と呼ぶ。また右辺第３項は、３心アレイ１６及びダイアフラム１５の相対角度が変化することが主因である特性曲線の傾き（Ｆ値スパン変動）を補償する項であり、ここでは角度変化温度補償項と呼ぶ。また右辺第４項は、圧力とＦ値の関係が線形ではないために生じる誤差を補償する項であり、ここでは非線形温度補償項と呼ぶ。このように、３心アレイ方式において距離変化、角度変化、非線形補償の３項によって数式を分けることにより、少ないデータ補償により使用する温度範囲で、精度の良い温度補償が実現できる。なお、測定温度を増やすことにより温度補償の制度を上げることも可能であり、その場合は、温度補償関数において、温度Ｔの次数を上げることで対応できる。
例えば、温度の関数を２次とした場合、（２）式は以下のようになる。
Ｐ（Ｔ）＝ｇ（Ｆ）−（Ａ_０＋Ａ_１＊Ｔ＋Ａ_２＊Ｔ^２）−（Ｂ_０＋Ｂ_１＊Ｔ＋Ｂ_２＊Ｔ^２）＊Ｆ−（Ｃ_０＋Ｃ_１＊Ｔ＋Ｃ_２＊Ｔ^２）＊ｇ’（Ｆ） Here, the physical meaning of each term is considered. In Expression (2), the second term on the right side is a term that compensates for a zero point variation (distance variation), which is mainly caused by a change in the distance between the three-core array 16 and the diaphragm 15 depending on the temperature. This is called a compensation term. The third term on the right side is a term that compensates for the slope of the characteristic curve (F value span fluctuation), which is mainly caused by the change in the relative angle between the three-core array 16 and the diaphragm 15. Here, the angle change temperature compensation term and the term Call. The fourth term on the right side is a term that compensates for an error that occurs because the relationship between the pressure and the F value is not linear, and is referred to herein as a nonlinear temperature compensation term. In this way, by dividing the mathematical expression by the three terms of distance change, angle change, and nonlinear compensation in the three-core array system, accurate temperature compensation can be realized in a temperature range used with a small amount of data compensation. It is possible to increase the temperature compensation system by increasing the measured temperature, and this case can be dealt with by increasing the order of the temperature T in the temperature compensation function.
For example, when the temperature function is quadratic, equation (2) is as follows.
P (T) = g (F) − (A ₀ + A ₁ * T + A ₂ * T ² ) − (B ₀ + B ₁ * T + B ₂ * T ² ) * F− (C ₀ + C ₁ * T + C ₂ * T ² ) * G '(F)

［光ファイバ損失補償方法］
３心アレイ方式は光強度を測定するため、光ファイバ自体の伝搬損失や、融着部での損失（以下、融着損失と記す。）などにより、光ファイバの途中で光強度が低下した場合、測定値が変化してしまう問題がある。光ファイバ自体の伝搬損失は、同じファイバを使用すればほぼ同じであり、環境温度変化による損失変動も同じ傾向を示す。３心アレイ方式では、光源から各受光部までの光ファイバ長が同じであるため、光ファイバ自体の損失は強度比をとることにより相殺され、測定値には影響を与えない。また、光ファイバの融着損失は、融着条件により異なるため、各光ファイバで異なった値となるが、融着損失の温度依存性や経年変化は小さいため、使用開始前に光ファイバ損失値の校正を行うことで、問題なく測定できる。この時、３心アレイ方式では各ファイバでの損失を個別に測定する必要はなく、一つの定数により全ての条件を補償できる。以下に詳細を説明する。 [Optical fiber loss compensation method]
Since the three-core array method measures the light intensity, the light intensity is reduced in the middle of the optical fiber due to the propagation loss of the optical fiber itself or the loss at the fusion part (hereinafter referred to as the fusion loss). There is a problem that the measured value changes. The propagation loss of the optical fiber itself is almost the same if the same fiber is used, and the loss fluctuation due to environmental temperature change shows the same tendency. In the three-core array system, since the optical fiber length from the light source to each light receiving unit is the same, the loss of the optical fiber itself is offset by taking the intensity ratio, and does not affect the measured value. In addition, the fusion loss of the optical fiber varies depending on the fusion conditions, so the value varies for each optical fiber. However, the temperature dependence and aging of the fusion loss are small, so the optical fiber loss value before the start of use is small. By calibrating, you can measure without problems. At this time, in the three-core array system, it is not necessary to individually measure the loss in each fiber, and all conditions can be compensated by one constant. Details will be described below.

