JPH0422245B2 - - Google Patents
Info
- Publication number
- JPH0422245B2 JPH0422245B2 JP21900882A JP21900882A JPH0422245B2 JP H0422245 B2 JPH0422245 B2 JP H0422245B2 JP 21900882 A JP21900882 A JP 21900882A JP 21900882 A JP21900882 A JP 21900882A JP H0422245 B2 JPH0422245 B2 JP H0422245B2
- Authority
- JP
- Japan
- Prior art keywords
- light
- mode light
- waveguides
- crystal
- mode
- 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.)
- Expired - Lifetime
Links
- 230000003287 optical effect Effects 0.000 claims description 28
- 239000013078 crystal Substances 0.000 claims description 20
- 239000000758 substrate Substances 0.000 claims description 11
- 229910013641 LiNbO 3 Inorganic materials 0.000 claims description 9
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 2
- 238000000926 separation method Methods 0.000 claims description 2
- 230000010287 polarization Effects 0.000 description 10
- 238000004891 communication Methods 0.000 description 4
- 239000010936 titanium Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 230000005684 electric field Effects 0.000 description 3
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000013307 optical fiber Substances 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
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
- G02F1/21—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 by interference
- G02F1/225—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 by interference in an optical waveguide structure
Landscapes
- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Integrated Circuits (AREA)
Description
【発明の詳細な説明】 (a) 発明の技術分野 本発明変調器の改良に関する。[Detailed description of the invention] (a) Technical field of the invention The present invention relates to improvements in the modulator.
(b) 技術の背景
半導体レーザ素子等を用いて光通信により入力
信号を伝達する際、入力信号の周波数の帯域巾を
広げて信号の伝達を高速に行うために光変調器が
用いられている。(b) Background of the technology When transmitting an input signal through optical communication using a semiconductor laser device, etc., an optical modulator is used to widen the frequency bandwidth of the input signal and transmit the signal at high speed. .
このような光変調器として例えばリチウムナイ
オベイト（LiNbO3）のような電気光学結晶の基
板にTi（チタン）等を細い線状に拡散して基板と
屈折率を変化せしめた光導波路が用いられてい
る。 As such an optical modulator, an optical waveguide is used, in which Ti (titanium) or the like is diffused into a thin line on an electro-optic crystal substrate such as lithium niobate (LiNbO 3 ) to change the refractive index with the substrate. ing.
このような光導波路を用いた光変調器は、小型
でかつ光が狭い導波路の領域内に閉じ込められる
ので、変調に要する電圧が低電圧で済む利点ある
ので光回路素子として広く用いられている。 Optical modulators using such optical waveguides are compact and the light is confined within the narrow waveguide area, so they have the advantage of requiring only a low voltage for modulation, and are therefore widely used as optical circuit elements. .
(c) 従来技術と問題点
このようなLiNbO3の結晶は電気光学効果が大
きく、また光信号を低損失で伝達できる導波路も
容易に形成できるが、結晶に屈折率の異方性があ
り、また導入される光の偏波面がTMモードある
いはTEモードのいずれかによつて、該結晶に電
界をかけた際の結晶の屈折率値の変動の度合が異
なるといつた即ち電気光学係数に差を生じるよう
になる。そのため、光変調器に導入される光の偏
光方向によつて光変調器より出力される信号が影
響を受ける欠点ある。(c) Prior art and problems Although such LiNbO 3 crystals have a large electro-optic effect and can easily form waveguides that can transmit optical signals with low loss, the crystal has anisotropy in the refractive index. Also, depending on whether the polarization plane of the introduced light is TM mode or TE mode, the degree of variation in the refractive index value of the crystal when an electric field is applied to the crystal differs, that is, the electro-optic coefficient It starts to make a difference. Therefore, there is a drawback that the signal output from the optical modulator is affected by the polarization direction of the light introduced into the optical modulator.
このようなLiNbO3を結晶基板として用いた導
波路型光変調器としてはLiNbO3基板上にTiを線
状に拡散して形成した二本の導波路上を近接して
配置し、この二本の導波路上にSiO2等の絶縁膜
を介して電極を形成し、この電極間に電圧を印加
して基板の屈折率を変動させ、導波路に導入され
た光を変調する方向性結合器やあるいは一本の導
波路を二方向に分岐せしめ、その分岐せしめた一
方の導波路上に絶縁膜を介して電極を形成し、こ
の電極に電圧を印加して導入された光を変調する
Mach−Zender型干渉計の如き変調素子があるが
これらはいずれも導入光の偏波面によつて基板に
電界をかけた際の屈折率の変動する割合が異なる
といつた偏光依存性がある欠点を生じる。 In a waveguide optical modulator using LiNbO 3 as a crystal substrate, two waveguides formed by linearly diffusing Ti on a LiNbO 3 substrate are placed close to each other. A directional coupler that forms electrodes on the waveguide via an insulating film such as SiO 2 and applies a voltage between the electrodes to vary the refractive index of the substrate and modulate the light introduced into the waveguide. A single waveguide is branched into two directions, an electrode is formed on one of the branched waveguides via an insulating film, and a voltage is applied to this electrode to modulate the introduced light.
