JPH02103434A - Method for measuring strain distribution in longitudinal direction of optical fiber cable and apparatus and optical fiber used in said method - Google Patents
Method for measuring strain distribution in longitudinal direction of optical fiber cable and apparatus and optical fiber used in said methodInfo
- Publication number
- JPH02103434A JPH02103434A JP25766388A JP25766388A JPH02103434A JP H02103434 A JPH02103434 A JP H02103434A JP 25766388 A JP25766388 A JP 25766388A JP 25766388 A JP25766388 A JP 25766388A JP H02103434 A JPH02103434 A JP H02103434A
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- Prior art keywords
- optical fiber
- strain distribution
- longitudinal direction
- cable
- optical
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 90
- 238000000034 method Methods 0.000 title claims description 6
- 230000010287 polarization Effects 0.000 claims description 18
- 238000000253 optical time-domain reflectometry Methods 0.000 claims description 13
- 238000009434 installation Methods 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 230000003287 optical effect Effects 0.000 abstract description 5
- 239000000835 fiber Substances 0.000 abstract description 3
- 230000004069 differentiation Effects 0.000 abstract 1
- 238000005452 bending Methods 0.000 description 17
- 238000005259 measurement Methods 0.000 description 14
- 238000010586 diagram Methods 0.000 description 8
- 230000008878 coupling Effects 0.000 description 7
- 238000010168 coupling process Methods 0.000 description 7
- 238000005859 coupling reaction Methods 0.000 description 7
- 230000002159 abnormal effect Effects 0.000 description 6
- 238000000926 separation method Methods 0.000 description 4
- 230000001902 propagating effect Effects 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 230000003449 preventive effect Effects 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 101000878457 Macrocallista nimbosa FMRFamide Proteins 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
- G01M11/31—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers
- G01M11/3181—Reflectometers dealing with polarisation
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- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Testing Of Optical Devices Or Fibers (AREA)
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
この発明は、■光ケーブル内の光ファイバに加わる曲げ
などによる歪の長さ方向分布測定方法と、■その実施に
使用するＯＴＤＲ装置および■光ファイバに関するもの
である。[Detailed Description of the Invention] [Industrial Application Field] This invention relates to: ■ a method for measuring the longitudinal distribution of strain due to bending applied to an optical fiber in an optical cable, ■ an OTDR device used to carry out the method, and ■ an optical It concerns fiber.
［従来の技術そのｌ］
【１］その内容；
光フアイバ内の歪は、曲げや引張りや側圧などによって
も生ずる。しかし、撚り合わせられた光ケーブル内の光
ファイバが、曲げや側圧を受けずに単純な引張りを受け
ることはないので、以下的げを主にして説明する。また
、いわゆるマイクロベンドについても同様の考え方がで
きる。[Prior Art Part 1] [1] Contents; Strain within an optical fiber is also caused by bending, tension, lateral pressure, etc. However, since the optical fibers in the twisted optical cable are not subjected to bending or lateral pressure and are not subjected to simple tension, the following description will focus mainly on the purpose. A similar idea can also be applied to so-called micro bends.
光ファイバに曲がりが生ずると、損失が増大する。その
損失増や光ファイバの破断をＷｌ′ｌＪ４する方法にＯ
ＴＤＲまたは光パルス試験と呼ばれているものがある。When an optical fiber is bent, losses increase. How to prevent the increase in loss and breakage of the optical fiber
There is something called TDR or optical pulse test.
この方法では、１５４図に示すように、電気パルスをパ
ルス発生器１２からＬＤ１４に送りこみ、発生する数１
０ｎｓｅｃ〜数ＪＬｓｅｃの光パルスを光ファイバ１８
に入射、光ファイバ１８の各部からの後方散乱光のうち
光ファイバ１８にふたたび導波されたものを、ハーフミ
ラ−１６および受光器２０を通して、波形解析装置２２
で観測する。In this method, as shown in Fig. 154, electric pulses are sent from the pulse generator 12 to the LD 14, and the number 1
A light pulse of 0 nsec to several JLsec is sent to the optical fiber 18.
Of the backscattered light from each part of the optical fiber 18, the backscattered light is guided into the optical fiber 18 again through a half mirror 16 and a light receiver 20, and then passed through a waveform analyzer 22.
Observe with.
