JP3145798B2 - Optical magnetic field sensor and magnetic field measuring device - Google Patents
Optical magnetic field sensor and magnetic field measuring deviceInfo
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- JP3145798B2 JP3145798B2 JP21742992A JP21742992A JP3145798B2 JP 3145798 B2 JP3145798 B2 JP 3145798B2 JP 21742992 A JP21742992 A JP 21742992A JP 21742992 A JP21742992 A JP 21742992A JP 3145798 B2 JP3145798 B2 JP 3145798B2
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- Japan
- Prior art keywords
- optical
- magnetic field
- optical fiber
- light
- field sensor
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Description
【０００１】[0001]
【産業上の利用分野】本発明は光磁界センサに関し、特
に、複数箇所の磁界を同時に測定できる光磁界センサに
関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical magnetic field sensor, and more particularly to an optical magnetic field sensor capable of simultaneously measuring magnetic fields at a plurality of locations.
【０００２】[0002]
【従来の技術】光磁界センサは従来から伝送線の電流測
定等に広く使用されている。図５に示したように、光磁
界センサは、磁気光学素子１、光ファイバ２、２’、コ
リメータレンズ３、３’、偏光子７、検光子８から構成
されている。光ファイバ２から出射した光はコリメータ
レンズ３により平行ビームとなり、偏光子７を透過し、
直線偏光となる。磁気光学素子１に磁界が印加されると
ファラディー効果によりこの直線偏光の偏光面が磁界の
強度に比例して回転する。この光が検光子３を透過する
と偏光面の角度により光量が変化し、コリメータレンズ
３’により光ファイバ２’へ集光される。このようにし
て、磁界の大きさが光量に変換される。2. Description of the Related Art Optical magnetic field sensors have been widely used for measuring the current of transmission lines. As shown in FIG. 5, the optical magnetic field sensor includes a magneto-optical element 1, optical fibers 2, 2 ', collimator lenses 3, 3', a polarizer 7, and an analyzer 8. The light emitted from the optical fiber 2 is converted into a parallel beam by the collimator lens 3, passes through the polarizer 7,
It becomes linearly polarized light. When a magnetic field is applied to the magneto-optical element 1, the plane of polarization of the linearly polarized light rotates in proportion to the strength of the magnetic field due to the Faraday effect. When this light passes through the analyzer 3, the amount of light changes depending on the angle of the plane of polarization, and is condensed on the optical fiber 2 'by the collimator lens 3'. In this way, the magnitude of the magnetic field is converted into a light amount.
【０００３】上記の光磁界センサは偏光子と検光子を使
用する必要があり、構造が複雑であるので、これらを省
略した光磁界センサが特願平３−２８１７３８号、及び
特願平４−８１３９８号により提案されている。図６に
示したように、図５から偏光子７と検光子８を省略し、
磁気光学素子１として多磁区構造を有し、且つ磁界を印
加しない時に光の進行方向に平行な磁化成分が隣接する
磁区で互いに逆方向になるような材料を使用する。外部
磁界が加わると磁気光学素子１は磁壁が移動し、磁区が
大きくなるので回折損失が減少し、飽和すると回折損失
は生じなくなる。透過率は印加磁界の強さに依存するの
で透過率を測定すれば磁界強度が検出できる。なお、図
６の透過型の代わりに図７のように反射鏡４を設け、出
射光ファイバ２’を入射側に配置した反射型光磁界セン
サを用いることもある。光が２度磁気光学素子を透過す
る以外は同じ原理による。The above-mentioned optical magnetic field sensor requires the use of a polarizer and an analyzer, and has a complicated structure. Therefore, an optical magnetic field sensor in which these elements are omitted is disclosed in Japanese Patent Application Nos. 3-28138 and 3-28138. No. 81398. As shown in FIG. 6, the polarizer 7 and the analyzer 8 are omitted from FIG.
