JP2011209121A - Optical fiber distribution type temperature measuring device - Google Patents
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本発明は、光ファイバ増幅器から出力される光パルス列を入射する光ファイバから得られる後方ラマン散乱光よりストークス光とアンチストークス光に分波抽出して電気信号に変換した夫々の受光信号のレベルを、前記光ファイバ増幅器から出力される光パルス列のパワー変動に応じて補正するレベル補正部と、レベル補正された夫々の受光信号に対して相関処理を施して復調する相関処理部と、夫々の相関処理部の出力に基づいて温度信号を算出する温度演算部と、を具備する光ファイバ分布型温度測定装置に関するものである。 In the present invention, the level of each received light signal, which is demultiplexed into Stokes light and anti-Stokes light from the back Raman scattered light obtained from the incident optical fiber and converted into an electrical signal, is converted from the optical pulse train output from the optical fiber amplifier. A level correction unit that corrects the optical pulse train output from the optical fiber amplifier according to power fluctuations, a correlation processing unit that performs correlation processing on each level-corrected received light signal, and demodulates the received light signals. The present invention relates to an optical fiber distributed temperature measuring device including a temperature calculation unit that calculates a temperature signal based on an output of a processing unit.
図４は、光ファイバへのパルス入射光に対する散乱光スペクトルを説明する模式図である。入射光と同一波長でレイリー散乱光が発生し、入射光と所定波長離れた長波側及び短波側にブルリアン散乱光が発生し、入射光と更に所定波長離れた長波側及び短波側にラマン散乱光が発生する。長波側のラマン散乱光はストークス光、短波側のラマン散乱光はアンチストークス光と称される。 FIG. 4 is a schematic diagram for explaining a scattered light spectrum with respect to pulse incident light on an optical fiber. Rayleigh scattered light is generated at the same wavelength as the incident light, Brillouin scattered light is generated on the long wave side and the short wave side separated from the incident light by a predetermined wavelength, and Raman scattered light is generated on the long wave side and the short wave side further separated from the incident light by a predetermined wavelength. Will occur. The Raman scattered light on the long wave side is called Stokes light, and the Raman scattered light on the short wave side is called anti-Stokes light.
光ファイバ分布型温度測定装置の原理は、温度依存性のある後方ラマン散乱光の２成分（ストークス光、アンチストークス光）の強度を測定し、その強度比から温度を算出する装置である。 The principle of the optical fiber distributed temperature measuring device is a device that measures the intensity of two components (Stokes light and anti-Stokes light) of temperature-dependent backward Raman scattered light and calculates the temperature from the intensity ratio.
図５は、ストークス光とアンチストークス光による温度演算を説明する模式図である。図５（Ａ）に示すストークス光強度の測定値ＬＡと（Ｂ）に示すアンチストークス光強度の測定値ＬＢの強度比の演算に基づいて（Ｃ）に示す距離に対する温度Ｔを測定する。このような原理に基づく光ファイバ分布型温度測定装置については、特許文献１に詳細な技術開示がある。 FIG. 5 is a schematic diagram illustrating temperature calculation using Stokes light and anti-Stokes light. Based on the calculation of the intensity ratio between the measured value LA of Stokes light intensity shown in FIG. 5A and the measured value LB of anti-Stokes light intensity shown in FIG. 5B, the temperature T with respect to the distance shown in FIG. Patent Document 1 discloses a detailed technical disclosure of an optical fiber distributed temperature measuring device based on such a principle.
図６は、従来の光ファイバ分布型温度測定装置の構成例を示す機能ブロック図である。温度測定対象に所定長に渡り敷設され、温度センサとして機能する光ファイバ１の一端側より、レーザ光源２の出力に対して符号生成回路３で符号変調した光パルス列を、光ファイバ増幅器４、光カプラ５、サーキュレータで構成される波長分波器６を介して入射する。 FIG. 6 is a functional block diagram showing a configuration example of a conventional optical fiber distributed temperature measuring device. An optical pulse train obtained by code-modulating the output of the laser light source 2 by the code generation circuit 3 from one end side of the optical fiber 1 that is laid over the temperature measurement object for a predetermined length and functions as a temperature sensor, The light enters through a wavelength demultiplexer 6 including a coupler 5 and a circulator.
