JPS62133423A - Phase modulator for optical circuit - Google Patents

Abstract

PURPOSE:To obtain an optical fiber type phase modulator free from the shift of its optical axis, extremely reduced at its insertion loss, capable of low voltage driving, having rapid responsibility, and remarkably reduced at the size of a transmission circuit by arranging an extremely small PLZT chip having a specific shape in a optical fiber in a specific direction. CONSTITUTION:A groove part 4 formed on an optical fiber 1 is a groove forming the shape of a cut part like a shape as shown in the figure by cutting one side of a clad part 2 from its periphery and leaving a part of the other side of the clad part 2 as it is so that the bottom of the groove becomes plane. A rectangular PLZT 5 arranging electrodes 6, 7 on its opposed main surface is engaged with the groove part 4 so that the height (h) in the direction between the electrodes 6, 7 is set up to the vertical direction, the electrode 7 is abutted upon the bottom of the groove part 4 and the thickness (d) direction is set up to the axial direction of a core 3 to constitute the phase modulator of the optical fiber 1 and the PLZT 5 in the groove part 4. The abutting surface of the PLZT 5 upon the core 3 has the area of hXw and constitutes an abutting surface sufficient for covering the whole sectional area of the core 4 and an electric field rectangular to the axial direction of the core 3 is formed.

Description

【発明の詳細な説明】 利用産業分野 この発明は、光通信分野において、光伝送路の入力光を
遮断、選択、切換、変調するために用いられる光学回路
用位相変調器に係り、光フアイバー内にＰＬＺＴを配置
した構成で、光フアイバー伝送の小型高性能化に最も適
した構成からなり、例えば、光スィッチにおける低電圧
駆動、切換速度の高速化２機器の小型化を可能にする光
学回路用位相変調器に関する。DETAILED DESCRIPTION OF THE INVENTION Field of Application This invention relates to a phase modulator for optical circuits used in the field of optical communications to block, select, switch, and modulate input light of an optical transmission line. PLZT is placed in the configuration, making it the most suitable configuration for miniaturizing and increasing the performance of optical fiber transmission. Regarding phase modulators.

背景技術 光通信における光伝送回路は、光フアイバー伝送が主流
で、伝送回路の諸特性は該伝送回路中に必要不可欠であ
る光スィッチの構成及び性能に大きく左右されることか
ら、光スィッチの構成に関する種々の開発が進められて
いる。BACKGROUND TECHNOLOGY Optical fiber transmission is the mainstream for optical transmission circuits in optical communications, and the various characteristics of the transmission circuit are greatly influenced by the configuration and performance of the optical switch, which is essential in the transmission circuit. Various developments related to this are underway.

現在、光スィッチとして、光ファイバーやプリズムを機
械的に動かして回路を切換構成からなる可動部を有する
機械式光スィッチが実用化されているが、切換速度が低
い上、振動等に弱い問題があった。Currently, mechanical optical switches that have a movable part that switches circuits by mechanically moving optical fibers or prisms are in practical use, but they have problems such as slow switching speed and vulnerability to vibrations. Ta.

このため、機械的可動部を有せず、位相変調器に電気光
学効果を利用した、例えば、ＬＬＮｂＯｚ先導波路を用
いた光スィッチが提案されており、高速切換が可能であ
るが、挿入損失が大きく、また、製造が困難であるなど
の問題を有していた。For this reason, optical switches have been proposed that do not have mechanically movable parts and utilize electro-optic effects in phase modulators, such as those using LLNbOz leading waveguides, which are capable of high-speed switching, but have low insertion loss. They had problems such as being large and difficult to manufacture.

さらに、可動部を有しな（＞光スイッチとして、入力光
をビームスプリッタと全反則プリズムで構成した偏光分
離器に入射させ、分波光を各々溝型電極を形成したＰＬ
ＺＴに入射させ、通過光をビ−ムスプリツタと全反射プ
リズムで構成した偏光合成器を通して出射させる構成で
、該溝型電極に与える電圧信号でスイッチングを行なう
光スィッチが提案（特開昭６０−３９６３０号）されて
いる。Furthermore, as an optical switch that does not have a movable part, the input light is made incident on a polarization separator composed of a beam splitter and a total refraction prism, and the demultiplexed light is sent to a PL with a groove-shaped electrode formed on each.
An optical switch has been proposed in which the light is incident on a ZT and the transmitted light is emitted through a polarization combiner composed of a beam splitter and a total reflection prism, and switching is performed by a voltage signal applied to the groove-shaped electrode (Japanese Patent Laid-Open No. 60-39630). No.) has been done.

