JPH0690112B2 - Backscattered light measurement device - Google Patents
Backscattered light measurement deviceInfo
- Publication number
- JPH0690112B2 JPH0690112B2 JP29413588A JP29413588A JPH0690112B2 JP H0690112 B2 JPH0690112 B2 JP H0690112B2 JP 29413588 A JP29413588 A JP 29413588A JP 29413588 A JP29413588 A JP 29413588A JP H0690112 B2 JPH0690112 B2 JP H0690112B2
- Authority
- JP
- Japan
- Prior art keywords
- light
- backscattered light
- optical waveguide
- backscattered
- measured
- 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 - Lifetime
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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
- G01M11/3172—Reflectometers detecting the back-scattered light in the frequency-domain, e.g. OFDR, FMCW, heterodyne detection
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- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Testing Of Optical Devices Or Fibers (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は光導波路の不連続点の探索に利用する。特に、
光導波路内で生じる後方散乱光を測定する装置に関す
る。DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is used for searching for discontinuities in an optical waveguide. In particular,
The present invention relates to a device for measuring backscattered light generated in an optical waveguide.
本発明は、被測定光導波路内で生じた後方散乱光を測定
する装置において、後方散乱光または参照光を周波数ｆ
で位相変調し、この後方散乱光と参照光を合波したのち
周波数ｆ成分およびその二次高調波2f成分をそれぞれ測
定することにより、後方散乱光と参照光との位相差の変
動による影響を除去し、高い信号対雑音比で後方散乱光
を測定できるようにするものである。The present invention is a device for measuring backscattered light generated in an optical waveguide to be measured, wherein the backscattered light or the reference light has a frequency f.
Phase modulation is performed with, and after the backscattered light and the reference light are combined, the frequency f component and its second harmonic 2f component are measured, respectively, to determine the influence of the fluctuation of the phase difference between the backscattered light and the reference light. It enables to measure backscattered light with high signal-to-noise ratio.
〔従来の技術〕 第４図は従来例後方散乱光測定装置のブロック構成図で
ある。[Prior Art] FIG. 4 is a block diagram of a conventional backscattered light measuring apparatus.
光源１の出射光は、レンズ２を介してビームスプリッタ
３に入射する。ビームスプリッタ３は、この入射光を二
つに分割し、その一方をレンズ４を介して被測定光導波
路５に入射する。また、分割された他方の光は参照光と
して用いられ、全反射鏡６により反射され、再びビーム
スプリッタ３に入射する。被測定光導波路５内で発生し
た後方散乱光は、レンズ４を介してビームスプリッタ３
に入射し、ここで参照光に合波される。この合波光は光
検出器８に入射する。光検出器８の出力は、選択レベル
計９およびアナログ・ディジタル変換器10を経由して、
信号処理部11に供給される。The light emitted from the light source 1 enters the beam splitter 3 via the lens 2. The beam splitter 3 splits the incident light into two, and one of them is incident on the measured optical waveguide 5 via the lens 4. The other split light is used as reference light, is reflected by the total reflection mirror 6, and is incident on the beam splitter 3 again. The backscattered light generated in the measured optical waveguide 5 passes through the lens 4 and the beam splitter 3
Is incident on and is multiplexed with the reference light. This combined light enters the photodetector 8. The output of the photodetector 8 passes through the selective level meter 9 and the analog-digital converter 10,
It is supplied to the signal processing unit 11.
この装置において、全反射鏡６を移動台７により移動さ
せると、後方散乱光に対する参照光の遅延時間が変化す
る。これを利用して、被測定光導波路５内の各点を全反
射鏡６の位置に対応させ、後方散乱光の強度分布を求め
ることができる。In this device, when the total reflection mirror 6 is moved by the moving table 7, the delay time of the reference light with respect to the backscattered light changes. By utilizing this, each point in the measured optical waveguide 5 can be made to correspond to the position of the total reflection mirror 6, and the intensity distribution of the backscattered light can be obtained.
