JP2002071945A - Element and method for compensating dispersion of light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problem in the conventional case that an element with satisfactory compensation characteristic has not been obtained inexpensively in spite of the proposal of various methods and elements for compensating dispersion for eliminating difficulty in communications resulting from the occurrence of wavelength dispersion in a signal transmitted through an optical fiber in optical communications in which a communication bit rate is >=10 Gbps, especially >=40 Gbps. SOLUTION: When producing elements capable of performing dispersion compensation through the use of group velocity delay time-wavelength characteristic and connecting a plurality of the elements in series, the element for performing dispersion compensation and a collimetor part are mounted on separate holding members and both of the holding members are mounted to a case attachably and detachably and opposedly to each other, thereby the optical dispersion compensation element which is large in band width and large in the extreme value of the group velocity delay time is prepared at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In the following description of the present invention, optical dispersion compensation is simply referred to as dispersion compensation, optical dispersion compensation element is also simply referred to as dispersion compensation element, and optical dispersion compensation method is simply referred to as dispersion compensation method. It is also called a compensation method.

[0002] The present invention relates to an element (hereinafter, simply referred to as "dispersion") capable of compensating for chromatic dispersion of second or higher order (described later) (hereinafter simply referred to as "dispersion") which occurs in optical communication using an optical fiber as a transmission path.
An element capable of compensating the next dispersion is also referred to as an element capable of changing the second dispersion or a second dispersion compensation element. Similarly, an element capable of compensating for a third-order dispersion, which will be described later, is also referred to as an element capable of changing the third-order dispersion or a third-order dispersion compensating element). About the method. More specifically, the present invention particularly relates to a dispersion compensating element capable of compensating for third-order or higher dispersion and a dispersion compensating method using the same,
Alternatively, the present invention relates to a dispersion compensating element capable of performing second-order, third-order or higher dispersion compensation, and a dispersion compensation method using the same. The dispersion compensating element of the present invention may be only the above-described third-order dispersion compensating element, or may include a unit for changing an incident position of incident light on an incident surface described later. In addition to the above-mentioned dispersion compensation, there are cases where it is configured to be able to perform second-order dispersion compensation, there are cases where it is mounted on a case, and in the case of a so-called chip or wafer that is not mounted on the case There is also. The dispersion compensating element of the present invention includes all of these forms, and can take various forms according to purposes such as use and sale.

In the present invention, the second-order dispersion compensation is described in FIG.
(A) to compensate for the slope of the dispersion of the wavelength-time characteristic curve described later ", and the third-order dispersion compensation means" compensation of the wavelength-time characteristic curve described later with reference to FIG. Compensating for bending ".

[0004]

2. Description of the Related Art In optical communication using an optical fiber for a communication transmission line, there is a demand for a longer distance of the communication transmission line and a higher communication bit rate with the progress of the utilization technology and the expansion of the use range. Under such an environment, dispersion generated when transmitting an optical fiber becomes a serious problem, and various attempts have been made to compensate for dispersion. At present, second-order dispersion is a major problem, and various compensations have been proposed, some of which have been effective.

However, as the demand for optical communication becomes higher, it is not enough to compensate only for secondary dispersion during transmission, and compensation for tertiary dispersion is becoming an issue.

A conventional second-order dispersion compensation method will be described below with reference to FIGS.

FIG. 9 is a diagram illustrating the dispersion-wavelength characteristics of a single mode optical fiber (hereinafter, also referred to as SMF), a dispersion compensating fiber, and a dispersion shift fiber (hereinafter, also referred to as DSF). 9, reference numeral 601 denotes a graph showing the dispersion-wavelength characteristic of the SMF, 602 denotes a graph showing the dispersion-wavelength characteristic of the dispersion compensating fiber, and 603 denotes D.
7 is a graph showing SF-dispersion-wavelength characteristics, in which the vertical axis represents dispersion and the horizontal axis represents wavelength.

As is apparent from FIG. 9, in the SMF, the dispersion increases as the wavelength of the light input to the fiber increases from 1.3 μm to 1.7 μm. Dispersion decreases as the length increases from 0.3 μm to 1.7 μm. In the DSF, the dispersion decreases as the wavelength of the input light increases from 1.2 μm to around 1.55 μm, and the wavelength of the input light becomes 1.55 μm.
The dispersion increases as the distance from the vicinity increases to 1.8 μm. In the DSF, in conventional optical communication at a communication bit rate of about 2.5 Gbps (2.5 gigabits per second), dispersion does not cause a problem in optical communication when the wavelength of input light is around 1.55 μm.

FIG. 8 is a diagram mainly explaining a method of compensating for the second-order dispersion. FIG.
(B) illustrates a transmission example in which second-order dispersion compensation is performed using a dispersion compensating fiber in a transmission line using SMF, and (C) illustrates a transmission example in a transmission line configured only with SMF. FIG.

In FIG. 8, reference numerals 501 and 511 are graphs showing characteristics of signal light before being input to the transmission line, reference numeral 530 is a transmission line constituted by SMF531, and reference numerals 502 and 512 are
The signal light having the characteristics shown in graphs 501 and 511
520 is a graph showing the characteristics of the signal light transmitted through the transmission line 30 and output from the transmission line 530; 520 is a transmission line composed of the dispersion compensating fiber 521 and the SMF 522;
Is a graph showing the characteristics of the signal light output from the transmission line 520 after the signal light having the characteristics shown in the graphs 501 and 511 is transmitted through the transmission line 520. Reference numerals 504 and 514
After the signal light having the characteristics shown in the graphs 501 and 511 is transmitted through the transmission path 520 and output from the transmission path 520,
FIG. 50 is a graph showing characteristics of signal light when desirable third-order dispersion compensation described below is performed by the present invention.
And 511. Graph 5
01, 502, 503, and 504 are wavelengths on the vertical axis, respectively.
The horizontal axis is a graph with time (or time), and the graphs 511, 512, 513, and 514 are light intensity on the vertical axis and time (or time) on the horizontal axis, respectively. Reference numerals 524 and 534 are transmitters and 525 and 53.
5 is a receiver.

As described above, in the conventional SMF, the dispersion increases as the wavelength of the signal light increases from 1.3 μm, so that a group velocity delay due to the dispersion occurs in high-speed communication or long-distance transmission. In the transmission path 530 constituted by the SMF, the signal light is greatly delayed on the long wavelength side as compared with the short wavelength side during transmission, as shown in graphs 502 and 512. For example, in high-speed communication and long-distance transmission, the changed signal light may not be able to be received as an accurate signal because it overlaps the preceding and following signal lights.

In order to solve such a problem, conventionally,
For example, as shown in FIG. 8B, dispersion is compensated (or also referred to as correction) using a dispersion compensating fiber. The conventional dispersion compensating fiber solves the problem of SMF in which the dispersion increases as the wavelength increases from 1.3 μm to 1.7 μm. Therefore, as described above, the wavelength increases from 1.3 μm to 1.7 μm. And the variance decreases as the length increases. The dispersion compensating fiber is, for example, as shown by a transmission line 520 in FIG.
A dispersion compensating fiber 521 can be connected to F522 and used. In the transmission line 520, the signal light
In 522, the long wavelength side is greatly delayed compared to the short wavelength side,
In the dispersion compensating fiber 521, the shorter wavelength side is delayed more than the longer wavelength side, so that the amount of change can be suppressed smaller than the changes shown in the graphs 502 and 512 as shown in the graphs 503 and 513.

However, in the above-mentioned conventional method of compensating for the second-order chromatic dispersion using the dispersion compensating fiber, the chromatic dispersion of the signal light transmitted through the transmission line is determined by the state of the signal light before input to the transmission line, that is, Dispersion compensation cannot be performed up to the shape of the graph 501, and the compensation is limited to the shape of the graph 503. As shown in the graph 503, in the conventional secondary chromatic dispersion compensation method using the dispersion compensation fiber, the light of the central wavelength of the signal light is not delayed as compared with the light of the short wavelength side and the light of the long wavelength side. Only the light of the components on the shorter wavelength side and the longer wavelength side than the light of the central wavelength component of the signal light is delayed. Then, as shown in a graph 513, a ripple may be generated in a part of the graph.

[0014] These phenomena are becoming a serious problem, such as the inability to accurately receive signals as needs for longer transmission distances and higher communication speeds in optical communication increase. For example, these phenomena are of considerable concern in high-speed communication at a communication bit rate of 10 Gbps (10 gigabits per second) or more, and in particular, at a communication bit rate of 40 Gbps or more as a very serious problem. . In such high-speed communication, it is considered difficult to use a conventional optical fiber communication system. For example, it is necessary to change the material of the optical fiber itself. Has become a serious problem.

[0015]

It is difficult to perform such dispersion compensation only by second-order dispersion compensation, and third-order or higher dispersion compensation is required.

Conventionally, an optical fiber (hereinafter, an optical fiber is also simply referred to as a fiber) whose second-order dispersion is reduced with respect to light having a wavelength of about 1.55 μm is referred to as D.
Although there is SF, this fiber cannot perform third-order dispersion compensation, which is the subject of the present invention, as is clear from the characteristics shown in FIGS.

In realizing high-speed communication and long-distance communication of optical communication, third-order dispersion is gradually recognized as a major problem, and its compensation is becoming an important issue. Many attempts have been made to solve the third-order dispersion compensation problem, but a third-order dispersion compensating element and a compensation method that can sufficiently solve the conventional problems are still in practical use. Not.