上記の光スィッチは、駆動電圧８０〜１００Ｖ、切換速
度１μｓ　　（Ｉ　ＨＩ３　）　、挿入損失１．４ｄＢ
の高特性が得られるとしているが、光ファイバーを出た
光が、レンズ、偏光分離器、位相変調器となるＰＬＺＴ
、ｍＩ光合成器、レンズを通過して、再び光ファイバー
に入る構成であるため、スイッチ構成素子の配置が複雑
であり、光は各素子間で空気中を通過することになり、
挿入損失も多く、ざらには、複雑な溝型電極を有するＰ
ＬＺＴを用いるなど、光伝送回路構成の簡素化、小型化
には不向きであるとともに、今後、要求されるスイッチ
ング速度の超高速化には対応できない問題を有している
。The above optical switch has a driving voltage of 80 to 100 V, a switching speed of 1 μs (I HI3), and an insertion loss of 1.4 dB.
PLZT is said to provide high characteristics, but the light exiting the optical fiber is used as a lens, polarization separator, and phase modulator.
, an mI light combiner, and a lens before entering the optical fiber again, so the arrangement of the switch components is complicated, and the light passes through the air between each element.
P has a high insertion loss and has a complex groove-shaped electrode.
It is not suitable for simplifying and downsizing the optical transmission circuit configuration, such as by using LZT, and has the problem of not being able to meet the ultra-high switching speeds that will be required in the future.

上述の如く、従来の光学回路素子は、いずれも伝送媒体
である光ファイバーよりもはるかに大型であり、かつ、
素子の配置に際して、伝送回路中の光ファイバーを分断
し装入する必要があり、分断に伴なう挿入損失の増大化
は不可避であった。As mentioned above, all conventional optical circuit elements are much larger than the optical fiber that is the transmission medium, and
When arranging the elements, it is necessary to cut and insert the optical fiber in the transmission circuit, and an increase in insertion loss due to the cutting is unavoidable.

そこで、光フアイバー伝送用の光学回路素子として究極
的な形態であるファイバー型の位相変調器の開発が望ま
れていた。Therefore, it has been desired to develop a fiber-type phase modulator, which is the ultimate form of optical circuit element for optical fiber transmission.

発明の目的 この発明は、光通信の光伝送回路に不可欠な光学回路用
位相変調器を目的とし、また、光スィッチを構成した際
のスイッチング速度を高速度化するのに必要な高速応答
性を有する位相変調器を目的とし、さらには、光フアイ
バー伝送において、伝送回路簡素化と小型化に最も適し
たファイバー型の位相変調器を目的としている。Purpose of the Invention The present invention aims to provide a phase modulator for optical circuits which is essential for optical transmission circuits in optical communications, and also to provide high-speed response necessary for increasing the switching speed when configuring an optical switch. Furthermore, the present invention aims at a fiber-type phase modulator that is most suitable for simplifying and downsizing transmission circuits in optical fiber transmission.

発明の構成 この発明は、高速応答性を有する位相変調器を目的に種
々検討した結果、Ｌ＝ＮｂＯ３等の電気光学材料に比べ
てはるかに電気光学効果の高いＰＬＺＴ（Ｐｂ、　Ｌａ
、　”ｌｒ、　ＴＬの各酸化物を主成分とする透明高密
度磁器からなる電気光学材料）に着目し、特定形状から
なるＰＬＺＴの極少片を光フアイバー内に特定方向に配
置することにより、光軸ずれが・なく、挿入損失が極め
て小さく、低電圧駆動が可能で高速応答性を有し、伝送
回路を著しく小型化できる光フアイバー型位相変調器が
得られることを知見したものである。Structure of the Invention As a result of various studies aimed at creating a phase modulator with high-speed response, the present invention has developed PLZT (Pb, La
By focusing on an electro-optical material made of transparent high-density porcelain whose main components are oxides of PLZT, ``lr, and TL'', we have developed an optical fiber that can be It has been discovered that an optical fiber phase modulator can be obtained that has no axis misalignment, has extremely low insertion loss, can be driven at low voltage, has high-speed response, and can significantly reduce the size of the transmission circuit.

