JP3820816B2 - Optical branching and coupling device - Google Patents

Description

の角度で拡散される。
【００１０】
したがって、例えば、入射側の光ファイバ７６と出射側の光ファイバ８０との開口数ＮＡが同じのものを使用すると、光拡散部７８を透過した光の拡散角が出射側の光ファイバ８０の開口数で決まる角度Ａより大きくなってしまい、出射側の光ファイバ８０の開口数ＮＡで決まる角度Ａより大きな角度となった分の光（図中の斜線部）は、たとえ、光ファイバ内８０に入射しても光ファイバ８０内で全反射することなく、損失してしまうことになる。
【００１１】
そこで、本発明は、光拡散部で拡散された光を全て出射導光路内で全反射させることにより、光拡散部の拡散によって生じる光の損失を低減ないしなくす光分岐結合装置を提供することを課題とする。
【００１２】
【課題を解決するための手段】
請求項１に記載の光分岐結合装置は、ガウス分布の拡散特性を持ち入射光を拡散する光拡散部を備えると共にこの光拡散部で拡散された光を伝送する透光性媒体と、光拡散部に光を伝達する少なくとも１つ以上の入射導光路と、透光性媒体から出射された光を伝達する少なくとも１つ以上の出射導光路と、を含んで構成された光分岐結合装置であって、入射導光路で発散される光の発散角度Ａと、平行光が光拡散部に入射したときに光拡散部で拡散される拡散光の拡散角度Ｂとに対し、出射導光路の開口数で決まる角度Ｃが、式（１）
【数３】

を満足することを特徴とする。
【００１３】
この構成によれば、入射導光路を伝達してきた光は、入射導光路で発散角度Ａ（入射導光路の開口数で決まる角度Ａ）で発散し、この発散角度Ａで光拡散部に入射する。
【００１４】
ところで、透光性媒体の光拡散部は平行光が入射すると、光拡散部のガウス分布特性により、この平行光は拡散角度Ｂの角度に拡散される。したがって、この光拡散部に発散角度Ａで発散した拡散光が入射した場合には、この入射光は、式（２）
【数４】