図９に示すように、投光用光ファイバ２の損失がα、２本の受光用光ファイバ３，４の損失がβ_１，β_２である場合、損失がない場合の光強度をＰ１，Ｐ２とした場合、実際に測定される強度比Ｆ値は、
Ｆ＝（α β_１Ｐ１−α β_２Ｐ２）／（α β_１Ｐ１＋α β_２Ｐ２）
＝（βＰ１−Ｐ２）／（βＰ１＋Ｐ２）
と書き直すことができる。ただし、β＝β_１／β_２である。つまり、この３心アレイ方式では、３本の光ファイバにそれぞれ損失がある場合でも、一つの損失補償定数βで補償できる。このため、３本の光ファイバを使用しながら、損失補償定数が１つで良いため、補償のためのパラメータが少なくて済む。また、補償定数が一つであるため、損失補償をする際に、ある１点での校正により損失補償定数を算出することができる。つまり、３心アレイ方式を用いた温度センサの場合、ある一つの温度で３心アレイから出力されるＦ値を測定し、そのＦ値が校正温度になるように損失補償定数β_Ｔを計算する。同様に、３心アレイ方式を用いた圧力センサの場合、ある一つの圧力で３心アレイから出力されるＦ値を測定し、そのＦ値が校正圧力になるように損失補償定数β_Ｐを計算する。ここで、βの添え字ＴとＰはそれぞれ温度測定用３心アレイ方式での損失補償定数、圧力測定用３心アレイ方式での損失補償定数を示している。 As shown in FIG. 9, when the loss of the light projecting optical fiber 2 is α and the losses of the two light receiving optical fibers 3 and 4 are β ₁ and β ₂ , the light intensity when there is no loss is expressed as P1, In the case of P2, the actually measured intensity ratio F value is
F = (αβ ₁ P1−α β ₂ P2) / (α β ₁ P1 + α β ₂ P2)
= (ΒP1-P2) / (βP1 + P2)
Can be rewritten. However, β = β ₁ / β ₂ . That is, in this three-core array system, even when there are losses in the three optical fibers, it is possible to compensate with one loss compensation constant β. For this reason, since only one loss compensation constant is required while using three optical fibers, the number of parameters for compensation is small. Further, since there is one compensation constant, the loss compensation constant can be calculated by calibration at a certain point when performing loss compensation. That is, in the case of a temperature sensor using the three-core array system, the F value output from the three-core array is measured at a certain temperature, and the loss compensation constant β _T is calculated so that the F value becomes the calibration temperature. . Similarly, in the case of a pressure sensor using the three-core array method, the F value output from the three-core array is measured at a certain pressure, and the loss compensation constant β _P is calculated so that the F value becomes the calibration pressure. To do. Here, the subscripts T and P of β indicate the loss compensation constant in the three-core array system for temperature measurement and the loss compensation constant in the three-core array system for pressure measurement, respectively.

［比較例１］
図１に示す構成の３心アレイ方式光ファイバセンサを用い、その３心アレイを図６に示すようにして、４００ｋＰａ圧力により約２００μｍ変形するダイアフラムに３心アレイを対向して固定し、２０℃、５５℃、−１０℃の３温度で圧力特性を測定した。前記の３温度は、使用環境温度が−５℃〜５０℃であるため、使用温度範囲が内包されるように設定した。このような温度設定を行うことで、使用温度範囲全体に渡り精度良く温度補償できる。 [Comparative Example 1]
A three-core array type optical fiber sensor having the configuration shown in FIG. 1 is used. As shown in FIG. 6, the three-core array is fixed to a diaphragm that is deformed by about 200 μm by a pressure of 400 kPa. The pressure characteristics were measured at three temperatures of 55 ° C. and −10 ° C. The above three temperatures were set so that the use temperature range was included because the use environment temperature was −5 ° C. to 50 ° C. By performing such temperature setting, temperature compensation can be performed with high accuracy over the entire operating temperature range.

３心アレイ方式光ファイバセンサの光源としては、波長１．３μｍ帯で発光するＬＥＤを用いた。光ファイバは、使用波長でシングルモードになる、光通信で広く使用されているシングルモード光ファイバ（ＩＴＵ−ＴＧ．６５２．Ｂ相当）を使用した。 As a light source of the three-core array type optical fiber sensor, an LED that emits light in a wavelength band of 1.3 μm was used. As the optical fiber, a single mode optical fiber (corresponding to ITU-T G.652.B) widely used in optical communication, which becomes a single mode at the wavelength used, was used.

図１０に、設定圧力と測定されたＦ値の関係を示す。まず２０℃で測定したＦ値を元に基本圧力特性（１）式を求めた。ここでは、基本圧力特性の式は４次の多項式関数とした。計算により算出した圧力換算定数を表１に示す。 FIG. 10 shows the relationship between the set pressure and the measured F value. First, the basic pressure characteristic (1) equation was obtained based on the F value measured at 20 ° C. Here, the formula of the basic pressure characteristic is a fourth-order polynomial function. The pressure conversion constant calculated by calculation is shown in Table 1.

表１中の式に、−１０℃、５５℃で測定したＦ値をそのまま代入して測定圧力を演算し、測定誤差を求めた結果を図１１に示す。図１１において、横軸は設定圧力、縦軸はＦ値を元に計算した測定圧力と設定圧力との差を設定圧力の最大値で規格化した値で、ここでは測定誤差と呼ぶ。図１１に示すように、温度補償を行わない場合、基本圧力特性を測定した温度では精度の良い測定ができるが、それ以外の温度では誤差が生じ、温度変化により１％以上の測定誤差が生じることが確認できる。 FIG. 11 shows the results of calculating the measurement pressure by substituting the F values measured at −10 ° C. and 55 ° C. into the formulas in Table 1 as they are and calculating the measurement error. In FIG. 11, the horizontal axis is the set pressure, and the vertical axis is a value obtained by normalizing the difference between the measured pressure calculated based on the F value and the set pressure by the maximum value of the set pressure, and is referred to as a measurement error here. As shown in FIG. 11, when temperature compensation is not performed, accurate measurement can be performed at the temperature at which the basic pressure characteristic is measured, but an error occurs at other temperatures, and a measurement error of 1% or more occurs due to temperature change. I can confirm that.

［実施例１］
比較例１の結果を元に、各温度での測定値から温度補償関数を求め、温度補償演算を行った結果を図１２に示す。この温度補償は、測定した３温度での圧力とＦ値の関係を元に温度補償関数を予め求め、この温度補償関数を元に、式（２）に従い温度変化による特性変動を補償した。なお、温度補償関数は温度の１次式とした。使用した温度補償定数を表２に示す。なお、基本圧力特性の圧力換算定数は、比較例１と同じ値である。 [Example 1]
Based on the result of Comparative Example 1, the temperature compensation function is obtained from the measured values at each temperature, and the result of the temperature compensation calculation is shown in FIG. In this temperature compensation, a temperature compensation function is obtained in advance based on the relationship between the measured pressure and the F value at three temperatures, and the characteristic variation due to temperature change is compensated according to the equation (2) based on this temperature compensation function. The temperature compensation function is a linear equation of temperature. Table 2 shows the temperature compensation constants used. Note that the pressure conversion constant of the basic pressure characteristic is the same value as in Comparative Example 1.