このとき得られる波形は、第５図のようなものとなる。The waveform obtained at this time is as shown in FIG.
ここで、大きな反射ピークＣは、そこで光ファイバが断
線していることを示している。Here, the large reflection peak C indicates that the optical fiber is broken at that point.
また段差Ｂは、その地点で光ファイバに何か局部的な損
失原因が存在していることを示している０局部的な損失
原因としては、■曲がり、■コア中の気泡、■光ファイ
バ間の接続点などがある。In addition, the step B indicates that there is some local loss cause in the optical fiber at that point.Local loss causes include: - bending, - air bubbles in the core, and - between the optical fibers. There are connection points, etc.
［２］発明の解決すべき課題：
（１）予兆現象について：
布設後の光ファイバケーブルが、異常な曲げ応力を受け
たとき、初めは小さい曲率の曲がりであったのが、やが
て大きな曲率になり、遂に破断（通信途絶）に至ること
が考えられる。[2] Problems to be solved by the invention: (1) Predictive phenomena: When an optical fiber cable after installation is subjected to abnormal bending stress, the bend initially has a small curvature, but eventually becomes a large curvature. It is conceivable that this will eventually lead to a breakdown (communication interruption).
そのような場合、小さい曲率の曲がりが、破断前の「予
兆」 （前兆、きざし）現象として現れる。In such cases, a bend with a small curvature appears as a ``foreshadow'' phenomenon before failure.
したがって、その予兆を検知することができれば、破断
を回避でき、光ファイバケーブル布設後の、予防保全的
な保守管理上、非常に望ましい。Therefore, if the signs of such occurrence can be detected, breakage can be avoided, which is highly desirable for preventive maintenance management after optical fiber cable installation.
しかし、その予兆のようなものをつかむことは容易でな
い。However, it is not easy to grasp such signs.
（２）光ファイバの曲げ損失について：元来、光ファイ
バは光を安定に伝搬できるようにその構造を設計されて
いる。たとえば、波長１．３沖腸を伝送できるように設
計された単一モード光ファイバでは、第６図に示すよう
に、あるきわどい曲げ半径になるまで損失を示さず、そ
の点を越えると急激に曲げ損失が増大する。(2) Regarding bending loss of optical fibers: Originally, the structure of optical fibers was designed so that light could be stably propagated. For example, a single-mode optical fiber designed to transmit a wavelength of 1.3 mm does not exhibit any loss until a certain critical bend radius is reached, as shown in Figure 6, and beyond that point the loss suddenly increases. Bending loss increases.
なぜこのような曲げ損失特性になるかというと、伝搬し
ている基本モードの曲げによる損失は、光ファイバ軸を
曲げたときの一種の放射モードへの結合とみなし得るの
であるが、基本モードの位相定数と放射モード位相定数
との間には大きな差があり、少々の曲がりでは簡単に結
合しないようになっているからである。The reason for this bending loss characteristic is that the loss due to bending of the propagating fundamental mode can be considered as a type of coupling to the radiation mode when the optical fiber axis is bent. This is because there is a large difference between the phase constant and the radiation mode phase constant, and a slight bend will prevent them from coupling easily.
なお、逆にこのような予兆を示しやすい光ファイバでは
、ケーブル作製そのものの工程で生ずる曲がりでも、Ｓ
川な損失増を示してしまうことになる。On the other hand, optical fibers that tend to show such signs may suffer from S
This would result in a significant increase in losses.
（３）従来のＯＴＤＲについて：
以上のことは、従来のＯＴＤＲで布設後の光ファイバケ
ーブルの後方散乱波形の経時変化を観測していても、上
記の「予兆」をつかむことは難しいことを示している。(3) Regarding conventional OTDR: The above shows that even if conventional OTDR is used to observe changes over time in the backscattered waveform of optical fiber cables after installation, it is difficult to grasp the above-mentioned "signs." ing.
［従来技術その２１
［１］その内容：
第７図のように、偏光分離プリズム２４からなる方向性
結合器を通して、光パルスを光ファイバ１８に入射し、
かつ後方散乱光を波形解析装置２２に送るＯＴＤＲ回路
も、知られている。[Prior Art No. 21 [1] Contents: As shown in FIG.
Also known is an OTDR circuit that sends backscattered light to the waveform analyzer 22.