の角度で拡散される。
【００１５】
ここで、本装置において、出射導光路は自らの開口数ＮＡで決まる角度Ｃ（ＮＡ＝ｓｉｎＣのＣをいう。）が、上述した
【数５】

以上である。
【００１６】
したがって、光拡散部で光が拡散されたとしても、この拡散光は、その全てが出射導光路に入射され、出射導光路内で全反射されつつ伝達される。このため、光の損失を防止することができる。
なお、上記入射導光路及び出射導光路は、単数の場合でも、複数の場合でも良い。
【００１７】
【発明の実施の形態】
以下、添付図面を参照して、本発明の第１実施形態に係る光分岐結合装置について説明する。図１は本発明の光分岐結合装置の全体構成を示す図であり、（Ａ）がその平面図、（Ｂ）が側面図である。
【００１８】
図１に示すように、光分岐結合装置１０は、全体として、シート状の透光性媒体である光ミキシング部１２と、この光ミキシング部１２の入射側に配置された入射導光路である少なくとも１つ以上の光ファイバ１４と、光ミキシング部１２の出射側に配置された出射側導光路である少なくとも１つ以上の光ファイバ１６とが光学的に結合されて構成されている。
【００１９】
光ミキシング部１２は、屈折率の比較的高いコア層と、このコア層の屈折率よりは小さい屈折率を持つクラッド層とで構成されている。光ミキシング部１２には、例えば、幅６ｍｍ、長さ３０ｍｍ、厚さ１ｍｍの大きさのプラスチックシートが用いられている。
【００２０】
また、光ミキシング部１２の入射側には光ファイバ１４からの出射光を拡散させる光拡散部１８が設けられている。この光拡散部１８は、ガウス分布の拡散特性を備えた、例えば、Ｐｈｙｓｉｃａｌ Ｏｐｔｉｃｓ Ｃｏｒｐｏｒａｔｉｏｎ製の透過型の拡散フィルムで形成されており、この透過型拡散フィルムが光ミキシング部１２の端面に接着されている。この光拡散部１８に入射した平行光が拡散する拡散角度Ｂは２０度（半値全角は４０度となる）である。
【００２１】
一方、入射側の光ファイバ１４は、直径０．９８ｍｍのコア部のまわりをクラッド部で包み、さらにクラッド部のまわりにはプラスチックプライマリコートが施されて構成され、全体として直径１ｍｍの円柱状に形成されている。また、その開口数ＮＡは０．３２である。
【００２２】
また、出射側の光ファイバ１６は、直径０．９８ｍｍのコア部のまわりをクラッド部で包み、さらにクラッド部のまわりにはプラスチックプライマリコートが施されて構成され、全体として直径１ｍｍの円柱状に形成されているが、その開口数ＮＡが０．５のものが用いられている。
【００２３】
なお、光ミキシング部１２の開口数ＮＡを出射側の光ファイバ１６の開口数ＮＡよりも大きくすることにより、入射側の光ファイバ１４から伝達してきた信号光が光ミキシング部１２において損失するのを防止している。
【００２４】
次に、本実施形態の作用及び効果を説明する。
【００２５】
以下の説明において、図２に示す光ファイバ１４、光拡散部１８及び光ファイバ１６は、実際にはそれぞれ接触し光結合しているが、説明の便宜上、光ファイバ１４と光拡散部１８間、光拡散部１８と光ファイバ１６間の距離を離して表している。
【００２６】
図示しない発光素子から出射した信号光は、光ファイバ１４内を伝搬した後、光拡散部１８で拡散されて光ミキシング部１２に入射し、その後光ファイバ１６に入射して図示しない受光素子まで伝達される。
【００２７】
ところで、一般的に、開口数ＮＡはｓｉｎθ（ＮＡ＝ｓｉｎθ）で表され、このときのθが開口数ＮＡで決まる角度となる。したがって、開口数０．３２の光ファイバ１４のコア層を伝達した信号光は、発散角度Ａ（ＮＡ＝ｓｉｎＡとした際のＡ）＝１８．７度の角度で発散される。そして、信号光は、発散光として光拡散部１８に入射する。ここで、光拡散部１８はガウス分布の拡散特性を有しているため、光拡散部１８に平行光が入射した場合の拡散角度をＢとすると、発散角度Ａの発散光が入射した場合の拡散角度Ｄは、式（３）
【数６】

