JP2010161194A - Bidirectional optical module - Google Patents

Bidirectional optical module Download PDF

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JP2010161194A
JP2010161194A JP2009002316A JP2009002316A JP2010161194A JP 2010161194 A JP2010161194 A JP 2010161194A JP 2009002316 A JP2009002316 A JP 2009002316A JP 2009002316 A JP2009002316 A JP 2009002316A JP 2010161194 A JP2010161194 A JP 2010161194A
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light
filter
optical module
wavelength
transmission
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Toshiaki Kihara
利彰 木原
Hiromi Nakanishi
裕美 中西
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Sumitomo Electric Industries Ltd
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Sumitomo Electric Industries Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a single-core bidirectional optical module of one-package type, capable of reducing optical crosstalk without being affected by incident angle and characteristics of a WDN filter. <P>SOLUTION: In the single-core bidirectional optical module of one-package type, a cap 11 having a translucent window is sealed on a stem 2 where a light-emitting element 4 for emitting transmission light, a light-receiving element 6 for receiving reception light, and a wavelength multiplexing/demultiplexing filter 8 are mounted. The light-emitting element 4 is mounted on the stem 11 through a heatsink 5, and the light-receiving element 6 is mounted through a sub-mount 7 such that a range in which outgoing light from the light-emitting element 4 penetrates a light-receiving surface 6a of the light-receiving element 6 is shielded by the heatsink 5. Between the wavelength multiplexing/demultiplexing filter 8 and the light-receiving element 6, a cut filter 9 is arranged for absorbing the wavelength light other than the reception wavelength light, and the heatsink 5 is composed of materials not allowing transmission wavelength light to penetrate therethrough. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、１つのパッケージ内に発光素子および受光素子を搭載し、光信号の送受信に用いられる同軸型の一心双方向光モジュールに関する。   The present invention relates to a coaxial single-fiber bidirectional optical module in which a light emitting element and a light receiving element are mounted in one package and used for transmission / reception of an optical signal.

光通信技術の進展に伴い、ＦＴＴＨ（Fiber To The Home）に代表される加入者系通信網（アクセス系）では、より高速で大容量の通信が、適切なコストで可能となるＰＯＮ（Passive Optical Network）システムの導入が進んでいる。このＰＯＮシステムは、一芯双方向通信方式の採用により、局側機器（ＯＬＴ：Optical Line Terminal ）とユーザ側機器（ＯＮＵ：Optical Network Unit ）との間の光ファイバ伝送路のファイバ本数を減らし、メタルケーブル並みの低価格で、より高速なサービスを実現している。具体的には、１本の光ファイバで、１.３１μｍ帯と１.４９μｍ帯の２波長で送受信を行う波長多重方式（ＷＤＭ：Wavelength Division Multiplexing）である。   With the advancement of optical communication technology, PON (Passive Optical), which enables high-speed and large-capacity communication at an appropriate cost, in subscriber communication networks (access systems) represented by FTTH (Fiber To The Home). Network) system is being introduced. This PON system reduces the number of fibers in the optical fiber transmission line between the station side equipment (OLT: Optical Line Terminal) and the user side equipment (ONU: Optical Network Unit) by adopting the single core bidirectional communication system. It offers a faster service at the same low price as a metal cable. Specifically, this is a wavelength division multiplexing (WDM) method in which transmission / reception is performed with two wavelengths of 1.31 μm band and 1.49 μm band using one optical fiber.

このようなＰＯＮシステムに用いるための一芯双方向光モジュールでは、レーザダイオード等の発光素子（以下、ＬＤという）から出射される送信光を光ファイバに結合させる一方で、光ファイバを伝送してきた受信光をフォトダイオード等の受光素子（以下、ＰＤという）に結合させている。光ファイバと送受信光との結合方法及び結合装置については、今までにも多くの提案がなされている。   In a single-core bidirectional optical module for use in such a PON system, transmission light emitted from a light emitting element such as a laser diode (hereinafter referred to as LD) is coupled to an optical fiber while transmitting the optical fiber. Received light is coupled to a light receiving element (hereinafter referred to as PD) such as a photodiode. Many proposals have been made for a method and an apparatus for coupling an optical fiber and transmitted / received light.

