JPH0354291B2 - - Google Patents
Info
- Publication number
- JPH0354291B2 JPH0354291B2 JP4049784A JP4049784A JPH0354291B2 JP H0354291 B2 JPH0354291 B2 JP H0354291B2 JP 4049784 A JP4049784 A JP 4049784A JP 4049784 A JP4049784 A JP 4049784A JP H0354291 B2 JPH0354291 B2 JP H0354291B2
- Authority
- JP
- Japan
- Prior art keywords
- light
- optical fiber
- mode coupling
- stimulated raman
- wavelength
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000001069 Raman spectroscopy Methods 0.000 claims description 43
- 230000008878 coupling Effects 0.000 claims description 29
- 238000010168 coupling process Methods 0.000 claims description 29
- 238000005859 coupling reaction Methods 0.000 claims description 29
- 239000013307 optical fiber Substances 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 10
- 230000010287 polarization Effects 0.000 claims description 6
- 238000000691 measurement method Methods 0.000 claims description 2
- 230000003287 optical effect Effects 0.000 description 14
- 239000000835 fiber Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000008033 biological extinction Effects 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 230000001427 coherent effect Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 230000003321 amplification Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 238000004891 communication Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 230000001131 transforming effect Effects 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
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Testing Of Optical Devices Or Fibers (AREA)
- Light Guides In General And Applications Therefor (AREA)
- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Description
【発明の詳細な説明】
〔技術分野〕
本発明は、光後方散乱法を偏波保持フアイバに
適用して誘導ラマン散乱の長手方向への非線形モ
ード結合量を正確に測定する方法に関するもので
ある。[Detailed Description of the Invention] [Technical Field] The present invention relates to a method for accurately measuring the amount of nonlinear mode coupling in the longitudinal direction of stimulated Raman scattering by applying an optical backscattering method to a polarization-maintaining fiber. .
〔従来技術〕
従来、光フアイバ中の誘導ラマン散乱がどのよ
うに光フアイバ中で発生するのかを測定するため
には、第１図に示す測定系を用いている。すなわ
ち、光パルス光源１からの光パルスを、偏光子２
およびビームスプリツタ３を経た後に偏波保持光
フアイバ４に入射する。この光フアイバ４からの
後方散乱光はビームスプリツタ３を経て検光子５
および分光器６を通過した後、光検出器７により
検出される。偏光子２および検光子５は直交ニコ
ルに配置され、入射端でのフレネル反射を除去す
る。なお、ここで分光器６を用いているのは、誘
導ラマン光およびレーザ光の波長選択を行うため
である。光検出器７で検出された信号は信号処理
部８で処理され、最終的に表示部９に出力され
る。[Prior Art] Conventionally, a measurement system shown in FIG. 1 has been used to measure how stimulated Raman scattering occurs in an optical fiber. That is, the optical pulse from the optical pulse light source 1 is transferred to the polarizer 2.
After passing through the beam splitter 3, the beam enters the polarization maintaining optical fiber 4. The backscattered light from the optical fiber 4 passes through the beam splitter 3 to the analyzer 5.
After passing through a spectrometer 6, it is detected by a photodetector 7. Polarizer 2 and analyzer 5 are arranged in crossed Nicols to eliminate Fresnel reflections at the input end. Note that the reason why the spectroscope 6 is used here is to select the wavelengths of the stimulated Raman light and laser light. The signal detected by the photodetector 7 is processed by the signal processing section 8 and finally output to the display section 9.
入力光パルスが弱い場合にかかる構成により得
られた後方散乱光を第２図Ａに示す。この場合に
は誘導ラマンが発生していないので、分光器６の
波長は入射光パルスの波長に設定して、その波長
の光を取り出す。ここでは、光フアイバの損失で
決まる指数関数的減衰波形Ａが観測される。Ｂは
出力端面でのフレネル反射による後方散乱光を示
す。 FIG. 2A shows the backscattered light obtained by this configuration when the input optical pulse is weak. In this case, since stimulated Raman is not generated, the wavelength of the spectroscope 6 is set to the wavelength of the incident light pulse, and light of that wavelength is extracted. Here, an exponential decay waveform A determined by the loss of the optical fiber is observed. B shows backscattered light due to Fresnel reflection at the output end face.
