JPS5915905A - Optical fiber which maintains plane of plarization - Google Patents

Optical fiber which maintains plane of plarization

Info

Publication number
JPS5915905A
JPS5915905A JP57126215A JP12621582A JPS5915905A JP S5915905 A JPS5915905 A JP S5915905A JP 57126215 A JP57126215 A JP 57126215A JP 12621582 A JP12621582 A JP 12621582A JP S5915905 A JPS5915905 A JP S5915905A
Authority
JP
Japan
Prior art keywords
core
optical fiber
long axis
elliptical
polarization
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.)
Pending
Application number
JP57126215A
Other languages
Japanese (ja)
Inventor
Masaharu Niizawa
新沢　正治
Toshihide Tokunaga
徳永　利秀
Hiroshi Kajioka
博 梶岡
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Cable Ltd
Original Assignee
Hitachi Cable Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Hitachi Cable Ltd filed Critical Hitachi Cable Ltd
Priority to JP57126215A priority Critical patent/JPS5915905A/en
Publication of JPS5915905A publication Critical patent/JPS5915905A/en
Pending legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/105—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type having optical polarisation effects
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/10—Internal structure or shape details
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/30—Polarisation maintaining [PM], i.e. birefringent products, e.g. with elliptical core, by use of stress rods, "PANDA" type fibres
    • C03B2203/302—Non-circular core cross-sections

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Organic Chemistry (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

PURPOSE:To attenuate quickly the unnecessary light shifted to the other axis by making the long axis direction of an elliptical clad covering a core different from the long axis direction of an elliptical jacket covering a clad. CONSTITUTION:A core 4 having an elliptical sectional shape is coated with a clad 3 having an elliptical sectional shape in such a way that the long axis direction of said clad is in the same direction as the long axis direction of the core 4. The outside circumference thereof is coated with a jacket 2 having a sectional shape differing by 45-90 deg. in the angle in the long axis direction, and a support 1 having a circular sectional outside surface is formed on the outside circumference thereof. The beat length is thus made shorter than the beat length of an ordinary optical fiber having a core of a circular section, and the light propagating in two planes of polarization is easily made into the light polarized purely in one direction by making the transmission loss of said light largely different, whereby the optical fiber having a large quenching ratio is obtd.

Description

【発明の詳細な説明】 本発明は光通信等に用いられる光ファイ・２に係り、／
Ｉ？に、偏波面保存光ファイバの改良に関するものであ
る。[Detailed Description of the Invention] The present invention relates to an optical fiber 2 used for optical communication, etc.
I? The present invention relates to improvements in polarization-maintaining optical fibers.

偏波面保存光ファイ・Ｓはシングルモード光ファイバの
コアに非対称な応力を加えて光の伝播定数の異なる固有
偏光軸を形成したもので、両軸を通る偏光のカンプリン
グを抑制して入射偏光の偏波面を長距離に亘って保持さ
せるようにしている。Polarization-maintaining optical fiber S is a single-mode optical fiber with asymmetrical stress applied to the core to form a unique polarization axis with different light propagation constants, which suppresses the polarization that passes through both axes and adjusts the incident polarization. The plane of polarization is maintained over a long distance.

しだがって、この偏波面保存光ファイバは通常のシング
ルモード光ファイバに比較して数多くの特長をもってい
る。例えば偏波面を乱すような状態がこれを布設した線
路に生じたときはそれを迅速に検出することができるの
で、各種の泪側用或いは各種センサとして多く用いられ
ている。Therefore, this polarization maintaining optical fiber has many features compared to a normal single mode optical fiber. For example, when a condition that disturbs the plane of polarization occurs on the line where it is installed, it can be quickly detected, so it is widely used for various types of ground-side applications or as various sensors.

従来の偏波面保存光ファイバは中心のコアとクラッドの
部分および最外層のザポートの外面は円形であるが、そ
の中間の、ジャケットは楕円形と１７であるのが普通で
ある。また、この偏波面保存光ファイバには固有偏光軸
のうちファースト軸或、いはスロー軸の方向に直線偏光
した光を入射させ。In conventional polarization-maintaining optical fibers, the central core, cladding, and outer surface of the outermost layer are circular, but the jacket in the middle is usually elliptical. Furthermore, light linearly polarized in the direction of the fast axis or the slow axis of the intrinsic polarization axes is input into this polarization-maintaining optical fiber.