光パルスを光ファイバ１に入射させて得られる後方散乱光を波長分波器６で後方ラマン散乱光の２成分であるストークス光ＬＡ、アンチストークス光ＬＢに分波して抽出する。抽出されたストークス光ＬＡ、アンチストークス光ＬＢは、受光回路で電気信号ＥＡ及びＥＢに変換され、増幅回路９を介してＡ／Ｄ変換回路１０でデジタル信号に変換される。 The backscattered light obtained by making the optical pulse incident on the optical fiber 1 is separated and extracted by the wavelength demultiplexer 6 into Stokes light LA and anti-Stokes light LB which are two components of the back Raman scattered light. The extracted Stokes light LA and anti-Stokes light LB are converted into electric signals EA and EB by a light receiving circuit, and converted into a digital signal by an A / D conversion circuit 10 via an amplifier circuit 9.
タイミング発生回路１１は、Ａ／Ｄ変換回路１０及び符号生成回路３にタイミング信号を供給する。符号化された光パルス列に対応して測定される電気信号ＥＡ及びＥＢのデジタル変換信号は、平均化処理部１２で平均化処理され、レベル補正部１２に入力する。 The timing generation circuit 11 supplies a timing signal to the A / D conversion circuit 10 and the code generation circuit 3. The digital conversion signals of the electrical signals EA and EB measured corresponding to the encoded optical pulse train are averaged by the averaging processor 12 and input to the level corrector 12.
光ファイバ増幅器４は、一般にＥＤＦＡ（Erbium Doped Fiber Amplifier）で実現される。ＥＤＦＡは、測定のダイナミックレンジを改善させるために備えるが、その出力特性により光パルス列のパワーが変動して不均一となり、温度測定の精度に影響を及ぼす。 The optical fiber amplifier 4 is generally realized by an EDFA (Erbium Doped Fiber Amplifier). An EDFA is provided to improve the dynamic range of measurement, but the power of the optical pulse train fluctuates due to its output characteristics and becomes non-uniform, affecting the accuracy of temperature measurement.
このパワー変動に起因する出力特性ａをフォトダイオード７で検出し、レベル補正部１３において出力特性aに応じた係数a1,a2,a3,…aNを各パルス列信号に乗算することによってレベル補正を実行し、波形歪や雑音を抑制する。 The output characteristic a resulting from this power fluctuation is detected by the photodiode 7, and the level correction unit 13 performs level correction by multiplying each pulse train signal by coefficients a1, a2, a3,... AN corresponding to the output characteristic a. Suppresses waveform distortion and noise.
レベル補正部１３により補正された信号ＳＡ（s1,s2,s3,…sN）及びＳＢ（s1,s2,s3,…sN）は、相関処理部１４Ａ及び１４Ｂに入力する。相関処理により復調された信号ＤＡ（d1,d2,d3,…dN）及びＤＢ（d1,d2,d3,…dN）は、温度演算部１５に入力され、算出された温度信号Ｔが温度表示部１６に渡されて表示され、または上位装置に通知される。 The signals SA (s1, s2, s3,... SN) and SB (s1, s2, s3,... SN) corrected by the level correction unit 13 are input to the correlation processing units 14A and 14B. The signals DA (d1, d2, d3,... DN) and DB (d1, d2, d3,... DN) demodulated by the correlation processing are input to the temperature calculation unit 15, and the calculated temperature signal T is input to the temperature display unit. 16 is displayed for display or notified to the host device.