入射パルスのパワーを増加すると、誘導ラマン
が発生し、フアイバ長手方向において、第２図Ｂ
に示すように、その増幅Ｃおよび減衰Ｄがなされ
る。これによると後方散乱波形の初期部での誘導
ラマン散乱の増幅の様子がよくわかり、対数変換
を行なうと直線で表わされ、その傾きから誘導ラ
マン散乱の利得がわかる。 Increasing the power of the incident pulse generates stimulated Raman, which in the longitudinal direction of the fiber is shown in Figure 2B.
The amplification C and attenuation D are performed as shown in FIG. This clearly shows how the stimulated Raman scattering is amplified in the initial part of the backscattered waveform, and when logarithmically transformed, it is expressed as a straight line, and the gain of the stimulated Raman scattering can be determined from its slope.
しかし、この方法では、偏波保持光フアイバの
長手方向に沿つて、２つの主軸（ｘおよびｙ軸）
の間での誘導ラマン散乱の結合がどのように生じ
ているかは測定できない。特に、偏波保持光フア
イバを用いる場合、ｘ軸からの誘導ラマン光がｙ
軸方向へどのように結合していくかを知ることが
コヒーレント伝送等においては非常に重要である
が、これまではそれを測定できる方法はなかつ
た。このような誘導ラマン光のｙ軸方向への結合
は伝送後の信号光の消光比の劣化をもたらし、コ
ヒーレント伝送にとつて重大な問題である。 However, in this method, two principal axes (x and y axes) are
It is not possible to measure how the coupling of stimulated Raman scattering occurs between the two. In particular, when using a polarization-maintaining optical fiber, the stimulated Raman light from the x-axis
Knowing how the coupling occurs in the axial direction is extremely important in coherent transmission, but until now there has been no method for measuring this. Such coupling of stimulated Raman light in the y-axis direction causes deterioration of the extinction ratio of signal light after transmission, which is a serious problem for coherent transmission.
さらにまた、各主軸方向での誘導ラマン散乱の
発生の波長分布は、光フアイバ出力端で容易に測
定できるが、長手方向にわたつて偏波保持光フア
イバ内部でどのようにラマン形の非線形モード結
合が生じているかはこれまで測定できなかつた。 Furthermore, although the wavelength distribution of stimulated Raman scattering occurrence in each principal axis direction can be easily measured at the output end of an optical fiber, it is important to understand how Raman-shaped nonlinear mode coupling occurs inside a polarization-maintaining optical fiber over its longitudinal direction. Until now, it has not been possible to measure whether this is occurring.
そこで、本発明の目的は、これらの欠点を解決
し、偏波保持光フアイバの両主軸から２種類の誘
導ラマン散乱信号の比率を求め、その大きさから
ラマン形非線形モード結合量を測定する方法を提
供することにある。
Therefore, the purpose of the present invention is to solve these drawbacks and provide a method for determining the ratio of two types of stimulated Raman scattering signals from both principal axes of a polarization-maintaining optical fiber and measuring the amount of Raman nonlinear mode coupling from the magnitude thereof. Our goal is to provide the following.
かかる目的を達成するために、本発明は、光パ
ルスを偏波保持光フアイバに入射し、該光フアイ
バの２つの直交する主軸方向からの後方散乱光の
うちの誘導ラマン散乱光の波長域の光を分光器を
介して順次に検出し、これら検出された光の強度
の比率を求めることにより、前記光フアイバで発
生する誘導ラマン散乱光の光フアイバ長手手向に
ついての偏波モード結合の状態を測定することを
特徴とする。
In order to achieve such an object, the present invention injects a light pulse into a polarization-maintaining optical fiber, and calculates the wavelength range of stimulated Raman scattered light among backscattered light from two orthogonal principal axes of the optical fiber. By sequentially detecting light through a spectrometer and determining the ratio of the intensities of these detected lights, the state of polarization mode coupling of the stimulated Raman scattered light generated in the optical fiber in the longitudinal direction of the optical fiber can be determined. It is characterized by measuring.