The magneto-optical element 1 is made of a material having a multi-domain structure and in which, when a magnetic field is not applied, the magnetization components parallel to the traveling direction of light are in opposite directions in adjacent magnetic domains. When an external magnetic field is applied, the domain wall of the magneto-optical element 1 moves, and the magnetic domain becomes large, so that the diffraction loss is reduced. Since the transmittance depends on the strength of the applied magnetic field, the magnetic field strength can be detected by measuring the transmittance. In addition, instead of the transmission type of FIG. 6, a reflection type optical magnetic field sensor in which the reflection mirror 4 is provided as shown in FIG. The same principle is used except that the light passes through the magneto-optical element twice.
【０００４】[0004]
【発明が解決しようとする課題】従来の透過式または反
射式の光磁界センサは単一機能を有するに過ぎないので
他の機能を同時に果たすことはできない。例えば、光通
信において伝送を中断することなく磁界を測定したい場
合とか、同時に多数点の磁界を測定したい場合とかの場
合には、別々の測定装置を設ける必要がある。The conventional transmission or reflection type optical magnetic field sensor has only a single function and cannot perform other functions at the same time. For example, when it is desired to measure a magnetic field without interrupting transmission in optical communication or when it is desired to measure magnetic fields at many points at the same time, it is necessary to provide a separate measuring device.
【０００５】[0005]
【課題を解決するための手段】本発明は、磁気光学素子
の透過損失が反射して再透過する場合の損失に比べて著
しく少ないことを利用して、反射光を磁界検知に使用
し、透過光を光通信とか他の同様な反射光による磁界検
知に利用する。すなわち、本発明の光磁界センサは、入
射用の第１光ファイバと、透過光出射用の第２光ファイ
バと、反射光出射用の第３光ファイバと、多磁区構造を
有し且つ磁界を印加しない時に光の進行方向に平行な磁
化成分が隣接する磁区で互いに逆方向になるような材料
より製作した磁気光学素子と、反射面とより構成され
る。第１光ファイバからの光は磁気光学素子を透過し、
その一部は透過光出射用の第２光ファイバに集束され
る。他の一部は反射面により反射されて磁気光学素子を
再度透過し、反射光出射用の第３光ファイバへ集束され
る。なお、反射光出射用の第３光ファイバは入射用の第
１光ファイバで兼用しても良い。また、二か所以上の磁
界を測定したい場合には、透過光を更に同一の構成の光
磁界センサに送ってその反射光を別々の受光素子に、ま
たは光スイッチを介して同一の受光素子に受けても良
い。以下に実施例により本発明を詳しく説明する。The present invention utilizes the reflected light for detecting a magnetic field by utilizing the fact that the transmission loss of a magneto-optical element is significantly smaller than the loss caused by reflection and retransmission. Light is used for optical communication or other similar reflected light magnetic field sensing. That is, the optical magnetic field sensor according to the present invention has a first optical fiber for incidence, a second optical fiber for emitting transmitted light, a third optical fiber for emitting reflected light, a multi-domain structure, and a magnetic field. It is composed of a magneto-optical element made of a material in which the magnetization components parallel to the light traveling direction are in opposite directions in adjacent magnetic domains when no voltage is applied, and a reflective surface. Light from the first optical fiber passes through the magneto-optical element,
A part thereof is focused on the second optical fiber for transmitting transmitted light. The other part is reflected by the reflecting surface, passes through the magneto-optical element again, and is focused on the third optical fiber for emitting the reflected light. The third optical fiber for emitting the reflected light may be used also as the first optical fiber for incidence. When it is desired to measure magnetic fields at two or more locations, the transmitted light is further sent to an optical magnetic field sensor having the same configuration, and the reflected light is sent to a separate light receiving element or to the same light receiving element via an optical switch. You may take it. Hereinafter, the present invention will be described in detail with reference to examples.