すなわち、この発明は、所要路ｍ間を寸断された光ファ
イバーのコア間に、少なくともコア全断面積に当接して
該寸断コア間を接続するＰＬＺＴを配置した構成からな
り、前記ＰＬＺＴの電界方向をコアの軸線方向と直交方
向に配したことを特徴とする光学回路用位相変調器であ
る。That is, the present invention has a configuration in which a PLZT is arranged between the cores of an optical fiber whose required path m is cut, and connects the cut cores by contacting at least the entire cross-sectional area of the core, and the direction of the electric field of the PLZT is This is a phase modulator for an optical circuit, characterized in that it is arranged in a direction orthogonal to the axial direction of the core.

発明の好ましい実施態様 この発明による位相変調器は、ファイバー型を特徴とし
、ＰＬＺＴは回折制限を受けない寸法で、コアを切断し
、径方向にクラッドを一部残して、軸方向に所要幅の溝
を切り、溝内に配置するのが望ましいが、一対の光フア
イバ一端面間に当接配置することもでき、光ファイバ一
種を選定することで、シングルモード用、マルチモード
用ともなる。Preferred Embodiment of the Invention The phase modulator according to the present invention is characterized by a fiber type, in which the PLZT is cut into a core with dimensions that are not subject to diffraction limitations, leaving a portion of the cladding in the radial direction, and having the required width in the axial direction. Although it is preferable to cut a groove and place it within the groove, it is also possible to place the optical fibers in contact between one end face of a pair of optical fibers, and by selecting one type of optical fiber, it can be used for single mode or multimode.

この発明に用いるＰＬＺＴは、光ファイバ一種。PLZT used in this invention is a type of optical fiber.

コア及びクラッド寸法、及び入射光の波長、駆動電圧等
を考慮して、その形状・寸法を適宜選定するが、ＰＬＺ
Ｔがコアの全断面積を覆って当接する必要があり、また
、このＰＬＺＴ内を通過する光に電気光学効果を作用さ
せるため、電界方向をコアの軸線方向に直交するように
形成する必要があり、該ＰＬＺＴの外表面に形成する電
極を、コア当接面以外の対向位置にある一対の面に形成
するほか、コア当接面を３分割して、コアとの接合部面
を挟む２面を一方とする一対の電極を配置するのもよく
、この電極間距離、すなわち、電界方向の長さを必要以
上に大きくすることは、駆動電圧を増大させるため、Ｐ
ＬＺＴが光ファイバーよりはみださない程度の寸法が望
ましい。The shape and dimensions are selected appropriately taking into consideration the core and cladding dimensions, the wavelength of the incident light, the driving voltage, etc., but PLZ
The T needs to cover the entire cross-sectional area of the core and come into contact with it, and in order to produce an electro-optic effect on the light passing through the PLZT, it is necessary to form the electric field so that the direction is perpendicular to the axial direction of the core. In addition to forming the electrodes on the outer surface of the PLZT on a pair of surfaces opposite to each other other than the core contact surface, the core contact surface is divided into three parts, and two electrodes are formed on the outer surface of the PLZT. It is also a good idea to arrange a pair of electrodes with one side facing the other. If the distance between the electrodes, that is, the length in the electric field direction, is made larger than necessary, the driving voltage will increase, so P
It is desirable that the dimensions are such that the LZT does not protrude from the optical fiber.

発明の図面に基づく開示 第１図は、この発明による位相変調器の斜視説明図であ
る。DISCLOSURE OF THE INVENTION BASED ON DRAWINGS FIG. 1 is a perspective explanatory diagram of a phase modulator according to the present invention.

光ファイバー（１）は、外径Ｄ１のクラッド部（２）の
軸心部に、外径Ｄ２なるコア部（３）を同心状に配した
構成からなる。The optical fiber (1) has a core part (3) having an outer diameter D2 concentrically disposed at the axial center of a cladding part (2) having an outer diameter D1.