この温度補償により、使用温度範囲全域に渡って±０．２％以下の高精度での測定が実現できることが確認された。 With this temperature compensation, it was confirmed that measurement with high accuracy of ± 0.2% or less can be realized over the entire operating temperature range.

前記の温度補償演算の結果を実証するべく、図１３に示す構成の温度補償型光ファイバセンサを作製し、測定圧力の温度補償を行い、その精度を確認した。本実施例で作製した温度補償型光ファイバセンサは、反射面２５を有し光ファイバ端面との相対距離が圧力に応じて変化する測定部２６（ダイアフラム）と、光源２１（ＬＥＤ）からの光を測定部２６に伝送する投光用光ファイバ２２と、測定部２６の反射面２５で反射した光を２つの受光部２７Ａ，２７Ｂにそれぞれ伝送する２本の受光用光ファイバ２３，２４と、受光部２７Ａ，２７Ｂ（フォトダイオード）で光電変換された電気信号及び測定部２６の温度測定値を元に演算して温度補償した圧力を算出する演算処理回路２９と、測定部２６に先端部を配置した熱電対３０により測定部２６の温度を測定し、測定温度値を演算処理回路２９に入力する温度測定手段３１と、予め測定した圧力換算定数、温度補償定数を記憶した不揮発性記憶媒体からなり演算処理回路２９に接続されたメモリー３２とから構成されている。３心アレイの構造は、図２及び図５に示すものと同様であり、反射面２５に対向させた３本の光ファイバ端面は、光ファイバ長手方向と反射面に対する法線とのなす角度がθとなるように固定した。使用した光源は、波長１．３μｍ帯で発光するＬＥＤを用い、また光ファイバはシングルモード光ファイバ（ＩＴＵ−ＴＧ．６５２．Ｂ相当）を使用した。 In order to verify the result of the temperature compensation calculation, a temperature compensation type optical fiber sensor having the configuration shown in FIG. 13 was manufactured, temperature compensation of the measurement pressure was performed, and the accuracy was confirmed. The temperature-compensated optical fiber sensor manufactured in this example has a measuring unit 26 (diaphragm) that has a reflecting surface 25 and a relative distance between the optical fiber end surface changes according to pressure, and light from a light source 21 (LED). A light projecting optical fiber 22 for transmitting the light to the measuring unit 26, two light receiving optical fibers 23 and 24 for transmitting the light reflected by the reflecting surface 25 of the measuring unit 26 to the two light receiving units 27A and 27B, and An arithmetic processing circuit 29 that calculates a pressure compensated by calculating based on the electrical signal photoelectrically converted by the light receiving units 27A and 27B (photodiodes) and the temperature measurement value of the measurement unit 26, and a tip portion on the measurement unit 26 The temperature of the measuring unit 26 is measured by the thermocouple 30 arranged, and the temperature measuring means 31 for inputting the measured temperature value to the arithmetic processing circuit 29, and the nonvolatile memory storing the pressure conversion constant and the temperature compensation constant measured in advance. And a memory 32 which is connected to the arithmetic processing circuit 29 consists of medium. The structure of the three-core array is the same as that shown in FIGS. 2 and 5, and the angle between the optical fiber longitudinal direction and the normal to the reflecting surface is the angle between the three optical fiber end surfaces facing the reflecting surface 25. It was fixed to be θ. The light source used was an LED that emits light with a wavelength of 1.3 μm, and the optical fiber was a single mode optical fiber (equivalent to ITU-T G.652.B).

本実施例では、測定部２６の環境温度Ｔを熱電対３０によって測定し、その温度測定値を演算処理回路２９に入力し、前述したように演算処理回路２９での演算により測定値から温度補償関数を求めた。メモリー３２には、予め測定した圧力換算定数、温度補償定数を不揮発性記憶媒体（例えばＲＯＭやＨＤＤなど）に保存してあり、演算処理回路２９において、３心アレイからのデータを元に計算されるＦ値と、熱電対３０で測定した温度Ｔを式（２）に代入し、演算処理することで、温度補償後の圧力を算出した。
図１３に示す構成の温度補償型光ファイバセンサによって温度補償後測定圧力を測定した結果、使用温度範囲全域に渡って±０．２％以下の測定精度を実現できた。 In the present embodiment, the environmental temperature T of the measuring unit 26 is measured by the thermocouple 30 and the measured temperature value is input to the arithmetic processing circuit 29, and the temperature compensation is performed from the measured value by the arithmetic processing circuit 29 as described above. I asked for a function. The memory 32 stores pre-measured pressure conversion constants and temperature compensation constants in a non-volatile storage medium (eg, ROM, HDD, etc.), and the arithmetic processing circuit 29 calculates them based on the data from the three-core array. The pressure after temperature compensation was calculated by substituting the F value and the temperature T measured by the thermocouple 30 into Equation (2) and performing arithmetic processing.
As a result of measuring the measured pressure after temperature compensation with the temperature compensated optical fiber sensor having the configuration shown in FIG. 13, a measurement accuracy of ± 0.2% or less was realized over the entire operating temperature range.

［実施例２］
実施例１では、測定部２６の温度測定を熱電対３０で行った。この場合、測定部２６の測温に電気信号が必要となるため、センサの光化の利点が半減する。そこで、実施例２では、温度測定用にも３心アレイ方式の温度センサを用いた全光方式の温度補償型光ファイバセンサを作製した。 [Example 2]
In Example 1, the temperature of the measurement unit 26 was measured with the thermocouple 30. In this case, since an electrical signal is required for temperature measurement of the measurement unit 26, the advantage of making the sensor light is halved. Therefore, in Example 2, an all-optical temperature-compensating optical fiber sensor using a three-core array type temperature sensor for temperature measurement was manufactured.