There are modulation elements such as Mach-Zender interferometers, but they all have the disadvantage of polarization dependence, in which the rate of change in the refractive index when an electric field is applied to the substrate differs depending on the polarization plane of the introduced light. occurs.
そのため、このような偏光依存性を除去するた
め導波路型光変調器を形成するLiNbO3のような
電気光学結晶を切断する際に切断方向を考慮した
り、また電極の形状を変化したり、あるいは電極
に周期性を持たせる等、種々考慮したが、いずれ
も結晶の切断に手間がかかつたり、電極の形成に
時間がかかりすぎたり、また電極の形状が複雑に
なつたりして好ましくない。 Therefore, in order to eliminate such polarization dependence, it is necessary to consider the cutting direction when cutting the electro-optic crystal such as LiNbO 3 that forms the waveguide optical modulator, or to change the shape of the electrode. Alternatively, various considerations have been made, such as giving periodicity to the electrodes, but all of these methods are undesirable because cutting the crystal takes time, forming the electrodes takes too much time, and the shape of the electrodes becomes complicated. .
(d) 発明の目的
本発明は上述した問題点を除去するもので、電
気光学結晶を用いて導波路型光変調器を形成する
際、該変調器に導入される光の偏波面がTMモー
ドかTEモードかによつて該結晶に電界をかけた
際に結晶の屈折率の変動の度合いが変化しないよ
うな、すなわち導入光の偏光方向によつて光変調
器より出力される光信号が影響を受けないように
した新規な光変調器の提供目的とするものであ
る。(d) Purpose of the Invention The present invention is intended to eliminate the above-mentioned problems.When forming a waveguide type optical modulator using an electro-optic crystal, the polarization plane of light introduced into the modulator is set to TM mode. The degree of variation in the refractive index of the crystal does not change when an electric field is applied to the crystal depending on whether it is in TE mode or TE mode.In other words, the optical signal output from the optical modulator is affected by the polarization direction of the introduced light. The purpose of the present invention is to provide a novel optical modulator that is not subject to
(e) 発明の構成
かかる目的を達成するための本発明の光変調器
は、電気光学結晶基板上に二本の導波路を設け、
該導波路を交差させて、導入される光のTEモー
ド光、TMモード光の分離素子を形成し、次いで
前記二本の導波路を分岐させて前記結晶にTEモ
ード光、TMモード光を導入して変調させた際の
該結晶のそれぞれのモード光に対する電気光学常
数の値の比に対応する長さの電極を備えたマツハ
ツエンダー型変調素子を形成し、次いで前記分岐
した導波路を合流させてTEモード光とTMモー
ド光とを合流させる合流素子を形成したことを特
徴とするものである。(e) Structure of the Invention The optical modulator of the present invention for achieving the above object comprises two waveguides provided on an electro-optic crystal substrate,
The waveguides are crossed to form a separation element for TE mode light and TM mode light of the introduced light, and then the two waveguides are branched to introduce TE mode light and TM mode light into the crystal. A Matsuhatsu Ender-type modulation element is formed which has an electrode having a length corresponding to the ratio of the value of the electro-optic constant to each mode light of the crystal when modulated by the waveguide, and then the branched waveguides are merged. The present invention is characterized in that a merging element is formed for merging TE mode light and TM mode light.
(f) 発明の実施例
以下図面を用いて本発明の一実施例につき詳細
に説明する。第１図は本発明の光変調器の構造を
示す平面図、第２図はそのＡ−A′線に沿つた断
面図である。(f) Embodiment of the Invention An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view showing the structure of the optical modulator of the present invention, and FIG. 2 is a sectional view taken along the line A-A'.
図示するようにＣ軸方向に垂直に切断した
LiNbO3の結晶基板１上にTiを蒸着後、所定の深
さに拡散して２本の光導波路２，３を形成する。
この導波路はＢ点，Ｃ点で交差させるようにして
おきこのＢ点を含む部分を分岐素子、Ｃ点を含む
部分を合流素子とする。そして分岐点Ｂより合流
点Ｃ迄の間のそれぞれの導波路２，３は途中で２
Ａ，２Ｂおよび３Ａ，３Ｂのように分岐させる。 Cut perpendicular to the C-axis direction as shown
After Ti is deposited on a LiNbO 3 crystal substrate 1, it is diffused to a predetermined depth to form two optical waveguides 2 and 3.
