JPH0378711A - Optical demultiplexing system - Google Patents
Optical demultiplexing systemInfo
- Publication number
- JPH0378711A JPH0378711A JP1216494A JP21649489A JPH0378711A JP H0378711 A JPH0378711 A JP H0378711A JP 1216494 A JP1216494 A JP 1216494A JP 21649489 A JP21649489 A JP 21649489A JP H0378711 A JPH0378711 A JP H0378711A
- Authority
- JP
- Japan
- Prior art keywords
- wavelength
- variable
- filter
- variable wavelength
- transmission
- 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.)
- Granted
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 50
- 230000005540 biological transmission Effects 0.000 claims abstract description 38
- 230000003247 decreasing effect Effects 0.000 abstract 1
- 238000001228 spectrum Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 5
- 238000004891 communication Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 230000010363 phase shift Effects 0.000 description 3
- BJQHLKABXJIVAM-UHFFFAOYSA-N bis(2-ethylhexyl) phthalate Chemical compound CCCCC(CC)COC(=O)C1=CC=CC=C1C(=O)OCC(CC)CCCC BJQHLKABXJIVAM-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 230000008033 biological extinction Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- 239000013598 vector Substances 0.000 description 1
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- Optical Communication System (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、波長分割多重光伝送・波長分割光交換システ
ムにおける光分波系に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical demultiplexing system in a wavelength division multiplexing optical transmission/wavelength division optical switching system.
波長分割多重光伝送・波長分割光交換システムは、多重
化された各々の波長に信号を乗せて伝送・交換を行う方
式であり、通信容量は波長の多重度に比例して増加する
。そのため、高度情報化社会の実現に向けた大容量光通
信技術として注目を集めている。この技術では、受信側
あるいは交換機で、多重化された波長信号の中から任意
の波長を選択する機能を有する波長分波器（波長フィル
タ）、すなわち、光分波系が必要であり、この光分波系
の特性が、波長多重度に大きく影響している。Wavelength division multiplexing optical transmission/wavelength division optical switching systems are methods in which signals are transmitted and exchanged by placing signals on each multiplexed wavelength, and communication capacity increases in proportion to the degree of multiplexing of wavelengths. Therefore, it is attracting attention as a high-capacity optical communication technology aimed at realizing an advanced information society. This technology requires a wavelength demultiplexer (wavelength filter), in other words, an optical demultiplexing system, which has the function of selecting an arbitrary wavelength from multiplexed wavelength signals on the receiving side or exchange. The characteristics of the demultiplexing system greatly affect the wavelength multiplicity.
マツハ・ツエンダ−干渉計やエタロンで成る可変波長フ
ィルタを光分波系に用いた波長分割多重光伝送の実験が
行われている。マツハ・ツエンダ−干渉計で成る光分波
系を用いた例としてイノウニ（Ｋ、Ｉｎｏｕｅ）他著の
ジャーナル・オブ・ライトウニイブ・テクノロジー（Ｊ
ｏｕｒｎａｌ ｏｆ ＬｉｇｈｔｗａｖｅＴｅｃｈｎｏ
ｌｏｇい誌第６巻（１９８８年２月発行）３３９〜３４
５ページ記載の論文をあげることが出来る。Experiments are being conducted on wavelength division multiplexing optical transmission using a variable wavelength filter consisting of a Matsuha-Zehnder interferometer and an etalon in an optical demultiplexing system. An example of using an optical demultiplexing system consisting of a Matsuha-Zehnder interferometer is the Journal of Lightweight Technology (J) by Inoue K. et al.
our own of Lightwave Techno
log magazine volume 6 (published February 1988) 339-34
I can list a 5-page paper.
また、エタロンを光分波系に用いた例としてリン（Ｃ，
Ｌｉｎ）他著のエレクトロニクス・レターズ（Ｅｌｅｃ
ｔｒｏｎｉｃｓ Ｌｅｔｔｅｒｓ）誌第２４巻（１９８
８年９月発行）１２１５〜１２１７ページ記載の論文を
あげることが出来る。In addition, as an example of using an etalon in an optical demultiplexing system, phosphorus (C,
Electronics Letters (Elec Lin) et al.
tronics Letters) Volume 24 (198
I can cite the paper on pages 1215-1217 (Published September 2010).