【０００６】[0006]
【作用】特願平３−２８１７３８号に記載されているよ
うに、多磁区構造を有する光学素子は回折損失を生じ、
この回折損失は磁界により変化する。この回折損失は次
の近似式で表される。 透過の際の回折損失（単位ｄＢ） Lt=-10log10 (cos2 θf ＋（H ／HS) sin2θf ） (1) 反射の際の回折損失（単位ｄＢ） Lr=-10log10 (cos2( 2θf)＋（H ／HS) sin2(2θf)）(2) ここに、Ｈは磁気光学素子に印加される磁界（絶対
値）、ＨS は飽和磁界であり、Ｈ≦ＨS である。Ｈ≧Ｈ
S では回折損失は零である。θf は飽和時のファラデー
回転角である。上の２式より、例えばＨ＝０、θf ＝３
０°の場合、Ｌｔ＝１．２５ｄＢＬｒ＝６．０２ｄＢと
なり、反射の際の回折損失は透過の際の回折損失より非
常に大きいことが分かる。As described in Japanese Patent Application No. 3-28138, an optical element having a multi-domain structure causes diffraction loss,
This diffraction loss changes with the magnetic field. This diffraction loss is represented by the following approximate expression. Diffraction loss at the time of transmission (unit: dB) Lt = −10 log 10 (cos 2 θ f + (H / H S ) sin 2 θ f ) (1) Diffraction loss at the time of reflection (unit: dB) Lr = −10 log 10 (cos 2 (2θ f ) + (H / H S ) sin 2 (2θ f )) (2) where H is a magnetic field (absolute value) applied to the magneto-optical element, H S is a saturation magnetic field, is H ≦ H S. H ≧ H
At S , the diffraction loss is zero. θ f is the Faraday rotation angle at the time of saturation. From the above two equations, for example, H = 0, θ f = 3
In the case of 0 °, Lt = 1.25 dBLr = 6.02 dB, which indicates that the diffraction loss at the time of reflection is much larger than the diffraction loss at the time of transmission.
【０００７】[0007]
実施例１ 図１は本発明の光磁界センサの実施例を示す。光磁界セ
ンサは入射用の第１光ファイバ１０、出射用の第２光フ
ァイバ１２を有し、それらの間にコリメータレンズ１
６、１８を有し、更にこれらのレンズ１６、１８の間に
磁気光学素子２０を有する。磁気光学素子２０は先に述
べたように多磁区構造を有し且つ磁界を印加しない時に
光の進行方向に平行な磁化成分が隣接する磁区で互いに
逆方向になるような材料より製作されていて、測定すべ
き磁界内に配置される。磁気光学素子２０の出射側の面
は磁気光学素子と空気の屈折率との差により入射光に対
する反射面２２となる。別法として、反射面は誘電体多
層膜により所定の反射率となるように作製しても良い。
更に、レンズ１３の入射側には反射光を受けて受光素子
へ導くための第３光ファイバ１４が配置されている。磁
気光学素子２０の入射側の面、レンズ１６、１８の両
面、光ファイバ１０、１２の端面には、反射を防ぐため
の公知の手段を施す。例えば反射防止膜を施すとか、光
ファイバを斜めに切断するとか、光ファイバとレンズを
接着するとかの対策を行う。第１光ファイバ１０から出
射した光はレンズ１６により平行光となり磁気光学素子
２０を透過し、一部はそのままレンズ１８により第２光
ファイバ１２へ集束し、他の部分は反射面２２により反
射されて磁気光学素子２０を再び透過し、レンズ１６に
より第３光ファイバ１４へ集束され、図示しない受光素
子により光の強度を検出される。先に述べたように、反
射光は大きな回折損失を受けるが、透過光はほとんど影
響されないので、第２光ファイバ１２を経て別の目的に
使用する。例えば別のセンサに接続したり、光通信に利
用する。Embodiment 1 FIG. 1 shows an embodiment of an optical magnetic field sensor according to the present invention. The optical magnetic field sensor has a first optical fiber 10 for incidence and a second optical fiber 12 for emission, and a collimator lens 1 between them.