となる。
【００２８】
したがって、本実施形態では、光拡散部１８に入射した信号光は、拡散角度Ｄ＝２７．３８度の角度で拡散される。
【００２９】
ここで、本実施形態では、出射側の光ファイバ１６の開口数ＮＡを０．５としたため、この開口数ＮＡで決まる角度Ｃ（ＮＡ＝ｓｉｎＣとした場合のＣ）は３０度となり、光拡散部１８で拡散された信号光の拡散角度Ｄ＝２７．３８度よりも大きくなる。このため、光拡散部１８で拡散された信号光は、光ミキシング部１２のコア層内で全反射を繰り返した後、光ファイバ１６に入射し光ファイバ１６内で全反射する。
【００３０】
このように、光ファイバ１６の開口数で決まる角度Ｃを、上記のように光拡散部１８で拡散された信号光の拡散角度Ｄよりも大きくすることにより、光ファイバ１６内で全反射させることができるので、光拡散部１８の拡散による損失を低減ないし防止することができる。
【００３１】
また、光ファイバ１６の開口数ＮＡで決まる角度Ｃと光拡散部１８で拡散された信号光の拡散角度Ｄとを同じにしても、光ミキシング部１２を伝搬した信号光が光ファイバ１６内を全反射するため、光拡散部１８の拡散に起因した損失を防止することができる。
【００３２】
なお、入射導光路及び出射導光路として、光ファイバ１４、１６を用いることにより、信号光の伝送効率を小さくすることができる上に、軽くて曲げ易く、発光素子等の配置自由度を上げることができる。
【００３３】
次に、本発明の第２実施形態の光分岐結合装置について説明する。
【００３４】
図３に示すように、本実施形態の光分岐結合装置２０においては、第１実施形態のシート状の光ミキシング部１２に替えて円柱状の光ミキシング部２２を用いた点で第１実施形態の光分岐結合装置１０と異なるが、その他の構成は同じであり、適宜省略して以下に説明する。
【００３５】
また、本実施形態の光分岐結合装置２０は、第１実施形態の光分岐結合装置と同様に、光ミキシング部２２には拡散角度Ｂが２０度の光拡散部２４が形成されており、さらに、入射側の光ファイバ２６には開口数ＮＡが０．３２、出射側の光ファイバ２８には開口数ＮＡが０．５のものが用いられている。
【００３６】
本実施形態の光分岐結合装置２０においても、出射側の光ファイバ２８の開口数ＮＡで決まる角度Ｃを、光拡散部２４で拡散された信号光の拡散角度Ｄよりも大きくなるように設定したので、第１実施形態の光分岐結合装置１０と同様の効果を得ることができる。
【００３７】
次に、本発明の第３実施形態に係る光分岐結合装置について説明する。
【００３８】
また、図４に示すように、本発明の第３実施形態の光分岐結合装置３０では、角柱形状の光ミキシング部３２が用いられている。なお、本実施形態では四角柱の光ミキシング部３２が用いられているが、これに限定されず、五角柱、六角柱等の多角柱形状のものでもよい。
【００３９】
また、光ミキシング部３２には拡散角度Ｂが２０度の光拡散部３４が形成され、さらに、入射側の光ファイバ３６として開口数ＮＡが０．３２、出射側の光ファイバ３８として開口数ＮＡが０．５のものを用いることで、第１実施形態と同様の効果を得ることができる。
【００４０】
なお、上記各実施形態では、入射導光路及び出射導光路として光ファイバを用いたが、開口数ＮＡが定義でき、光を導光するものであれば、これに限られるものではない。
【００４１】
また、図５（Ｂ）に示すように、出射側の光ファイバ４０を角柱形状とすることにより、図５（Ａ）に示すように円柱形状の光ファイバ４２を並べて配置するときに生じる隙間（図中の斜線部分）をなくすことができ、光ミキシング部３２から出射した信号光をすべて光ファイバ４０内に入射させることができるので、角柱形状の光ミキシング部３２との結合損失を低減することができる。
【００４２】
なお、同図においては、光ファイバ４０の断面が四角形状のものを示したが、これに限られず、隙間なく並べられるものであれば、三角形、六角形のものでもよい。
【００４３】
なお、入射側の光ファイバ１４からの信号光を光拡散部１８により複数の光ファイバ１６に分岐する例を示したが、複数の光ファイバ１４からの信号光を光ミキシング部１２でミキシングすることにより、１つの光ファイバ１６に結合することもできる。
【００４４】
【発明の効果】
本発明の光分岐結合装置によれば、入射導光路で発散される光の発散角度Ａと、平行光を入射した場合の光拡散部の拡散特性による拡散角度Ｂに対して、出射導光路の開口数で決まる角度Ｃとが式（１）を満足することにより、透光性媒体から出射した光を出射導光路へ入射させ、出射導光路内で全反射させて伝搬することができるので、光拡散部の拡散によって生じる信号光の損失をなくすことができる。
【図面の簡単な説明】
【図１】（Ａ）は、本発明の第１実施形態に係る光分岐結合装置の平面図であり、（Ｂ）はその側面図である。
【図２】光拡散部により拡散された光と、出射導光路に入射することができる光の範囲との関係を示した図である。
【図３】本発明の第２実施形態に係る光分岐結合装置の全体構成図である。
【図４】本発明の第３実施形態に係る光分岐結合装置の全体構成図である。
【図５】（Ａ）は円形断面の出射導光路を用いた場合の光ミキシング部との光の結合損失を示した図であり、（Ｂ）は四角形断面の出射導光路を用いた場合の図である。
【図６】（Ａ）は入射導光路で発散された発散光を示した図であり、（Ｂ）は光拡散部に平行光が入射した場合に拡散された拡散光を示した図であり、（Ｃ）は光拡散部に発散光が入射した場合に拡散された拡散光を示した図である。
【図７】従来の光分岐結合装置の全体構成図である。
【図８】従来の光分岐結合装置の全体構成図である。
【符号の説明】
１０、２０、３０ 光分岐結合装置
１２、２２、３２ 光ミキシング部（透光性媒体）
１４、２６、３６ 光ファイバ（入射導光路）
１６、２８、３８、４０ 光ファイバ（出射導光路）
１８、２４、３４ 光拡散部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical branching and coupling device for branching an optical signal into a plurality of optical fibers and collecting optical signals from the plurality of optical fibers into one optical signal.
[0002]
[Prior art]
In recent years, an increase in multi-microprocessor systems in which a plurality of microprocessors are combined, and an optical fiber has been used as a data transmission path between the processors. Here, in order to connect a plurality of processors using an optical fiber, an optical branching and coupling device that branches into a plurality of optical fibers and collects optical signals from the plurality of optical fibers into one optical fiber is provided. Necessary.
[0003]