［２］発明の解決すべき課題：
この場合、光ファイバ１８に入射した光は直線偏光にな
っている。しかし光フアイバ１８内で一度後方散乱した
光の偏光状態は、はとんど無偏光に近くなっている。[2] Problem to be solved by the invention: In this case, the light incident on the optical fiber 18 is linearly polarized light. However, the polarization state of the light once backscattered within the optical fiber 18 is almost unpolarized.
ところで、通常の光ファイバのコアの断面はほぼ円形を
している。そして、厳密には、単一モード光ファイバを
伝搬する基本モードには２つの厳密解が含まれており（
ＨＥ＋ｔモード）、２つのモードは互いに直交する偏光
を有する。また理想的には、円形コアの光ファイバの２
つの直交モードは完全に縮退していて、その伝搬定数（
位相定数）の差はゼロである。By the way, the cross section of the core of a typical optical fiber is approximately circular. Strictly speaking, the fundamental mode propagating in a single mode optical fiber contains two exact solutions (
HE+t mode), the two modes have mutually orthogonal polarizations. Ideally, two of the circular core optical fibers are
The two orthogonal modes are completely degenerate and their propagation constant (
phase constant) is zero.
ただし、通常の光ファイバにおいては、わずかにコアの
偏平などがあるが、この異方性にともなう縮退からのず
れは、ごく小さい。However, although a normal optical fiber has a slightly flattened core, the deviation from degeneracy due to this anisotropy is extremely small.
このため、通常の光ファイバに曲げなどの外力を加える
と、非常にわずかな力で２つの直交モード間に結合が起
こり、エネルギーの交換が生じる。Therefore, when an external force such as bending is applied to a normal optical fiber, coupling occurs between the two orthogonal modes with a very small force, resulting in energy exchange.
すなわち、第７図の測定系においては、後方散乱光の受
信が偏光分離プリズム２４を介して行われるため、上記
のわずかな力（製造や布設時に受ける通常の）で結合し
た光ファイバのモードの偏光状態の一方だけを、常に受
信していることになる。In other words, in the measurement system shown in FIG. 7, since the backscattered light is received through the polarization separation prism 24, the mode of the coupled optical fiber is This means that only one polarization state is always received.
その結果、このような測定系の測定波形は第５図の場合
と異なり、第８図のように、非常に激しいゆらいだ状態
になる。As a result, the measurement waveform of such a measurement system is different from that shown in FIG. 5, and as shown in FIG. 8, it is in a state of extremely severe fluctuation.
したがってはこれを防ぐため、今までは偏光分離プリズ
ム２４の使用を避けるのが普通であった。Therefore, in order to prevent this, it has been common practice until now to avoid using the polarization separation prism 24.
［課題を解決するための手段］
上記の従来技術の欠点を積極的に利用して、これまでの
ＯＴＤＲとは異なり、上記の「予兆」、すなわち、より
僅かな曲がり（必ずしも損失を伴わない程度の小応力に
よる）などを検出して、通信途絶にいたる前に予防処置
をとれるようにしたもので、
第１（特定）発明においては、偏光した光パルスを光フ
ァイバに入射し、前記光ファイバの各部から後方に散乱
する光の偏光状態の長さ方向の変化’ｅ １１定し、そ
れによって光ファイバケーブルの長さ方向歪分布を測定
する。[Means for solving the problem] By actively utilizing the shortcomings of the above-mentioned conventional technology, unlike conventional OTDRs, the above-mentioned "premonition", i.e., a slight bending (not necessarily accompanied by loss) can be achieved. In the first (specific) invention, a polarized light pulse is input into an optical fiber, and the optical fiber is The longitudinal change in the polarization state of the light scattered backward from each part of the optical fiber cable is determined, thereby measuring the longitudinal strain distribution of the optical fiber cable.
第２発明は、第１発明の実施に直接使用する歪分布測定
用光ファイバで、単一モード光ファイバからなり、かつ
その直交する２モードが、製造および布設時に受ける通
常の応力では結合しないが、前記通常の応力を越える応
力を受けたとき結合する程度のビート長を持つ。The second invention is an optical fiber for strain distribution measurement that is directly used in carrying out the first invention, and is made of a single mode optical fiber, and its two orthogonal modes are not combined by the normal stress received during manufacturing and installation. , has a beat length that is long enough to bond when subjected to stress exceeding the normal stress.
