JPH05323248A - Tunable optical filter - Google Patents
Tunable optical filterInfo
- Publication number
- JPH05323248A JPH05323248A JP13290392A JP13290392A JPH05323248A JP H05323248 A JPH05323248 A JP H05323248A JP 13290392 A JP13290392 A JP 13290392A JP 13290392 A JP13290392 A JP 13290392A JP H05323248 A JPH05323248 A JP H05323248A
- Authority
- JP
- Japan
- Prior art keywords
- surface acoustic
- acoustic wave
- optical
- optical waveguide
- waveguide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/11—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves
- G02F1/125—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves in an optical waveguide structure
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- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
Abstract
Description
【0001】[0001]
【産業上の利用分野】本発明は、光波長多重伝送システ
ムあるいは光周波数多重伝送システムにおいて、任意の
波長(周波数)の光信号に対して合波および分波を行う
可同調光合分波器その他に利用される可同調光フィルタ
に関する。特に、音響光学(AO)効果を用いたTE−
TMモード変換型の光フィルタにおいて、表面弾性波の
周波数を変えることによって容易に位相整合を得ること
ができる可同調光フィルタに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunable optical multiplexer / demultiplexer for multiplexing and demultiplexing an optical signal of an arbitrary wavelength (frequency) in an optical wavelength multiplex transmission system or an optical frequency multiplex transmission system. The present invention relates to a tunable optical filter used in. In particular, TE-using the acousto-optic (AO) effect
The present invention relates to a tunable optical filter that can easily achieve phase matching in a TM mode conversion type optical filter by changing the frequency of a surface acoustic wave.
【0002】[0002]
【従来の技術】図7は、音響光学効果によるTE−TM
モード変換を用いた従来の可同調光フィルタの構成を示
す図である。2. Description of the Related Art FIG. 7 shows a TE-TM based on an acousto-optic effect.
It is a figure which shows the structure of the conventional tunable optical filter using mode conversion.
【0003】図において、誘電体基板であるLiNbO3
基板11の表面には、伝搬方向が光学軸(z軸)に垂直
になるようにチタン(Ti) を熱拡散した光導波路12
と、光導波路12を伝搬する光信号と同一直線上を進行
する表面弾性波を励起する直線電極13と、表面弾性波
を吸収する吸音材14とが形成される。さらに光導波路
12の前後に、入射光のうち特定方向の偏波のみを光導
波路12に結合する入射光用偏光子15と、光導波路1
2の出射光を偏波成分に応じて分離する出射光用偏光子
16とを配置して可同調光フィルタが構成される。In the figure, the dielectric substrate LiNbO 3
On the surface of the substrate 11, an optical waveguide 12 in which titanium (Ti) is thermally diffused so that the propagation direction is perpendicular to the optical axis (z axis).
A linear electrode 13 for exciting a surface acoustic wave traveling on the same straight line as the optical signal propagating through the optical waveguide 12 and a sound absorbing material 14 for absorbing the surface acoustic wave are formed. Further, before and after the optical waveguide 12, an incident light polarizer 15 that couples only the polarized light in a specific direction of the incident light to the optical waveguide 12, and the optical waveguide 1
The tunable optical filter is configured by arranging the outgoing light polarizer 16 for separating the outgoing light of 2 according to the polarization component.
【0004】光導波路12を伝搬する光信号と、直線電
極13により励起された表面弾性波とを同一直線上で進
行させると、表面弾性波による回折格子により屈折率楕
円体の主軸が変わる。これにより、誘電率テンソルに対
角要素が生じ、表面弾性波とTEモードおよびTMモー
ドの位相整合条件を満たす波長の光信号のみが選択的に
TE−TMモード変換を受ける。When the optical signal propagating through the optical waveguide 12 and the surface acoustic wave excited by the linear electrode 13 travel on the same straight line, the principal axis of the index ellipsoid is changed by the diffraction grating by the surface acoustic wave. As a result, a diagonal element is generated in the permittivity tensor, and only the optical signal having a wavelength satisfying the phase matching conditions of the surface acoustic wave and TE mode and TM mode is selectively subjected to TE-TM mode conversion.
