JP4504989B2 - Variable optical attenuator - Google Patents

Variable optical attenuator Download PDF

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JP4504989B2
JP4504989B2 JP2007071042A JP2007071042A JP4504989B2 JP 4504989 B2 JP4504989 B2 JP 4504989B2 JP 2007071042 A JP2007071042 A JP 2007071042A JP 2007071042 A JP2007071042 A JP 2007071042A JP 4504989 B2 JP4504989 B2 JP 4504989B2
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refractive index
optical fiber
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JP2008233384A (en
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郁昭 田中
幾太郎 大串
裕司 東
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Nippon Telegraph and Telephone Corp
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本発明は、１Ｗを超えるような高パワー光の光ファイバ伝送において、光レベルを適切に調整するための可変光減衰器に関するものである。   The present invention relates to a variable optical attenuator for appropriately adjusting an optical level in optical fiber transmission of high power light exceeding 1 W.

図５は従来の光減衰ファイバを用いた光減衰器を示す構成説明図である。図５において、１は光ファイバ、２は高パワー光、３は収納ケース、４は光減衰ファイバである。すなわち、１Ｗを超えるような高パワー光の光伝送システムにおいて、その高パワー光を光の状態で減衰させ、所要の光レベルに調節する方法として、光ファイバのコア内にリン（Ｐ）やコバルト（Ｃｏ）等の不純物をドープした光減衰ファイバ４が用いられている（例えば、特許文献１参照。）。図５に示すように、光ファイバ１に接続された光減衰ファイバ４は収納ケース３内に収納され、前記光ファイバ１及び光減衰ファイバ４には高パワー光２が伝送される。前記光減衰ファイバ４は、通過する高パワー光２を光ファイバ長手方向に分布させた不純物によって散乱させ、その通過した長さや不純物の濃度に応じて所要の損失を作り出している。   FIG. 5 is an explanatory diagram showing a configuration of an optical attenuator using a conventional optical attenuating fiber. In FIG. 5, 1 is an optical fiber, 2 is high power light, 3 is a storage case, and 4 is an optical attenuating fiber. That is, in an optical transmission system of high power light exceeding 1 W, as a method for attenuating the high power light in the state of light and adjusting it to a required light level, phosphorus (P) or cobalt is contained in the core of the optical fiber. An optical attenuating fiber 4 doped with an impurity such as (Co) is used (for example, see Patent Document 1). As shown in FIG. 5, the optical attenuating fiber 4 connected to the optical fiber 1 is accommodated in the accommodating case 3, and the high power light 2 is transmitted to the optical fiber 1 and the optical attenuating fiber 4. The optical attenuating fiber 4 scatters the high-power light 2 passing therethrough by impurities distributed in the longitudinal direction of the optical fiber, and creates a required loss according to the length of the light passing through and the concentration of impurities.

図６は従来の光カプラを用いた光減衰器を示す構成説明図である。図６において、１１は光ファイバ、１２は高パワー光、１３は収納ケース、１４は１：１０のような分岐比の大きい光カプラ、１５はコアレスファイバである。図６に示すように、光ファイバ１１には光カプラ１４が複数個接続され、各光カプラ１４にはコアレスファイバ１５が接続される。前記各光カプラ１４及びコアレスファイバ１５は収納ケース内に収納され、光ファイバ１１には高パワー光１２が伝送される。すなわち、１：１０のような分岐比の大きい光カプラを複数個接続して分配損を利用しながら光パワーを減衰させることも行われている。   FIG. 6 is an explanatory diagram showing a configuration of an optical attenuator using a conventional optical coupler. In FIG. 6, 11 is an optical fiber, 12 is high power light, 13 is a storage case, 14 is an optical coupler having a large branching ratio such as 1:10, and 15 is a coreless fiber. As shown in FIG. 6, a plurality of optical couplers 14 are connected to the optical fiber 11, and a coreless fiber 15 is connected to each optical coupler 14. Each of the optical couplers 14 and the coreless fiber 15 is housed in a housing case, and high power light 12 is transmitted to the optical fiber 11. That is, optical power is attenuated by connecting a plurality of optical couplers having a large branching ratio such as 1:10 and using distribution loss.