相関処理部１４Ａ及び１４Ｂは、光パルス列の数に対応したＮ個のシフトレジスタR1,R2,R3,…RNと、これらシフトレジスタの出力に相関係数k1,k2,k3,…kNを乗算する乗算手段M1,M2,M3,…MNと、これら乗算手段の出力を加算して復調した信号を出力する加算手段Ｓよりなる。相関係数には入力する符号と同じものを使用し、入力した符号と整合したとき最大出力信号レベルを得る。 Correlation processing units 14A and 14B multiply N shift registers R1, R2, R3,... RN corresponding to the number of optical pulse trains, and outputs of these shift registers by correlation coefficients k1, k2, k3,. MN and multiplication means M1, M2, M3,... MN, and addition means S for adding the outputs of these multiplication means and outputting a demodulated signal. The same correlation coefficient as the input code is used, and the maximum output signal level is obtained when matching with the input code.
レベル補正部１３及び相関処理部１４の動作の詳細については、信号処理内容が共通する、レイリー散乱光やフレネル反射光を用いる光ファイバ試験装置に関する特許文献２に技術開示がある。 The details of the operations of the level correction unit 13 and the correlation processing unit 14 are disclosed in Patent Document 2 relating to an optical fiber test apparatus using Rayleigh scattered light and Fresnel reflected light, which share the same signal processing content.
従来装置では次のような問題がある。
（１）従来技術のレベル補正手法では、入射するパワーが不均一となる光ファイバ両端部分において段階的に係数を乗算する（特許文献２、図３参照）。段階的に係数を乗算した部分においては波形歪や雑音が抑制されるが、光ファイバ両端以外の部分においては一定の係数を乗算しているのみであるため、波形歪や雑音は抑制されない。従って光ファイバ両端以外の部分が測定対象となるような温度測定の場合、従来技術では波形歪や雑音抑制の効果は少ない。
The conventional apparatus has the following problems.
(1) In the conventional level correction method, the coefficients are multiplied in stages at both ends of the optical fiber where the incident power is non-uniform (see Patent Document 2 and FIG. 3). Waveform distortion and noise are suppressed in the portion where the coefficients are multiplied step by step, but waveform distortion and noise are not suppressed since the portions other than both ends of the optical fiber are only multiplied by a constant coefficient. Therefore, in the case of temperature measurement in which portions other than both ends of the optical fiber are to be measured, the conventional technique has little effect on waveform distortion and noise suppression.
（２）信号対ノイズ比の観点でみると、従来技術ではレベル補正において受光信号に係数を乗算していることから、基本的に補正前後で信号対ノイズ比は変わらず、光ファイバ全体で高精度に測定するには至らない。 (2) From the viewpoint of the signal-to-noise ratio, in the conventional technique, the received light signal is multiplied by a coefficient in the level correction, so that the signal-to-noise ratio basically does not change before and after the correction, and is high throughout the optical fiber. It cannot be measured accurately.
本発明の目的は、光ファイバに入射するパワーが変動しても、光ファイバ全体で信号対ノイズ比を改善し高精度に測定できる光ファイバ分布型温度測定装置を実現することにある。 An object of the present invention is to realize an optical fiber distributed temperature measuring apparatus capable of improving the signal-to-noise ratio and measuring with high accuracy even if the power incident on the optical fiber fluctuates.
このような課題を達成するために、本発明は次の通りの構成になっている。
（１）光ファイバ増幅器から出力される光パルス列を入射する光ファイバから得られる後方ラマン散乱光よりストークス光とアンチストークス光に分波抽出して電気信号に変換した夫々の受光信号のレベルを、前記光ファイバ増幅器から出力される光パルス列のパワー変動に応じて補正するレベル補正部と、レベル補正された夫々の受光信号に対して相関処理を施して復調する相関処理部と、夫々の相関処理部の出力に基づいて温度信号を算出する温度演算部と、を具備する光ファイバ分布型温度測定装置において、
前記夫々の相関処理部で前記光パルス列に対応して設定される係数を、前記光ファイバ増幅器から出力される光パルス列のパワー変動に応じて補正する係数補正手段を備えることを特徴とする光ファイバ分布型温度測定装置。
In order to achieve such a subject, the present invention has the following configuration.