6 and 18, and a magneto-optical element 20 between the lenses 16 and 18. The magneto-optical element 20 has a multi-domain structure as described above, and is made of a material such that when no magnetic field is applied, the magnetization components parallel to the traveling direction of light become opposite to each other in adjacent magnetic domains. , Placed in the magnetic field to be measured. The exit surface of the magneto-optical element 20 becomes a reflection surface 22 for incident light due to the difference between the refractive index of the magneto-optical element and air. Alternatively, the reflection surface may be formed by a dielectric multilayer film so as to have a predetermined reflectance.
Further, a third optical fiber 14 for receiving the reflected light and guiding it to the light receiving element is arranged on the incident side of the lens 13. Known means for preventing reflection is applied to the incident surface of the magneto-optical element 20, both surfaces of the lenses 16 and 18, and the end surfaces of the optical fibers 10 and 12. For example, measures such as applying an anti-reflection film, cutting the optical fiber obliquely, and bonding the optical fiber and the lens are taken. The light emitted from the first optical fiber 10 is converted into parallel light by the lens 16 and passes through the magneto-optical element 20, and a part of the light is focused on the second optical fiber 12 by the lens 18, and the other part is reflected by the reflection surface 22. Then, the light passes through the magneto-optical element 20 again, is focused on the third optical fiber 14 by the lens 16, and the light intensity is detected by the light receiving element (not shown). As described above, the reflected light undergoes a large diffraction loss, but the transmitted light is hardly affected. Therefore, the reflected light is used for another purpose through the second optical fiber 12. For example, it is connected to another sensor or used for optical communication.
【０００８】実施例２ 図２は本発明の光磁界センサの他の実施例を示す。この
例では、上に述べた実施例における第３光ファイバ１４
が省略され、その代わりに第１光ファイバ１０が反射光
を導くための光ファイバを兼用している。その他は点は
実施例１と同様である。Embodiment 2 FIG. 2 shows another embodiment of the optical magnetic field sensor according to the present invention. In this example, the third optical fiber 14 in the above-described embodiment is used.
Are omitted, and the first optical fiber 10 also serves as an optical fiber for guiding the reflected light instead. The other points are the same as in the first embodiment.
【０００９】実施例３ 図３は図１に示した実施例による光磁界センサを複数個
使用した光磁界測定装置の一例を示し、光源３０には光
ファイバ３１、３３、３５を介して光磁界センサ３２、
３４、３６が直列に接続され、また、これらの光磁界セ
ンサは光ファイバ３７、３９、４１を介して複数個の受
光素子３８、４０、４２に接続されている。光源３０か
らの入射光は光ファイバ３１、３３、３５を通して光磁
界センサ３２、３４、３６を順に透過し、一方これらの
光磁界センサからの反射光は光ファイバ３７、３９、４
１により受光素子３８、４０、４２にそれぞれ導かれ
る。このようにして、複数カ所の磁界が受光素子の位置
で同時に測定できる。ただし、後の光磁界センサからの
反射光は先行する光磁界センサにおける回折損失を補償
する必要がある。Embodiment 3 FIG. 3 shows an example of an optical magnetic field measuring apparatus using a plurality of optical magnetic field sensors according to the embodiment shown in FIG. 1, and an optical magnetic field is supplied to a light source 30 via optical fibers 31, 33 and 35. Sensor 32,
34, 36 are connected in series, and these optical magnetic field sensors are connected to a plurality of light receiving elements 38, 40, 42 via optical fibers 37, 39, 41. The incident light from the light source 30 sequentially passes through the optical magnetic field sensors 32, 34, and 36 through the optical fibers 31, 33, and 35, while the reflected light from these optical magnetic field sensors transmits the optical fibers 37, 39, and
1 guides the light to the light receiving elements 38, 40, 42, respectively. In this way, a plurality of magnetic fields can be simultaneously measured at the position of the light receiving element. However, the reflected light from the subsequent optical magnetic field sensor needs to compensate for the diffraction loss in the preceding optical magnetic field sensor.