これら光減衰器の最大の欠点は、個々の光減衰器の損失値が固定化されているため、前記高パワー光を所要の光レベルに柔軟に調整できないということである。従って、所要の光レベルを得るためには、光伝送システムの受光特性や光線路の媒体損失に応じて前記固定光減衰器を選択する必要があった。   The greatest drawback of these optical attenuators is that the loss values of the individual optical attenuators are fixed, so that the high power light cannot be flexibly adjusted to the required optical level. Therefore, in order to obtain a required light level, it is necessary to select the fixed optical attenuator according to the light receiving characteristics of the optical transmission system and the medium loss of the optical line.

上記光減衰ファイバを用いた光減衰器の場合（図５参照）、長手方向を利用した減衰方法であることから、数ｍ〜十数ｍ長のファイバを収納ケース内に収容する必要があり、その構造もまた曲げ半径が小さ過ぎると大きな曲げ損失（漏洩光）が発生し光ケーブルや光コードの被覆を劣化させる恐れがあった。   In the case of the optical attenuator using the optical attenuating fiber (see FIG. 5), since it is an attenuation method using the longitudinal direction, it is necessary to accommodate a fiber having a length of several meters to several tens of meters in a storage case. If the bending radius of the structure is too small, a large bending loss (leakage light) is generated and there is a possibility that the coating of the optical cable or the optical cord is deteriorated.

また、上記光カプラを用いた光減衰器の場合（図６参照）は、分配損失を発生させるためのポートからの反射光を抑えると同時に、そのポート端から放射される光を減衰させるため、コアレスファイバ等によって光を分散させる構造が必要であった。なお、分散させた光によって生じた熱は収容ケース内の空気により吸収されるため、比熱の大きい空気においては温度低下に難点があることは言うまでもない。   Further, in the case of the optical attenuator using the optical coupler (see FIG. 6), the reflected light from the port for generating the distribution loss is suppressed, and at the same time, the light emitted from the port end is attenuated. A structure for dispersing light by using a coreless fiber or the like was necessary. In addition, since the heat generated by the dispersed light is absorbed by the air in the housing case, it goes without saying that there is a difficulty in lowering the temperature in air with a large specific heat.

特開平１０-２６８１５３号公報JP 10-268153 A 首藤義人 他著 「電子情報通信学会論文誌」電子情報通信学会出版 ２００３年３月 Ｖｏｌ．J８６−C Ｎｏ．３ ｐ．２５２−２６１Yoshito Suto et al. “Journal of the Institute of Electronics, Information and Communication Engineers” published by IEICE, March 2003, Vol. J86-C No. 3 p. 252-261

上述したように、従来における高パワー光の光レベル調整では、光減衰ファイバや光カプラの損失値が固定されているため、それらの長さや数を選択もしくは組み合わせて、所要の光レベルに調整しているのが現状であった。   As described above, in the conventional optical power level adjustment of high-power light, the loss value of the optical attenuating fiber or optical coupler is fixed, so the length or number of those is selected or combined to adjust to the required optical level. It was the current situation.

本発明は上記の事情に鑑みてなされたもので、１Ｗを超えるような高パワー光を所要の光レベルに調整できることにより、１Ｗを超えるような高パワー光の光ファイバ伝送においても、光線路設備や光伝送受信器に対して適切な光レベルを簡単に供給できるため、光伝送システムの信頼性や安全性を向上できる可変光減衰器を提供することを目的とする。   The present invention has been made in view of the above circumstances. By adjusting high power light exceeding 1 W to a required optical level, optical line equipment can be used in optical fiber transmission of high power light exceeding 1 W. Another object of the present invention is to provide a variable optical attenuator that can improve the reliability and safety of an optical transmission system because an appropriate optical level can be easily supplied to an optical transmission receiver.

上記目的を達成するために本発明は、光ファイバで伝送される高パワー光を光の状態で減衰させる可変光減衰器であって、光軸上で端面が突合わされた２本の光ファイバと、前記端面を含む各光ファイバの一部に充填され、高パワー光の通光下で光ファイバのコアの屈折率と略同一の屈折率となる液体状の屈折率整合剤と、前記２本の光ファイバの端面間隔を変化させる光ファイバ移動手段とを具備することを特徴とするものである。   In order to achieve the above object, the present invention provides a variable optical attenuator for attenuating high-power light transmitted through an optical fiber in the state of light, and two optical fibers having end faces butted on the optical axis, and A liquid refractive index matching agent filled in a part of each optical fiber including the end face and having a refractive index substantially the same as the refractive index of the core of the optical fiber under the passage of high-power light; And an optical fiber moving means for changing the distance between the end faces of the optical fiber.

