JPS62103607A - Method for evaluating splicing loss of multimode optical fiber - Google Patents

Abstract

PURPOSE:To easily evaluate the loss due to the core distortion in a splicing part without a special device by obtaining a ratio of the outside diameter of an optical fiber before splicing to that after splicing and evaluating the splicing loss due to the core distortion in accordance with this ratio. CONSTITUTION:Optical fibers 10 are put in V-grooves 20 arranged linearly accurately and are fixed there, and an interval 9d) between end faces is determined, and they are preheated, and one optical fiber 10 is advanced by d+l=L (l is the overlap length and L is the extent of press-in) while heating them. Relations between a ratio epsilon of an original outside diameter d1 of the optical fiber at a splicing point to an outside diameter d2 of that after fusion-splicing and a splicing loss alpha are always fixed for the same optical fiber on the same splicing conditions. Thus, the ratio epsilon is measured to obtain the splicing loss alphadue to core distortion.

Description

【発明の詳細な説明】 ［産業上の利用分野］ この発明は、多モード光ファイバの融着接続後における
損失評価方法に関するもので、特に光ファイバに光を通
すことなく、接続点における測定だけで損失を評価する
方法に関するものである。[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for evaluating loss after fusion splicing of multimode optical fibers. It concerns how to evaluate losses.

［従来の技術と問題点］ 上記の損失評価方法として、ミラー、顕微鏡。[Conventional technology and problems] Mirrors and microscopes are used as loss evaluation methods for the above.

ＴＶカメラなどを使用して、接続部のＸ方向、ｙ方向の
軸ずれを測定し、それから損失を評価する方法が公知で
ある。A method is known in which a TV camera or the like is used to measure the axis deviation of the connection part in the X direction and the y direction, and then the loss is evaluated.

しかし、この方法によって得られる接続損失値は、光フ
ァイバに光しを通して得られる実測値と比較すると小さ
い値であり、実際には軸ズレによる損失ともう一つの損
失要因であるコア歪による損失を加算して全体の接続損
失とする必要があった。However, the splice loss value obtained by this method is a small value compared to the actual value obtained by passing light through the optical fiber, and in reality, the loss due to axis misalignment and the loss due to core distortion, which is another loss factor, are small. It was necessary to add it up to get the total connection loss.

しかして現実には、このコア歪による接続損失を評価す
る方法が見当らず、軸ズレによる損失を評価することで
光ファイバの接続損失のおおよその目安としてすると−
いうのが実状であった。However, in reality, there is no way to evaluate the splice loss due to core distortion, so evaluating the loss due to axis misalignment can be used as a rough guide to the splice loss of an optical fiber.
That was the reality.

［問題点を解決するための手段］ この発明は、接続部のコア歪による損失を評価する方法
を提供するもので、融着接続機の接続後の接続点の外径
ｄ２に対する元の光ファイバ外径ｄ、の比εを求め、そ
の値から、コア歪による接続損失を評価するようにした
ものである。[Means for Solving the Problems] The present invention provides a method for evaluating loss due to core distortion of a splicing part, and the present invention provides a method for evaluating loss due to core distortion of a splicing part, and the present invention provides a method for evaluating loss due to core distortion of a splicing part. The ratio ε of the outer diameter d is determined, and the connection loss due to core strain is evaluated from that value.

［その説明］ 一般に、多モード光ファイバを接続する場合は、第２図
のように、光ファイバ１０を、正確に直線上に整列して
いるＶ溝２０内に入れて固定し、 ■端面間隔ｄを決め。[Explanation] Generally, when connecting multimode optical fibers, as shown in Fig. 2, the optical fibers 10 are placed and fixed in V-grooves 20 that are accurately aligned on a straight line, and the distance between the end faces is adjusted. Decide on d.

■手前熱し、 ■加熱しながら一方の光ファイバｌＯを、ｄ中文＝Ｌ だけ前進させる。■Heat the front, ■ While heating one optical fiber lO, d Chinese = L only move forward.

ただし、文はオーバーラツプ長、 Ｌは押込み量である。However, the sentence has an overlap length, L is the pushing amount.

ところで、上記の接続部におけるコア歪をもたらす要因
には、 ■押込み量りの不適。By the way, the factors that cause the core distortion in the above-mentioned connections include: ① Inadequate push-in measurement.

■端面間隔ｄの不適。■Inappropriate end face spacing d.

■手前熱時間の不適、 などが考えられる。■ Inappropriate heating time in front, etc. are possible.

これらのうち、■■によるコア歪は、ＧＩ型光ファイバ
の場合、第３図のように、接続点１２の膨らみ（同図（
ａ））や、凹み（同図（ｂ））となって表れる。なお同
図（Ｃ）は最適の場合である。Among these, the core strain caused by
a)) or a dent ((b) in the same figure). Note that (C) in the same figure is an optimal case.

