JP2626726B2 - Optical fiber type phase element - Google Patents
Optical fiber type phase elementInfo
- Publication number
- JP2626726B2 JP2626726B2 JP1227217A JP22721789A JP2626726B2 JP 2626726 B2 JP2626726 B2 JP 2626726B2 JP 1227217 A JP1227217 A JP 1227217A JP 22721789 A JP22721789 A JP 22721789A JP 2626726 B2 JP2626726 B2 JP 2626726B2
- Authority
- JP
- Japan
- Prior art keywords
- refractive index
- cladding
- optical fiber
- core
- phase element
- 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 - Fee Related
Links
Landscapes
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
Description
【発明の詳細な説明】 「産業上の利用分野」 この発明は光センサ、光干渉計、光通信などにおい
て、光波の偏波状態の変換や補正などに用いられ、特に
広い波長帯域にわたって直交直線偏波間にほゞ一定の位
相差を与えることができるようにした光ファイバ形位相
素子に関する。The present invention is used for conversion or correction of the polarization state of a light wave in an optical sensor, an optical interferometer, an optical communication, and the like. The present invention relates to an optical fiber type phase element capable of giving a substantially constant phase difference between polarized waves.
「従来の技術」 従来の広帯域光位相素子としては、空間伝搬光学系に
おいて用いられるバルク形素子のフレネル斜方プリズム
があった。これは第６図に示すような構造をしており、
入射光はガラス−空気境界面で２回の全反射を受けた後
出射される。光波はその全反射の際に、二つの偏波方向
で異なる位相推移を受けるが、これは入射角とガラスの
屈折率とのみに依存し、光波の波長には依存しないの
で、出射光の二つの直交直線偏波成分間には、広い波長
帯域にわたって一定の位相差が付けられることになる。"Prior Art" As a conventional broadband optical phase element, there has been a Fresnel oblique prism of a bulk type used in a space propagation optical system. This has a structure as shown in FIG.
The incident light is emitted after undergoing two total reflections at the glass-air interface. Light waves undergo different phase shifts in the two polarization directions during their total reflection, but this depends only on the angle of incidence and the refractive index of the glass, and not on the wavelength of the light waves. A constant phase difference is provided between the two orthogonal linear polarization components over a wide wavelength band.
「発明が解決しようとする課題」 以上述べたように、従来の広帯域光位相素子はフレネ
ル斜方プリズムのようなバルク形素子であった、このた
め光ファイバ回路系への組み込みが困難であるという欠
点があった。[Problems to be Solved by the Invention] As described above, the conventional broadband optical phase element is a bulk-type element such as a Fresnel oblique prism, and therefore, it is difficult to incorporate it into an optical fiber circuit system. There were drawbacks.
一方、位相素子として動作するためには、直交直線偏
波成分間の位相速度に差があればよい、この点から非軸
対称光ファイバを位相素子として使用することが考えら
える。確かに多くの非軸対称光ファイバにおいて、直交
偏波成分間の位相差がほゞ一定になる帯域が存在する
が、この帯域内に第一高次伝搬モードの遮断周波数が存
在するために帯域が制限され、広帯域位相素子として使
用することはできない。On the other hand, in order to operate as a phase element, it suffices if there is a difference in phase velocity between orthogonal linearly polarized components. From this point, it can be considered that a non-axisymmetric optical fiber is used as a phase element. Certainly, in many non-axially symmetric optical fibers, there is a band in which the phase difference between orthogonal polarization components is almost constant, but since the cutoff frequency of the first higher-order propagation mode exists in this band, the band is , And cannot be used as a broadband phase element.
この発明の目的は光ファイバ回路系への組み入れが容
易で、しかも広帯域で使用可能な光ファイバ形位相素子
を提供することにある。An object of the present invention is to provide an optical fiber type phase element which can be easily incorporated into an optical fiber circuit system and can be used in a wide band.