【００１０】実施例４ 図４は図２に示した実施例による光磁界センサを複数個
使用した光磁界測定装置の一例を示す。パルス光を発生
する光源４４に、所定の時間経過後の反射光のみが受光
素子５４に戻るようにスイッチするスイッチ４６が接続
され、次いで光ファイバ４７、４９、５１を介して直列
に光磁界センサ４８、５０、５２が接続されている。光
ファイバ４７、４９、５１は反射光用に兼用されてい
る。光スイッチ４６には反射光を受信するために光ファ
イバ５３を介して受光素子５４が接続されている。動作
において、光源４４からパルス光を出射させ、光スイッ
チ４６を経て順次光磁界センサ４８、５０、５２に送
る。これらの光磁界センサからの反射光は、それぞれの
光磁界センサの位置により定まった時間の経過後に受光
素子５４に戻る。したがって、光スイッチ４６により任
意の光磁界センサからの反射光のみを受光素子５４に入
射させるようにスイッチすれば、任意の光磁界センサに
おける磁界を測定することができる。Embodiment 4 FIG. 4 shows an example of an optical magnetic field measuring apparatus using a plurality of optical magnetic field sensors according to the embodiment shown in FIG. A switch 46 for switching only the reflected light after a predetermined time elapses to the light receiving element 54 is connected to the light source 44 for generating the pulsed light, and then the optical magnetic field sensor is connected in series via the optical fibers 47, 49, 51. 48, 50 and 52 are connected. The optical fibers 47, 49, and 51 are also used for reflected light. A light receiving element 54 is connected to the optical switch 46 via an optical fiber 53 for receiving the reflected light. In operation, pulse light is emitted from the light source 44, and is sequentially sent to the optical magnetic field sensors 48, 50, and 52 via the optical switch 46. The reflected light from these optical magnetic field sensors returns to the light receiving element 54 after a lapse of time determined by the position of each optical magnetic field sensor. Therefore, if the optical switch 46 is switched so that only the reflected light from any optical magnetic field sensor is incident on the light receiving element 54, the magnetic field in any optical magnetic field sensor can be measured.
【００１１】[0011]
【発明の効果】本発明によれば、光磁界センサに多機能
を持たせることができ、光通信において伝送を中断する
ことなく磁界を測定したり、同時に多数点の磁界を測定
することができる。According to the present invention, the optical magnetic field sensor can be provided with multiple functions, and the magnetic field can be measured without interrupting the transmission in the optical communication, or the magnetic field at multiple points can be measured at the same time. .
【図１】本発明の実施例による光磁界センサを示す。FIG. 1 shows an optical magnetic field sensor according to an embodiment of the present invention.
【図２】本発明の他の実施例による光磁界センサを示
す。FIG. 2 shows an optical magnetic field sensor according to another embodiment of the present invention.
【図３】本発明の磁界測定装置の一例を示す。FIG. 3 shows an example of a magnetic field measuring apparatus according to the present invention.
【図４】本発明の磁界測定装置の他の例を示す。FIG. 4 shows another example of the magnetic field measuring device of the present invention.
【図５】従来の透過式光磁界センサを示す。FIG. 5 shows a conventional transmission type optical magnetic field sensor.
【図６】先願の透過式光磁界センサを示す。FIG. 6 shows a transmission type optical magnetic field sensor of the prior application.
【図７】先願の反射式光磁界センサを示す。FIG. 7 shows a reflection type optical magnetic field sensor of the prior application.