ここで、前記分光器の設定波長を誘導ラマン散
乱の中心波長に設定し、各ラマン波長での非線形
モード結合を測定することができる。 Here, the set wavelength of the spectrometer is set to the center wavelength of stimulated Raman scattering, and nonlinear mode coupling at each Raman wavelength can be measured.
〔実施例〕
以下に図面を参照して本発明を詳細に説明す
る。[Example] The present invention will be described in detail below with reference to the drawings.
第３図は本発明の１実施例であつて、ここに、
１は光パルス光源（例えばYAGレーザ、F+セン
ターレーザ）、２は偏光子、３はビームスプリツ
タ、４は被測定偏波保持光フアイバ、５は検光
子、６は分光器、７は光検出器、８は信号処理
部、９は表示部である。１０は光スイツチングを
行なうための超音波光偏向素子、１１は偏向素子
１０を駆動するための電気回路および遅延回路、
１２は光源１を駆動するための電気パルス発生器
である。 FIG. 3 shows one embodiment of the present invention, where:
1 is an optical pulse light source (e.g. YAG laser, F + center laser), 2 is a polarizer, 3 is a beam splitter, 4 is a polarization-maintaining optical fiber to be measured, 5 is an analyzer, 6 is a spectrometer, 7 is a light source A detector, 8 a signal processing section, and 9 a display section. 10 is an ultrasonic optical deflection element for performing optical switching; 11 is an electric circuit and a delay circuit for driving the deflection element 10;
12 is an electric pulse generator for driving the light source 1.
本発明方法においては、まず、電気パルス発生
器１２からの電気パルスにより光源１を駆動し、
そこから発生する光パルスを偏光子２およびビー
ムスプリツタ３を経て、偏波保持光フアイバ４の
主軸のうちｘ軸方向に入射させる。光パルスはこ
の光フアイバ４中を伝搬し、後方散乱光を発生す
る。光パルス強度が弱ければ入射光と同一波長の
後方散乱光が観測される。パルス強度が強くなる
と、誘導ラマン散乱により、波長のシフトした後
方散乱光が観測される。 In the method of the present invention, first, the light source 1 is driven by an electric pulse from the electric pulse generator 12,
The light pulses generated therefrom pass through a polarizer 2 and a beam splitter 3 and are made to enter the polarization-maintaining optical fiber 4 in the x-axis direction of its main axis. The light pulse propagates through this optical fiber 4 and generates backscattered light. If the optical pulse intensity is weak, backscattered light with the same wavelength as the incident light is observed. When the pulse intensity increases, backscattered light with a shifted wavelength is observed due to stimulated Raman scattering.
ここで、入射光パルスのｘ軸方向の後方散乱光
をPL bx、ｙ軸方向の後方散乱光をPL byとし、誘導ラ
マン散乱により発生したストークス光のｘ軸方向
の光をPS bx、ｙ軸方向の光をPS byとする。なお、簡
単のために、誘導ラマン散乱は１次ストークスの
みとし、波長選択は分光器６で行なう。また、
PL bx，PL byの波長とPS bx，PS byの波長とはラマンシフ
ト量だけ異なる。PL bxは偏光子２と検光子５の偏
光方向が同一の場合である。従つて、光フアイバ
４の入射端面でのフレネル反射（散乱レベルに比
べて40dB程度大きい）をも一緒に受光すること
になるので、超音波光偏向器１０を用いて入射端
でのフレネル反射光のマスキングを行ない、PL bx
を無歪み状態で光検出器７により受光する。な
お、光マスキングのタイミングは駆動回路１１に
より制御する。後方散乱光は微弱であるので、
Ｓ／Ｎ比改善等の信号処理を行うのが好適である。 Here, the backscattered light in the x-axis direction of the incident light pulse is P L bx , the backscattered light in the y-axis direction is P L by , and the light in the x-axis direction of Stokes light generated by stimulated Raman scattering is P S bx , the light in the y-axis direction is P S by . For simplicity, only first-order Stokes is used for stimulated Raman scattering, and wavelength selection is performed by the spectrometer 6. Also,
The wavelengths of P L bx and P L by differ from those of P S bx and P S by by the amount of Raman shift. P L bx is a case where the polarization directions of the polarizer 2 and the analyzer 5 are the same. Therefore, since the Fresnel reflection (approximately 40 dB higher than the scattering level) at the input end of the optical fiber 4 is also received, the ultrasonic optical deflector 10 is used to detect the Fresnel reflected light at the input end. P L bx
is received by the photodetector 7 in an undistorted state. Note that the timing of optical masking is controlled by the drive circuit 11. Since the backscattered light is weak,
It is preferable to perform signal processing such as improving the S/N ratio.
