JP5118004B2 - Optical fiber sensor - Google Patents
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- 239000013307 optical fiber Substances 0.000 title claims description 12
- 230000003287 optical effect Effects 0.000 claims description 25
- 238000001514 detection method Methods 0.000 claims description 13
- 238000005259 measurement Methods 0.000 claims description 5
- 230000003111 delayed effect Effects 0.000 claims description 2
- 238000000034 method Methods 0.000 description 6
- 239000000835 fiber Substances 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
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Description
本発明は、光ファイバが外圧により、そこを通過する光信号の位相に変化を及ぼす特性を利用した光ファイバセンサに関する。 The present invention relates to an optical fiber sensor that utilizes a characteristic that changes the phase of an optical signal passing through an optical fiber due to an external pressure.
光ファイバセンサは、電磁的影響を受けないことから、従来の電気信号センサに比べて、センサ信号を安定に長距離伝送することができる。 Since the optical fiber sensor is not affected by electromagnetic waves, the sensor signal can be stably transmitted over a long distance as compared with the conventional electric signal sensor.
光の干渉を利用したセンサ方式としては、参照光と被参照光を反射、戻して干渉させるマイケルソン干渉方式と、参照光と被参照光を進めて干渉させるマッハ・ツェンダ干渉方式がある。 As sensor methods using light interference, there are a Michelson interference method in which reference light and reference light are reflected and reflected to interfere with each other, and a Mach-Zehnder interference method in which reference light and reference light are caused to interfere with each other.
参照光と外圧を受けた被参照光との位相差の変化は、干渉により、光強度の変化に変換されて、光ファイバ伝送路を経て、光強度変化として検出される。 A change in phase difference between the reference light and the reference light subjected to external pressure is converted into a change in light intensity due to interference, and is detected as a change in light intensity through the optical fiber transmission line.
干渉出力は光強度の変化として検出されるが、この中には干渉以外の光強度の変化分も含まれた状態で検出されるため、その分が検出誤差となる。 The interference output is detected as a change in the light intensity, but this is detected in a state in which the change in the light intensity other than the interference is included, and this amount becomes a detection error.
干渉以外の光強度の変動要因としては、光ファイバ伝送路の損失変動、参照光、被参照光との比率変動、分波器、合波器の損失変動などがあるが、従来は検出した干渉光より干渉以外の変動分を識別、分離することが困難であった。
センサの高感度化を図るには、検出誤差となる前記干渉以外の光強度の変動要因を除去する必要がある。Factors that cause fluctuations in light intensity other than interference include loss fluctuations in optical fiber transmission lines, ratio fluctuations with reference light and reference light, loss fluctuations in duplexers and multiplexers. It was difficult to identify and separate fluctuations other than interference from light.
In order to increase the sensitivity of the sensor, it is necessary to remove the light intensity fluctuation factor other than the interference, which becomes a detection error.
本発明の光センサ部では、時分割多重方式により、参照光、被参照光、および干渉光を時分割で同一の光ファイバによって送り、検出部で参照光、被参照光、干渉光レベルの３つの信号レベルを用いて変動要因を除去した出力を得る。 In the optical sensor unit of the present invention, the reference light, the reference light, and the interference light are sent by the same optical fiber in a time division manner by the time division multiplexing method, and the reference light, the reference light, and the interference light level 3 are transmitted by the detection unit. An output from which fluctuation factors are removed is obtained using two signal levels.
本発明の光センサ部では、計測用光パルスを分波器で２波に分波して、一方を参照光パルス、他方をセンサとして、外圧を受ける被参照光パルスとし、被参照光パルスは参照光パルスに対して一定の遅延を持たせて、一部が重なり合う時間関係に設定し、前記参照光パルスと一定の遅延を受けた被参照光パルスは合波器により合波されて、一つの光信号パルスとなる。 In the optical sensor unit of the present invention, the optical pulse for measurement is demultiplexed into two waves by a demultiplexer, and one is a reference optical pulse and the other is a sensor, which is a reference optical pulse that receives external pressure. The reference light pulse is set to have a time relationship in which a part of the reference light pulse overlaps, and the reference light pulse and the reference light pulse that has received the constant delay are combined by a multiplexer. It becomes one optical signal pulse.