１０ 第１光ファイバ １２ 第２光ファイバ １４ 第３光ファイバ １６、１８ コリメータレンズ ２０ 磁気光学素子 ２２ 反射面 ３０ 光源 ３１、３３、３５ 光ファイバ ３２、３４、３６ 光磁界センサ ３８、４０、４２ 受光素子 ３７、３９、４１ 光ファイバ ４４ 光源 ４６ スイッチ ４７、４９、５１ 光ファイバ ４８、５０、５２ 光磁界センサ ５３ 光ファイバ ５４ 受光素子 DESCRIPTION OF SYMBOLS 10 1st optical fiber 12 2nd optical fiber 14 3rd optical fiber 16, 18 Collimator lens 20 Magneto-optical element 22 Reflection surface 30 Light source 31, 33, 35 Optical fiber 32, 34, 36 Optical magnetic field sensor 38, 40, 42 Light reception Element 37, 39, 41 Optical fiber 44 Light source 46 Switch 47, 49, 51 Optical fiber 48, 50, 52 Optical magnetic field sensor 53 Optical fiber 54 Light receiving element
Claims (4)
射用の第２光ファイバと、反射光出射用の第３光ファイ
バと、多磁区構造を有し且つ磁界を印加しない時に光の
進行方向に平行な磁化成分が隣接する磁区で互いに逆方
向になるような材料より製作した磁気光学素子と、反射
面とより構成され、第１光ファイバからの出射光が磁気
光学素子を透過し、その一部は透過光出射用の第２光フ
ァイバに集束され、他の一部は反射面により反射されて
磁気光学素子を再度透過し、反射光出射用の第３光ファ
イバへ集束されるようになっている、光磁界センサ。1. A first optical fiber for light incidence, a second optical fiber for emission of transmitted light, a third optical fiber for emission of reflected light, a light having a multi-domain structure, and having no magnetic field applied. A magneto-optical element made of a material in which magnetization components parallel to the traveling direction of the magnetic domain are adjacent to each other in a direction opposite to each other, and a reflecting surface, and light emitted from the first optical fiber passes through the magneto-optical element. A part of the light is focused on the second optical fiber for emitting transmitted light, and the other part is reflected by the reflection surface, passes through the magneto-optical element again, and is focused on the third optical fiber for emitting reflected light. An optical magnetic field sensor.
ている請求項１に記載の光磁界センサ。2. The optical magnetic field sensor according to claim 1, wherein the first optical fiber also serves as a third optical fiber.
光ファイバにより直列に結合し、それぞれの第３光ファ
イバをそれぞれの受光素子に結合し、複数カ所の磁界を
任意に測定可能にした磁界測定装置。3. A plurality of optical magnetic field sensors according to claim 1 are connected in series by an optical fiber, and each third optical fiber is connected to each light receiving element, so that magnetic fields at a plurality of locations can be arbitrarily measured. Magnetic field measuring device.
光ファイバにより直列に結合し、任意の光磁界センサか
らの反射光を光スイッチにより選択して単一の受光素子
に結合し、複数カ所の磁界を任意に測定可能にした磁界
測定装置。4. A plurality of optical magnetic field sensors according to claim 2 are connected in series by an optical fiber, and reflected light from any optical magnetic field sensor is selected by an optical switch and coupled to a single light receiving element. A magnetic field measurement device that can arbitrarily measure magnetic fields at multiple locations.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21742992A JP3145798B2 (en) | 1992-07-24 | 1992-07-24 | Optical magnetic field sensor and magnetic field measuring device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21742992A JP3145798B2 (en) | 1992-07-24 | 1992-07-24 | Optical magnetic field sensor and magnetic field measuring device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0643229A JPH0643229A (en) | 1994-02-18 |
| JP3145798B2 true JP3145798B2 (en) | 2001-03-12 |
Family
ID=16704081
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21742992A Expired - Fee Related JP3145798B2 (en) | 1992-07-24 | 1992-07-24 | Optical magnetic field sensor and magnetic field measuring device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3145798B2 (en) |
-
1992
- 1992-07-24 JP JP21742992A patent/JP3145798B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0643229A (en) | 1994-02-18 |
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