JPH065332B2 - Optical coupler - Google Patents
Optical couplerInfo
- Publication number
- JPH065332B2 JPH065332B2 JP61140638A JP14063886A JPH065332B2 JP H065332 B2 JPH065332 B2 JP H065332B2 JP 61140638 A JP61140638 A JP 61140638A JP 14063886 A JP14063886 A JP 14063886A JP H065332 B2 JPH065332 B2 JP H065332B2
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- Prior art keywords
- lens
- optical
- refractive index
- axis
- optical coupler
- Prior art date
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- Expired - Lifetime
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- Optical Couplings Of Light Guides (AREA)
- Semiconductor Lasers (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は発光ダイオード、半導体レーザ等の発光素子か
らの光を光伝送ファイバに効率良く入射させるための光
結合器に関する。Description: TECHNICAL FIELD The present invention relates to an optical coupler for efficiently causing light from a light emitting element such as a light emitting diode or a semiconductor laser to enter an optical transmission fiber.
上記のような光源からの拡散光束を光結合器を介して光
伝送ファイバのコア内に効率良く伝送するためには、軸
上入射光ばかりでなく、組立て誤差に起因する軸外入射
光も効率良く光伝送ファイバに伝送する必要がある。こ
のために光結合器に使用されるレンズは収差について厳
しい性能が要求される。In order to efficiently transmit the diffused light flux from the above light source into the core of the optical transmission fiber through the optical coupler, not only the on-axis incident light but also the off-axis incident light caused by the assembly error is efficient. It needs to be well transmitted to the optical transmission fiber. For this reason, the lens used in the optical coupler is required to have severe performance with respect to aberrations.
従来、光結合器として第５図に示した光学系が使用され
ている。Conventionally, the optical system shown in FIG. 5 is used as an optical coupler.
第５図において、１０は屈折率分布型の単一レンズ、１
１は光源、１２は光伝送ファイバであり、レンズ１０は
屈折率が中心軸上で最大で外周に向けて漸減する分布を
有し、光源１１に対向する端面が凸曲面で、光ファイバ
１２に対向する端面が光軸に垂直な平面である。光源１
１から出た拡散光束はレンズ１０で集束されて光ファイ
バ１２のコア内に入射する。In FIG. 5, 10 is a single lens of the gradient index type, 1
Reference numeral 1 is a light source, 12 is an optical transmission fiber, the lens 10 has a distribution in which the refractive index is maximum on the central axis and gradually decreases toward the outer circumference, and the end face facing the light source 11 is a convex curved surface, Opposing end faces are planes perpendicular to the optical axis. Light source 1
The diffused light flux emitted from 1 is focused by the lens 10 and enters the core of the optical fiber 12.
しかしながら上記のような光学系では、光結合器を組み
立てる時に一番問題となる光伝送ファイバの光軸に垂直
な方向の組立誤差等に起因する軸ずれに対して充分な性
能が得られない。However, the optical system as described above cannot obtain sufficient performance against the axis deviation caused by the assembly error in the direction perpendicular to the optical axis of the optical transmission fiber, which is the most problematic when assembling the optical coupler.
例えば、第５図に示した従来の光学系では上記軸ずれを
約１μm以下に抑える必要があるが、実際に１μm以下に
軸ずれ誤差を抑えることは組立工程が複雑になり歩留り
の低下を招くなど実生産上の問題が多い。For example, in the conventional optical system shown in FIG. 5, it is necessary to suppress the axis deviation to about 1 μm or less, but actually suppressing the axis deviation error to 1 μm or less complicates the assembly process and causes a reduction in yield. There are many problems in actual production.
上記従来の問題を解決する本発明による光結合器は２群
２枚のレンズ構成とし、両レンズ媒質は光軸から半径方
向へｒの距離における屈折率ｎ（ｒ）が、ｎ0を中心軸
上屈折率、ｇ、ｈ4、ｈ6、ｈ8を分布定数として、 ｎ2（ｒ）＝ｎ2 0〔1-(gr)2+h4(gr)4+h6(gr)6+h8(gr)8+
…〕 で表わされる半径方向屈折率分布を有し、第１レンズは
一方の面が凸面で他方の面が光軸に垂直な平面であり、
第２レンズは両面が光軸に垂直な平面であって光伝送フ
ァイバの端面と密着して配置される。An optical coupler according to the present invention for solving the above-mentioned conventional problem has a lens configuration of two groups and two lenses, and both lens media have a refractive index n (r) at a distance r in the radial direction from the optical axis with the central axis being n 0. N 2 (r) = n 2 0 [1- (gr) 2 + h 4 (gr) 4 + h 6 (gr) 6 + with the upper refractive index, g, h 4 , h 6 and h 8 as distribution constants h 8 (gr) 8 +
Has a radial-direction refractive index distribution represented by the following formula, one surface of the first lens is convex and the other surface is a plane perpendicular to the optical axis,
Both surfaces of the second lens are planes perpendicular to the optical axis and are arranged in close contact with the end surface of the optical transmission fiber.