図１４は、３心アレイ方式の温度センサを例示する図であり、この温度センサは、基材３３の上にミラー３５と対向するように３心アレイ３４を接着剤３６で固定して構成され、基材３３の膨張による３心アレイとミラー間の距離変化を測定するものである。ここで用いた３心アレイ３４の基本構造は、圧力測定用の３心アレイと同じである（図２及び図５参照）。これにより、温度測定も光化できる利点がある。 FIG. 14 is a diagram illustrating a temperature sensor of a three-core array system. This temperature sensor is configured by fixing a three-core array 34 with an adhesive 36 on a base material 33 so as to face the mirror 35. The change in the distance between the three-core array and the mirror due to the expansion of the base material 33 is measured. The basic structure of the three-core array 34 used here is the same as the three-core array for pressure measurement (see FIGS. 2 and 5). Thereby, there is an advantage that the temperature measurement can be converted into light.

図１５は、この３心アレイ方式の温度センサで測定したＦ値と温度との関係を示すグラフである。図１５から分かるように、Ｆ値と温度とは直線的な関係が得られ、この関係を予め測定し、温度換算定数を求めておくことにより、３心アレイを用いた温度測定が実現できる。図１５の例では、温度換算式は、Ｔ＝１８．８７−３９５．７Ｆとなるため、温度換算定数は１８．８７と−３９５．７となる。 FIG. 15 is a graph showing the relationship between the F value measured by this three-core array type temperature sensor and the temperature. As can be seen from FIG. 15, a linear relationship is obtained between the F value and the temperature. By measuring this relationship in advance and obtaining a temperature conversion constant, temperature measurement using a three-core array can be realized. In the example of FIG. 15, since the temperature conversion formula is T = 18.87-395.7 F, the temperature conversion constants are 18.87 and −395.7.

図１６は、本実施例の全光方式の温度補償型光ファイバセンサの構成図である。この温度補償型光ファイバセンサは、反射面４５を有し光ファイバ端面との相対距離が圧力に応じて変化する圧力測定部４６（ダイアフラム）と、光源４１（ＬＥＤ）から光分岐部５６で２分割された一方の光を圧力測定部４６に伝送する投光用光ファイバ４２と、圧力測定部４６の反射面４５で反射した光を圧力測定用の２つの受光部５２Ａ，５２Ｂにそれぞれ伝送する圧力測定用の２本の受光用光ファイバ４３，４４と、光分岐部５６で２分割された他方の光を圧力測定部４６の近傍に設けられた温度測定部５１に伝送する投光用光ファイバ４７と、温度測定部５１の反射面５０で反射した光を温度測定用の２つの受光部５２Ｃ，５２Ｄにそれぞれ伝送する温度測定用の２本の受光用光ファイバ４８，４９と、４つの受光部５２Ａ〜５２Ｄ（フォトダイオード）で光電変換された電気信号を演算し、温度補償後の圧力を算出する演算処理回路５４と、予め測定した圧力換算定数、温度補償定数を記憶した不揮発性記憶媒体からなり演算処理回路５４に接続されたメモリー５５とから構成されている。圧力測定用及び温度測定用の３心アレイの構造は、図２及び図５に示すものと同様であり、反射面に対向させた３本の光ファイバ端面は、光ファイバ長手方向と反射面に対する法線とのなす角度がθとなるように固定した。使用した光源４１は、波長１．３μｍ帯で発光するＬＥＤを用い、また光ファイバはシングルモード光ファイバ（ＩＴＵ−ＴＧ．６５２．Ｂ相当）を使用した。 FIG. 16 is a configuration diagram of an all-optical temperature-compensating optical fiber sensor according to the present embodiment. This temperature-compensated optical fiber sensor includes a pressure measuring unit 46 (diaphragm) having a reflecting surface 45 and a relative distance between the optical fiber end surface and a light branching unit 56 from the light source 41 (LED). The light projecting optical fiber 42 that transmits the divided light to the pressure measurement unit 46 and the light reflected by the reflection surface 45 of the pressure measurement unit 46 are transmitted to the two light receiving units 52A and 52B for pressure measurement, respectively. Two light receiving optical fibers 43 and 44 for pressure measurement and the other light divided into two by the light branching unit 56 are transmitted to a temperature measuring unit 51 provided in the vicinity of the pressure measuring unit 46. Two light receiving optical fibers 48 and 49 for temperature measurement that transmit the light reflected by the reflection surface 50 of the fiber 47 and the temperature measuring unit 51 to the two light receiving units 52C and 52D for temperature measurement, respectively, and four Light receiving parts 52A-52 An arithmetic processing circuit 54 that calculates an electric signal photoelectrically converted by a (photodiode) and calculates a pressure after temperature compensation, and a nonvolatile storage medium that stores a pressure conversion constant and a temperature compensation constant measured in advance. The memory 55 is connected to the circuit 54. The structure of the three-core array for pressure measurement and temperature measurement is the same as that shown in FIGS. 2 and 5, and the three optical fiber end faces opposed to the reflection surface are in the optical fiber longitudinal direction and the reflection surface. The angle between the normal and the normal was fixed to θ. The light source 41 used was an LED that emits light in a wavelength band of 1.3 μm, and a single-mode optical fiber (equivalent to ITU-T G.652.B) was used as the optical fiber.

メモリー５５には、予め測定した圧力換算定数、温度補償定数、温度換算定数を不揮発性記憶媒体（例えばＲＯＭやＨＤＤなど）に保存してあり、演算処理回路５４では、温度測定用３心アレイから計算されるＦ値を元に温度換算定数を用いて計算される温度と、圧力測定部４６の３心アレイから計算されるＦ値を式（２）に代入して温度補償後の圧力を計算している。これにより、全光型の温度補償圧力測定が実現でき、実施例１と同様に使用温度範囲全域に渡って±０．２％以下の測定精度を実現できた。 The memory 55 stores pre-measured pressure conversion constants, temperature compensation constants, and temperature conversion constants in a non-volatile storage medium (for example, ROM, HDD, etc.). Calculate the pressure after temperature compensation by substituting the temperature calculated using the temperature conversion constant based on the calculated F value and the F value calculated from the three-core array of the pressure measuring unit 46 into Equation (2). is doing. As a result, all-optical temperature-compensated pressure measurement can be realized, and measurement accuracy of ± 0.2% or less can be realized over the entire operating temperature range as in Example 1.