また本発明は、前記可変光減衰器において、光ファイバ移動手段として、２本の光ファイバの端面間隔を、当該光ファイバのコア径（スポットサイズＷ０）に対して０〜１０Ｗ０の範囲で可動する光ファイバ移動手段を用いることを特徴とするものである。 In the variable optical attenuator, the optical fiber moving means in the variable optical attenuator may have an interval between the end faces of the two optical fibers in a range of 0 to 10 W 0 with respect to the core diameter (spot size W 0 ) of the optical fiber. The movable optical fiber moving means is used.

また本発明は、前記可変光減衰器において、屈折率整合剤として、高パワー光の通光前に光ファイバのコアの屈折率よりやや高めの屈折率を有し、高パワー光の通光下で屈折率が小さくなる屈折率整合剤を用いることを特徴とするものである。   In the variable optical attenuator, the refractive index matching agent may have a refractive index slightly higher than the refractive index of the core of the optical fiber before passing high power light as the refractive index matching agent. A refractive index matching agent having a small refractive index is used.

本発明は、１Ｗを超えるような高パワー光を一つの可変光減衰器で所要の光レベルに簡単に調節できるため、高パワー光伝送システムの受光レベル調整稼動が大幅に削減できる。また、光軸上で突合された端面には、屈折率整合剤が、充填されているため、その突合せ部分が融着と同じような接続状態、即ち、光ファイバ長手方向に一様な屈折率分布をもつことから、長手方向の屈折率分布の不連続性が一要因となっているファイバフューズを防ぐことができるため、信頼性と安全性のある高パワー通信線路を構築することができる。   According to the present invention, high power light exceeding 1 W can be easily adjusted to a required light level with a single variable optical attenuator, so that the light reception level adjustment operation of the high power optical transmission system can be greatly reduced. In addition, since the end face butt on the optical axis is filled with a refractive index matching agent, the butt portion is in the same connection state as fusion, that is, a uniform refractive index in the longitudinal direction of the optical fiber. Since it has a distribution, it is possible to prevent a fiber fuse caused by a discontinuity in the refractive index distribution in the longitudinal direction, so that a high power communication line with reliability and safety can be constructed.

以下図面を参照して本発明の実施の形態を詳細に説明する。
図１は本発明の実施形態に係る可変光減衰器を示す構成説明図である。図１において、２１は光ファイバ、２２は１Ｗを超えるような高パワー光、２３は収納ケース、２４はオイル状（ゲル状にならない程度の液体状）の屈折率整合剤、２５は移動方向、２６はＶ溝台、２７はＶ溝台ガイド、２８は光ファイバ移動手段としての長手方向アクチュエータである。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration explanatory view showing a variable optical attenuator according to an embodiment of the present invention. In FIG. 1, 21 is an optical fiber, 22 is a high power light exceeding 1 W, 23 is a storage case, 24 is an oil-like (a liquid that does not become a gel) refractive index matching agent, 25 is a moving direction, Reference numeral 26 denotes a V groove base, 27 denotes a V groove base guide, and 28 denotes a longitudinal actuator as an optical fiber moving means.