従来は、送信用のＬＤを内蔵するＣＡＮパッケージと受信用のＰＤを内蔵するＣＡＮパッケージを用いた２パッケージ構造の光モジュールが、組立ても従来方法で行えるということで、開発が進められていた。しかし、冒頭に記したように、低価格の要求により一芯双方向の通信で、更なるコストダウンを図ることが必要とされ、１つのＣＡＮパッケージ内に送信用のＬＤと受信用のＰＤの両方を内蔵させた１パッケージ構造の一芯双方向光モジュールについても、開発が進められるようになった。   Conventionally, development has progressed because an optical module having a two-package structure using a CAN package containing a transmission LD and a CAN package containing a reception PD can be assembled by a conventional method. However, as described at the beginning, it is necessary to further reduce the cost by single-core two-way communication due to low cost requirements, and there is a need for transmission LD and reception PD in one CAN package. Development of a single-core bidirectional optical module with a single package structure in which both of them are built has also been promoted.

図４は、現在ＯＬＴ側で用いられる１パーケージ構造の一芯双方向光モジュールの一例で、光モジュール１は同軸型のパッケージで形成されている。パッケージ内には、複数のリード端子３が設けられたステム２に信号光を送信するＬＤ４が、冷却のためのヒートシンク５等を介して搭載され、また、受信光を受光するＰＤ６が、サブマウント７等を介して搭載されている。また、ステム２上に搭載されたＬＤ４及びＰＤ６とその他の電子部品を封止するようにして、送信光（ＬＤ光）及び受信光を集光させるレンズ１０を設けたキャップ１１が取付けられている。キャップ１１には、光ファイバとの接続を形成するスリーブ部材（図示せず）を位置決めして保持するホルダ１２が取付け固定されている。   FIG. 4 shows an example of a single-core bidirectional optical module having a single package structure that is currently used on the OLT side. The optical module 1 is formed of a coaxial package. In the package, an LD 4 for transmitting signal light to a stem 2 provided with a plurality of lead terminals 3 is mounted via a heat sink 5 for cooling, and a PD 6 for receiving received light is a submount. 7 etc. A cap 11 provided with a lens 10 for condensing transmission light (LD light) and reception light is attached so as to seal the LD 4 and PD 6 mounted on the stem 2 and other electronic components. . A holder 12 for positioning and holding a sleeve member (not shown) that forms a connection with the optical fiber is attached and fixed to the cap 11.

レンズ１０とＬＤ４及びＰＤ６の光学経路上には、送信光（実線で示す）を反射させると共に受信光（点線で示す）を透過させるＷＤＭフィルタ８が傾斜させて配置される。ＬＤ４の出射部４ａから出射された送信光は、このＷＤＭフィルタ８で反射され、レンズ１０で集光されてホルダ１２の開口１２ａを通って、スリーブ部材に固定されているファイバスタブ１３の光ファイバ１３ａに入射され、外部の光ファイバ伝送路に送出される。外部の光ファイバ伝送路から送られてきた受信光は、ファイバスタブ１３の光ファイバ１３ａから出射され、ホルダ１２の開口１２ａを通ってレンズ１０で集光され、ＷＤＭフィルタ８を透過してＰＤ６の受光面６ａで受光される。   On the optical path of the lens 10 and the LD 4 and PD 6, a WDM filter 8 that reflects transmission light (shown by a solid line) and transmits reception light (shown by a dotted line) is disposed at an inclination. The transmission light emitted from the emission portion 4a of the LD 4 is reflected by the WDM filter 8, collected by the lens 10, passes through the opening 12a of the holder 12, and is fixed to the sleeve member. The light is incident on 13a and sent to an external optical fiber transmission line. The received light transmitted from the external optical fiber transmission line is emitted from the optical fiber 13a of the fiber stub 13, is collected by the lens 10 through the opening 12a of the holder 12, passes through the WDM filter 8, and passes through the PD6. Light is received by the light receiving surface 6a.

また、ＬＤ４から出射された信号光の一部は、ＷＤＭフィルタ８により反射されファイバスタブ１３に入射されて外部に送信される以外に、ＷＤＭフィルタ８をすり抜けたり透過したりして、外部に出射されずにキャップ１１内で反射を繰り返しながら減衰する迷光となる。このキャップ１１内で迷光となった光が、受信用のＰＤ６で受光すると、光クロストークの原因となり、受信特性を劣化させることになる。   In addition, a part of the signal light emitted from the LD 4 is reflected by the WDM filter 8, enters the fiber stub 13 and is transmitted to the outside, and passes through or passes through the WDM filter 8 to be emitted to the outside. Instead, it becomes stray light that attenuates while being repeatedly reflected in the cap 11. If the light that has become stray light in the cap 11 is received by the PD 6 for reception, it causes optical crosstalk and degrades reception characteristics.