As a conventional technique, as shown in FIG. 7, Japanese Patent Application Laid-Open No. 7-209543 discloses an optical branching and coupling device 60. The optical branching and coupling device 60 includes a mixing unit 56 in which a cladding unit 52 having a refractive index smaller than the refractive index of the core unit 50 is optically bonded to the top, bottom, left and right surfaces of the core unit 50 having a large refractive index. A reflection surface 54 is formed on one end surface of the mixing portion 56. A plurality of optical fibers 58 that transmit optical signals are optically coupled to the end surface of the mixing portion 56 that faces the end surface on which the reflection surface 54 is formed. In this optical branching and coupling device 60, it is possible to branch one input light beam into an arbitrary number of light beams with high accuracy by making the mixing unit 56 sufficiently long.
[0004]
Further, as shown in FIG. 8, an optical branching and coupling device 74 is disclosed in Japanese Patent Laid-Open No. 9-184941. The optical branching and coupling device 74 includes a bundle portion 68 in which the optical fibers 62 are bundled and fixed, and light reflecting means 66 is formed on a part of the end face 64 thereof. The mixing portion 70 is in contact with the end face 64 of the bundle portion 68. Further, a light diffuse reflection means 72 is disposed on the other end face of the mixing unit 70. In this optical branching and coupling device 74, the light reflecting means 66 of the bundle side mirror is formed on the entire surface of the bundle portion 68 other than the core portion of the optical fiber 62 on the surface where the bundle portion 68 and the mixing portion 70 are joined. The signal is multiple-reflected in the mixing unit 70 until it becomes output light, and is not radiated to the outside in a form other than the output light, so that the loss is small and the optical signal can be transmitted efficiently.
[0005]
In addition, although not shown in the drawings, as an optical branching and coupling device that performs low-cost and low-loss branching and coupling, by diffusing and transmitting an optical signal incident on a light-transmitting medium from a plurality of optical fibers, An optical star coupler that branches into a plurality of optical fibers has been proposed. In this optical branching and coupling device, in order to make the branching ratio uniform, a mixing unit and a light diffusion unit are provided in combination.
[0006]
[Problems to be solved by the invention]
However, when a light guide such as an optical fiber is combined with a light diffusing unit, the following problems occur.
[0007]
That is, the light guided by the optical fiber is emitted at an angle determined by the numerical aperture NA. The light emitted from this optical fiber is diffused by the light diffusing section. However, in the case of a transmission type light diffusing section, if the transmittance is increased in order to reduce the loss, the diffusion characteristic will have directivity. become. When the diffusion characteristic of the light diffusion part has directivity, there is a disadvantage that the diffusion characteristic of the light diffusion part differs between when parallel light is incident and when divergent light is incident.
[0008]
Here, for example, as shown in FIG. 6A, the divergence angle of the outgoing light from the optical fiber 76 on the incident side is determined by the numerical aperture NA of the optical fiber 76, and this divergence angle is A (numerical aperture NA = sinA). Point to A). Further, as shown in FIG. 6B, the diffusion angle when the parallel light L is incident on the light diffusion portion 78 having the diffusion characteristic of Gaussian distribution is set to B.
[0009]
At this time, when the light diverged at the divergence angle A is incident on the light diffusion portion 78, the light is expressed by the equation (2) as shown in FIG.
[Expression 2]