(1) The level of each received light signal that is demultiplexed into Stokes light and anti-Stokes light from the back Raman scattered light obtained from the optical fiber that is incident on the optical pulse train output from the optical fiber amplifier and converted into an electrical signal, A level correction unit that corrects according to power fluctuations of the optical pulse train output from the optical fiber amplifier, a correlation processing unit that performs correlation processing on each level-corrected received light signal, and demodulates the received light signal, and each correlation processing A temperature calculation unit that calculates a temperature signal based on the output of the unit, and an optical fiber distributed temperature measuring device comprising:
An optical fiber comprising coefficient correction means for correcting a coefficient set by each correlation processing unit corresponding to the optical pulse train in accordance with a power fluctuation of the optical pulse train output from the optical fiber amplifier. Distributed temperature measuring device.
（２）前記光ファイバに入射する光パルス列にゴーレイ符号による符号変調を行う符号生成回路を備えることを特徴とする（１）に記載の光ファイバ分布型温度測定装置。 (2) The optical fiber distributed temperature measuring device according to (1), further comprising a code generation circuit that performs code modulation using a Golay code on an optical pulse train incident on the optical fiber.
（３）前記光ファイバ増幅器は、ＥＤＦＡ（Erbium Doped Fiber Amplifier）であることを特徴とする（１）または（２）に記載の光ファイバ分布型温度測定装置。 (3) The optical fiber distributed temperature measuring device according to (1) or (2), wherein the optical fiber amplifier is an EDFA (Erbium Doped Fiber Amplifier).
（４）前記光ファイバ増幅器から出力される光パルス列のパワー変動を予め記憶する記憶手段からの補正情報に基づいて、前記レベル補正部のレベル補正と前記相関処理部の係数補正を実行することを特徴とする（１）乃至（３）のいずれかに記載の光ファイバ分布型温度測定装置。 (4) performing level correction of the level correction unit and coefficient correction of the correlation processing unit based on correction information from a storage unit that stores in advance the power fluctuation of the optical pulse train output from the optical fiber amplifier. The optical fiber distributed temperature measuring device according to any one of (1) to (3).
本発明によれば、従来構成の相関処理部１４Ａ及び１４Ｂにおいて固定で設定されている相関係数k1,k2,k3,…kNを、レベル補正部１３において用いた、光ファイバ増幅器４の出力特性aに応じた係数a1,a2,a3,…aNと同一係数により補正することで、信号対ノイズ比を改善することができる。 According to the present invention, the output characteristics of the optical fiber amplifier 4 using the correlation coefficients k1, k2, k3,... KN fixed in the correlation processing units 14A and 14B of the conventional configuration in the level correction unit 13 are used. The signal-to-noise ratio can be improved by correcting with the same coefficients as the coefficients a1, a2, a3,.
以下本発明を、図面を用いて詳細に説明する。図１は、本発明を適用した光ファイバ分布型温度測定装置の一実施例を示す機能ブロック図である。図４で説明した従来構成と同一要素には同一符号を付して説明を省略する。 Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of an optical fiber distributed temperature measuring device to which the present invention is applied. The same elements as those in the conventional configuration described with reference to FIG.
図１において、本発明を適用した相関処理部を１００Ａ及び１００Ｂで示す。図４で示した従来構成における相関処理部１４Ａ及び１４Ｂとの相違点は、相関係数k1,k2,k3,…kNに対する係数補正手段１０１，１０２，１０３，…１０Ｎを追加した構成にある。 In FIG. 1, the correlation processing units to which the present invention is applied are indicated by 100A and 100B. 4 is different from the correlation processing units 14A and 14B in the conventional configuration in that coefficient correction means 101, 102, 103,... 10N are added to the correlation coefficients k1, k2, k3,.