これを改善する方法として、ＰＤ６とＷＤＭフィルタ８との間に、特定波長の光を透過し、それ以外の波長を遮断するカットフィルタ９（バンドパスフィルタともいう）を配置し、送信光の漏れ光や反射光がキャップ内で迷光となってＰＤで受光されるのを防止している。
なお、特許文献１には、キャップ表面にＺｎ−Ｎｉメッキなどによる黒色皮膜を設けてＬＤ光の反射による迷光を抑制することが開示され、特許文献２には、キャップ表面に無光沢パラジウムメッキを施して、同様にＬＤ光の反射による迷光を抑制することが開示されている。 As a method of improving this, a cut filter 9 (also referred to as a bandpass filter) that transmits light of a specific wavelength and blocks other wavelengths is disposed between the PD 6 and the WDM filter 8 to leak transmission light. Light or reflected light is prevented from being received by the PD as stray light in the cap.
Patent Document 1 discloses that a black film such as Zn—Ni plating is provided on the cap surface to suppress stray light due to reflection of LD light, and Patent Document 2 discloses matte palladium plating on the cap surface. In addition, it is disclosed that stray light due to reflection of LD light is similarly suppressed.

特開２００３−２０４００６号公報JP 2003-204006 A 特開２００６−１２０８６４号公報JP 2006-120864 A

図５は、ＬＤ４から出射される送信光の出射状態を模擬的に示した図である。ＬＤ４の出射部４ａから出射される光は、ガウシアンビームであり、例えば、遠視野像（ＦＦＰ：Far Filed Pattern ）は、１／ｅ２の半幅でθ＝２０°〜２５°の広がりを持っている。このため、ＷＤＭフィルタ８は、広がりをもつ送信光が照射されるに十分なサイズのものが必要とされ、少なくともθ＝３０°の広がりの送信光を照射することが可能なサイズのものが用いられる。 FIG. 5 is a diagram schematically showing the emission state of the transmission light emitted from the LD 4. The light emitted from the emitting portion 4a of the LD 4 is a Gaussian beam. For example, a far field image (FFP: Far Filed Pattern) has a half width of 1 / e 2 and a spread of θ = 20 ° to 25 °. Yes. For this reason, the WDM filter 8 is required to have a size sufficient to irradiate spread transmission light, and has a size capable of irradiating transmission light having a spread of at least θ = 30 °. It is done.

ＷＤＭフィルタ８に対する送信光の入射角αは、図５（Ｂ）に示すように、ＷＤＭフィルタ８の反射面の法線に対する角度で表される。すなわち、ＦＲＰの半幅θとすると、入射角αは、（９０°−θ）で表すことができる。例えば、図５（Ｂ）において、ＷＤＭフィルタ８の傾斜角が４５°で、ＦＲＰの半幅θ＝３０°とすると、ＬＤ４の出射部４ａから最も離れた位置での光の入射角αは７５°であり、ＬＤ４の出射部４ａから最も近い位置での光の入射角αは１５°となる。   The incident angle α of the transmission light with respect to the WDM filter 8 is represented by an angle with respect to the normal line of the reflection surface of the WDM filter 8 as shown in FIG. That is, when the half width θ of the FRP is used, the incident angle α can be expressed by (90 ° −θ). For example, in FIG. 5B, when the inclination angle of the WDM filter 8 is 45 ° and the half width θ of the FRP is 30 °, the incident angle α of light at the position farthest from the emitting portion 4a of the LD 4 is 75 °. The incident angle α of the light at the position closest to the emitting portion 4a of the LD 4 is 15 °.