さらに本発明は、前記第１レンズの焦点距離をｆ1、凸
面の曲率半径をＲ、中心軸上での厚みをｄ1としたと
き、 ０．４≦ｆ1・ｇ≦０．６ ０．８≦Ｒ／ｆ1≦１．３ ０．５≦ｄ1／ｆ1≦２．３ の範囲内に限定するものであり、これにより、特に良好
な収差が得られ、光軸に垂直方向の組立誤差の許容値も
充分に大きい。Further, in the present invention, when the focal length of the first lens is f 1 , the radius of curvature of the convex surface is R, and the thickness on the central axis is d 1 , 0.4 ≦ f 1 · g ≦ 0.6 0. 8 ≦ R / f 1 ≦ 1.3 0.5 ≦ d 1 / f 1 ≦ 2.3, whereby a particularly good aberration can be obtained, and The tolerance of assembly error is also large enough.
本発明による光結合器は、後述の数値実施例に示すよう
に球面収差とコマ収差が充分に小さく、光軸に垂直な方
向の組立誤差の許容値が大きい。The optical coupler according to the present invention has sufficiently small spherical aberration and coma aberration, and a large allowable value of the assembly error in the direction perpendicular to the optical axis, as shown in the numerical examples described later.
したがって本発明によれば光結合器の組立て製作工程を
簡略化できるとともに、安価な部品を使用できるので、
コストの低減を図ることができる。Therefore, according to the present invention, since the assembly process of the optical coupler can be simplified and inexpensive parts can be used,
The cost can be reduced.
以下本発明を第１図に示した実施例について詳細に説明
する。The present invention will be described in detail below with reference to the embodiment shown in FIG.
第１図において、１は光源例えば半導体レーザであり、
２は本発明に係る光結合器光学系、３は光伝送ファイバ
であって、光源１から出射した拡散光束４は光結合器２
で集束されて光伝送ファイバ３のコア内に入射する。In FIG. 1, 1 is a light source such as a semiconductor laser,
2 is an optical coupler optical system according to the present invention, 3 is an optical transmission fiber, and the diffused light flux 4 emitted from the light source 1 is an optical coupler 2
Then, the light is focused by and is incident on the core of the optical transmission fiber 3.
光結合器２は第１の屈折率分布型レンズ５と、この第１
レンズ５の端面から一定距離ｄ２をおいて配置される第
２の屈折率分布型レンズ６の２群２枚構成となってい
る。両レンズ５，６を構成する媒質はいずれも、光軸７
から半径方向へｒの距離における屈折率ｎ(r)が、 ｎ2（ｒ）＝ｎ2 0〔1-(gr)2+h4(gr)4+h6(gr)6+h8(gr)8＋
……〕 のべき級数で表わされる屈折率勾配を有する透明円柱体
である。The optical coupler 2 includes a first gradient index lens 5 and a first gradient index lens 5.
It has a two-group, two-element configuration of the second gradient index lens 6 arranged at a constant distance d 2 from the end surface of the lens 5. Each of the media forming both lenses 5 and 6 has an optical axis 7
The refractive index n (r) at the distance r from the radial direction is n 2 (r) = n 2 0 [1- (gr) 2 + h 4 (gr) 4 + h 6 (gr) 6 + h 8 ( gr) 8 +
……] It is a transparent cylinder with a refractive index gradient represented by a power series of.
上式においてｎ０は光軸上の屈折率、g,h4,h6,h8は分布
定数を表わす。そして第１レンズ５は、光源１に対向す
る面５Ａが光軸７上に曲率中心を有する曲率半径r1の凸
球面で、他方の面5Bが曲率半径r2＝無限大つまり平面で
ある。In the above equation, n 0 represents the refractive index on the optical axis, and g, h 4 , h 6 and h 8 represent distribution constants. Then, in the first lens 5, the surface 5A facing the light source 1 is a convex spherical surface having a curvature radius r 1 having the center of curvature on the optical axis 7, and the other surface 5B is a curvature radius r 2 = infinity, that is, a flat surface.