これら係数補正手段１０１，１０２，１０３，…１０Ｎは、光ファイバ増幅器４のパワー変動に起因する出力特性aに応じた係数a1,a2,a3,…aNを、相関処理部１４Ａ及び１４Ｂの相関係数k1,k2,k3,…kNの設定値に乗算して補正する。 These coefficient correction means 101, 102, 103,... 10N use coefficients a1, a2, a3,... AN corresponding to the output characteristics a caused by power fluctuations of the optical fiber amplifier 4 as phase relationships between the correlation processing units 14A and 14B. Correction is performed by multiplying the set values of the numbers k1, k2, k3,.
各相関処理部１４Ａ及び１４Ｂの最大出力信号レベルは、入力信号s1,s2,s3,…sN、相関係数k1,k2,k3,…kNとすると式（１）で示される。
信号レベル＝(s1×k1)+(s2×k2)+(s3×k3)…+(sN×kN) （１）
The maximum output signal level of each of the correlation processing units 14A and 14B is expressed by Expression (1) when the input signals s1, s2, s3,... SN and the correlation coefficients k1, k2, k3,.
Signal level = (s1 x k1) + (s2 x k2) + (s3 x k3) ... + (sN x kN) (1)
一方、ノイズn1,n2,n3,…nNが入力された場合の出力は、整合しないので平方和となり式（２）で示される。
ノイズレベル＝√｛(n1×k1)2+(n2×k2)2+(n3×k3)2+…+(nN×kN)2｝ （２）
On the other hand, the outputs when noises n1, n2, n3,.
Noise level = √ {(n1 × k1) 2 + (n2 × k2) 2 + (n3 × k3) 2 +… + (nN × kN) 2 } (2)
光ファイバ増幅器４のパワー変動により、相関処理後の信号レベルが減衰し、信号対ノイズ比が劣化する場合がある。本発明では、相関係数k1,k2,k3,…kNに、光ファイバ増幅器４の出力特性aに応じた係数a1,a2,a3,…aNを乗算して補正をすることで、信号対ノイズ比を改善する。これによって、入力信号と相関係数が整合するため、信号対ノイズ比を改善することができる。 Due to the power fluctuation of the optical fiber amplifier 4, the signal level after the correlation processing may be attenuated and the signal-to-noise ratio may be deteriorated. In the present invention, the correlation coefficient k1, k2, k3,... KN is multiplied by the coefficients a1, a2, a3,. Improve the ratio. As a result, the input signal and the correlation coefficient are matched, so that the signal-to-noise ratio can be improved.
具体的に図１に示した相関処理部１００Ａの信号対ノイズ比を算出し、本発明の効果を確認する。通常、光ファイバ分布型温度測定装置の相関処理部への入力信号は、光ファイバ全箇所からの反射信号の重ね合わせであるが、ここでは全箇所中1箇所の反射信号に着目して考える。 Specifically, the signal-to-noise ratio of the correlation processing unit 100A shown in FIG. 1 is calculated to confirm the effect of the present invention. Normally, the input signal to the correlation processing unit of the optical fiber distributed temperature measuring device is a superposition of the reflected signals from all the locations of the optical fiber, but here, the reflected signal at one location in all the locations is considered.
まず、光ファイバ増幅器４のパワー変動の影響がない理想的な場合を考える。相関処理部１００Ａに（1,1,-1,-1,1,-1,1,-1）の符号が入力し、相関係数を符号列と同じとすると、式（１）より最大出力信号レベルは8となる。一方、レベルσのノイズが入力した場合は、式（２）より√８σとなる。よって理想的な相関処理後の信号対ノイズ比は、２.８×１／σとなる。 First, an ideal case where there is no influence of power fluctuation of the optical fiber amplifier 4 will be considered. If the code of (1,1, -1, -1,1, -1,1, -1) is input to the correlation processing unit 100A and the correlation coefficient is the same as that of the code string, the maximum output is obtained from equation (1). The signal level is 8. On the other hand, when noise of level σ is input, √8σ is obtained from equation (2). Therefore, the ideal signal-to-noise ratio after correlation processing is 2.8 × 1 / σ.