このＷＤＭフィルタ８に照射された送信光は、レンズ１０方向に向かうように反射されるが、一部はＷＤＭフィルタ８を透過して突き抜ける。このＷＤＭフィルタ８を透過した光は迷光となるが、その透過率は上記の入射角αによって異なるとともに、入射される送信光の波長によっても異なる。この送信光のうち、ＬＤ４のＦＲＰの裾方向でＰＤ６に近い光、すなわち入射角αの小さい光で、ＬＤ４の出射部と受信用のＰＤ６の受光面を結ぶ直線（Ｌ）を通る光は、ＷＤＮフィルタ８とカットフィルタ９を透過して、受信用のＰＤ６で直接受光される可能性がある。この受光量が多いと、光クロストークの原因となり、受信特性を劣化させることになる。   The transmitted light applied to the WDM filter 8 is reflected toward the lens 10, but part of the transmitted light passes through the WDM filter 8 and penetrates. The light transmitted through the WDM filter 8 becomes stray light, but the transmittance varies depending on the incident angle α and also depends on the wavelength of incident transmission light. Of this transmitted light, light that is close to PD6 in the skirt direction of the FRP of LD4, that is, light that has a small incident angle α, and passes through a straight line (L) that connects the emitting portion of LD4 and the light receiving surface of PD6 for reception, There is a possibility that light is directly received by the PD 6 for reception through the WDN filter 8 and the cut filter 9. If this amount of received light is large, it causes optical crosstalk and degrades reception characteristics.

なお、アクセス系のＰＯＮシステムでは、ＯＮＵ側は、送信波長１３１０ｎｍ、受信波長が１４９０ｎｍ、ＯＬＴ側は、送信波長が１４９０ｎｍ、受信波長が１３１０ｎｍが用いられる。このため、ＷＤＭフィルタ８は、ＯＮＵ側に用いるものと、ＯＬＴ側に用いるものとでは、そのＷＤＭフィルタ特性が異なるものが用いられる。   In the access PON system, the transmission wavelength is 1310 nm and the reception wavelength is 1490 nm on the ONU side, and the transmission wavelength is 1490 nm and the reception wavelength is 1310 nm on the OLT side. For this reason, the WDM filter 8 having different WDM filter characteristics is used between the WDM filter 8 used on the ONU side and the WDM filter 8 used on the OLT side.

ＯＮＵ側の光モジュールでは、図６（Ａ）に示すようなＷＤＮフィルタ特性のものが用いられる。このＷＤＭフィルタにおいては、入射角が小さい光（ＬＤ４のＦＲＰの裾方向側のＰＤ６に近い光）ほど反射率が高く、透過光は微量である。そして、この透過光は、カットフィルタ９でカットされて、更に微量とされる。このため、ＷＤＮフィルタ８とカットフィルタ９を透過して、受信用のＰＤ６で受光するＬＤ４の送信光は少なく、光クロストークを抑制することができる。具体的には、−４０ｄＢ以下とすることが可能とされている。   In the optical module on the ONU side, one having a WDN filter characteristic as shown in FIG. In this WDM filter, the smaller the incident angle (light closer to the PD 6 on the skirt direction side of the FRP of the LD 4), the higher the reflectance, and the smaller the amount of transmitted light. Then, this transmitted light is cut by the cut filter 9 to be further minute. For this reason, there is little transmission light of LD4 which permeate | transmits the WDN filter 8 and the cut filter 9, and is received by PD6 for reception, and can suppress optical crosstalk. Specifically, it can be made -40 dB or less.

一方、ＯＬＴ側の光モジュールでは、図６（Ｂ）に示すようなＷＤＮフィルタ特性のものが用いられる。このＷＤＭフィルタ８においては、入射角が小さい光ほど反射率が低下し、より多くの光が透過する。この透過光は、カットフィルタ９である程度はカットされるが、カットフィルタ９を透過する漏れ光の量はＯＮＵ側と比べると多くなっている。このため、ＷＤＮフィルタ８とカットフィルタ９を透過して、受信用のＰＤ６で受光してしまうＬＤ４の送信光は多く、光クロストークが劣化する。具体的には、−３２ｄＢ前後となる。   On the other hand, the optical module on the OLT side has a WDN filter characteristic as shown in FIG. In the WDM filter 8, the smaller the incident angle, the lower the reflectance, and more light is transmitted. This transmitted light is cut to some extent by the cut filter 9, but the amount of leaked light that passes through the cut filter 9 is larger than that on the ONU side. For this reason, there is much transmission light of LD4 which permeate | transmits the WDN filter 8 and the cut filter 9, and is received by PD6 for reception, and optical crosstalk deteriorates. Specifically, it is around -32 dB.

本発明は、上述した実情に鑑みてなされたもので、ＷＤＮフィルタの特性や入射角の影響を受けることなく、光クロストークを低減できる１パッケージ型の一心双方向光モジュールの提供を目的とする。   The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a one-package single-fiber bidirectional optical module that can reduce optical crosstalk without being affected by the characteristics of the WDN filter and the incident angle. .