上述の光分波系を用いた波長分割光交換の実験例として
は、ニシオ（Ｍ、Ｎ１５ｈｉｏ）他著の１９８８年９月
開催の第１４回ヨーロッパ光通信会議（Ｆｏｕｒｔｅｅ
ｎｔｈ Ｅｕｒｏｐｅａｎ Ｃｏｎｆｅｒｅｎｃｅ ｏ
ｎ ０ｐｔｉｃａｌ Ｃｏｍ−ｍｕｎｉｃａｔｉｏｎ）
論文集第２分冊４９〜５２ページ記載の論文をあげるこ
とが出来る。As an experimental example of wavelength division optical exchange using the above-mentioned optical demultiplexing system, the 14th European Conference on Optical Communications (Fourtee
nth European Conference o
n 0ptical Com-communication)
I can cite the papers listed on pages 49-52 of Volume 2 of the collection of papers.
〔発明が解決しようとする課題〕
しかしながら、波長分割多重光伝送・波長分割光交換シ
ステムに用いる従来の光分波系には、次のような解決す
べき課題が存在する。従来の光分波系は、１個の可変波
長フィルタで構成されていた。この可変波長フィルタを
使って波長多重化信号の中から１つの波長信号を選択す
ると、フィルタの透過特性にしたがって、選択すべき波
長以外の光もわずかながら透過してしまう。この様子を
第３図（ｂ）に示す。これら選択すべき波長以外の光が
雑音光となり、受信時の誤り率を劣化させてしまう。所
定の誤り率を得るためには、雑音光成分を低減する、す
なわち近接波長間のクロストークな小さくしなければな
らない。そうして必要なりロストークが決まり、このク
ロストークを満たすように波長分割多重光伝送・波長分
割光交換とシステムの波長間隔が決定されていた。波長
間隔と可変波長フィルタの可変波長範囲とから波長多重
度が決まるわけで、つまり、単体の可変波長フィルタ、
すなわち光分波系の特性によってシステム全体の波長多
重度が決定されていた。[Problems to be Solved by the Invention] However, conventional optical demultiplexing systems used in wavelength division multiplexing optical transmission and wavelength division optical switching systems have the following problems to be solved. A conventional optical demultiplexing system consists of one variable wavelength filter. When this variable wavelength filter is used to select one wavelength signal from among wavelength multiplexed signals, a small amount of light other than the wavelengths to be selected is transmitted according to the filter's transmission characteristics. This situation is shown in FIG. 3(b). Light with wavelengths other than those to be selected becomes noise light, which deteriorates the error rate during reception. In order to obtain a predetermined error rate, it is necessary to reduce optical noise components, that is, to reduce crosstalk between adjacent wavelengths. Then, the necessary losstalk was determined, and the wavelength division multiplexing optical transmission, wavelength division optical switching, and wavelength spacing of the system were determined to satisfy this crosstalk. The wavelength multiplicity is determined by the wavelength interval and the variable wavelength range of the variable wavelength filter.
In other words, the wavelength multiplicity of the entire system was determined by the characteristics of the optical demultiplexing system.
本発明の目的は、波長多重度を増加させて大容量波長分
割多重光伝送・光交換システムを構築できる光分波系を
提供することにある。An object of the present invention is to provide an optical demultiplexing system that can increase the wavelength multiplexing degree and construct a large-capacity wavelength division multiplexing optical transmission/switching system.
本発明の光分波系は２つあり、その１つは、あらかじめ
定められた波長範囲の中から任意の光の波長を選択する
機能を有する可変波長フィルタと、前記可変波長フィル
タの可変波長範囲よ・りも広い透過バンド幅を有し、か
つ前記可変波長フィルタの可変波長範囲を透過バンド内
に含む固定波長フィルタとが直列に配列されて構成され
ることを特徴としている。もう１つの光分波系は、各々
の透過波長帯が異なる複数の前記の光分波系を並列に配
置し、各固定波長フィルタのバンド幅を、可変波長フィ
ルタの可変波長幅と透過バンド幅から決定される間隔で
ひとまとまりの波長群を形成している伝送光の各波長群
間の波長間隔よりも狭いバンド幅とした構成になってい
る。The optical demultiplexing system of the present invention has two parts, one of which is a variable wavelength filter that has a function of selecting an arbitrary wavelength of light from a predetermined wavelength range, and a variable wavelength range of the variable wavelength filter. It is characterized in that fixed wavelength filters having a transmission band width wider than that of the variable wavelength filter and whose transmission band includes the variable wavelength range of the variable wavelength filter are arranged in series. The other optical demultiplexing system has a plurality of optical demultiplexing systems with different transmission wavelength bands arranged in parallel, and the bandwidth of each fixed wavelength filter is set to the variable wavelength width of the variable wavelength filter and the transmission bandwidth of the variable wavelength filter. The configuration is such that the bandwidth is narrower than the wavelength interval between each wavelength group of the transmitted light forming a group of wavelengths at an interval determined from .