全反射鏡６の移動による遅延時間の変化量をτ、この変
化量τに対応する被測定光導波路５内の位置をｚとする
と、光検出器８の出力は、 Ｉ＝ｃ（１＋Γ（ｚ）cos（２πνｔ） ………（１） となる。ここで、ｃは定数、Γ（ｚ）は被測定光導波路
５内の点ｚで生じる後方散乱光の電場振幅に比例する無
次元の値（Γ(z)2が相対光強度を表す）、νは全反射鏡
６の移動にともなって生じるビート周波数である。Assuming that the change amount of the delay time due to the movement of the total reflection mirror 6 is τ and the position in the measured optical waveguide 5 corresponding to this change amount τ is z, the output of the photodetector 8 is I = c (1 + Γ (z ) Cos (2πνt) (1) where c is a constant and Γ (z) is a dimensionless value proportional to the electric field amplitude of the backscattered light generated at the point z in the measured optical waveguide 5. (Γ (z) 2 represents the relative light intensity), and ν is a beat frequency generated with the movement of the total reflection mirror 6.
そこで、選択レベル計９の中心周波数をνに設定するこ
とにより、交流成分ｃΓ（ｚ）cos（２πνｔ）の振幅
ｃΓ（ｚ）が測定される。この測定をτを変化させなが
ら繰り返すことにより、被測定光導波路５の後方散乱光
の強度分布が得られる。Therefore, by setting the center frequency of the selection level meter 9 to ν, the amplitude cΓ (z) of the AC component cΓ (z) cos (2πνt) is measured. By repeating this measurement while changing τ, the intensity distribution of the back scattered light of the measured optical waveguide 5 can be obtained.
第５図に従来例装置による測定結果の一例を示す。この
例は、選択レベル計の帯域幅を30Hzに設定したときの測
定結果である。FIG. 5 shows an example of the measurement result by the conventional device. This example is the measurement result when the bandwidth of the selected level meter is set to 30 Hz.
しかし、全反射鏡の移動速度を厳密に一定に保つことは
困難である。この移動速度に変動があると、それにとも
なってビート周波数νが変動する。この変動は、従来装
置では10Hz程度となる。これに対して、Γ（ｚ）は非常
に微弱であるため、交流成分ｃΓ（ｚ）×cos（２πν
ｔ）を高い信号対雑音比で測定するためには、選択レベ
ル計の帯域幅をできるだけ狭くする必要がある。しか
し、前述した理由から、帯域幅を10Hz以下に設定するこ
とはできず、信号対雑音比を改善することが困難である
欠点があった。However, it is difficult to keep the moving speed of the total reflection mirror strictly constant. When the moving speed changes, the beat frequency ν changes accordingly. This fluctuation is about 10 Hz in the conventional device. On the other hand, since Γ (z) is very weak, the AC component cΓ (z) × cos (2πν
In order to measure t) with a high signal to noise ratio, it is necessary to make the bandwidth of the selective level meter as narrow as possible. However, for the reasons described above, the bandwidth cannot be set to 10 Hz or less, and there is a drawback that it is difficult to improve the signal-to-noise ratio.
本発明は、以上の問題点を解決し、測定帯域幅が狭く、
光導波路内で生じる後方散乱光を高い信号対雑音比で測
定することのできる後方散乱光測定装置を提供すること
を目的とする。The present invention solves the above problems and has a narrow measurement bandwidth,
An object of the present invention is to provide a backscattered light measuring device capable of measuring backscattered light generated in an optical waveguide with a high signal-to-noise ratio.
〔問題点を解決するための手段〕 本発明の後方散乱光測定装置は、後方散乱光または参照
光を周波数ｆで位相変調する手段と、後方散乱光と参照
光との合波光に含まれる周波数ｆ成分およびその二次高
調波2f成分をそれぞれ測定する手段と、この手段の出力
に一定の定数を乗算してその二乗和を求める演算手段と
を備えたことを特徴とする。[Means for Solving the Problems] The backscattered light measuring apparatus of the present invention includes means for phase-modulating the backscattered light or the reference light at the frequency f, and the frequency included in the combined light of the backscattered light and the reference light. It is characterized by comprising means for measuring the f component and its second harmonic 2f component respectively, and arithmetic means for multiplying the output of this means by a constant and obtaining the sum of squares thereof.