本発明による一心双方向光モジュールは、送信光を発光する発光素子と受信光を受信する受光素子、並びに、波長合分波フィルタを搭載したステム上に、光透過窓を有するキャップを封着した１パッケージ型の一心双方向光モジュールで、ステム上にヒートシンクを介して発光素子が実装され、サブマウントを介して受光素子が実装され、発光素子の出射光が受光素子の受光面を透視する範囲を、ヒートシンクが遮るように構成されていることを特徴とする。
なお、前記の波長合分波フィルタと受光素子の間には、受信波長光の以外の波長光を吸収するカットフィルタが配され、ヒートシンクは送信波長光を透過しない材料で形成されている。 A single-fiber bidirectional optical module according to the present invention has a cap having a light transmission window sealed on a light-emitting element that emits transmission light, a light-receiving element that receives reception light, and a stem on which a wavelength multiplexing / demultiplexing filter is mounted. A single-package bidirectional optical module in which a light-emitting element is mounted on a stem via a heat sink, a light-receiving element is mounted via a submount, and the light emitted from the light-emitting element is seen through the light-receiving surface of the light-receiving element The heat sink is configured to be shielded by the heat sink.
A cut filter that absorbs light of wavelengths other than the reception wavelength light is disposed between the wavelength multiplexing / demultiplexing filter and the light receiving element, and the heat sink is formed of a material that does not transmit the transmission wavelength light.

本発明によれば、送信用の発光素子からの送信光の出射部と、受信用の受光素子の受光面を結ぶ線上の送信光は、発光素子が搭載されるヒートシンクより遮られる。このため、受光素子の受光面が、ＷＤＭフィルタを透過した送信光を直接受光するのを抑制することができ、ＯＬＴ側、ＯＮＵ側のいずれの機器においても、光クロストークを低減でき良好な受信特性を得ることができる。   According to the present invention, the transmission light on the line connecting the emission part of the transmission light from the light emitting element for transmission and the light receiving surface of the light receiving element for reception is blocked by the heat sink on which the light emitting element is mounted. As a result, the light receiving surface of the light receiving element can be prevented from directly receiving the transmitted light that has passed through the WDM filter, and optical crosstalk can be reduced in both the OLT side and the ONU side devices. Characteristics can be obtained.

本発明の一心双方向光モジュールの概略を説明する図である。It is a figure explaining the outline of the single fiber bidirectional optical module of the present invention. 本発明の要部を示す図である。It is a figure which shows the principal part of this invention. 本発品と従来品との比較結果を示す図である。It is a figure which shows the comparison result of this product and a conventional product. 従来の一心双方向光モジュールの概略を説明する図である。It is a figure explaining the outline of the conventional single fiber bidirectional optical module. 従来の送信光の反射と透過を説明する図である。It is a figure explaining the reflection and transmission of the conventional transmission light. ＯＮＵ側とＯＬＴ側の光モジュールに搭載されるＷＤＭフィルタの特性を示す図である。It is a figure which shows the characteristic of the WDM filter mounted in the optical module of ONU side and OLT side.

図により本発明の実施の形態を説明する。図１は本発明による１パッケージ型の一心双方向光モジュールの概略を説明する図で、図中、１は光モジュール、２はステム、３はリード端子、４は発光素子（ＬＤ）、４ａは出射部、５はヒートシンク、５ａは上面、６は受光素子（ＰＤ）、６ａは受光面、７はサブマウント、８はＷＤＭフィルタ、９はカットフィルタ、１０はレンズ、１１はキャップ、１２はホルダ、１２ａは開口、１３はファイバスタブ、１３ａは光ファイバを示す。   Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining an outline of a single-package bidirectional optical module according to the present invention. In FIG. 1, 1 is an optical module, 2 is a stem, 3 is a lead terminal, 4 is a light emitting element (LD), 4a is Emitting part, 5 is a heat sink, 5a is an upper surface, 6 is a light receiving element (PD), 6a is a light receiving surface, 7 is a submount, 8 is a WDM filter, 9 is a cut filter, 10 is a lens, 11 is a cap, and 12 is a holder , 12a are openings, 13 is a fiber stub, and 13a is an optical fiber.