［実施例３］
実施例３では、融着部などによる損失補償の方法について示す。本実施例では、実施例２と同様に、温度測定用にも３心アレイ方式の温度センサを用いた全光方式の温度補償型光ファイバセンサを作製した。
図１７は、本実施例の全光方式の温度補償型光ファイバセンサの構成図である。この温度補償型光ファイバセンサは、反射面６５を有し光ファイバ端面との相対距離が圧力に応じて変化する圧力測定部６６（ダイアフラム）と、光源６１（ＬＥＤ）から光分岐部７６で２分割された一方の光を圧力測定部６６に伝送する投光用光ファイバ６２と、圧力測定部６６の反射面６５で反射した光を圧力測定用の２つの受光部７２Ａ，７２Ｂにそれぞれ伝送する圧力測定用の２本の受光用光ファイバ６３，６４と、光分岐部７６で２分割された他方の光を圧力測定部６６の近傍に設けられた温度測定部７１に伝送する投光用光ファイバ６７と、温度測定部７１の反射面７０で反射した光を温度測定用の２つの受光部７２Ｃ，７２Ｄにそれぞれ伝送する温度測定用の２本の受光用光ファイバ６８，６９と、４つの受光部７２Ａ〜７２Ｄ（フォトダイオード）で光電変換された電気信号を演算し、温度補償後の圧力を算出する演算処理回路７４と、予め測定した圧力換算定数、温度補償定数を記憶した不揮発性記憶媒体を有し演算処理回路７４に接続されたメモリー７５とから構成されている。圧力測定用及び温度測定用３心アレイの構造は、図２及び図５に示すものと同様であり、反射面に対向させた３本の光ファイバ端面は、光ファイバ長手方向と反射面に対する法線とのなす角度がθとなるように固定した。使用した光源６１は、波長１．３μｍ帯で発光するＬＥＤを用い、また光ファイバはシングルモード光ファイバ（ＩＴＵ−ＴＧ．６５２．Ｂ相当）を使用した。 [Example 3]
In the third embodiment, a loss compensation method using a fused portion or the like will be described. In this example, as in Example 2, an all-optical temperature-compensating optical fiber sensor using a three-core array type temperature sensor for temperature measurement was produced.
FIG. 17 is a configuration diagram of an all-optical temperature-compensating optical fiber sensor according to the present embodiment. This temperature-compensated optical fiber sensor includes a pressure measuring unit 66 (diaphragm) having a reflecting surface 65 and a relative distance between the optical fiber end surface and a light branching unit 76 from the light source 61 (LED). The light projecting optical fiber 62 that transmits the divided light to the pressure measuring unit 66 and the light reflected by the reflecting surface 65 of the pressure measuring unit 66 are transmitted to the two light receiving units 72A and 72B for pressure measurement, respectively. Two light receiving optical fibers 63 and 64 for pressure measurement and the other light divided into two by the light branching portion 76 are transmitted to a temperature measuring portion 71 provided in the vicinity of the pressure measuring portion 66. Two light receiving optical fibers 68 and 69 for temperature measurement that transmit the light reflected by the reflection surface 70 of the temperature 67 to the two light receiving portions 72C and 72D for temperature measurement, respectively, and four fibers Light receivers 72A-72 An arithmetic processing circuit 74 that calculates an electric signal photoelectrically converted by a (photodiode) and calculates a pressure after temperature compensation, and a non-volatile storage medium that stores a pressure conversion constant and a temperature compensation constant measured in advance. The memory 75 is connected to the processing circuit 74. The structure of the three-core array for pressure measurement and temperature measurement is the same as that shown in FIG. 2 and FIG. 5, and the three optical fiber end faces opposed to the reflection surface are a method for the optical fiber longitudinal direction and the reflection surface. The angle formed with the line was fixed to be θ. The light source 61 used was an LED that emits light in a wavelength band of 1.3 μm, and the optical fiber was a single mode optical fiber (equivalent to ITU-T G.652.B).

実施例２と同様に、予め、圧力測定用、温度測定用３心アレイの特性を評価し、圧力換算定数、温度補償定数、温度換算定数を求めておき、演算処理回路７４のメモリー７５に保存しておく。ついで、温度測定用３心アレイ及び圧力測定用３心アレイを光強度測定用の光源６１及び受光部（フォトダイオード）７２Ａ〜７２Ｄに接続する。ついで、温度測定部７１の温度を熱電対などで測定し、その温度を演算処理回路７４に入力する。演算処理回路７４では、温度測定用の３心アレイの損失補償係数β_Ｔを変えながら、温度換算定数から求められる温度と、入力された温度との差を計算し、その差が規定の値以下になるようにβ_Ｔを決定する。決定されたβ_Ｔは演算処理回路７４のメモリー７５に保存され、それ以降の温度計算の際に使用する。ここで、β_Ｔは、温度測定用３心アレイの光ファイバ損失を補償する損失補償定数である。これにより、温度測定用センサの損失補償が完了する。 As in the second embodiment, the characteristics of the three-core array for pressure measurement and temperature measurement are evaluated in advance, and the pressure conversion constant, temperature compensation constant, and temperature conversion constant are obtained and stored in the memory 75 of the arithmetic processing circuit 74. Keep it. Next, the temperature measuring three-core array and the pressure measuring three-core array are connected to the light intensity measuring light source 61 and the light receiving portions (photodiodes) 72A to 72D. Next, the temperature of the temperature measuring unit 71 is measured with a thermocouple or the like, and the temperature is input to the arithmetic processing circuit 74. The arithmetic processing circuit 74, while changing the loss compensation factor beta _T of 3 heart arrays for temperature measurement, the temperature determined from the temperature conversion constant, compute the difference between the input temperature, less the difference is defined value Β _T is determined so that Determined beta _T is stored in the memory 75 of the arithmetic processing circuit 74, for use in the subsequent temperature calculations. Here, β _T is a loss compensation constant for compensating for the optical fiber loss of the temperature measuring three-core array. Thereby, the loss compensation of the temperature measuring sensor is completed.

