WO2009081905A1 - Optical waveguide type wavelength dispersion compensation device and method for manufacturing the device - Google Patents

Abstract

An optical waveguide type wavelength dispersion compensation device is provided with an optical waveguide as a reflection type wavelength dispersion compensation means, wherein the optical waveguide is configured to change a physical size of a core embedded in a clad, so that an equivalent refractive index of the core changes unevenly over a light traveling direction. A dispersion compensating wavelength region of the optical waveguide is divided into a plurality of channels and the optical waveguide has a dispersion compensation characteristic in which the dispersion is compensated within the wavelength region of the channels.

Description

Optical waveguide type chromatic dispersion compensation device and manufacturing method thereof

The present invention relates to a small-sized optical waveguide type chromatic dispersion compensation device that compensates for chromatic dispersion of an optical fiber and a method for manufacturing the same. This device can be used for an optical fiber communication network or the like.
This application claims priority based on Japanese Patent Application No. 2007-331176 for which it applied to Japan on December 21, 2007, and uses the content here.

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 an optical fiber as the transmission line that has as little chromatic dispersion as possible in the transmission band, while preventing chromatic dispersion from becoming zero in order to suppress nonlinear effects. However, optical fibers that have already been laid in a wide range are often used in a wavelength region with large dispersion.
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 fiber amplifier. Used in belts. 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-DSF) 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.

Various techniques are used for dispersion compensation. Among these, dispersion compensation using a dispersion compensation fiber (DCF: Dispersion Compensation Fiber) is the most practical technique (see, for example, Patent Documents 1 and 2). In the DCF, the refractive index distribution of the optical fiber is controlled so that a desired dispersion compensation amount can be obtained. However, the DCF usually requires the same length as the optical fiber to be compensated. Therefore, when this DCF 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.

Fiber Bragg Grating (FBG) is 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 refractive index. Furthermore, since there is a limit to the change in the refractive index of the fiber, there is a limit to the dispersion compensation characteristics that can be realized. In addition, there is a limit to miniaturization and mass production of devices using FBG.

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 overlapped at one place (see, for example, Patent Document 4). By using this, the required fiber length is shortened. However, in this prior art, since it is designed to simply superimpose a plurality of FBGs, the structure of each channel approaches and affects each channel characteristic. Therefore, there is a limit to the dispersion compensation 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.

An optical planar circuit (PLC: Planar Lightwave Circuit) can perform dispersion compensation 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. Therefore, the amount of dispersion to be realized is limited.

There is also considered a mechanism in which demultiplexing is performed with an arrayed waveguide grating (AWG), a path difference is added for each channel, a delay time is adjusted, and then re-multiplexing with a collimator lens (for example, Patent Document 5). reference). However, this method not only has a complicated structure and is difficult to manufacture, but also requires a large space.

A VIPA (Virtually Imaged Phased Array) type dispersion compensator is a dispersion compensation device composed of a wavelength dispersion element (VIPA plate) in which a reflection film is coated on both surfaces of a thin plate and a reflection mirror (for example, see Patent Document 6). ). This device adjusts the dispersion with a three-dimensional structure. Therefore, it is structurally complicated 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 2005-275101 A

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 is limited in the 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 a lattice-type PLC has a small amount of dispersion compensation that can be realized.
5: The PLC using AWG 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.

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 reduced in size, has excellent dispersion compensation characteristics, can be easily manufactured, and can be manufactured at low cost.

The present invention employs the following means in order to solve the above problems and achieve the object.
(1) The optical waveguide type chromatic dispersion compensation device of the present invention is an optical waveguide in which the 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. The optical waveguide has a dispersion compensation characteristic in which a wavelength region for dispersion compensation is divided into a plurality of channels, and dispersion is compensated within the wavelength region of these channels.

(2) It is preferable that the width of the core is unevenly distributed over the light propagation direction.

(3) It is preferable that the width of the core is unevenly distributed over the light propagation direction so that both sides of the core in the width direction are symmetrical from the center of the core.

(4) It is preferable that the width of the core is unevenly distributed in the light propagation direction so that both sides of the core in the width direction are asymmetric from the center of the core.

(5) It is preferable that the width of the core is unevenly distributed over the light propagation direction only on one side of the core in the width direction from the center of the core.

(6) It is preferable that the core is linearly provided in the optical waveguide.

(7) It is preferable that the core is provided in a meandering manner in the optical waveguide.

(8) One end of the optical waveguide is a transmissive end, the other end of the optical waveguide is a reflective end; the transmissive end is terminated at a non-reflective end; and a circulator or a directional coupler is used at the reflective end. Preferably, the light output is taken out.

(9) 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.

(10) The optical waveguide has a dispersion D of −3000 ps / nm ≦ D ≦ 3000 ps / with a center wavelength λ _{c in} the range of 1490 nm ≦ λ _c ≦ 1613 nm and an operating band ΔBW in the range of 0.1 nm ≦ ΔBW ≦ 60 nm. nm range, the ratio RDS dispersion slope for the dispersion is preferably has a characteristic in the range of -0.1nm ^-1 ≦ RDS ≦ 0.1nm ^-1.