また第２レンズ６は、第１レンズ５の端面からd2の距離
において配置され、その両面6Aおよび6Bは曲率半径r3,r
4がいずれも無限大で光軸７に垂直な平面であり、この
レンズ６の一方の端面6Bに光軸を一致させて光ファイバ
３の端面を密着して接続する。The second lens 6 is arranged at a distance of d 2 from the end surface of the first lens 5, and both surfaces 6A and 6B have radii of curvature r 3 , r
Reference numeral 4 denotes a plane which is infinite and perpendicular to the optical axis 7. The optical axis is aligned with one end surface 6B of the lens 6 and the end surface of the optical fiber 3 is closely contacted for connection.
そして第１レンズ５の焦点距離をf1、凸面5Aの曲率半径
の大きさをＲ、中心軸上の厚みをd1とすると光結合器２
が、 ０．４≦ｆ1・ｇ≦０．６ (1) ０．８≦Ｒ／ｆ1≦１．３ (2) ０．５≦ｄ1／ｆ1≦２．３ (3) の条件を満足しているときに特に良好な収差補正が可能
になる。When the focal length of the first lens 5 is f 1 , the radius of curvature of the convex surface 5A is R, and the thickness on the central axis is d 1 , the optical coupler 2
Where 0.4 ≦ f 1 · g ≦ 0.6 (1) 0.8 ≦ R / f 1 ≦ 1.3 (2) 0.5 ≦ d 1 / f 1 ≦ 2.3 (3) When the above condition is satisfied, particularly good aberration correction becomes possible.
条件(1)は第１レンズ５の屈折率分布定数に関するもの
であり、条件(1)の下限値以下では屈折率分布媒質のパ
ワーが小さくなり、パワーを一定に保とうとすると球面
（凸面）でパワーを得る必要があり、そうすると球面で
高次の収差が発生し、結合器光学系の収差を補正できな
くなってしまう。The condition (1) relates to the refractive index distribution constant of the first lens 5, and the power of the refractive index distribution medium becomes small below the lower limit value of the condition (1), and it is a spherical surface (convex surface) to keep the power constant. It is necessary to obtain power, and then higher-order aberrations occur on the spherical surface, making it impossible to correct the aberration of the coupler optical system.
また条件(1)の上限を越えるとレンズ媒質の中心と周辺
との屈折率差が大きくなり屈折率分布の制御が困難にな
る。If the upper limit of the condition (1) is exceeded, the refractive index difference between the center and the periphery of the lens medium becomes large, making it difficult to control the refractive index distribution.
条件(2)はレンズ５の曲率半径の大きさに関するもので
あり、条件(2)の下限値以下では球面で発生するパワー
が大きくなり高次収差が発生しやすくなる。条件(2)の
上限値を越えるとレンズ５の中心と周辺の屈折率差をか
なり大きくする必要があり屈折率分布の制御が困難にな
る。The condition (2) relates to the size of the radius of curvature of the lens 5, and below the lower limit of the condition (2), the power generated on the spherical surface becomes large and high-order aberrations easily occur. When the value exceeds the upper limit of the condition (2), it is necessary to considerably increase the difference in refractive index between the center and the periphery of the lens 5, which makes it difficult to control the refractive index distribution.
条件(3)は条件(1)，(2)から自動的に決まるものであ
る。Condition (3) is automatically determined from conditions (1) and (2).
第１図の実施例では光源１に第１レンズ５の凸面5Aを対
向させているが、第１レンズ５はその平面側が光源１に
対向し、凸面側が第２レンズ６に対向するように配置し
てもよい。In the embodiment of FIG. 1, the convex surface 5A of the first lens 5 is opposed to the light source 1, but the first lens 5 is arranged such that its flat surface side faces the light source 1 and the convex surface side faces the second lens 6. You may.
また本発明で使用する第１レンズ５の媒質は四次項分布
定数h4が−２ないし２の範囲内にあることが望ましく、
この範囲よりも外側では高次収差が出やすくなる。The medium of the first lens 5 used in the present invention preferably has a quartic distribution constant h 4 in the range of −2 to 2,
Higher-order aberrations tend to occur outside this range.
さらに第１レンズ５の凸面が第２レンズ６と対向するよ
うに配置した場合には、 0.5≦d1／f1≦1.3 の範囲にあることが望ましく、第１レンズ５の凸面が光
源側にあるときは 2.0≦d1／f1≦2.3 の範囲にあることが望ましい。Further, when the convex surface of the first lens 5 is arranged so as to face the second lens 6, it is desirable that the range is 0.5 ≦ d 1 / f 1 ≦ 1.3, and the convex surface of the first lens 5 is located on the light source side. In some cases, it is desirable to be in the range of 2.0 ≦ d 1 / f 1 ≦ 2.3.