This waveguide is made to intersect at points B and C, and the portion including point B is used as a branching element, and the portion including point C is used as a merging element. Then, each waveguide 2, 3 from the branching point B to the confluence point C has two waveguides on the way.
Branch as A, 2B and 3A, 3B.
次いで、この基板１上二酸化シリコン（SiO2）
膜等の絶縁膜４を形成してから分岐した導波路２
Ｂ，３Ｂ上に該絶縁膜４を介してアルミニウム
（Al）等を蒸着して電圧印加用電極５を形成し、
この電極と櫛の羽状に対向してアース用電極６を
形成する。 Next, silicon dioxide (SiO 2 ) is deposited on this substrate 1.
Waveguide 2 branched after forming an insulating film 4 such as a film
A voltage application electrode 5 is formed by vapor depositing aluminum (Al) or the like on B, 3B via the insulating film 4,
A grounding electrode 6 is formed opposite to this electrode in the shape of a comb.
そしてこの分岐した導波路２Ｂ上に形成されて
対向している電極５，６の長さｌは導波路３Ｂ上
に形成されて対向している電極５，６の長さl3に
比して約１／３の長さとしておく。 The length l of the electrodes 5 and 6 formed on the branched waveguide 2B and facing each other is compared to the length l 3 of the electrodes 5 and 6 formed on the waveguide 3B and facing each other. Leave it at about 1/3 of the length.
このように導波路２Ａ，２Ｂと対向部分がl1の
長さを有する５，６とを組としたMach−Zender
型導波路M1と導波路３Ａ，３Ｂと対向部分がl2
の長さを有する５，６とを組としたMach−
Zender型導波路M2とを形成する。 In this way, the Mach-Zender waveguides 2A and 2B and the waveguides 5 and 6 whose opposing portions have a length of l 1 are combined.
The part facing the type waveguide M1 and waveguides 3A and 3B is l2
Mach−, which is a pair of 5 and 6 with length
A Zender type waveguide M2 is formed.
このような変調器に例えばレーザ光源より光フ
アイバを介して光を導入する。このように光フア
イバを介して導入される光は、直線偏光の状態で
なく楕円偏光の状態となつており、この導入され
た光は分岐素子によつてTEモード光とTMモー
ド光に分離される。ここでTMモード光は直進し
て進みMach−Zender型導入路M2に導入され、
TMモード光は曲がつて進みMach−Zender型導
入路M1に導入される。そしてTEモード光は
Mach−Zender型導入路M2において対向部l2の長
さを有する電極５，６によつて変調を受け、TM
モード光はMach−Zender型導入路M1において
対向部がl1の長さを有する電極５，６によつて変
調を受ける。 Light is introduced into such a modulator from, for example, a laser light source via an optical fiber. In this way, the light introduced through the optical fiber is not in a linearly polarized state but in an elliptically polarized state, and this introduced light is separated into TE mode light and TM mode light by a branching element. Ru. Here, the TM mode light travels straight and is introduced into the Mach-Zender type introduction path M2 ,
The TM mode light travels in a curved manner and is introduced into the Mach-Zender type introduction path M1 . And the TE mode light is
Modulated by electrodes 5 and 6 having a length of opposing portions l 2 in the Mach-Zender type introduction path M 2 , TM
The mode light is modulated by electrodes 5 and 6 whose opposing portions have a length of l1 in the Mach-Zender introduction path M1 .
ここでＣ軸に垂直な平面で切断したLiNbO3の
結晶においては、TEモード光に対する電気光学
常数r13とTMモード光に対する電気光学常数r38
とは異なつており、r33≒3r13の関係を有している
のでl1とl2をl2／l1＝r33／r13≒３の長さになるよ
うに、つまりTEモード光が変調を受ける対向電
極の長さl2をTMカード光が変調を受ける対向電
極の長さl1の約３倍になるようにする。 Here, in a LiNbO 3 crystal cut along a plane perpendicular to the C-axis, the electro-optic constant r 13 for TE mode light and the electro-optic constant r 38 for TM mode light.
, and has the relationship r 33 ≒ 3r 13 , so we set l 1 and l 2 to the length l 2 /l 1 = r 33 /r 13 ≒ 3, that is, the TE mode light The length l2 of the opposing electrode on which the TM card light is modulated is set to be approximately three times the length l1 of the opposing electrode on which the TM card light is modulated.
この後さらに合流素子が変調をかけられたTM
モード光を曲げ、TEモード光を直進させること
で変調器の外部に両モードの合流した光を出力さ
せるようにする。 After this, the merging element is further modulated TM
By bending the mode light and making the TE mode light go straight, the combined light of both modes is output outside the modulator.