本発明による一心双方向光モジュールは、従来例の図４で説明したのと同様に、同軸型の１パッケージで形成される。パッケージ内には、複数のリード端子３が設けられたステム２上に、信号光を送信するＬＤ４が冷却のためのヒートシンク５等を介して搭載され、また、受信光を受光するＰＤ６がサブマウント７等を介して搭載される。また、ステム２上に搭載されたＬＤ４及びＰＤ６とその他の電子部品を封止するようにして、送信光および受信光を集光させるレンズ１０を設けたキャップ１１が取付けられ、パッケージ内が封止される。なお、キャップ１１には、光ファイバとの接続を形成するスリーブ部材（図示せず）を位置決めして保持するホルダ１２が取付け固定される。   The single-fiber bidirectional optical module according to the present invention is formed by a single coaxial type package, as described with reference to FIG. In the package, an LD 4 for transmitting signal light is mounted via a heat sink 5 for cooling on a stem 2 provided with a plurality of lead terminals 3, and a PD 6 for receiving received light is a submount. 7 etc. Further, a cap 11 provided with a lens 10 for condensing transmission light and reception light is attached so as to seal the LD 4 and PD 6 mounted on the stem 2 and other electronic components, and the inside of the package is sealed. Is done. A holder 12 that positions and holds a sleeve member (not shown) that forms a connection with the optical fiber is attached and fixed to the cap 11.

レンズ１０とＬＤ４およびＰＤ６の光学経路上には、ＬＤ４から照射される送信光を反射させると共に受信光を透過させるＷＤＭフィルタ８が、所定の傾斜角で配置される。ＬＤ４の出射部４ａから出射された送信光は、このＷＤＭフィルタ８で反射され、レンズ１０で集光されてホルダ１２の開口１２ａを通ってスリーブ部材に固定されているファイバスタブ１３の光ファイバ１３ａに入射され、外部の光ファイバ伝送路に送出される。外部の光ファイバ伝送路から送られてきた受信光は、ファイバスタブ１３の光ファイバ１３ａから出射され、ホルダ１２の開口１２ａを通ってレンズ１０で集光され、ＷＤＭフィルタ８を透過して受信用のＰＤ６で受光される。   On the optical path of the lens 10, LD4, and PD6, a WDM filter 8 that reflects the transmission light emitted from the LD4 and transmits the reception light is disposed at a predetermined inclination angle. The transmission light emitted from the emission part 4 a of the LD 4 is reflected by the WDM filter 8, collected by the lens 10, passed through the opening 12 a of the holder 12 and fixed to the sleeve member 13. And is sent to an external optical fiber transmission line. The received light transmitted from the external optical fiber transmission line is emitted from the optical fiber 13 a of the fiber stub 13, collected by the lens 10 through the opening 12 a of the holder 12, and transmitted through the WDM filter 8 for reception. Is received by PD6.

また、ＬＤ４の出射部４ａから出射された信号光の一部は、ＷＤＭフィルタ８で反射されてファイバスタブ１３の光ファイバ１３ａに入射されて外部に送信する以外に、ＷＤＭフィルタ８等をすり抜けたり透過したりして、外部に出射されずにキャップ１１内で反射を繰り返しながら減衰する迷光が生じる。このキャップ１１内で迷光となった光は、キャップ内に光吸収層等を設けることにより反射を抑制すると共に、ＰＤ６とＷＤＭフィルタ８との間に配されたカットフィルタ９により減衰させて、ＰＤ６の受光面６ａに受光するのを抑制している。このＰＤ６の受光面６ａに受光される迷光が少なければ少ないほど、光クロストークは低減させることができる。   Further, a part of the signal light emitted from the emission part 4a of the LD 4 is reflected by the WDM filter 8 and incident on the optical fiber 13a of the fiber stub 13 to be transmitted to the outside. Or stray light that attenuates while being repeatedly reflected in the cap 11 without being transmitted to the outside. The stray light in the cap 11 is prevented from reflecting by providing a light absorption layer or the like in the cap, and attenuated by the cut filter 9 disposed between the PD 6 and the WDM filter 8, so that the PD 6 The light receiving surface 6a is suppressed from receiving light. As the stray light received by the light receiving surface 6a of the PD 6 is reduced, the optical crosstalk can be reduced.