本発明の後方散乱光測定装置はさらに、後方散乱光と参
照光との光路長差の変動を測定する手段と、この光路長
差が一定となるように少なくともひとつの光路長を制御
する帰還手段とを含むことが望ましい。The backscattered light measuring device of the present invention further comprises means for measuring a variation in the optical path length difference between the backscattered light and the reference light, and a feedback means for controlling at least one optical path length so that the optical path length difference is constant. It is desirable to include and.
光路長差の変動を測定する手段は、測定用の光源からの
出射光の中心周波数と発光周波数の異なる参照光源と、
この参照光源の出射光を測定用の光源からの出射光に合
波する手段と、後方散乱光と参照光との合波光から参照
光源による成分を分離する手段と、分離された成分の強
度により光路長差を求める手段とを含むことができる。Means for measuring the variation of the optical path length difference, a reference light source having a different emission frequency and the center frequency of the emitted light from the light source for measurement,
The means for combining the emitted light of the reference light source with the emitted light from the light source for measurement, the means for separating the component by the reference light source from the combined light of the backscattered light and the reference light, and the intensity of the separated component Means for determining the optical path length difference.
参照光または後方散乱光の一方に周波数ｆの位相変調を
加えて、参照光と後方散乱光の干渉強度を周波数ｆおよ
びその高調波2f、3f…で変化する交流成分を生じさせ
る。この成分中の変調周波数ｆ成分および二次高調波2f
成分を狭帯域で検出すると、これらの検出信号には、後
方散乱光と参照光との位相差による変動が90°異なって
現れる。そこで、これらの信号に一定の定数を乗算して
二乗和を求めることにより、ビート周波数νの位相変動
の項を除去できる。したがって、光路長の変動に影響さ
れることなく、高い信号対雑音比で後方散乱光の強度を
求めることができる。Phase modulation of the frequency f is applied to one of the reference light and the backscattered light to generate an AC component that changes the interference intensity of the reference light and the backscattered light at the frequency f and its harmonics 2f, 3f. Modulation frequency f component and second harmonic 2f in this component
When the components are detected in a narrow band, fluctuations due to the phase difference between the backscattered light and the reference light appear at 90 ° in these detection signals. Therefore, the term of the phase fluctuation of the beat frequency ν can be removed by multiplying these signals by a constant and obtaining the sum of squares. Therefore, the intensity of the backscattered light can be obtained with a high signal-to-noise ratio without being affected by the fluctuation of the optical path length.
第１図は本発明第一実施例後方散乱光測定装置のブロッ
ク構成図である。FIG. 1 is a block diagram of the backscattered light measuring apparatus according to the first embodiment of the present invention.
この装置は、光源１を備え、この光源１の出射光を被測
定光導波路５に入射する入射手段としてレンズ２、４を
備え、出射光から参照光を分岐する光分岐手段およびこ
の参照光を被測定光導波路５の入射端に現れる後方散乱
光に合波する光合波手段としてビームスプリッタ３およ
び全反射鏡６を備え、この光合波手段の出力光を検出し
て被測定光導波路５からの後方散乱光強度を求める信号
処理手段として光検出器８、ロックインアンプ14、15、
アナログ・ディジタル変換器16、17および信号処理部11
を備える。This device comprises a light source 1, and lenses 2 and 4 as incident means for making the emitted light of the light source 1 incident on the optical waveguide 5 to be measured, and an optical branching means for branching the reference light from the emitted light and this reference light A beam splitter 3 and a total reflection mirror 6 are provided as optical combining means for combining the backscattered light appearing at the incident end of the measured optical waveguide 5, and the output light of this optical combining means is detected to output from the measured optical waveguide 5. As a signal processing means for obtaining the backscattered light intensity, a photodetector 8, lock-in amplifiers 14, 15,
Analog-digital converters 16 and 17 and signal processing unit 11
Equipped with.
ここで本実施例の特徴とするところは、参照光を周波数
ｆで位相変調する手段として電歪振動子12および交流発
振器13を備え、ビームスプリッタ３の出力光に含まれる
周波数ｆ成分およびその二次高調波2f成分をそれぞれ測
定する手段としてロックインアンプ14、15を備え、信号
処理部11が、ロックインアンプ14、15の出力に一定の定
数を乗算してその二乗和を求める演算手段を含むことに
ある。The feature of the present embodiment is that an electrostrictive oscillator 12 and an AC oscillator 13 are provided as means for phase-modulating the reference light at a frequency f, and the frequency f component included in the output light of the beam splitter 3 and its two components are included. The lock-in amplifiers 14 and 15 are provided as means for measuring the second harmonic 2f components, respectively, and the signal processing unit 11 calculates the sum of squares by multiplying the outputs of the lock-in amplifiers 14 and 15 by a constant. To include.