ｆｆＧ３発明は、第１発明の実施に直接使用するＯＴＤ
Ｒ装置で、偏光した光パルスを光ファイバに入射し、前
記光ファイバの各部から後方に散乱される光を偏光子を
通して光受信する。The ffG3 invention is an OTD that is directly used to implement the first invention.
In the R device, a polarized light pulse is input into an optical fiber, and the light scattered backward from each part of the optical fiber is received through a polarizer.
［その説明］
［１］歪分布測定用光ファイバについてニ一般に光ファ
イバは、ケーブル化や布設に伴ってさまざまな外力を受
ける。上記のように、この外力によって、伝送損失の増
加はないが、２つの直交偏光モードの結合が生じるよう
な状態になっている。[Description] [1] Optical fiber for strain distribution measurement Generally, optical fibers are subjected to various external forces when they are made into cables or installed. As described above, this external force causes no increase in transmission loss, but creates a state in which coupling of two orthogonal polarization modes occurs.
これに対して、本発明で使用する歪分布測定用光ファイ
バは、直交する２モードが、製造および布設時に受ける
通常の応力では結合しないが、前記通常の応力を越える
応力（以下、異常応力という）を受けたとき結合する程
度の異方性を有する。On the other hand, in the optical fiber for strain distribution measurement used in the present invention, the two orthogonal modes do not combine under the normal stress received during manufacturing and installation, but the stress exceeding the normal stress (hereinafter referred to as abnormal stress) ) has such anisotropy that it bonds when subjected to
それをより具体的に示すと、次のとおりである。More specifically, it is as follows.
第１ａ図は、長さ１０ｍにわたって曲げを受けたときの
、曲げ直径と２つのモード間のクロストロークを示して
いる。Figure 1a shows the bending diameter and crossstroke between the two modes when subjected to bending over a length of 10 m.
ここでパラメータＬｂはビート長で、
／ｊ！ −／Ｎ
β冨 、βｙは光ファイバを伝搬する２つの直交偏光基
本モードの位相定数である。Here, the parameter Lb is the beat length, /j! −/N β-value and βy are the phase constants of two orthogonally polarized fundamental modes propagating in the optical fiber.
そこで、歪分布測定用光ファイバとして、Ｌｂが３００
鵬騰あるいはそれよりも若干短い（定偏光光ファイバよ
りもはるかに大きく１通常の光ファイバよりはるかに小
さい）程度のものを用いるのが良いが、これは光ファイ
バケーブルの布設環境で決定される。Therefore, as an optical fiber for strain distribution measurement, Lb is 300
It is better to use Pengteng or something slightly shorter (much larger than fixed polarization optical fiber and much smaller than normal optical fiber), but this will be determined by the installation environment of the optical fiber cable. .
このような光ファイバに、通常受ける以上の異常応力が
加わると、その部分での偏光状態が変化する。When such an optical fiber is subjected to an abnormal stress greater than that normally experienced, the polarization state at that portion changes.
なお、通常の光ファイバケーブル中では、直径１００論
−程度の曲がりが、ケーブル化に伴う撚り合わせなどで
生じているので、 Ｌｂ ＝ ３０軸腸では少し結合し
過ぎるように思われる。In addition, in a normal optical fiber cable, bends with a diameter of about 100 decimal degrees occur due to twisting and the like during cable formation, so it seems that Lb = 30 axes would cause a little too much coupling.
しかし、もしケーブル中の光ファイバがあまり曲がりを
受けないような状態で挿入されているのであれば、Ｌｂ
は大きい程ケーブルに加わる外力の検出感度が高くなる
。However, if the optical fiber in the cable is inserted in such a way that it is not subjected to much bending, then Lb
The larger the value, the higher the detection sensitivity of the external force applied to the cable.
以上の歪分布測定用光ファイバ１８０を、第１ｂ図のよ
うに、通常の光ファイバ１８といっしょに集合して光フ
ァイバケーブル１７を構成する。The above strain distribution measuring optical fibers 180 are assembled together with the normal optical fibers 18 to form the optical fiber cable 17, as shown in FIG. 1b.
［２］ ＯＴＤＲ装置について： ［１Ｆその構成： 第１ｃ図の構成にするのが望ましい。[2] About the OTDR device: [1F composition: The configuration shown in Figure 1c is preferred.
