JPH01316707A - Optical fiber for sensor - Google Patents

Optical fiber for sensor

Info

Publication number
JPH01316707A
JPH01316707A JP63149019A JP14901988A JPH01316707A JP H01316707 A JPH01316707 A JP H01316707A JP 63149019 A JP63149019 A JP 63149019A JP 14901988 A JP14901988 A JP 14901988A JP H01316707 A JPH01316707 A JP H01316707A
Authority
JP
Japan
Prior art keywords
cores
optical fiber
change
stress
sensor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP63149019A
Other languages
Japanese (ja)
Inventor
Kazuo Sanada
和夫 真田
Toshiyuki Tanaka
利行 田中
Takeru Fukuda
福田　長
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fujikura Ltd
Original Assignee
Fujikura Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fujikura Ltd filed Critical Fujikura Ltd
Priority to JP63149019A priority Critical patent/JPH01316707A/en
Publication of JPH01316707A publication Critical patent/JPH01316707A/en
Pending legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/105—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type having optical polarisation effects

Landscapes

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

Abstract

PURPOSE:To improve stability and linearity against the change of incidence conditions by providing stress giving parts which face each other across cores in a clad wherein the cores are embedded. CONSTITUTION:The couple of cores 13 and 13 are embedded in the clad 12 and the couple of nearly circular stress giving parts 14 and 14 are formed across said cores 13 and 13. The shape, etc., of the clads 12 is not limited specially and the number of the cores 13 is preferably two, but >=3 cores are allowed; and the shape, number, etc., of the stress giving parts 14 are not limited specially as long as they stress the cores 13. The stability to the change of the incidence conditions, etc., and the polarization characteristics as a dual core type single mode optical fiber are improved greatly through the double refraction caused by the core parts by the stress giving parts 14. Consequently, the stability to the change of the incidence conditions, etc., is excellent and the sensor optical fiber which has high reliability as to the linearity is obtained.

Description

【発明の詳細な説明】[Detailed description of the invention]