(11) 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 using the Zakharov-Shabat equation; It is preferably designed by a design method that estimates the potential for realizing a desired reflection spectrum from the values obtained in the scattering problem.

(12) The equivalent refractive index distribution of the core across the light propagation direction of the optical waveguide is obtained by using a wave equation that introduces a variable that is an amplitude of a power wave propagating forward and backward of the optical waveguide. It is reduced to the Zakharov-Shabat equation having a potential derived from the logarithmic derivative of the refractive index, and is solved as an inverse scattering problem that numerically derives the potential function from the spectral data of the reflection coefficient; Estimating a potential for realizing a desired reflection spectrum; obtaining an equivalent refractive index based on this potential; a predetermined thickness of the core, an equivalent refractive index, a dimension of the core, which are obtained in advance; From the above relationship, it is preferable to calculate the width distribution of the core over the light propagation direction of the optical waveguide.

(13) The equivalent refractive index distribution of the core across the light propagation direction of the optical waveguide has a substantially periodic structure at the scale of the center wavelength of the band for dispersion compensation, and is determined by the inverse scattering problem at a scale larger than the center wavelength. It preferably has a two-layer structure of an aperiodic structure.

(14) In the method of manufacturing an optical waveguide type chromatic dispersion compensation device of the present invention, a lower cladding layer of an optical waveguide is provided; and then a core layer having a refractive index larger than that of the lower cladding layer is provided on the lower cladding layer; Next, a predetermined core shape designed so that the equivalent refractive index of the core varies non-uniformly in the light propagation direction is left on the core layer, and a core is formed by removing the other portions; Next, it is preferable to manufacture an optical waveguide by providing a clad covering the core.

The optical waveguide type chromatic dispersion compensation device described in (1) above has an optical waveguide in which the equivalent refractive index of the core embedded in the clad varies nonuniformly in the light propagation direction as the reflective chromatic dispersion compensation means. Therefore, the size can be reduced as compared with the prior art using a dispersion compensating fiber and the installation space can be reduced.
In addition, the optical waveguide type chromatic dispersion compensation device described in the above (1) 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 described in the above (1) 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 described in (1) has a dispersion compensation characteristic in which a wavelength region for dispersion compensation is divided into a plurality of channels, and dispersion is compensated within the wavelength region of each channel. . Therefore, the length of the required optical waveguide is shortened, the device can be miniaturized, and the transmission loss of the optical waveguide can be reduced.

According to the method for manufacturing an optical waveguide type chromatic dispersion compensation device described in (14) above, a small dispersion compensation device having excellent dispersion compensation characteristics as described above can be efficiently manufactured at low cost.

FIG. 1 is a schematic perspective view showing the structure of an NPWG used in the dispersion compensation device of the present invention. FIG. 2A is a graph showing group delay characteristics of the NPWG when the NPWG performs dispersion compensation for the entire wavelength band to be compensated. FIG. 2B is a diagram schematically illustrating the relationship between the wavelength of light and reflection at the core of the NPWG when the NPWG performs dispersion compensation for the entire wavelength band to be compensated. FIG. 3A is a graph showing group delay characteristics of the NPWG when the NPWG divides the wavelength band to be compensated into a plurality of channels and performs dispersion compensation on each channel. FIG. 3B is a diagram schematically showing the relationship between the wavelength and reflection of light in the NPWG core when the NPWG divides the wavelength band to be compensated into a plurality of channels and performs dispersion compensation in each channel. is there. FIG. 4A is a schematic plan view showing an example of a core width distribution shape. FIG. 4B is a schematic plan view showing a modification of the distribution shape of the core width. FIG. 5 is a schematic plan view illustrating the case where the cores are provided in a meandering manner. FIG. 6 is a block diagram showing an embodiment of the dispersion compensation device of the present invention. FIG. 7 is a graph showing the potential distribution of the NPWG of Example 1. FIG. 8 is a graph showing the group delay characteristics of the NPWG according to the first embodiment. FIG. 9 is a graph showing the reflectance characteristics of the NPWG of Example 1. FIG. 10 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. FIG. 11 is a graph showing the core width distribution of the NPWG of Example 1. FIG. 12 is a graph showing the distribution of the equivalent refractive index of the NPWG of Example 1. FIG. 13 is a partially enlarged view of FIG. FIG. 14 is a partially enlarged view of FIG. FIG. 15 is a graph showing the distribution of the core width of the NPWG when a high initial refractive index is used in the NPWG of Example 1. FIG. 16 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. FIG. 17 is a graph showing the potential distribution of the NPWG of Example 2. FIG. 18 is a graph showing the group delay characteristics of the NPWG of the same example. FIG. 19 is a graph showing the reflectance characteristics of the NPWG of the same example. FIG. 20 is a graph showing the core width distribution of the NPWG of the same example. FIG. 21 is a graph showing the distribution of the equivalent refractive index of the NPWG of the same example. FIG. 22 is a graph showing the potential distribution of the NPWG of Example 3. FIG. 23 is a graph showing the group delay characteristics of the NPWG of the same example. FIG. 24 is a graph showing the reflectance characteristics of the NPWG of the same example. FIG. 25 is a graph showing the core width distribution of the NPWG of the same example. FIG. 26 is a graph showing an equivalent refractive index distribution of the NPWG of the same example. FIG. 27 is a graph showing the potential distribution of the NPWG of Example 4. FIG. 28 is a graph showing the group delay characteristics of the NPWG of the same example. FIG. 29 is a graph showing the reflectance characteristics of the NPWG of this example. FIG. 30 is a graph showing the core width distribution of the NPWG of the same example. FIG. 31 is a graph showing an equivalent refractive index distribution of the NPWG of the same example. FIG. 32 is a graph showing the potential distribution of the NPWG of Example 5. FIG. 33 is a graph showing the group delay characteristic of the NPWG of the same example. FIG. 34 is a graph showing the reflectance characteristics of the NPWG of this example. FIG. 35 is a graph showing the core width distribution of the NPWG of the same example. FIG. 36 is a graph showing an equivalent refractive index distribution of the NPWG of the same example. FIG. 37 is a graph showing the potential distribution of the NPWG of Example 6. FIG. 38 is a graph showing the group delay characteristics of the NPWG of the same example. FIG. 39 is a graph showing the reflectance characteristics of the NPWG of this example. FIG. 40 is a graph showing the core width distribution of the NPWG of the same example. FIG. 41 is a graph showing an equivalent refractive index distribution of the NPWG of the same example. FIG. 42 is a graph showing the potential distribution of the NPWG of Example 7. FIG. 43 is a graph showing the group delay characteristics of the NPWG of the same example. FIG. 44 is a graph showing the reflectance characteristics of the NPWG of the same example. FIG. 45 is a graph showing the core width distribution of the NPWG of the same example. FIG. 46 is a graph showing an equivalent refractive index distribution of the NPWG of the same example. FIG. 47 is a graph showing the potential distribution of the NPWG of Example 8. FIG. 48 is a graph showing the group delay characteristics of the NPWG of the same example. FIG. 49 is a graph showing the reflectance characteristics of the NPWG of this example. FIG. 50 is a graph showing the core width distribution of the NPWG of the same example. FIG. 51 is a graph showing an equivalent refractive index distribution of the NPWG of the same example. FIG. 52 is a graph showing the potential distribution of the NPWG of Example 9. FIG. 53 is a graph showing the group delay characteristics of the NPWG of the same example. FIG. 54 is a graph showing the reflectance characteristics of the NPWG of this example. FIG. 55 is a graph showing the core width distribution of the NPWG of the same example. FIG. 56 is a graph showing an equivalent refractive index distribution of the NPWG of the same example.

Explanation of symbols

10 NPWG
11 Core 12 Cladding 13 Reflecting end 14 Transmitting end 15 Circulator 16 Non-reflective termination 20 Dispersion compensation device

The dispersion compensation device of the present invention has an optical waveguide in which the equivalent refractive index of the core embedded in the clad varies nonuniformly in the light propagation direction as a reflection type chromatic dispersion compensation means. Here, non-uniform means that the physical dimension changes with the traveling direction of the waveguide.
This optical waveguide has a dispersion compensation characteristic in which a wavelength region for dispersion compensation is divided into a plurality of channels, and dispersion is compensated within the wavelength region of each channel.

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.
As shown in FIG. 6, for example, the dispersion compensation device of the present invention is generally configured by an optical waveguide 10 and a circulator 15 connected to the reflection end 13 side. The transmission end 14 of the optical waveguide 10 is a non-reflection terminal 16. The circulator 15 is connected to a compensated optical fiber (not shown) on its input side (input). A downstream optical fiber is connected to the output side (output) of the circulator 15. This downstream optical fiber 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 is reflected by entering the optical waveguide 10, and the reflected wave passes through the circulator 15. Is output.

FIG. 1 is a schematic perspective view showing an embodiment of an optical waveguide 10. In FIG. 1, reference numeral 10 denotes an optical waveguide, 11 denotes a core, and 12 denotes a cladding. The optical waveguide 10 of the present embodiment is a non-uniform width core in which the width w of the core 11 is changed over the longitudinal direction (z) as means for changing the equivalent refractive index of the core 11 non-uniformly along the light propagation direction. 11. As this optical waveguide 10, it is preferable to use a planar waveguide (Non-uniform Planar WaveGide; hereinafter referred to as NPWG).

The NPWG 10 of the present embodiment has a core 11 in the clad 12. The core 11, as shown in FIG. 1, has a constant height h _3. Further, the width w of the core 11 varies non-uniformly in the longitudinal direction (z) direction, and changes the local equivalent refractive index of the propagation mode of the waveguide. Due to this change in refractive index, the NPWG 10 is provided with a reflective chromatic dispersion compensation function.

As the NPWG 10, a quartz glass material can be used. 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.

The operational principle of the NPWG 10 is similar to the FBG grating at first glance. However, regarding the change of the equivalent refractive index, the refractive index of the core medium is changed in the FBG, whereas in the NPWG 10 of the present embodiment, the equivalent refractive index is changed by changing the width of the core 11 along the longitudinal direction. It is changing. Thus, regarding the change of the equivalent refractive index, the operating principle is completely different between the two.
In the NPWG 10, 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 in the FBG, and fine and accurate control is easy.
Since the structure of the NPWG 10 is planar, it can be manufactured in a large amount by a known manufacturing process, and the cost can be reduced.

Such a dispersion compensation device can also be designed to compensate for the dispersion in the entire band to be subjected to dispersion compensation, as shown in FIGS. 2A and 2B. FIG. 2A is a graph showing group delay (Group delay) characteristics of the NPWG 10. FIG. 2B is a diagram schematically illustrating the relationship between the wavelength of light and the reflection in the core 11.

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. 2A) within the band. As shown in FIGS. 2A and 2B, the NPWG reflects a signal in a wavelength band with a fast delay (λ ₁ in FIGS. 2A and 2B) in front of the device, and a wavelength band with a slow delay (λn in FIGS. 2A and 2B). ) Is reflected in 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).

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.
As described above, when dispersion is compensated for the entire band to be subjected to dispersion compensation, if the absolute delay amount is high, the required device length becomes long.

As shown in FIGS. 2A and 2B, the present invention does not perform dispersion compensation in the entire area to be subjected to dispersion compensation, but divides the area to be compensated into a plurality of channels as shown in FIGS. 3A and 3B. Thus, a method of performing dispersion compensation in each channel is used. FIG. 3A is a graph showing group delay characteristics of the NPWG 10. FIG. 3B is a diagram schematically illustrating the relationship between the wavelength of light and the reflection in the core 11. As shown in FIG. 3A, in the NPWG used in the dispersion compensation device of the present invention, the region to be compensated is divided into a plurality of channels such as channels of wavelengths λ ₁₁ to λ ₁₂ and channels of wavelengths λ ₂₁ to λ _22. Dispersion compensation is performed in each channel.
That is, 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 the required compensation group delay is indicated within each wavelength band. Is to set. By using this method, compared to the case shown in FIGS. 2A and 2B, the required waveguide length is shortened, and not only the device is reduced, but also the loss of the waveguide can be reduced.

In the above embodiment, the NPWG 10 having a structure in which the core 11 in which the height (thickness) is constant and the width varies non-uniformly in the longitudinal direction is embedded in the clad 11, but the optical fiber used in the present invention is exemplified. The waveguide is not limited to this example, and various modifications can be made.
For example, as shown in FIG. 4A, the core 11 may have a width distribution that is unevenly distributed in the light propagation direction so that both sides of the core 11 in the width direction are symmetrical. Further, as shown in FIG. 4B, a structure in which the both sides in the width direction of the core 11 from the center of the core 11 are asymmetrically distributed in the light propagation direction may be used.
As shown in FIG. 1, the core 11 may have a structure in which the core 11 is provided in a meandering manner as shown in FIG. 5 in addition to a structure in which the core 11 is provided linearly along the longitudinal direction (z) of the NPWG 10. By adopting such a structure in which the core 11 is provided in a meandering manner, the NPWG 10 can be further downsized.

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 is processed so as to leave a predetermined core shape designed so that the equivalent refractive index of the core varies nonuniformly in the light propagation direction and remove the other portions. 11 is formed.
(D) Next, the cladding 12 covering the core 11 is provided, and the NPWG 10 is manufactured.

Regarding the formation of the core 11 of the NPWG 10 (step (c) described above), the distribution of the core width can be designed by using the inverse scattering problem method for obtaining a necessary width distribution from a desired reflection spectrum.

First, the electromagnetic field propagating to the NPWG 10 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 electromagnetic field propagating to the NPWG 10 by the Maxwell equation is expressed by the following expressions (1) and (2).

In the above formulas (1) and (2), 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)

The power wave amplitude A ₊ (z) propagating in front of z and the power wave amplitude A ₋ (z) propagating in the rear of z are defined in the above equations (1) and (2), respectively. Introduce. However, Z ₀ = √μ ₀ / ε ₀ represents the impedance in vacuum, and n ₀ represents the reference refractive index. From these variables, the following equations (5) and (6) are derived, respectively:

Here, c represents the speed of light in vacuum.

These equations (5) and (6) are expressed by the following equation (7)

If the variable conversion is performed in, the result is reduced to the Zakharov-Shabat equation shown in the following equations (8) and (9):

However, ω ₀ represents the reference angular frequency.

These Zakharov-Shabat equations can be solved as inverse scattering problems. That is, the following formula (10)

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). If this is applied to the above-mentioned inverse scattering 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.

If the potential u (x) is obtained, the local equivalent refractive index n (x) can be obtained by the following equation (11).

Furthermore, from the relationship between the thickness of the core of the waveguide to be actually manufactured and the equivalent refractive index with respect to the core width, which is obtained from the refractive index of the core and the refractive index of the cladding, at a predetermined position in the light propagation direction. The core width w (x) is obtained.

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.
When this method is used, interference between channels that occurs in a method of superimposing FBGs (see, for example, Patent Document 4) does not occur because the design method is considered. Further, the NPWG obtained by this design has a structure different from that disclosed in Patent Document 4.

Thus, when forming the core 11 of the NPWG 10, it is preferable to form the core 11 by photolithography using a mask having the shape of the core width w (x) described above. Materials and procedures used for this photolithography method can be implemented using materials and procedures used for photolithography methods well known in the field of semiconductor manufacturing. The cladding layer or core layer can be formed by using a well-known film forming technique used in the production of a general optical waveguide.

The dispersion compensation device 20 of the present invention, after manufacturing the NPWG 10 as described above, terminates the transmissive end 14 of the NPWG 10 with a non-reflection termination 16. Further, a circulator 15 or a directional coupler is connected to the reflection end 13 of the NPWG 10. Thus, the dispersion compensation device 20 shown in FIG. 6 is obtained.

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.

<Example 1>
In the wavelength region [1546.12 nm to 1554.13 nm], a dispersion compensation device that realizes chromatic dispersion compensation with a dispersion amount D = −1700 ps / nm and a ratio of dispersion slope to dispersion RDS = 0.0036 nm ⁻¹ was designed. . At this time, the NPWG was designed so that the wavelength region for dispersion compensation is divided into 10 channels satisfying the frequency f of 193.4 + 0.1 nTHz ≦ f ≦ 193.5 + 0.1 nTHz. Here, n represents an integer satisfying −5 ≦ n ≦ 4. In this dispersion compensation device, dispersion compensation is performed in each channel. That is, in Example 1, the reflection spectrum shown by the dispersion compensation device is divided into the 10 channels, and the width of the waveguide is designed by setting so as to compensate for the dispersion within each wavelength band. . Each of these channels fills the ITU grid interval. The dispersion compensation device of this embodiment can compensate for the residual dispersion of S-SMF having a length of 100 km.

FIG. 7 is a graph showing the potential distribution of the 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 distribution is used as described above, the group delay characteristic shown in FIG. 8 and the reflectance characteristic shown in FIG. 9 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

The NPWG of this example has a waveguide structure in which a core having a height h ₃ = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass. In this waveguide structure, the relationship between the equivalent refractive index at a wavelength of 1550 nm and the width of the waveguide is as shown in FIG. In this case, the thickness of the clad is sufficiently larger than that of the core.

When this waveguide structure is used, the width distribution of the core of the NPWG realizing the characteristics shown in FIGS. 8 and 9 is as shown in FIG. The distribution of the equivalent refractive index of the NPWG at that time is as shown in FIG.

FIG. 13 shows an enlarged view of a part of FIG. FIG. 14 shows an enlarged view of a part of FIG. As shown in FIGS. 13 and 14, the NPWG according to the present embodiment has a periodic structure in which the period is about 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.

Even if the waveguide structure of the same material is 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, the NPWG having a different core width can be used. The same characteristics can be realized. FIG. 15 shows the distribution in the core width direction when a higher reference refractive index n (0) than in the above example is used. The distribution of the equivalent refractive index of the NPWG at that time is as shown in FIG.

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.

<Example 2>
In the wavelength region [154.14 nm to 1558.17 nm], a dispersion compensation device that realizes chromatic dispersion compensation with a dispersion amount D = −1700 ps / nm and a dispersion slope ratio RDS = 0.0036 nm ⁻¹ was designed. . At this time, the NPWG was designed so that the wavelength region for dispersion compensation is divided into 20 channels satisfying the frequency f of 193.4 + 0.1 nTHz ≦ f ≦ 193.5 + 0.1 nTHz. Here, n represents an integer satisfying −10 ≦ n ≦ 9. In this dispersion compensation device, dispersion compensation is performed in each channel. Each of these channels fills the ITU grid interval. The dispersion compensation device of this embodiment can compensate for the residual dispersion of S-SMF having a length of 100 km.

FIG. 17 is a graph showing the potential distribution of the 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 distribution is used as described above, the group delay characteristic shown in FIG. 18 and the reflectance characteristic shown in FIG. 19 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

The NPWG of this example has a waveguide structure in which a core having a height h ₃ = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass. In this waveguide structure, the core width distribution of the NPWG realizing the characteristics shown in FIGS. 18 and 19 is as shown in FIG. The distribution of the equivalent refractive index of the NPWG at that time is as shown in FIG.

In this embodiment, the potential fluctuation is larger than that in the first embodiment because the compensation band (channel) is increased. Further, the amount of change in the core width of the NPWG for realizing this potential fluctuation has also increased. However, the length of the device is the same as in the first embodiment. That is, in this embodiment, dispersion compensation in a larger number of bands can be realized with the dispersion compensation device having the same length as that of the first embodiment.

<Example 3>
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 dispersion slope to dispersion ratio RDS = 0.0036 nm ⁻¹ was designed. . At this time, the NPWG was designed so that the wavelength region for dispersion compensation was divided into 50 channels with the frequency f satisfying 193.4 + 0.1 nTHz ≦ f ≦ 193.5 + 0.1 nTHz. Here, n represents an integer satisfying −25 ≦ n ≦ 24. In this dispersion compensation device, dispersion compensation is performed in each channel. Each of these channels fills the ITU grid interval. This is a dispersion compensation device that covers the entire C band. The dispersion compensation device of this embodiment can compensate for the residual dispersion of S-SMF having a length of 100 km.

FIG. 22 is a graph showing the potential distribution of the 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 distribution is used as described above, the group delay characteristic shown in FIG. 23 and the reflectance characteristic shown in FIG. 24 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

The NPWG of this example has a waveguide structure in which a core having a height h ₃ = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass. In this waveguide structure, the core width distribution of the NPWG realizing the characteristics shown in FIGS. 23 and 24 is as shown in FIG. The distribution of the equivalent refractive index of the NPWG at that time is as shown in FIG.

In this embodiment, the potential fluctuation is larger than that in the first embodiment because the compensation band (channel) is increased. In addition, the amount of change in the core width of the NPWG for realizing this potential fluctuation has also increased. However, the length of the device is the same as in the first embodiment. That is, in this embodiment, dispersion compensation in a larger number of bands can be realized with the dispersion compensation device having the same length as that of the first embodiment.

<Example 4>
In the wavelength region [1587.04 nm to 1595.49 nm], a dispersion compensation device was designed to realize chromatic dispersion compensation with a dispersion amount D = −1900 ps / nm and a dispersion slope ratio RDS = 0.003 nm ⁻¹ . . At this time, the NPWG was designed so that the wavelength region for dispersion compensation was divided into 10 channels satisfying the frequency f of 188.4 + 0.1 nTHz ≦ f ≦ 188.5 + 0.1 nTHz. Here, n represents an integer satisfying −5 ≦ n ≦ 4. In this dispersion compensation device, dispersion compensation is performed in each channel. Each of these channels fills the ITU grid interval. The dispersion compensation device of this embodiment can compensate for the residual dispersion of S-SMF having a length of 100 km.

FIG. 27 is a graph showing the potential distribution of the 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 1591.26 nm. When this potential distribution is used as described above, the group delay characteristic shown in FIG. 28 and the reflectance characteristic shown in FIG. 29 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

The NPWG of this example has a waveguide structure in which a core having a height h ₃ = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass. In this waveguide structure, the core width distribution of the NPWG realizing the characteristics shown in FIGS. 28 and 29 is as shown in FIG. The distribution of the equivalent refractive index of NPWG at that time is as shown in FIG.

<Example 5>
In the wavelength region [158.85 nm to 1599.75 nm], a dispersion compensation device that realizes chromatic dispersion compensation with a dispersion amount D = −1900 ps / nm and a dispersion slope ratio RDS = 0.003 nm ⁻¹ was designed. . At this time, the NPWG was designed so that the wavelength region for dispersion compensation was divided into 20 channels satisfying the frequency f of 188.4 + 0.1 nTHz ≦ f ≦ 188.5 + 0.1 nTHz. Here, n represents an integer satisfying −10 ≦ n ≦ 9. In this dispersion compensation device, dispersion compensation is performed in each channel. Each of these channels fills the ITU grid interval. The dispersion compensation device of this embodiment can compensate for the residual dispersion of S-SMF having a length of 100 km.

FIG. 32 is a graph showing the potential distribution of the 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 1591.26 nm. When this potential distribution is used as described above, the group delay characteristic shown in FIG. 33 and the reflectance characteristic shown in FIG. 32 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

The NPWG of this example has a waveguide structure in which a core having a height h ₃ = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass. In this waveguide structure, the core width distribution of the NPWG realizing the characteristics shown in FIGS. 33 and 34 is as shown in FIG. The distribution of the equivalent refractive index of the waveguide at that time is as shown in FIG.

In this example, the fluctuation in potential was larger than that in Example 4 because the compensation band (channel) was increased. Further, the amount of change in the core width of the NPWG for realizing this potential fluctuation has also increased. However, the length of the device is the same as in the fourth embodiment. That is, in this embodiment, dispersion compensation for a larger number of bands can be realized with a dispersion compensation device having the same length as that of the fourth embodiment.

<Example 6>
In the wavelength region [1574.54 nm to 1608.33 nm], a dispersion compensation device that realizes chromatic dispersion compensation with a dispersion amount D = −1900 ps / nm and a dispersion slope ratio RDS = 0.003 nm ⁻¹ was designed. . At this time, the NPWG was designed so that the wavelength region for dispersion compensation was divided into 40 channels satisfying the frequency f of 188.4 + 0.1 nTHz ≦ f ≦ 188.5 + 0.1 nTHz. Here, n represents an integer satisfying −20 ≦ n ≦ 19. In this dispersion compensation device, dispersion compensation is performed in each channel. Each of these channels fills the ITU grid interval. The dispersion compensation device of this embodiment can cover almost the entire L band. The dispersion compensation device of this embodiment can compensate for the residual dispersion of S-SMF having a length of 100 km.

FIG. 37 is a graph showing the potential distribution of the 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 1591.26 nm. When this potential distribution is used as described above, the group delay characteristic shown in FIG. 38 and the reflectance characteristic shown in FIG. 39 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

The NPWG of this example has a waveguide structure in which a core having a height h ₃ = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass. In this waveguide structure, the core width distribution of the NPWG realizing the characteristics shown in FIGS. 38 and 39 is as shown in FIG. The distribution of the equivalent refractive index of the NPWG at that time is as shown in FIG.

In this example, the fluctuation in potential was larger than that in Example 4 because the compensation band (channel) was increased. In addition, the amount of change in the core width of the NPWG for realizing this potential fluctuation has also increased. However, the length of the device is the same as in the fourth embodiment. That is, in this embodiment, dispersion compensation for a larger number of bands can be realized with a dispersion compensation device having the same length as that of the fourth embodiment.

<Example 7>
In the wavelength region [1507.25 nm to 1514.87 nm], a dispersion compensation device was designed that realizes chromatic dispersion compensation with a dispersion amount D = −1400 ps / nm and a dispersion slope ratio RDS = 0.005 nm ⁻¹ . . At this time, the NPWG was designed so that the wavelength region for dispersion compensation is divided into 10 channels satisfying the frequency f of 198.4 + 0.1 nTHz ≦ f ≦ 198.5 + 0.1 nTHz. Here, n represents an integer satisfying −5 ≦ n ≦ 4. In this dispersion compensation device, dispersion compensation is performed in each channel. Each of these channels fills the ITU grid interval. The dispersion compensation device of this embodiment can compensate for the residual dispersion of S-SMF having a length of 100 km.

FIG. 42 is a graph showing the potential distribution of the 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 151.05 nm. When this potential distribution is used as described above, the group delay characteristic shown in FIG. 43 and the reflectance characteristic shown in FIG. 44 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

The NPWG of this example has a waveguide structure in which a core having a height h ₃ = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass. In this waveguide structure, the core width distribution of the NPWG realizing the characteristics shown in FIGS. 43 and 44 is as shown in FIG. The distribution of the equivalent refractive index of the NPWG at that time is as shown in FIG.

<Example 8>
In the wavelength region [1503.47 nm to 1518.71 nm], a dispersion compensation device that realizes chromatic dispersion compensation in which the dispersion amount D = −1400 ps / nm and the dispersion slope to dispersion ratio RDS = 0.005 nm ⁻¹ was designed. . At this time, the NPWG was designed so that the wavelength region for dispersion compensation is divided into 20 channels satisfying the frequency f of 198.4 + 0.1 nTHz ≦ f ≦ 198.5 + 0.1 nTHz. Here, n represents an integer satisfying −10 ≦ n ≦ 9. In this dispersion compensation device, dispersion compensation is performed in each channel. Each of these channels fills the ITU grid interval. The dispersion compensation device of this embodiment can compensate for the residual dispersion of S-SMF having a length of 100 km.

FIG. 47 is a graph showing the potential distribution of the 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 151.05 nm. When this potential distribution is used as described above, the group delay characteristic shown in FIG. 48 and the reflectance characteristic shown in FIG. 49 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

The NPWG of this example has a waveguide structure in which a core having a height h ₃ = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass. In this waveguide structure, the core width distribution of the NPWG realizing the characteristics shown in FIGS. 48 and 49 is as shown in FIG. The distribution of the equivalent refractive index of the NPWG at that time is as shown in FIG.

In this example, the fluctuation in potential was larger than that in Example 7 because the compensation band (channel) was increased. Further, the amount of change in the core width of the NPWG for realizing this potential fluctuation has also increased. However, the length of the device is the same as in the seventh embodiment. That is, in this example, dispersion compensation for a larger number of bands could be realized with a dispersion compensation device having the same length as that of Example 7.

<Example 9>
In the wavelength region [149.25 nm to 1530.33 nm], a dispersion compensation device that realizes chromatic dispersion compensation with a dispersion amount D = −1400 ps / nm and a dispersion slope ratio RDS = 0.005 nm ⁻¹ was designed. . At this time, the NPWG was designed so that the wavelength region for dispersion compensation is divided into 50 channels in which the frequency f satisfies 198.4 + 0.1 nTHz ≦ f ≦ 198.5 + 0.1 nTHz. Here, n represents an integer satisfying −25 ≦ n ≦ 24. In this dispersion compensation device, dispersion compensation is performed in each channel. Each of these channels fills the ITU grid interval. The dispersion compensation device of this embodiment can compensate for the residual dispersion of S-SMF having a length of 100 km.

FIG. 52 is a graph showing the NPWG potential distribution of the dispersion compensation device fabricated in this example. The horizontal axis in the figure represents a location standardized at a center wavelength of 151.05 nm. When this potential distribution is used as described above, the group delay characteristic shown in FIG. 53 and the reflectance characteristic shown in FIG. 54 are obtained. In both figures, spectral data (designed) used for design and obtained spectral data (realized) are shown.

The NPWG of this example has a waveguide structure in which a core having a height h ₃ = 6 μm and a relative refractive index difference Δ = 0.6% is embedded in a clad made of quartz glass. In this waveguide structure, the core width distribution of the NPWG realizing the characteristics shown in FIGS. 53 and 54 is as shown in FIG. The distribution of the equivalent refractive index of the NPWG at that time is as shown in FIG.

In this example, the fluctuation in potential was larger than that in Example 7 because the compensation band (channel) was increased. In addition, the amount of change in the core width of the NPWG for realizing this potential fluctuation has also increased. However, the length of the device is the same as in the seventh embodiment. That is, in this example, dispersion compensation for a larger number of bands could be realized with a dispersion compensation device having the same length as that of Example 7.

The dispersion compensation device according to the present invention is a reflection-type chromatic dispersion compensation means that converts an optical waveguide whose equivalent refractive index of the core is nonuniformly changed in the light propagation direction by changing the physical dimension of the core embedded in the clad. The optical waveguide has a dispersion compensation characteristic in which a wavelength region for dispersion compensation is divided into a plurality of channels, and dispersion is compensated within the wavelength region of these channels.

Claims (14)

1. An optical waveguide in which the equivalent refractive index of the core is changed nonuniformly in the light propagation direction by changing the physical dimension of the core embedded in the clad as a reflection type chromatic dispersion compensation means;
   The optical waveguide has a dispersion compensation characteristic in which a wavelength region for dispersion compensation is divided into a plurality of channels, and dispersion is compensated in the wavelength region of these channels;
   An optical waveguide type chromatic dispersion compensation device.
2. 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.
3. 3. The optical waveguide according to claim 2, wherein the width of the core is unevenly distributed over the light propagation direction so that both sides of the core in the width direction are symmetrical from the center of the core. 4. Type chromatic dispersion compensation device.
4. 3. The optical waveguide according to claim 2, wherein the width of the core is unevenly distributed in the light propagation direction so that both sides of the core in the width direction are asymmetric from the center of the core. Type chromatic dispersion compensation device.
5. 3. The light guide according to claim 2, wherein the width of the core is unevenly distributed over the light propagation direction only on one side of both sides of the core in the width direction from the center of the core. Waveguide-type chromatic dispersion compensation device.
6. The optical waveguide type chromatic dispersion compensation device according to claim 1, wherein the core is linearly provided in the optical waveguide.
7. The optical waveguide type chromatic dispersion compensating device according to claim 1, wherein the core is provided in a meandering manner in the optical waveguide.
8. One end of the optical waveguide is a transmission end, and the other end of the optical waveguide is a reflection end;
   The transmissive end is terminated with a non-reflective termination;
   A light output is extracted at the reflection end via a circulator or a directional coupler;
   The optical waveguide type chromatic dispersion compensation device according to claim 1.
9. The optical waveguide type chromatic dispersion compensation device according to claim 1, 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.
10. The optical waveguide has a center wavelength λ _{c in} the range of 1490 nm ≦ λ _c ≦ 1613 nm and an operating band ΔBW in the range of 0.1 nm ≦ ΔBW ≦ 60 nm.
    The dispersion D 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. Item 4. An optical waveguide type chromatic dispersion compensation device according to Item 1.
11. The equivalent refractive index distribution of the core over the light propagation direction of the optical waveguide is
    Solve as an inverse scattering problem that numerically derives the potential function from the spectral data of the reflection coefficient, using the Zakharov-Shabat equation;
    Designed with a design method that estimates the potential to achieve the desired reflection spectrum from the values obtained from this inverse scattering problem;
    The optical waveguide type chromatic dispersion compensation device according to claim 1.
12. The equivalent refractive index distribution of the core over the light propagation direction of the optical waveguide is
    Using a wave equation that introduces a variable that is the amplitude of the power wave propagating forward and backward of the optical waveguide, it is reduced to the Zakharov-Shabat equation having a potential derived from the logarithmic derivative of the equivalent refractive index of the optical waveguide. Solve as an inverse scattering problem that numerically derives the potential function from the spectral data of the reflection coefficient;
    From the value obtained by this inverse scattering problem, the potential for realizing the desired reflection spectrum is inferred;
    Determine the equivalent refractive index based on this potential;
    Designed by calculating the width distribution of the core over the light propagation direction of the optical waveguide from the relationship between the predetermined thickness of the core, the equivalent refractive index, and the dimension of the core, which is obtained in advance;
    The optical waveguide type chromatic dispersion compensation device according to claim 11.
13. The equivalent refractive index distribution of the core over the light propagation direction of the optical waveguide is:
    It is almost a periodic structure at the center wavelength scale of the dispersion compensating band;
    On a scale larger than the center wavelength, it has a two-layer structure of an aperiodic structure determined by the inverse scattering problem;
    The optical waveguide type chromatic dispersion compensation device according to claim 11.
14. Providing 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, a predetermined core shape designed so that the equivalent refractive index of the core varies non-uniformly in the light propagation direction is left on the core layer, and a core is formed by removing the other portions;
    Then producing an optical waveguide by providing a cladding covering the core;
    A method for manufacturing an optical waveguide type chromatic dispersion compensation device according to claim 1, wherein the optical waveguide type chromatic dispersion compensation device is manufactured.

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