As an example of the optical dispersion compensating element used for the third-order dispersion compensation, the present inventors succeeded in the third-order dispersion compensation by using an optical dispersion compensating element using a multilayer film such as a dielectric. The conventional optical communication technology has been greatly advanced. However, for example, if the communication bit rate is 40 Gbp
In order to ideally perform third-order dispersion compensation at high speeds such as s and 80 Gbps, or to sufficiently perform third-order dispersion compensation in optical communication of a plurality of channels, for example, in a wider wavelength range, There is a strong demand for practical use of a dispersion compensating element and a dispersion compensating method capable of sufficiently compensating the second and third-order or higher dispersion, and corresponding to various situations of a communication system. One proposal is to adjust the wavelength band of group velocity delay and the delay time of group velocity delay.
A second-order dispersion compensating element has been proposed. In particular, as one method of inexpensively putting a third-order or higher dispersion compensation element suitable for the wavelength of each channel into practical use, a wavelength tunable (ie,
A dispersion compensating element which can select a wavelength to be compensated for dispersion) has been proposed. However, it is difficult to obtain a dispersion compensating element having a group velocity delay time-wavelength characteristic such that sufficient dispersion compensation can be performed in a wide wavelength range using these dispersion compensating elements alone.

As a method of obtaining a dispersion compensating element having a group velocity delay time-wavelength characteristic capable of performing good dispersion compensation in a wide wavelength range, an element capable of performing dispersion compensation proposed by the present inventors is called a signal. There is a method of serially connecting a plurality of light beams in the optical path. In this case, in order to satisfy the specification required for the dispersion compensating element, considering the variation of the element capable of performing the dispersion compensation, the selection of the element capable of performing the dispersion compensation and the connection thereof are complicated. It is necessary, and improvement is required in terms of complexity and cost. This combination of elements capable of performing dispersion compensation and their connection also pose a problem in maintenance. In the conventional method of sequentially connecting elements capable of performing dispersion compensation using an optical fiber collimator, the apparatus becomes complicated,
Not only is the cost of maintenance high, but the quality of the maintenance tends to be low.

The present invention has been made in view of the above points, and an object of the present invention is to facilitate assembly work, increase the production yield, and flexibly cope with a change in specifications.
An object of the present invention is to provide a wide-band optical dispersion compensating element which is easy to maintain and an optical dispersion compensating method using the same.

[0021]

In order to achieve the object of the present invention, an optical dispersion compensating element according to the present invention uses chromatic dispersion (hereinafter simply referred to as chromatic dispersion) by using an optical fiber for communication using a communication transmission line.
(Also referred to as dispersion), and the dispersion compensating element includes at least two elements capable of performing dispersion compensation in a signal light communication path.
Or an element capable of performing dispersion compensation (hereinafter, an element capable of performing dispersion compensation and an element capable of performing dispersion compensation are collectively referred to as an element capable of performing dispersion compensation) At least two places)
It is configured to be connected in series via at least a pair of holding members, and one of the pair of holding members (hereinafter, also referred to as holding member A) may perform the dispersion compensation. At least one element that can be mounted is mounted, and the other holding member (hereinafter, also referred to as holding member B) of the pair of holding members has an optical fiber including at least two optical fibers and a lens. A collimator is mounted, and the holding member A and the holding member B
And a plurality of pairs of the holding member A and the holding member B are attached to one case so as to face each other.

This makes it easy to assemble the optical dispersion compensating element according to the specifications, increases the degree of freedom in combining elements capable of performing dispersion compensation, increases the manufacturing yield, and increases the manufacturing cost. Goes down. An element capable of performing dispersion compensation and an optical fiber collimator for connection thereof can be easily attached and detached. It is easy to modify the dispersion compensation characteristics, including the case of maintenance, the structure is simplified, and the quality of maintenance is greatly improved.

In a preferred embodiment of the light dispersion compensating element of the present invention, the pair of holding members A and B are provided with positioning means for positioning when the holding members A and B are assembled in the case. The above effect is further ensured.

In a preferred embodiment of the optical dispersion compensating element according to the present invention, the focal point of the optical fiber collimator of the holding member B is adjusted such that the focal point of the optical dispersion collimator mounted on the holding member A is capable of performing the optical dispersion compensation. As described above, the holding member A and the holding member B are positioned when assembled in the case.

In a preferred embodiment of the light dispersion compensating element of the present invention, the positioning means provided on the pair of holding members A and B is means for positioning by engaging with the case. It is characterized by.

In a preferred embodiment of the light dispersion compensating element according to the present invention, the positioning means is a reference surface provided on the case and at least one of the holding members A and B. In a preferred example of the optical dispersion compensating element of the present invention, the reference plane can be three planes orthogonal to each other. In a preferred example of the light dispersion compensation element of the present invention, a spring acting to press the holding member A and the holding member B in the direction of the reference plane includes at least one of the holding member A and the case. An optical dispersion compensating element provided at one location and at least one location of at least one of the holding member B and the case.

By doing so, it is possible to further facilitate attachment and detachment of the element capable of performing dispersion compensation and the optical fiber collimator for connecting the element.

In a preferred embodiment of the optical dispersion compensating element of the present invention, a structure is provided in which at least one of the case and the holding member A and at least one of the case and the holding member B can be screwed. It is characterized in that the holding member A and the holding member B can be fixed to the case by screwing.

Further, a preferred example of the optical dispersion compensating element of the present invention is characterized in that the element capable of performing the dispersion compensation is an element having a multilayer film. In this manner, as will be described in detail later with reference to the drawings in the present invention, it is possible to provide an optical dispersion compensator having excellent dispersion compensation characteristics over a wide band with high reliability and at low cost.

In a preferred example of the optical dispersion compensating element of the present invention, the multilayer film of the element capable of performing the dispersion compensation has a curve having at least one extreme value in a wavelength range of 1460 to 1640 nm of incident light. It is characterized by having a group velocity delay time-wavelength characteristic as follows.

In a preferred embodiment of the light dispersion compensating element of the present invention, the multilayer film has at least two reflective layers having different light reflectances and at least one light transmitting layer formed between the reflective layers. It is characterized by having.

In a preferred example of the optical dispersion compensating element of the present invention, the element capable of performing the dispersion compensation includes at least five types of laminated films having different optical properties (that is, such as light reflectance and film thickness). And at least three types of reflective layers including at least two types of reflective layers having different light reflectivities from each other. ,
It has at least two light transmission layers in addition to the three types of reflection layers, and each one of the three types of reflection layers and each one of the two light transmission layers are alternately arranged, The multilayer film
In order from one side in the thickness direction of the film, a first layer as a first reflection layer, a second layer as a first light transmission layer, a third layer as a second reflection layer, and a second light transmission The first to fifth layers are composed of a fourth layer that is a layer and a fifth layer that is a third reflective layer, where λ is the center wavelength of the incident light. The film thickness of each layer of the multilayer film (hereinafter, simply referred to as an optical path length).
A film having a value within a range of an integral multiple of λ / 4 ± 1% (hereinafter, also simply referred to as an integral multiple of λ / 4 or an integral multiple of λ / 4). And the thickness of the multilayer film is 1/4 times λ (hereinafter, 1 // of λ).
(In the meaning of 4 times ± 1% of film thickness, it is called 1/4 times of λ)
And a layer having a higher refractive index (hereinafter, also referred to as a layer H) and a layer having a film thickness of 1/4 times λ and a lower refractive index (hereinafter, also referred to as a layer L). The multilayer film A is formed by stacking the five layers, that is, the first to fifth layers, in the order from one side in the thickness direction of the multilayer film, to a layer H,
Three sets of layers (hereinafter, also referred to as HL layers) combined one by one in the order of the layer L (a layer obtained by combining the layer H1 layer and the layer L1 layer is referred to as one set of HL layers, the same applies hereinafter) are laminated. A first layer, a layer formed by combining layers H and H (that is, a layer formed by stacking two layers of H. Hereinafter, HH
Layer), which is formed by laminating 10 sets of
The third layer is formed by laminating one set of layers L and 7 sets of HL layers, the fourth layer is formed by stacking 38 sets of HH layers, and the third set of layers L is formed of one layer and HL. The multilayer film B is formed by laminating 10 sets of the HH layers of the multilayer film A. Instead of two layers, the second layer is a layer obtained by combining three sets of HH layers and a layer L and a layer L in order from one side in the thickness direction of the film in the same direction as that of the multilayer film A (that is, a layer combining the layers L and L). , A layer formed by laminating two layers L (hereinafter, also referred to as LL layer), three sets of HH layers, three sets of LL layers, two sets of LL layers, and one set of HH layers. The multi-layered film is constituted by a multi-layered film, and the multi-layered film C is formed by stacking 38 sets of the HH layers of the multi-layered film A or B. And instead of the fourth layer is formed, the fourth layer, in order from one side in the thickness direction of the same direction of the film in the case of the multilayer film A, 3 sets a layer of HH,
3 sets of LL layers, 3 sets of HH layers, 3 sets of LL layers, 3 sets of HH layers, 3 sets of LL layers,
3 sets of HH layers, 3 sets of LL layers, 3 sets of HH layers, 3 sets of LL layers, 3 sets of HH layers,
The multilayer film D is a multilayer film formed by stacking three sets of LL layers, three sets of HH layers, three sets of LL layers, and two sets of HH layers in this order.
A layer (hereinafter referred to as LH) in which the five-layered film, that is, the first to fifth layers are combined one by one in the order of layer L and layer H in order from one side in the thickness direction of the multilayer film. The first layer is formed by laminating five sets of LH, the second layer is formed by laminating seven sets of LL layers, and one layer H is defined as LH.
A third layer formed by stacking seven sets of LH layers, a fourth layer formed by stacking 57 sets of LL layers, one layer H, and thirteen sets of LH layers. The multi-layered film is formed by a fifth layer that is configured, and the multi-layered film E is a laminated film of the five layers, that is, the first to fifth layers are sequentially arranged from one side in the thickness direction of the multi-layered film. A first layer formed by stacking two sets of HL layers, a second layer formed by stacking 14 sets of HH layers, a stack formed by stacking one layer L and six sets of HL layers. A third layer, a fourth layer formed by stacking 24 sets of HH layers, and a fifth layer formed by stacking one layer L and 13 sets of HL layers. And a multilayer film F formed by laminating 14 sets of the HH layers of the multilayer film E.
Instead of the layers, the second layer is composed of three sets of HH layers, three sets of LL layers, and three sets of HH layers in order from one side in the thickness direction of the film in the same direction as the multilayer film E. Set, LL
Layer, three sets of HH layers, two sets of LL layers, one set of LL layers, and one set of HH layers in this order to form a multilayer film composed of a laminated film. Instead of the fourth layer formed by laminating 24 sets of the HH layers of the multilayer film E or F, the fourth layer is one of the thickness directions of the film in the same direction as the multilayer film E. , Three sets of HH layers, three sets of LL layers, HH
3 layers, 3 sets of LL layers, 3 sets of HH layers, 3 sets of LL layers, 3 sets of HH layers, LL
Layer, three sets of HH layers, two sets of LL layers, one set of LL layers, and one set of HH layers in this order. , The five-layered film, that is, the first to fifth layers are formed by sequentially forming four layers L and LH from one side in the thickness direction of the multilayer film.
A first layer composed of set laminations, a second layer composed of nine sets of LL layers, one layer H and six layers LH
The third layer constituted by laminating the set and the LL layer is 35
When a multi-layered film is formed of a fourth layer formed by stacking a set, a single layer H, and a fifth layer formed by stacking 13 sets of LH layers, the dispersion compensation is performed. An element that can be performed includes at least one of the multilayer films A to H.