「課題を解決するための手段」 この発明によれば、断面が円形のコアと、そのコアの
外周上にそれに対して偏心して形成され、外周が円形を
なし、かつ上記コアの屈折率よりも低い屈折率の中間ク
ラッドと、その中間クラッドの外周上にこれと同心に形
成され、外周が円形をなし、かつ上記コアの屈折率より
低く、上記中間クラッドの屈折率よりも高い屈折率と
し、かつコア、中間クラッドの位置、断面形状を選定し
て全体の屈折率分布が非軸対称とされている。更にこの
光ファイバの等価屈折率が、基本伝搬モードでクラッド
の屈折率より大で、高次伝搬モードでクラッドの屈折率
より小となり、かつｘ偏波成分およびこれと直交するｙ
偏波成分を通すようにクラッド、コア、中間クラッドの
各屈折率が選定されている。According to the present invention, according to the present invention, a core having a circular cross section is formed on the outer periphery of the core so as to be eccentric to the core, the outer periphery forms a circle, and the refractive index of the core is higher than that of the core. An intermediate cladding with a low refractive index, formed concentrically on the outer periphery of the intermediate cladding, having a circular outer periphery, and having a refractive index lower than the refractive index of the core and higher than the refractive index of the intermediate cladding, In addition, the position and the cross-sectional shape of the core and the intermediate cladding are selected to make the entire refractive index distribution non-axisymmetric. Further, the equivalent refractive index of the optical fiber is larger than the refractive index of the cladding in the fundamental propagation mode, smaller than the refractive index of the cladding in the higher-order propagation mode, and is an x-polarized component and y orthogonal to this.
Refractive indices of the cladding, core, and intermediate cladding are selected so as to pass the polarization component.
「作 用」 この発明の位相素子によれば屈折率分布が非軸対称で
あるため、直交偏波成分間の位相差がほゞ一定な帯域が
存在し、位相素子として作用し、しかも、等価屈折率が
基本伝搬モードでクラッドの屈折率より大であり、高次
伝搬モードでクラッドの屈折率より小であるため、この
中間クラッドの存在により位相差一定の帯域内で第一高
次モードが抑圧される。つまり等価屈折率がクラッドの
屈折率より大きく、かつコアの屈折率より小さい光モー
ド（基本伝搬モード）が伝搬し、等価屈折率がクラッド
の屈折率よりも小さい、高次伝搬の光モードは伝搬しな
い、これは中間クラッドが等価屈折率を下げる作用を
し、また高次伝搬モードの方が基本伝搬モードよりも等
価屈折率が低く、従って適当な中間クラッドを使用し
て、高次伝搬モードの等価屈折率をクラッドの屈折率よ
り下げて高次伝搬モードを遮断するが、基本伝搬モード
の等価屈折率はクラッドの屈折率より大きく、基本伝搬
モードは伝搬するようにする。このようにして広帯域位
相素子が光ファイバ構造で得られ、光ファイバ回路系へ
の組み入れが容易である。[Operation] According to the phase element of the present invention, since the refractive index distribution is non-axially symmetric, there is a band in which the phase difference between the orthogonal polarization components is almost constant, which acts as a phase element, Since the refractive index is larger than the refractive index of the cladding in the fundamental propagation mode and smaller than the refractive index of the cladding in the higher-order propagation mode, the presence of the intermediate cladding causes the first higher-order mode to be in a band with a constant phase difference. Be suppressed. That is, an optical mode (fundamental propagation mode) in which the equivalent refractive index is larger than the refractive index of the cladding and smaller than the refractive index of the core propagates, and an optical mode of higher-order propagation in which the equivalent refractive index is smaller than the refractive index of the cladding propagates. No, this is because the intermediate cladding acts to lower the equivalent index of refraction, and the higher order mode has a lower equivalent index than the fundamental mode, so using a suitable intermediate cladding, The higher-order propagation mode is cut off by lowering the equivalent refractive index than the cladding refractive index. However, the equivalent refractive index of the fundamental propagation mode is larger than that of the cladding, so that the fundamental propagation mode propagates. In this way, a broadband phase element is obtained with an optical fiber structure, and can be easily incorporated into an optical fiber circuit system.
「実施例」 第１図にこの発明の実施例の断面を示す。屈折率がnC
の外周断面が円形のクラッド11内にその軸芯O1に対し、
偏心して屈折率がnIの断面円形のコア12が埋込まれてい
る。こゝでnI＞nCとされている。この発明ではクラッド
11とコア12との間に中間クラッド13が介在される。中間
クラッド13の屈折率nDはクラッド11の屈折率nCよりも小
とされている。Embodiment FIG. 1 shows a cross section of an embodiment of the present invention. Refractive index is n C
With respect to its axis O 1 in the cladding 11 having a circular outer cross section,
Decentered refractive index circular cross section of the core 12 of the n I is embedded. Here, it is assumed that n I > n C. In this invention the cladding
Intermediate cladding 13 is interposed between 11 and core 12. Refractive index n D of the intermediate cladding 13 is smaller than the refractive index n C of the cladding 11.