次いで、同様の測定を検光子５を90゜回転させ
てｙ軸方向について行う。すなわち、光フアイバ
４の他方の主軸すなわちｙ軸方向からの信号PL by
を測定する。 Next, similar measurements are performed in the y-axis direction by rotating the analyzer 5 by 90 degrees. That is, the signal P L by from the other main axis of the optical fiber 4, that is, from the y-axis direction
Measure.
このように順次に測定した両信号光PL bxおよび
PL byを信号処理装置１１に供給し、ここで両信号
光の強度の比率を求め、その結果を、誘導ラマン
散乱光の光フアイバ長手方向についての偏波モー
ド結合係数および消光比などを表示装置１２に表
示する。 Both signal lights P L bx and
PL by is supplied to the signal processing device 11, where the ratio of the intensity of both signal lights is determined, and the results are displayed as the polarization mode coupling coefficient and extinction ratio of the stimulated Raman scattered light in the longitudinal direction of the optical fiber. Displayed on the device 12.
ここで、光源１からの入射光を強くし、かつ分
光器６を誘導ラマン波長に設定することにより、
PS bxおよびPS byを測定することができる。 Here, by increasing the intensity of the incident light from the light source 1 and setting the spectrometer 6 to the stimulated Raman wavelength,
P S bx and P S by can be measured.
ここで、ｘ軸方向でのレーザ入力をPL x、スト
ークス光をPS x、またｙ軸方向でのレーザ入力を
PL y、ストークス光をPS xとすると、それらの量は
次の結合方程式を満足する。 Here, the laser input in the x-axis direction is P L x , the Stokes beam is P S x , and the laser input in the y-axis direction is
When P L y and Stokes light are P S x , their quantities satisfy the following coupling equation.
dPL／x／dz＝−γPS xPL x−γ′PS yPL x＋ｈ（PL y−PL x）
−αPL x(1)
dPS／x／dz＝γPL xPS x＋γ′PL yPS x＋ｈ（PS y−PS x）−
αPS x(2)
dPL／y／dz＝−γPS yPL y−γ′PS xPL y＋ｈ（PL x−PL y）
−αPL y(3)
dPS／y／dz＝γPL yPS y＋γ′PL xPS y＋ｈ（PS x−PS y）−
αPS y(4)
ここで、γは偏波が同一方向でのラマン利得、
γ′は直交方向でのラマン利得、ｈは線形なモード
結合係数、αはフアイバ損失である。dP L / x / dz = −γP S x P L x −γ′P S y P L x +h (P L y −P L x )
−αP L x (1) dP S / x / dz = γP L x P S x + γ′P L y P S x +h(P S y −P S x )−
αP S x (2) dP L / y / dz = −γP S y P L y −γ′P S x P L y +h (P L x −P L y )
−αP L y (3) dP S / y / dz = γP L y P S y + γ′P L x P S y +h(P S x −P S y )−
αP S y (4) Here, γ is the Raman gain when the polarization is in the same direction,
γ' is the Raman gain in the orthogonal direction, h is the linear mode coupling coefficient, and α is the fiber loss.
式(1)〜(4)において、右辺の第１、２項は誘導ラ
マンによる非線形モード結合であり、第３項は線
形なモード結合、第４項はフアイバ損失を示して
いる。従つて、上式は一般化したモード結合の関
係を示している。 In equations (1) to (4), the first and second terms on the right side are nonlinear mode coupling due to stimulated Raman, the third term is linear mode coupling, and the fourth term is fiber loss. Therefore, the above equation shows a generalized mode coupling relationship.