前記光信号パルスは、参照光のみの参照光部、参照光と被参照光が重なった部分の干渉光部および被参照光のみの被参照光部により構成され、光ファイバにより検出部に送られる。 The optical signal pulse is composed of a reference light unit including only reference light, an interference light unit where the reference light overlaps with the reference light, and a reference light unit including only the reference light, and is transmitted to the detection unit via an optical fiber. .
本発明の検出部では、前記光信号パルスを電気信号パルスに変換し、参照光部の電気信号、干渉光部の電気信号および被参照光部の電気信号をそれぞれサンプル・ホールドする。 The detection unit of the present invention converts the optical signal pulse into an electrical signal pulse, and samples and holds the electrical signal of the reference light unit, the electrical signal of the interference light unit, and the electrical signal of the reference light unit.
本発明では、前記サンプル・ホールドされた各電気信号レベルは、センサ部における参照光、被参照光、干渉光レベルに対応しているものとして、各電気信号レベルを入力とした演算処理を行い、参照光と被参照光との位相差の関数を求めることで、変動要因を除去した出力を得る。 In the present invention, each of the sampled and held electric signal levels corresponds to the reference light, the reference light, and the interference light level in the sensor unit, and performs an arithmetic process using each electric signal level as an input. By obtaining a function of the phase difference between the reference light and the reference light, an output from which the variation factor is removed is obtained.
本発明では、干渉信号を得る時点における参照光レベル、被参照光レベルおよびその干渉光レベルに即した電気信号を検出部で得る。 In the present invention, the reference light level at the time of obtaining the interference signal, the reference light level, and the electrical signal corresponding to the interference light level are obtained by the detection unit.
この電気信号レベルは以下の関係にある。
従来は、このうち干渉光の電気信号レベル：ｋの値を干渉出力としていたが、本発明では、加えて参照光の電気信号レベル：ｊと被参照光の電気信号レベル：ｌを検出部で得ている。
参照光と被参照光の位相差：θを置くと、
ｊ＋ｌ＋２√（ｊ・ｌ）ｃｏｓθ＝ｋ
の関係式が成り立つ。
この関係式から、位相差の関数ｃｏｓθを求めると、ｃｏｓθ＝（ｋ−ｊ−ｌ）／２√（ｊ・ｌ）となる。
ｊ、ｌ、ｋはそれぞれ損失変動を含むが、同じ光ファイバをほとんど同時に通過しており、同じ比率で変動を受けていることに等しいため、（ｋ−ｊ−ｌ）／２√（ｊ・ｌ）の分母、分子に、変動分は同率に掛かることになり、この除算の値から損失変動の影響は除外される。
よってｃｏｓθには、損失変動による誤差分は含まれない値として求めることができる。
本発明では、センサ出力として、ｃｏｓθまたはθを出力することにより、損失変動分による誤差を含まない出力を得ることができる。
This electric signal level has the following relationship.
Conventionally, the value of the electrical signal level of the interference light: k is used as the interference output. In the present invention, the electrical signal level of the reference light: j and the electrical signal level of the reference light: l are additionally detected by the detection unit. It has gained.
Phase difference between reference light and referenced light: When θ is set ,
j + l + 2√ (j · l) cos θ = k
The following relational expression holds.
If the phase difference function cos θ is obtained from this relational expression , cos θ = (k−j −l ) / 2√ (j · l ).
Each of j, l, and k includes a loss variation, but is equivalent to passing through the same optical fiber almost at the same time and undergoing a variation at the same ratio, so (k−j −l ) / 2√ (j · The variation is applied to the denominator and numerator of l ) at the same rate, and the influence of loss variation is excluded from the value of this division.
Therefore, cos θ can be obtained as a value that does not include an error due to loss fluctuation.
In the present invention, by outputting cos θ or θ as the sensor output, it is possible to obtain an output that does not include an error due to the loss variation.