この光の変化を検知して伝送路の異常を検知するように
している。しかしこの光ファイバの長手方向の偏波面の
変化やコアとクラッドの界面の不規則性、或いは外部応
力の変化等で多少の光カップリングがあると、一方の偏
光軸を伝播する偏光が他の偏光軸に移って出射端に出現
するようになる。Abnormalities in the transmission path are detected by detecting changes in this light. However, if there is some optical coupling due to changes in the plane of polarization in the longitudinal direction of the optical fiber, irregularities in the interface between the core and cladding, or changes in external stress, the polarized light propagating along one polarization axis may become polarized by the other. It moves to the polarization axis and appears at the output end.

このように偏光軸間を移動する割合をデシベル換算した
ものを消光比と呼んでおり、これを偏波面保存ゼトの良
否を示す・ξラメータとしている。The rate of movement between the polarization axes, converted into decibels, is called the extinction ratio, and is used as the ξ parameter that indicates the quality of polarization preservation.

また、カップリングによって他軸に移った光は情報に対
してノイズ的に作用するので、なるべく消光比の少いこ
とが要求きれる。従来の偏波面保存光ファイバは、ファ
ースト軸を伝播する光もスロー軸を伝播する光もその伝
送損失は殆んど等しいので、一旦他軸に移った光は急速
には減衰しないという欠点をもっていた。Furthermore, since light transferred to other axes due to coupling acts like noise on information, it is required that the extinction ratio be as small as possible. Conventional polarization-maintaining optical fibers have the disadvantage that the transmission loss of light propagating along the fast axis and light propagating along the slow axis is almost the same, so once the light moves to the other axis, it does not attenuate rapidly. .

本発明はＬ記従来技術の欠点を解消し、他軸に移った不
要光を速やかに減衰させることができる偏波面保存光フ
ァイ・ζを提供することを目的とし、その特徴とすると
ころは、コアとこのコアを被覆するクラッドとを断面楕
円状に形成すると共に、コアとクラッドとを埋設する楕
円断面のジャケラ１−の長軸方向とは異なる方向に長軸
を配置して構成したことにある。The present invention aims to eliminate the drawbacks of the prior art described in L and to provide a polarization-maintaining optical fiber that can quickly attenuate unnecessary light transferred to other axes, and its characteristics are as follows: The core and the cladding covering the core are formed to have an elliptical cross section, and the long axis is arranged in a direction different from the long axis direction of the jacket 1-, which has an elliptical cross section in which the core and the cladding are buried. be.

第１図は本発明の一実施例である偏波面保存光ファイバ
の断面図である。外面が円形新曲状であるザボート１の
中火部には長軸が＋１１・方向とな″りているジャケッ
ト２が存在し、その中心には長軸を縦方向としたコア４
および・クラッド３が埋設されている。FIG. 1 is a cross-sectional view of a polarization-maintaining optical fiber that is an embodiment of the present invention. There is a jacket 2 whose long axis is in the +11 direction in the medium heat section of the boat 1, whose outer surface has a newly curved circular shape, and a core 4 whose long axis is in the vertical direction.
and - cladding 3 is buried.

このように構成した場合は、コア４の長軸力督ｊ１を伝
播する偏光の規格化周波数■は次式で示される。In the case of this configuration, the normalized frequency {circle around (2)} of the polarized light propagating through the long-axis force beam j1 of the core 4 is expressed by the following equation.

２．１．。Ｂス　　　（１） Ｖ　＝　− λ 但し、ａ：コア４０半径 λ：伝播先の波長 ＋１（１：コア４の屈折率 △：コア４とクラッド３の比屈折率兼 ＋１Ｏｎ △＝ １１：クララ１３の屈折率 即ち、（１）式の条件を満足する周波数Ｖの縦方向の偏
光は減衰することが少くコア４中を伝送する７５；、上
記コア４とクラッド３の界面の不規則性等の影響で光カ
ップリングが生じて一部横方向の偏光に変化すると、こ
の横偏光はコア４の屈折率が異っているので（１）式の
条件からはずれて急速に減衰するようになる。しだがっ
て、この光ファイバの出射光は縦方向偏光だけの純粋な
信号となる。2.1. . Bsu (1) V = - λ However, a: Core 40 radius λ: Wavelength of propagation destination +1 (1: Refractive index of core 4 △: Relative refractive index of core 4 and cladding 3 combined +1 On △ = 11: Clara 13 In other words, vertically polarized light with a frequency V that satisfies the condition of equation (1) is transmitted through the core 4 with little attenuation. When optical coupling occurs due to this influence and the light is partially polarized in the lateral direction, this lateral polarized light deviates from the condition of equation (1) and rapidly attenuates because the refractive index of the core 4 is different. Therefore, the light emitted from this optical fiber becomes a pure signal of only longitudinally polarized light.