光源１の出力光はレンズ２によりコリメートされて平行
ビームとなり、ビームスプリッタ３により二つに分割さ
れる。分割された光の一方は、レンズ４を介して被測定
光導波路５に入射する。分割された光の他方は、全反射
鏡６で全反射し、再びビームスプリッタ３に入射し、被
測定光導波路５で生じた後方散乱光と合波される。この
合波光は光検出器８に入射する。The output light of the light source 1 is collimated by the lens 2 into a parallel beam, which is split into two by the beam splitter 3. One of the divided lights enters the optical waveguide 5 to be measured via the lens 4. The other of the split lights is totally reflected by the total reflection mirror 6, again enters the beam splitter 3, and is combined with the backscattered light generated in the measured optical waveguide 5. This combined light enters the photodetector 8.
全反射鏡６は電歪振動子12に固定されている。電歪振動
子12は、交流発振器13からの正弦波により駆動され、全
反射鏡６を入射ビームの方向に微小振動させる。これに
より、全反射鏡６の反射光、すなわち参照光が位相変調
される。The total reflection mirror 6 is fixed to the electrostrictive oscillator 12. The electrostrictive oscillator 12 is driven by the sine wave from the AC oscillator 13, and causes the total reflection mirror 6 to slightly vibrate in the direction of the incident beam. Thereby, the reflected light of the total reflection mirror 6, that is, the reference light, is phase-modulated.
このとき、後方散乱光と参照光との干渉強度、すなわち
光検出器８の出力は、 Ｉ＝ｃ｛１＋Γ（ｚ）cos〔φcos2πft＋Φ（ｚ）〕｝
………（２） となる。ここで、ｃ、φは定数、Γ（ｚ）は被測定光導
波路５内の点ｚで生じる後方散乱光の電場振幅に比例す
る無次元の値である。また、Φ（ｚ）は、参照光と後方
散乱光との位相差であり、被測定光導波路５内の点ｚと
参照光との光路長差をｌ（ｚ）とすると、 で与えられる。（２）式を展開すると、 となる。そこで、ロックインアンプ14、15によりそれぞ
れ周波数ｆ成分と、周波数2f成分とを検出する。これに
より、 If（ｚ）＝−２Γ（ｚ）J1（φ）sinΦ（Ｚ） I2f（ｚ）＝−２Γ（ｚ）J2（φ）cosΦ（Ｚ） が得られる。これらの検出出力は、アナログ・ディジタ
ル変換器16、17を介して信号処理部11に供給される。信
号処理部は、これらの値から、 を演算により求める。これにより４Γ(z)2が得られ、位
相差（ｚ）に依存せずに後方散乱光の強度を求めるこ
とができる。At this time, the interference intensity between the backscattered light and the reference light, that is, the output of the photodetector 8 is I = c {1 + Γ (z) cos [φcos2πft + Φ (z)]}
……… (2) Here, c and φ are constants, and Γ (z) is a dimensionless value proportional to the electric field amplitude of the backscattered light generated at the point z in the measured optical waveguide 5. Further, Φ (z) is the phase difference between the reference light and the backscattered light, and if the optical path length difference between the point z in the measured optical waveguide 5 and the reference light is l (z), Given in. Expanding equation (2), Becomes Therefore, the lock-in amplifiers 14 and 15 detect the frequency f component and the frequency 2f component, respectively. As a result, I f (z) = − 2Γ (z) J 1 (φ) sinΦ (Z) I 2f (z) = − 2Γ (z) J 2 (φ) cosΦ (Z) is obtained. These detection outputs are supplied to the signal processing unit 11 via the analog / digital converters 16 and 17. The signal processing unit uses these values to Is calculated. As a result, 4Γ (z) 2 is obtained, and the intensity of the backscattered light can be obtained without depending on the phase difference (z).