Is diffused at an angle of
[0010]
Therefore, for example, when the optical fibers 76 on the incident side and the optical fibers 80 on the outgoing side have the same numerical aperture NA, the diffusion angle of the light transmitted through the light diffusing portion 78 is the opening of the optical fiber 80 on the outgoing side. The light (hatched portion in the figure) corresponding to the angle A larger than the angle A determined by the number and larger than the angle A determined by the numerical aperture NA of the optical fiber 80 on the output side is, for example, in the optical fiber 80. Even if it is incident, it is lost without being totally reflected in the optical fiber 80.
[0011]
Accordingly, the present invention provides an optical branching and coupling device that reduces or eliminates light loss caused by diffusion of the light diffusing unit by totally reflecting all of the light diffused by the light diffusing unit within the output light guide. Let it be an issue.
[0012]
[Means for Solving the Problems]
The optical branching and coupling device according to claim 1 includes a light diffusing unit that diffuses incident light with a gaussian diffusion characteristic, and transmits light diffused by the light diffusing unit, and light diffusion. An optical branching and coupling device including at least one incident light guide for transmitting light to the unit and at least one output light guide for transmitting light emitted from the translucent medium. The numerical aperture of the outgoing light guide with respect to the divergence angle A of light emitted from the incident light guide and the diffusion angle B of diffused light diffused by the light diffuser when parallel light enters the light diffuser The angle C determined by Equation (1)
[Equation 3]