次に、光ファイバ増幅器４のパワー変動の影響があり、その出力特性が0.5を底とする指数関数である場合を考える。出力特性によって（1,0.5,-0.25,-0.125,...）が入力され、本発明の補正をしない場合、相関処理後の最大出力信号レベルは式（１）より約２.０となる。ノイズレベルは変わらないので、信号対ノイズ比は、０.７×１／σとなる。 Next, let us consider a case where there is an influence of power fluctuation of the optical fiber amplifier 4 and its output characteristic is an exponential function with a base of 0.5. When (1,0.5, -0.25, -0.125, ...) is input depending on the output characteristics, and the correction according to the present invention is not performed, the maximum output signal level after the correlation processing is about 2.0 from the equation (1). . Since the noise level does not change, the signal-to-noise ratio is 0.7 × 1 / σ.
本発明では、相関係数k1,k2,k3,…kNに、光ファイバ増幅器４の出力特性aに応じた係数a1,a2,a3,…aNを乗算して相関処理を行う。相関係数は（1,0.5,-0.25,-0.125,...）となり、そのときの最大出力信号レベルは式（１）より約１.２となる。 In the present invention, correlation coefficients k1, k2, k3,... KN are multiplied by coefficients a1, a2, a3,... AN corresponding to the output characteristics a of the optical fiber amplifier 4 to perform correlation processing. The correlation coefficient is (1,0.5, -0.25, -0.125, ...), and the maximum output signal level at that time is about 1.2 from the equation (1).
ノイズレベルは、相関係数に応じて式（２）より約１.１σとなる。よって、信号対ノイズ比は１.１×１／σとなり、本発明の補正によって改善が得られることがわかる。 The noise level is about 1.1σ according to equation (2) depending on the correlation coefficient. Therefore, the signal-to-noise ratio is 1.1 × 1 / σ, and it can be seen that improvement is obtained by the correction of the present invention.
上記の具体例により、光ファイバ１箇所からの反射信号の信号対ノイズ比の改善が確認できた。光ファイバ全体においては、各箇所からの反射信号の重ね合わせであるため、この算出手法を適用することができる。 According to the above specific example, it was confirmed that the signal-to-noise ratio of the reflected signal from one optical fiber was improved. This calculation method can be applied to the entire optical fiber because it is a superposition of the reflected signals from each location.
しかし、実際は相関処理時に発生するサイドローブと呼ばれる不要信号による干渉があるため、理想的な改善は得られないことがある。このため、一般的には、光ファイバ分布型温度測定装置に用いられるレーザ光のパルス列符号は、理想的にはサイドローブのないゴーレイ符号等が用いられる。 However, in reality, there is an interference due to an unnecessary signal called a side lobe that is generated at the time of correlation processing, so that an ideal improvement may not be obtained. For this reason, generally, the pulse train code of the laser light used in the optical fiber distributed temperature measuring device is ideally a Golay code or the like having no side lobe.
実際には、波形の振幅の変化や本発明のように相関係数に補正をかけること等でサイドローブが発生するが、ゴーレイ符号を使用することによりこのサイドローブを低減できると考えられる。 Actually, side lobes are generated by changing the amplitude of the waveform or correcting the correlation coefficient as in the present invention, but it is considered that the side lobes can be reduced by using the Golay code.