この装置では、被測定光導波路５内の測定点ｚを変える
ために全反射鏡６を移動させる必要があるが、各点を測
定するときには全反射鏡６を停止させる。このため、変
調周波数ｆの安定度程度、すなわち高々1Hz程度にロッ
クインアンプ14、15の測定帯域幅を狭めることができ
る。In this device, it is necessary to move the total reflection mirror 6 in order to change the measurement point z in the measured optical waveguide 5, but the total reflection mirror 6 is stopped when measuring each point. Therefore, the measurement bandwidth of the lock-in amplifiers 14 and 15 can be narrowed to the degree of stability of the modulation frequency f, that is, at most about 1 Hz.
ここで、実際の測定時には、ビームスプリッタ３、レン
ズ４、被測定光導波路５および全反射鏡６により構成さ
れるマイケルソン干渉計の二つのアームの光路長差が、
温度変動や振動その他の外乱によりランダムに変動する
ことが問題となる。この変動の周期が1Hz程度あるた
め、ロックインアンプの帯域幅を1Hz以下にすることは
困難である。そこで本実施例では、光源１の出射光の中
心周波数と発光周波数の異なる参照光源としてHe−Neレ
ーザ18を用い、このHe−Neレーザ18からの干渉性の高い
光をダイクロイックミラー19を介してマイケルソン干渉
計内に導入し、光源１の出射光と同一の経路を伝搬させ
る。そして、マイケルソン干渉計の出射光からダイクロ
イックミラー20によりHe−Neレーザ18に起因する光を分
離抽出して光検出器21に入射する。この光検出器21の出
力について、ロックインアンプ22により干渉強度成分を
検出する。このとき、ロックインアンプ22の出力はJ
1（φ）sinΦ（Ｚ）比例する。ただし、Φ（ｚ）はHe−
Neレーザ18の出射光の位相差である。そこで、帰還回路
23により、ロックインアンプ22の検出信号J1（φ）sin
Φ（Ｚ）が常に一定となるように全反射鏡６の位置を補
正する。すなわち、マイケルソン干渉計の光路長差を一
定に保持する。これにより、ロックインアンプ14、15の
測定帯域幅を0.1Hz以下に設定することができる。Here, at the time of actual measurement, the optical path length difference between the two arms of the Michelson interferometer composed of the beam splitter 3, the lens 4, the measured optical waveguide 5, and the total reflection mirror 6,
Random fluctuations due to temperature fluctuations, vibrations, and other disturbances pose a problem. Since the cycle of this fluctuation is about 1 Hz, it is difficult to set the bandwidth of the lock-in amplifier to 1 Hz or less. Therefore, in the present embodiment, a He-Ne laser 18 is used as a reference light source having a different emission frequency from the center frequency of the light emitted from the light source 1, and light with high coherence from this He-Ne laser 18 is passed through a dichroic mirror 19. It is introduced into the Michelson interferometer and propagates along the same path as the light emitted from the light source 1. Then, the light originating from the He—Ne laser 18 is separated and extracted by the dichroic mirror 20 from the light emitted from the Michelson interferometer and is incident on the photodetector 21. The interference intensity component of the output of the photodetector 21 is detected by the lock-in amplifier 22. At this time, the output of the lock-in amplifier 22 is J
1 (φ) sinΦ (Z) Proportional. However, Φ (z) is He−
It is the phase difference of the emitted light of the Ne laser 18. Therefore, the feedback circuit
23, the detection signal J 1 (φ) sin of the lock-in amplifier 22
The position of the total reflection mirror 6 is corrected so that Φ (Z) is always constant. That is, the optical path length difference of the Michelson interferometer is kept constant. As a result, the measurement bandwidth of the lock-in amplifiers 14 and 15 can be set to 0.1 Hz or less.
第２図は前述の実施例装置による測定結果の一例を示
す。FIG. 2 shows an example of the measurement result obtained by the apparatus of the above-mentioned embodiment.