〔図１〕本発明のマッハ・ツェンダ干渉方式の光センサ部を示す。
計測用の光パルスａは分波器Ａ１でｂ，ｃの２つに分波されて、ｂは参照光、ｃは被参照光となりｃは遅延ファイバＤ１を経てセンサとなる外圧Ｃ１が加えられてｄとして、ｂとともに合波器Ｂ１に入り、合波出力ｅ１として検出部に送られる。FIG. 1 shows a Mach-Zehnder interference optical sensor unit of the present invention.
The measurement light pulse a is demultiplexed into b and c by a demultiplexer A1, b is a reference light, c is a reference light, and c is applied with an external pressure C1 serving as a sensor via a delay fiber D1. As d, it enters the multiplexer B1 together with b, and is sent to the detector as a combined output e1.
〔図２〕本発明のマイケルソン干渉方式の光センサ部を示す。
計測用の光パルスａは分波器Ａ２でｂ，ｃの２つに分波されて、ｂは参照光、ｃは被参照光となり、ｃは遅延ファイバＤ２を経てセンサとなる外圧Ｃ２が加えられた後、反射鏡Ｅ２で戻され、ｄとして同様に反射鏡Ｅ１で戻されたｂとともに合波器Ａ２に入り、合波出力ｅ１として検出部に送られる。FIG. 2 shows a Michelson interferometric optical sensor unit according to the present invention.
The measurement light pulse a is demultiplexed into b and c by a demultiplexer A2, b is a reference light, c is a reference light, and c is applied with an external pressure C2 serving as a sensor via a delay fiber D2. After that, it is returned by the reflecting mirror E2, and similarly enters d as well as b returned by the reflecting mirror E1, enters the multiplexer A2, and is sent to the detector as a combined output e1.
〔図３〕本発明の光センサ部（図１、図２）の動作タイムチャートを示す。
ａはセンサ部に入力する計測用光パルス
ｂは２分岐された一方の光パルスで、参照光となる
ｃは２分岐された他方の光パルスで、被参照光となる
ｄは遅延ファイバによりｃが遅らされて、外圧を受けた後の被参照光
ｅ１はｂ、ｄを入力とした合波出力
ｅ１出力の前方ｘはｂの重ならない部分：参照光部
ｅ１出力の中間ｙはｂとｄが重なる部分で干渉した部分：干渉光部
ｅ１出力の後方ｚはｄの重ならない部分：被参照光部FIG. 3 shows an operation time chart of the optical sensor unit (FIGS. 1 and 2) of the present invention.
a is a measurement optical pulse to be input to the sensor unit, b is one of the two branched optical pulses, and becomes reference light, c is the other branched two optical pulse, and becomes the reference light, d is c by a delay fiber The reference light e1 after being subjected to external pressure by being delayed is a combined output with b and d as inputs. The forward x of the e1 output is a portion where b does not overlap: the intermediate portion y of the reference light portion e1 output is b The part where d overlaps: The part where interference occurs: Interfering light part The rear z of the e1 output is the part where d does not overlap: Referenced light part
〔図４〕本発明の検出部を示す。
光センサ部から送られた信号ｅ１は検出部に信号ｅ２として届く。ｅ２は光ー電気変換器Ｆで電気信号ｆに変換され、サンプル・ホールド回路Ｇ，Ｈ，Ｉに送られる。
サンプル・ホールド回路Ｇのサンプルタイミングｇ、Ｈのサンプルタイミングｈ，Ｉのサンプルタイミングｉにてホールドされた電気信号ｊ、ｋ、ｌは演算回路Ｊに入る。
演算回路Ｊでは、ｊ、ｋ、ｌはデジタル信号化されて、参照光と被参照光との位相差が演算処理されて、位相差の関数ｍとして出力する。FIG. 4 shows a detection unit of the present invention.
The signal e1 sent from the optical sensor unit reaches the detection unit as a signal e2. e2 is converted into an electric signal f by the photoelectric converter F and sent to the sample and hold circuits G, H, and I.