以下に本発明の具体的数値例を示し、各実施例の収差曲
線を第２図ないし第４図に示す。収差曲線のたて軸は第
２レンズの出射側開口数NA′である。Specific numerical examples of the present invention are shown below, and the aberration curves of each example are shown in FIGS. 2 to 4. The vertical axis of the aberration curve is the exit side numerical aperture NA 'of the second lens.
実施例１ 第１レンズ：r1＝無限大、d1＝1.921、 n0＝1.607、ｇ＝0.325、 h4＝0.249、h6＝1.709、 h8＝14.489、r2＝−1.500、 1＝0.7、光源側開口数NA＝0.5 ｆ１・ｇ＝０．５１２８５ Ｒ／ｆ１＝０．９５０５７ ｄ１／ｆ１＝１．２１７３６４ 第２レンズ：r3＝無限大、d3＝3.480、 n0＝1.607、ｇ＝0.325、 h4＝2.0、h6＝0.0、h8＝０．０、 r4＝無限大 両レンズ間隔 d2＝１５．７４７ 実施例２ 第１レンズ：r1＝1.700、d1＝2.837、 n0＝1.658、ｇ＝0.392、 h4＝1.682、h6＝1.021、 h8＝9.508、r2＝無限大、 1＝0.7、ＮＡ＝0.5 ｆ１・ｇ＝０．５１９７９２ Ｒ／ｆ１＝１．２８２０５１ ｄ１／ｆ１＝２．１３９５１７ 第２レンズ：r3＝無限大、 d3＝3.480、n0＝1.607、 ｇ＝0.325、h4＝2.0、h6＝0.0、 h8＝0.0、r4＝無限大 d2＝１１．３８２ 実施例３ 第１レンズ：r1＝無限大、d1＝1.281、 n0＝1.658、ｇ＝0.392、 h4＝0.654、h6＝2.788、 h8＝24.710、r2＝-1.2、 1＝0.7、ＮＡ＝0.5 ｆ１・ｇ＝0.49392 Ｒ／ｆ１＝0.952381 ｄ１／ｆ１＝1.016667 第２レンズ：r3＝無限大、d3＝3.480、 n0＝1.607、ｇ＝0.325、 h4＝2.0、h6＝0.0、h8＝0.0、 r4＝無限大 d2＝１１．８３３ 〔発明の効果〕 本発明による光結合器は残留波面収差が極めて小さく、
光軸に垂直方向の軸ずれに対する許容値も大きいので、
結合効率の良い光結合器を簡単な工程で容易に作ること
ができる。Example 1 First lens: r 1 = infinity, d 1 = 1.921, n 0 = 1.607, g = 0.325, h 4 = 0.249, h 6 = 1.709, h 8 = 14.489, r 2 −1.500, 1 = 0.7, light source side numerical aperture NA = 0.5 f 1 · g = 0.51285 R / f 1 = 0.95057 d 1 / f 1 = 1.217364 Second lens: r 3 = infinity, d 3 = 3.480, n 0 = 1.607, g = 0.325, h 4 = 2.0, h 6 = 0.0, h 8 = 0.0, r 4 = infinity both lens distance d 2 = 15.747 example 2 the first lens: r 1 = 1.700 , D 1 = 2.837, n 0 = 1.658, g = 0.392, h 4 = 1.682, h 6 = 1.021, h 8 = 9.508, r 2 = infinity, 1 = 0.7, NA = 0.5 f 1 · g = 0. 511792 R / f 1 = 1.2802051 d 1 / f 1 = 2.139517 Second lens: r 3 = infinity, d 3 = 3.480, n 0 = 1.607, g = 0.325, h 4 = 2.0, h 6 = 0.0, h 8 = 0.0, r 4 = infinity d 2 = 11.382 implementation 3 first lens: r 1 = infinity, d 1 = 1.281, n 0 = 1.658, g = 0.392, h 4 = 0.654, h 6 = 2.788, h 8 = 24.710, r 2 = -1.2, 1 = 0.7, NA = 0.5 f 1 · g = 0.49392 R / f 1 = 0.952381 d 1 / f 1 = 1.016667 Second lens: r 3 = infinity, d 3 = 3.480, n 0 = 1.607, g = 0.325, h 4 = 2.0 , H 6 = 0.0, h 8 = 0.0, r 4 = infinity d 2 = 11.833 [Effect of the invention] The optical coupler according to the present invention has an extremely small residual wavefront aberration,
Since the tolerance value for the axis deviation in the direction perpendicular to the optical axis is large,
An optical coupler with good coupling efficiency can be easily manufactured by a simple process.