このようにすれば導入される光のTEモード、
TMモードの両方のモードの光によつて影響を受
けない偏光依存性のない光変調器が得られ、この
ような変調器を用いれば直線偏光の光だけでなく
楕円偏光の光でも偏光の依存性がなく変調ででき
るので、光通信システム等に用いて極めて効果的
である。 In this way, the TE mode of the light introduced,
It is possible to obtain a polarization-independent optical modulator that is unaffected by light in both modes of the TM mode, and by using such a modulator, polarization-independent light is not affected not only by linearly polarized light but also by elliptically polarized light. Since it can be done by modulation without any bias, it is extremely effective for use in optical communication systems, etc.
(g) 発明の効果
以上述べたように本発明の光変調器によれば導
入される光の偏波面の影響を受けない光変調器が
得られ、該変調器を光通信システム等に用いれば
高効率、高信頼度の光通信が出来る等効果が大で
ある。(g) Effects of the invention As described above, according to the optical modulator of the present invention, an optical modulator that is not affected by the polarization plane of introduced light can be obtained, and if the modulator is used in an optical communication system, etc. It has great effects, such as enabling highly efficient and highly reliable optical communications.
第１図は本発明の光変調器の構造を示す平面
図、第２図そのＡ−A′線に沿つた断面図である。
図において、１はLiNbO3基板、２，２Ａ，２
Ｂ，３，３Ａ，３Ｂは導波路、４は絶縁膜、５，
６は電極、M1，M2はMach−Zender型導波路、
Ｂ，Ｃは交差点、l1，l2は電極の長さを示す。
FIG. 1 is a plan view showing the structure of the optical modulator of the present invention, and FIG. 2 is a sectional view taken along the line A-A'. In the figure, 1 is a LiNbO 3 substrate, 2, 2A, 2
B, 3, 3A, 3B are waveguides, 4 is an insulating film, 5,
6 is an electrode, M 1 and M 2 are Mach-Zender type waveguides,
B and C indicate the intersection, and l 1 and l 2 indicate the lengths of the electrodes.
Claims (1)
該導波路を交差させて、導入される光のTEモー
ド光、TMモード光の分離素子を形成し、次いで
前記二本の導波路を分岐させて前記結晶にTEモ
ード光、TMモード光を導入して変調させた際の
該結晶のそれぞれのモード光に対する電気光学常
数の値の比に対応する長さの電極を備えたマツハ
ツエンダー型変調素子を形成し、次いで前記分岐
した導波路を合流させてTEモード光とTMモー
ド光とを合流させる合流素子を形成したことを特
徴とする光変調器。 ２ 前記電気光学結晶としてリチウムナイオベイ
ト（LiNbO3）を用いたことを特徴とする特許請
求範囲第１項に記載の光変調器。[Claims] 1. Two waveguides are provided on an electro-optic crystal substrate,
The waveguides are crossed to form a separation element for TE mode light and TM mode light of the introduced light, and then the two waveguides are branched to introduce TE mode light and TM mode light into the crystal. A Matsuhatsu Ender-type modulation element is formed which has an electrode having a length corresponding to the ratio of the value of the electro-optic constant to each mode light of the crystal when modulated by the waveguide, and then the branched waveguides are merged. An optical modulator characterized in that a merging element is formed for merging TE mode light and TM mode light. 2. The optical modulator according to claim 1, wherein lithium niobate (LiNbO 3 ) is used as the electro-optic crystal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21900882A JPS59107324A (en) | 1982-12-13 | 1982-12-13 | Optical modulator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21900882A JPS59107324A (en) | 1982-12-13 | 1982-12-13 | Optical modulator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS59107324A JPS59107324A (en) | 1984-06-21 |
| JPH0422245B2 true JPH0422245B2 (en) | 1992-04-16 |
Family
ID=16728809
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21900882A Granted JPS59107324A (en) | 1982-12-13 | 1982-12-13 | Optical modulator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS59107324A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8630959D0 (en) * | 1986-12-29 | 1987-02-04 | British Telecomm | Optical polarisation control |
| JPS644719A (en) * | 1987-06-29 | 1989-01-09 | Japan Broadcasting Corp | Optical modulator |
| JPH0980365A (en) * | 1995-09-19 | 1997-03-28 | Nec Corp | Waveguide type optical device |
| US5835212A (en) * | 1996-10-18 | 1998-11-10 | Uniphase Telecommunications Products, Inc. | Variable chirp optical modulator using single modulation source |
-
1982
- 1982-12-13 JP JP21900882A patent/JPS59107324A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS59107324A (en) | 1984-06-21 |
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