さて、上式を参考にしながら、モード結合の様
子を説明する。 Now, referring to the above equation, we will explain the state of mode coupling.
非線形モード結合時の後方散乱の様子を第４図
Ａ〜Ｆに示す。ここでは、光パルスはPL xで与え、
PL y（Ｏ）＝０としている。第４図ＡおよびＢには、
入射パルスが微弱な場合、すなわち線形領域での
同方向（ｘ軸）後方散乱光および直交方向（ｙ
軸）後方散乱光を示す。第４図Ａに示す尖頭波形
は出力端面でのフレネル反射による後方散乱光で
ある。 The state of backscattering during nonlinear mode coupling is shown in FIGS. 4A to 4F. Here, the light pulse is given by P L x ,
P L y (O)=0. In Figures 4A and B,
When the incident pulse is weak, i.e. backscattered light in the same direction (x axis) in the linear region and in the orthogonal direction (y
Axis) indicates backscattered light. The peak waveform shown in FIG. 4A is backscattered light due to Fresnel reflection at the output end face.
入射パルスを強くすると、誘導ラマン散乱によ
り非線形モード結合が発生し、第４図Ａは第４図
Ｃの実線部に変化し、第４図Ｂは第４図Ｅに変化
する。いずれにおいても、後方散乱光のレベルは
増加するとともに、その傾きも変化している。こ
の変化はストークス光、すなわちPS bx，PS byの発生
に起因している。 When the incident pulse is strengthened, nonlinear mode coupling occurs due to stimulated Raman scattering, and FIG. 4A changes to the solid line part in FIG. 4C, and FIG. 4B changes to FIG. 4E. In both cases, the level of backscattered light increases and its slope also changes. This change is caused by the generation of Stokes light, that is, P S bx and P S by .
分光器６の波長をレーザパルスの波長からスト
ークス波長に設定して得られた同一方向（ｘ軸）
の誘導ラマン成分をPS bx、直交方向（ｙ軸）の成
分をPS byとし、その波形を第４図ＤおよびＦにそ
れぞれ示す。これより、徐々に誘導ラマン散乱が
増幅されていく様子がよくわかる。第４図Ｄおよ
びＦの立ち上がり部分を対数変換することにより
その傾きからラマンの利得係数γおよびγ′が求ま
る。第４図ＤとＦとを比べると、増幅の割合いに
ついては、第４図Ｆの方が小さいのは、直交方向
でのラマン利得係数γ′がγに比べて小さいためで
ある。 The same direction (x-axis) obtained by setting the wavelength of the spectrometer 6 from the wavelength of the laser pulse to the Stokes wavelength
The stimulated Raman component of is P S bx and the component in the orthogonal direction (y axis) is P S by , and their waveforms are shown in FIGS. 4D and F, respectively. This clearly shows how stimulated Raman scattering is gradually amplified. By logarithmically transforming the rising portions of D and F in FIG. 4, the Raman gain coefficients γ and γ' can be determined from the slope thereof. Comparing FIGS. 4D and 4F, the amplification ratio is smaller in FIG. 4F because the Raman gain coefficient γ' in the orthogonal direction is smaller than γ.
本発明では、このようにして得られた種々の後
方散乱光の比率を求めることにより、非線形モー
ド結合の様子を求める。その様子を第５図Ａ〜Ｅ
により説明する。第５図Ａは入力パルスが弱い線
形領域の場合でのPL by／PL bxの変化を示す。その傾
きは2hで与えられ、モード結合係数を求まる。 In the present invention, the state of nonlinear mode coupling is determined by determining the ratio of the various backscattered lights obtained in this manner. The situation is shown in Figure 5 A to E.
This is explained by: FIG. 5A shows the change in P L by /P L bx when the input pulse is in a weak linear region. Its slope is given by 2h, and the mode coupling coefficient is found.