第１図の偏波面保存光ファイ・ミの製作法の一例を次に
説明する。外径２０＋ＷＩＩｌ、内径１７１１１Ｍの溶
融石英管の内壁にＭ　ＣＶ＋）法で８２０３を１０モル
％以上含む８１０２層を堆積させる。この層は第１図の
ジャケット２となる層である。その後クラッド層として
例えば５ｉＣｔ４等のソースガスを導入して上記ジャケ
ット層の上に５ｉ０２とほぼ同等の屈折率をもつ薄いク
ラッド層を堆積させる。最後に５ｉＯｔ４とＧｅＣｌ４
のノースガスを導入してクラッド層の内側により高屈折
率のコア層を堆積させる。An example of a method for manufacturing the polarization preserving optical fiber shown in FIG. 1 will be described next. An 8102 layer containing 10 mol % or more of 8203 is deposited on the inner wall of a fused silica tube having an outer diameter of 20+WIIl and an inner diameter of 17111M using the MCV+) method. This layer is the layer that becomes jacket 2 in FIG. Thereafter, a source gas such as 5iCt4 is introduced as a cladding layer, and a thin cladding layer having a refractive index substantially equal to that of 5i02 is deposited on the jacket layer. Finally, 5iOt4 and GeCl4
North gas is introduced to deposit a core layer with a higher refractive index inside the cladding layer.

このようにして形成した石英管の内部の圧力を外部の圧
力よりも５〜２０　＃ｎ　Ａｇ程程度正圧状態保ったま
ま一端より加熱し徐々に中吉化させると、第１図に相似
する断面構造をもつ偏波面保存光ファイバの母材が得ら
れるので、これを線引きずれは所望のものが得られる。When the internal pressure of the quartz tube thus formed is maintained at a positive pressure of about 5 to 20 #nAg relative to the external pressure, it is heated from one end and gradually turned into a medium, resulting in a cross section similar to that shown in Figure 1. Since a structured polarization-maintaining optical fiber base material is obtained, the desired line drag can be obtained from this.

なお、第１図のジャケット２はＢ２Ｏ３を含んでいるの
で純粋な石英管より形成したザボートｌよりも線膨張率
が大きい。その結果常温時はコア４の横方向には引張り
応力が作用している。Incidentally, since the jacket 2 in FIG. 1 contains B2O3, its coefficient of linear expansion is larger than that of the jacket 1 formed from a pure quartz tube. As a result, tensile stress acts on the core 4 in the lateral direction at room temperature.

第２図はジャケット２の長軸とコア４の長＋Ｉ！ｌｌ＋
方向とのなす角θの影響についての説明図である。Figure 2 shows the long axis of the jacket 2 and the length of the core 4 + I! ll+
It is an explanatory view about the influence of angle theta formed with a direction.

第１図はθ：９００の場合であるが、４５Ｑ〈θ・ζ９
００の範囲では円形のコア４をもつ偏波面保存光ファイ
バよりもビート長しが短くなることを確認している。な
お、ビート長Ｉ７は次式で表わされ、１．が短縮する程
非対称応力が増加するので光のカッシリングは生じにく
くなるどいつ好結果が得られる。Figure 1 shows the case of θ: 900, but 45Q〈θ・ζ9
It has been confirmed that in the range of 00, the beat length is shorter than that of a polarization maintaining optical fiber having a circular core 4. Note that the beat length I7 is expressed by the following formula: 1. The shorter the distance, the more asymmetrical stress increases, making it less likely that light will occur, and better results will be obtained.

但し、△β−１β、β２１　で２軸の光伝播定数差であ
る。However, Δβ−1β, β21 is the difference in the light propagation constants of the two axes.

寸だ、θ角の調節は堆積ガラス層であるジャケット２、
クラッド３、コア４のカラブス温度における粘性とカラ
ジス時の減圧量、カラジス時の石英管の回転速度等から
可能となる。The adjustment of the θ angle is done using jacket 2, which is a deposited glass layer.
This is possible based on the viscosity of the cladding 3 and core 4 at the Karabus temperature, the amount of pressure reduction during Karagis, the rotational speed of the quartz tube during Karagis, etc.

