JPS6337335B2 - - Google Patents
Info
- Publication number
- JPS6337335B2 JPS6337335B2 JP9393179A JP9393179A JPS6337335B2 JP S6337335 B2 JPS6337335 B2 JP S6337335B2 JP 9393179 A JP9393179 A JP 9393179A JP 9393179 A JP9393179 A JP 9393179A JP S6337335 B2 JPS6337335 B2 JP S6337335B2
- Authority
- JP
- Japan
- Prior art keywords
- frequency
- output
- local oscillation
- detection output
- optical fiber
- 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
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
- G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
- G01M11/333—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face using modulated input signals
-
- 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
- G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
- G01M11/335—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face using two or more input wavelengths
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Optical Communication System (AREA)
- Testing Of Optical Devices Or Fibers (AREA)
Description
【発明の詳細な説明】
本発明は両端が離れて配設されたケーブルにお
けるベースバンド周波数特性の測定方法に関す
る。光ケーブルが布設された後において伝送損失
の周波数特性を測定する必要がある。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring baseband frequency characteristics of a cable whose ends are separated. After the optical cable is installed, it is necessary to measure the frequency characteristics of transmission loss.
この種の測定技術としては従来周波数掃引法と
パルス法があるが、本発明は前者の改良について
なされたものである。 Conventional measurement techniques of this type include the frequency sweep method and the pulse method, and the present invention is an improvement on the former.
周波数掃引法は被測定ケーブルの送・受信端が
接近しているときはネツトワークアナライザを用
いて連続的に容易に上記測定をすることが出来
る。 In the frequency sweep method, when the transmitting and receiving ends of the cable to be measured are close to each other, it is possible to easily perform the above measurements continuously using a network analyzer.
しかるに送受信端が離れていると送受信機間の
同期信号を長距離伝送する必要があり、従来方法
をそのまま適用することが出来ない。 However, if the transmitting and receiving ends are far apart, it is necessary to transmit the synchronization signal between the transmitting and receiving devices over a long distance, and the conventional method cannot be applied as is.
一方、同期信号を送らずに測定する場合は送信
側と受信側で周波数情報を相互に連絡をとりなが
ら人為的に周波数を調整（送信側周波数に受信機
の同調周波数を一致させうる）しながら測定する
必要があり、測定に要する時間が長く、また精度
もよくない。 On the other hand, when measuring without sending a synchronization signal, the transmitter and receiver communicate frequency information and artificially adjust the frequency (the receiver's tuning frequency can match the transmitter's frequency). It is necessary to measure, the time required for measurement is long, and the accuracy is not good.
本発明は同期信号を送ることなく、以上の問題
点を解決する方法であり、以下図面を用いて本発
明の実施例を説明する。 The present invention is a method for solving the above problems without sending a synchronization signal, and embodiments of the present invention will be described below with reference to the drawings.
第１図に、本発明による光フアイバの周波数特
性測定法のブロツク図を示す。 FIG. 1 shows a block diagram of a method for measuring the frequency characteristics of an optical fiber according to the present invention.
光フアイバ送信端には、掃引型信号発生器１と
レーザー光源２がある。掃引型信号発生器１の
RF出力信号でレーザー光源２を光変調し、その
光変調波を被測定光フアイバ３に入射させる。被
測定光フアイバ３の受信端では、光検出器４によ
り、出射光を光電変換し、光変調波成分を検波す
る。 At the optical fiber transmission end, there is a sweep type signal generator 1 and a laser light source 2. Sweep type signal generator 1
The laser light source 2 is optically modulated by the RF output signal, and the optically modulated wave is made to enter the optical fiber 3 to be measured. At the receiving end of the optical fiber 3 to be measured, a photodetector 4 photoelectrically converts the emitted light and detects an optical modulation wave component.
第２図は掃引型信号発生器１の時間に対する変
調波の周波数の関係を示す。掃引時間がtsからtE
に変化するに従つて、変調周波数がfsからfEに変
化することを示す。ここでは、簡単のために被測
定光フアイバの周波数特性測定範囲をfsからfEと
する。第１図で光検波器４の出力は２分岐され、
その一方は狭帯域バンドパスフイルタ５に入る。
他の一方は、ヘテロダイン検波器６に入る。狭帯
域バンドパスフイルタ５の中心周波数はfsであ
り、掃引型信号発生器１のスタート時の周波数成
分fsを検出する。この出力は信号制御装置７に入
り、受信側の信号処理系全体をリセツトする機能
を持つ。このリセツトによつて局部発振器８が動
作し、局発周波数f1（第３図）がヘテロダイン検
波器６に入る。 FIG. 2 shows the relationship between the frequency of the modulated wave and the time of the sweep type signal generator 1. Sweep time from ts to t E
This shows that the modulation frequency changes from fs to fE as the value changes to fE. Here, for simplicity, the frequency characteristic measurement range of the optical fiber under test is assumed to be from fs to fE . In Fig. 1, the output of the photodetector 4 is branched into two,
One of them enters the narrowband bandpass filter 5.