入射パワーを増大して誘導ラマンが発生すると
（非線形領域）、パワーの増加とともに第５図Ｂに
示すように変化する。これは、誘導ラマン散乱に
よりPL bx（ｚ）が減少し、さらに急激にPL by（ｚ）も
減少するためである。 When stimulated Raman is generated by increasing the incident power (nonlinear region), it changes as shown in FIG. 5B as the power increases. This is because P L bx (z) decreases due to stimulated Raman scattering, and P L by (z) also decreases rapidly.
第５図Ｃにはｘ軸方向でのレーザ光波長におけ
る後方散乱パワーPL bxに対する誘導ラマン散乱の
変化PS bxの割合いを示す。入射パワーを増加する
につれて入射端近傍でラマンが立ち上がる。 FIG. 5C shows the ratio of the change in stimulated Raman scattering P S bx to the backscattered power P L bx at the laser light wavelength in the x-axis direction. As the incident power increases, Raman rises near the incident end.
第５図Ｄには分光器６により波長選択して得ら
れるラマン波長での散乱光PS byPS bxを示す。入射パ
ワーを増加するにつれて、PS bx（ｚ）の方がPS by
（ｚ）に比べて早く立ち上がり、大きな値となる
ため、PS by／PS bxは急激に小さくなる。 FIG. 5D shows scattered light P S by P S bx at the Raman wavelength obtained by wavelength selection by the spectroscope 6. As the incident power increases, P S bx (z) becomes smaller than P S by
Since it rises earlier and takes on a larger value than (z), P S by /P S bx becomes smaller rapidly.
第５図Ｅは分光器６をはずして直交する２軸
（ｘ，ｙ）間の後方散乱パワーの比率（PL by＋
PS by）／（PL bx＋PS bx）を求めたものである。入力
が増加するにつれて、PS byの増加量がPL bx＋PS bxの
変化に比べて大きいので、パワーの増加とともに
モード結合量は増加することになる。 Figure 5E shows the ratio of backscattered power (P L by +
P S by )/(P L bx + P S bx ). As the input increases, the amount of increase in P S by is larger than the change in P L bx +P S bx , so the amount of mode coupling increases as the power increases.
このように、第５図Ｂ〜Ｅにおいて、光パルス
パワーの増加とともにｘ，ｙ軸間での非線形モー
ド結合がどのように長手方向に変化していくのか
よくわかる。 Thus, in FIGS. 5B to 5E, it can be clearly seen how the nonlinear mode coupling between the x and y axes changes in the longitudinal direction as the optical pulse power increases.
本発明の測定方法によれば、個別の光フアイバ
について入射エネルギの増大に伴う誘導ラマン光
の発生と、モード結合の長手方向の分布を知るこ
とができるので、個別の光フアイバの特性とし
て、実質的な消光比の劣化をもたらさない入力限
界を知ることができる。 According to the measurement method of the present invention, it is possible to know the generation of stimulated Raman light as the incident energy increases and the distribution of mode coupling in the longitudinal direction for individual optical fibers. It is possible to know the input limit that does not cause deterioration of the extinction ratio.
以上説明したように、本発明によれば、偏波保
持光フアイバ中の誘導ラマン散乱形の非線形モー
ド結合の様子を、光後方散乱法を用いて、２つの
直交主軸における後方散乱光の比率から求めるこ
とができる。これによれば、従来測定できなかつ
た非線形モード結合の様子がフアイバの長手方向
にわたつて判る利点がある。さらに加えて、本発
明によれば、個別の光フアイバについて入力限界
を求めることができるから、コヒーレント通信に
おける入力限界を知る上でも有効である。
As explained above, according to the present invention, the state of stimulated Raman scattering type nonlinear mode coupling in a polarization-maintaining optical fiber can be determined from the ratio of backscattered light in two orthogonal principal axes using an optical backscattering method. You can ask for it. This has the advantage that the state of nonlinear mode coupling, which could not be measured conventionally, can be seen over the longitudinal direction of the fiber. Furthermore, according to the present invention, it is possible to determine the input limit for each optical fiber, which is also effective in knowing the input limit in coherent communication.