It is characterized by satisfying.
[0013]
According to this configuration, the light transmitted through the incident light guide diverges at the divergence angle A (angle A determined by the numerical aperture of the incident light guide) at the incident light guide, and enters the light diffusion portion at the divergence angle A. .
[0014]
By the way, when parallel light enters the light diffusing portion of the translucent medium, the parallel light is diffused to an angle of diffusion angle B due to the Gaussian distribution characteristic of the light diffusing portion. Therefore, when the diffused light diverged at the divergence angle A is incident on the light diffusing portion, the incident light is expressed by the equation (2).
[Expression 4]

Is diffused at an angle of
[0015]
Here, in this apparatus, the outgoing light guide has an angle C determined by its own numerical aperture NA (NA = C of sin C) as described above.

That's it.
[0016]
Therefore, even if light is diffused by the light diffusing unit, all of this diffused light is incident on the outgoing light guide and transmitted while being totally reflected in the outgoing light guide. For this reason, loss of light can be prevented.
The incident light guide path and the output light guide path may be singular or plural.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an optical branching and coupling device according to a first embodiment of the present invention will be described with reference to the accompanying drawings. 1A and 1B are diagrams showing the overall configuration of an optical branching and coupling device of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a side view.
[0018]
As shown in FIG. 1, the optical branching and coupling device 10 as a whole is an optical mixing unit 12 that is a sheet-like translucent medium and an incident light guide disposed on the incident side of the optical mixing unit 12. The one or more optical fibers 14 and at least one or more optical fibers 16 that are output side light guides disposed on the output side of the optical mixing unit 12 are optically coupled to each other.
[0019]
The optical mixing unit 12 includes a core layer having a relatively high refractive index and a clad layer having a refractive index smaller than that of the core layer. For the optical mixing unit 12, for example, a plastic sheet having a width of 6 mm, a length of 30 mm, and a thickness of 1 mm is used.
[0020]
A light diffusing unit 18 that diffuses light emitted from the optical fiber 14 is provided on the incident side of the light mixing unit 12. The light diffusing portion 18 is formed of a transmissive diffusion film made of, for example, Physical Optics Corporation, which has a Gaussian distribution characteristic, and the transmissive diffusion film is bonded to the end face of the light mixing portion 12. Yes. The diffusion angle B at which the parallel light incident on the light diffusion portion 18 diffuses is 20 degrees (the full width at half maximum is 40 degrees).
[0021]
On the other hand, the optical fiber 14 on the incident side is configured by wrapping a core portion having a diameter of 0.98 mm with a clad portion, and further, a plastic primary coat is applied around the clad portion, and is formed into a cylindrical shape having a diameter of 1 mm as a whole. Is formed. The numerical aperture NA is 0.32.
[0022]
The optical fiber 16 on the output side is configured by wrapping around a core portion having a diameter of 0.98 mm with a clad portion, and further, a plastic primary coat is applied around the clad portion. Although it is formed, it has a numerical aperture NA of 0.5.
[0023]
Note that by making the numerical aperture NA of the optical mixing unit 12 larger than the numerical aperture NA of the optical fiber 16 on the emission side, the signal light transmitted from the optical fiber 14 on the incident side is lost in the optical mixing unit 12. It is preventing.
[0024]
Next, the operation and effect of this embodiment will be described.
[0025]
In the following description, the optical fiber 14, the light diffusion unit 18, and the optical fiber 16 shown in FIG. 2 are actually in contact with each other and optically coupled, but for convenience of description, between the optical fiber 14 and the light diffusion unit 18, The distance between the light diffusion portion 18 and the optical fiber 16 is shown separated.
[0026]
The signal light emitted from the light emitting element (not shown) propagates through the optical fiber 14, is diffused by the light diffusion unit 18, enters the optical mixing unit 12, and then enters the optical fiber 16 and is transmitted to the light receiving element (not shown). Is done.
[0027]
By the way, the numerical aperture NA is generally expressed by sin θ (NA = sin θ), and θ at this time is an angle determined by the numerical aperture NA. Therefore, the signal light transmitted through the core layer of the optical fiber 14 having a numerical aperture of 0.32 is diverged at an angle of divergence angle A (A when NA = sinA) = 18.7 degrees. Then, the signal light enters the light diffusion unit 18 as diverging light. Here, since the light diffusing unit 18 has a Gaussian diffusion characteristic, assuming that the diffusion angle when the parallel light is incident on the light diffusing unit 18 is B, the divergent light having the divergence angle A is incident. The diffusion angle D is given by equation (3)
[Formula 6]