同様に、圧力測定用３心アレイの損失補償を行う。圧力測定用３心アレイの損失補償では、校正する圧力（通常は０ｋＰａ）を圧力測定部６６のダイアフラムにかけ、その時の測定圧力を演算する。この時、温度測定用３心アレイで測定した温度Ｔと設定圧力を式（２）に代入し、設定圧力と測定圧力の差が既定値以下になるように圧力測定用３心アレイの損失係数β_Ｐを決定する。決定されたβ_Ｐは、演算処理回路７４のメモリー７５に保存され、それ以降の圧力計算の際に使用する。ここで、β_Ｐは、圧力測定用３心アレイの光ファイバ損失を補償する損失補償定数である。これにより、圧力測定用センサの損失補償が完了する。 Similarly, loss compensation is performed for the three-core array for pressure measurement. In the loss compensation of the pressure measuring three-core array, the pressure to be calibrated (usually 0 kPa) is applied to the diaphragm of the pressure measuring unit 66, and the measured pressure at that time is calculated. At this time, the temperature T measured with the three-core array for temperature measurement and the set pressure are substituted into Equation (2), and the loss factor of the three-core array for pressure measurement is set so that the difference between the set pressure and the measured pressure is not more than the predetermined value. β _P is determined. The determined β _P is stored in the memory 75 of the arithmetic processing circuit 74 and is used for subsequent pressure calculations. Here, β _P is a loss compensation constant for compensating for the optical fiber loss of the three-core array for pressure measurement. Thereby, the loss compensation of the pressure measuring sensor is completed.

その後の計算は実施例２と同様に行う。本実施例では、温度測定用及び圧力測定用３心アレイの損失補償定数を予め求めておき、測定圧力の演算時にこれを補償した値を出力することで、光ファイバ経路に損失がある場合でも、±０．２％以下の測定精度を実現できた。 Subsequent calculations are performed in the same manner as in Example 2. In this embodiment, the loss compensation constants of the temperature measurement and pressure measurement three-core arrays are obtained in advance, and a value compensated for this is output when calculating the measurement pressure, so that even if there is a loss in the optical fiber path. Measurement accuracy of ± 0.2% or less was achieved.

３心アレイ方式光ファイバセンサの基本構成を例示する構成図である。It is a block diagram which illustrates the basic composition of a 3 core array type optical fiber sensor. 図１の３心アレイ方式光ファイバセンサにおける測定部の拡大図である。FIG. 2 is an enlarged view of a measurement unit in the three-core array type optical fiber sensor of FIG. 1. 図１に示す３心アレイ方式光ファイバセンサでの測定結果を例示するグラフである。It is a graph which illustrates the measurement result in the 3 core array type optical fiber sensor shown in FIG. 図１に示す３心アレイ方式光ファイバセンサにおいて３心アレイの固定角度θを種々変更した場合の測定結果を例示するグラフである。3 is a graph illustrating measurement results when various changes are made to the fixed angle θ of the three-core array in the three-core array type optical fiber sensor shown in FIG. 1. 図２中のＡ−Ａ’部断面図である。FIG. 3 is a cross-sectional view taken along line A-A ′ in FIG. 2. ダイアフラムを用いた圧力測定の３心アレイ配置状態を例示する側面断面図である。It is side surface sectional drawing which illustrates the 3-core array arrangement | positioning state of the pressure measurement using a diaphragm. ダイアフラム中心線と３心アレイがずれている場合を例示する側面断面図である。It is side surface sectional drawing which illustrates the case where the diaphragm centerline and the 3 core array have shifted | deviated. ダイアフラム中心線に対して３心アレイが傾いた場合を例示する側面断面図である。It is side surface sectional drawing which illustrates the case where a 3 core array inclines with respect to a diaphragm centerline. ３心アレイ方式光ファイバセンサの光ファイバに損失がある場合を示す構成図である。It is a block diagram which shows the case where there exists a loss in the optical fiber of a 3 core array system optical fiber sensor. ３心アレイ方式光ファイバセンサの圧力測定結果を例示するグラフである。It is a graph which illustrates the pressure measurement result of a 3 core array system optical fiber sensor. 比較例１において温度補償をしない場合の圧力測定誤差の変動を示すグラフである。6 is a graph showing fluctuations in pressure measurement error when temperature compensation is not performed in Comparative Example 1; 実施例１において温度補償をした場合の圧力測定誤差の変動を示すグラフである。4 is a graph showing fluctuations in pressure measurement error when temperature compensation is performed in Example 1. 実施例１で作製した温度補償型光ファイバセンサの構成図である。1 is a configuration diagram of a temperature-compensated optical fiber sensor manufactured in Example 1. FIG. 実施例２で作製した３心アレイ方式の温度センサを示す側面図である。5 is a side view showing a three-core array type temperature sensor manufactured in Example 2. FIG. 実施例２で作製した３心アレイ方式の温度センサを用いた温度測定結果を示すグラフである。6 is a graph showing a temperature measurement result using a three-core array type temperature sensor manufactured in Example 2. FIG. 実施例２で作製した温度補償型光ファイバセンサの構成図である。6 is a configuration diagram of a temperature-compensating optical fiber sensor manufactured in Example 2. FIG. 実施例３で作製した温度補償型光ファイバセンサの構成図である。6 is a configuration diagram of a temperature compensated optical fiber sensor manufactured in Example 3. FIG.