図１に示すように、２本の光ファイバ２１のそれぞれ先端部にはＶ溝台２６が一体化して設けられ、前記Ｖ溝台２６はＶ溝台ガイド２７上に移動自在に取付られる。前記２本の光ファイバ２１のそれぞれ先端部及びＶ溝台ガイド２７、Ｖ溝台２６の一部は収納ケース２３内に収容され、前記収納ケース２３内には液体状の屈折率整合剤２４が充填される。前記Ｖ溝台２６には長手方向アクチュエータ２８が設けられ、前記長手方向アクチュエータ２８はＶ溝台２６及び光ファイバ２１を移動方向２５に応じてＶ溝台ガイド２７上を自在に移動し、光ファイバ２１の光軸上で２本の光ファイバ２１のそれぞれ先端面を突合せたり、あるいは２本の光ファイバ２１のそれぞれ先端面間を０〜１０Ｗ０の範囲で変化させることができる。 As shown in FIG. 1, a V-groove base 26 is integrally provided at the tip of each of the two optical fibers 21, and the V-groove base 26 is movably mounted on a V-groove guide 27. The tip ends of the two optical fibers 21 and a part of the V-groove guide 27 and a part of the V-groove base 26 are accommodated in a storage case 23, and a liquid refractive index matching agent 24 is stored in the storage case 23. Filled. The V-groove base 26 is provided with a longitudinal actuator 28, and the longitudinal actuator 28 freely moves the V-groove base 26 and the optical fiber 21 on the V-groove guide 27 according to the moving direction 25. The tip surfaces of the two optical fibers 21 can be abutted on the optical axis 21, or the distance between the tip surfaces of the two optical fibers 21 can be changed in the range of 0 to 10 W 0 .

前記屈折率整合剤２４はシリカケトン等のシリコーン樹脂の側鎖の一部をフェニル基とメチル基で置き換えた化合物を用いることが有効であり、その中でもフェニル基とメチル基の配合比を４８：５２（側鎖基の％）とすることで特に好適な化合物が得られる。なお、前記屈折率整合剤２４は高パワー光の通光下で光ファイバのコアの屈折率と略同一となる屈折率を有し、かつ低損失で光を透過する液体状の屈折率整合剤である。   As the refractive index matching agent 24, it is effective to use a compound in which a part of the side chain of a silicone resin such as silica ketone is replaced with a phenyl group and a methyl group. Among them, the compounding ratio of the phenyl group and the methyl group is 48:52. A particularly suitable compound can be obtained by setting (% of side chain group). The refractive index matching agent 24 has a refractive index that is substantially the same as the refractive index of the core of the optical fiber under the passage of high power light, and is a liquid refractive index matching agent that transmits light with low loss. It is.

なお、屈折率整合剤２４は温度増加（加熱）に応じて屈折率が小さくなる（屈折率整合剤の種別によって異なるが、例えば、５０℃の変化で約２％小さくなる）特性がある。従って、高パワー光の通光時（加熱時）に屈折率整合剤２４の屈折率が光ファイバ２１のコアの屈折率と同程度となるためには、高パワー光の通光前（常温時）に光ファイバ２１のコアの屈折率よりやや高めの屈折率を有する屈折率整合剤２４を用いることが望ましい。具体的には、屈折率整合剤２４の通光前（常温時）の屈折率を１．４８〜１．５０程度とすればよい。   The refractive index matching agent 24 has a characteristic that the refractive index becomes smaller as the temperature increases (heats) (for example, the refractive index matching agent 24 becomes smaller by about 2% at 50 ° C., depending on the type of the refractive index matching agent). Therefore, in order for the refractive index of the refractive index matching agent 24 to be approximately the same as the refractive index of the core of the optical fiber 21 when high-power light is transmitted (during heating), before the high-power light is transmitted (at room temperature). It is desirable to use a refractive index matching agent 24 having a refractive index slightly higher than the refractive index of the core of the optical fiber 21. Specifically, the refractive index of the refractive index matching agent 24 before passing light (at room temperature) may be about 1.48 to 1.50.

図２は本発明の実施形態に係る可変光減衰器の高パワー光通過時の屈折率整合剤における屈折率プロファイルを示す説明図であり、図３は本発明の実施形態に係る可変光減衰器の高パワー光通過時の強度分布の変化を示す説明図である。図２及び図３において、２４は屈折率整合剤、３１はクラッド、３２はコア、３３は光ファイバの屈折率分布、３４は屈折率整合剤の屈折率プロファイル、３５は発熱部分、３６は屈折率整合剤通過前の光パワー強度分布、３７は屈折率整合剤通過後の光パワー強度分布である。   FIG. 2 is an explanatory view showing a refractive index profile in a refractive index matching agent when high-power light passes through the variable optical attenuator according to the embodiment of the present invention, and FIG. 3 is a variable optical attenuator according to the embodiment of the present invention. It is explanatory drawing which shows the change of the intensity distribution at the time of high power light passage. 2 and 3, 24 is a refractive index matching agent, 31 is a cladding, 32 is a core, 33 is a refractive index profile of the optical fiber, 34 is a refractive index profile of the refractive index matching agent, 35 is a heat generating portion, and 36 is refractive. An optical power intensity distribution before passing through the refractive index matching agent, and 37 is an optical power intensity distribution after passing through the refractive index matching agent.