すなわち、方向性結合器にハーフミラ−１６を用い、後
方散乱光を偏光分離プリズム２６により直交するｙ、ｘ
の２方向に分け、それぞれ受光器２０テ、２０ｘで受光
する。That is, a half mirror 16 is used as a directional coupler, and the backscattered light is divided into orthogonal y and x by a polarization separation prism 26.
The light is divided into two directions, and the light is received by receivers 20 and 20x, respectively.
そして、歪分布測定用光ファイバ１８０の同一地点から
の２つの偏光の強度Ｉ！、Ｉ！の比をとることにより、
−＋ Ｉｙ
φ＝ｊａｎ（）
ｘ
を計算し、φの値から、偏光面の回転（向き）を知るこ
とができる。Then, the intensity I of the two polarized lights from the same point on the strain distribution measuring optical fiber 180! ,I! By taking the ratio, −+ Iy φ=jan() x can be calculated, and from the value of φ, the rotation (orientation) of the plane of polarization can be known.
なお、実際には、偏光状態の長さ方向変化が重要な量で
あるので、φを距離の関数とみなして微分することによ
り、微係数の激しい地点で光ファイバに大きな外力が加
わっていることが分る。Note that in reality, the change in the polarization state in the longitudinal direction is an important quantity, so by differentiating φ as a function of distance, it can be determined that a large external force is applied to the optical fiber at a point where the differential coefficient is large. I understand.
［２］その作用：
（１）異常応力を受けないとき：
歪分布測定用光フアイバ１８０内において、直交する２
つのモード間に結合は生じない。[2] The effect: (1) When not receiving abnormal stress: In the strain distribution measurement optical fiber 180, two orthogonal
No coupling occurs between the two modes.
したがって、φのケーブル長さ方向の変化は、第２図の
（ａ）のように、非常にゆるやかな変化しか示さない。Therefore, the change in φ in the cable length direction shows only a very gradual change, as shown in FIG. 2(a).
（２）異常応力を受けたとき：
歪分布測定用光フアイバ１８０内の異常応力を受けた地
点において、直交する２つのモード間に結合が生じる。(2) When receiving abnormal stress: At a point in the optical fiber 180 for strain distribution measurement that receives abnormal stress, coupling occurs between two orthogonal modes.
したがって、φのケーブル長さ方向の変化は、第２図の
（ｂ）のように、急激な変化を示すようになる。Therefore, the change in φ in the cable length direction shows a rapid change as shown in FIG. 2(b).
（３）上記の使い方とは別に、第１ｃ図の波形解析袋ｒ
１２２において、
ＩＸ ＋Ｉ７ ＝Ｉｔｏｔａｌ
を表示させるようにすれば１通常のＯＴＤＲとして使用
することができる。(3) Apart from the above usage, the waveform analysis bag r in Figure 1c
122, if IX + I7 = Itotal is displayed, it can be used as a normal OTDR.
［３］従来の例として、第７図に示したＯＴＤＲも、本
発明に使用することができる。[3] As a conventional example, the OTDR shown in FIG. 7 can also be used in the present invention.
ただしこの場合は、後方散乱光をｘ、ｙの２方向に分け
て測定することができない。However, in this case, it is not possible to measure the backscattered light separately in two directions, x and y.
［実施例］
光ファイバケーブル１７内に、Ｌｂ ＝ ５０龍の歪分
布測定用光ファイバ１８０を配置、ｗＳｌｅ図のＯＴＤ
Ｒで測定した。[Example] An optical fiber 180 for strain distribution measurement with Lb = 50 is placed inside the optical fiber cable 17, and the OTD in the wSle diagram is
Measured at R.
この光ファイバケーブル１７に外力を加えないときのφ
（２）の結果はｔ第２図（ａ）に示すように、非常にゆ
るやかな変化しか示していない。φ when no external force is applied to this optical fiber cable 17
The result of (2) shows only a very gradual change, as shown in Figure 2(a).
しかしながら、この長さ約１に■の光ファイバケーブル
１７の途中の６００ｍの地点にケーブル座屈を生じさせ
ると、そこでは第２図の（ｂ）のように、非常に急激な
偏光面の回転が観測され、大きな曲がりが生じているこ
とが分る。However, if cable buckling occurs at a point 600 m in the middle of the optical fiber cable 17 with a length of approximately 1, there will be a very rapid rotation of the plane of polarization, as shown in (b) in Figure 2. is observed, indicating that a large bend has occurred.