The electric signals j, k, and l held at the sample timings g and H of the sample and hold circuit G and the sample timings i and i of the sample and hold circuit G enter the arithmetic circuit J.
In the arithmetic circuit J, j, k, and l are converted into digital signals, the phase difference between the reference light and the reference light is subjected to arithmetic processing, and output as a function m of the phase difference.
〔図５〕本発明の検出部（図４）の動作タイムチャートを示す。
ｅ２、ｆは受信信号の光信号と光ー電気変換された電気信号パルス
ｇは参照光部ｘをサンプルするタイミングパルス位置
ｈは干渉光部ｙをサンプルするタイミングパルス位置
ｉは被参照光部ｚをサンプルするタイミングパルス位置FIG. 5 shows an operation time chart of the detection unit (FIG. 4) of the present invention.
e2 and f are the optical signals of the received signal and the electrical-to-electrically converted electrical signal pulse g is the timing pulse position for sampling the reference light part x, h is the timing pulse position for sampling the interference light part y, i is the referenced light part z Timing pulse position to sample
Ａ１，Ａ２，Ｂ１：分波器、合波器
Ｄ１、Ｄ２：遅延用光ファイバ
Ｃ２、Ｃ２：外圧部分
Ｅ１、Ｅ２：反射鏡
Ｆ：光ー電気変換器
Ｇ，Ｈ，Ｉ：サンプル・ホールド回路
Ｊ：演算回路A1, A2, B1: Demultiplexer, multiplexer D1, D2: Delay optical fiber C2, C2: External pressure part E1, E2: Reflector F: Opto-electric converter G, H, I: Sample and hold circuit J: Arithmetic circuit
Claims (1)
計測用光パルスを分波器により二つに分波してその一方を参照光パルスとすると共に他方を外圧により位相変化を受ける被参照光パルスとし、前記参照光パルスの後部と前記被参照光パルスの前部が重なる時間位置まで前記被参照光パルスを遅らせた後、その被参照光パルスと前記参照光パルスとを合波器により合波し、その合波パルスの前方の参照光のみの部分を参照光部、中間の参照光と被参照光が重なった部分を干渉光部、後方の被参照光のみの部分を被参照光部とする時分割多重光パルスを出力とする光センサ部と、
前記光センサ部から出力される前記時分割多重光パルスから、前記参照光部の電気信号レベル、前記被参照光部の電気信号レベル、及び前記干渉光部の電気信号レベルのそれぞれを得て、それらの電気信号レベルに基づいて、参照光と被参照光との位相差の関数を損失変動による誤差分が含まれない値として求め、それを干渉信号出力とする検出部と、
を備えたことを特徴とする光ファイバセンサ。 In an optical fiber sensor using light interference,
The measurement optical pulse is demultiplexed into two by a demultiplexer, one of which is used as a reference light pulse and the other as a reference light pulse that undergoes a phase change due to external pressure, and the rear part of the reference light pulse and the reference light After the reference light pulse is delayed until the time position where the front part of the pulse overlaps, the reference light pulse and the reference light pulse are combined by a multiplexer, and only the reference light in front of the combined pulse is An optical sensor unit that outputs a time-division-multiplexed optical pulse with a reference light unit as a part, a part where the intermediate reference light and the reference light overlap with each other as an interference light part, and a rear reference light only part as a reference light part When,
From the time-division multiplexed optical pulse output from the optical sensor unit, obtaining an electrical signal level of the reference light unit, an electrical signal level of the referenced light unit, and an electrical signal level of the interference light unit, Based on those electrical signal levels, a function of the phase difference between the reference light and the reference light is determined as a value that does not include an error due to loss variation, and a detection unit that uses it as an interference signal output;
An optical fiber sensor comprising:
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| JP6002329B2 (en) * | 2013-07-25 | 2016-10-05 | 白山工業株式会社 | Optical interference sensor and measurement system using the same |
| JP7351365B1 (en) | 2022-03-17 | 2023-09-27 | 沖電気工業株式会社 | Optical fiber sensor and Brillouin frequency shift measurement method |
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