図２は、本発明の効果を説明する波形図である。図２（Ａ）の（イ），（ロ）は、理想的な相関処理前及び処理後の波形、図２（Ｂ）の（イ），（ロ）は、補正のない相関処理前及び処理後の波形、図２（Ｃ）の（イ），（ロ）は、補正のある相関処理前後の波形のシミュレーション例を示す。この例においては補正のあるないによらず、サイドローブは同等レベルと考えられる。 FIG. 2 is a waveform diagram for explaining the effect of the present invention. (A) and (B) in FIG. 2A are waveforms before and after ideal correlation processing, and (A) and (B) in FIG. 2B are before and after correlation processing without correction. The later waveforms, (A) and (B) in FIG. 2C, show simulation examples of waveforms before and after correlation processing with correction. In this example, the side lobes are considered to be at the same level regardless of whether there is no correction.
図２（Ｄ）の（イ），（ロ）は、ゴーレイ符号等の使用による相関処理前及び処理後の波形のシミュレーション例を示し、サイドローブ処理が理想的に実行された場合の波形を示している。 FIGS. 2D and 2B show simulation examples of waveforms before and after correlation processing by using Golay codes, etc., and show waveforms when sidelobe processing is ideally executed. ing.
図３は、さらに同じ条件でノイズ印加時の本発明の効果を説明する波形図である。図３（Ａ）の（イ），（ロ）は、ノイズを印加した場合の理想的な相関処理前及び処理後の波形、図３（Ｂ）の（イ），（ロ）は、ノイズを印加して補正のない場合の相関処理前及び処理後の波形、図３（Ｃ）の（イ），（ロ）は、ノイズを印加して補正のある場合の相関処理前及び処理後の波形のシミュレーション例を示す。 FIG. 3 is a waveform diagram for explaining the effect of the present invention when noise is applied under the same conditions. (A) and (B) in FIG. 3A are waveforms before and after ideal correlation processing when noise is applied, and (A) and (B) in FIG. Waveforms before and after correlation processing when applied and without correction, (A) and (B) in FIG. 3C are waveforms before and after correlation processing when correction is applied by applying noise. An example of simulation is shown.
図の波形においてピーク値を信号レベル、ピーク値を除く平方和をノイズレベルとして数値で比較すると以下のようになり、本発明による補正の効果を確認することができる。
In the waveform of the figure, when the numerical value is compared with the peak value as the signal level and the sum of squares excluding the peak value as the noise level as follows, the effect of the correction according to the present invention can be confirmed.
以上説明した実施例では、相関係数の補正値は、信号対ノイズ比を改善するため、パワー変動に起因する光ファイバ増幅器４の出力特性そのものを用いたが、光ファイバ増幅器から出力される光パルス列のパワー変動パターンを予め記憶保持する記憶手段からの補正情報に基づいて、前記レベル補正部のレベル補正と前記相関処理部の係数補正を行ってもよい。 In the embodiment described above, the correction value of the correlation coefficient uses the output characteristics of the optical fiber amplifier 4 due to power fluctuations in order to improve the signal-to-noise ratio, but the light output from the optical fiber amplifier is used. The level correction by the level correction unit and the coefficient correction by the correlation processing unit may be performed based on correction information from a storage unit that stores and holds the power fluctuation pattern of the pulse train in advance.
本発明を適用した相関処理部１００Ａ、１００Ｂにおける相関係数の補正手法は、レイリー散乱光、フレネル反射光、ブリルアン散乱光等を用いた各種光ファイバ試験装置、測定装置に適用することが可能である。 The correlation coefficient correction method in the correlation processing units 100A and 100B to which the present invention is applied can be applied to various optical fiber test apparatuses and measurement apparatuses using Rayleigh scattered light, Fresnel reflected light, Brillouin scattered light, and the like. is there.