By using the various multilayer films as described above, it is possible to realize excellent group velocity delay time-wavelength characteristics as described in detail below as a detailed description of the present invention.

In a preferred example of the optical dispersion compensating element of the present invention, the thickness of at least one of the laminated films constituting the multilayer film is set in an in-plane direction in a cross section parallel to a light incident surface of the multilayer film. (Hereinafter, also referred to as an in-plane direction). And adjusting means for adjusting the film thickness of at least one laminated film of the multilayer film by engaging with the element capable of performing the dispersion compensation, or changing a light incident position on an incident surface of the multilayer film. Means can be provided.

In a preferred embodiment of the optical dispersion compensating element according to the present invention, the optical dispersion compensating element is capable of compensating mainly for third-order dispersion. Further, the optical dispersion compensating element may be capable of compensating for second-order dispersion, or second- and third-order dispersion.

In a preferred example of the optical dispersion compensating element of the present invention, the layer H is formed of Si, Ge, TiO ₂ , Ta
It is characterized by being formed of a layer containing at least one of ₂ O ₅ and Nb ₂ O ₅ as one of the main components. The layer L is formed using a material having a lower refractive index than the material used for the layer H. For example, the layer L is formed of a layer containing SiO ₂ as one of the main components.

In order to achieve the object of the present invention, an optical dispersion compensating method according to the present invention is a method for compensating dispersion using an optical dispersion compensating element, wherein the optical dispersion compensating element comprises: At least two elements can be compensated.
In the signal light communication path, the holding member A is configured to be connected in series via at least a pair of holding members, and is a holding member A that is one of the pair of holding members.
Is provided with at least one element capable of performing the dispersion compensation, an optical fiber collimator is provided on a holding member B which is the other holding member of the pair of holding members, and the holding member A and a holding member B are paired, and a plurality of pairs of holding members A and B are arranged so as to face each other to perform dispersion compensation.

In a preferred embodiment of the optical dispersion compensation method of the present invention, an element having a multilayer film is used as an element capable of performing the dispersion compensation.

In a preferred embodiment of the optical dispersion compensating method of the present invention, the group velocity of the multilayer film of the optical dispersion compensating element has a curve having at least one extreme value in a wavelength range of 1460 to 1640 nm of incident light. Delay time-
It is characterized in that a multilayer film having wavelength characteristics is used.

In a preferred example of the optical dispersion compensation method according to the present invention, as the multilayer film, the thickness of at least one laminated film constituting the multilayer film changes in a direction in the incident plane of the multilayer film. It is characterized by using a multi-layer film.

In a preferred embodiment of the optical dispersion compensating method of the present invention, the system for compensating for the dispersion is engaged with an element capable of performing the dispersion compensation to form at least one laminated film of the multilayer film. Adjusting means for adjusting the film thickness, or
It is characterized in that a means for changing the incident position of light on the incident surface of the multilayer film is provided.

In a preferred embodiment of the optical dispersion compensating method according to the present invention, the optical dispersion compensating element is capable of mainly compensating for third-order dispersion.

In a preferred embodiment of the optical dispersion compensating method according to the present invention, the optical dispersion compensating element is capable of compensating for secondary dispersion.

[0044]

Embodiments of the present invention will be described below with reference to the drawings. Each drawing used in the description schematically shows dimensions, shapes, arrangement relations, and the like of each component so that the present invention can be understood. For convenience of description of the present invention, the magnification may be partially changed in the drawings, and the drawings used in the description of the present invention may not necessarily be similar to the actual product or description of the embodiment. Also, in each of the drawings, the same components are denoted by the same reference numerals, and overlapping description may be omitted.

FIG. 1 is a diagram for explaining a method for compensating dispersion caused by communication using an optical fiber as a transmission line by an optical dispersion compensating element. Reference numeral 1101 denotes a second-order dispersion of signal light transmitted through the transmission line. Is the group velocity delay time-wavelength characteristic curve showing the third order dispersion of the signal light remaining after the compensation, 1102 is the group velocity delay time-wavelength characteristic curve of the dispersion compensating element, and 1103 is
The group velocity delay time between the compensation target wavelength bands λ _{1 and} λ ₂ after the dispersion of the signal light having the dispersion characteristic of the curve 1101 is compensated by the dispersion compensating element having the dispersion characteristic of the curve 1102 −
In the wavelength characteristic curve, the vertical axis represents the group velocity delay time, and the horizontal axis represents the wavelength.

FIGS. 2 to 4 are views for explaining a light dispersion compensating element according to the present invention. FIG. 2 is a sectional view of a multilayer film described later.
FIG. 4 is a perspective view of a multilayer film having a changed film thickness, and FIG. 4 is a diagram illustrating a group velocity delay time-wavelength characteristic curve of the multilayer film.

FIG. 2 is a diagram schematically illustrating a cross section of a multilayer film used as an example of the third-order dispersion compensating element of the present invention.
In FIG. 2, reference numeral 100 denotes a multilayer film as an example of the optical dispersion compensating element of the present invention, 101 denotes an arrow indicating the direction of incident light,
102 is an arrow indicating the direction of the emitted light, 103 and 104 are reflection layers having a reflectance of less than 100% (hereinafter also referred to as reflection films), 105 is a reflection layer having a reflectance of 98 to 100%, and 10 is a reflection layer.
8, 109 are light transmitting layers, and 111, 112 are cavities. Reference numeral 107 denotes a board, for example, BK-7
Using glass.

The reflectances R (103), R (104), and R (105) of each of the reflection layers 103, 104, and 105 in FIG.
R (103) ≦ R (104) ≦ R (105). It is preferable in terms of mass production that the reflectance of each reflective layer is set to be different from each other at least between adjacent reflective layers with the light transmitting layer interposed therebetween. That is, the reflective layers are formed such that the reflectance of each reflective layer with respect to the center wavelength λ of the incident light gradually increases from the side where the incident light is incident toward the thickness direction of the multilayer film. Then, the reflectance of each reflection layer with respect to the light having the wavelength λ is set to 60% ≦ R (103) ≦ 77%, 96
% ≦ R (104) ≦ 99.8%, 98% ≦ R (105)
R (103), R (104), R
By configuring so as to satisfy the relationship of (105),
A group velocity delay time-wavelength characteristic curve as described below can be obtained. Then, R (103) <R (104) <R
(105) is more preferable, and R (105) is closer to or more preferably 100%, and the performance of the optical dispersion compensating element of the present invention can be further enhanced.

Although not limited to this, in order to make it easier to manufacture the optical dispersion compensating element of the present invention, each reflection layer is formed so that the interval when considered as the optical path length between adjacent reflection layers is different. It is preferable to select the conditions for forming
The design accuracy of the reflectance of each reflective layer can be reduced, and the tertiary dispersion of the present invention can be achieved by a combination of unit films having a film thickness of ４ of the wavelength λ (film having an integral multiple of λ / 4). A multilayer film used for a compensating element can be formed, and a tertiary dispersion compensating element having high reliability and excellent mass productivity can be provided at low cost.

The unit film of the multilayer film has a wavelength λ.
Which is described as one quarter of
It means λ / 4 within the range of error allowed in the formation of a film in mass production, specifically, λ / 4 ± 1% means the film thickness of λ / 4 in the present invention, Even in this range, the present invention exhibits a particularly great effect. Therefore, in the present invention, the thickness in this range is defined as a thickness of λ / 4. In particular, the thickness of the unit film is λ / 4 ± 0.5%
(In this case, λ / 4 means λ / 4 without error), there is little variation without impairing mass productivity.
A highly reliable multilayer film can be formed, and an optical dispersion compensating element as described below can be provided at low cost.

The multilayer film of the present invention has a thickness of λ /
Although it is described that the unit film of No. 4 is formed by lamination, it is possible to form a multilayer film by repeating a method of forming one unit film and then forming the next unit film. Not limited to this, generally, a film having a thickness of an integral multiple of λ / 4 is generally formed continuously, and such a multilayer film is naturally included in the multilayer film of the present invention. It is. Then, some examples of the multilayer film of the present invention could be formed by using a film forming step of continuously forming the reflection layer and the transmission layer.

FIG. 3 is a view for explaining an example in which the thickness of the multilayer film 100 is changed in an in-plane direction of a light incident surface 220 of the multilayer film 100 shown in FIG.

In FIG. 3, reference numeral 200 denotes a multilayer film as an example of the optical dispersion compensating element of the present invention, 201 denotes a first reflecting layer, 202 denotes a second reflecting layer, 203 denotes a third reflecting layer,
05 is a substrate, 206 is a first light transmitting layer, 207 is a second light transmitting layer, 211 is a first cavity, 212 is a second cavity, 220 is a light incident surface, and 230 indicates the direction of incident light. Arrow, 240, arrow indicating the direction of the emitted light, 250
Is an arrow indicating a first film thickness change direction, 260 is an arrow indicating a second film thickness change direction, and 270 and 271 are arrows indicating a direction in which an incident position of incident light is moved.

In FIG. 3, for example, a third reflective layer 203 and a third reflective layer 203 are formed on a substrate 205 made of BK-7 glass or the like.
A second light transmission layer 207, a second reflection layer 202, a first light transmission layer 206, and a first reflection layer 201 are sequentially formed.

The thickness of the first light transmitting layer 206 changes in the direction indicated by the arrow 250 in FIG. 3 and the thickness of the second light transmitting layer 207 changes in the direction indicated by the arrow 260 in FIG. The multilayer film is formed. The thicknesses and configurations of the first to third reflection layers are defined as follows: when the wavelength when the resonance wavelength of the first and second cavities coincides with the center wavelength λ of the incident light, The reflective layer 3 is formed so that the reflectance of each reflective layer has a film thickness that satisfies the conditions of R (103), R (104), and R (105).

FIG. 4 shows incident light from a direction of an arrow 230 in FIG. , The outgoing light is obtained in the direction of arrow 240, and the incident position of the incoming light is set to the position indicated by arrow 270 in FIG.
Alternatively, it illustrates the manner in which the group velocity delay time-wavelength characteristic curve changes when moving in the direction of 271.

FIG. 4 shows a group velocity delay time-wavelength characteristic curve when incident light having a center wavelength λ is incident on the incident positions 280 to 282, wherein the vertical axis represents the group velocity delay time and the horizontal axis represents the wavelength. .

The reflection layers 201 to 203 and the light transmission layer 20
When the incident position of the incident light on the incident surface 220 is moved in the direction indicated by the arrow 270 by appropriately selecting the conditions for changing the film thickness in the directions indicated by the arrows 250 and 260 of FIGS. While maintaining the shape of the delay time-wavelength characteristic curve in substantially the same shape, the band center wavelength λ _{0 of} the group velocity delay time-wavelength characteristic curve (for example, the group velocity delay time-wavelength having a substantially symmetrical shape in FIG. 4) Characteristic curve 280
1), and when the incident position is moved from the position in the direction indicated by the arrow 271, the wavelength λ ₀ is substantially the same range, and the group velocity delay time−the wavelength The shape of the characteristic curve is represented by a curve 281 in FIG.
1, 2812. Each curve in FIG. 4 is obtained when the thickness of each film is monotonically increased in the directions of arrows 250 and 260 in FIG.

The band center wavelength λ ₀ in the curves 2801 to 2812 is set, for example, at an appropriate wavelength in the graph of FIG. 4 depending on the purpose of dispersion compensation.
It may be set to approximately the center value of the wavelength range of the curve shown in FIG. 4, or may be appropriately determined according to the purpose of dispersion compensation. In addition, it is natural that the correspondence between the wavelengths of the characteristic points of the curves such as the respective extreme wavelengths between the curves 2801 to 2812 should be checked in advance, etc., without being described here.

As described above, for example, first, the band center wavelength λ corresponding to the center wavelength λ of the incident light to be dispersion-compensated.
_In order to make ₀ coincide, the incident position of the incident light is indicated by an arrow 270.
And the shape of the group velocity delay time-wavelength characteristic curve used for dispersion compensation in accordance with the content of the compensation to be dispersion-compensated, that is, in accordance with the dispersion state of the incident light. The incident position is set to, for example, 280 in the direction indicated by the arrow 271 in FIG.
By selecting each point as shown by ~ 282,
The dispersion compensation required for the signal light can be effectively performed.

As is apparent from the shape of the group velocity delay time-wavelength characteristic curve in FIG. 4, tertiary dispersion compensation can be performed using the optical dispersion compensating element of the present invention, for example, using the curve 2801. , And a relatively close linear component of the curve 2811 or 2812 can be used to perform second-order fine dispersion compensation.

Although the “element capable of performing dispersion compensation” used in the present invention has been described with reference to FIGS. 2 to 4, if the “element capable of performing dispersion compensation” is used, It is clear from the description of each curve in FIG. 4 that the third-order dispersion can be compensated to some extent.

However, the wavelength band of the dispersion compensation that can be compensated by the “element capable of performing the dispersion compensation” alone is, for example, 1.5 n for the signal light whose wavelength is around 1.55 μm.
m, the magnitude of the group velocity delay time extreme is 3-6 ps
(Picoseconds) in many cases, and the bandwidth of 3 nm and the peak value of the group velocity delay time are 2 to 1 by changing the configuration conditions of the multilayer film.
A group velocity delay time-wavelength characteristic curve of about 0 ps can be realized. However, if the wavelength band of the dispersion compensation is widened to cope with the optical communication of a large number of channels, it is difficult to obtain a group velocity delay time that can sufficiently perform the dispersion compensation, and it is widely used for actual communication. Further improvement is desirable for use. Therefore, the present invention will be described in more detail with reference to FIGS.

FIG. 5 shows a group velocity delay time using a plurality of elements capable of performing dispersion compensation as described above.
FIG. 5 is a diagram for explaining a method for improving wavelength characteristics, and FIG.
5A shows a group velocity delay time-wavelength characteristic of one element capable of performing dispersion compensation used in the present invention, and FIG. 5B shows a group velocity delay time-wavelength characteristic curve having almost the same shape. According to the present invention, two devices capable of performing dispersion compensation having different wavelengths (hereinafter, also referred to as extreme values) giving a peak value (hereinafter, also referred to as extreme values) of a speed delay time-wavelength characteristic curve are connected in series. FIG. 5C shows a group velocity delay time-wavelength characteristic curve of the optical dispersion compensating element, and three elements capable of performing dispersion compensation having substantially the same group velocity delay time-wavelength characteristic curve but different extremal wavelengths in series. FIG. 5D shows a group velocity delay time-wavelength characteristic curve of the connected optical dispersion compensating element of the present invention, and FIG. Group velocity delay of three optical dispersion compensating elements of the present invention connected in series Time - is a graph representing the wavelength characteristics, both the group velocity delay time is the vertical axis and the horizontal axis represents the wavelength. The optical dispersion compensating method of the present invention uses the optical dispersion compensating elements shown in FIGS. 5A to 5D in an appropriate place in an optical transmission line, for example, an amplifier, a receiver, a wavelength This is a dispersion compensation method in which signal light is incident on the optical dispersion compensating element and is disposed in a path of signal light such as a branching filter or various devices of a relay station to compensate for dispersion of the signal light.

In FIG. 5, reference numerals 301 to 309 denote elements 1 capable of performing dispersion compensation used in the present invention.
Each group velocity delay time-wavelength characteristic curve 310 is a series of two elements capable of performing dispersion compensation having substantially the same shape of the group velocity delay time-wavelength characteristic curve used in the present invention and having different extreme wavelengths. Group delay time-wavelength characteristic curve 311 when connected to the group velocity delay time used in the present invention.
Group velocity delay time-wavelength characteristic curve when three elements capable of performing dispersion compensation with substantially the same wavelength characteristic curve and different extreme wavelengths are connected in series, and 312 is a group velocity delay time-wavelength characteristic curve. Is a group velocity delay time-wavelength characteristic curve when three elements capable of performing dispersion compensation having different shapes and extreme wavelengths are connected in series. In FIG. 5A, reference symbol a denotes the wavelength width of the wavelength band for dispersion compensation, and b denotes the extreme value of the group velocity delay time. The curves 302 to 307 and 309 have substantially the same bandwidth of the dispersion compensation target wavelength band and the extreme value of the group velocity delay time, and the curve 308 has a narrower bandwidth of the dispersion compensation target wavelength band than the curves 307 and 309 and has a group velocity delay. It is a group velocity delay time-wavelength characteristic curve with a large extremum of time.

5B and 5C, the extreme value of the group velocity delay time of the group velocity delay time-wavelength characteristic curve 310 is as follows.
1.6 in the case of one element capable of performing dispersion compensation
And the wavelength band for dispersion compensation is about 1.8 times,
The extreme value of the group velocity delay time of the group velocity delay time-wavelength characteristic curve 311 is about 2.3 times that of a single element capable of performing dispersion compensation, and the dispersion compensation target wavelength band can perform dispersion compensation. This is about 2.5 times that of one element.
In FIG. 5D, the extreme value of the group velocity delay time of the group velocity delay time-wavelength characteristic curve 312 is about three times as large as that of each of the elements 307 and 309 capable of performing dispersion compensation. The target wavelength band is about 2.3 times that of the case of each one of the elements 307 and 309 capable of performing dispersion compensation.

The extreme value of the group velocity delay time of the group velocity delay time-wavelength characteristic curve of the element capable of performing dispersion compensation using the multilayer film described with reference to FIGS. The wavelength width changes depending on the configuration conditions of each reflection layer and each light transmission layer of the multilayer film.
The bandwidth of the dispersion compensation target wavelength band as indicated by the curve 307 in (D) is relatively wide but the extreme value of the group velocity delay time is not so large. The target wavelength band is narrow, but the extreme value of the group velocity delay time is large, as in the group velocity delay time-wavelength characteristic curve,
An element having various characteristics and capable of performing dispersion compensation can be realized.

Examples of the multilayer film used for the element capable of performing such dispersion compensation include, for example, the multilayer films A to H described in the section “Means for Solving the Problems”.
Is raised. When an element capable of performing dispersion compensation was prepared using the multilayer films A to H, the wavelength was about 1.
For a signal light of 55 μm, the extreme value of the group velocity delay time is 3
The wavelength band targeted for dispersion compensation in 1.3 ps (picoseconds) is 1.3-2.
A group velocity delay time-wavelength characteristic curve of 0 nm was realized.

Then, a plurality of elements capable of performing the dispersion compensation are connected in series, and the dispersion compensation target wavelength band having a group velocity delay time-wavelength characteristic capable of compensating the dispersion due to the optical fiber transmission is 15 nm. Can be realized. This optical dispersion compensating element has a wavelength of about 1.55 μm and a bandwidth of 0.1 mm for each channel.
When used as an element for performing third-order dispersion compensation in a communication system of 5 nm and 30 channels and performing optical communication of 40 Gbps and 60 km, communication could be performed without harmful third-order dispersion.

A group of elements that can be used in series and can perform dispersion compensation, such as a group velocity delay time-wavelength characteristic curve in FIG. 4 and a group velocity delay time-wavelength characteristic curve in FIG. 5D. By appropriately selecting the speed delay time-wavelength characteristic, not only the third-order dispersion but also the second-order fine dispersion remaining after being compensated by the dispersion compensating fiber could be compensated.

In the example of the optical dispersion compensating element in which at least two elements capable of performing dispersion compensation according to the present invention are connected in series, the group velocity delay time-wavelength characteristic required for compensating the third or higher order dispersion is provided. It is necessary to use at least one element capable of performing dispersion compensation of the group velocity delay time-wavelength characteristic having an extreme value in the wavelength region to be compensated for dispersion in order to realize an optical dispersion compensation element having the following.

Further, in order to more effectively perform dispersion compensation of a communication transmission line, the group velocity delay time as an optical dispersion compensating element must be calculated as follows:
It is desirable to improve the wavelength characteristic curve. As one method for this, there is a method having means for adjusting the group velocity delay time-wavelength characteristic of an element capable of performing dispersion compensation.

As one of the methods, as described with reference to FIGS. 2 and 3, dispersion compensation can be performed by changing the film thickness of the light transmitting layer and the reflecting layer of the multilayer film in the direction in the incident plane. Changing the relative incident position of the signal light on the element and changing the group velocity delay time-wavelength characteristic of the element capable of performing dispersion compensation can be mentioned. The means for changing the incident position of the incident light is realized by moving at least one of the light dispersion compensator 200 or the incident position itself of the incident light with respect to the position of the incident light. As a means for moving the position of the optical dispersion compensating element or the incident light, the circumstances in which the optical dispersion compensating element is used,
Various selections can be made according to circumstances such as conditions such as cost and characteristics. For example, due to the cost or the circumstances of the device, a method of performing manual means such as a screw can be used. Also, it is possible to perform adjustment for accurate adjustment or even when adjustment cannot be performed manually. It is effective to use, for example, an electromagnetic step motor or a continuous drive motor,
It is also effective to use a piezoelectric motor using PZT (lead zirconate titanate) or the like. In addition, it is possible to easily and accurately select an incident position by using a prism or a two-core collimator that can be combined with these methods, or by selecting an incident position by an optical means such as using an optical waveguide. Can be.

Each layer of the multi-layer film of the device capable of performing dispersion compensation used in the light dispersion compensating device of the present invention is a film formed by ion-assisted deposition of SiO _{2 having} a thickness of 波長 wavelength (hereinafter referred to as ion (Also referred to as an assist film), and a layer H formed of a Ta ₂ O ₅ ion assist film having a quarter wavelength thickness. Said Si
Combination of one layer of O ₂ ion assist film (layer L) and one layer of Ta ₂ O ₅ ion assist film (layer H), LH layer 1
For example, “lamination of 5 sets of LH layers” means “layer L / layer H / layer L / layer H / layer L / layer H / layer L / layer H / layer L / layer H” The layers are sequentially formed one by one. "

Similarly, the LL layer has a thickness of ４
A layer formed by laminating two layers L composed of an ion-assist film of SiO _{2 having} a wavelength is referred to as one set of LL layers.
Therefore, for example, “three layers of LL are stacked” means “formed by stacking six layers L”.
The same applies to the HH layer.

The composition of the film forming the layer H is as follows:
Although the example of the electric body is shown, the present invention is not limited to this.
But not Ta_TwoO_FiveThe same dielectric material as_TwoO_Fiveof
In addition, TiO_Two, Nb_TwoO_FiveEtc. can be used
Furthermore, in addition to the dielectric material, the layer H is formed using Si or Ge.
It can also be done. The composition of the layer L is SiO 2 _Two
Is shown, but SiO 2_TwoIs cheap and reliable
Although there is an advantage that L can be formed, the present invention is not limited to this.
The refractive index is lower than the refractive index of the layer H
If the layer L is formed of a material, the above-described effects of the present invention can be obtained.
A light dispersion compensating element that emits light can be realized.

In the present embodiment, the layers L and H constituting the multilayer film are formed by ion-assisted vapor deposition.
The present invention is not limited to this, normal vapor deposition,
The present invention exerts a great effect even when a multilayer film formed by sputtering, ion plating or other methods is used.

The light dispersion compensating element of the present invention can be used by appropriately holding a wafer-like element such as a multilayer film 200 as a light dispersion compensating element shown in FIG. In the thickness direction, that is, in the direction from the incident surface 220 to the substrate 205, for example, in the direction of the substrate 205, for example, vertically, the chip is cut into small chips. The form has various possibilities, such as being able to be used as a dispersion compensating element, and in any case, the main effects described in the present invention are provided.

FIG. 6 is a diagram for explaining connection of elements capable of performing dispersion compensation used in the present invention.
FIG. 6B shows an example in which two elements capable of performing the dispersion compensation are connected in series to form an optical dispersion compensation element. FIG. 6B shows three elements capable of performing the dispersion compensation connected in series. FIG. 6C shows an example in which the optical dispersion compensating element is configured as shown in FIG. 6 (C). FIG. 6D shows an example in which the optical dispersion compensating element is configured by connecting
It is a figure which shows the example which mounted the optical dispersion compensation element of the same structure as (A) in one case.

In FIG. 6, reference numerals 410, 420, 43
0 and 440 are optical dispersion compensating elements, 411, 412, and 421.
423, 431, 442, and 443 are elements capable of performing dispersion compensation, and 416 is a multilayer film used in an element capable of performing dispersion compensation.
4, 426, 4261, 4262, 436, 4361,
4362, 446, 4461, 4462 are optical fibers,
413, 4131, 414, 4141, 424, 42
5, 434, 435, 444, and 445 are arrows indicating the traveling direction of the signal light, 417 is a lens, and 418 is a lens 417.
A two-core collimator comprising optical fibers 4151 and 4152, a case 441, and a multilayer film 431 having a thickness varying in the direction of incidence on the substrate to perform dispersion compensation. The devices 432 and 433, which are configured as described above and are capable of performing wafer-like dispersion compensation, are "elements capable of performing dispersion compensation". Further, among the optical fibers, reference numerals 415 and 41
52, 426, 436, and 446 are optical fibers as internal connection parts, and reference numerals 4151, 4153, 4154, and 42
61, 4262, 4361, 4362, 4461, 44
Reference numeral 62 denotes an optical fiber as an external connection component.

In FIG. 6A, the signal light incident on the element 411 capable of performing dispersion compensation from the optical fiber 4153 in the direction of arrow 413 receives the element 411 capable of undergoing dispersion compensation and performing dispersion compensation. From the optical fiber 415, and is incident on the element 412 capable of performing dispersion compensation by being transmitted through the optical fiber 415. The optical fiber 415 exits from the element 412 capable of receiving dispersion compensation and performing dispersion compensation. 4154 is transmitted.

Reference numeral 4112 is a cross-sectional view for explaining the internal structure of a portion surrounded by a broken line 4111 of the element 411 capable of performing dispersion compensation. Optical fibers 4151 and 4
The 152 and the lens 417 constitute a two-core collimator 418, and the signal light that has traveled along the optical fiber 4151 in the direction of the arrow 4131 passes through the lens 417 and enters the multilayer film 416.

The multilayer film 416 has the group velocity delay time-wavelength characteristic shown in FIG.
The signal light that has entered the multilayer film 416 through the lens 417 is subjected to third-order dispersion compensation, passes through the lens 417 again, enters the optical fiber 4152, travels in the direction of the arrow 4141, and performs dispersion compensation. Is incident on the element 412 that can be formed. The signal light that has been further subjected to dispersion compensation by the element 412 capable of performing dispersion compensation exits from the element 412 capable of performing dispersion compensation, and travels through the optical fiber 4154 in the direction indicated by the arrow 414.

The optical dispersion compensating element 410 shown in FIG. 6A has the group velocity delay time-wavelength characteristic shown in FIG. 5B, and the signal light incident on the optical dispersion compensating element 410. Is subjected to dispersion compensation according to the group velocity delay time-wavelength characteristic shown in FIG.

Similarly, in the optical dispersion compensating element 420 shown in FIG.
First, the signal light incident on the optical dispersion compensating element 420 through the optical fiber 426 is incident on the element 421 capable of performing dispersion compensation, is subjected to dispersion compensation, and is then emitted to perform dispersion compensation via the optical fiber 426. In the process of sequentially entering and exiting the elements 422 to 423 that can be
(C) is subjected to dispersion compensation according to the group velocity delay time-wavelength characteristic curve, and is emitted from the optical dispersion compensation element 420;
The optical fiber 4262 travels in the direction indicated by the arrow 425.

FIG. 6C shows a portion of the “element 431 capable of performing dispersion compensation” formed on the same wafer instead of the elements 411 and 412 capable of performing dispersion compensation in FIG. 6A. 432 and 433 ”are connected in series along the path of the signal light using the optical fiber 436.
This is the same as described for (A).

However, it is clear from the above description that the manner in which dispersion compensation is performed depends on the group velocity delay time-wavelength characteristic of an element capable of performing dispersion compensation.

FIG. 6D shows an arrangement in which elements 442 and 443 capable of performing the same dispersion compensation as in FIG. Optical dispersion compensating element 440 connected in series
Although not shown, the element 443 capable of performing dispersion compensation uses a multilayer film whose film thickness changes in the in-plane direction of the multilayer film described with reference to FIG. And has means for adjusting the incident position. Although the incident position adjusting means is not shown, the incident position can be adjusted using a control circuit provided in the case 441. The signal light enters the optical dispersion compensating element 440 via the optical fiber 4461, and exits from the optical dispersion compensating element via the optical fiber 4462.

In order to make it possible to widen the wavelength band to be subjected to dispersion compensation in the dispersion compensating element of the present invention and the dispersion compensating method using the same, as described above, for example, a multilayer film is used. By connecting a plurality of elements capable of performing dispersion compensation in series in the optical path, FIG.
What is necessary is just to comprise the dispersion compensating element as described in (1), and it is sufficient to compensate the dispersion using such a dispersion compensating element.

However, as described with reference to FIG. 6, when a plurality of elements capable of performing the dispersion compensation of the present invention are connected by using a collimator, if the number of the elements to be connected increases, the number is given. The attachment and detachment of the element becomes complicated in accordance with the specifications, which leads to an increase in manufacturing cost, and it is difficult to perform maintenance after shipping the device, resulting in a large problem such as a decrease in maintenance quality and an increase in maintenance cost.

In the present invention, a dispersion compensating element using the connection method illustrated in FIG. 7 has been proposed as a dispersion compensating element using the connection method for solving this problem.

FIG. 7 is a view for explaining an example of an actual connection method of the optical dispersion compensating element of the present invention, and FIG. 7A shows a holding section mounted with an element capable of performing dispersion compensation used in the present invention. 701 (described later) is viewed from the direction of arrow 761 in FIG. 7C, and FIG.
FIG. 7C is a diagram viewed from the direction of the arrow 762 in FIG.
(C) is a diagram illustrating a case in which the holding unit 701 is stored. In FIG. 7, reference numeral 700 denotes a dispersion compensating element,
701, 702, 703 are holding parts, 704 is a case, 7
11 and 712 are holding members, 713 is a two-core fiber collimator (hereinafter, also simply referred to as a collimator), 714 is a mounting portion of the holding member 712 on which the multilayer film element 722 is mounted, and 721 is
Denotes a lens, 722 denotes a multilayer element as an element capable of performing dispersion compensation, 723 denotes an optical fiber, 725, 72
Reference numeral 6 denotes a stopper provided on the case 704 and a holding member 71.
1 and 712 play a role in positioning when mounted on the case 704, and 731 to 734 are springs, 741
762 are arrows.

In FIG. 7, a lens 721 and an optical fiber 723 constitute a collimator 713, and are held by a holding member 711. The collimator 71
3, the lens 721 is held by the holding member 711 such that the holding member 711 is attached to the case 704 so as to have a focal point at the position of the incident surface of the multilayer element 722. The optical path of the signal light can be freely designed. And, it is mounted on the case 704 so as to correspond to a reference surface (described later) of the case 704. In addition, the holding member 711 can be provided with a screw. In that case, the case 704 is provided with a screw.
Even when the holding member 711 detachable from the case 704 is mounted, the holding member 711 can be held at a position determined by the reference surface of the case 704 with high accuracy and easily.

The multilayer element 722 is arranged such that the focus of the lens 721 is on the incident surface of the multilayer element 722 when the holding member 712 is mounted on the case 704.
2 is mounted on the second mounting section 714. Also, a plurality of the multilayer elements 722 can be mounted on the holding member 712, and the group velocity delay time-wavelength characteristic curve can be freely designed. Further, the holding member 712 can be provided with a screw similarly to the holding member 711. In this case, the case 704 is provided with a screw as in the case of the holding member 711.

When the holding member 711 is mounted on the case 704, as shown in FIG. 7A, it is pressed by the spring 731 in the directions indicated by the arrows 741 and 742, as shown in FIG. Arrow 751 by spring 733
And is attached to the case 704 by being pressed in the direction indicated by the arrow 752 and the arrow 745 and the arrow 74.
7, a reference surface indicated by an arrow 749, a reference surface indicated by an arrow 759, and a stopper 725, a stopper 726, and the case 704 provided on the case 704. The case 704 is brought into contact with an inner side surface corresponding to each reference surface of the holding member.
It is placed on. Then, in a state where the holding member 711 is mounted at a position determined by the three reference surfaces of the case 704, a screw that can be mounted on the holding member 711 or the holding member 711 from outside the case 704. It is also possible to fix the holding member 711 with a fixing tool or the like that can fix the holding member 711.

Similarly, the holding member 712 is
04, the spring 73 as shown in FIG.
2, and is pressed in the directions indicated by arrows 753 and 754 by a spring 734 and attached to the case 704 as shown in FIG. And a reference surface indicated by an arrow 748, a reference surface indicated by an arrow 750, and a reference surface indicated by an arrow 760 at positions determined by three reference surfaces. The holding member 704 is placed on the case 704 so as to be in contact with an inner surface corresponding to each reference surface of the holding member. Then, in a state where the holding member 712 is mounted at a position determined by the three reference surfaces of the case 704, a screw or the case 704 that can be mounted on the holding member 712 is provided.
It is also possible to fix the holding member 712 by a fixing tool or the like that can fix the holding member 712 from outside. Further, a screw or a screw hole can be attached to the stopper 725 and the stopper 726. In that case, a screw can be provided on the case 704, and the holding member 711 and the holding member 712 can be attached and detached. In this case, the positional relationship between the holding member 711 and the holding member 712 can be accurately and easily determined, that is, the lens 721 mounted on the holding member 711 and the multilayer film element 722 mounted on the holding member 712 can be used. Can be maintained.

For the purpose of mounting and fixing the holding member to the case, instead of screws or screw holes, for example, a spring-like fixing tool is provided on at least one of the case and the holding member. By using means for simply fixing the optical dispersion compensating element, a highly reliable and easy-to-handle optical dispersion compensating element can be realized.

As shown in FIG. 7B, the signal light incident on the collimator 713 of the holder 701 travels in one of the two optical fibers 723 in the direction indicated by the arrow 755. The light enters the lens 721 from the end 724 of the optical fiber 723, changes its optical path in the direction shown by the arrow 756, enters the multilayer element 722, undergoes dispersion compensation, is reflected in the direction shown by the arrow 757, and 721
Again, is incident on the other optical fiber of the two optical fibers 723, travels in the direction indicated by the arrow 758, and is transmitted to the outside of the holding unit 701. The signal light emitted from the collimator 713 can be transmitted to the holding units 702 and 703.

As described above, the dispersion of the signal light is a predetermined amount by the multilayer element 722 as an element capable of performing dispersion compensation, that is, the group velocity delay time-wavelength characteristic curve of the multilayer element 722 is plotted. 5, is compensated by an amount determined by the group velocity delay time-wavelength characteristic curve resulting from the superposition. Here, when it is necessary to change the group velocity delay time-wavelength characteristic of the optical dispersion compensating element according to the content required for dispersion compensation, the holding unit of the present invention is configured to be detachable, Since the connection of the collimator mounted on the section can be easily changed, the content of the optical dispersion compensating element can be easily changed by appropriately increasing or decreasing the number of the multilayer films. Depending on the transmission state of the signal light, it is preferable to appropriately select the content of the dispersion compensation.However, in the optical dispersion compensation element and the optical dispersion compensation method of the present invention, as described above, the holding unit is configured to be detachable, By using a holding unit that can easily change the connection of the collimator of the holding unit, for example, a multilayer film is selected as an element that can perform dispersion compensation mounted thereon, and a light dispersion compensation having predetermined characteristics is selected. The element can be easily configured, and good optical dispersion compensation can be easily performed using the element.

Using such an optical dispersion compensating element according to the present invention, as a result of compensating dispersion in a communication system transmitting 60 km at a communication bit rate of 40 Gbps,
In addition to being able to perform very good dispersion compensation, the loss due to signal light passing through the optical dispersion compensation element is extremely low as compared with a conventional dispersion compensation element using a fiber grating. Met.

The light dispersion compensating element of the present invention and the light dispersion compensating method using the element have been described centering on the light dispersion compensating element of the present invention. The most remarkable features of the light dispersion compensating method of the present invention are described above. Since the internal connection component and the external connection component used in the present invention have the same structure, they are interchangeable, and a plurality of elements capable of performing dispersion compensation are detachably connected in series to provide a wide wavelength range. The second and third-order dispersion compensation is made possible in a band, and high-speed and long-distance communication is made possible by utilizing many conventional optical communication systems. The bandwidth of the wavelength band for dispersion compensation enables compensation over a wide range such as 15 nm and 30 nm.

[0102]

As described above, the present invention has been described in detail. According to the present invention, in preparing various group velocity delay time-wavelength characteristic curves described with reference to FIGS. A holding member (referred to as a holding member I) for mounting the element capable of performing dispersion compensation as shown in FIG.
A configuration in which a holding member (referred to as a holding member II) for mounting a collimator having, for example, an optical fiber and a lens as a connection portion is provided, and the holding member I and the holding member II are opposed to each other and can be detachably mounted on a case. With this configuration, an optical dispersion compensating element having a desirable group velocity delay time-wavelength characteristic curve can be easily realized. Since each holding member is positioned by a positioning tool such as a spring and a stopper, the positioning accuracy is good, the optical path of the signal light can be easily formed with extremely low loss, and the good dispersion compensation of each channel can be achieved. In addition, since the connection of the holding member can be easily changed, an optical dispersion compensating element that can also perform excellent dispersion compensation for a plurality of channels can be easily configured. With such a configuration, maintenance is also facilitated.

The dispersion compensation by the optical dispersion compensating element of the present invention has a particularly large effect in the third or higher order dispersion compensation, and in addition, by appropriate adjustment of the group velocity delay time-wavelength characteristic, the second order dispersion compensation. It can also perform dispersion compensation.

[0104] The dispersion compensation method of constructing a substantial dispersion compensating element according to the above technical idea of the dispersion compensating element of the present invention and performing dispersion compensation makes it possible to utilize many existing optical communication systems. In making it possible, the social and economic effects are enormous.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining optical dispersion compensation according to the present invention.

FIG. 2 is a sectional view of a multilayer film of the present invention.

FIG. 3 is a perspective view of a multilayer film of the present invention.

FIG. 4 is a diagram illustrating a group velocity delay time-wavelength characteristic curve of the multilayer film of the present invention.

FIG. 5 is a diagram illustrating a method of improving group velocity delay time-wavelength characteristics using a plurality of elements capable of performing dispersion compensation according to the present invention.

FIG. 6 is a diagram illustrating connection of a light dispersion compensation element.

FIG. 7 is a diagram illustrating an example of an actual connection method of the optical dispersion compensating element of the present invention.

FIG. 8 is a diagram illustrating a method of compensating for second and third order chromatic dispersion.

FIG. 9 is a graph showing dispersion-wavelength characteristics of a conventional optical fiber.

[Explanation of symbols]

100, 200: multilayer film 101, 230: arrow indicating the direction of incident light 102, 240: arrow indicating the direction of outgoing light 103, 104, 105, 201, 202, 203: reflective layer 108, 109, 206, 207: Light transmitting layers 107, 205: substrates 111, 112, 211, 212: cavities 220: light incident surfaces 250, 260: arrows indicating the direction in which the film thickness changes 270, 271: arrows 271 indicating the direction of moving the incident position of the incident light : Curve adjustment direction 280, 281, 282: Incident position 1101, 1102, 1103, 2801, 2811
2812, 301 to 312: Group velocity delay time-wavelength characteristic curve 410, 420, 430, 440: Optical dispersion compensation element 411, 412, 421 to 423, 431, 442, 4
43: element capable of performing dispersion compensation 416: multilayer film 415, 4151 to 4154, 426, 4261, 42
62,436,4361,4362,446,446
1,4462: Optical fibers 413, 4131, 414, 4141, 424, 42
5,434,435,444,445: Arrow 417: Lens 418: Two-core collimator 432,433: Element part capable of performing dispersion compensation 441: Case 501,502,503,504,511,512,5
13, 514: Graph showing characteristics of signal light 520, 530: Transmission line 521: Dispersion compensating fiber 522, 531: SMF 524, 534: Transmitter 525, 535: Receiver 601: SMF dispersion-wavelength characteristic curve 602: Dispersion-Wavelength Characteristic Curve of Dispersion Compensating Fiber 603: DSF Dispersion-Wavelength Characteristic Curve 700: Optical Dispersion Compensating Element 701, 702, 703: Holding Unit 704: Cases 711, 712: Holding Member 713: Two-Core Fiber Collimator 714: Mounting Part 721: Lens 722: Multilayer film element 723: Optical fiber 724: End 725, 726: Stopper 731 to 734: Spring 741 to 762: Arrow

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yuichi Takushima 2-22-7 Hiyoshihoncho, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Charman Hiyoshi 202 Room 202 (72) Inventor Mark Kennes Jaboronski 4-6-1 Komaba, Meguro-ku, Tokyo No. 29 K518 (72) Inventor Yuichi Tanaka 3-1-23 Niisonanami, Toda City, Saitama Prefecture Applied Optics Laboratory (72) Inventor Haruki Kataoka 3-1-23 Niisonanami, Toda City, Saitama Prefecture Applied Company Photoelectric Laboratory (72) Inventor Kenji Furushiro 3-1-23 Niisonanami, Toda City, Saitama Prefecture Applied Photonics Laboratory (72) Inventor Shin Shin Higashi 3-1-23-1 Nishinami, Toda City, Saitama Prefecture Applied Company Photoelectric Laboratory (72) Inventor Kazuya Sato 3-1-23-1 Nishinaminami, Toda City, Saitama Prefecture Applied Photonic Laboratory (72) Invention Shiro Yamashita Toda City, Saitama Prefecture Nizominami 3 chome No. 23 stock company applied photoelectric laboratory F-term (reference) 2H037 AA01 BA32 CA00 2H048 GA07 GA09 GA12 GA34 GA51 GA60 GA62 5K002 AA07 CA01 DA14

Claims (26)