〈産業上の利用分野〉 本発明は、光フアイバ自体をセンサとして使用する場合
のセンサ月光ファ゛イバに関するものである。 〈従来の技術〉 従来、温度や歪み等の測定用光ファイバとして、例えば
、デュアルコア型光ファイバが提案されている。 このデュアルコア型光ファイバを図示すると、第２図の
如くで、この光ファイバ１は、クラッド２中に２個の屈
折率の異なるコア３．３が埋設されてなる。 そして、この光ファイバ１の使用にあたっては、例え、
ば温度測定の場合を例にとると、第３図に示したように
リール４等に当該光ファイバ１を巻いた状態で例えば液
体等の被測定物５中に入れ、その一端に、光源（レーザ
発振器等）６からの光を入射させ、他端からの出力光を
、ＴＶカメラ７等で受け、それをデスプレイ８上に干渉
縞９として結像させ、この干渉縞９の移動（変化）を捉
えて、被測定物５の温度測定を行っていた。 ′　ここで、干渉縞（フリンジ）９の移動は、上記光フ
ァイバｌの２個のコア３．３間に位相差が生じた場合に
起こる。この位相差の生じる原因としては、光の到達時
間に変化が生じるからと考えられ、より具体的には、光
のスピードの変化や光路長の変化等によって生じる。つ
まり、一つは異なる屈折率を持つ２個のコア３．３の温
度および歪みによる屈折率変化量の差により生じる光の
スピードの変化であり、もう一つは曲げ等により生じる
互いの光路長の変化である。 そして、その変化量は、具体的にはフリンジの移動した
数によって対応される。 〈発明が解決しようとする課題〉 ところが、従来の上記デュアルコア型光ファイバ１にあ
っては、実際の使用環境下において、レーザ光のパワー
変動およびファイバの軸ずれ等により入射条件の変化等
に対する安定性が悪く、また直線性に対する信頼性に欠
ける面があった。 この関係を示すと、第４図〜第５図の如（で、第４図で
はフリンジ数と温度の関係を示し、第５図ではフリンジ
数と光ファイバ長さの関係を示したものであるが、従来
のデュアルコア型光ファイバ１にあっては、グラフ線！
、■が示したように良好な直線性は得られなかった。 本発明は、このような従来の実情に鑑みてなされたもで
のあり、特に、上記フリンジ数と温度や光ファイバ長さ
等の関係において、入射条件の変化等に対する安定性を
図ると同時に、直線性の改善を図ったセンサ用の光ファ
イバを提供せんとするにある。 〈課題を解決するための手段〉 か−る目的を達成する本発明のセンサ用光ファイバは、
複数のコアが埋設されたクラッド中に前記コアを挟んで
対向する応力付与部を設けたものである。 〈作用〉 このクラッド中への応力付与部の形成により、入射条件
の変化等に対する安定化が図られ、かつ光ファイバの偏
波特性が改善されるため、上述したフリンジ数と温度や
光ファイバ長さ等の関係において、良好な直線性が得ら
れる。 〈実施例〉 第１図（Ａ）〜（Ｃ）は本発明に係るセンサ用光ファイ
バの各実施例を示したものである。 各図において、１２はクラッド、１３はコア、１４は応
力付与部である。 より具体的には、第１図（Ａ）の場合は略真円のクラッ
ド１１中に一対のコア１３．１３が埋設され、丁度この
各コア１３．１３を挟むようにして一対の略真円からな
る応力付与部１４．１４が形成されてなる。第１図（Ｂ
）の場合はやはり略真円のクラッド１１中に一対のコア
１３．１３が埋設され、丁度この各コア１３．１３を挾
むようにして一対の略楕円からなる応力付与部１４，１
４が形成されてなる。第２図（Ｃ）の場合は対向する側
面が一部除去された断面小判型のクラッド１１中に一対
のコア１３．１３が埋設され、丁度この各コア１３．１
３を挟むようにして一対の略楕円からなる応力付与部１
４．１４が形成されてなる。 このように本発明では、クラッド１２の形状等は特に限
定されず、またコア１３の数は実用的な面からすると、
上記一対の場合（デュアルコア型）が好ましいが、３個
以上でもよく、また応力付与部１４にあっても、コア１
３に応力を与える構造であれば、その形状、数等は特に
限定されない。 上記応力付与部１４の形成にあたっては、例えば、先ず
、ドーパントとして、Ｂ２Ｏ３、Ｇｅ０１、Ｆ等を選択
し、ドープ量の多いシリカベースのガラスロンドをＭＣ
ＶＤ法等により作成する。 そして、その後、応力付与部１４に相当する部分に穴を
開けた母材を作成し、前記ガラスロンドの応力付与部１
４を穴に入れ、ロッドインチューブ法によりファイバを
作成する。 この応力付与部１４による、コア部に生じる複屈折の作
用により、入射条件の変化等に対する安定化およびデュ
アルコア型単一モード光ファイバとしての偏波特性が大
幅に改善される。 因みに、本発明のセンサ用光ファイバを用いて、上述し
た第４図のフリンジ数と温度の関係や、第５図のフリン
ジ数と光ファイバ長さ等の関係について調べたところ、
略直線のグラフ線■、■が得られ、温度に対する直線性
および長さに対する直線性が著しく改善されていること
が判った。 〈発明の効果〉 以上の説明から明らかなように本発明によれば、実際の
使用環境下において、入射条件の変化等に対する安定性
が良く、また直線性に対する高い信頼性のある優れたセ
ンサ用光ファイバが得られる。<Industrial Application Field> The present invention relates to a sensor moonlight fiber when the optical fiber itself is used as a sensor. <Prior Art> Conventionally, for example, a dual-core optical fiber has been proposed as an optical fiber for measuring temperature, strain, etc. This dual-core optical fiber is shown in FIG. 2, and the optical fiber 1 has two cores 3.3 having different refractive indexes embedded in a cladding 2. When using this optical fiber 1, for example,
For example, in the case of temperature measurement, as shown in FIG. 3, the optical fiber 1 is wound around a reel 4 and placed in a measured object 5 such as a liquid, and a light source ( The light from a laser oscillator, etc.) 6 is input, the output light from the other end is received by a TV camera 7, etc., and it is imaged on a display 8 as interference fringes 9, and the interference fringes 9 move (change). The temperature of the object to be measured 5 was measured by capturing the temperature. ' Here, the movement of the interference fringes (fringes) 9 occurs when a phase difference occurs between the two cores 3.3 of the optical fiber l. This phase difference is thought to be caused by a change in the arrival time of the light, and more specifically, by a change in the speed of the light, a change in the optical path length, etc. In other words, one is the change in the speed of light caused by the difference in the amount of change in the refractive index due to temperature and strain between the two cores 3.3, which have different refractive indexes, and the other is the change in the optical path length of each other caused by bending, etc. This is a change in Specifically, the amount of change corresponds to the number of fringe movements. <Problems to be Solved by the Invention> However, in the above-mentioned conventional dual-core optical fiber 1, under the actual usage environment, it is difficult to cope with changes in the incident conditions due to power fluctuations of the laser beam, misalignment of the fiber axis, etc. It had poor stability and lacked reliability in linearity. This relationship is shown in Figures 4 and 5 (Figure 4 shows the relationship between the number of fringes and temperature, and Figure 5 shows the relationship between the number of fringes and the length of the optical fiber. However, for the conventional dual-core optical fiber 1, the graph line!
As shown in , ■, good linearity was not obtained. The present invention has been made in view of the above-mentioned conventional circumstances, and in particular, in the relationship between the number of fringes, temperature, optical fiber length, etc., it aims at stability against changes in incident conditions, etc. The object of the present invention is to provide an optical fiber for a sensor with improved linearity. <Means for solving the problem> The optical fiber for a sensor of the present invention that achieves the above object has the following features:
A cladding in which a plurality of cores are embedded is provided with stress applying portions that face each other with the cores interposed therebetween. <Function> By forming this stress-applying part in the cladding, it is stabilized against changes in the incident conditions, etc., and the polarization characteristics of the optical fiber are improved. Good linearity can be obtained in terms of length, etc. <Example> FIGS. 1A to 1C show examples of the optical fiber for a sensor according to the present invention. In each figure, 12 is a cladding, 13 is a core, and 14 is a stress applying part. More specifically, in the case of FIG. 1(A), a pair of cores 13.13 are embedded in a substantially perfect circular cladding 11, and each core 13.13 is sandwiched between the pair of substantially perfect circles. A stress applying portion 14.14 is formed. Figure 1 (B
), a pair of cores 13.13 are buried in the approximately perfect circular cladding 11, and a pair of approximately elliptical stress applying portions 14, 1 are placed between each core 13.13.
4 is formed. In the case of FIG. 2(C), a pair of cores 13.13 are buried in the clad 11, which has an oval cross section with opposing side surfaces partially removed, and each core 13.1
A stress applying section 1 consisting of a pair of substantially elliptical shapes sandwiching the stress applying section 1
4.14 is formed. As described above, in the present invention, the shape of the cladding 12 is not particularly limited, and the number of cores 13 is determined from a practical standpoint.
The above-mentioned case of a pair (dual core type) is preferable, but three or more may be used.
The shape, number, etc. are not particularly limited as long as they have a structure that applies stress to 3. In forming the stress applying portion 14, for example, first, B2O3, Ge01, F, etc. are selected as the dopant, and a silica-based glass iron with a large amount of doping is MC.
Created by VD method etc. After that, a base material is created in which a hole is made in a portion corresponding to the stress applying portion 14, and the stress applying portion 1 of the glass rond is prepared.
4 into the hole and create a fiber using the rod-in-tube method. Due to the effect of birefringence generated in the core portion by the stress applying portion 14, stabilization against changes in incident conditions and the like and polarization characteristics as a dual-core type single mode optical fiber are significantly improved. Incidentally, when using the sensor optical fiber of the present invention, we investigated the relationship between the number of fringe and temperature shown in FIG. 4 and the relationship between the number of fringe and optical fiber length, etc. shown in FIG. 5, and found that
Almost straight graph lines (■) and (2) were obtained, and it was found that the linearity with respect to temperature and the linearity with respect to length were significantly improved. <Effects of the Invention> As is clear from the above description, the present invention provides an excellent sensor with good stability against changes in incident conditions and high reliability in linearity under actual usage environments. Optical fiber is obtained.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図（Ａ）〜（Ｃ）は本発明に係るセンサ用光ファイ
バの各実施例を示した縦断面図、第２図は従来のデュア
ルコア型光ファイバを示した縦断面図、第３図は光フア
イバ自体をセンサとして使用する場合の装置系の一例を
示した概略説明図である。 図中、 １２・・・・クラッド、 １３・・・・コア、 １４・・・・応力付与部、 特許出願人　　藤倉電線株式会社 第１図ＣＡ）　　　　　　第１図１？）第３図 第４図 特許庁長官　吉　１）文　毅　殿 １、事件の表示 昭和６３年特許願第１４９０１９号 ２、発明の名称 センサ用光ファイバ ３、補正をする者 事件との関係　特許出願人 住所　東京都江東区木場−丁目５番１号名称　藤　倉　
電　線　株式会社　（ほか１名）代表者加賀谷誠− ４、代理人＠１４１　ｆｆ０３（４４０）−６７６１住
所　東京部品用区東五反田五丁目２３番１号６、補正の
対象1(A) to 1(C) are vertical cross-sectional views showing each embodiment of the optical fiber for a sensor according to the present invention, FIG. 2 is a vertical cross-sectional view showing a conventional dual-core optical fiber, and FIG. The figure is a schematic explanatory diagram showing an example of a device system in which the optical fiber itself is used as a sensor. In the figure, 12... cladding, 13... core, 14... stress applying part, patent applicant Fujikura Electric Wire Co., Ltd. Figure 1 CA) Figure 1 1? ) Figure 3 Figure 4 Director General of the Patent Office Yoshi 1) Takeshi Moon 1, Indication of the case 1988 Patent Application No. 149019 2, Name of the invention Optical fiber for sensor 3, Person making the amendment Relationship with the case Patent application Address: 5-1 Kiba-chome, Koto-ku, Tokyo Name: Fujikura
Electric Cable Co., Ltd. (and 1 other person) Representative Makoto Kagaya-4, Agent @ 141 ff03 (440)-6761 Address 5-23-1-6 Higashigotanda, Tokyo Parts Ward, Subject of amendment

【図面の簡単な説明】[Brief explanation of the drawing]

１、明細書中、第７図第５行目〜第６行目の「・・・概
略説明図である。」を、「・・・概略説明図、第４図は
フリンジ数と温度の関係を示したグラフ、第５図はフリ
ンジ数と光ファイバ長さの関係を示したグラフである。 」と補正する。1. In the specification, "...is a schematic explanatory diagram" in lines 5 and 6 of Figure 7 is replaced with "...is a schematic explanatory diagram. Figure 5 is a graph showing the relationship between the number of fringes and the length of the optical fiber.''

Claims (1)

【特許請求の範囲】[Claims] 複数のコアが埋設されたクラッド中に前記コアを挟んで
対向する応力付与部を設けたことを特徴とするセンサ用
光ファイバ。1. An optical fiber for a sensor, comprising a cladding in which a plurality of cores are embedded, and stress applying portions facing each other with the cores sandwiched therebetween.
JP63149019A 1988-06-16 1988-06-16 Optical fiber for sensor Pending JPH01316707A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP63149019A JPH01316707A (en) 1988-06-16 1988-06-16 Optical fiber for sensor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP63149019A JPH01316707A (en) 1988-06-16 1988-06-16 Optical fiber for sensor

Publications (1)

Publication Number Publication Date
JPH01316707A true JPH01316707A (en) 1989-12-21

Family

ID=15465894

Family Applications (1)

Application Number Title Priority Date Filing Date
JP63149019A Pending JPH01316707A (en) 1988-06-16 1988-06-16 Optical fiber for sensor

Country Status (1)

Country Link
JP (1) JPH01316707A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016020865A (en) * 2014-07-15 2016-02-04 古河電気工業株式会社 Stress distribution measuring method using optical fiber, and stress distribution measuring device
EP2722659B1 (en) * 2009-04-27 2018-03-21 Picometrix, LLC System and method reducing fiber stretch induced timing errors in fiber optic coupled time domain terahertz systems

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2722659B1 (en) * 2009-04-27 2018-03-21 Picometrix, LLC System and method reducing fiber stretch induced timing errors in fiber optic coupled time domain terahertz systems
JP2016020865A (en) * 2014-07-15 2016-02-04 古河電気工業株式会社 Stress distribution measuring method using optical fiber, and stress distribution measuring device

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