１ 光ファイバ
２ レーザ光源
３ 符号生成回路
４ 光ファイバ増幅器
５ 光カプラ
６ 波長分波器
７ フォトダイオード
８ 受光回路
９ 増幅回路
１０ Ａ／Ｄ変換回路
１１ タイミング発生回路
１２ 平均化回路
１３ レベル補正部
１５ 温度演算部
１６ 温度表示部
１００Ａ、１００Ｂ 相関処理部
Ｒ１，Ｒ２，Ｒ３，…ＲＮ シフトレジスタ
Ｍ１，Ｍ２，Ｍ３，…ＭＮ 乗算手段
Ｓ 加算手段
a1,a2,a3,…aN 光ファイバ増幅器の出力特性係数
k1,k2,k3,…kN 相関係数
１０１，１０２，１０３，…１０Ｎ 係数補正手段
DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Laser light source 3 Code generation circuit 4 Optical fiber amplifier 5 Optical coupler 6 Wavelength demultiplexer 7 Photodiode 8 Light receiving circuit 9 Amplifying circuit 10 A / D conversion circuit 11 Timing generation circuit 12 Averaging circuit 13 Level correction part 15 Temperature calculation unit 16 Temperature display unit 100A, 100B Correlation processing unit R1, R2, R3,... RN Shift register M1, M2, M3,.
a1, a2, a3, ... aN Optical fiber amplifier output characteristic coefficient
k1, k2, k3,... kN correlation coefficients 101, 102, 103,.
Claims (4)
前記夫々の相関処理部で前記光パルス列に対応して設定される係数を、前記光ファイバ増幅器から出力される光パルス列のパワー変動に応じて補正する係数補正手段を備えることを特徴とする光ファイバ分布型温度測定装置。 A level of each received light signal that is demultiplexed into Stokes light and anti-Stokes light from back Raman scattered light obtained from an optical fiber that is incident on an optical pulse train that is output from an optical fiber amplifier, and converted into an electrical signal. Level correction unit that corrects according to the power fluctuation of the optical pulse train output from the amplifier, correlation processing unit that performs correlation processing on each level-corrected received light signal, and demodulation, and outputs of each correlation processing unit A temperature calculation unit that calculates a temperature signal based on the optical fiber distributed temperature measurement device,
An optical fiber comprising coefficient correction means for correcting a coefficient set by each correlation processing unit corresponding to the optical pulse train in accordance with a power fluctuation of the optical pulse train output from the optical fiber amplifier. Distributed temperature measuring device.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140254629A1 (en) * | 2013-03-06 | 2014-09-11 | Yokogawa Electric Corporation | Optical fiber temperature distribution measurement device and method of measuring optical fiber temperature distribution |
| US10775245B2 (en) | 2015-05-13 | 2020-09-15 | Fujitsu Limited | Temperature measurement device, temperature measurement method, and computer-readable non-transitory medium |
| CN112945417A (en) * | 2021-02-26 | 2021-06-11 | 王世有 | Dual-wavelength fluorescent optical fiber temperature measurement system based on europium-doped yttrium oxide fluorescent powder |
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2010
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140254629A1 (en) * | 2013-03-06 | 2014-09-11 | Yokogawa Electric Corporation | Optical fiber temperature distribution measurement device and method of measuring optical fiber temperature distribution |
| JP2014173877A (en) * | 2013-03-06 | 2014-09-22 | Yokogawa Electric Corp | Optical fiber temperature distribution measuring device |
| US9689751B2 (en) * | 2013-03-06 | 2017-06-27 | Yokogawa Electric Corporation | Optical fiber temperature distribution measurement device and method of measuring optical fiber temperature distribution |
| US10775245B2 (en) | 2015-05-13 | 2020-09-15 | Fujitsu Limited | Temperature measurement device, temperature measurement method, and computer-readable non-transitory medium |
| CN112945417A (en) * | 2021-02-26 | 2021-06-11 | 王世有 | Dual-wavelength fluorescent optical fiber temperature measurement system based on europium-doped yttrium oxide fluorescent powder |
| CN112945417B (en) * | 2021-02-26 | 2022-06-28 | 王世有 | Dual-wavelength fluorescent optical fiber temperature measurement system based on europium-doped yttrium oxide fluorescent powder |
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