符号の説明Explanation of symbols

１，２１，４１，６１…光源、２，２２，４２，４７，６２，６７…投光用光ファイバ、３，４，２３，２４，４３，４４，４８，４９、６３，６４，６８，６９…受光用光ファイバ、５，２５，４５，６５，５０，７０…反射面、５Ａ…反射板、６，２６…測定部、７Ａ，７Ｂ，２７Ａ，２７Ｂ，５２Ａ，５２Ｂ，５２Ｃ，５２Ｄ，７２Ａ，７２Ｂ，７２Ｃ，７２Ｄ…受光部、９，２９，５４，７４…演算処理回路、１０Ａ，１０Ｂ，１０Ｃ…光ファイバ、１１Ａ，１１Ｂ，１１Ｃ…コア、１２…Ｖ溝アレイ基板、１３…光ファイバ押え蓋、１４…筒部、１５…ダイアフラム、１６…３心アレイ、３０…熱電対、３１…温度測定手段、３２，５５，７５…メモリー、３３…基材、３４…３心アレイ、３５…ミラー、４６，６６…圧力測定部、５１，７１…温度測定部、５６，７６…光分岐部。 1, 2, 41, 61... Light source, 2, 22, 42, 47, 62, 67 .. projecting optical fiber, 3, 4, 23, 24, 43, 44, 48, 49, 63, 64, 68, 69 ... Optical fiber for light reception, 5, 25, 45, 65, 50, 70 ... Reflecting surface, 5A ... Reflecting plate, 6, 26 ... Measuring section, 7A, 7B, 27A, 27B, 52A, 52B, 52C, 52D, 72A, 72B, 72C, 72D ... light receiving unit, 9, 29, 54, 74 ... arithmetic processing circuit, 10A, 10B, 10C ... optical fiber, 11A, 11B, 11C ... core, 12 ... V groove array substrate, 13 ... light Fiber holding lid, 14 ... cylindrical portion, 15 ... diaphragm, 16 ... 3-core array, 30 ... thermocouple, 31 ... temperature measuring means, 32, 55, 75 ... memory, 33 ... base material, 34 ... 3-core array, 35 ... Mirror, 46, 66 ... Pressure measuring part 51, 71 ... the temperature measuring unit, 56, 76 ... light branching unit.

Claims

光源と、反射面を有し光ファイバ端面との相対距離が物理量に応じて変化する測定部と、光源からの光を測定部に伝送する投光用光ファイバと、測定部反射面で反射した光を複数の受光部にそれぞれ伝送する複数本の受光用光ファイバと、受光部からの電気信号の比から前記物理量を算出する演算処理回路とを有する光ファイバセンサを用いた物理量測定における物理量の温度補償方法であって、
測定部又はその近傍に温度測定手段を設け、該温度測定手段で測定した温度を元に、
測定部と反射部の距離が温度により変化する距離変動を補償する距離変化温度補償と、測定部と反射部の角度が温度により変化する角度変動を補償する角度変化温度補償と、測定される物理量と各受光用光ファイバで測定される光強度の強度比との関係が線形でないために生じる非線形誤差を補償する非線形温度補償とを算出し、
該温度で測定された基本物理量特性から、次式（Ａ）：
温度補償後測定物理量＝基本物理量特性−距離変化温度補償−角度変化温度補償−非線形温度補償 …（Ａ）
によって温度補償後測定物理量を算出することを特徴とする物理量の温度補償方法。 A measurement unit in which the relative distance between the light source and the reflection surface and the end face of the optical fiber changes according to the physical quantity, a light projecting optical fiber that transmits light from the light source to the measurement unit, and a reflection by the measurement unit reflection surface A physical quantity in a physical quantity measurement using an optical fiber sensor having a plurality of light receiving optical fibers that respectively transmit light to a plurality of light receiving sections, and an arithmetic processing circuit that calculates the physical quantity from a ratio of electrical signals from the light receiving sections. A temperature compensation method comprising:
Based on the temperature measured by the temperature measuring means provided in the measuring part or its vicinity,
Distance variation temperature compensation that compensates for the distance variation in which the distance between the measurement unit and the reflection unit varies with temperature, angle variation temperature compensation that compensates for the angle variation in which the angle between the measurement unit and the reflection unit varies with temperature, and the physical quantity to be measured And non-linear temperature compensation that compensates for non-linear errors caused by the non-linear relationship between the intensity ratio of the light intensity measured by each light receiving optical fiber,
From the basic physical quantity characteristics measured at the temperature, the following formula (A):
Measurement physical quantity after temperature compensation = basic physical quantity characteristics-distance change temperature compensation-angle change temperature compensation-nonlinear temperature compensation (A)
A temperature compensation method for a physical quantity, characterized in that a measured physical quantity after temperature compensation is calculated by:

以下の手順：
１．各受光用ファイバで測定される光強度（Ｐ１，Ｐ２）の強度比Ｆ（Ｐ１，Ｐ２）＝（Ｐ１−Ｐ２）／（Ｐ１＋Ｐ２）と物理量Ｐ_Ｔ０の関係を測定部の環境温度Ｔ_０で測定し、
２．Ｆ値と物理量Ｐ_Ｔ０の関係を表す関数ｇ（Ｆ）を求め、これを基本物理量特性とし、
Ｐ_Ｔ０＝ｇ（Ｆ） …（１）
３．測定部の異なる環境温度をＴ_ｎとし、強度比Ｆ（Ｐ１，Ｐ２）＝（Ｐ１−Ｐ２）／（Ｐ１＋Ｐ２）と物理量Ｐ_Ｔｎの関係を測定し、
４．各温度で測定した物理量Ｐ_Ｔｎと測定した全ての温度Ｔ_ｎを用い、Ｐ_Ｔｎ温度補償がなされるように、式（２）の温度補償関数、Ａ（Ｔ）、Ｂ（Ｔ），Ｃ（Ｔ）を決定すること、
Ｐ（Ｔ）＝ｇ（Ｆ）−Ａ（Ｔ）−Ｂ（Ｔ）＊Ｆ−Ｃ（Ｔ）＊ｇ’（Ｆ） …（２）
（式中、ｇ’（Ｆ）は（１）式のＦ値での１次微分であり、Ａ（Ｔ）、Ｂ（Ｔ）、Ｃ（Ｔ）は温度Ｔを変数とした関数であり、右辺第２項は距離変化温度補償項、右辺第３項は角度変化温度補償項、右辺第４項は非線形温度補償をそれぞれ表す。）
によって温度補償後測定物理量を算出することを特徴とする請求項１に記載の物理量の温度補償方法。 The following steps:
1. Intensity ratio F of the light intensity measured by the light receiving fiber (P1, P2) (P1, P2) = (P1-P2) / (P1 + P2) and measured at ambient temperature _{T 0} of the measuring section the relationship of the physical quantity _{P T0} And
2. A function g (F) representing the relationship between the F value and the physical quantity _PT0 is obtained, and this is used as a basic physical quantity characteristic.
P _T0 = g (F) (1)
3. The environmental temperature of different measuring unit and _{T n,} the intensity ratio F (P1, P2) = ( P1-P2) / (P1 + P2) and to measure the relationship between the physical quantity _{P Tn,}
4). Using all temperature _{T n} and the measured physical quantity _{P Tn} measured at each _temperature, as _{P Tn} temperature compensation is made, the temperature compensation function of equation (2), A (T) , B (T), C ( T),
P (T) = g (F) −A (T) −B (T) * FC (T) * g ′ (F) (2)
(In the formula, g ′ (F) is a first derivative at the F value of the formula (1), A (T), B (T), C (T) are functions with the temperature T as a variable, (The second term on the right side represents the distance change temperature compensation term, the third term on the right side represents the angle change temperature compensation term, and the fourth term on the right side represents the nonlinear temperature compensation.)
The temperature compensation method for a physical quantity according to claim 1, wherein the measured physical quantity after temperature compensation is calculated by:

受光用光ファイバの損失（β_１，β_２）を測定し、損失補償定数β（ただし、β＝β_１／β_２）を算出し、この損失補償定数βで測定物理量を更に補償することを特徴とする請求項１又は２に記載の物理量の温度補償方法。 The loss (β ₁ , β ₂ ) of the optical fiber for light reception is measured, the loss compensation constant β (where β = β ₁ / β ₂ ) is calculated, and the measured physical quantity is further compensated with this loss compensation constant β. 3. The physical quantity temperature compensation method according to claim 1, wherein the physical quantity is compensated by temperature.

測定する物理量が圧力であることを特徴とする請求項１〜３のいずれかに記載の物理量の温度補償方法。 The physical quantity temperature compensation method according to claim 1, wherein the physical quantity to be measured is pressure.

光源と、反射面を有し光ファイバ端面との相対距離が圧力や温度などの物理量に応じて変化する測定部と、光源からの光を測定部に伝送する投光用光ファイバと、測定部反射面で反射した光を複数の受光部にそれぞれ伝送する複数本の受光用光ファイバと、受光部からの電気信号の比から前記物理量を算出する演算処理回路とを有する光ファイバセンサであって、
測定部又はその近傍に温度測定手段が設けられ、
演算処理回路は、該温度測定手段で測定した温度を元に、請求項１〜４のいずれかに記載の物理量の温度補償方法を実行し、温度補償後測定物理量を算出するプログラムを有していることを特徴とする温度補償型光ファイバセンサ。 A measuring unit in which the relative distance between the light source and the end surface of the optical fiber having a reflecting surface changes according to a physical quantity such as pressure and temperature, a light projecting optical fiber that transmits light from the light source to the measuring unit, and a measuring unit An optical fiber sensor comprising: a plurality of light receiving optical fibers that respectively transmit light reflected by a reflecting surface to a plurality of light receiving units; and an arithmetic processing circuit that calculates the physical quantity from a ratio of electrical signals from the light receiving units. ,
A temperature measuring means is provided at or near the measuring unit,
The arithmetic processing circuit has a program for executing the physical quantity temperature compensation method according to any one of claims 1 to 4 based on the temperature measured by the temperature measuring means, and calculating the measured physical quantity after temperature compensation. A temperature-compensated optical fiber sensor.

投光用光ファイバと２本の受光用光ファイバとのそれぞれの先端部が、反射面に対する法線を基準として固定角度θで対称に固定された３心アレイ構造を有していることを特徴とする請求項５に記載の温度補償型光ファイバセンサ。 Each of the tip ends of the light projecting optical fiber and the two light receiving optical fibers has a three-core array structure that is fixed symmetrically at a fixed angle θ with respect to the normal to the reflecting surface. The temperature-compensated optical fiber sensor according to claim 5.

温度測定手段が前記３心アレイ構造を有する光ファイバセンサであることを特徴とする請求項６に記載の温度補償型光ファイバセンサ。 The temperature compensating optical fiber sensor according to claim 6, wherein the temperature measuring means is an optical fiber sensor having the three-core array structure.

予め測定した物理量換算定数、温度補償定数及び温度換算定数を記録しておく不揮発性記憶媒体を演算処理回路に接続したことを特徴とする請求項５〜７のいずれかに記載の温度補償型光ファイバセンサ。 8. The temperature-compensated light according to claim 5, wherein a nonvolatile storage medium that records physical quantity conversion constants, temperature compensation constants, and temperature conversion constants measured in advance is connected to an arithmetic processing circuit. Fiber sensor.