第１図は本発明の一実施例を示す側面図、第２図ないし
第４図は本発明の実施例１ないし３の収差曲線を示す
図、第５図は従来の光結合器を示す側面図である。 １……光源、２……光結合器光学系 ３……光伝送ファイバ、４……光 束 ５……第１屈折率分布型レンズ ６……第２屈折率分布型レンズ、７……光 軸FIG. 1 is a side view showing an embodiment of the present invention, FIGS. 2 to 4 are diagrams showing aberration curves of Embodiments 1 to 3 of the present invention, and FIG. 5 is a side view showing a conventional optical coupler. It is a figure. 1 ... Light source, 2 ... Optical coupler optical system 3 ... Optical transmission fiber, 4 ... Light bundle 5 ... First gradient index lens 6 ... Second gradient index lens, 7 ... Light axis
Claims (1)
は光軸から半径方向へｒの距離での屈折率ｎ（ｒ）が、
ｎ0を中心軸上屈折率、ｇ、ｈ4、ｈ6、ｈ8を分布定数と
すると、 ｎ2（ｒ）＝ｎ0 2［1-(gr)2+h4(gr)4+h6(gr)6+h8(gr)8＋
・・・］ で表わされる半径方向屈折率分布を有し、第１のレンズ
は一方の面が凸面で他方の面が光軸に垂直な平面であ
り、第２のレンズは両面が光軸に垂直な平面であって光
伝送ファイバの端面と密着して配置され、かつ前記第１
のレンズは、 焦点距離をｆ1、凸面の曲率半径をＲ、中心軸上での厚
みをｄ1としたとき、 ０．４０≦ｆ1・ｇ≦０．６０ ０．８０≦Ｒ／ｆ1≦１．３ ０．５０≦ｄ1／ｆ1≦２．３ の条件を満足していることを特徴とする光結合器。1. A refractive index n (r) at a distance r from the optical axis in a radial direction, wherein both lens media are composed of two lenses in two groups,
If n 0 is the refractive index on the central axis and g, h 4 , h 6 , and h 8 are distribution constants, then n 2 (r) = n 0 2 [1- (gr) 2 + h 4 (gr) 4 + h 6 (gr) 6 + h 8 (gr) 8 +
..], the first lens has a convex surface on one side and the other surface is a plane perpendicular to the optical axis, and the second lens has both surfaces on the optical axis. It is a vertical plane and is disposed in close contact with the end face of the optical transmission fiber, and the first
When the focal length is f 1 , the radius of curvature of the convex surface is R, and the thickness on the central axis is d 1 , the lens of is 0.40 ≦ f 1 · g ≦ 0.60 0.80 ≦ R / f 1 An optical coupler which satisfies the condition of ≦ 1.3 0.50 ≦ d 1 / f 1 ≦ 2.3.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61140638A JPH065332B2 (en) | 1986-06-17 | 1986-06-17 | Optical coupler |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61140638A JPH065332B2 (en) | 1986-06-17 | 1986-06-17 | Optical coupler |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62296105A JPS62296105A (en) | 1987-12-23 |
| JPH065332B2 true JPH065332B2 (en) | 1994-01-19 |
Family
ID=15273331
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61140638A Expired - Lifetime JPH065332B2 (en) | 1986-06-17 | 1986-06-17 | Optical coupler |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH065332B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2699293B1 (en) * | 1992-12-15 | 1995-03-03 | France Telecom | Monolithic optical system comprising improved coupling means between an optical fiber and a phototransducer. |
| JP4037346B2 (en) | 2003-10-08 | 2008-01-23 | 東洋ガラス株式会社 | Optical fiber coupling parts |
| JPWO2007057974A1 (en) * | 2005-11-21 | 2009-04-30 | 東洋ガラス株式会社 | Light emitting element / optical fiber coupling module and parts for light emitting element / optical fiber coupling module |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS556354A (en) * | 1978-06-30 | 1980-01-17 | Agency Of Ind Science & Technol | Refractive index distribution type lens |
| JPS58145909A (en) * | 1982-02-25 | 1983-08-31 | Nippon Sheet Glass Co Ltd | Lens mechanism for coupling light source and optical fiber |
| JPS60173516A (en) * | 1984-02-20 | 1985-09-06 | Nippon Sheet Glass Co Ltd | Optical system for coupling light source |
| JPS60189714A (en) * | 1984-03-09 | 1985-09-27 | Nippon Sheet Glass Co Ltd | Light source and optical fiber coupler |
-
1986
- 1986-06-17 JP JP61140638A patent/JPH065332B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62296105A (en) | 1987-12-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |