JP5193585B2 - Optical waveguide type chromatic dispersion compensation device and manufacturing method thereof - Google Patents

Optical waveguide type chromatic dispersion compensation device and manufacturing method thereof Download PDF

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JP5193585B2
JP5193585B2 JP2007331005A JP2007331005A JP5193585B2 JP 5193585 B2 JP5193585 B2 JP 5193585B2 JP 2007331005 A JP2007331005 A JP 2007331005A JP 2007331005 A JP2007331005 A JP 2007331005A JP 5193585 B2 JP5193585 B2 JP 5193585B2
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optical waveguide
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dispersion compensation
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refractive index
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JP2009151240A (en
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寧 官
憲介 小川
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Fujikura Ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
    • G02B6/29392—Controlling dispersion
    • G02B6/29394—Compensating wavelength dispersion
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/13—Integrated optical circuits characterised by the manufacturing method
    • G02B6/132—Integrated optical circuits characterised by the manufacturing method by deposition of thin films
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
    • G02B6/29316—Light guides comprising a diffractive element, e.g. grating in or on the light guide such that diffracted light is confined in the light guide
    • G02B6/29317—Light guides of the optical fibre type
    • G02B6/29322—Diffractive elements of the tunable type

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  • Dispersion Chemistry (AREA)
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Description

本発明は、光ファイバの波長分散を補償する小型の光導波路型波長分散補償デバイスに関する。このデバイスは、光ファイバ通信網などに使用することができる。   The present invention relates to a compact optical waveguide type chromatic dispersion compensation device that compensates for chromatic dispersion of an optical fiber. This device can be used for an optical fiber communication network or the like.

光通信において、高密度波長多重（ＤＷＤＭ：Dense Wavelength-Division Multiplexing）伝送の広帯域化・高速化が急速に進められている。高速伝送を行うためには、これらの伝送線路として、伝送帯域で波長分散ができるだけ小さく、一方で非線形効果を抑制するために波長分散が零にはならない光ファイバを用いることが望ましい。また、既に広範囲に敷設されている光ファイバにおいて、分散が大きい波長領域で使われることが多い。例えば、波長１．３μｍ付近で零分散を有する標準シングルモードファイバ（Ｓ−ＳＭＦ：Standard Single-Mode Fiber）は、エルビウム添加光ファイバ増幅器が実用化されたことにより、波長１．５３〜１．６３μｍ帯で使われる。また、零分散を波長１．５５μｍ付近にシフトさせた分散シフトファイバ（ＤＳＦ：Dispersion Shifted Fiber）は、Ｃバンドだけでなく、ＳバンドやＬバンドで使われることがある。その他、波長１．５５μｍでゼロ分散にならない各種ノンゼロ分散シフトファイバ（ＮＺ−ＤＳＦ：Non-Zero Dispersion Shifted Fiber）がある。これらの光ファイバをＤＷＤＭで使用する場合、広い波長範囲にわたる残留分散の補償技術が重要である。   In optical communication, widening and speeding up of Dense Wavelength-Division Multiplexing (DWDM) transmission are rapidly progressing. In order to perform high-speed transmission, it is desirable to use, as these transmission lines, optical fibers whose chromatic dispersion is as small as possible in the transmission band, while chromatic dispersion is not zero in order to suppress nonlinear effects. Further, in an optical fiber already laid over a wide range, it is often used in a wavelength region where the dispersion is large. For example, a standard single-mode fiber (S-SMF) having zero dispersion near a wavelength of 1.3 μm has a wavelength of 1.53 to 1.63 μm due to the practical use of an erbium-doped optical fiber amplifier. Used in obi. In addition, a dispersion shifted fiber (DSF: Dispersion Shifted Fiber) in which zero dispersion is shifted to a wavelength near 1.55 μm may be used not only in the C band but also in the S band and the L band. In addition, there are various non-zero dispersion shifted fibers (NZ-DSFs) that do not become zero dispersion at a wavelength of 1.55 μm. When these optical fibers are used in DWDM, a technique for compensating for residual dispersion over a wide wavelength range is important.

分散補償には、様々な技術が用いられている。その中でも、分散補償ファイバ（ＤＣＦ：Dispersion Compensation Fiber）を用いる分散補償が最も実用化された技術である（例えば、特許文献１、２参照。）。ＤＣＦは、所望の分散補償量が得られるように光ファイバの屈折率分布を制御することで実現される。しかし、ＤＦＣは通常、補償の対象となる光ファイバと同程度の長さが必要であり、これをモジュール化した場合、大きな設置スペースが必要となるだけでなく、伝搬損失も無視できなくなる。また、ＤＣＦには正確な屈折率分布の制御が必要であり、作製が難しいという面があるだけでなく、広帯域で要求される分散補償量を満たすことが困難になることも多い。   Various techniques are used for dispersion compensation. Among them, dispersion compensation using a dispersion compensation fiber (DCF) is the most practical technique (see, for example, Patent Documents 1 and 2). The DCF is realized by controlling the refractive index distribution of the optical fiber so that a desired dispersion compensation amount can be obtained. However, the DFC normally needs to be as long as the optical fiber to be compensated. When this is modularized, not only a large installation space is required, but also propagation loss cannot be ignored. In addition, DCF requires precise control of the refractive index distribution, which is not only difficult to manufacture, but also often makes it difficult to satisfy the dispersion compensation amount required in a wide band.

ファイバブラッググレーティング（ＦＢＧ：Fiber Bragg Grating）もよく分散補償に用いられる技術の一つである（例えば、特許文献３参照。）。ＦＢＧは、ファイバにＵＶ光を照射することにより、ファイバコアの屈折率を変化させ、屈折率が異なることによるグレーティングを形成させることで分散補償を行う。これにより分散補償用の小型デバイスが実現可能となるが、屈折率変化の制御が難しく、さらにファイバの屈折率の変化に限度があるため、実現できる分散補償特性に限界がある。また、デバイスの小型化と大量生産にも限界がある。   Fiber Bragg Grating (FBG) is also one of the techniques often used for dispersion compensation (see, for example, Patent Document 3). The FBG performs dispersion compensation by irradiating the fiber with UV light, thereby changing the refractive index of the fiber core and forming a grating due to the different refractive index. This makes it possible to realize a small device for dispersion compensation, but it is difficult to control the change in the refractive index, and there is a limit to the change in the refractive index of the fiber. There are also limits to device miniaturization and mass production.

分散補償を行う領域をチャンネル毎に分けて、各々のチャンネル内で分散補償を行うチャープしたＦＢＧを一箇所に重ね合わせる構造も提案されている（例えば、特許文献４参照。）。これを用いることにより、必要となるファイバの長さが短くなるが、この従来技術では、単に複数のＦＢＧを重ね合わせるように設計されているため、各チャンネルの構造が接近し、各々のチャンネル特性に影響を及ぼすため、実現できる特性に限界がある。また、ＦＢＧを重ね合わせるために要求される屈折率の変化は、ＵＶ照射で得られないため、実現できない構造も生じる。   There has also been proposed a structure in which a region where dispersion compensation is performed is divided for each channel, and chirped FBGs for which dispersion compensation is performed in each channel are superposed at one place (see, for example, Patent Document 4). By using this, the required fiber length is shortened. However, in this prior art, the structure of each channel is approached because each FBG is designed so that a plurality of FBGs are simply overlapped. Since there is an influence on the characteristics, there is a limit to the characteristics that can be realized. In addition, since a change in refractive index required for superimposing FBGs cannot be obtained by UV irradiation, some structures cannot be realized.

光平面回路（ＰＬＣ：Planar Lightwave Circuit）は、平面に構築される光回路を用いて、分散補償を行うことができる。ラティス型ＰＬＣはその一例である（例えば、非特許文献１参照。）。しかし、ラティス型ＰＬＣは、結合共振器をカスケード接続して分散を制御しており、デジタルＩＩＲ（Infinite Impulse Response）フィルターの原理に基づいているため、実現する分散量が限られている。   An optical planar circuit (PLC: Planar Lightwave Circuit) can perform dispersion compensation by using an optical circuit constructed on a plane. Lattice type PLC is one example (see, for example, Non-Patent Document 1). However, the lattice type PLC controls the dispersion by cascading coupled resonators and is based on the principle of a digital IIR (Infinite Impulse Response) filter, so that the amount of dispersion to be realized is limited.

アレイ導波路格子（ＡＷＧ：Arrayed Waveguide Grating）で分波し、チャンネルごとに行路差を付け、遅延時間を調整した後にコリメートレンズで再び合波する仕組みも考えられているが（例えば、特許文献５参照。）、構造が複雑で作製が難しいだけでなく、必要とするスペースが大きい。   A mechanism is also considered in which demultiplexing is performed with an arrayed waveguide grating (AWG), a path difference is added for each channel, and the delay time is adjusted, and then multiplexed with a collimator lens (for example, Patent Document 5). Not only is the structure complicated and difficult to manufacture, but also requires a large amount of space.

ＶＩＰＡ（Virtually Imaged Phased Array）型分散補償器は、薄板の両面に反射膜をコーティングした波長分散素子（ＶＩＰＡ板）、及び反射ミラーにより構成された分散補償デバイスである（例えば、特許文献６参照。）。このデバイスは、３次元の構造で分散を調整しており、構造的に複雑であり、製造上極めて高い精度が要求される。
特許第３８５７２１１号公報 特許第３８１９２６４号公報 特開２００４−３２５５４９号公報 ＷＯ０３／０１０５８６号パンフレット K. Takiguchi, et. al, “Dispersion slope equalizer for dispersion shifted fiber using a lattice-form programmable optical filter on a planar lightwave circuit,” J. Lightwave Technol., pp. 1647-1656, vol. 16, no. 9, 1998 特許第３８５２４０９号公報 特開２００５−２７５１０１号公報 A VIPA (Virtually Imaged Phased Array) type dispersion compensator is a dispersion compensation device including a wavelength dispersion element (VIPA plate) in which a reflection film is coated on both surfaces of a thin plate, and a reflection mirror (see, for example, Patent Document 6). ). This device adjusts dispersion with a three-dimensional structure, is structurally complex, and requires extremely high accuracy in manufacturing.
Japanese Patent No. 3857211 Japanese Patent No. 3819264 JP 2004-325549 A WO03 / 010586 pamphlet K. Takiguchi, et. Al, “Dispersion slope equalizer for dispersion shifted fiber using a lattice-form programmable optical filter on a planar lightwave circuit,” J. Lightwave Technol., Pp. 1647-1656, vol. 16, no. 9 , 1998 Japanese Patent No. 3852409 JP-A-2005-275101

前述した従来技術における問題点は、次の通りである。
（１）ＤＣＦを用いる分散補償は、長尺ファイバの使用で必要スペースが大きく、小型化が困難である。また実現できる分散補償特性に限界がある。
（２）ＦＢＧを用いる分散補償は、実現できる分散補償特性に限界がある。
（３）ＦＢＧの重ね合わせを用いる分散補償は、実現できる分散補償特性に限界がある。
（４）ラティス型ＰＬＣを用いる分散補償は、実現可能な分散補償量が小さい。
（５）ＡＷＧ使用ＰＬＣは、構造が複雑であり、製造が難しく、コストが高くなってしまう。また、要求スペースが大きく、デバイスの小型化が困難である。
（６）ＶＩＰＡ型分散補償器は、構造が複雑であり、製造が難しく、コストが高くなってしまう。 The problems in the prior art described above are as follows.
(1) Dispersion compensation using DCF requires a large space due to the use of a long fiber and is difficult to reduce in size. In addition, there is a limit to the dispersion compensation characteristics that can be realized.
(2) Dispersion compensation using FBG has a limitation in dispersion compensation characteristics that can be realized.
(3) Dispersion compensation using FBG superposition has a limit in the dispersion compensation characteristics that can be realized.
(4) Dispersion compensation using lattice type PLC has a small amount of dispersion compensation that can be realized.
(5) The AWG-based PLC has a complicated structure, is difficult to manufacture, and increases the cost. In addition, the required space is large and it is difficult to reduce the size of the device.
(6) The VIPA type dispersion compensator has a complicated structure, is difficult to manufacture, and increases the cost.

本発明は、前記事情に鑑みてなされ、小型化でき、優れた分散補償特性を有し、製造が容易で低コスト化が可能な光導波路型波長分散補償デバイスの提供を目的とする。   The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical waveguide type chromatic dispersion compensation device that can be downsized, has excellent dispersion compensation characteristics, is easy to manufacture, and can be manufactured at low cost.

前記目的を達成するため、本発明は、クラッドに埋め込まれたコアの物理的寸法を変えることによりコアの等価屈折率が光伝搬方向にわたって不均一に変化する光導波路を反射型の波長分散補償手段として有し、前記光導波路は、分散補償する波長領域が複数のチャンネルに区切られ、各チャンネルの波長領域のうちの部分的領域のみで分散が補償される分散補償特性を有しており、分散が補償される前記部分的領域以外の前記チャンネルの波長領域では波長に対する群遅延の分布が平坦であることを特徴とする光導波路型波長分散補償デバイスを提供する。 In order to achieve the above object, the present invention provides a reflection-type chromatic dispersion compensation means for reflecting an optical waveguide whose equivalent refractive index of the core varies nonuniformly in the light propagation direction by changing the physical dimension of the core embedded in the cladding. have as the optical waveguide, the wavelength region to be dispersion compensated is divided into a plurality of channels has a partial region only dispersion compensation characteristic dispersion is compensated within the wavelength region of each channel, distributed An optical waveguide type chromatic dispersion compensating device is characterized in that the distribution of the group delay with respect to the wavelength is flat in the wavelength region of the channel other than the partial region where the compensation is made .

本発明の光導波路型波長分散補償デバイスにおいて、前記チャンネルの波長領域は、分散が補償される前記部分的領域以外の波長領域の、波長に対する群遅延の分布及び反射率の分布が、それと近接した分散補償を行う前記部分的領域の群遅延の分布及び反射率の分布とそれぞれ連続し、且つこの近接した分散補償を行う部分的領域から最も離れた波長で前記各分布が隣接するチャンネルの各分布と不連続となる分布構造を有することが好ましい。 In the optical waveguide type chromatic dispersion compensation device of the present invention, the wavelength region of the channel is close to the distribution of the group delay and the reflectance with respect to the wavelength in the wavelength region other than the partial region where the dispersion is compensated. each the distribution of distribution and reflectivity of the group delay of the partial region for dispersion compensation in succession, and each distribution channel, each distribution is adjacent farthest wavelength from a partial region for the proximate dispersion compensation And a discontinuous distribution structure.

本発明の光導波路型波長分散補償デバイスにおいて、前記コアの幅が光伝搬方向にわたって不均一に分布していることが好ましい。   In the optical waveguide type chromatic dispersion compensating device of the present invention, it is preferable that the width of the core is unevenly distributed in the light propagation direction.

本発明の光導波路型波長分散補償デバイスにおいて、前記コアの幅が、コア中心から幅方向両側が対称となるように光伝搬方向にわたって不均一に分布していることが好ましい。   In the optical waveguide type chromatic dispersion compensating device of the present invention, it is preferable that the width of the core is non-uniformly distributed over the light propagation direction so that both sides of the core are symmetric from the center of the core.

本発明の光導波路型波長分散補償デバイスにおいて、前記コアの幅が、コア中心から幅方向両側が非対称となるように光伝搬方向にわたって不均一に分布した構成としてもよい。   In the optical waveguide type chromatic dispersion compensating device of the present invention, the width of the core may be non-uniformly distributed over the light propagation direction so as to be asymmetric on both sides in the width direction from the core center.

本発明の光導波路型波長分散補償デバイスにおいて、前記コアの幅が、コア中心から幅方向両側のうち一方の側のみが光伝搬方向にわたって不均一に分布した構成としてもよい。   In the optical waveguide type chromatic dispersion compensating device of the present invention, the width of the core may be configured such that only one side of both sides in the width direction from the core center is unevenly distributed in the light propagation direction.

本発明の光導波路型波長分散補償デバイスにおいて、前記コアが、前記光導波路内に直線状に設けられていることが好ましい。   In the optical waveguide type chromatic dispersion compensating device of the present invention, it is preferable that the core is provided linearly in the optical waveguide.

本発明の光導波路型波長分散補償デバイスにおいて、前記コアが、前記光導波路内に蛇行状に設けられた構成としてもよい。   In the optical waveguide type chromatic dispersion compensating device of the present invention, the core may be provided in a meandering manner in the optical waveguide.

本発明の光導波路型波長分散補償デバイスにおいて、前記コアの幅が、光伝搬方向の中央部に幅変化の小さい分布領域があり、該中央部の両側に幅変化が中央部よりも大きな幅変化極大部を有することが好ましい。   In the optical waveguide type chromatic dispersion compensating device according to the present invention, the core has a distribution region in which the width change is small in the center portion in the light propagation direction, and the width change is larger on both sides of the center portion than in the center portion. It is preferable to have a local maximum.

本発明の光導波路型波長分散補償デバイスにおいて、前記光導波路の透過端が無反射終端で終端され、反射端でサーキュレータ又は方向性結合器を介して出力を取り出すように構成されたことが好ましい。   In the optical waveguide type chromatic dispersion compensating device of the present invention, it is preferable that the transmission end of the optical waveguide is terminated at a non-reflective end and an output is taken out at the reflection end via a circulator or a directional coupler.

本発明の光導波路型波長分散補償デバイスにおいて、前記光導波路は、所定の波長帯域において、所定の長さの被補償光ファイバの波長分散を打ち消す分散補償特性を有することが好ましい。   In the optical waveguide type chromatic dispersion compensation device of the present invention, the optical waveguide preferably has a dispersion compensation characteristic that cancels the chromatic dispersion of the compensated optical fiber having a predetermined length in a predetermined wavelength band.

本発明の光導波路型波長分散補償デバイスにおいて、前記光導波路は、中心波長λｃが１２８０ｎｍ≦λｃ≦１３２０ｎｍ及び１４９０ｎｍ≦λｃ≦１６１３ｎｍの範囲、動作帯域ΔＢＷが０．１ｎｍ≦ΔＢＷ≦６０ｎｍの範囲において、分散Ｄが−３０００ｐｓ／ｎｍ≦Ｄ≦３０００ｐｓ／ｎｍの範囲、分散に対する分散スロープの比ＲＤＳが−０．１ｎｍ−１≦ＲＤＳ≦０．１ｎｍ−１の範囲の特性を有することが好ましい。 In the optical waveguide type chromatic dispersion compensation device of the present invention, the optical waveguide has a center wavelength λ c in the range of 1280 nm ≦ λ c ≦ 1320 nm and 1490 nm ≦ λ c ≦ 1613 nm, and an operating band ΔBW of 0.1 nm ≦ ΔBW ≦ 60 nm. In the range, the dispersion D preferably has characteristics in the range of −3000 ps / nm ≦ D ≦ 3000 ps / nm, and the ratio RDS of the dispersion slope to the dispersion is in the range of −0.1 nm −1 ≦ RDS ≦ 0.1 nm −1. .

本発明の光導波路型波長分散補償デバイスにおいて、前記光導波路の光伝搬方向にわたるコアの等価屈折率分布が、Ｚａｋｈａｒｏｖ−Ｓｈａｂａｔ方程式において、反射係数のスペクトルデータからポテンシャル関数を数値的に導く逆散乱問題として解き、所望の反射スペクトルを実現するためのポテンシャルを推測する設計法で設計されることが好ましい。   In the optical waveguide type chromatic dispersion compensating device of the present invention, the equivalent refractive index distribution of the core over the light propagation direction of the optical waveguide is an inverse scattering problem that numerically derives a potential function from the spectral data of the reflection coefficient in the Zakharov-Shabat equation. And is preferably designed by a design method for estimating a potential for realizing a desired reflection spectrum.

前記光導波路の光伝搬方向にわたるコアの等価屈折率分布は、光導波路の前方及び後方に伝搬する電力波振幅なる変数を導入した波動方程式より、光導波路の等価屈折率の対数の微分から導かれるポテンシャルを有するＺａｋｈａｒｏｖ−Ｓｈａｂａｔ方程式に帰着させ、反射係数のスペクトルデータからポテンシャル関数を数値的に導く逆散乱問題として解き、所望の反射スペクトルを実現するためのポテンシャルを推測し、それに基づいて等価屈折率を求め、予め求められた、所定のコアの厚さとコア-クラッド間の比屈折率差を持ったコアにおける等価屈折率とコア寸法との関係から、光導波路の光伝搬方向にわたるコア寸法を算出して設計されることが好ましい。   The equivalent refractive index distribution of the core across the light propagation direction of the optical waveguide is derived from the logarithmic derivative of the equivalent refractive index of the optical waveguide from the wave equation that introduces a variable of the power wave amplitude propagating forward and backward of the optical waveguide. Reduced to the Zakharov-Shabat equation with potential, solved as an inverse scattering problem that numerically derives the potential function from the spectral data of the reflection coefficient, estimated the potential for realizing the desired reflection spectrum, and based on it, the equivalent refractive index Calculate the core dimensions over the optical propagation direction of the optical waveguide based on the relationship between the equivalent refractive index and core dimensions of the core with a predetermined core thickness and core-clad relative refractive index difference. Are preferably designed.

本発明の光導波路型波長分散補償デバイスにおいて、前記光導波路の光伝搬方向にわたるコアの等価屈折率分布は、分散補償する帯域の中心波長のスケールではほぼ周期構造であり、中心波長より大きいスケールでは、前記逆散乱問題で決まる非周期構造の二階層構造を有することが好ましい。   In the optical waveguide type chromatic dispersion compensation device of the present invention, the equivalent refractive index distribution of the core in the optical propagation direction of the optical waveguide is substantially a periodic structure at the center wavelength scale of the dispersion compensation band, and at a scale larger than the center wavelength. It is preferable to have a two-layer structure with an aperiodic structure determined by the inverse scattering problem.

また本発明は、光導波路の下クラッド層を設け、
次いで、前記下クラッド層上に、下クラッド層よりも屈折率の大きいコア層を設け、
次いで、前記コア層に、コアの等価屈折率が光伝搬方向にわたって不均一に変化するように設計された所定のコア形状を残し、それ以外の部分を除去する加工を施してコアを形成し、
次いで、前記コアを覆うクラッドを設けることによって光導波路を製造し、前述した本発明に係る光導波路型波長分散補償デバイスを製造することを特徴とする光導波路型波長分散補償デバイスの製造方法を提供する。 The present invention also provides a lower cladding layer of the optical waveguide,
Next, a core layer having a refractive index larger than that of the lower cladding layer is provided on the lower cladding layer,
Next, the core layer is left with a predetermined core shape designed so that the equivalent refractive index of the core varies nonuniformly in the light propagation direction, and a core is formed by removing the other portions.
Next, an optical waveguide is manufactured by providing a clad covering the core, and an optical waveguide type chromatic dispersion compensation device according to the present invention described above is manufactured. To do.

本発明の光導波路型波長分散補償デバイスは、クラッドに埋め込まれたコアの等価屈折率が光伝搬方向にわたって不均一に変化する光導波路を反射型の波長分散補償手段として有し、する構成なので、分散補償ファイバ等を用いる従来技術に比べて小型化することができ、設置スペースが少なくて済む。
また本発明の光導波路型波長分散補償デバイスは、従来のＦＢＧを用いた分散補償に比べ、実現できる分散補償特性が広くなるなど、優れた分散補償特性を得ることができる。
また本発明の光導波路型波長分散補償デバイスは、ＰＬＣやＶＩＰＡ等の従来の分散補償デバイスに比べ、構造が簡単で低コストで製造することができる。
また本発明の光導波路型波長分散補償デバイスは、分散補償する波長領域が複数のチャンネルに区切られ、各チャンネルの波長領域のうちの部分的領域のみで分散が補償される分散補償特性を有しているものなので、必要になる最大遅延量を短くすることができ、必要な光導波路の長さが短かくなり、デバイスが小型化できるとともに、光導波路の伝送損失を低くすることができる。 Since the optical waveguide type chromatic dispersion compensation device of the present invention has an optical waveguide in which the equivalent refractive index of the core embedded in the cladding changes nonuniformly over the light propagation direction as a reflection type chromatic dispersion compensation means, Compared to the conventional technique using a dispersion compensating fiber or the like, the size can be reduced and installation space can be reduced.
In addition, the optical waveguide type chromatic dispersion compensation device of the present invention can obtain excellent dispersion compensation characteristics such as a wider dispersion compensation characteristic that can be realized as compared with dispersion compensation using a conventional FBG.
In addition, the optical waveguide type chromatic dispersion compensation device of the present invention has a simple structure and can be manufactured at a lower cost than conventional dispersion compensation devices such as PLC and VIPA.
The optical waveguide type chromatic dispersion compensation device of the present invention has a dispersion compensation characteristic in which the wavelength region for dispersion compensation is divided into a plurality of channels, and dispersion is compensated only in a partial region of the wavelength regions of each channel. Therefore, the required maximum delay amount can be shortened, the required length of the optical waveguide can be shortened, the device can be miniaturized, and the transmission loss of the optical waveguide can be reduced.

本発明の光導波路型波長分散補償デバイスの製造方法によれば、前述したように優れた分散補償特性を有する小型の分散補償デバイスを、低コストで効率よく製造することができる。   According to the method for manufacturing an optical waveguide type chromatic dispersion compensation device of the present invention, a small dispersion compensation device having excellent dispersion compensation characteristics as described above can be efficiently manufactured at low cost.

本発明の分散補償デバイスは、クラッドに埋め込まれたコアの等価屈折率が光伝搬方向にわたって不均一に変化する光導波路を反射型の波長分散補償手段として有し、この光導波路は、分散補償する波長領域が複数のチャンネルに区切られ、各チャンネルの波長領域のうちの部分的領域のみで分散が補償される分散補償特性を有していることを特徴としている。   The dispersion compensation device of the present invention has an optical waveguide in which the equivalent refractive index of the core embedded in the cladding varies non-uniformly in the light propagation direction as a reflection type chromatic dispersion compensation means, and this optical waveguide compensates for dispersion. The wavelength region is divided into a plurality of channels and has a dispersion compensation characteristic in which dispersion is compensated only in a partial region of the wavelength regions of each channel.

以下、図面を参照して本発明の光導波路型波長分散補償デバイス（以下、分散補償デバイスと略記する。）の実施形態を説明する。
図１は、本発明の分散補償デバイスの主な構成要素である光導波路の一実施形態を示す概略斜視図である。本実施形態の光導波路は、コアの等価屈折率を光伝搬方向にわたって不均一に変化させる手段として、コアの幅ｗを長手方向（ｚ）にわたって変化させた非均一幅をもつ平面導波路（Non-uniform Planar WaveGuide；以下、ＮＰＷＧと記す。）である。図１中、符号１０はＮＰＷＧ、１１はコア、１２はクラッドである。 Embodiments of an optical waveguide type chromatic dispersion compensation device (hereinafter abbreviated as dispersion compensation device) of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic perspective view showing an embodiment of an optical waveguide which is a main component of the dispersion compensation device of the present invention. The optical waveguide of the present embodiment is a planar waveguide (Non) having a non-uniform width obtained by changing the width w of the core in the longitudinal direction (z) as means for changing the equivalent refractive index of the core non-uniformly in the light propagation direction. -uniform Planar WaveGuide; hereinafter referred to as NPWG). In FIG. 1, reference numeral 10 is an NPWG, 11 is a core, and 12 is a cladding.

本実施形態のＮＰＷＧ１０は、クラッド１２中に、コア１１を有する構造である。コア１１は、一定の高さｈ３を有するが、その幅ｗは長手方向（ｚ）方向にわたって不均一に変化させ、導波路の伝搬モードの局所等価屈折率を変化させており、これによって反射型の波長分散補償機能を持たせている。 The NPWG 10 of this embodiment has a structure having a core 11 in a clad 12. The core 11 has a constant height h 3, the width w is the longitudinal direction (z) unevenly varied over direction and by changing the local equivalent refractive index of the propagating mode of the waveguide, reflected by this Type chromatic dispersion compensation function.

このＮＰＷＧ１０の動作原理は、ＦＢＧのグレーティングと一見類似しているところもあるが、等価屈折率の変化に関し、ＦＢＧではコア媒質の屈折率を変化させるのに対して、本実施形態のＮＰＷＧ１０では、コア１１の幅を長手方向に沿って変化させることで等価屈折率を変化させており、等価屈折率の変化に関して両者は全く相違している。
コア１１の幅を長手方向に沿って変化させることで得られる等価屈折率の変動率は、ＦＢＧの場合に比べて大きい上、細かく正確な制御が容易である。
また、ＮＰＷＧ１０の構造は、平面的となっているため、周知の製造プロセスで大量に製造することができ、低コスト化を図ることができる。 The operation principle of the NPWG 10 is somewhat similar to that of the FBG grating. However, the FBG changes the refractive index of the core medium with respect to the change of the equivalent refractive index, whereas the NPWG 10 of the present embodiment changes the refractive index of the core medium. The equivalent refractive index is changed by changing the width of the core 11 along the longitudinal direction, and the two are completely different with respect to the change of the equivalent refractive index.
The variation rate of the equivalent refractive index obtained by changing the width of the core 11 along the longitudinal direction is larger than that of the FBG, and fine and accurate control is easy.
Further, since the structure of the NPWG 10 is planar, it can be manufactured in large quantities by a known manufacturing process, and the cost can be reduced.

このＮＰＷＧ１０は、石英ガラス系材料を用いることができる。その場合、例えば、クラッドを純石英ガラスで作製し、コアはゲルマニウム添加石英ガラスを用いればよい。また樹脂系材料の使用も可能である。   This NPWG 10 can use a quartz glass-based material. In that case, for example, the clad may be made of pure quartz glass, and the core may be made of germanium-added quartz glass. It is also possible to use a resin material.

このＮＰＷＧ１０を用いた分散補償デバイスにおいて、図２に示すように、分散補償の対象とする帯域を複数のチャンネルに区分し、それぞれのチャンネルごとに分散補償を行うこともできる。図２（Ａ）は、ＮＰＷＧ１０の群遅延（Group delay）特性を示すグラフであり、また（Ｂ）は、コア１１における光の波長と反射との関係を模式的に示す図である。   In the dispersion compensation device using the NPWG 10, as shown in FIG. 2, the band to be subjected to dispersion compensation can be divided into a plurality of channels, and dispersion compensation can be performed for each channel. 2A is a graph showing the group delay characteristics of the NPWG 10, and FIG. 2B is a diagram schematically showing the relationship between the wavelength of light and the reflection in the core 11. As shown in FIG.

光ファイバの波長分散を補償する場合、要求される分散特性は単調変化することが多い。その結果、補償する帯域が広くなればなるほど、帯域内で絶対遅延量（図２中のτｍａｘ−τｍｉｎ）が高くなる。ＮＰＷＧは図示のように、遅延が早い波長帯（図２中のλ１）の信号をデバイスの手前で反射させ、遅延が遅い波長帯（図２中のλｎ）の信号をデバイスの奥で反射させるように動作するので、絶対遅延量が高い場合、必要とするデバイスの長さが長くなる。つまり、必要とするデバイスの長さＬは、おおよそ次式（Ａ）で見積もることができる。 When compensating for the chromatic dispersion of an optical fiber, the required dispersion characteristics often change monotonously. As a result, the wider the band to be compensated, the higher the absolute delay amount (τmax−τmin in FIG. 2) within the band. As shown in the figure, the NPWG reflects a signal in a wavelength band with a fast delay (λ 1 in FIG. 2) in front of the device and reflects a signal in a wavelength band with a slow delay (λn in FIG. 2) at the back of the device. Therefore, when the absolute delay amount is high, the required device length becomes long. That is, the required device length L can be estimated by the following equation (A).

Figure 0005193585
Figure 0005193585

ただし、ｃは光速、ｎｅｆｆは導波路の等価屈折率、τｍａｘとτｍｉｎはそれぞれ最大遅延量と最小遅延量を表す。 Where c is the speed of light, n eff is the equivalent refractive index of the waveguide, and τmax and τmin are the maximum delay amount and the minimum delay amount, respectively.

本発明は、図３に示すように、区分けされたチャンネル全体（例えば、図中の［λ１〜λ２］）で分散補償を行うのではなく、図４に示すように、補償対象のチャンネルが本当に使用する波長領域（例えば、図４中の［λ'１〜λ'２］）のみを補償することを特徴としている。図３に示すように、チャンネル全体［λ１〜λ２］で分散を補償するよりも、図４に示すように、その一部［λ'１〜λ'２］のみを補償するようにすれば、必要になるデバイス内最大遅延量を［τｍａｘ〜τｍｉｎ］の範囲から［τ'ｍａｘ〜τ'ｍｉｎ］の範囲へと短くすることができ、より短いデバイスが実現できる。 As shown in FIG. 3, the present invention does not perform dispersion compensation for the entire divided channel (for example, [λ 1 to λ 2 ] in the figure), but as shown in FIG. Is compensated only for the wavelength region that is really used (for example, [λ ′ 1 to λ ′ 2 ] in FIG. 4). As shown in FIG. 3, rather than compensating for dispersion across the channel [λ 1 ~λ 2], as shown in FIG. 4, it suffices to compensate for the part [λ '1 ~λ' 2] only For example, the required maximum delay amount in the device can be shortened from the range of [τmax to τmin] to the range of [τ′max to τ′min], and a shorter device can be realized.

実際、補償帯域外（図４中の［λ１〜λ'１］や［λ２〜λ'２］）では、群遅延がτ'ｍａｘとτ'ｍｉｎの範囲を超えないようにすればよいが、境界λ'１とλ'２での反射スペクトルが不連続になると、補償帯域内［λ'１〜λ'２］でも不連続性の影響で特性に乱れが生じる。そこで、本発明では、図５に示すように、補償帯域外における群遅延が平坦で、補償帯域の境界λ'１とλ'２で連続となるようにした。そうすることにより、不連続が実使用帯域に与える影響を抑えることができる。 Actually, outside the compensation band ([λ 1 to λ ′ 1 ] or [λ 2 to λ ′ 2 ] in FIG. 4), the group delay may be prevented from exceeding the range of τ′max and τ′min. However, when the reflection spectrum at the boundaries λ ′ 1 and λ ′ 2 becomes discontinuous, the characteristic is disturbed due to the discontinuity within the compensation band [λ ′ 1 to λ ′ 2 ]. Therefore, in the present invention, as shown in FIG. 5, the group delay outside the compensation band is flat and continuous at the boundaries λ ′ 1 and λ ′ 2 of the compensation band. By doing so, the influence which a discontinuity has on an actual use band can be suppressed.

デバイスの設計は、所望の反射スペクトルから必要な幅分布を得る逆散乱問題の手法を用いる。
まず、導波路に伝搬する電磁界を次のように定式化する（参考文献：J. E. Sipe, L. Poladian, and C. Martijn de Sterke, “Propagation through nonuniform grating structures,” J. Opt. Soc. Am. A, vol. 11, no. 4, pp. 1307-1320, 1994）。電磁界の時間変動をｅｘｐ（−ｉωｔ）と仮定すると、Ｍａｘｗｅｌｌ方程式により、次式（１）、（２）となる。 The device design uses the inverse scattering problem approach to obtain the required width distribution from the desired reflection spectrum.
First, the electromagnetic field propagating in the waveguide is formulated as follows (reference: JE Sipe, L. Poladian, and C. Martijn de Sterke, “Propagation through nonuniform grating structures,” J. Opt. Soc. Am A, vol. 11, no. 4, pp. 1307-1320, 1994). Assuming that the time variation of the electromagnetic field is exp (−iωt), the following equations (1) and (2) are obtained according to the Maxwell equation.

Figure 0005193585
Figure 0005193585

Figure 0005193585
Figure 0005193585

ただし、Ｅ，Ｈはそれぞれ電界と磁界の複素振幅を表し、ｎは導波路の屈折率を表す。ここで、次式（３），（４）   Here, E and H represent the complex amplitudes of the electric field and magnetic field, respectively, and n represents the refractive index of the waveguide. Here, the following equations (3), (4)

Figure 0005193585
Figure 0005193585

Figure 0005193585
Figure 0005193585

で定義されるｚの前方に伝搬する電力波振幅Ａ＋（ｚ）と後方に伝搬する電力波振幅Ａ−（ｚ）を導入する。ただし、Ｚ０＝√μ０／ε０は真空中のインピーダンスを表し、ｎ０は参照屈折率を表す。これらの変数は次式（５），（６）を満たす： The power wave amplitude A + (z) propagating forward of z and the power wave amplitude A − (z) propagating backward are defined. However, Z 0 = √μ 0 / ε 0 represents the impedance in vacuum, and n 0 represents the reference refractive index. These variables satisfy the following equations (5) and (6):

Figure 0005193585
Figure 0005193585

Figure 0005193585
Figure 0005193585

ただし、ｃは真空中の光速を表す。この式は、次式（７） Here, c represents the speed of light in vacuum. This equation is expressed by the following equation (7)

Figure 0005193585
Figure 0005193585

で変数変換を行うと、次式（８）、（９）に示すＺａｋｈａｒｏｖ−Ｓｈａｂａｔ方程式に帰着される： If the variable conversion is performed in, it is reduced to the Zakharov-Shabat equation shown in the following equations (8) and (9):

Figure 0005193585
Figure 0005193585

Figure 0005193585
Figure 0005193585

ただし、ω０は参照角周波数を表す。
Ｚａｋｈａｒｏｖ−Ｓｈａｂａｔ方程式は、逆散乱問題として解くことができる。すなわち、次式（１０） However, ω 0 represents the reference angular frequency.
The Zakharov-Shabat equation can be solved as an inverse scattering problem. That is, the following formula (10)

Figure 0005193585
Figure 0005193585

で定義される反射係数のスペクトルデータから、ポテンシャル関数u(x)を数値的に解くことができる（参考文献：P. V. Frangos and D. L. Jaggard, “A numerical solution to the Zakharov-Shabat inverse scattering problem,” IEEE Trans. Antennas and Propag., vol. 39, no. 1, pp. 74-79, 1991）。これを前記問題に当てはめると、所望の反射スペクトルを実現するためのポテンシャルを求めることができる。ここで、反射スペクトルとは、波長に対する群遅延量と反射率から得られる複素反射データをいう。さらに、不均一とは、物理寸法が導波路の進行方向の場所とともに変化していることをいう。
ポテンシャルu(x)が得られれば、局所等価屈折率n(x)は、次式（１１）のように求められる。 The potential function u (x) can be solved numerically from the spectral data of the reflection coefficient defined in (Reference: PV Frangos and DL Jaggard, “A numerical solution to the Zakharov-Shabat inverse scattering problem,” IEEE Trans. Antennas and Propag., Vol. 39, no. 1, pp. 74-79, 1991). When this is applied to the above problem, a potential for realizing a desired reflection spectrum can be obtained. Here, the reflection spectrum refers to complex reflection data obtained from the group delay amount and the reflectance with respect to the wavelength. Furthermore, non-uniform means that the physical dimension changes with the location of the waveguide in the traveling direction.
If the potential u (x) is obtained, the local equivalent refractive index n (x) can be obtained by the following equation (11).

Figure 0005193585
Figure 0005193585

さらに、実際作製しようとする導波路におけるコアの厚み、コアの屈折率、およびクラッドの屈折率から求められる、コアの幅に対する等価屈折率との関係から、光の伝搬方向の所定の位置におけるコア幅ｗ（ｘ）を求めることができる。   Further, the core at a predetermined position in the light propagation direction is obtained from the relationship between the equivalent refractive index to the core width, which is obtained from the thickness of the core, the refractive index of the core, and the refractive index of the cladding in the waveguide to be actually manufactured. The width w (x) can be determined.

被補償ファイバの使用波長と使用帯域及び使用長さを考慮し、被補償ファイバの分散と逆になるように（分散補償できるように）スペクトルデータを作成し、前記設計手法を用いて逆問題を解き、光平面導波路を作成すれば、小型分散補償デバイスが実現される。   Considering the wavelength, bandwidth, and length of the compensated fiber, create spectral data that is opposite to the dispersion of the compensated fiber (so that dispersion can be compensated), and use the above design method to solve the inverse problem. Solving and creating an optical planar waveguide realizes a compact dispersion compensation device.

そして、被補償光ファイバの使用波長と使用帯域及び使用長さを考慮し、被補償光ファイバの分散と逆になるように（分散補償できるように）スペクトルデータを作成し、前記設計手法を用いて逆問題を解き、ＮＰＷＧ１０を作製すれば、小型で高性能の分散補償デバイスが実現される。
本発明で特徴的なことは、所望する分散補償デバイスが示す反射スペクトルを分散補償が必要な波長帯域（チャネル）に分け、その各々の波長帯域内でのみ必要な補償群遅延を示すように設定することである。さらに、上記分散補償が必要ではない波長帯域において、少なくとも分散補償が必要な波長帯域に連続する所定の波長帯域では、波長に対する群遅延が一定となるように反射スペクトルを設定する。なお、この波長に対する群遅延の一定値は、分散補償が必要な波長帯域であって、この分散補償が必要でない波長帯域と連続する帯域の境界値と同一にすることが好ましい。さらに、上記所定の波長帯域よりを超えた波長において、波長に対する群遅延が不連続となるように反射スペクトルを設定する。 Then, in consideration of the wavelength used, the band used, and the length of the optical fiber to be compensated, spectral data is created so as to be opposite to the dispersion of the optical fiber to be compensated (so that dispersion compensation can be performed), and the design method is used. If the inverse problem is solved and the NPWG 10 is manufactured, a small and high-performance dispersion compensation device can be realized.
What is characteristic of the present invention is that the reflection spectrum indicated by the desired dispersion compensation device is divided into wavelength bands (channels) that require dispersion compensation, and is set so as to indicate the necessary compensation group delay only within each wavelength band. It is to be. Further, in the wavelength band that does not require dispersion compensation, the reflection spectrum is set so that the group delay with respect to the wavelength is constant at least in a predetermined wavelength band that is continuous with the wavelength band that requires dispersion compensation. The constant value of the group delay with respect to this wavelength is a wavelength band that requires dispersion compensation, and is preferably the same as a boundary value between a wavelength band that does not require dispersion compensation and a continuous band. Further, the reflection spectrum is set so that the group delay with respect to the wavelength becomes discontinuous at a wavelength exceeding the predetermined wavelength band.

前記実施形態では、クラッド１１中に、高さ（厚さ）が一定で幅が長手方向にわたって不均一に変化するコア１１が埋設された構造のＮＰＷＧ１０を例示したが、本発明に用いる光導波路は本例示にのみ限定されず、種々の変更が可能である。
例えば、コア１１の幅分布は、図６（Ａ）に示すように、コア１１中心から幅方向両側が対称となるように光伝搬方向にわたって不均一に分布している構造の他、図６（Ｂ）に示すように、コア１１中心から幅方向両側が非対称となるように光伝搬方向にわたって不均一に分布している構造であってもよい。
また、コア１１は、図１に示すように、ＮＰＷＧ１０の長手方向（ｚ）に沿って直線状に設ける構造の他、図７に示すように、蛇行状にコア１１を設ける構造としてもよい。このように蛇行状にコア１１を設けた構造とすることで、ＮＰＷＧ１０をより小型化することが可能となる。 In the above embodiment, the NPWG 10 having a structure in which the core 11 whose height (thickness) is constant and whose width varies non-uniformly in the longitudinal direction is embedded in the clad 11, but the optical waveguide used in the present invention is The present invention is not limited to this example, and various modifications are possible.
For example, as shown in FIG. 6A, the width distribution of the core 11 is not uniformly distributed over the light propagation direction so that both sides in the width direction are symmetric from the center of the core 11, as shown in FIG. As shown in B), it may be a structure that is unevenly distributed over the light propagation direction so that both sides in the width direction are asymmetric from the center of the core 11.
In addition to the structure in which the core 11 is provided linearly along the longitudinal direction (z) of the NPWG 10 as shown in FIG. 1, the core 11 may be provided in a meandering manner as shown in FIG. By adopting such a structure in which the core 11 is provided in a meandering manner, the NPWG 10 can be further downsized.

図８は、本発明の分散補償デバイスの一実施形態を示す構成図である。本実施形態の分散補償デバイス２０は、前述したＮＰＷＧ１０と、その反射端１３側に接続されたサーキュレータ１５とを備えて構成され、またＮＰＷＧ１０の透過端１４は無反射終端１６になっている。サーキュレータ１５には、入力側（input）に図示していない被補償光ファイバが接続され、出力側（output）にも下流側の光ファイバが接続され、光伝送路内で使用される。本発明の分散補償デバイス２０は反射型デバイスであり、被補償光ファイバからサーキュレータ１５の入力側に入力された光信号は、ＮＰＷＧ１０に入って反射され、その反射波がサーキュレータ１５を介して出力されるようになっている。   FIG. 8 is a block diagram showing an embodiment of the dispersion compensation device of the present invention. The dispersion compensation device 20 of the present embodiment is configured to include the NPWG 10 described above and a circulator 15 connected to the reflection end 13 side, and the transmission end 14 of the NPWG 10 is a non-reflection termination 16. The circulator 15 is connected to an optical fiber to be compensated (not shown) on the input side (input), and an optical fiber on the downstream side is also connected to the output side (output), and is used in the optical transmission line. The dispersion compensation device 20 of the present invention is a reflection type device, and an optical signal input from the compensated optical fiber to the input side of the circulator 15 enters the NPWG 10 and is reflected, and the reflected wave is output through the circulator 15. It has become so.

この分散補償デバイス２０のＮＰＷＧ１０は、前述したように、被補償光ファイバの波長分散を補償できるような反射率特性を有しているので、被補償光ファイバから出力された光信号がＮＰＷＧ１０で反射される際に、その光信号の波長分散が補正されて出力される。そして、分散補償デバイス２０から出力された光信号は、サーキュレータ１５の出力側に接続された下流側の光ファイバに入力され、このファイバ内を伝搬する。   As described above, the NPWG 10 of the dispersion compensation device 20 has reflectivity characteristics that can compensate for the chromatic dispersion of the compensated optical fiber. Therefore, the optical signal output from the compensated optical fiber is reflected by the NPWG 10. In this case, the chromatic dispersion of the optical signal is corrected and output. The optical signal output from the dispersion compensation device 20 is input to the downstream optical fiber connected to the output side of the circulator 15 and propagates through the fiber.

本発明の分散補償デバイス２０の主要構成要素であるＮＰＷＧ１０は、例えば、次のように製造される。
（ａ）まず、ＮＰＷＧ１０の下クラッド層を設け、
（ｂ）次いで、前記下クラッド層上に、下クラッド層よりも屈折率の大きいコア層を設け、
（ｃ）次いで、前記コア層に、コアの等価屈折率が光伝搬方向にわたって不均一に変化するように設計された所定のコア形状を残し、それ以外の部分を除去する加工を施してコア１１を形成し、
（ｄ）次いで、前記コア１１を覆うクラッド１２を設け、ＮＰＷＧ１０を製造する。 The NPWG 10, which is a main component of the dispersion compensation device 20 of the present invention, is manufactured as follows, for example.
(A) First, a lower cladding layer of the NPWG 10 is provided,
(B) Next, a core layer having a refractive index larger than that of the lower cladding layer is provided on the lower cladding layer,
(C) Next, the core layer 11 is processed by leaving a predetermined core shape designed so that the equivalent refractive index of the core varies nonuniformly in the light propagation direction, and removing the other portions. Form the
(D) Next, the cladding 12 covering the core 11 is provided, and the NPWG 10 is manufactured.

また本発明の分散補償デバイス２０は、前述した通りＮＰＷＧ１０を製造した後、該ＮＰＷＧ１０の透過端１４を無反射終端１６で終端し、反射端１３にサーキュレータ１５又は方向性結合器を接続して図８に示す分散補償デバイス２０を作製する工程を行うことで製造される。   The dispersion compensation device 20 of the present invention is manufactured by manufacturing the NPWG 10 as described above, terminating the transmissive end 14 of the NPWG 10 with a non-reflective terminal 16, and connecting the circulator 15 or the directional coupler to the reflective end 13. The dispersion compensation device 20 shown in FIG.

ＮＰＷＧ１０のコア１１を形成する際、コア１０の等価屈折率が光伝搬方向にわたって不均一に変化するように設計された所定のコア形状を持ったマスクを用いたフォトリソグラフィー法によってコア１０を形成することが好ましい。このフォトリソグラフィー法に用いる材料や手順は、半導体製造分野等で周知のフォトリソグラフィー法に用いる材料や手順を用いて実施することができる。また、クラッド層やコア層の成膜方法は、一般の光導波路の製造において用いられている周知の成膜技術を用いて実施することができる。   When the core 11 of the NPWG 10 is formed, the core 10 is formed by a photolithography method using a mask having a predetermined core shape designed so that the equivalent refractive index of the core 10 changes nonuniformly in the light propagation direction. It is preferable. The material and procedure used for this photolithography method can be implemented using the material and procedure used for the photolithography method well-known in the semiconductor manufacturing field etc. Moreover, the film-forming method of a clad layer or a core layer can be implemented using the well-known film-forming technique currently used in manufacture of a general optical waveguide.

波長領域［１５４２．１４ｎｍ〜１５５８．１７ｎｍ］において、分散量Ｄ＝−１０００ｐｓ／ｎｍ、分散に対する分散スロープの比ＲＤＳ＝０．００３４ｎｍ−１となる波長分散の補償を実現する分散補償デバイスを設計した。ただし、本実施例では、波長領域を周波数ｆが、１９３．４＋０．１ｎＴＨｚ≦ｆ≦１９３．５＋０．１ｎＴＨｚを満たす２０チャンネルに分けており、それぞれのチャンネル内で中心周波数を中心とした帯域０．０２ＴＨｚの領域でのみ分散補償を行っている。ここで、ｎは−１０≦ｎ≦９を満たす整数を表す。なお、これらのチャンネルはＩＴＵグリッド間隔を満たす。本実施例の分散補償デバイスは、長さ５８ｋｍのＳ−ＳＭＦの残留分散を補償することができる。 In the wavelength region [154.14 nm to 1558.17 nm], a dispersion compensation device that realizes chromatic dispersion compensation in which the dispersion amount D = −1000 ps / nm and the ratio of dispersion slope to dispersion RDS = 0.0036 nm −1 was designed. . However, in this embodiment, the wavelength region is divided into 20 channels satisfying the frequency f of 193.4 + 0.1 nTHz ≦ f ≦ 193.5 + 0.1 nTHZ, and the band 0. Dispersion compensation is performed only in the 02 THz region. Here, n represents an integer satisfying −10 ≦ n ≦ 9. These channels satisfy the ITU grid interval. The dispersion compensation device according to the present embodiment can compensate for the residual dispersion of the S-SMF having a length of 58 km.

図９は、本実施例で作製した分散補償デバイスのＮＰＷＧのポテンシャル分布を表すグラフである。図中の横軸は、中心波長１５５０．１２ｎｍで規格された場所を表す。このポテンシャルを用いると、図１０に示す群遅延特性と図１１に示す反射率特性が得られる。両図には、設計に用いたスペクトルデータ（designed）と得られたスペクトルデータ（realized）が示されている。   FIG. 9 is a graph showing the NPWG potential distribution of the dispersion compensation device manufactured in this example. The horizontal axis in the figure represents a location standardized at a center wavelength of 1550.12 nm. When this potential is used, the group delay characteristic shown in FIG. 10 and the reflectance characteristic shown in FIG. 11 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

図１２は、図１０の一部拡大図であり、図示のようにスペクトル不連続による影響は、群遅延のリップルをもたらすが、分散補償を行う帯域への影響は限定的となっている。   FIG. 12 is a partially enlarged view of FIG. 10. As shown in the figure, the influence due to the spectrum discontinuity brings about the ripple of the group delay, but the influence on the band where dispersion compensation is performed is limited.

ＮＰＷＧは、高さがｈ３＝６μｍ、比屈折率差Δ＝０．６％となるコアが石英ガラスからなるクラッドに埋め込まれた導波路構造とした場合、波長１５５０ｎｍにおける等価屈折率と導波路の幅との関係は、図１３に示すようになる。なお、この際のクラッドの厚さは、コアに比べて十分大きいものとする。 When an NPWG has a waveguide structure in which a core having a height of h 3 = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass, the equivalent refractive index and waveguide at a wavelength of 1550 nm The relationship with the width of is as shown in FIG. In this case, the thickness of the clad is sufficiently larger than that of the core.

この導波路構造を用いた場合、図１０と図１１の各特性を実現するＮＰＷＧのコア幅分布は、図１４に示すように、光伝搬方向の中央部に幅変化の小さい分布領域があり、該中央部の両側に幅変化が中央部よりも大きな幅変化極大部を有するようになる。そのときのＮＰＷＧの等価屈折率の分布は、図１５に示すようになる。   When this waveguide structure is used, the core width distribution of the NPWG that realizes the characteristics of FIGS. 10 and 11 has a distribution region with a small width change at the center in the light propagation direction, as shown in FIG. A width change maximum portion having a width change larger than that of the center portion is provided on both sides of the center portion. The distribution of the equivalent refractive index of the NPWG at that time is as shown in FIG.

図１４の一部を拡大したものが図１６であり、また図１５の一部を拡大したものが図１７である。これらの図示のように、本実施例のＮＰＷＧは、分散補償する帯域の中心波長のスケールでは、周期が中心波長の約１／２になる周期構造となっている。すなわち、このＮＰＷＧは、中心波長のスケールでは周期構造で、波長よりずっと大きなスケールでは、逆問題で決まる非周期構造のような二階層構造となっている。   FIG. 16 is an enlarged view of a part of FIG. 14, and FIG. 17 is an enlarged view of a part of FIG. As shown in these figures, the NPWG according to the present embodiment has a periodic structure in which the period is approximately ½ of the center wavelength on the scale of the center wavelength of the band for dispersion compensation. In other words, this NPWG has a two-layered structure such as a periodic structure at the center wavelength scale and a non-periodic structure determined by an inverse problem at a scale much larger than the wavelength.

同じ材料の導波路構造を用いても、導波路全体の平均等価屈折率を示す参照屈折率n(o)を導波路の厚さや材料に応じて設定すれば、異なるコア幅をもつ導波路で同じ特性を実現することができる。図１８は、高いn(0)を使った場合の幅方向分布を示す。その時の導波路の等価屈折率の分布は、図１９に示すようになる。   Even if waveguide structures of the same material are used, if the reference refractive index n (o) indicating the average equivalent refractive index of the entire waveguide is set according to the thickness and material of the waveguide, waveguides having different core widths can be used. The same characteristics can be realized. FIG. 18 shows the distribution in the width direction when high n (0) is used. The distribution of the equivalent refractive index of the waveguide at that time is as shown in FIG.

コアとクラッドの材料は、石英ガラス系に限定されず、シリコン化合物、ポリマー等の光学分野等で従来周知の他の透明材料を用いることもできる。特に、屈折率の高い材料を用いれば、デバイスをさらに小さくし、伝送損失を下げることができる。   The material of the core and the clad is not limited to quartz glass, and other transparent materials that are conventionally known in the optical field such as silicon compounds and polymers can also be used. In particular, if a material having a high refractive index is used, the device can be further reduced and the transmission loss can be reduced.

波長領域［１５３４．２５ｎｍ〜１５６６．３１ｎｍ］において、分散量Ｄ＝−１０００ｐｓ／ｎｍ、分散に対する分散スロープの比ＲＤＳ＝０．００３４ｎｍ−１となる波長分散の補償を実現する分散補償デバイスを設計した。ただし、本実施例では、波長領域を周波数ｆが、１９３．４＋０．１ｎＴＨｚ≦ｆ≦１９３．５＋０．１ｎＴＨｚを満たす４０チャンネルに分けており、それぞれのチャンネル内で中心周波数を中心とした帯域０．０２ＴＨｚの領域でのみ分散補償を行っている。ここで、ｎは−２０≦ｎ≦１９を満たす整数を表す。なお、これらのチャンネルはＩＴＵグリッド間隔を満たす。本実施例の分散補償デバイスは、長さ５８ｋｍのＳ−ＳＭＦの残留分散を補償することができる。 In the wavelength region [153.25 nm to 1566.31 nm], a dispersion compensation device that realizes chromatic dispersion compensation with a dispersion amount D = −1000 ps / nm and a ratio of dispersion slope to dispersion RDS = 0.0036 nm −1 was designed. . However, in this embodiment, the wavelength region is divided into 40 channels satisfying the frequency f of 193.4 + 0.1 nTHz ≦ f ≦ 193.5 + 0.1 nTHZ, and the band 0. Dispersion compensation is performed only in the 02 THz region. Here, n represents an integer satisfying −20 ≦ n ≦ 19. These channels satisfy the ITU grid interval. The dispersion compensation device according to the present embodiment can compensate for the residual dispersion of the S-SMF having a length of 58 km.

図２０は、本実施例で作製した分散補償デバイスのＮＰＷＧのポテンシャル分布を表すグラフである。図中の横軸は、中心波長１５５０．１２ｎｍで規格された場所を表す。このポテンシャルを用いると、図２１に示す群遅延特性と図２２に示す反射率特性が得られる。両図には、設計に用いたスペクトルデータ（designed）と得られたスペクトルデータ（realized）が示されている。   FIG. 20 is a graph showing the NPWG potential distribution of the dispersion compensation device manufactured in this example. The horizontal axis in the figure represents a location standardized at a center wavelength of 1550.12 nm. When this potential is used, the group delay characteristic shown in FIG. 21 and the reflectance characteristic shown in FIG. 22 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

図２３は、図２１の一部拡大図であり、図示のように、スペクトル不連続による影響は、群遅延のリップルをもたらすが、分散補償を行う帯域内への影響は限定的となっている。   FIG. 23 is a partially enlarged view of FIG. 21, and as shown in the figure, the influence of the spectral discontinuity causes the ripple of the group delay, but the influence on the band where dispersion compensation is performed is limited. .

高さがｈ３＝６μｍ、比屈折率差Δ＝０．６％となるコアが石英ガラスからなるクラッドに埋め込まれた導波路構造とした場合、図２１と図２２の各特性を実現するＮＰＷＧのコア幅分布は、図２４に示すように、光伝搬方向の中央部に幅変化の小さい分布領域があり、該中央部の両側に幅変化が中央部よりも大きな幅変化極大部を有するようになる。そのときのＮＰＷＧの等価屈折率の分布は図２５に示すようになる。 In the case of a waveguide structure in which a core having a height of h 3 = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass, NPWG that realizes the characteristics shown in FIGS. As shown in FIG. 24, the core width distribution has a distribution region with a small width change at the center in the light propagation direction, and has a width change maximum portion where the width change is larger than the center at both sides of the center. become. The distribution of the equivalent refractive index of the NPWG at that time is as shown in FIG.

実施例１と比べると、補償の帯域（チャンネル）が増えた分、ポテンシャルの変動が実施例１より大きくなり、それを実現するＮＰＷＧのコア幅変化量も大きくなった。しかし、デバイスの長さは、実施例１と同じである。   Compared with the first embodiment, the amount of fluctuation in the potential is larger than that of the first embodiment, and the amount of change in the core width of the NPWG that realizes this is increased as the compensation band (channel) is increased. However, the length of the device is the same as in the first embodiment.

波長領域［１５３０．３３ｎｍ〜１５７０．４２ｎｍ］において、分散量Ｄ＝−１７００ｐｓ／ｎｍ、分散に対する分散スロープの比ＲＤＳ＝０．００３４ｎｍ−１となる波長分散の補償を実現する分散補償デバイスを設計した。ただし、本実施例では、波長領域を周波数ｆが、１９３．４＋０．１ｎＴＨｚ≦ｆ≦１９３．５＋０．１ｎＴＨｚを満たす５０チャンネルに分けており、それぞれのチャンネル内で中心周波数を中心とした帯域０．０２ＴＨｚの領域でのみ分散補償を行っている。ここで、ｎは−２５≦ｎ≦２４を満たす整数を表す。なお、これらのチャンネルはＩＴＵグリッド間隔を満たす。本実施例の分散補償デバイスは、長さ１００ｋｍのＳ−ＳＭＦの残留分散を補償することができ、Ｃバンドの全域をカバーすることができる。 In the wavelength region [1530.33 nm to 1570.42 nm], a dispersion compensation device that realizes chromatic dispersion compensation in which the dispersion amount D = −1700 ps / nm and the ratio of the dispersion slope to the dispersion RDS = 0.0036 nm −1 was designed. . However, in this embodiment, the wavelength region is divided into 50 channels in which the frequency f satisfies 193.4 + 0.1 nTHz ≦ f ≦ 193.5 + 0.1 nTHz, and the band 0. Dispersion compensation is performed only in the 02 THz region. Here, n represents an integer satisfying −25 ≦ n ≦ 24. These channels satisfy the ITU grid interval. The dispersion compensation device according to the present embodiment can compensate for the residual dispersion of the S-SMF having a length of 100 km and can cover the entire C band.

図２６は、本実施例で作製した分散補償デバイスのＮＰＷＧのポテンシャル分布を表すグラフである。図中の横軸は、中心波長１５５０．１２ｎｍで規格された場所を表す。このポテンシャルを用いると、図２７に示す群遅延特性と図２８に示す反射率特性が得られる。両図には、設計に用いたスペクトルデータ（designed）と得られたスペクトルデータ（realized）が示されている。   FIG. 26 is a graph showing the potential distribution of NPWG of the dispersion compensation device manufactured in this example. The horizontal axis in the figure represents a location standardized at a center wavelength of 1550.12 nm. When this potential is used, the group delay characteristic shown in FIG. 27 and the reflectance characteristic shown in FIG. 28 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

図２９は、図２７の一部拡大図であり、図示のように、スペクトル不連続による影響は、群遅延のリップルをもたらすが、分散補償を行う帯域内への影響は限定的となっている。   FIG. 29 is a partially enlarged view of FIG. 27. As shown in FIG. 29, the influence due to the spectrum discontinuity causes the ripple of the group delay, but the influence on the band where dispersion compensation is performed is limited. .

高さがｈ３＝６μｍ、比屈折率差Δ＝０．６％となるコアが石英ガラスからなるクラッドに埋め込まれた導波路構造とした場合、図２７と図２８の各特性を実現するＮＰＷＧのコア幅分布は、図３０に示すように、光伝搬方向の中央部に幅変化の小さい分布領域があり、該中央部の両側に幅変化が中央部よりも大きな幅変化極大部を有するようになる。そのときのＮＰＷＧの等価屈折率の分布は、図３１に示すようになる。 In the case of a waveguide structure in which a core having a height of h 3 = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass, NPWG that realizes the characteristics shown in FIGS. As shown in FIG. 30, the core width distribution of FIG. 30 has a distribution region with a small width change at the central portion in the light propagation direction, and has a width change maximum portion where the width change is larger than the central portion on both sides of the central portion. become. The distribution of the equivalent refractive index of NPWG at that time is as shown in FIG.

本発明の分散補償デバイスの主な構成要素である光導波路の一実施形態としてＮＰＷＧの構造を示す概略斜視図である。It is a schematic perspective view which shows the structure of NPWG as one Embodiment of the optical waveguide which is the main components of the dispersion compensation device of this invention. ＮＰＷＧにおいて、補償対象の波長帯域を複数のチャンネルに分けて、それぞれのチャンネルで分散補償を行う場合を示し、（Ａ）はＮＰＷＧの群遅延特性を示すグラフであり、また（Ｂ）は、コアにおける光の波長と反射との関係を模式的に示すグラフである。In NPWG, the wavelength band to be compensated is divided into a plurality of channels, and dispersion compensation is performed in each channel. (A) is a graph showing group delay characteristics of NPWG, and (B) is a core. It is a graph which shows typically the relationship between the wavelength of the light in, and reflection. 補償対象の波長帯域を複数のチャンネルに分けて、各チャンネル全体で分散補償を行う場合の最大遅延量を示すグラフである。It is a graph which shows the maximum amount of delay in the case where the wavelength band to be compensated is divided into a plurality of channels and dispersion compensation is performed for the entire channels. 本発明において、補償対象の波長帯域を複数のチャンネルに分けて、各チャンネルの波長領域のうちの部分的領域のみで分散補償を行う場合の最大遅延量を示すグラフである。In the present invention, the wavelength band to be compensated is divided into a plurality of channels, and is a graph showing the maximum delay amount when dispersion compensation is performed only in a partial region of the wavelength region of each channel. 本発明において、連続性を維持したチャンネルごとに分散補償するＮＰＷＧの群遅延特性を例示するグラフである。In the present invention, it is a graph illustrating a group delay characteristic of NPWG that performs dispersion compensation for each channel maintaining continuity. コアの幅の分布形状を例示する概略平面図である。It is a schematic plan view which illustrates the distribution shape of the core width. コアを蛇行状に設けた場合を例示する概略平面図である。It is a schematic plan view which illustrates the case where a core is provided in a meandering shape. 本発明の分散補償デバイスの一実施形態を示す構成図である。It is a block diagram which shows one Embodiment of the dispersion compensation device of this invention. 実施例１のＮＰＷＧのポテンシャル分布を示すグラフである。3 is a graph showing a potential distribution of the NPWG of Example 1. 実施例１のＮＰＷＧの群遅延特性を示すグラフである。3 is a graph showing group delay characteristics of the NPWG of Example 1. 実施例１のＮＰＷＧの反射率特性を示すグラフである。3 is a graph showing the reflectance characteristics of the NPWG of Example 1. 図１０の一部拡大図である。FIG. 11 is a partially enlarged view of FIG. 10. ｈ３＝６μｍ、比屈折率差Δ＝０．６％コアを使用した場合、波長１５５０ｎｍでの等価屈折率とコア幅の関係を示すグラフである。6 is a graph showing the relationship between the equivalent refractive index and the core width at a wavelength of 1550 nm when a core having h 3 = 6 μm and a relative refractive index difference Δ = 0.6% is used. 実施例１のＮＰＷＧのコア幅分布を示すグラフである。3 is a graph showing a core width distribution of the NPWG of Example 1. 実施例１のＮＰＷＧの等価屈折率の分布を示すグラフである。3 is a graph showing an equivalent refractive index distribution of the NPWG of Example 1. 図１４の一部拡大図である。FIG. 15 is a partially enlarged view of FIG. 14. 図１５の一部拡大図である。FIG. 16 is a partially enlarged view of FIG. 15. 実施例１のＮＰＷＧで高い初期屈折率を用いた場合のＮＰＷＧのコア幅の分布を示すグラフである。6 is a graph showing a core width distribution of an NPWG when a high initial refractive index is used in the NPWG of Example 1. FIG. 実施例１のＮＰＷＧで高い初期屈折率を用いた場合のＮＰＷＧの等価屈折率分布を示すグラフである。3 is a graph showing an equivalent refractive index distribution of NPWG when a high initial refractive index is used in the NPWG of Example 1. 実施例２のＮＰＷＧのポテンシャル分布を示すグラフである。6 is a graph showing a potential distribution of NPWG in Example 2. 実施例２のＮＰＷＧの群遅延特性を示すグラフである。10 is a graph showing group delay characteristics of the NPWG of Example 2. 実施例２のＮＰＷＧの反射率特性を示すグラフである。6 is a graph showing the reflectance characteristics of the NPWG of Example 2. 図２１の一部拡大図である。FIG. 22 is a partially enlarged view of FIG. 21. 実施例２のＮＰＷＧのコア幅分布を示すグラフである。6 is a graph showing a core width distribution of the NPWG of Example 2. 実施例２のＮＰＷＧの等価屈折率の分布を示すグラフである。6 is a graph showing an equivalent refractive index distribution of the NPWG of Example 2. 実施例３のＮＰＷＧのポテンシャル分布を示すグラフである。10 is a graph showing a potential distribution of NPWG in Example 3. 実施例３のＮＰＷＧの群遅延特性を示すグラフである。6 is a graph showing group delay characteristics of the NPWG of Example 3. 実施例３のＮＰＷＧの反射率特性を示すグラフである。6 is a graph showing the reflectance characteristics of the NPWG of Example 3. 図２７の一部拡大図である。It is a partially enlarged view of FIG. 実施例３のＮＰＷＧのコア幅分布を示すグラフである。6 is a graph showing a core width distribution of the NPWG of Example 3. 実施例３のＮＰＷＧの等価屈折率の分布を示すグラフである。10 is a graph showing an equivalent refractive index distribution of the NPWG of Example 3.