図２及び図３を用いて本発明の実施形態に係る可変光減衰器を高パワー光が通過する際の振る舞いを説明する。すなわち、本発明の実施形態に係る可変光減衰器はＶ溝突合せの光減衰器であり、フィジカルコンタクトはさせず、光ファイバ端面間には屈折率整合剤２４が充填されている。通過光は、一方のファイバコア３２から出力され、屈折率整合剤２４を通過した後、もう一方のファイバコア３２へ入力される。このとき１Ｗクラスの高パワー光の通過光によって屈折率整合剤２４が加熱され、結果としてコア３２付近の屈折率整合剤２４に不均一な屈折率プロファイル３４が生じることになる（図２参照）。即ち、高パワー光通過時の温度に応じて光ファイバコア３２付近の屈折率整合剤２４の屈折率がやや小さくなり、クラッド３１以遠との間に図２に示すような屈折率プロファイル３４をもつようになる。図２に示すようなコア３２中心から光ファイバ外径方向に屈折率が大きくなるような媒体をシングルモード（ガウスビームの基本モード）の光が伝播すると、一様な屈折率プロファイルの整合剤中を通過する光より、スポットサイズが広がる（図３参照）。この広がりによって入力される側の光ファイバコア３２において、一様な屈折率プロファイルの場合よりも大きな損失が生じることになる。この損失発生メカニズムを利用しながら光ファイバ端面間隔を変化させて所要の光レベルに調節する。
次に、２本の光ファイバの端面間隔が、当該光ファイバのコア径（スポットサイズＷ０）に対して０〜１０Ｗ０の範囲で可動することの作用を説明する。上述のように、高パワー光通過時の温度上昇に応じて光ファイバのコア付近の屈折率整合剤の屈折率が小さくなり、光ファイバ端面間に図２に示すような屈折率プロファイルをもつようになる。図２に示すように、光ファイバのコア中心から光ファイバ外径方向に屈折率が大きくなるような媒体中をシングルモード（ガウスビームの基本モード）の光が伝播すると屈折率の大きい方に向かって進行していく光の性質のため、一様な屈折率分布をもつ整合剤中を通過する光より、スポットサイズが広がる。この広がりに対して、入力端側の光ファイバで受光ロスが生じる。ここで、スポットサイズの広がりが通光長（光ファイバの接続端面間隔）に依存することから光ファイバの接続端面間隔を変化させて所要の光レベルが得られることになる。 The behavior when high power light passes through the variable optical attenuator according to the embodiment of the present invention will be described with reference to FIGS. That is, the variable optical attenuator according to the embodiment of the present invention is a V-groove butt optical attenuator, which is not subjected to physical contact, and the refractive index matching agent 24 is filled between the optical fiber end faces. The passing light is output from one fiber core 32, passes through the refractive index matching agent 24, and then input to the other fiber core 32. At this time, the refractive index matching agent 24 is heated by the passing light of the 1 W class high power light, and as a result, a non-uniform refractive index profile 34 is generated in the refractive index matching agent 24 in the vicinity of the core 32 (see FIG. 2). . That is, the refractive index of the refractive index matching agent 24 in the vicinity of the optical fiber core 32 becomes slightly smaller depending on the temperature when passing high power light, and has a refractive index profile 34 as shown in FIG. It becomes like this. When light in a single mode (Gaussian beam fundamental mode) propagates through a medium whose refractive index increases from the center of the core 32 to the outer diameter of the optical fiber as shown in FIG. The spot size is wider than the light passing through (see FIG. 3). In the optical fiber core 32 on the input side due to this spread, a larger loss occurs than in the case of a uniform refractive index profile. Using this loss generation mechanism, the optical fiber end face spacing is changed to adjust to the required light level.
Then, the end face spacing of two optical fibers, the operation of the movable range of 0～10W 0 to the core diameter of the optical fiber (spot size W 0). As described above, the refractive index of the refractive index matching agent near the core of the optical fiber decreases as the temperature rises when high-power light passes, and the refractive index profile as shown in FIG. become. As shown in FIG. 2, when single mode (Gaussian beam fundamental mode) light propagates through a medium whose refractive index increases from the core center of the optical fiber in the direction of the outer diameter of the optical fiber, the light is directed toward the higher refractive index. Because of the nature of the light that travels, the spot size is wider than the light passing through the matching agent having a uniform refractive index distribution. For this spread, a light receiving loss occurs in the optical fiber on the input end side. Here, since the spread of the spot size depends on the light transmission length (the distance between the connecting end faces of the optical fiber), the required light level can be obtained by changing the distance between the connecting end faces of the optical fiber.