It becomes.
[0028]
Therefore, in the present embodiment, the signal light incident on the light diffusing unit 18 is diffused at a diffusion angle D = 27.38 degrees.
[0029]
Here, in the present embodiment, since the numerical aperture NA of the optical fiber 16 on the emission side is set to 0.5, the angle C determined by the numerical aperture NA (C when NA = sinC) is 30 degrees, and light diffusion is performed. The diffusion angle D of the signal light diffused by the unit 18 becomes larger than 27.38 degrees. For this reason, the signal light diffused by the light diffusing unit 18 repeats total reflection in the core layer of the optical mixing unit 12 and then enters the optical fiber 16 and is totally reflected in the optical fiber 16.
[0030]
As described above, the angle C determined by the numerical aperture of the optical fiber 16 is made larger than the diffusion angle D of the signal light diffused by the light diffusing unit 18 as described above, so that it is totally reflected in the optical fiber 16. Therefore, it is possible to reduce or prevent loss due to diffusion of the light diffusing unit 18.
[0031]
Even if the angle C determined by the numerical aperture NA of the optical fiber 16 and the diffusion angle D of the signal light diffused by the light diffusing unit 18 are the same, the signal light propagated through the optical mixing unit 12 passes through the optical fiber 16. Since it is totally reflected, it is possible to prevent loss due to the diffusion of the light diffusing unit 18.
[0032]
In addition, by using the optical fibers 14 and 16 as the incident light guide path and the output light guide path, the transmission efficiency of the signal light can be reduced, and it is light and easy to bend, and the degree of freedom in arranging the light emitting elements and the like is increased. Can do.
[0033]
Next, an optical branching and coupling device according to a second embodiment of the present invention will be described.
[0034]
As shown in FIG. 3, in the optical branching and coupling device 20 of the present embodiment, the first embodiment is used in that a cylindrical optical mixing unit 22 is used instead of the sheet-shaped optical mixing unit 12 of the first embodiment. Although the configuration is the same as that of the optical branching and coupling device 10 of FIG.
[0035]
Further, in the optical branching and coupling device 20 of the present embodiment, similarly to the optical branching and coupling device of the first embodiment, the light mixing unit 22 is formed with a light diffusion unit 24 having a diffusion angle B of 20 degrees. The incident-side optical fiber 26 has a numerical aperture NA of 0.32, and the output-side optical fiber 28 has a numerical aperture NA of 0.5.
[0036]
Also in the optical branching and coupling device 20 of the present embodiment, the angle C determined by the numerical aperture NA of the optical fiber 28 on the emission side is set to be larger than the diffusion angle D of the signal light diffused by the light diffusion unit 24. Therefore, the same effect as that of the optical branching and coupling device 10 of the first embodiment can be obtained.
[0037]
Next, an optical branching and coupling device according to a third embodiment of the present invention will be described.
[0038]
Moreover, as shown in FIG. 4, in the optical branching and coupling apparatus 30 of the third embodiment of the present invention, a prismatic optical mixing unit 32 is used. In the present embodiment, the quadrangular prism optical mixing unit 32 is used. However, the present invention is not limited to this, and a polygonal prism shape such as a pentagonal prism or a hexagonal prism may be used.
[0039]
The light mixing section 32 is formed with a light diffusion section 34 having a diffusion angle B of 20 degrees. Further, the numerical aperture NA is 0.32 as the optical fiber 36 on the incident side, and the numerical aperture NA as the optical fiber 38 on the output side. By using one having a value of 0.5, the same effect as in the first embodiment can be obtained.
[0040]
In each of the above embodiments, optical fibers are used as the incident light guide and the output light guide. However, the present invention is not limited to this as long as the numerical aperture NA can be defined and light is guided.
[0041]
Further, as shown in FIG. 5 (B), by forming the optical fiber 40 on the emission side into a prismatic shape, a gap (when a cylindrical optical fiber 42 is arranged side by side as shown in FIG. 5 (A) ( (Shaded portions in the figure) can be eliminated, and all the signal light emitted from the optical mixing section 32 can be made incident into the optical fiber 40, so that the coupling loss with the prism-shaped optical mixing section 32 can be reduced. Can do.
[0042]
In the figure, the optical fiber 40 has a rectangular cross section. However, the cross section is not limited to this, and the optical fiber 40 may be triangular or hexagonal as long as it is arranged without a gap.
[0043]
Although an example in which the signal light from the incident-side optical fiber 14 is branched to the plurality of optical fibers 16 by the light diffusion unit 18, the signal light from the plurality of optical fibers 14 is mixed by the optical mixing unit 12. Thus, it is possible to couple to one optical fiber 16.
[0044]
【The invention's effect】
According to the optical branching and coupling device of the present invention, the output light guide path has a divergence angle A of light emitted from the incident light guide path and a diffusion angle B due to the diffusion characteristics of the light diffusion section when parallel light is incident. Since the angle C determined by the numerical aperture satisfies the expression (1), the light emitted from the translucent medium can be incident on the output light guide, and can be totally reflected in the output light guide. Loss of signal light caused by diffusion of the light diffusing unit can be eliminated.
[Brief description of the drawings]
FIG. 1A is a plan view of an optical branching and coupling device according to a first embodiment of the present invention, and FIG. 1B is a side view thereof.
FIG. 2 is a diagram showing the relationship between the light diffused by the light diffusing unit and the range of light that can enter the light guide.
FIG. 3 is an overall configuration diagram of an optical branching and coupling device according to a second embodiment of the present invention.
FIG. 4 is an overall configuration diagram of an optical branching and coupling device according to a third embodiment of the present invention.
FIG. 5A is a view showing a coupling loss of light with an optical mixing unit when an output light guide having a circular cross section is used, and FIG. 5B is a diagram when an output light guide having a square cross section is used. FIG.
6A is a diagram showing divergent light diverged in an incident light guide, and FIG. 6B is a diagram showing diffused light diffused when parallel light is incident on a light diffusing section. (C) is the figure which showed the diffused light diffused when divergent light injects into the light-diffusion part.
FIG. 7 is an overall configuration diagram of a conventional optical branching and coupling device.
FIG. 8 is an overall configuration diagram of a conventional optical branching and coupling device.
[Explanation of symbols]
10, 20, 30 Optical branching and coupling device 12, 22, 32 Optical mixing unit (translucent medium)
14, 26, 36 Optical fiber (incident light guide)
16, 28, 38, 40 Optical fiber (outgoing light guide)
18, 24, 34 Light diffusion part

Claims (1)

A translucent medium having a Gaussian distribution of diffusion characteristics and a light diffusing section for diffusing incident light and transmitting light diffused by the light diffusing section;
At least one incident light guide for transmitting light to the light diffusing section;
At least one outgoing light guide for transmitting light emitted from the translucent medium;
An optical branching and coupling device comprising:
The divergence angle A of the light diverged in the incident light guide and the diffusion angle B of the diffused light diffused in the light diffusing unit when parallel light enters the light diffusing unit The angle C determined by the numerical aperture is expressed by Equation (1).

An optical branching and coupling device characterized by satisfying

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