なお、上記■の場合で、手前熱時間が長ずざるときは、
コアが広がるが、その歪による損失は、０．０３ｄＢ程
度であり、接続損失の目標とする０、１ｄＢに比べると
非常に小さいので除外してもさしつかえない。In addition, in the case of ■ above, if the front heating time is not long,
Although the core expands, the loss due to distortion is about 0.03 dB, which is very small compared to the target connection loss of 0.1 dB, so it can be excluded.

コア径／外径＝５０ｇｍ　７１２５　ｇｍのＧＩ型光フ
ァイバを、波長１．３ｐｍのＬＥＤ光源を用いて、第２
図のように、■溝２０内に固定し、無調心で、端面間隔
ｄを変え、一定の押込み量Ｌ　＝　２００ル鵬で融着接
続したときにおける、εと接続損失αとの関係を、第１
図に示す０曲線は最小２乗法による近似曲線である。　
このεと接続損失αとの関係は、同一の光ファイバにつ
いて、同一の接続条件で接続したとき、いつも一定であ
ることがわかった。Core diameter/outer diameter = 50 gm A 7125 gm GI type optical fiber was
As shown in the figure, the relationship between ε and splicing loss α when fixed in the groove 20, non-aligned, changing the end face spacing d, and fusion splicing with a constant push-in amount L = 200 l. , 1st
The zero curve shown in the figure is an approximated curve based on the least squares method.
It has been found that the relationship between ε and splice loss α is always constant when the same optical fiber is spliced under the same splicing conditions.

したがって、εを測定することによって、コア歪による
接続損失αが求められる。Therefore, by measuring ε, the splice loss α due to core strain can be determined.

第１図の、ｅ＞１については。Regarding e>1 in Fig. 1.

α＝　　２．０４（ε−１）２　＋ｏ、ｏｅ（ε−１）
　＋０．０５　［ｄＢ］の式で表わされることがわかる
。α= 2.04(ε-1)2 +o, oe(ε-1)
It can be seen that it is expressed by the formula +0.05 [dB].

定数項の０．０５ｄＢは、外径歪以外に要因による接続
損失で、さくｌについては、外径歪以外の要因が支配的
になる。The constant term of 0.05 dB is a connection loss due to factors other than the outer diameter distortion, and with regard to the diameter, factors other than the outer diameter distortion are dominant.

なお、寸法や屈折率などの違う光ファイバについては、
あらためて、上記のように、εとαとの関係を求めてお
く必要がある。Regarding optical fibers with different dimensions and refractive index,
As mentioned above, it is necessary to find the relationship between ε and α.

［発明の効果１ （１）接続点の外径を測定するだけあるから、特別な装
置がなくても、容易に実施できる。[Advantageous Effects of the Invention 1 (1) Since all that is required is to measure the outer diameter of the connection point, it can be easily carried out without any special equipment.

（２）多心テープ型光ファイバの場合でも、特別な装置
を付加〔ないで、そのまま実施てきる。(2) Even in the case of multi-core tape type optical fiber, it can be implemented as is without adding any special equipment.

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

第１図は本発明における接続点の外径歪εと接続損失α
との関係を示す特性図、 第２図は融着接続の一般的説明図、 第３図（ａ）（ｂ）（ｃ）は接続点の状態の説明図。 ｌＯ：光ファイバ　　１２：接続点 ２０：Ｖ溝Figure 1 shows the outer diameter strain ε and connection loss α at the connection point in the present invention.
FIG. 2 is a general explanatory diagram of fusion splicing, and FIG. 3 (a), (b), and (c) are explanatory diagrams of the state of connection points. lO: Optical fiber 12: Connection point 20: V groove

Claims (1)

【特許請求の範囲】 一定の接続条件のもとにおける、融着接続後の接続点の
外径ｄ＿２に対する元の光ファイバ外径ｄ＿１の比εと
接続損失αとの関係を、特定の光ファイバについて、あ
らかじめ求めておき、 前記光ファイバについて、前記条件で融着接続した後の
前記εの値を求め、それにより接続損失αの値を推定す
ることを特徴とする、多モード光ファイバの接続損失評
価方法。[Claims] The relationship between the ratio ε of the original optical fiber outer diameter d_1 to the outer diameter d_2 of the splicing point after fusion splicing and the splice loss α under certain splicing conditions can be expressed as follows: is determined in advance, and the value of ε is determined for the optical fiber after fusion splicing under the conditions, and the value of the splice loss α is estimated thereby. Loss evaluation method.