本発明の光分波系は可変波長フィルタと、第３図（ｃ）
に示すような特性の固定波長フィルタとか５−
ら構成されているので、可変波長フィルタが第３図（ｂ
）に示すような特性であっても、不要な波長領域は固定
波長フィルタでカットされ、雑音光成分が減少し、誤り
率が改善される。また、複数の可変波長フィルタを並列
配置し、各可変波長フィルタにそれぞれ固定波長フィル
タを直列接続した構成では、個々の光分波系、すなわち
、１個の可変波長フィルタと１個の固定波長フィルタで
成る各光分波系間のクロストークが従来に比べて小さく
なるので波長分割多重光伝送・波長分割光交換システム
の波長多重度を増加させることが可能となる。The optical demultiplexing system of the present invention includes a variable wavelength filter, and FIG. 3(c).
The variable wavelength filter consists of a fixed wavelength filter with the characteristics shown in Figure 3 (b).
), unnecessary wavelength regions are cut by a fixed wavelength filter, noise optical components are reduced, and the error rate is improved. In addition, in a configuration in which multiple variable wavelength filters are arranged in parallel and fixed wavelength filters are connected in series to each variable wavelength filter, each optical demultiplexing system, that is, one variable wavelength filter and one fixed wavelength filter Since the crosstalk between each optical demultiplexing system consisting of the following is smaller than that in the past, it becomes possible to increase the wavelength multiplexing degree of the wavelength division multiplexing optical transmission/wavelength division optical switching system.
可変波長フィルタ及び固定波長フィルタを各々複数用い
た構成で波長多重度が増加する原理について図面を参照
し“て説明する。第３図（ａ）に各可変波長フィルタへ
の入射スペクトル、（ｂ）ｔ４意の１つの可変波長フィ
ルタからの出射スペクトル（固定波長フィルタへの入射
スペクトルになる）、（Ｃ）に任意の１つの固定波長フ
ィルタからの出射スペクトルを示す。λ１１０〜λ１、
。、λ１２゜〜λ１□７、・・・は、−〇−
それぞれ各可変波長フィルタの可変波長範囲、またλ２
．８〜λ２１８は固定波長フィルタの透過バンド帯であ
り、
λ２．８〈λ１、。〈λ１、。〈λ２．９という関係が
ある。The principle of increasing the wavelength multiplicity in a configuration using a plurality of variable wavelength filters and fixed wavelength filters will be explained with reference to the drawings. Figure 3 (a) shows the incident spectrum to each variable wavelength filter, and (b) The output spectrum from one arbitrary variable wavelength filter at t4 (becomes the input spectrum to the fixed wavelength filter), and (C) shows the output spectrum from one arbitrary fixed wavelength filter. λ110 to λ1,
. , λ12° to λ1□7, ... are the variable wavelength range of each variable wavelength filter, and λ2
．． 8 to λ218 is the transmission band of the fixed wavelength filter, λ2.8<λ1,. <λ1,. There is a relationship of 〈λ2.9.