符号の説明Explanation of symbols

１０…ＮＰＷＧ、１１…コア、１２…クラッド、１３…反射端、１４…透過端、１５…サーキュレータ、１６…無反射終端、２０…分散補償デバイス。   DESCRIPTION OF SYMBOLS 10 ... NPWG, 11 ... Core, 12 ... Cladding, 13 ... Reflection end, 14 ... Transmission end, 15 ... Circulator, 16 ... Non-reflection termination, 20 ... Dispersion compensation device

Claims (16)

クラッドに埋め込まれたコアの物理的寸法を変えることによりコアの等価屈折率が光伝搬方向にわたって不均一に変化する光導波路を反射型の波長分散補償手段として有し、
前記光導波路は、分散補償する波長領域が複数のチャンネルに区切られ、
各チャンネルの波長領域のうちの部分的領域のみで分散が補償される分散補償特性を有しており、
分散が補償される前記部分的領域以外の前記チャンネルの波長領域では波長に対する群遅延の分布が平坦であることを特徴とする光導波路型波長分散補償デバイス。 As a reflection-type wavelength dispersion compensation means, an optical waveguide in which the equivalent refractive index of the core changes nonuniformly in the light propagation direction by changing the physical dimensions of the core embedded in the clad,
In the optical waveguide, a wavelength region for dispersion compensation is divided into a plurality of channels,
It has a dispersion compensation characteristic in which dispersion is compensated only in a partial region of the wavelength region of each channel ,
An optical waveguide type chromatic dispersion compensation device , wherein a distribution of group delay with respect to a wavelength is flat in a wavelength region of the channel other than the partial region in which dispersion is compensated. 前記チャンネルの波長領域は、分散が補償される前記部分的領域以外の波長領域の、波長に対する群遅延の分布及び反射率の分布が、それと近接した分散補償を行う前記部分的領域の群遅延の分布及び反射率の分布とそれぞれ連続し、且つこの近接した分散補償を行う部分的領域から最も離れた波長で前記各分布が隣接するチャンネルの各分布と不連続となる分布構造を有することを特徴とする請求項１に記載の光導波路型波長分散補償デバイス。 Wavelength region of the channel, the dispersion of wavelength region other than the partial area to be compensated, the distribution of the group delay distribution and reflectance with respect to wavelength, the same group delay of the partial area to be close to each dispersion compensation A distribution structure in which each distribution is discontinuous with each distribution of adjacent channels at a wavelength most distant from a partial region where dispersion compensation is performed, which is continuous with the distribution of the distribution and the reflectance. The optical waveguide type chromatic dispersion compensating device according to claim 1 . 前記コアの幅が光伝搬方向にわたって不均一に分布していることを特徴とする請求項１又は２に記載の光導波路型波長分散補償デバイス。 3. The optical waveguide type chromatic dispersion compensating device according to claim 1, wherein the width of the core is unevenly distributed in the light propagation direction. 前記コアの幅が、コア中心から幅方向両側が対称となるように光伝搬方向にわたって不均一に分布していることを特徴とする請求項３に記載の光導波路型波長分散補償デバイス。 4. The optical waveguide type chromatic dispersion compensating device according to claim 3 , wherein the width of the core is unevenly distributed over the light propagation direction so that both sides in the width direction are symmetrical from the center of the core. 前記コアの幅が、コア中心から幅方向両側が非対称となるように光伝搬方向にわたって不均一に分布していることを特徴とする請求項３に記載の光導波路型波長分散補償デバイス。 4. The optical waveguide type chromatic dispersion compensation device according to claim 3 , wherein the width of the core is non-uniformly distributed over the light propagation direction so as to be asymmetric on both sides in the width direction from the core center. 前記コアの幅が、コア中心から幅方向両側のうち一方の側のみが光伝搬方向にわたって不均一に分布していることを特徴とする請求項３に記載の光導波路型波長分散補償デバイス。 4. The optical waveguide type chromatic dispersion compensation device according to claim 3 , wherein the width of the core is non-uniformly distributed over the light propagation direction only on one side in the width direction from the core center. 5. 前記コアが、前記光導波路内に直線状に設けられていることを特徴とする請求項１〜６のいずれかに記載の光導波路型波長分散補償デバイス。 Wherein the core, the optical waveguide-type wavelength dispersion compensation device according to any one of claims 1 to 6, characterized in that provided linearly in the optical waveguide. 前記コアが、前記光導波路内に蛇行状に設けられていることを特徴とする請求項１〜７のいずれかに記載の光導波路型波長分散補償デバイス。 Wherein the core, according to claim 1 to 7 optical waveguide-type wavelength dispersion compensation device according to any of characterized in that provided in a meandering shape in the optical waveguide. 前記コアの幅が、光伝搬方向の中央部に幅変化の小さい分布領域があり、該中央部の両側に幅変化が中央部よりも大きな幅変化極大部を有することを特徴とする請求項１〜８のいずれかに記載の光導波路型波長分散補償デバイス。 2. The core has a distribution region having a small width change at a central portion in a light propagation direction, and has a width change maximum portion having a width change larger than that of the central portion on both sides of the central portion. The optical waveguide type chromatic dispersion compensating device according to any one of to 8 . 前記光導波路の透過端が無反射終端で終端され、反射端でサーキュレータ又は方向性結合器を介して出力を取り出すように構成されたことを特徴とする請求項１〜９のいずれかに記載の光導波路型波長分散補償デバイス。 Transmission end of the optical waveguide is terminated in reflection-free termination, according to any one of claims 1 to 9, characterized in that it is configured to retrieve the output via the circulator or a directional coupler at the reflecting end Optical waveguide type chromatic dispersion compensation device. 前記光導波路は、所定の波長帯域において、所定の長さの被補償光ファイバの波長分散を打ち消す分散補償特性を有することを特徴とする請求項１〜１０のいずれかに記載の光導波路型波長分散補償デバイス。 The optical waveguide wavelength according to any one of claims 1 to 10 , wherein the optical waveguide has a dispersion compensation characteristic that cancels chromatic dispersion of a compensated optical fiber having a predetermined length in a predetermined wavelength band. Dispersion compensation device. 前記光導波路は、中心波長λｃが１２８０ｎｍ≦λｃ≦１３２０ｎｍ及び１４９０ｎｍ≦λｃ≦１６１３ｎｍの範囲、動作帯域ΔＢＷが０．１ｎｍ≦ΔＢＷ≦６０ｎｍの範囲において、分散Ｄが−３０００ｐｓ／ｎｍ≦Ｄ≦３０００ｐｓ／ｎｍの範囲、分散に対する分散スロープの比ＲＤＳが−０．１ｎｍ−１≦ＲＤＳ≦０．１ｎｍ−１の範囲の特性を有することを特徴とする請求項１〜１１のいずれかに記載の光導波路型波長分散補償デバイス。 The optical waveguide has a dispersion D of −3000 ps / nm ≦ D when the center wavelength λ c is in the range of 1280 nm ≦ λ c ≦ 1320 nm and 1490 nm ≦ λ c ≦ 1613 nm, the operating band ΔBW is in the range of 0.1 nm ≦ ΔBW ≦ 60 nm. ≦ 3000 ps / nm range, according to any one of claims 1 to 11, the ratio RDS dispersion slope is characterized by having the properties of a range of -0.1nm-1 ≦ RDS ≦ 0.1nm- 1 for dispersion Optical waveguide type chromatic dispersion compensation device. 前記光導波路の光伝搬方向にわたるコアの等価屈折率分布が、Ｚａｋｈａｒｏｖ−Ｓｈａｂａｔ方程式において、反射係数のスペクトルデータからポテンシャル関数を数値的に導く逆散乱問題として解き、所望の反射スペクトルを実現するためのポテンシャルを推測する設計法で設計されることを特徴とする請求項１〜１２のいずれかに記載の光導波路型波長分散補償デバイス。 The equivalent refractive index distribution of the core over the light propagation direction of the optical waveguide is solved as an inverse scattering problem that numerically derives a potential function from the spectral data of the reflection coefficient in the Zakharov-Shabat equation, and realizes a desired reflection spectrum. the optical waveguide-type wavelength dispersion compensation device according to any one of claims 1 to 12, characterized in that it is designed in the design process to infer potential. 前記光導波路の光伝搬方向にわたるコアの等価屈折率分布が、光導波路の前方及び後方に伝搬する電力波振幅なる変数を導入した波動方程式より、光導波路の等価屈折率の対数の微分から導かれるポテンシャルを有するＺａｋｈａｒｏｖ−Ｓｈａｂａｔ方程式に帰着させ、反射係数のスペクトルデータからポテンシャル関数を数値的に導く逆散乱問題として解き、所望の反射スペクトルを実現するためのポテンシャルを推測し、それに基づいて等価屈折率を求め、予め求められた、所定のコアの厚さとコア-クラッド間の比屈折率差を持ったコアにおける等価屈折率とコア寸法との関係から、光導波路の光伝搬方向にわたるコア寸法を算出して設計されることを特徴とする請求項１３に記載の光導波路型波長分散補償デバイス。 The equivalent refractive index distribution of the core over the light propagation direction of the optical waveguide is derived from the logarithmic derivative of the equivalent refractive index of the optical waveguide from the wave equation that introduces a variable of the power wave amplitude propagating forward and backward of the optical waveguide. Reduced to the Zakharov-Shabat equation with potential, solved as an inverse scattering problem that numerically derives the potential function from the spectral data of the reflection coefficient, estimated the potential for realizing the desired reflection spectrum, and based on it, the equivalent refractive index Calculate the core dimensions over the optical propagation direction of the optical waveguide based on the relationship between the equivalent refractive index and core dimensions of the core with a predetermined core thickness and core-clad relative refractive index difference. The optical waveguide type chromatic dispersion compensation device according to claim 13 , wherein the device is designed as follows. 前記光導波路の光伝搬方向にわたるコアの等価屈折率分布は、分散補償する帯域の中心波長のスケールではほぼ周期構造であり、中心波長より大きいスケールでは、前記逆散乱問題で決まる非周期構造の二階層構造を有することを特徴とする請求項１３又は１４に記載の光導波路型波長分散補償デバイス。 The equivalent refractive index distribution of the core over the light propagation direction of the optical waveguide has a substantially periodic structure on the scale of the center wavelength of the band for dispersion compensation, and on the scale larger than the center wavelength, the equivalent refractive index distribution of the non-periodic structure determined by the inverse scattering problem. The optical waveguide type chromatic dispersion compensating device according to claim 13 or 14 , wherein the optical waveguide type chromatic dispersion compensating device has a hierarchical structure. 光導波路の下クラッド層を設け、
次いで、前記下クラッド層上に、下クラッド層よりも屈折率の大きいコア層を設け、
次いで、前記コア層に、コアの等価屈折率が光伝搬方向にわたって不均一に変化するように設計された所定のコア形状を残し、それ以外の部分を除去する加工を施してコアを形成し、
次いで、前記コアを覆うクラッドを設けることによって光導波路を製造し、請求項１〜１５のいずれかに記載の光導波路型波長分散補償デバイスを製造することを特徴とする光導波路型波長分散補償デバイスの製造方法。 Provide a lower cladding layer of the optical waveguide,
Next, a core layer having a refractive index larger than that of the lower cladding layer is provided on the lower cladding layer,
Next, the core layer is left with a predetermined core shape designed so that the equivalent refractive index of the core varies nonuniformly in the light propagation direction, and a core is formed by removing the other portions.
Next, an optical waveguide is manufactured by providing a clad covering the core, and the optical waveguide type chromatic dispersion compensation device according to any one of claims 1 to 15 is manufactured. Manufacturing method.
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