The other one enters the heterodyne detector 6. The center frequency of the narrowband bandpass filter 5 is fs, and the frequency component fs at the start of the sweep type signal generator 1 is detected. This output enters the signal control device 7 and has the function of resetting the entire signal processing system on the receiving side. This reset causes the local oscillator 8 to operate, and the local oscillator frequency f 1 (FIG. 3) is input to the heterodyne detector 6.
一方、ヘテロダイン検波器６に光検波器４出力
が入り、ヘテロダイン検波され、局発周波数f1と
ヘテロダイン検波器６の中間周波数で決まる周波
数成分を出力する。 On the other hand, the output of the photodetector 4 enters the heterodyne detector 6, which performs heterodyne detection and outputs a frequency component determined by the local oscillation frequency f1 and the intermediate frequency of the heterodyne detector 6.
このとき、掃引時間の経過に伴つて、光検出器
４の出力の周波数は変化するが、局発周波数f1と
中間周波数で決まる周波数の信号がヘテロダイン
検波器６に入力したときのみ検波され出力される
（第４図）。局発周波数f1のときの検波出力が得ら
れると、その検波出力は信号処理装置９に入力
し、増巾され適当に信号処理され、デイスプレー
１０の縦軸に入る。一方、局発周波数f1に対応す
るヘテロダイン検波出力の時間信号が信号制御装
置７より出力され、デイスプレー１０の横軸に入
り、処理信号の出力とそのときの周波数がデイス
プレー１０上に記録される。 At this time, as the sweep time elapses, the frequency of the output of the photodetector 4 changes, but only when a signal with a frequency determined by the local frequency f1 and the intermediate frequency is input to the heterodyne detector 6, it is detected and output. (Figure 4). When the detection output at the local oscillation frequency f 1 is obtained, the detection output is input to the signal processing device 9, amplified and appropriately processed, and then entered on the vertical axis of the display 10. On the other hand, the time signal of the heterodyne detection output corresponding to the local frequency f 1 is output from the signal control device 7 and entered on the horizontal axis of the display 10, and the output of the processed signal and the frequency at that time are recorded on the display 10. be done.
一方、局発周波数f1のときの検波出力の一部は
信号制御装置７に入り、局部発振器８を再び動作
させて局発周波数をf2（第３図）に変える。この
局発周波数はヘテロダイン検波器６入り、光検波
器４からの出力が、前記したと同様、局発周波数
f2と中間周波数で決まる周波数になつたとき（掃
引時間の経過に伴つて生じる）、検波出力が得ら
れる。以下、同様に逐次局部発振周波数をデイス
クリートにかつ階段状に変化させ、そのときのヘ
テロダイン検波出力と、局部発振周波数をデイス
プレー１０上に記録する。 On the other hand, a part of the detection output at the local oscillator frequency f 1 enters the signal control device 7 to operate the local oscillator 8 again and change the local oscillator frequency to f 2 (FIG. 3). This local oscillation frequency enters the heterodyne detector 6, and the output from the optical detector 4 is the local oscillation frequency, as described above.
When the frequency determined by f 2 and the intermediate frequency is reached (which occurs as the sweep time elapses), the detected output is obtained. Thereafter, similarly, the local oscillation frequency is successively changed discretely and stepwise, and the heterodyne detection output and local oscillation frequency at that time are recorded on the display 10.
以上の過程を第３図及び第４図に示す。 The above process is shown in FIGS. 3 and 4.
本測定法では掃引型信号発生器１および局部発
振器８の出力は、各発振周波数に対して一定の必
要がある。このとき、光検波器４の出力をPs局
部発振器８の出力をPLとすると、ヘテロダイン
検波出力はPsPLとなり、光フアイバの周波数特
性Psを求めることができる。第５図に、本測定
法による測定例を示す。 In this measurement method, the outputs of the sweep signal generator 1 and the local oscillator 8 must be constant for each oscillation frequency. At this time, if the output of the optical detector 4 is Ps and the output of the local oscillator 8 is P L , the heterodyne detection output is PsP L , and the frequency characteristic Ps of the optical fiber can be determined. FIG. 5 shows an example of measurement using this measurement method.
本図に示すように、周波数情報がデイスクリー
トに得られ、各周波数成分の減衰量の包絡線を結
ぶことにより、光フアイバの周波数特性を求める
ことができる。 As shown in this figure, frequency information is obtained discretely, and by connecting the envelopes of the attenuation amounts of each frequency component, the frequency characteristics of the optical fiber can be determined.
ヘテロダイン検波器６の中間周波数の設定に特
に制限はない。 There are no particular restrictions on the setting of the intermediate frequency of the heterodyne detector 6.