図４は本発明の実施形態に係る可変光減衰器の光ファイバ端面間隔と入力パワーとの関係（測定結果）を示す特性図である。すなわち、本発明の実施形態に係る可変光減衰器の有効性を検証するため、通過する光パワーと接続損失との関係を光ファイバ接続端面間隔について調べたものである。図４より、通過する光パワーと接続損失との関係には光ファイバ接続端面間隔と相関があり、例えば、光ファイバ接続端面間隔が５０μｍ間隔の可変光減衰器を用いれば光パワーが２５ｄＢｍ（約３００ｍＷ）を超えるあたりから接続損失が増加していることから、光パワーが２５ｄＢｍを超える光伝送では、接続端面間隔を５０μｍ以上に調節することで、所望の損失が得られることが分かる。また、光伝送パワーに応じて光ファイバ接続端面間隔を調節し可変光減衰器とできることは言うまでもない。   FIG. 4 is a characteristic diagram showing the relationship (measurement result) between the optical fiber end face spacing and the input power of the variable optical attenuator according to the embodiment of the present invention. That is, in order to verify the effectiveness of the variable optical attenuator according to the embodiment of the present invention, the relationship between the optical power passing through and the connection loss is examined with respect to the distance between the optical fiber connection end faces. From FIG. 4, the relationship between the optical power passing through and the connection loss correlates with the distance between the optical fiber connection end faces. For example, if a variable optical attenuator with an optical fiber connection end face distance of 50 μm is used, the optical power is 25 dBm (about Since the connection loss increases from around 300 mW), it can be seen that the desired loss can be obtained by adjusting the distance between the connection end faces to 50 μm or more in optical transmission with optical power exceeding 25 dBm. Needless to say, a variable optical attenuator can be obtained by adjusting the distance between the optical fiber connection end faces according to the optical transmission power.

以上のことから、高パワー光通過時の温度上昇に応じて光ファイバコア付近の屈折率整合剤の屈折率が連続分布をもつように小さくなり、かつ、接続端面間において、一様でない（勾配をもつ）屈折率プロファイルが生じるという特性を利用しながら通過光の強度プロファイルを広げ、この広がりが通光長に依存することから端面間隔を変化させて所要の光レベルを得る方法の有効性が確認できた。なお、接続損失は高パワー光の入力とほぼ同時（１秒以内）に発生し、通光している間はその接続損失を安定に保つこと、また、その接続損失の値には十分な再現性があること、さらには、接続損失発生に伴う屈折率整合剤２４の物性的な変化等も生じないことを確認した。   From the above, the refractive index of the refractive index matching agent in the vicinity of the optical fiber core becomes small so as to have a continuous distribution according to the temperature rise at the time of passing high power light, and is not uniform between the connection end faces (gradient It is effective to obtain a desired light level by changing the end face spacing because the spread light intensity profile is widened while utilizing the characteristic that a refractive index profile is generated. It could be confirmed. Note that the connection loss occurs almost simultaneously with the input of high-power light (within 1 second), keep the connection loss stable while light is passing, and reproduce the connection loss sufficiently. Further, it was confirmed that there is no change in physical properties of the refractive index matching agent 24 due to the occurrence of connection loss.

以上のように本発明の実施形態に係る可変光減衰器は、２本の光ファイバの端面を光軸上で突合せ、かつ、当該端面を含む前記２本の光ファイバ全体が液体状の屈折率整合剤で充填された構造であって、前記屈折率整合剤は室温で前記２本の光ファイバのコアと同程度かやや高めの屈折率（具体的には１．４８〜１．５０程度）を有するものである。これによって、前記２本の光ファイバの突合せ部分では、高パワー光の通光下で温度上昇した屈折率整合剤の屈折率が、光ファイバコアの屈折率とほぼ同じ状態で、かつ、連続して分布することから、融着と同じような接続状態を作り上げることができ、屈折率分布の不連続性が一要因となっているファイバフューズを防ぐことができる（例えば、非特許文献１参照。）。加えて、接続端面の領域では、局所的に不均一な（勾配をもつ）屈折率プロファイルを形成することから、均一な屈折率プロファイルの場合以上にスポットサイズが広がり、接続端面間隔に応じて所望の光レベルに調整することができる。   As described above, in the variable optical attenuator according to the embodiment of the present invention, the end faces of the two optical fibers are abutted on the optical axis, and the entire two optical fibers including the end faces are in a liquid refractive index. A structure filled with a matching agent, wherein the refractive index matching agent has a refractive index that is the same as or slightly higher than the cores of the two optical fibers at room temperature (specifically, about 1.48 to 1.50). It is what has. As a result, at the butt portion of the two optical fibers, the refractive index of the refractive index matching agent whose temperature has increased under the passage of high-power light is substantially the same as the refractive index of the optical fiber core and is continuous. Therefore, it is possible to create a connection state similar to fusion, and to prevent a fiber fuse caused by discontinuity in the refractive index distribution (see, for example, Non-Patent Document 1). ). In addition, in the region of the connection end face, a locally non-uniform (gradient) refractive index profile is formed, so that the spot size is widened more than in the case of a uniform refractive index profile, and is desired according to the connection end face interval. The light level can be adjusted.

なお、本発明は、上記実施形態そのままに限定されるものではなく、実施段階ではその要旨を逸脱しない範囲で構成要素を変形して具体化できる。また、上記実施形態に開示されている複数の構成要素の適宜な組み合せにより種々の発明を形成できる。例えば、実施形態に示される全構成要素から幾つかの構成要素を削除してもよい。更に、異なる実施形態に亘る構成要素を適宜組み合せてもよい。   Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

本発明の実施形態に係る可変光減衰器を示す構成説明図である。It is a block diagram showing a variable optical attenuator according to an embodiment of the present invention. 本発明の実施形態に係る可変光減衰器の高パワー光通過時の屈折率整合剤における屈折率プロファイルを示す説明図である。It is explanatory drawing which shows the refractive index profile in the refractive index matching agent at the time of high power light passage of the variable optical attenuator which concerns on embodiment of this invention. 本発明の実施形態に係る可変光減衰器の高パワー光通過時の強度分布の変化を示す説明図である。It is explanatory drawing which shows the change of the intensity distribution at the time of high power light passage of the variable optical attenuator which concerns on embodiment of this invention. 本発明の実施形態に係る可変光減衰器の光ファイバ端面間隔と入力パワーとの関係（測定結果）を示す特性図である。It is a characteristic view which shows the relationship (measurement result) of the optical fiber end surface space | interval and input power of the variable optical attenuator which concerns on embodiment of this invention. 従来の光減衰ファイバを用いた光減衰器を示す構成説明図である。It is structure explanatory drawing which shows the optical attenuator using the conventional optical attenuation fiber. 従来の光カプラを用いた光減衰器を示す構成説明図である。It is structure explanatory drawing which shows the optical attenuator using the conventional optical coupler.

符号の説明Explanation of symbols

２１…光ファイバ、２２…１Ｗを超えるような高パワー光、２３…収納ケース、２４…オイル状（ゲル状にならない程度の液体状）の屈折率整合剤、２５…移動方向、２６…Ｖ溝台、２７…Ｖ溝台ガイド、２８…光ファイバ移動手段としての長手方向アクチュエータ。   DESCRIPTION OF SYMBOLS 21 ... Optical fiber, 22 ... High power light exceeding 1 W, 23 ... Storage case, 24 ... Refractive index matching agent of oil-like (a liquid form which does not become gel form), 25 ... Moving direction, 26 ... V groove 27: V groove base guide, 28: Longitudinal actuator as optical fiber moving means.