従来の波長分割光多重伝送・波長分割光交換シ、ステム
では、単体の可変波長フィルタで成る光分波系を用いて
いたので第３図（ｂ）に示すような出カスベクトルを利
用していた。この場合、図にも示したように可変波長フ
ィルタの透過特性（透過バンド幅や消光比）にしたがっ
て選択すべき波長以外の光も透過してしまう。これら、
選択波長以外の光が雑音光となり、受信時の誤り率を劣
化させる。所定の誤り率を得るためには、雑音光成分を
低減する、すなわち近接波長間のクロストークを小さく
しなければならない。このクロストークを満たすように
波長間隔が決定され、波長間隔と可変波長フィルタの可
変波長範囲とによって波長多重度が制限されていた。Conventional wavelength-division optical multiplexing transmission/wavelength-division optical switching systems and systems use an optical demultiplexing system consisting of a single variable wavelength filter, so they utilize output vectors as shown in Figure 3(b). Ta. In this case, as shown in the figure, light of wavelengths other than those to be selected according to the transmission characteristics (transmission bandwidth and extinction ratio) of the variable wavelength filter is also transmitted. these,
Light other than the selected wavelength becomes noise light and degrades the error rate during reception. In order to obtain a predetermined error rate, it is necessary to reduce optical noise components, that is, to reduce crosstalk between adjacent wavelengths. The wavelength spacing is determined to satisfy this crosstalk, and the wavelength multiplexing degree is limited by the wavelength spacing and the variable wavelength range of the variable wavelength filter.
しかしながら、本発明のように可変波長フィルタの出力
段に固定波長フィルタを直列に配置すれば、第３図（Ｃ
）に示すように自然放出光等の雑音光成分を低減するこ
とが出来る。そして、第２図に示すように、各可変波長
フィルタの可変波長範囲Δλ１１（ｉ＝１，２．・・・
、ｎ）、すなわち、λ１、。〜λ１１．．、λ１□。〜
λ１２ｎ、・・・をそれぞれ−まとまりの波長群として
、波長群どうしの間隔Δλを固定波長フィルタの透過バ
ンド幅Δλ２１ （ｊ＝１．２．・・・ｍ）に比べて広
く取れば、第３図を使って説明したように全ての波長の
選択に関して雑音光を低減できる。従って単体の可変波
長フィルタを用いた場合に比べて、波長多重度を大きく
することが出来る。However, if a fixed wavelength filter is arranged in series at the output stage of a variable wavelength filter as in the present invention, then as shown in FIG.
), noise light components such as spontaneous emission light can be reduced. As shown in FIG. 2, the variable wavelength range Δλ11 (i=1, 2...
, n), i.e., λ1,. ~λ11. ．． , λ1□. ~
If λ12n, . As explained using the figure, noise light can be reduced by selecting all wavelengths. Therefore, the wavelength multiplicity can be increased compared to the case where a single variable wavelength filter is used.
図面を参照して、本実施例を詳細に説明する。 This embodiment will be described in detail with reference to the drawings.
第１図は、本発明の一実旅例の光分波系を構成する可変
波長フィルタ群と固定波長フィルタ群の配置を示す。第
２図は、波長間隔と固定波長フィルタの透過バンド幅の
関係を説明する図である。第３図は、第１図の光分波系
を構成する可変波長フィルタと固定波長フィルタに入射
するスペクトルと出射スペクトルを示す図である。FIG. 1 shows the arrangement of a variable wavelength filter group and a fixed wavelength filter group constituting an optical demultiplexing system according to an example of the present invention. FIG. 2 is a diagram illustrating the relationship between the wavelength interval and the transmission bandwidth of a fixed wavelength filter. FIG. 3 is a diagram showing spectra entering and exiting the variable wavelength filter and the fixed wavelength filter that constitute the optical demultiplexing system shown in FIG.