このようにして作られた楕円コアをもつ偏波面保存光フ
ァイバの特性の一例を述べると、ジャケット部の楕円率
（（長径−短径）／（長径士短径月は０６、コア部の楕
円率は０２、ジャケット２の長軸とコア４の長軸とのな
す角θは約８０°のもので、スロー軸とファースト軸に
伝搬する偏光の伝送損失は夫々３　ｄ　Ｂ　／　Ｋｍ以
下と１５　ｄ　Ｔ３　／　Ｋｍ以上である。また、ビー
ト長りは０６３μｍの波長光で３龍以下、消光比は４０
ｄＢ／Ｋｍ以上であった。An example of the characteristics of a polarization-maintaining optical fiber with an elliptical core made in this way is as follows: The ellipticity of the jacket part ((major axis - minor axis)/(major axis minus minor axis) is 06, and the ellipticity of the core part is The ratio is 02, the angle θ between the long axis of the jacket 2 and the long axis of the core 4 is about 80°, and the transmission loss of polarized light propagating to the slow axis and fast axis is 3 dB/Km or less, respectively, and 15 dT3/Km or more.Also, the beat length is 0.63 μm or less for wavelength light, and the extinction ratio is 40.
It was more than dB/Km.

本実施例の偏波面保存光ファイ・Ｓは１、ジャケット２
とコア４を共に楕円形とし、しかもその長軸方向に４５
°〜９００の角度θをもだせることによって、次のよう
な効果が得られる。In this example, the polarization maintaining optical fiber S is 1 and the jacket is 2.
and core 4 are both elliptical, and 45 mm in the long axis direction.
By being able to obtain an angle θ of 900° to 900°, the following effects can be obtained.

（１）、通常の円形断面のコアをもつものよりもビート
長の短いものが容易に得られる。(1) A core with a shorter beat length than a core with a normal circular cross section can be easily obtained.

（２）、２つの偏光面を伝播する光の伝送損失を大きく
相違させて純粋な一方向の偏光にすることが容易となり
、消光比の大きなものが容易に得られる。(2) It is easy to greatly differ the transmission loss of light propagating through two polarization planes to make it pure unidirectionally polarized light, and it is easy to obtain a large extinction ratio.

本発明の偏波面保存光ファイバは、威信光軸からこれと
４５０〜９００の角度をなす他軸に移った不要光を速や
かに減衰させて雑音光を能棒良く除去することができる
という効果が得られる。The polarization-maintaining optical fiber of the present invention has the effect of quickly attenuating unnecessary light transferred from the prestige optical axis to other axes forming an angle of 450 to 900 with this optical axis, and effectively eliminating noise light. can get.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明の一実施例である偏波面保育光ファイバ
の断面図、第２図はジャケットとコアの長袖のなす角θ
の影響の説明図である。 ■　サポート、２　）ヤケット、３　クラッド、４　コ
ア。 第 □　　！Figure 1 is a cross-sectional view of a polarization-maintaining optical fiber that is an embodiment of the present invention, and Figure 2 is an angle θ formed by the jacket and the long sleeve of the core.
FIG. ■ Support, 2) Jacket, 3 Clad, 4 Core. No. □!

Claims (2)

【特許請求の範囲】[Claims] （１）　　コアと、コアを被覆する断面楕円形のクラッ
ドと、クラッドを被拶する断面楕円形のジャケットとを
有する偏波面保存光ファイ・Ｓにおいて、ｎ；１記楕円
形クラッドの長軸方向と前記楕円形ジャケットの長袖方
向とが異なる方向であることを特徴とする偏波面保存光
ファイバ。(1) In a polarization preserving optical fiber S having a core, a cladding with an elliptical cross section covering the core, and a jacket with an elliptical cross section covering the cladding, n; 1 in the major axis direction of the elliptical cladding. and the long sleeve direction of the elliptical jacket are different directions. （２）　　上記コアとクラッドの長袖方向が、上記ジャ
ケットの長袖方向と４５０〜９０００角度を形成する範
囲である特許請求の範囲第１項記載の偏波面保存光ファ
イバ。(2) The polarization maintaining optical fiber according to claim 1, wherein the long sleeve direction of the core and the cladding forms an angle of 450 to 9000 with the long sleeve direction of the jacket.
JP57126215A 1982-07-20 1982-07-20 Optical fiber which maintains plane of plarization Pending JPS5915905A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP57126215A JPS5915905A (en) 1982-07-20 1982-07-20 Optical fiber which maintains plane of plarization

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP57126215A JPS5915905A (en) 1982-07-20 1982-07-20 Optical fiber which maintains plane of plarization

Publications (1)

Publication Number Publication Date
JPS5915905A true JPS5915905A (en) 1984-01-27

Family

ID=14929577

Family Applications (1)

Application Number Title Priority Date Filing Date
JP57126215A Pending JPS5915905A (en) 1982-07-20 1982-07-20 Optical fiber which maintains plane of plarization

Country Status (1)

Country Link
JP (1) JPS5915905A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01203226A (en) * 1988-02-10 1989-08-16 Ishihara Sangyo Kaisha Ltd Production of ferromagnetic iron oxide containing cobalt
US4896942A (en) * 1989-02-03 1990-01-30 Minnesota Mining And Manufacturing Company Polarization-maintaining optical fiber
US5067793A (en) * 1989-08-16 1991-11-26 U.S. Philips Corporation Polarization-maintaining single-mode optical fibre and method of making same
US5333232A (en) * 1992-03-16 1994-07-26 The Furukawa Electric Co., Ltd. Optical fiber for connection to waveguide type optical device and method of manufacturing the same
EP0907618A1 (en) * 1996-06-17 1999-04-14 Corning Incorporated Method of making polarization retaining fiber

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5699306A (en) * 1980-01-11 1981-08-10 Hitachi Ltd Single mode optical fiber which preserves plane of polarization
JPS5737305A (en) * 1980-08-18 1982-03-01 Hitachi Ltd Polarization plane preserving optical fiber

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5699306A (en) * 1980-01-11 1981-08-10 Hitachi Ltd Single mode optical fiber which preserves plane of polarization
JPS5737305A (en) * 1980-08-18 1982-03-01 Hitachi Ltd Polarization plane preserving optical fiber

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01203226A (en) * 1988-02-10 1989-08-16 Ishihara Sangyo Kaisha Ltd Production of ferromagnetic iron oxide containing cobalt
US4896942A (en) * 1989-02-03 1990-01-30 Minnesota Mining And Manufacturing Company Polarization-maintaining optical fiber
US5067793A (en) * 1989-08-16 1991-11-26 U.S. Philips Corporation Polarization-maintaining single-mode optical fibre and method of making same
US5333232A (en) * 1992-03-16 1994-07-26 The Furukawa Electric Co., Ltd. Optical fiber for connection to waveguide type optical device and method of manufacturing the same
EP0907618A1 (en) * 1996-06-17 1999-04-14 Corning Incorporated Method of making polarization retaining fiber
EP0907618A4 (en) * 1996-06-17 2002-07-17 Corning Inc Method of making polarization retaining fiber

Similar Documents

Publication Publication Date Title
US8958677B2 (en) Polarization-maintaining optical fiber
JP2007536580A (en) Long wavelength pure silica core single mode fiber and method of forming the fiber
US3997241A (en) Optical waveguide transmitting light wave energy in single mode
CN110346866B (en) Panda type polarization maintaining optical fiber
US4493530A (en) Single polarization optical fibers
CN111505762B (en) High-precision polarization maintaining optical fiber and preparation method thereof
KR20010020930A (en) Method of manufacturing polarization-maintaining optical fiber coupler
JPS5915905A (en) Optical fiber which maintains plane of plarization
JPH0798418A (en) Optical waveguide fiber and formation of optical waveguide fiber
JPH0389204A (en) Mono-polarized mode optical fiber and manufacture thereof
CN110346865B (en) Polarization maintaining optical fiber used in multiple bands
JPS6053285B2 (en) Constant polarization optical fiber
JPH0685005B2 (en) Constant polarization fiber and manufacturing method thereof
JPH11119036A (en) Plastic clad fiber
JPS59139005A (en) Fiber for maintaining linearly polarized light
JPH02157133A (en) Production of elliptic core type polarization plane maintaining optical fiber
JPS6033513A (en) Single linear polarization optical fiber
JPH0612364B2 (en) Polarization-maintaining optical fiber base material
JP3013010B2 (en) Optical fiber type polarizing element
JPS59135402A (en) Single polarization optical fiber
JPS58223102A (en) Optical fiber conserving plane of polarization and its manufacture
JPS6054644B2 (en) Single polarization fiber for very long wavelengths
JPS5918127A (en) Manufacture of polarization maintaining optical fiber
JPS61264303A (en) Single mode optical fiber for 1.5mu band
JPS6313521B2 (en)