この測定結果は、第５図に示した従来例による測定と同
じ被測定光導波路について得られたものである。被測定
光導波路の長さは10cm、横軸の零点は導波路入射端を示
し、10cmの点が被測定光導波路の出射端に相当する。入
射端と出射端との間の信号が被測定光導波路内の各点で
生じた後方散乱光の強度を示す。この測定では、ロック
インアンプ14、15の帯域幅は0.1Hzに設定した。This measurement result is obtained for the same optical waveguide as the measurement according to the conventional example shown in FIG. The length of the measured optical waveguide is 10 cm, the zero point on the horizontal axis indicates the waveguide entrance end, and the 10 cm point corresponds to the exit end of the measured optical waveguide. The signal between the entrance end and the exit end indicates the intensity of the backscattered light generated at each point in the measured optical waveguide. In this measurement, the bandwidth of lock-in amplifiers 14 and 15 was set to 0.1 Hz.
このように、本実施例は、従来例に比較して信号対雑音
比を２桁以上向上させることができた。As described above, the present embodiment was able to improve the signal-to-noise ratio by two digits or more as compared with the conventional example.
第３図は本発明第二実施例後方散乱光測定装置の構成を
示す。FIG. 3 shows the configuration of the backscattered light measuring apparatus according to the second embodiment of the present invention.
この実施例は、第一実施例のバルク形マイケルソン干渉
計をファイバ形マイケルソン干渉計に置き換えたもので
ある。すなわち、ダイクロイックミラー19およびビーム
スプリッタ３がそれぞれファイバ形光結合器24、25に置
き換えられる。In this embodiment, the bulk Michelson interferometer of the first embodiment is replaced with a fiber Michelson interferometer. That is, the dichroic mirror 19 and the beam splitter 3 are replaced with fiber type optical couplers 24 and 25, respectively.
また、参照光に位相変調を加えるため、ファイバ形光結
合器25の一方の出射端にファイバ形位相変調器26を設
け、交流発振器13からの交流信号により、光路長を正弦
関数で変化させている。Further, in order to apply phase modulation to the reference light, a fiber type phase modulator 26 is provided at one emission end of the fiber type optical coupler 25, and the optical path length is changed by a sine function by an AC signal from the AC oscillator 13. There is.
さらに、ファイバ形マイケルソン干渉計における外乱に
よる位相変化を抑えるため、ファイバ形光結合器25の他
方の出射端にもファイバ形位相変調器27が設けられてい
る。このファイバ形位相変調器は、帰還回路23により制
御される。すなわち、ファイバの伸縮によりその光路長
を安定化し、強度変化が少なく雑音の少ない干渉計が得
られる。Further, in order to suppress the phase change due to the disturbance in the fiber type Michelson interferometer, the fiber type phase modulator 27 is also provided at the other emitting end of the fiber type optical coupler 25. This fiber type phase modulator is controlled by the feedback circuit 23. That is, the optical path length is stabilized by expansion and contraction of the fiber, and an interferometer with less intensity change and less noise can be obtained.
ファイバ形位相変調器26、27は光ファイバを円筒形の電
歪振動子に巻きつけた構造をもち、この電歪振動子に印
加する電圧を調整することにより光路長を変化させ、内
部を伝搬する光を位相変調することができる。The fiber type phase modulators 26 and 27 have a structure in which an optical fiber is wound around a cylindrical electrostrictive oscillator, and the optical path length is changed by adjusting the voltage applied to this electrostrictive oscillator and propagated inside. The light can be phase-modulated.
以上説明したように、本発明の後方散乱光測定装置は、
光導波路内で生じた後方散乱光を高い信号対雑音被で測
定できる。したがって、光導波路の損失や障害点を高精
度に測定できる効果がある。As described above, the backscattered light measuring device of the present invention,
The backscattered light generated in the optical waveguide can be measured with high signal-to-noise coverage. Therefore, there is an effect that the loss and the failure point of the optical waveguide can be measured with high accuracy.