本発明においては、特に、図５で説明したＬＤ４の送信光のうち、ＬＤ４のＦＲＰの裾方向側のＰＤ６に近い光、すなわち、ＷＤＭフィルタ８への入射角が小さい光で、ＬＤ４の出射部４ａと受信用のＰＤ６の受光面６ａを結ぶ線上を通る光が、ＷＤＮフィルタ８とカットフィルタ９を透過して、受信用のＰＤ６で直接受光しないようにしている。このため、ＬＤ４が搭載されるヒートシンク５のＰＤ６側の少なくとも上面５ａを、突出幅（Ｄ）で示すように、受信用のＰＤ６方向に張り出るように形成する。   In the present invention, in particular, among the transmission light of the LD 4 described in FIG. 5, light close to the PD 6 on the skirt direction side of the FRP of the LD 4, that is, light having a small incident angle to the WDM filter 8, The light passing through the line connecting 4a and the light receiving surface 6a of the receiving PD 6 passes through the WDN filter 8 and the cut filter 9 and is not directly received by the receiving PD 6. For this reason, at least the upper surface 5a on the PD6 side of the heat sink 5 on which the LD4 is mounted is formed so as to protrude in the direction of the receiving PD6 as indicated by the protruding width (D).

図２に示すように、ＬＤ４の出射部４ａから出射され信号光のうち、ＷＤＭフィルタ８に小さい入射角（鋭角）で入射される光成分は、上述したヒートシンク５のＰＤ６側に張り出た上面５ａに当たって、上方に反射させることができる。これには、ＬＤ４の出射部４ａからの出射光が、ＰＤ６の受光面６ａを透視する範囲のラインＥを境として、ヒートシンク５寄り（矢印Ａ方向）の光成分は、全て上記のＰＤ６側に張り出た上面５ａにより遮って、ＷＤＭフィルタ８には当たらないようにする。この結果、ラインＥより矢印Ａ側の光成分は、ＷＤＭフィルタ８を透過せず、ＰＤ６の受光面６ａで直接受光することから防止される。   As shown in FIG. 2, of the signal light emitted from the emitting portion 4a of the LD 4, the light component incident on the WDM filter 8 at a small incident angle (acute angle) is the upper surface of the heat sink 5 that protrudes toward the PD 6 side. 5a can be reflected upward. For this purpose, all the light components near the heat sink 5 (in the direction of arrow A) are directed to the PD 6 side above the line E in the range where the emitted light from the light emitting portion 4a of the LD 4 is seen through the light receiving surface 6a of the PD 6. It is blocked by the protruding upper surface 5a so as not to hit the WDM filter 8. As a result, the light component on the arrow A side from the line E is prevented from being directly received by the light receiving surface 6a of the PD 6 without passing through the WDM filter 8.

なお、ＰＤ６の受光面６ａを透視する範囲のラインＥからレンズ１０寄り（矢印Ｂ方向）で、ＷＤＭフィルタ８を透過する光成分は、ＰＤ６の受光面６ａには直接には当たらずに迷光となる。この迷光は、ＷＤＭフィルタ８をすり抜けた迷光と同様に、キャップ内で反射を繰り返して減衰され、また、カットフィルタ９で吸収され、吸収し切れなかった迷光の一部がＰＤ６で受光される。しかしながら、ＬＤ４の出射部４ａから出射してＷＤＭフィルタ８およびカットフィルタ９を透過して直進した送信光は、ヒートシンク５の張り出た上面５ａで反射されるため、この光成分の受光を抑制することができる。   The light component transmitted through the WDM filter 8 near the lens 10 (in the direction of arrow B) from the line E in the range through which the light receiving surface 6a of the PD 6 is seen is not directly applied to the light receiving surface 6a of the PD 6 but stray light. Become. Similar to the stray light that has passed through the WDM filter 8, this stray light is repeatedly reflected and attenuated in the cap, is absorbed by the cut filter 9, and part of the stray light that has not been absorbed is received by the PD 6. However, since the transmitted light that has been emitted from the emitting portion 4a of the LD 4 and transmitted through the WDM filter 8 and the cut filter 9 is reflected by the upper surface 5a of the heat sink 5, the reception of this light component is suppressed. be able to.