可変波長フィルタ１１，１２，１３，１４．１５は互い
に並列配置され、それぞれ異なった可変波長範囲λ１１
０〜λ１１．．、λ１□０〜λ１□７、λ１３゜〜λ１
３ゎ、λ１４０〜λ１４１１％ λ１．。〜λ１５ｎを
有する。それぞれ異なった透過バンド帯λ２１８〜λ２
１８、λ２２８〜λ２２８、λ２３８〜λ２３８、λ２
４８〜λ２４Ｅ、λ２５８〜λ２．８を有する、固定波
長フィルタ２１，２２，２３，２４゜２５が、可変波長
フィルタ１１，１２，１３，１４゜１５の出力段に第１
図に示すように直列に配置される。可変波長フィルタと
しては、可変波長範囲９．５人（周波数域１２０ＧＨｚ
）多重波長数１６の特性を有する１、５μｍ帯の位相シ
フト制御型分布帰還型半導体レーザ（ＤＦＢ−ＬＤ）フ
ィルタを５個使用する。５個の位相シフト制御型ＤＦＢ
・ＬＤフィルタの透過波長の中心値の間隔は３００人と
する。また、固定波長フィルタとしては、透過バンドの
中央値が５個の位相シフト制御型ＤＦＢ−ＬＤフィルタ
の透過波長の中心値とほぼ一致９−
し、かつ透過バンド幅が２００人で、透過波長域と透過
阻止波長域とで透過率の比が１０ｄＢ以上ある干渉フィ
ルタを５個用いる。その結果、従来の１６波の伝送を大
きく上回る、１０−１１以下の誤り率で８０（１６Ｘ５
）波の波長多重光伝送、及び、波長分割光交換が可能と
なる。また、各デバイスの高性能化にともなって、さら
に波長多重度の増加が期待される。The variable wavelength filters 11, 12, 13, 14.15 are arranged in parallel with each other, and each has a different variable wavelength range λ11.
0~λ11. ．． , λ1□0~λ1□7, λ13°~λ1
3ゎ, λ140~λ1411% λ1. . ~λ15n. Different transmission bands λ218~λ2
18, λ228~λ228, λ238~λ238, λ2
Fixed wavelength filters 21, 22, 23, 24°25 having wavelengths of 48 to λ24E and λ258 to λ2.8 are connected to the first output stage of the variable wavelength filters 11, 12, 13, 14°15.
arranged in series as shown in the figure. As a variable wavelength filter, the variable wavelength range is 9.5 people (frequency range 120 GHz).
) Five 1.5 μm band phase shift controlled distributed feedback semiconductor laser (DFB-LD) filters having characteristics of 16 multiplexed wavelengths are used. 5 phase shift controlled DFBs
- The interval between the center values of the transmission wavelengths of the LD filter shall be 300 people. In addition, as a fixed wavelength filter, the median value of the transmission band is almost the same as the center value of the transmission wavelength of five phase shift control type DFB-LD filters, and the transmission band width is 200. Five interference filters are used, each having a transmittance ratio of 10 dB or more between the wavelength range and the transmission blocking wavelength range. As a result, the 80 (16X5
) Enables wavelength-multiplexed optical transmission and wavelength-division optical exchange of waves. Further, as the performance of each device improves, it is expected that the wavelength multiplicity will further increase.
なお、可変波長フィルタ及び固定波長フィルタの材料及
び組成、上述の実施例に限定する必要はなく、如何なる
半導体材料や誘電体材料などであってもよい。さらに可
変波長フィルタ及び固定波長フィルタの構造は、フィル
タ機能を有するものであれば如何なる構造であってもよ
い。Note that the materials and compositions of the variable wavelength filter and the fixed wavelength filter do not need to be limited to the above-mentioned embodiments, and may be any semiconductor material, dielectric material, or the like. Further, the structure of the variable wavelength filter and the fixed wavelength filter may be any structure as long as it has a filter function.
従来の波長分割多重光伝送・波長分割光交換システムで
は１６波多重が限度であったが、本発明によって８０波
以上の波長多重度が可能となる。Conventional wavelength division multiplexing optical transmission/wavelength division optical switching systems have a limit of 16 wavelengths, but the present invention enables wavelength division multiplexing of 80 or more wavelengths.
１０−10-
第１図は、本発明の一実施例の光分波系を構成する可変
波長フィルタと固定波長フィルタの配置を示す図、第２
図は、波長間隔と固定波長フィルタの透過バンド幅との
関係を説明する図である。
第３図は、第１図の光分波系を構成する可変波長フィル
タと固定波長フィルタの入射スペクトルと出射スペクト
ルを示す図である。
図において、
１１．１２，１３，１４．１５・・・・・・可変波長フ
ィルタ、
２１．２２，２３，２４．２５・・・・・・固定波長フ
ィルタ、
である。FIG. 1 is a diagram showing the arrangement of a variable wavelength filter and a fixed wavelength filter constituting an optical demultiplexing system according to an embodiment of the present invention, and FIG.