第１図は本発明第一実施例後方散乱光測定装置のブロッ
ク構成図。 第２図は測定結果の一例を示す図。 第３図は本発明第二実施例後方散乱光測定装置のブロッ
ク構成図。 第４図は従来例後方散乱光測定装置のブロック構成図。 第５図は従来例装置による測定結果の一例を示す図。 １…光源、２、４…レンズ、３…ビームスプリッタ、５
…被測定光導波路、６…全反射鏡、７…移動台、８、21
…光検出器、９…選択レベル計、10、16、17…アナログ
・ディジタル変換器、11…信号処理部、12…電歪振動
子、13…交流発振器、14、15、22…ロックインアンプ、
18…He−Neレーザ、19、20…ダイクロイックミラー、23
…帰還回路、24、25…ファイバ形光結合器、26、27…フ
ァイバ形位相変調器。FIG. 1 is a block configuration diagram of a backscattered light measuring device according to a first embodiment of the present invention. FIG. 2 is a diagram showing an example of measurement results. FIG. 3 is a block configuration diagram of a backscattered light measuring device according to a second embodiment of the present invention. FIG. 4 is a block diagram of a conventional backscattered light measuring device. FIG. 5 is a diagram showing an example of a measurement result by a conventional device. 1 ... Light source, 2, 4 ... Lens, 3 ... Beam splitter, 5
... Optical waveguide to be measured, 6 ... Total reflection mirror, 7 ... Moving base, 8, 21
... Photodetector, 9 ... Selection level meter, 10, 16, 17 ... Analog-digital converter, 11 ... Signal processing unit, 12 ... Electrostrictive oscillator, 13 ... AC oscillator, 14, 15, 22 ... Lock-in amplifier ,
18 ... He-Ne laser, 19, 20 ... Dichroic mirror, 23
… Feedback circuit, 24, 25… Fiber type optical coupler, 26, 27… Fiber type phase modulator.
Claims (1)
と、 前記出射光から参照光を分岐する光分岐手段と、 この参照光を前記被測定光導波路の入射端に現れる後方
散乱光に合波する光合波手段と、 この光合波手段の出力光を検出して前記被測定光導波路
からの後方散乱光強度を求める信号処理手段と を備えた後方散乱光測定装置において、 前記後方散乱光または前記参照光を周波数ｆで位相変調
する手段を備え、 前記信号処理手段は、前記合波手段の出力光に含まれる
周波数ｆ成分およびその二次高調波2f成分をそれぞれ測
定する手段と、この手段の出力に一定の定数を乗算して
その二乗和を求める演算手段とを含む ことを特徴とする後方散乱光測定装置。1. A light source, an incident means for making light emitted from the light source incident on an optical waveguide to be measured, an optical branching means for branching reference light from the emitted light, and the reference light being incident on the optical waveguide to be measured. Backscattered light measurement provided with a light combining means for combining the backscattered light appearing at the end, and a signal processing means for detecting the output light of this light combining means to obtain the backscattered light intensity from the optical waveguide to be measured. In the apparatus, means for phase-modulating the backscattered light or the reference light with a frequency f is provided, and the signal processing means includes a frequency f component and a second harmonic 2f component thereof included in the output light of the combining means. An apparatus for measuring backscattered light, comprising: a means for measuring each and an operation means for multiplying the output of this means by a constant to obtain the sum of squares thereof.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29413588A JPH0690112B2 (en) | 1988-11-21 | 1988-11-21 | Backscattered light measurement device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29413588A JPH0690112B2 (en) | 1988-11-21 | 1988-11-21 | Backscattered light measurement device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02140639A JPH02140639A (en) | 1990-05-30 |
| JPH0690112B2 true JPH0690112B2 (en) | 1994-11-14 |
Family
ID=17803758
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP29413588A Expired - Lifetime JPH0690112B2 (en) | 1988-11-21 | 1988-11-21 | Backscattered light measurement device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0690112B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5156291B2 (en) * | 2007-07-31 | 2013-03-06 | 浜松ホトニクス株式会社 | Apparatus for measuring optical properties of samples flowing in a flow cell |
| JP6259753B2 (en) * | 2014-12-09 | 2018-01-10 | 日本電信電話株式会社 | Light reflection measuring device and light reflection measuring method |
| WO2018123169A1 (en) | 2016-12-26 | 2018-07-05 | 三菱電機株式会社 | Device and method for measuring biological material |
| JP7424360B2 (en) * | 2021-11-29 | 2024-01-30 | 横河電機株式会社 | Optical fiber characteristic measuring device and optical fiber characteristic measuring method |
-
1988
- 1988-11-21 JP JP29413588A patent/JPH0690112B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02140639A (en) | 1990-05-30 |
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