しかし、この座屈状態の光ファイバケーブル１７を１９
通常のＯＴＤＲで観測したところ、第３図の（ｂ）のよ
うに、外力無しの（ａ）に対して波形の変化は非常に僅
かであって、損失はせいぜい０．０５ｄＢ Ｉ、か増加
しなかった。However, when the buckled optical fiber cable 17
When observed with a normal OTDR, as shown in Figure 3 (b), there was a very slight change in the waveform compared to (a) with no external force, and the loss increased by at most 0.05 dB I. There wasn't.
［発明の効果］
（１）偏光した光パルスを光ファイバに入射し、前記光
ファイバの各部から後方に散乱する光の偏光状態の長さ
方向の変化を測定するので、必ずしも損失増加を伴なわ
ないような光ファイバへの外力の印加を検出することが
できるようになった。[Effects of the Invention] (1) Since a polarized light pulse is input into an optical fiber and changes in the polarization state of the light scattered backward from each part of the optical fiber are measured in the longitudinal direction, an increase in loss does not necessarily occur. It is now possible to detect external force applied to an optical fiber.
これにより、光ファイバケーブルが通信途絶などの事態
を招く前に、予防保全処置がとれる。This allows preventive maintenance measures to be taken before the fiber optic cable causes a situation such as a loss of communication.
（２）単一モード光ファイバからなりかつその直交する
２モードが、製造および布設時に受ける通常の応力では
結合しないが、前記通常の応力を越える応力を受けたと
き結合する程度のビート長を持つ、歪分２１ｆＩ測定用
光ファイバを用いるので、これと、偏光した光パルスを
光ファイバに入射し、前記光ファイバの各部から後方に
散乱される光を偏光子を通して光受信するＯＴＤＲとを
組合わせることにより、後方散乱光の偏光状態の長さ方
向の変化を測定することが可能になる。(2) Consisting of a single mode optical fiber, the two orthogonal modes do not combine under the normal stress received during manufacturing and installation, but have a beat length that is sufficient to combine when subjected to stress exceeding the normal stress. , since an optical fiber for strain measurement of 21 fI is used, this is combined with an OTDR that inputs polarized light pulses into the optical fiber and receives the light scattered backward from each part of the optical fiber through a polarizer. This makes it possible to measure changes in the polarization state of backscattered light in the length direction.
第１ａ〜２図は本発明の実施例にかかるもので、第１ａ
図はビート長をパラメータとした光ファイバの、曲げ直
径〜クロストーク特性図、第１ｂ図は歪分布測定用光フ
ァイバ１８０を挿入した光ファイバケーブル１７の説明
図、第１ｃ図は０ＴＤＨの概略構成図、
第２図は偏光面の回転角φの長さ方向分布図、第３図は
本発明の実施例と同じ実験の、通常のＯＴＤＲによる測
定結果の説明図、
ｆ５４図は従来の０ＴＤＨの概略構成図で、第５図はそ
の後方散乱光強度の分布図、第６図は通常の単一モード
光ファイバの曲げ直径〜曲げ損失特性図、
第７図は従来の別のＯＴＤＲの概略構成図で、第８図は
その後方散乱光強度〜時間特性図。
１２：パルス発生器 １４：ＬＤ
１６：ハーフミラ−１７：光ファイバケーブル１８：光
ファイバ ２０：受光器
２２二波形解析装置
２４．２６：偏光分離プリズム
１８０：歪分布測定用光ファイバ1a to 2 show embodiments of the present invention;
The figure is a bending diameter-crosstalk characteristic diagram of an optical fiber with beat length as a parameter, Figure 1b is an explanatory diagram of the optical fiber cable 17 into which the optical fiber 180 for strain distribution measurement is inserted, and Figure 1c is a schematic configuration of 0TDH. Fig. 2 is a longitudinal distribution diagram of the rotation angle φ of the polarization plane, Fig. 3 is an explanatory diagram of the measurement results by ordinary OTDR in the same experiment as the embodiment of the present invention, and Fig. f54 is the distribution of the conventional 0TDH. Figure 5 is a diagram of the backscattered light intensity distribution, Figure 6 is a diagram of the bending diameter and bending loss characteristics of a normal single mode optical fiber, and Figure 7 is a schematic diagram of another conventional OTDR. In the figure, FIG. 8 is a graph showing the backscattered light intensity vs. time characteristic. 12: Pulse generator 14: LD 16: Half mirror 17: Optical fiber cable 18: Optical fiber 20: Photo receiver 22 dual waveform analyzer 24. 26: Polarization separation prism 180: Optical fiber for strain distribution measurement
Claims (3)
ファイバの各部から後方に散乱する光の偏光状態の長さ
方向の変化を測定する、光ファイバケーブルの長さ方向
歪分布測定方法。(1) A method for measuring strain distribution in the longitudinal direction of an optical fiber cable, in which a polarized light pulse is incident on an optical fiber, and changes in the polarization state of light scattered backward from each part of the optical fiber are measured in the longitudinal direction.