この例では中間クラッド13の外周断面を円形とし、そ
の軸心をクラッド11の軸心O1と一致させた場合である。
中間クラッド13の面積が小さくなると中間クラッド13の
作用が弱くなる、この点からコア12の半径をａ、中間ク
ラッド13の半径をｂとする時、b/a＞1.2とする。またク
ラッド11とコア12との屈折率差が小さいと中間クラッド
13の効果が大となり、クラッド11とコア12との屈折率差
が大きいと中間クラッド13の効果が小となる。この点か
らnI＝nC（１＋ΔＩ）とする時、ΔＩ＜0.05とする。In this example the outer peripheral section of the intermediate cladding 13 is circular, the case in which to match the axis thereof with the axis O 1 of the clad 11.
When the area of the intermediate cladding 13 is reduced, the function of the intermediate cladding 13 is weakened. From this point, when the radius of the core 12 is a and the radius of the intermediate cladding 13 is b, b / a> 1.2. Also, if the refractive index difference between the cladding 11 and the core 12 is small,
The effect of the intermediate cladding 13 becomes small if the refractive index difference between the cladding 11 and the core 12 is large. When this point as n I = n C (1 + Δ I), and delta I <0.05.
この構成によれば、コア12が偏心しているため、全体
としての屈折率分布が非軸対称となり、直交偏波成分間
の位相差がほゞ一定になる帯域が存在し、しかも、この
帯域において中間クラッド13の存在により、第一高次伝
搬モードが抑圧され、広帯域の位相素子が得られる。コ
ア12が中間クラッド13と接した状態で、クラッド11の軸
心O1とコア12の軸心O2との間の距離ｃのコア半径ａに対
する比c/aを0.5、b/aを1.5、ΔＩを0.02、ΔＤ（nD＝nC
（１−ΔＤ））を0.01、nC＝1.458として、1.3〜1.55μ
ｍの波長帯域内で直交偏波成分間の位相差の誤差が±１
％、長さが数cmの素子が実現できた。第２図にこの位相
素子に近い素子の位相特性を示す。横軸は正規化周波数
Ｖ、縦軸は正規化伝搬定数差VBであり、VBの最大値の0.
98倍となる下限、上限の各周波数をVL,VHとした。According to this configuration, since the core 12 is decentered, the refractive index distribution as a whole becomes non-axially symmetric, and there is a band in which the phase difference between the orthogonal polarization components is almost constant. Due to the presence of the intermediate cladding 13, the first higher-order propagation mode is suppressed, and a broadband phase element is obtained. In a state where the core 12 is in contact with the intermediate cladding 13, the axis O 1 and 0.5 the ratio c / a to the core radius a distance c between the axial center O 2 of the core 12 of the cladding 11, the b / a 1.5 , 0.02 Δ I, Δ D (n D = n C
The (1-Δ D)) 0.01 , as n C = 1.458, 1.3~1.55μ
The error of the phase difference between the orthogonal polarization components within the wavelength band of m is ± 1.
%, An element having a length of several cm was realized. FIG. 2 shows the phase characteristics of an element close to this phase element. The horizontal axis is the normalized frequency V, and the vertical axis is the normalized propagation constant difference VB, the maximum value of VB being 0.
98 times become lower, and the respective frequency of the upper limit V L, and V H.
上述では屈折率分布が非軸対称になるように、コア12
の位置をクラッド11に対し偏心させたが、非軸対称コア
を用いてもよい。例えば第３図Ａに示すようにコア12を
クラッド11の軸心に位置させ、コア12の断面を楕円形と
する。屈折率分布が非軸対称になるように、非軸対称中
間クラッドを用いてもよい。例えば第３図Ｂに示すよう
に、クラッド11の軸心に断面円形のコア12を配し、中間
クラッド13をその断面外周が楕円形となるようにする。In the above description, the core 12 is set so that the refractive index distribution is non-axially symmetric.