【0005】この音響光学効果によるモード変換機能を
利用し、あらかじめ入射光の偏波方向を入射光用偏光子
15により揃えておき、出射光用偏光子16によりTE
モードあるいはTMモードのいずれか一方の偏波の光信
号を選択することにより、帯域通過フィルタあるいは帯
域阻止フィルタを構成することができる。この従来技術
については、文献(David A. Smith, Jane E. Baran, J
ohn J. Johonson andKwok-Wai Cheng, " Integrated-Op
tic Acoustically-Tunable Filter for WDMNetworks",
IEEE JOURNAL OF SELECTED AREAS IN COMUNICATIONS,
vol.8, No.6,pp1151-1159,1990) に記載がある。By utilizing the mode conversion function by the acousto-optic effect, the polarization direction of the incident light is preliminarily aligned by the incident light polarizer 15, and the outgoing light polarizer 16 is used for TE.
A bandpass filter or a bandstop filter can be constructed by selecting an optical signal of either polarization mode or TM mode. This prior art is described in the literature (David A. Smith, Jane E. Baran, J.
ohn J. Johonson and Kwok-Wai Cheng, "Integrated-Op
tic Acoustically-Tunable Filter for WDMNetworks ",
IEEE JOURNAL OF SELECTED AREAS IN COMUNICATIONS,
vol.8, No.6, pp1151-1159, 1990).
【0006】ここで、音響光学効果によるTE−TMモ
ード変換を用いた従来の可同調光フィルタにおける光信
号と表面弾性波の伝搬方向を図8に示す。TEモード,
TMモードの界分布E3 ,H3 は、それぞれの伝搬方向
の振幅の変化をAE(x1),AM(x1)とし、伝搬方向と垂
直方向の界分布をFE(x2,x3),FM(x2,x3)とし、光
信号の角周波数をωとし、それぞれの伝搬定数をβE,
βMとすると、Here, FIG. 8 shows propagation directions of an optical signal and a surface acoustic wave in a conventional tunable optical filter using TE-TM mode conversion by the acousto-optic effect. TE mode,
The TM mode field distributions E 3 and H 3 are defined as A E (x 1 ) and A M (x 1 ) respectively indicating changes in the amplitude in the propagation direction, and F E (x 2 ) in the field distribution in the propagation direction and the vertical direction. , x 3 ), F M (x 2 , x 3 ), the angular frequency of the optical signal is ω, and their propagation constants are β E ,
β M
【0007】[0007]
【数1】 [Equation 1]
【0008】と表すことができる。また、真空中の誘電
率をε0 とし、弾性光学定数をpE kjmn とし、電気光学
定数をrs kjmとし、表面弾性波の変位によって生じる歪
みをSmnとし、表面弾性波による電界をEa mとすると、
表面弾性波による誘電率テンソルの変位量δεilはIt can be expressed as Further, the permittivity in vacuum is ε 0 , the elastic optical constant is p E kjmn , the electro-optical constant is r s kjm , the strain caused by the displacement of the surface acoustic wave is S mn, and the electric field due to the surface acoustic wave is E If you say a m ,
The displacement δε il of the dielectric constant tensor due to surface acoustic waves is
【0009】[0009]
【数2】 [Equation 2]
【0010】となる。ここで、歪みSと表面弾性波によ
る電界Ea は、表面弾性波パワーの平方根に比例する。
TEモード,TMモードの各等価屈折率をNTE,NTMと
し、光の波長をλとし、光の波長λが1.55μmのときの
表面弾性波の波長をΛとし、波長λが1.55μmからの位
相不整合量をΔkとすると、位相整合条件は、[0010] Here, the strain S and the electric field E a due to the surface acoustic wave are proportional to the square root of the surface acoustic wave power.
The TE mode and TM mode equivalent refractive indices are N TE and N TM , the light wavelength is λ, the surface acoustic wave wavelength is Λ when the light wavelength λ is 1.55 μm, and the wavelength λ is 1.55 μm. If the amount of phase mismatch of is Δk, the phase matching condition is
【0011】[0011]
【数3】 [Equation 3]
【0012】となる。このとき、TEモードとTMモー
ドの結合モード方程式は、モード間の結合係数をCME,
CEMとすると、[0012] At this time, the coupling mode equation of the TE mode and the TM mode has the coupling coefficient between the modes as C ME ,
C EM
【0013】[0013]
【数4】 [Equation 4]
【0014】となる。モード間の結合係数CME,CEMと
TE−TMモード変換との関係は、[0014] The relationship between the coupling coefficients C ME and C EM between modes and the TE-TM mode conversion is
【0015】[0015]
【数5】 [Equation 5]
【0016】の関係がある。ここで、歪みSと表面弾性
波による電界Ea は、表面弾性波パワーの平方根に比例
するので、 (3)式、 (7)式の関係を用いると、モード間
の結合係数の伝搬方向の分布も、やはり表面弾性波パワ
ーの平方根に比例する関係となる。There is a relationship of Here, since the strain S and the electric field E a due to the surface acoustic wave are proportional to the square root of the surface acoustic wave power, using the relations of the equations (3) and (7), the propagation direction of the coupling coefficient between the modes is The distribution also has a relationship proportional to the square root of the surface acoustic wave power.
【0017】[0017]
【発明が解決しようとする課題】ところで、従来の直線
電極13は直線形状であり、表面弾性波と光の相互作用
領域における伝搬方向の表面弾性波パワー分布がほぼ一
定となっている。したがって、結合係数が相互作用領域
でほぼ一定となり定数とみなすことができる。このとき
のTE−TMモード変換効率(透過特性)ηは、相互作
用距離をLとすると、By the way, the conventional linear electrode 13 has a linear shape, and the surface acoustic wave power distribution in the propagation direction in the interaction area of the surface acoustic wave and light is substantially constant. Therefore, the coupling coefficient becomes almost constant in the interaction region and can be regarded as a constant. The TE-TM mode conversion efficiency (transmission characteristic) η at this time is given by the following formula:
【0018】[0018]
【数6】 [Equation 6]
【0019】となる。ここで、 (4)式よりΔkをλで表
し、これを (8)式に代入して得られるフィルタの透過特
性を図9に示す。図9において、横軸は光の中心波長1.
55μmからの偏差(nm)であり、縦軸はフィルタ透過
率(dB)である。なお、相互作用距離は20mmとした。It becomes Here, the transmission characteristic of the filter obtained by substituting Δk in equation (8) into equation (8) is shown in FIG. In Fig. 9, the horizontal axis represents the central wavelength of light 1.
It is the deviation (nm) from 55 μm, and the vertical axis is the filter transmittance (dB). The interaction distance was 20 mm.
【0020】音響光学効果によるTE−TMモード変換
を用いた可同調光フィルタは、他の可同調光フィルタに
比べて駆動電力が小さく、チューニング範囲が広いとい
う長所を有している。The tunable optical filter using the TE-TM mode conversion by the acousto-optic effect has the advantages that the driving power is smaller and the tuning range is wider than other tunable optical filters.
【0021】しかし、従来の可同調光フィルタは表面弾
性波を励起する直線電極13が直線形状であるので、図
9に示すように、中心波長を含む主透過領域(メインロ
ーブ)の両側に存在する副透過領域(サイドローブ)と
の差が9dB程度になっていた。すなわち、サイドローブ
の最大値がメインローブに比べて無視しえない大きさで
あり、異なる波長の光信号間のクロストークを増大さ
せ、波長多重通信における光信号の波長配置を著しく制
限する要因になっていた。However, in the conventional tunable optical filter, since the linear electrode 13 for exciting the surface acoustic wave has a linear shape, it exists on both sides of the main transmission region (main lobe) including the central wavelength, as shown in FIG. The difference with the sub-transmissive region (side lobe) is about 9 dB. In other words, the maximum value of the side lobe is not negligible compared to the main lobe, which increases crosstalk between optical signals of different wavelengths and is a factor that significantly limits the wavelength arrangement of optical signals in wavelength division multiplexing communication. Was becoming.
【0022】本発明は、音響光学効果によるTE−TM
モード変換を用いた可同調光フィルタにおいて、サイド
ローブを十分に抑圧することができる可同調光フィルタ
を提供することを目的とする。The present invention is a TE-TM based on the acousto-optic effect.
An object of the present invention is to provide a tunable optical filter that can sufficiently suppress side lobes in the tunable optical filter using mode conversion.
【0023】[0023]
【課題を解決するための手段】請求項1に記載の発明
は、誘電体基板に、光導波路と、光導波路を伝搬する光
信号と同一直線上を進行する表面弾性波を励起する電極
とを形成し、光導波路に入射させる光信号のうち、特定
方向の偏波のみを結合させる入射光用偏光子と、光導波
路の出射光を偏波成分に応じて分離する出射光用偏光子
とを備えた可同調光フィルタにおいて、電極は、光導波
路を伝搬する光信号と表面弾性波の相互作用領域におけ
る伝搬方向の結合係数を所定の関数で分布させる曲率半
径を有する湾曲形状とすることを特徴とする。According to a first aspect of the present invention, an optical waveguide and an electrode for exciting a surface acoustic wave traveling on the same straight line as an optical signal propagating in the optical waveguide are provided on a dielectric substrate. An incident light polarizer that couples only the polarized light in a specific direction among the optical signals that are formed and incident on the optical waveguide, and an outgoing light polarizer that separates the outgoing light of the optical waveguide according to the polarization component. In the provided tunable optical filter, the electrode has a curved shape having a radius of curvature that distributes a coupling coefficient in a propagation direction in an interaction region of an optical signal propagating through an optical waveguide and a surface acoustic wave with a predetermined function. And
【0024】請求項2に記載の発明は、請求項1に記載
の可同調光フィルタにおいて、光信号と表面弾性波の相
互作用領域内に表面弾性波を導波する表面弾性波用導波
路を備え、湾曲させた電極と表面弾性波用導波路とによ
り、相互作用領域における伝搬方向の結合係数を所定の
関数で分布させる構成であることを特徴とする。According to a second aspect of the present invention, in the tunable optical filter according to the first aspect, there is provided a surface acoustic wave waveguide for guiding the surface acoustic wave in an interaction region between the optical signal and the surface acoustic wave. The present invention is characterized in that the curved electrode and the surface acoustic wave waveguide are used to distribute the coupling coefficient in the propagation direction in the interaction region with a predetermined function.
【0025】[0025]
【作用】請求項1に記載の発明は、表面弾性波を励起す
る電極を所定の曲率半径を有する湾曲形状とすることに
より、表面弾性波と光信号との相互作用領域におけるT
E−TMモード変換の結合係数に適当な分布を与える。According to the first aspect of the present invention, the electrode for exciting the surface acoustic wave is formed into a curved shape having a predetermined radius of curvature so that T in the interaction area between the surface acoustic wave and the optical signal is increased.
An appropriate distribution is given to the coupling coefficient of E-TM mode conversion.
【0026】請求項2に記載の発明は、表面弾性波を励
起する電極を所定の曲率半径を有する湾曲形状とし、さ
らに収束させた表面弾性波を導波するための表面弾性波
用導波路を備えることにより、同様にして表面弾性波と
光信号との相互作用領域におけるTE−TMモード変換
の結合係数に適当な分布を与える。According to a second aspect of the present invention, an electrode for exciting a surface acoustic wave has a curved shape having a predetermined radius of curvature, and a surface acoustic wave waveguide for guiding the converged surface acoustic wave is provided. By including the same, an appropriate distribution is similarly given to the coupling coefficient of TE-TM mode conversion in the interaction region between the surface acoustic wave and the optical signal.
【0027】ここで、表面弾性波パワーの平方根に比例
する結合係数として、例えばガウス分布あるいはハミン
グ関数のような相互作用領域の両端で小さく、中央部で
大きくなるような分布を与えるように光導波路上の表面
弾性波パワーを関数分布させると、サイドローブを著し
く抑圧した良好な透過特性をもつ可同調光フィルタを実
現することができる。Here, as the coupling coefficient proportional to the square root of the surface acoustic wave power, the optical waveguide is provided so as to give a distribution such as a Gaussian distribution or a Hamming function that is small at both ends of the interaction region and large at the center. When the surface acoustic wave power on the road is functionally distributed, it is possible to realize a tunable optical filter having excellent transmission characteristics in which side lobes are significantly suppressed.
【0028】たとえば、図2に示すハミング関数を相互
作用領域の結合係数の分布として与えた可同調光フィル
タでは、 (5)式および (6)式に示す結合方程式(連立微
分方程式)を用いた数値解析によれば、図3に示すよう
な透過特性を実現することができる。この解析結果で
は、メインローブに対するサイドローブのフィルタ透過
率は−30dB程度低くなり、良好なフィルタ特性が実現さ
れることがわかる。For example, in the tunable optical filter in which the Hamming function shown in FIG. 2 is given as the distribution of the coupling coefficient in the interaction region, the coupling equations (simultaneous differential equations) shown in the equations (5) and (6) are used. According to the numerical analysis, the transmission characteristic as shown in FIG. 3 can be realized. From this analysis result, it can be seen that the filter transmittance of the side lobe with respect to the main lobe is reduced by about −30 dB, and good filter characteristics are realized.
【0029】結合係数をこのような関数分布にさせるに
は、表面弾性波を励起する電極を湾曲させ、また表面弾
性波の収束を高め、表面弾性波パワー分布を変化させる
ことにより実現される。In order to make the coupling coefficient have such a function distribution, the electrode for exciting the surface acoustic wave is curved, the convergence of the surface acoustic wave is enhanced, and the surface acoustic wave power distribution is changed.
【0030】[0030]
【実施例】図1は、請求項1に記載の発明の可同調光フ
ィルタの実施例構成を示す図である。FIG. 1 is a diagram showing the configuration of an embodiment of a tunable optical filter of the invention described in claim 1. In FIG.
【0031】図において、誘電体基板であるYcut のL
iNbO3 基板1の表面には、伝搬方向が光学軸(z軸)
に垂直になるようにチタン(Ti) を熱拡散した光導波路
2と、光導波路2を伝搬する光と同一直線上を進行する
表面弾性波を励起する湾曲電極3と、表面弾性波を吸収
する吸音材4とが形成される。さらに光導波路2の前後
に、入射光のうち特定方向の偏波のみを光導波路2に結
合する入射光用偏光子15と、光導波路2の出射光を偏
波成分に応じて分離する出射光用偏光子16とを配置し
て可同調光フィルタが構成される。In the figure, L of Ycut which is a dielectric substrate
On the surface of the iNbO 3 substrate 1, the propagation direction is the optical axis (z axis).
An optical waveguide 2 in which titanium (Ti) is thermally diffused so as to be perpendicular to, a curved electrode 3 that excites a surface acoustic wave traveling on the same straight line as the light propagating in the optical waveguide 2, and a surface acoustic wave is absorbed. The sound absorbing material 4 is formed. Further, before and after the optical waveguide 2, an incident light polarizer 15 that couples only the polarized light in a specific direction of the incident light to the optical waveguide 2, and an outgoing light that separates the outgoing light of the optical waveguide 2 according to the polarization component. The tunable optical filter is configured by arranging the polarizer 16 for use.
【0032】本実施例では、相互作用領域の長さ(電極
3から吸音材4までの距離)を20mmとし、湾曲電極3
の開口幅を 920μmとし、相互作用領域の中心に表面弾
性波が焦点を結ぶように曲率半径を10mmとした。In this embodiment, the length of the interaction area (distance from the electrode 3 to the sound absorbing material 4) is set to 20 mm, and the curved electrode 3
The opening width was set to 920 μm, and the radius of curvature was set to 10 mm so that the surface acoustic wave was focused on the center of the interaction region.
【0033】ここで、光導波路12,2上の各相互作用
領域において、従来の直線形状の直線電極13および本
実施例の湾曲電極3によって励起される表面弾性波のパ
ワー分布を図4に示す。実線は湾曲電極3による表面弾
性波パワーの分布を示し、破線は直線形状の直線電極1
3による表面弾性波パワーの分布を示す。FIG. 4 shows the power distribution of the surface acoustic wave excited by the conventional linear electrode 13 and the curved electrode 3 of this embodiment in each interaction region on the optical waveguides 12, 2. .. The solid line indicates the surface acoustic wave power distribution by the curved electrode 3, and the broken line indicates the linear electrode 1 having a linear shape.
3 shows the distribution of surface acoustic wave power according to No. 3.
【0034】結合係数は、ここに示す表面弾性波パワー
の分布の平方根に比例して分布し、図5に示すような透
過特性を得ることができる。図5において、横軸は光の
中心波長1.55μmからの偏差(nm)であり、縦軸はフ
ィルタ透過率(dB)である。なお、実線は湾曲電極3に
よる透過特性を示し、破線は直線電極13による従来の
透過特性(図9)を示す。ここに示すように、本実施例
によるサイドローブは従来構成に比べて8dB程度の抑圧
されていることがわかる。すなわち、本実施例の湾曲電
極3を用いて表面弾性波のパワー分布を制御することに
より、サイドローブを抑圧してクロストークの低い可同
調光フィルタを実現することができる。The coupling coefficient is distributed in proportion to the square root of the surface acoustic wave power distribution shown here, and a transmission characteristic as shown in FIG. 5 can be obtained. In FIG. 5, the horizontal axis represents the deviation (nm) from the central wavelength of light of 1.55 μm, and the vertical axis represents the filter transmittance (dB). The solid line shows the transmission characteristic of the curved electrode 3, and the broken line shows the conventional transmission characteristic of the linear electrode 13 (FIG. 9). As shown here, it is understood that the side lobe according to the present embodiment is suppressed by about 8 dB as compared with the conventional configuration. That is, by controlling the power distribution of the surface acoustic wave using the curved electrode 3 of the present embodiment, side lobes can be suppressed and a tunable optical filter with low crosstalk can be realized.
【0035】図6は、請求項2に記載の発明の可同調光
フィルタの実施例構成を示す図である。本実施例におい
て、LiNbO3 基板1、光導波路2、湾曲電極3、吸音
材4、入射光用偏光子15、出射光用偏光子16は、図
1に示す実施例構成と同様である。本実施例の特徴とす
るところは、湾曲電極3から励起される表面弾性波を閉
じ込める表面弾性波用導波路7を設ける構成にある。こ
の表面弾性波用導波路7は、例えばバッファ層としてS
iO2層を形成した上に金を蒸着することにより形成する
ことができる。また、表面弾性波の導波領域の外側に高
濃度のチタンを熱蒸着しても形成することができる。FIG. 6 is a diagram showing the construction of an embodiment of the tunable optical filter of the invention described in claim 2. In FIG. In this embodiment, the LiNbO 3 substrate 1, the optical waveguide 2, the curved electrode 3, the sound absorbing material 4, the incident light polarizer 15 and the outgoing light polarizer 16 are the same as those of the embodiment shown in FIG. The feature of this embodiment is that the surface acoustic wave waveguide 7 for confining the surface acoustic waves excited from the curved electrode 3 is provided. The surface acoustic wave waveguide 7 is formed of, for example, S as a buffer layer.
It can be formed by depositing gold on the io 2 layer. It can also be formed by thermally depositing high-concentration titanium outside the surface acoustic wave waveguide region.
【0036】この表面弾性波用導波路7を用いて収束さ
せた表面弾性波を導波させることにより、光導波路2を
伝搬する光信号に結合する表面弾性波の伝搬方向のパワ
ー分布を増加させ、相互作用領域内の結合係数の分布を
微細に制御することができる。すなわち、湾曲電極3か
ら励起される表面弾性波は、表面弾性波用導波路7に収
束して結合する。このとき、湾曲電極3の曲率半径と表
面弾性波用導波路7の形状を試行錯誤的に調整すること
により、結合係数の分布を所定の分布とすることができ
る。By guiding the surface acoustic wave converged by using the surface acoustic wave waveguide 7, the power distribution in the propagation direction of the surface acoustic wave coupled to the optical signal propagating in the optical waveguide 2 is increased. , The distribution of the coupling coefficient in the interaction region can be finely controlled. That is, the surface acoustic wave excited from the curved electrode 3 is converged and coupled to the surface acoustic wave waveguide 7. At this time, the distribution of the coupling coefficient can be set to a predetermined distribution by adjusting the radius of curvature of the curved electrode 3 and the shape of the surface acoustic wave waveguide 7 by trial and error.
【0037】[0037]
【発明の効果】以上説明したように本発明は、表面弾性
波を励起する電極を所定の曲率半径で湾曲させることに
より、容易に結合係数に分布をもたせ、フィルタ透過特
性におけるサイドローブを抑圧させることができる。ま
た、湾曲した電極と表面弾性波を収束させる表面弾性波
用導波路を組み合わせることにより、サイドローブの抑
圧効果を高めることができる。したがって、可同調光フ
ィルタにおいてクロストークを大幅に低減させることが
できる。As described above, according to the present invention, the electrode for exciting the surface acoustic wave is curved with a predetermined radius of curvature, so that the coupling coefficient is easily distributed and the side lobe in the filter transmission characteristic is suppressed. be able to. Further, by combining the curved electrode and the surface acoustic wave waveguide that converges the surface acoustic wave, the side lobe suppressing effect can be enhanced. Therefore, crosstalk can be significantly reduced in the tunable optical filter.
【図1】請求項1に記載の発明の可同調光フィルタの実
施例構成を示す図。FIG. 1 is a diagram showing a configuration of an embodiment of a tunable optical filter of the invention described in claim 1.
【図2】ハミング関数を相互作用領域の結合係数の分布
とした例を示す図。FIG. 2 is a diagram showing an example in which a Hamming function is a distribution of coupling coefficients in an interaction region.
【図3】図2の結合係数分布に対するフィルタ透過特性
を示す図。FIG. 3 is a diagram showing filter transmission characteristics with respect to the coupling coefficient distribution of FIG.
【図4】従来の直線電極および本実施例の湾曲電極によ
って励起される表面弾性波のパワー分布を示す図。FIG. 4 is a diagram showing a power distribution of surface acoustic waves excited by a conventional linear electrode and a curved electrode of the present embodiment.
【図5】図4の表面弾性波パワー分布に対するフィルタ
透過特性を示す図。5 is a diagram showing filter transmission characteristics with respect to the surface acoustic wave power distribution of FIG.
【図6】請求項2に記載の発明の可同調光フィルタの実
施例構成を示す図。FIG. 6 is a diagram showing a configuration of an embodiment of a tunable optical filter of the invention described in claim 2.
【図7】音響光学効果によるTE−TMモード変換を用
いた従来の可同調光フィルタの構成を示す図。FIG. 7 is a diagram showing a configuration of a conventional tunable optical filter using TE-TM mode conversion by an acousto-optic effect.
【図8】従来の可同調光フィルタにおける光信号と表面
弾性波の伝搬方向を示す図。FIG. 8 is a diagram showing propagation directions of an optical signal and a surface acoustic wave in a conventional tunable optical filter.
【図9】従来の可同調光フィルタのフィルタ透過特性を
示す図。FIG. 9 is a diagram showing filter transmission characteristics of a conventional tunable optical filter.
1 LiNbO3 基板 2 光導波路 3 湾曲電極 4 吸音材 7 表面弾性波用導波路 11 LiNbO3 基板 12 光導波路 13 直線電極 14 吸音材 15 入射光用偏光子 16 出射光用偏光子1 LiNbO 3 substrate 2 optical waveguide 3 curved electrode 4 sound absorbing material 7 surface acoustic wave waveguide 11 LiNbO 3 substrate 12 optical waveguide 13 linear electrode 14 sound absorbing material 15 incident light polarizer 16 outgoing light polarizer
Claims (2)
伝搬する光信号と同一直線上を進行する表面弾性波を励
起する電極とを形成し、 前記光導波路に入射させる光信号のうち、特定方向の偏
波のみを結合させる入射光用偏光子と、 前記光導波路の出射光を偏波成分に応じて分離する出射
光用偏光子とを備えた可同調光フィルタにおいて、 前記電極は、前記光導波路を伝搬する光信号と前記表面
弾性波の相互作用領域における伝搬方向の結合係数を所
定の関数で分布させる曲率半径を有する湾曲形状とする
ことを特徴とする可同調光フィルタ。1. A dielectric substrate is provided with an optical waveguide and an electrode for exciting a surface acoustic wave propagating on the same straight line as an optical signal propagating through the optical waveguide, and the optical signal is incident on the optical waveguide. A tunable optical filter including an incident light polarizer that couples only polarized light in a specific direction, and an outgoing light polarizer that separates outgoing light of the optical waveguide according to a polarization component, wherein the electrode is A tunable optical filter having a curved shape having a radius of curvature for distributing a coupling coefficient in a propagation direction in an interaction region of an optical signal propagating through the optical waveguide and the surface acoustic wave with a predetermined function.
いて、 光信号と表面弾性波の相互作用領域内に表面弾性波を導
波する表面弾性波用導波路を備え、 湾曲させた電極と前記表面弾性波用導波路とにより、前
記相互作用領域における伝搬方向の結合係数を所定の関
数で分布させる構成であることを特徴とする可同調光フ
ィルタ。2. The tunable optical filter according to claim 1, further comprising a surface acoustic wave waveguide that guides the surface acoustic wave in an interaction region between the optical signal and the surface acoustic wave, and a curved electrode. A tunable optical filter having a structure in which a coupling coefficient in a propagation direction in the interaction region is distributed by a predetermined function by the surface acoustic wave waveguide.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP13290392A JPH05323248A (en) | 1992-05-25 | 1992-05-25 | Tunable optical filter |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP13290392A JPH05323248A (en) | 1992-05-25 | 1992-05-25 | Tunable optical filter |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH05323248A true JPH05323248A (en) | 1993-12-07 |
Family
ID=15092239
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP13290392A Pending JPH05323248A (en) | 1992-05-25 | 1992-05-25 | Tunable optical filter |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH05323248A (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH07270735A (en) * | 1994-04-01 | 1995-10-20 | Nec Corp | Acousto-optical filter |
US5677971A (en) * | 1994-08-26 | 1997-10-14 | Oki Electric Industry Co., Ltd. | Optical wavelength filter with reduced sidelobes and simple design |
US5991472A (en) * | 1996-12-19 | 1999-11-23 | Nec Corporation | Optical wavelength filter |
US6400881B1 (en) | 1997-08-11 | 2002-06-04 | Fujitsu Limited | Optical device having thin film formed over optical waveguide |
WO2008041448A1 (en) * | 2006-10-04 | 2008-04-10 | Murata Manufacturing Co., Ltd. | Acoustooptical filter |
-
1992
- 1992-05-25 JP JP13290392A patent/JPH05323248A/en active Pending
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH07270735A (en) * | 1994-04-01 | 1995-10-20 | Nec Corp | Acousto-optical filter |
US5677971A (en) * | 1994-08-26 | 1997-10-14 | Oki Electric Industry Co., Ltd. | Optical wavelength filter with reduced sidelobes and simple design |
US5991472A (en) * | 1996-12-19 | 1999-11-23 | Nec Corporation | Optical wavelength filter |
US6400881B1 (en) | 1997-08-11 | 2002-06-04 | Fujitsu Limited | Optical device having thin film formed over optical waveguide |
WO2008041448A1 (en) * | 2006-10-04 | 2008-04-10 | Murata Manufacturing Co., Ltd. | Acoustooptical filter |
US8036499B2 (en) | 2006-10-04 | 2011-10-11 | Murata Manufacturing Co., Ltd. | Acousto-optic filter |
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