Claims (3)

光ファイバで伝送される高パワー光を光の状態で減衰させる可変光減衰器であって、
光軸上で端面が突合わされた２本の光ファイバと、
前記２本の光ファイバのそれぞれ先端部に一体化して設けられたＶ溝台と、
前記Ｖ溝台及び前記光ファイバが移動自在に取付られるＶ溝台ガイドと、
前記２本の光ファイバのそれぞれ先端部及び前記Ｖ溝台ガイド、前記Ｖ溝台の一部が収容される収容ケースと、
前記収容ケース内に充填されると共に前記光ファイバ端面間に充填され、高パワー光の通光下で前記光ファイバのコアの屈折率と略同一の屈折率となる液体状の屈折率整合剤と、
前記Ｖ溝台及び前記光ファイバを前記Ｖ溝台ガイド上に自在に移動させ、前記２本の光ファイバの端面間隔を光軸上で変化させる光ファイバ移動手段と
を具備することを特徴とする可変光減衰器。 A variable optical attenuator that attenuates high power light transmitted through an optical fiber in the state of light,
Two optical fibers whose end faces are abutted on the optical axis;
A V-groove base integrally provided at the tip of each of the two optical fibers;
A V-groove guide on which the V-groove and the optical fiber are movably mounted;
Each of the two optical fibers, a distal end portion, the V-groove guide, a housing case for housing a part of the V-groove,
Filled between the optical fiber end face while being filled in the accommodating case, and a high power optical refractive index of the core of the optical fiber under light passing substantially the same refractive index liquid index matching medium ,
And an optical fiber moving means for freely moving the V-groove base and the optical fiber onto the V-groove base guide and changing an end face interval between the two optical fibers on the optical axis. Variable optical attenuator. 前記光ファイバ移動手段として、前記２本の光ファイバの端面間隔を、当該光ファイバのコア径（スポットサイズＷ０）に対して０〜１０Ｗ０の範囲で可動する長手方向アクチュエータを用いる
ことを特徴とする請求項１に記載の可変光減衰器。 As the optical fiber moving means, characterized in that a longitudinal actuator for moving the end face spacing of the two optical fibers, the core diameter of the optical fiber (spot size W 0) in a range of 0～10W 0 The variable optical attenuator according to claim 1. 前記屈折率整合剤として、高パワー光の通光前に前記光ファイバのコアの屈折率よりやや高めの屈折率を有し、高パワー光の通光下で屈折率が小さくなる屈折率整合剤を用いる
ことを特徴とする請求項１又は２に記載の可変光減衰器。 As the refractive index matching agent, has a slightly refractive index higher than the refractive index of the core of the optical fiber to the light passing before the high power light, a refractive index matching agent whose refractive index decreases in passing light of a high power light The variable optical attenuator according to claim 1 or 2, wherein:
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CN104678503A (en) * 2015-03-11 2015-06-03 哈尔滨工程大学 Optical fiber optical switch based on photothermal effect

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JPS4944418A (en) * 1972-07-25 1974-04-26
JPH11281803A (en) * 1998-03-26 1999-10-15 Sumitomo Osaka Cement Co Ltd Method for limiting optical intensity and limiter
JP2004101470A (en) * 2002-09-12 2004-04-02 Nippon Sheet Glass Co Ltd Microchemical system, light source unit for microchemical system and photothermal conversion spectrometric method
JP2004325839A (en) * 2003-04-25 2004-11-18 Nippon Telegr & Teleph Corp <Ntt> Variable optical attenuator

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Publication number Priority date Publication date Assignee Title
JPS4944418A (en) * 1972-07-25 1974-04-26
JPH11281803A (en) * 1998-03-26 1999-10-15 Sumitomo Osaka Cement Co Ltd Method for limiting optical intensity and limiter
JP2004101470A (en) * 2002-09-12 2004-04-02 Nippon Sheet Glass Co Ltd Microchemical system, light source unit for microchemical system and photothermal conversion spectrometric method
JP2004325839A (en) * 2003-04-25 2004-11-18 Nippon Telegr & Teleph Corp <Ntt> Variable optical attenuator

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104678503A (en) * 2015-03-11 2015-06-03 哈尔滨工程大学 Optical fiber optical switch based on photothermal effect

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