Is eccentric with respect to the cladding 11, but a non-axisymmetric core may be used. For example, as shown in FIG. 3A, the core 12 is positioned at the axis of the clad 11, and the cross section of the core 12 is made elliptical. A non-axisymmetric intermediate cladding may be used so that the refractive index distribution is non-axisymmetric. For example, as shown in FIG. 3B, a core 12 having a circular cross section is arranged at the axis of the cladding 11, and the outer circumference of the intermediate cladding 13 is made elliptical.
第４図にこの発明による光ファイバ形位相素子を用い
て広帯域光ファイバ形円偏波偏光子を構成した例を示
す。つまり入射した任意偏波状態の光の左回りと右回り
との円偏波成分は、この発明が適用された光ファイバ形
広帯域λ/4素子21によってそれぞれ互いに直交する直線
偏波成分に変換され、これらのうち片方のみが光ファイ
バ形直線偏光子22によって選択され、その選択された成
分は、この発明が適用された光ファイバ形広帯域λ/4素
子23に通されて、円偏波成分に変換される。このように
して任意偏波状態の光から所望の回転方向を持つ円偏波
成分のみを取り出すことができる。この場合各素子21,2
2,23は光ファイバで構成され、これら間の接続が容易で
あり、かつこの発明の適用により広い波長帯域にわたっ
て動作するものが得られる。FIG. 4 shows an example in which a broadband optical fiber type circularly polarized light polarizer is constructed using the optical fiber type phase element according to the present invention. In other words, the left-handed and right-handed circularly polarized light components of the incident light of arbitrary polarization state are converted into mutually orthogonal linearly polarized light components by the optical fiber type broadband λ / 4 element 21 to which the present invention is applied. Of these, only one of them is selected by the optical fiber type linear polarizer 22, and the selected component is passed through the optical fiber type broadband λ / 4 element 23 to which the present invention is applied, and becomes a circularly polarized component. Is converted. In this manner, only a circularly polarized component having a desired rotation direction can be extracted from light in an arbitrary polarization state. In this case, each element 21,2
Reference numerals 2 and 23 are composed of optical fibers, the connection between them is easy, and the present invention can operate over a wide wavelength band.
第５図にこの発明による光ファイバ形位相素子を用い
たコヒーレント光通信方式を示す。レーザ24からの直線
偏波光はスイッチ25により光ファイバ26,27の各一端に
交互に切替え供給され、一方の光ファイバ26にはこの発
明が適用された光ファイバ形λ/2位相素子28が挿入され
てあり、これを通った光は偏光状態が90゜変えられる。
光ファイバ26,27の各他端からの光は偏光選択性カップ
ラ29で合成されて出力される。従って偏光選択性カップ
ラ29から二つの偏光状態の光が交互に出力される。この
場合、光ファイバ形λ/2位相素子28は光ファイバ26に容
易に接続することができ、また光ファイバ形λ/2位相素
子28は広帯域であるため、多波長の光通信に利用でき
る。FIG. 5 shows a coherent optical communication system using an optical fiber type phase element according to the present invention. The linearly polarized light from the laser 24 is alternately switched and supplied to each end of optical fibers 26 and 27 by a switch 25, and an optical fiber type λ / 2 phase element 28 to which the present invention is applied is inserted into one optical fiber 26. The polarization state of the light passing therethrough is changed by 90 °.
Light from the other ends of the optical fibers 26 and 27 are combined by the polarization selective coupler 29 and output. Therefore, two polarized light beams are alternately output from the polarization selective coupler 29. In this case, the optical fiber type λ / 2 phase element 28 can be easily connected to the optical fiber 26, and since the optical fiber type λ / 2 phase element 28 has a wide band, it can be used for multi-wavelength optical communication.
「発明の効果」 以上述べたようにこの発明によれば光ファイバ構造で
あるため、光ファイバ回路系への組み込みを容易に行う
ことができ、かつ中間クラッドの存在により、第一高次
伝搬モードが抑圧され、直交偏波成分間にほゞ一定の位
相差を与える波長帯域が広い特徴がある。[Effect of the Invention] As described above, according to the present invention, since the present invention has an optical fiber structure, it can be easily incorporated into an optical fiber circuit system, and the presence of the intermediate cladding allows the first higher-order propagation mode Is suppressed, and the wavelength band that gives a substantially constant phase difference between orthogonal polarization components is wide.