[Claims] An optical dispersion compensating element (hereinafter, also referred to as a dispersion compensating element) capable of compensating chromatic dispersion (hereinafter, also referred to simply as dispersion) by using an optical fiber for communication using a communication transmission line. The optical dispersion compensating element may include at least two elements capable of performing dispersion compensation in a communication path of signal light, or a part of an element capable of performing dispersion compensation (hereinafter referred to as performing the dispersion compensation. The element that can perform dispersion compensation and the element that can perform dispersion compensation are collectively referred to as an element that can perform dispersion compensation), and at least two locations are connected in series via at least a pair of holding members. At least one element capable of performing the dispersion compensation is mounted on one of the pair of holding members (hereinafter, also referred to as a holding member A), An optical fiber collimator composed of an optical fiber and a lens is mounted on the other holding member (hereinafter, also referred to as holding member B) of the pair of holding members, and the holding member A and the holding member are provided. B
Wherein a plurality of pairs of the holding members A and the holding members B are mounted on one case so as to face each other. 2. The optical dispersion compensating element according to claim 1, wherein the holding member A and the holding member B are incorporated in the case into at least one of the pair of holding members A and B and the case. An optical dispersion compensating element, further comprising a positioning means for positioning the element capable of performing the dispersion compensation and the optical fiber collimator disposed opposite thereto. 3. The optical dispersion compensating element according to claim 1, wherein the holding member A and the holding member B are provided in the case.
When the optical fiber collimator of the holding member B is installed, the focal point of the optical fiber collimator is located on the incident surface of the element capable of performing the optical dispersion compensation mounted on the holding member A, and is positioned at the time of installation into the case. An optical dispersion compensating element characterized in that: 4. The optical dispersion compensating element according to claim 3, wherein said positioning means provided on said pair of holding members A and B is means for positioning by engaging with said case. Characteristic light dispersion compensating element. 5. The optical dispersion compensating element according to claim 4, wherein said positioning means comprises: said case and said holding member A;
And a reference surface provided on at least one of the holding members B. 6. The optical dispersion compensating element according to claim 5, wherein said reference plane is three planes orthogonal to each other. 7. The optical dispersion compensating element according to claim 6, wherein a spring acting to press the holding member A and the holding member B in the direction of the reference plane is at least one of the holding member A and the case. An optical dispersion compensating element, which is provided at at least one location and at least one location of at least one of the holding member B and the case. 8. The optical dispersion compensating element according to claim 1, wherein a screw can be attached to at least one of the case and the holding member A and at least one of the case and the holding member B. Wherein the holding member A and the holding member B can be fixed to the case by screwing. 9. The optical dispersion compensating element according to claim 1, wherein the element capable of performing the dispersion compensation is an element having a multilayer film. . 10. The optical dispersion compensating element according to claim 9, wherein the multilayer film of the element capable of performing the dispersion compensation has at least one extreme value in a wavelength range of 1460 to 1640 nm of incident light. An optical dispersion compensating element having a group velocity delay time-wavelength characteristic as follows. 11. The light dispersion compensating element according to claim 9, wherein the multilayer film has at least two reflective layers having different light reflectivities, and at least one light formed between the reflective layers. An optical dispersion compensating element having a transmission layer. 12. The optical dispersion compensating element according to claim 9, wherein the element capable of performing the dispersion compensation comprises at least five types of laminated films having different optical properties (ie, light A multilayer film having at least five stacked films having different optical properties such as reflectance and film thickness, wherein the multilayer film includes at least two types of reflective layers having different light reflectances from each other. Types of reflective layers, and at least two types in addition to the three types of reflective layers.
Three light-transmitting layers, each one of the three types of reflective layers and each one of the two light-transmitting layers are alternately arranged,
The multilayer film is formed in a first order from one side in the thickness direction of the film.
A first layer that is a reflective layer, a second layer that is a first light transmitting layer,
The third layer, which is the second reflection layer, and the fourth layer, which is the second light transmission layer.
And a fifth layer, which is a third reflective layer, where the central wavelength of the incident light is λ, and in the first to fifth layers, an optical path length (hereinafter, referred to as a light) having a central wavelength λ of the incident light. The thickness of each layer of the multilayer film (hereinafter, simply referred to as the film thickness or the thickness of the film) when considered as an optical path length is simply a value in a range of an integral multiple of λ / 4 ± 1% (hereinafter, also referred to as a film thickness). , Λ / 4
And the film thickness of the multilayer film is １ of λ (hereinafter １ of λ ± 1%). A layer having a higher refractive index (hereinafter, also referred to as a layer H) having a thickness of 1/4 times λ and a layer having a lower refractive index having a thickness of 1/4 times λ. The multi-layer film A is composed of a plurality of sets of layers (hereinafter, also referred to as layers L).
The layer is a layer (hereinafter, referred to as HL) in which one layer is combined with each of layers H and L in order from one side in the thickness direction of the multilayer film.
(A layer obtained by combining the layer H1 layer and the layer L1 layer is referred to as an HL layer 1 set; the same applies hereinafter).
A first layer formed by lamination, a layer obtained by combining layers H and H (that is, a layer formed by laminating two layers H. Hereinafter, H
H) (10 layers).
The third layer is formed by laminating one set of layers L and 7 sets of HL layers, the fourth layer is formed by stacking 38 sets of HH layers, and the third set of layers L is formed of one layer and HL. A multilayer film formed by laminating 13 sets of layers and a fifth layer formed by laminating 13 sets; and a multilayer film B formed by laminating 10 sets of HH layers of the multilayer film A. Instead of the second layer of membrane A,
The second layer is, in order from one side in the thickness direction of the film in the same direction as that of the multilayer film A, three sets of HH layers and a layer obtained by combining the layers L and L (that is, two layers L A layer formed by laminating three sets of LL layers, three sets of HH layers, two sets of LL layers, and one set of HH layers in this order. Instead of the fourth layer formed by stacking 38 sets of HH layers in the multilayer film A or B, the fourth layer is a multilayer film A. , Three sets of HH layers and LL in order from one side in the thickness direction of the film in the same direction as
3 layers, 3 sets of HH layers, 3 sets of LL layers, 3 sets of HH layers, 3 sets of LL layers, HH
3 layers, 3 sets of LL layers, 3 sets of HH layers, 3 sets of LL layers, 3 sets of HH layers, LL
And three sets of HH layers, three sets of LL layers, and two sets of HH layers are stacked in this order to form a multilayer film. , The five-layer laminated film, that is, the first to fifth layers
The layers are layers (hereinafter referred to as LH) in which layers are combined one by one in the order of layer L and layer H from one side in the thickness direction of the multilayer film.
), A first layer formed by stacking five sets of
A second layer formed by stacking seven sets of LL layers, a third layer formed by stacking one layer H and seven sets of LH layers.
Layer, a fourth layer configured by stacking 57 sets of LL layers,
The layer H is a multilayer film composed of a fifth layer formed by laminating one layer and 13 sets of LH layers, and the multilayer film E is a laminated film of the five layers, that is, the first to the first layers. 5
The layers are HL in order from one side in the thickness direction of the multilayer film.
A first layer formed by laminating two sets of HH layers, a second layer formed by laminating 14 sets of HH layers, one layer L and one layer H
HH, a third layer composed of six sets of L layers
Layer L, which is formed by laminating 24 sets of
Layer 13 composed of 13 sets of layers and HL layers
A multi-layer film formed of a plurality of layers, wherein the second layer is a multi-layer film instead of the second layer formed by laminating 14 sets of the HH layers of the multi-layer film E; In the order from one side in the thickness direction of the film in the same direction as in E, three sets of HH layers, three sets of LL layers, three sets of HH layers, three sets of LL layers, and three sets of HH layers Two sets, one set of LL layers, and one set of HH layers are laminated in this order to form a multilayer film formed of a laminated film, and the multilayer film G is the HH of the multilayer film E or F. Layer 2
Instead of the fourth layer formed by laminating four sets, the fourth layer is composed of three sets of layers of HH and LL in order from one side in the thickness direction of the film in the same direction as that of the multilayer film E. 3 layers, 3 sets of HH layers, 3 sets of LL layers,
3 sets of HH layers, 3 sets of LL layers, 3 sets of HH layers, 3 sets of LL layers, 2 sets of HH layers,
One set of LL layers and one set of HH layers are laminated in this order to form a multilayer film composed of a laminated film, and the multilayer film H is a laminated film of five layers, that is, the first to first layers. 5
The layers are sequentially LH from one side in the thickness direction of the multilayer film.
A first layer formed by laminating four sets of layers, a second layer formed by laminating nine sets of layers LL, one layer H and LH
The third layer is formed by laminating 6 sets of layers, the fourth layer is formed by laminating 35 sets of LL layers, one layer H is formed by laminating 13 sets of LH layers. When a multilayer film formed of the fifth layer is formed, the element capable of performing the dispersion compensation has at least one of the multilayer films A to H. Compensating element. 13. The optical dispersion compensating element according to claim 9, wherein a thickness of at least one laminated film constituting the multilayer film is parallel to a light incident surface of the multilayer film. An optical dispersion compensating element that changes in an in-plane direction (hereinafter, also referred to as an incident plane direction) in a simple cross section. 14. The optical dispersion compensating element according to claim 13, wherein the adjusting means adjusts the film thickness of at least one of the multilayer films by engaging with the element capable of performing the dispersion compensation. Alternatively, there is provided a light dispersion compensating element provided with means for changing a light incident position on an incident surface of the multilayer film. 15. The optical dispersion compensating element according to claim 1, wherein the optical dispersion compensating element can mainly compensate for third-order dispersion. 16. An optical dispersion compensating element according to claim 1, wherein said optical dispersion compensating element is capable of compensating for second-order dispersion. 17. The optical dispersion compensating element according to claim 12, wherein the layer H is made of Si, Ge,
An optical dispersion compensation element comprising a layer containing at least one of TiO ₂ , Ta ₂ O ₅ , and Nb ₂ O ₅ as one of main components. 18. The optical dispersion compensating element according to claim 12, wherein the layer L is formed using a material having a lower refractive index than the material used for the layer H. A light dispersion compensation element. 19. The light dispersion compensating element according to claim 12, wherein the layer L is formed of a layer containing SiO ₂ as one of the main components. Dispersion compensating element. 20. In communication using an optical fiber for a communication transmission line, chromatic dispersion (hereinafter, simply referred to as dispersion) using an optical dispersion compensating element (hereinafter, also referred to as dispersion compensating element).
Wherein the optical dispersion compensating element comprises at least two elements capable of performing dispersion compensation.
Or an element capable of performing dispersion compensation (hereinafter, an element capable of performing dispersion compensation and an element capable of performing dispersion compensation are collectively referred to as an element capable of performing dispersion compensation) ) Are connected in series via at least a pair of holding members in a signal light communication path, and one of the pair of holding members (hereinafter, holding) At least one element capable of performing the dispersion compensation is provided in the member A), and the other of the pair of holding members (hereinafter, also referred to as a holding member B) is provided with an optical fiber collimator. And the holding member A
And a plurality of holding members A and a plurality of holding members B are disposed so as to face each other to perform dispersion compensation. 21. The optical dispersion compensation method according to claim 20, wherein an element having a multilayer film is used as the element capable of performing the dispersion compensation. 22. The optical dispersion compensating method according to claim 21, wherein the group velocity of the multilayer film of the optical dispersion compensation element has a curve having at least one extreme value in a wavelength range of 1460 to 1640 nm of incident light. An optical dispersion compensation method comprising using a multilayer film having a delay time-wavelength characteristic. 23. The optical dispersion compensation method according to claim 21, wherein a thickness of at least one of the multilayer films constituting the multilayer film is parallel to a light incident surface of the multilayer film. An optical dispersion compensation method characterized by using a multilayer film that changes in an in-plane direction (hereinafter, also referred to as an incident plane direction) in a simple cross section. 24. The optical dispersion compensating method according to claim 23, wherein the dispersion compensating system is engaged with an element capable of performing the dispersion compensation to form at least one of the multilayer films. An optical dispersion compensating method, comprising an adjusting means for adjusting a film thickness or a means for changing a light incident position on an incident surface of the multilayer film. 25. The optical dispersion compensating method according to claim 20, wherein the optical dispersion compensating element can mainly compensate for third-order dispersion. 26. The optical dispersion compensating method according to claim 20, wherein the optical dispersion compensating element is
An optical dispersion compensation method, wherein the following dispersion can be compensated.