第１図は従来のラマン形後方散乱法の説明図、
第２図ＡおよびＢは第１図の方法により得られる
後方散乱信号を示す線図、第３図は本発明装置の
一実施例を示す構成図、第４図Ａ〜Ｆは第３図の
測定系により得られた後方散乱光の説明図、第５
図Ａ〜Ｅは本発明により測定した非線形モード結
合状態の種々の態様を示す線図である。
１…光パルス光源、２…偏光子、３…ビームス
プリツタ、４…被測定偏波保持光フアイバ、５…
検光子、６…分光器、７…光検出器、８…信号処
理部、９…表示器、１０…超音波光偏向器、１１
…超音波光偏向器用駆動回路および遅延回路、１
２…電気パルス発生器。
Figure 1 is an explanatory diagram of the conventional Raman backscattering method.
2A and 2B are diagrams showing backscattered signals obtained by the method shown in FIG. 1, FIG. Explanatory diagram of backscattered light obtained by the measurement system, 5th
Figures A to E are diagrams showing various aspects of nonlinear mode coupling states measured according to the present invention. DESCRIPTION OF SYMBOLS 1... Optical pulse light source, 2... Polarizer, 3... Beam splitter, 4... Polarization-maintaining optical fiber to be measured, 5...
Analyzer, 6... Spectrometer, 7... Photodetector, 8... Signal processing section, 9... Display device, 10... Ultrasonic light deflector, 11
...Ultrasonic optical deflector drive circuit and delay circuit, 1
2...Electric pulse generator.
Claims (1)
光フアイバの２つの直交する主軸方向からの後方
散乱光のうちの誘導ラマン散乱光の波長域の光を
分光器を介して順次に検出し、これら検出された
光の強度の比率を求めることにより、前記光フア
イバで発生する誘導ラマン散乱光の光フアイバ長
手方向についての偏波モード結合の状態を測定す
ることを特徴とする非線形モード結合状態の測定
方法。 ２ 特許請求の範囲第１項記載の測定方法におい
て、前記分光器の設定波長を誘導ラマン散乱の中
心波長に設定し、各ラマン波長での非線形モード
結合を測定することを特徴とする非線形モード結
合状態の測定方法。[Claims] 1. A light pulse is input into a polarization-maintaining optical fiber, and among the backscattered light from two orthogonal principal axes of the optical fiber, light in the wavelength range of stimulated Raman scattered light is detected using a spectrometer. The state of polarization mode coupling of the stimulated Raman scattered light generated in the optical fiber in the longitudinal direction of the optical fiber is measured by sequentially detecting the light through the optical fiber and determining the ratio of the intensities of these detected lights. A method for measuring the state of nonlinear mode coupling. 2. Nonlinear mode coupling in the measurement method according to claim 1, characterized in that the set wavelength of the spectrometer is set to the center wavelength of stimulated Raman scattering, and nonlinear mode coupling at each Raman wavelength is measured. How to measure condition.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4049784A JPS60185132A (en) | 1984-03-05 | 1984-03-05 | Measuring method of coupling state in nonlinear mode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4049784A JPS60185132A (en) | 1984-03-05 | 1984-03-05 | Measuring method of coupling state in nonlinear mode |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60185132A JPS60185132A (en) | 1985-09-20 |
| JPH0354291B2 true JPH0354291B2 (en) | 1991-08-19 |
Family
ID=12582200
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4049784A Granted JPS60185132A (en) | 1984-03-05 | 1984-03-05 | Measuring method of coupling state in nonlinear mode |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS60185132A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3606558A1 (en) * | 1986-02-28 | 1987-09-03 | Philips Patentverwaltung | MEASURING ARRANGEMENT FOR DETERMINING THE LENGTH-DEPENDENT DAMPING OF MONOMODE LIGHTWAVE GUIDES AFTER THE BACKFLOW METHOD |
| KR101305326B1 (en) * | 2006-12-20 | 2013-09-06 | 엘지전자 주식회사 | Air conditioner |
| CN106895959B (en) * | 2017-04-17 | 2019-01-25 | 吉林大学 | A kind of less fundamental mode optical fibre Mode Coupling measuring device based on two-photon lantern and less fundamental mode optical fibre circulator |
-
1984
- 1984-03-05 JP JP4049784A patent/JPS60185132A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60185132A (en) | 1985-09-20 |
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