本発明の特徴は、送信側の周波数を知るため
に、ヘテロダイン検波方式を用い、かつ局部発振
周波数をデイスクリートに変えて、送信側周波数
を待ち受け、ビート検出していることにある。従
つて従来より行なわれている送受信間で送信周波
数を知るために、同期信号や局部発振信号を送る
必要がない。又、ヘテロダイン検波方式により、
微弱な光検波器出力を高いSN比で検波すること
ができる。 The feature of the present invention is that in order to know the frequency of the transmitting side, a heterodyne detection method is used, the local oscillation frequency is changed to discrete, the frequency of the transmitting side is waited for, and beat detection is performed. Therefore, there is no need to send a synchronization signal or a local oscillation signal to know the transmission frequency between transmission and reception, which has been done in the past. In addition, due to the heterodyne detection method,
It is possible to detect weak optical detector output with a high signal-to-noise ratio.
第１図は本発明の測定法を示すブロツク図。
１……掃引型信号発生器、２……光源、３……
被測定光フアイバ、４……光検波器、５……狭帯
域バンドパスフイルタ、６……ヘテロダイン検波
器、７……信号制御装置、８……局部発振器、９
……信号処理装置、１０……デイスプレー、第２
図は送信光変調波の掃引周波数、第３図は局部発
振周波数、第４図はヘテロダイン検波出力、第５
図は周波数特性測定例を示す。
FIG. 1 is a block diagram showing the measurement method of the present invention. 1...Sweep type signal generator, 2...Light source, 3...
Optical fiber to be measured, 4... Optical detector, 5... Narrowband bandpass filter, 6... Heterodyne detector, 7... Signal control device, 8... Local oscillator, 9
...Signal processing device, 10...Display, 2nd
The figure shows the sweep frequency of the transmitted optical modulation wave, the third figure shows the local oscillation frequency, the fourth figure shows the heterodyne detection output, and the fifth figure shows the sweep frequency of the transmitted optical modulation wave.
The figure shows an example of frequency characteristic measurement.
Claims (1)
の一端より周波数が掃引可能な変調波により、強
度変調されたレーザー光を送信し他端で該レーザ
ー光を検波して掃引周波数成分に対応する検波出
力をヘテロダイン検波して該光フアイバケーブル
の特性を測定する方法において、前記検波出力を
分割し、一方の出力は特定周波数のみを通す狭
帯域バンドパスフイルタを通過せしめ該通過した
検波出力を局部発振器に作用して第１の局部発振
周波数信号を発生せしめ、該局部発振周波数信号
と分割した他の検波出力とによつてヘテロダイン
検波すること。次いで該ヘテロダイン検波出力
を分割し、その一方の出力を局部発振器に作用し
て第２の局部発振周波数信号を発生せしめ、該局
部発振周波数信号と掃引された検波出力とによつ
て別のヘテロダイン検波をすること。以下順次
を繰返して、再度掃引周波数が最初の特定周波
数に戻つたときにの作動に戻ることを特徴とす
る光フアイバケーブルの測定方法。1 Transmit intensity-modulated laser light using a modulated wave whose frequency can be swept from one end of an optical fiber cable whose ends are placed apart, and detect the laser light at the other end to generate a detection output corresponding to the swept frequency component. In the method of measuring the characteristics of the optical fiber cable by heterodyne detection of act to generate a first local oscillation frequency signal, and perform heterodyne detection using the local oscillation frequency signal and the other divided detection output. The heterodyne detection output is then divided, one output is applied to a local oscillator to generate a second local oscillation frequency signal, and the local oscillation frequency signal and the swept detection output are used to generate another heterodyne detection output. to do. A method for measuring an optical fiber cable, characterized in that the following steps are repeated in sequence and the operation returns when the sweep frequency returns to the initial specific frequency again.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9393179A JPS5618738A (en) | 1979-07-23 | 1979-07-23 | Measuring method for optical fiber cable |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9393179A JPS5618738A (en) | 1979-07-23 | 1979-07-23 | Measuring method for optical fiber cable |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5618738A JPS5618738A (en) | 1981-02-21 |
| JPS6337335B2 true JPS6337335B2 (en) | 1988-07-25 |
Family
ID=14096170
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9393179A Granted JPS5618738A (en) | 1979-07-23 | 1979-07-23 | Measuring method for optical fiber cable |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5618738A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0288829U (en) * | 1988-12-20 | 1990-07-13 | ||
| JPH0520917U (en) * | 1991-08-30 | 1993-03-19 | 三菱自動車工業株式会社 | Hirufuira Door |
-
1979
- 1979-07-23 JP JP9393179A patent/JPS5618738A/en active Granted
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0288829U (en) * | 1988-12-20 | 1990-07-13 | ||
| JPH0520917U (en) * | 1991-08-30 | 1993-03-19 | 三菱自動車工業株式会社 | Hirufuira Door |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5618738A (en) | 1981-02-21 |
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