る２モードが、製造および布設時に受ける通常の応力で
は結合しないが、前記通常の応力を越える応力を受けた
とき結合する程度のビート長を持つ、光ファイバケーブ
ルの長さ方向歪分布測定用光ファイバ。(2) Consisting of a single mode optical fiber, the two orthogonal modes do not combine under normal stress during manufacturing and installation, but have a beat length that is such that they will combine when subjected to stress exceeding the normal stress. Optical fiber for measuring longitudinal strain distribution of optical fiber cables.
ファイバの各部から後方に散乱される光を偏光子を通し
て光受信する、光ファイバケーブルの長さ方向歪分布測
定用ＯＴＤＲ装置。(3) An OTDR device for measuring strain distribution in the longitudinal direction of an optical fiber cable, which inputs a polarized light pulse into an optical fiber and receives the light scattered backward from each part of the optical fiber through a polarizer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25766388A JPH02103434A (en) | 1988-10-13 | 1988-10-13 | Method for measuring strain distribution in longitudinal direction of optical fiber cable and apparatus and optical fiber used in said method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25766388A JPH02103434A (en) | 1988-10-13 | 1988-10-13 | Method for measuring strain distribution in longitudinal direction of optical fiber cable and apparatus and optical fiber used in said method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH02103434A true JPH02103434A (en) | 1990-04-16 |
Family
ID=17309374
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP25766388A Pending JPH02103434A (en) | 1988-10-13 | 1988-10-13 | Method for measuring strain distribution in longitudinal direction of optical fiber cable and apparatus and optical fiber used in said method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02103434A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0638795A2 (en) * | 1993-08-10 | 1995-02-15 | AT&T Corp. | Remote sensing in optical fiber networks |
| GB2376293A (en) * | 2001-06-04 | 2002-12-11 | Bookham Technology Plc | Determining polarisation dependent power loss in an optical device |
| JP2007256978A (en) * | 2007-06-04 | 2007-10-04 | Furukawa Electric Co Ltd:The | Method of manufacturing optical fiber |
| JP2011158330A (en) * | 2010-01-29 | 2011-08-18 | Nippon Telegr & Teleph Corp <Ntt> | Apparatus and method for measurement of optical path |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62207927A (en) * | 1986-03-10 | 1987-09-12 | Yokogawa Electric Corp | Optical fiber measuring instrument |
-
1988
- 1988-10-13 JP JP25766388A patent/JPH02103434A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62207927A (en) * | 1986-03-10 | 1987-09-12 | Yokogawa Electric Corp | Optical fiber measuring instrument |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0638795A2 (en) * | 1993-08-10 | 1995-02-15 | AT&T Corp. | Remote sensing in optical fiber networks |
| EP0638795B1 (en) * | 1993-08-10 | 1998-05-06 | AT&T Corp. | Remote sensing in optical fiber networks |
| GB2376293A (en) * | 2001-06-04 | 2002-12-11 | Bookham Technology Plc | Determining polarisation dependent power loss in an optical device |
| JP2007256978A (en) * | 2007-06-04 | 2007-10-04 | Furukawa Electric Co Ltd:The | Method of manufacturing optical fiber |
| JP2011158330A (en) * | 2010-01-29 | 2011-08-18 | Nippon Telegr & Teleph Corp <Ntt> | Apparatus and method for measurement of optical path |
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