The figure is a diagram illustrating the relationship between the wavelength interval and the transmission bandwidth of a fixed wavelength filter. FIG. 3 is a diagram showing the incident spectrum and output spectrum of the variable wavelength filter and fixed wavelength filter that constitute the optical demultiplexing system of FIG. 1. In the figure, 11.12, 13, 14.15... variable wavelength filter, 21.22, 23, 24.25... fixed wavelength filter.
Claims (2)
の波長を選択する機能を有する可変波長フィルタと、前
記可変波長フィルタの可変波長範囲よりも広い透過バン
ド幅を有し、かつ前記可変波長フィルタの可変波長範囲
を透過バンド内に含む固定波長フィルタとが直列に配列
されて構成されることを特徴とする光分波系。(1) A tunable wavelength filter having a function of selecting an arbitrary wavelength of light from a predetermined wavelength range, and a tunable wavelength filter having a transmission bandwidth wider than the tunable wavelength range of the tunable wavelength filter; An optical demultiplexing system characterized in that a fixed wavelength filter whose transmission band includes a variable wavelength range of the filter is arranged in series.
数の可変波長フィルタを並列配置し、前記各可変波長フ
ィルタに、それぞれ透過バンド幅が異なる固定波長フィ
ルタを直列接続した構成とし、かつ、前記固定波長フィ
ルタの透過バンド幅を、前記可変波長フィルタの可変波
長幅と透過バンド幅から決まる間隔でひとまとまりの波
長群を形成している伝送光の各波長群間の波長間隔より
も狭く定めたことを特徴とする光分波系。(2) A plurality of variable wavelength filters having different variable wavelength ranges and transmission bandwidths are arranged in parallel, and each of the variable wavelength filters is connected in series with a fixed wavelength filter having a different transmission bandwidth, and The transmission band width of the wavelength filter is determined to be narrower than the wavelength interval between each wavelength group of transmission light forming a group of wavelengths at an interval determined by the variable wavelength width and transmission band width of the variable wavelength filter. An optical demultiplexing system featuring
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1216494A JP2702237B2 (en) | 1989-08-22 | 1989-08-22 | Optical demultiplexing system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1216494A JP2702237B2 (en) | 1989-08-22 | 1989-08-22 | Optical demultiplexing system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0378711A true JPH0378711A (en) | 1991-04-03 |
| JP2702237B2 JP2702237B2 (en) | 1998-01-21 |
Family
ID=16689312
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1216494A Expired - Fee Related JP2702237B2 (en) | 1989-08-22 | 1989-08-22 | Optical demultiplexing system |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2702237B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7287915B2 (en) | 2003-01-27 | 2007-10-30 | Ngk Insulators, Ltd. | Optical device |
| CN102313777A (en) * | 2011-07-26 | 2012-01-11 | 电子科技大学 | Detection apparatus for defects of inner and outer walls of pipeline based on remote field eddy current testing |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5412447U (en) * | 1977-06-28 | 1979-01-26 | ||
| JPS5532019A (en) * | 1978-08-26 | 1980-03-06 | Fujitsu Ltd | Branching filter of light wavelength region variable type |
| JPS5767910A (en) * | 1980-10-15 | 1982-04-24 | Fujitsu Ltd | Optical synthesizing and branching device |
| JPS61184938A (en) * | 1985-02-12 | 1986-08-18 | Mitsubishi Electric Corp | Optical wavelength multiplex transmitter |
-
1989
- 1989-08-22 JP JP1216494A patent/JP2702237B2/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5412447U (en) * | 1977-06-28 | 1979-01-26 | ||
| JPS5532019A (en) * | 1978-08-26 | 1980-03-06 | Fujitsu Ltd | Branching filter of light wavelength region variable type |
| JPS5767910A (en) * | 1980-10-15 | 1982-04-24 | Fujitsu Ltd | Optical synthesizing and branching device |
| JPS61184938A (en) * | 1985-02-12 | 1986-08-18 | Mitsubishi Electric Corp | Optical wavelength multiplex transmitter |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7287915B2 (en) | 2003-01-27 | 2007-10-30 | Ngk Insulators, Ltd. | Optical device |
| CN102313777A (en) * | 2011-07-26 | 2012-01-11 | 电子科技大学 | Detection apparatus for defects of inner and outer walls of pipeline based on remote field eddy current testing |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2702237B2 (en) | 1998-01-21 |
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