ＯＬＴ側では、図６（Ｂ）で示したように、ＷＤＭフィルタ８の特性からラインＥよりＡ方向寄りの鋭角な入射角の光成分の透過率が大きいことから、この光成分をヒートシンク５の上面５ａで遮ることは、極めて有効である。なお、ＯＬＴ側では、図６（Ａ）で示したように、ＷＤＭフィルタ８の特性から、ラインＥより矢印Ａ方向寄りの鋭角な入射角の光成分の透過率が小さく、この光成分をＰＤ６で受光する量は微量であるが、更にその受光量を軽減することができる。   On the OLT side, as shown in FIG. 6B, the transmittance of the light component having an acute incident angle closer to the A direction than the line E is large due to the characteristics of the WDM filter 8. It is very effective to block the upper surface 5a. On the OLT side, as shown in FIG. 6A, due to the characteristics of the WDM filter 8, the transmittance of the light component having an acute incident angle closer to the arrow A direction than the line E is small, and this light component is converted into PD6. The amount of light received by is small, but the amount of received light can be further reduced.

図３は、ＯＬＴ側の光モジュールで、図４，５の従来品と図１，２の本発明品による光クロストークを測定した比較結果を示す図である。従来品においては、光クロストークが−３０（ｄＢ）〜−３４（ｄＢ）で、平均で−３３（ｄＢ）前後であったが、本発明品によれば、光クロストークが−４０（ｄＢ）〜−４６（ｄＢ）で、平均で−４５（ｄＢ）前後となり、光モジュールの受信性能を改善することができた。   FIG. 3 is a diagram showing a comparison result obtained by measuring optical crosstalk between the conventional product of FIGS. 4 and 5 and the product of the present invention of FIGS. In the conventional product, the optical crosstalk is -30 (dB) to -34 (dB), and is about -33 (dB) on average. However, according to the present invention, the optical crosstalk is -40 (dB). ) To -46 (dB), the average is around -45 (dB), and the reception performance of the optical module can be improved.

１…光モジュール、２…ステム、３…リード端子、４…発光素子（ＬＤ）、４ａ…出射部、５…ヒートシンク、５ａ…上面、６…受光素子（ＰＤ）、６ａ…受光面、７…サブマウント、８…ＷＤＭフィルタ、９…カットフィルタ、１０…レンズ、１１…キャップ、１２…ホルダ、１２ａ…開口、１３…ファイバスタブ、１３ａ…光ファイバ。 DESCRIPTION OF SYMBOLS 1 ... Optical module, 2 ... Stem, 3 ... Lead terminal, 4 ... Light emitting element (LD), 4a ... Output part, 5 ... Heat sink, 5a ... Upper surface, 6 ... Light receiving element (PD), 6a ... Light receiving surface, 7 ... Submount, 8 ... WDM filter, 9 ... cut filter, 10 ... lens, 11 ... cap, 12 ... holder, 12a ... opening, 13 ... fiber stub, 13a ... optical fiber.

Claims (3)

送信光を発光する発光素子と受信光を受信する受光素子、並びに、波長合分波フィルタを搭載したステム上に、光透過窓を有するキャップを封着した１パッケージ型の一心双方向光モジュールであって、
前記ステム上にヒートシンクを介して前記発光素子が実装され、サブマウントを介して前記受光素子が実装され、前記発光素子の出射光が前記受光素子の受光面を透視する範囲を、前記ヒートシンクが遮るように構成されていることを特徴とする一心双方向光モジュール。 A one-pack type single-fiber bidirectional optical module in which a cap having a light transmission window is sealed on a light-emitting element that emits transmission light, a light-receiving element that receives reception light, and a stem on which a wavelength multiplexing / demultiplexing filter is mounted. There,
The light emitting element is mounted on the stem via a heat sink, the light receiving element is mounted via a submount, and the heat sink blocks a range in which light emitted from the light emitting element is seen through the light receiving surface of the light receiving element. A one-fiber bidirectional optical module characterized by being configured as described above. 前記波長合分波フィルタと前記受光素子の間に、受信波長光の以外の波長光を吸収するカットフィルタが配されていることを特徴とする請求項１に記載の一心双方向光モジュール。   The single-fiber bidirectional optical module according to claim 1, wherein a cut filter that absorbs light having a wavelength other than received wavelength light is disposed between the wavelength multiplexing / demultiplexing filter and the light receiving element. 前記ヒートシンクは、送信波長光を透過しない材料で形成されていることを特徴とする請求項１または２に記載の一心双方向光モジュール。   The single-fiber bidirectional optical module according to claim 1 or 2, wherein the heat sink is made of a material that does not transmit light having a transmission wavelength.
JP2009002316A 2008-04-28 2009-01-08 Bidirectional optical module Pending JP2010161194A (en)

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