第１図はこの発明の実施例を示す断面図、第２図はその
位相特性図、第３図A,Bはそれぞれこの発明の他の実施
例を示す断面図、第４図はこの発明を適用したλ/4素子
を利用した広帯域円偏波偏光子を示すブロック図、第５
図はこの発明を適用したλ/2素子を利用したコヒーレン
ト光通信方式を示すブロック図、第６図は従来の位相素
子を示す斜視図である。1 is a cross-sectional view showing an embodiment of the present invention, FIG. 2 is a phase characteristic diagram thereof, FIGS. 3A and 3B are cross-sectional views showing other embodiments of the present invention, and FIG. FIG. 5 is a block diagram showing a wide-band circularly-polarized polarizer using an applied λ / 4 element.
FIG. 1 is a block diagram showing a coherent optical communication system using a λ / 2 element to which the present invention is applied, and FIG. 6 is a perspective view showing a conventional phase element.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 山下 榮▲吉▼ 東京都八王子市めじろ台２―49―３ (72)発明者 赤澤 優 東京都渋谷区道玄坂１丁目21番６号 日 本航空電子工業株式会社内 (56)参考文献 特開 昭62−47607（ＪＰ，Ａ) 特開 昭62−283304（ＪＰ，Ａ) ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Sakae Yamashita 2-49-3, Mejirodai, Hachioji-shi, Tokyo (72) Inventor Yu Akazawa 1-21-6 Dogenzaka, Shibuya-ku, Tokyo Japan Aviation Electronics Industry (56) References JP-A-62-47607 (JP, A) JP-A-62-283304 (JP, A)
Claims (1)
のコアを有する光ファイバよりなり、 前記コアと前記クラッドとの間に、屈折率が前記クラッ
ドのそれよりも低い中間クラッドが介在され， かつ全体の屈折率分布が非軸対称とされ、 前記光ファイバの等価屈折率が、基本伝播モードにおい
て、前記クラッドの屈折率より大で、高次伝播モードに
おいて前記クラッドの屈折率より小となり、かつｘ偏波
成分およびこれと直交するｙ偏波成分を通すように、前
記クラッド、前記コア、前記中間クラッドの各屈折率が
選定されていることを特徴とする光ファイバ形位相素
子。1. An optical fiber having a core having a refractive index higher than that of a surrounding clad, wherein an intermediate cladding having a refractive index lower than that of the cladding is interposed between the core and the cladding. , And the entire refractive index distribution is non-axially symmetric, and the equivalent refractive index of the optical fiber is larger than the refractive index of the cladding in the fundamental propagation mode and smaller than the refractive index of the cladding in the higher-order propagation mode. An optical fiber type phase element, wherein each refractive index of the clad, the core, and the intermediate clad is selected so as to pass an x-polarized component and a y-polarized component orthogonal thereto.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1227217A JP2626726B2 (en) | 1989-09-01 | 1989-09-01 | Optical fiber type phase element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1227217A JP2626726B2 (en) | 1989-09-01 | 1989-09-01 | Optical fiber type phase element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0389305A JPH0389305A (en) | 1991-04-15 |
| JP2626726B2 true JP2626726B2 (en) | 1997-07-02 |
Family
ID=16857333
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1227217A Expired - Fee Related JP2626726B2 (en) | 1989-09-01 | 1989-09-01 | Optical fiber type phase element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2626726B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101806934A (en) * | 2010-03-29 | 2010-08-18 | 哈尔滨工程大学 | Inner wall fused and embedded single-mode polarization maintaining fiber grating and preparation method thereof |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2679548B1 (en) * | 1991-07-25 | 1994-10-21 | Alsthom Cge Alcatel | METHOD FOR MANUFACTURING ACTIVE OPTICAL FIBERS. |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0762725B2 (en) * | 1985-08-27 | 1995-07-05 | 日立電線株式会社 | Optical fiber type polarizer |
| JPS62283304A (en) * | 1986-05-31 | 1987-12-09 | Hitachi Cable Ltd | Absolute single polarizing plane maintaining optical fiber |
-
1989
- 1989-09-01 JP JP1227217A patent/JP2626726B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101806934A (en) * | 2010-03-29 | 2010-08-18 | 哈尔滨工程大学 | Inner wall fused and embedded single-mode polarization maintaining fiber grating and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0389305A (en) | 1991-04-15 |
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