光ファイバー（１）に設けた溝部（４）は、クラッド部
（２）の一方外周よりコア部（３）を切断し、他方側の
クラッド部（２）を一部残し、溝底面が平面となるよう
、切除部の形状が所謂蒲鉾状となった溝である。The groove part (4) provided in the optical fiber (1) cuts the core part (3) from the outer periphery of one side of the cladding part (2), leaving a part of the cladding part (2) on the other side, and the bottom surface of the groove becomes flat. The cutout is a so-called semicylindrical groove.

この溝部（４）に、対向する主面に電極（６Ｘ７）を設
しプた直方体状のＰＬＺＴ（５）を嵌入配置するが、溝
部（４）幅方向をＰ　Ｌ　Ｚ　Ｔ（５）の厚み（ｄ）、
電極（６Ｘ７）開方向を高さくｈ）９幅を（Ｗ＞として
、電極（６Ｘ７）　　。A rectangular parallelepiped-shaped PLZT (5) with electrodes (6 x 7) provided on the opposing main surfaces is fitted into this groove (4), but the width direction of the groove (4) is the thickness of PLZT (5). (d),
Electrode (6X7) The height in the opening direction is h)9, and the width is (W>).

開方向の高さくｈ）を図面の上下方向にし、一方電極（
７）を溝部（４）底面に当接させ、厚み（ｄ）方向をコ
ア（３）軸線方向として配置してあり、光ファイバー（
１）と溝部（４）のＰＬＺＴ（５）とで、この発明によ
る位相変調器を構成している。The height h) in the opening direction is in the vertical direction of the drawing, and one electrode (
7) is placed in contact with the bottom surface of the groove (4), and the thickness (d) direction is the axial direction of the core (3).
1) and the PLZT (5) in the groove (4) constitute a phase modulator according to the present invention.

このＰ　Ｌ　Ｚ　Ｔ（５）のコア（３）との当接面は、
ｈｘｗの面積であり、コア（４）の全断面積を覆うのに
充分な当接面を有し、また、コア（４）の軸線方向に直
交方向の電界を形成する。The contact surface of this P L Z T (5) with the core (3) is
It has an area of hxw, has a contact surface sufficient to cover the entire cross-sectional area of the core (4), and forms an electric field in a direction perpendicular to the axial direction of the core (4).

以上の構成からなるこの発明の位相変調器において、Ｐ
　Ｌ　Ｚ　Ｔ（５）の厚み（ｄ）が、ＰＬＺＴの回折損
失に大ぎく影響を及ぼすことに着目し、Ｐ［ＺＴの厚み
（ｄ）と回折損失との関係を調べた。In the phase modulator of the present invention having the above configuration, P
Focusing on the fact that the thickness (d) of L Z T (5) greatly affects the diffraction loss of PLZT, the relationship between the thickness (d) of P[ZT and the diffraction loss was investigated.

コア径１０．ｃａｎのシングルモード光ファイバーに、
波長λ＝　０．７８　ｌｉｍ、λ＝１．２９．ａｍの半
導体レーザーを入射し、屈折率ｎ＝２．５のＰＬＺＴに
おけるＰＬＺＴ厚み（ｄ）と回折損失との関係を調べた
ところ、第２図のグラフを得た。Core diameter 10. can's single mode optical fiber,
Wavelength λ=0.78 lim, λ=1.29. When the relationship between the PLZT thickness (d) and the diffraction loss in PLZT with a refractive index n=2.5 was investigated by inputting an am semiconductor laser, the graph shown in FIG. 2 was obtained.

この発明による位相変調器を用いて、光スィッチ等を構
成した際に、光学回路における挿入損失をより少なくす
る目的から、λ＝０．７８ｍ＋の半導体レーザーを入射
する場合、該回折損失を１ｄＢ以下とするには、厚み（
ｄ）を９０ＪＪｍ以下とする必要があることが分る。When configuring an optical switch or the like using the phase modulator according to the present invention, in order to reduce the insertion loss in the optical circuit, when a semiconductor laser of λ = 0.78 m+ is input, the diffraction loss should be 1 dB or less. To make it, the thickness (
It can be seen that d) needs to be 90 JJm or less.

実施例 上述した第１図の構成からなる位相変調器を、外径Ｄ＋
　＝　１２５．ｉｍ、コア外径Ｄ２　＝１０．ｇｍのシ
ングルモード光ファイバーに、厚みｄ＝５０１ｉｍ、幅
Ｗ＝２０、ｕｍ、高ざｈ＝２０．ｉｚｍのＰＬＺＴを用
いて作製し、その−万端面に、ＰＬＺＴの電界方向に対
して４５°の偏波面を有する波長λ＝０．７８βｍの半
導体レーザーの光源を配し、他方端に、該半導体レーザ
ーの偏波面とざらに９０”位相のずれた偏波面のみを透
過させる偏光子を具備する検出器を配置して、光スィッ
チを構成した。Example A phase modulator having the configuration shown in FIG.
= 125. im, core outer diameter D2 = 10. gm single mode optical fiber, thickness d=501im, width W=20, um, height h=20. A light source of a semiconductor laser having a wavelength λ = 0.78βm and having a polarization plane of 45° with respect to the electric field direction of PLZT is placed on one end of the semiconductor laser. An optical switch was constructed by arranging a detector equipped with a polarizer that transmits only a polarized wave plane that is roughly 90 inches out of phase with the polarized wave plane of the laser.

上記ＰＬＺＴの電極に、駆動電圧として半波長電圧を印
加したところ、駆動電圧２０Ｖにて、スイッチング速度
０．１μｓ１挿入損失１．０ｄＢの特性を得た。When a half-wavelength voltage was applied as a driving voltage to the PLZT electrode, characteristics of a switching speed of 0.1 μs and an insertion loss of 1.0 dB were obtained at a driving voltage of 20 V.

ちなみに、上記ＰＬＺＴと同寸法のＬＬＦＪｂ０３を用
いて、従来の光スィッチを構成したところ、その駆動電
圧は本発明に比べて５０〜１００倍となり、実用的でな
い。Incidentally, when a conventional optical switch is constructed using LLFJb03 having the same dimensions as the PLZT described above, its driving voltage is 50 to 100 times higher than that of the present invention, which is not practical.

発明の効果 この発明による位相変調器は、光ファイバーに極少のＰ
ＬＺＴを埋め込んだ極めて簡単な構成からなり、低電圧
駆動でき、高速応答性にすぐれ、光スィッチを構成した
際のスイッチング速度が著しく速くなり、理論上では１
ｎＳの超高速スイッチングが可能となる。また、光フア
イバー伝送において、伝送回路簡素化と小型化に最も適
したファイバー型であり、！Ａ造が容易で、他の光学回
路素子との組み合せも容易になり、汎用性の高い位相変
調器である。Effects of the Invention The phase modulator according to the present invention has a very small amount of P in the optical fiber.
It has an extremely simple configuration with embedded LZT, can be driven at low voltage, has excellent high-speed response, and has a significantly faster switching speed when configured as an optical switch.
Ultra high-speed switching of nS is possible. In addition, in optical fiber transmission, it is the most suitable fiber type for simplifying and downsizing the transmission circuit. It is a highly versatile phase modulator that can be easily assembled and combined with other optical circuit elements.

【図面の簡単な説明】[Brief explanation of drawings]

第１図はこの発明による位相変調器の斜視説明図である
。第２図はＰＬＺＴ厚みｄと回折損失との関係を示すグ
ラフである。 １・・・光ファイバー、２・・・クラッド部、３・・・
コア部、４・・・溝部、５・・・ＰＬＺＴ、６，７・・
・電極。 回折損失（ｄＢ）FIG. 1 is a perspective explanatory diagram of a phase modulator according to the present invention. FIG. 2 is a graph showing the relationship between PLZT thickness d and diffraction loss. 1... Optical fiber, 2... Clad part, 3...
Core part, 4...Groove part, 5...PLZT, 6,7...
·electrode. Diffraction loss (dB)

Claims (1)

【特許請求の範囲】[Claims] １　所要距離間を寸断された光ファイバーのコア間に、
少なくともコア全断面積に当接して該寸断コア間を接続
するＰＬＺＴを配置した構成からなり、前記ＰＬＺＴの
電界方向をコアの軸線方向と直交方向に配したことを特
徴とする光学回路用位相変調器。1 Between the cores of optical fibers that have been cut over the required distance,
A phase modulation method for an optical circuit comprising a structure in which a PLZT is arranged to contact at least the entire cross-sectional area of the core and connect the shredded cores, and the electric field direction of the PLZT is arranged in a direction orthogonal to the axial direction of the core. vessel.