JP3262312B2 - Optical dispersion equalizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal which is distorted by being propagated through an optical fiber having a dispersion and which is distorted by a high-order dispersion effect (an effect that a dispersion characteristic slope is present and a relative delay time characteristic having a frequency of 2). The present invention relates to an optical dispersion equalizer that performs waveform shaping including an effect that varies with the following function).

[0002]

2. Description of the Related Art When an optical fiber having a zero dispersion at a wavelength of λ = 1.3 μm (most existing optical fibers such as the Japan Longitudinal Optical Communication Line) is used at a minimum loss band of λ = 1.55 μm. , The propagation delay time τ decreases as the frequency increases due to the dispersion of the optical fiber (the propagation speed increases). For this reason, the distortion of the optical signal pulse increases, so that the transmission capacity or the transmission (relay) distance is limited.

[0003] Conventionally, as a dispersion equalizer for shaping a signal distorted by propagating through an optical fiber having dispersion, a metal conductor 32 is provided on both sides of a dielectric 31 as shown in FIG.
A microwave strip line provided with a and 32b is known.

A microwave strip line has the propagation delay time characteristics shown in FIG. 14, and the propagation delay time τ increases (the propagation speed decreases) as the optical frequency increases. In FIG. 14, 1 _MS is the length of the strip line.

Since the delay time characteristic shown in FIG. 14 is opposite to the delay characteristic of the optical fiber, the optical signal is converted into an electric signal by a photoelectric converter (photodetector) and then passed through a strip line to thereby transmit the optical fiber. Can be offset.

[0006]

In the above-described dispersion equalizer having the conventional structure, it is necessary to convert an optical signal into an electric signal once to shape the waveform, and (1) all-optical relay cannot be performed. (2) There is a problem that the conductor loss of the strip line increases as the signal frequency increases, and (3) it can be applied only to coherent optical transmission that performs heterodyne detection. Further, in most regions, the delay time characteristic changes linearly with respect to frequency, and therefore, there is a problem that (4) it is difficult to compensate for the effect of higher-order dispersion.

The present invention has been made in view of the above-mentioned prior art, and is different from a conventional dispersion equalizer that compensates only for a delay time characteristic that changes linearly with frequency. Provided is an optical dispersion equalizer suitable for large-capacity, long-distance optical communication, which enables a signal distorted by performing optical shaping to compensate for the effect of higher-order dispersion as it is and to shape the waveform. The purpose is to do so.

[0008]

According to a first aspect of the present invention, there is provided a first optical waveguide, a second optical waveguide, and an N coupling the first and second optical waveguides at different locations.
+1 (N is an integer) coupling rate variable directional coupler,
The optical path lengths of the first and second optical waveguides at respective portions sandwiched between two adjacent ones of the N + 1 directional couplers are different from each other, and two adjacent ones of the N + 1 directional couplers are different from each other. An optical waveguide circuit in which a phase controller is provided in at least one of the first and second optical waveguides in each of the portions sandwiched between the optical waveguide circuits, and an optical waveguide circuit provided in at least one of the input / output units of the optical waveguide circuit. Linear with light frequency
And a dispersion compensator having a relative delay time characteristic,
The optical waveguide circuit has a convex shape with respect to the frequency of the optical fiber.
Optical waveguide circuit with relative delay time characteristics approximated by
An optical dispersion equalizer, characterized in that it.

According to a second aspect of the present invention, there is provided an optical waveguide group including a first optical waveguide, a second optical waveguide, and I (I is an integer of 2 or more) optical waveguides, and the optical waveguide group. I coupling rate variable directional couplers for coupling the I optical waveguides to different portions of the first optical waveguide on one end side thereof, and each of the I optical waveguides of the optical waveguide group A merger that collectively outputs signals input from the other end to the second optical waveguide, and is provided between the directional coupler and the merger of each of the I optical waveguides of the optical waveguide group. An optical waveguide circuit having a phase controller, and provided in at least one of the input / output units of the optical waveguide circuit.
And a dispersion compensator having a linear relative delay time characteristic.
The optical waveguide circuit is provided with respect to the frequency of the optical fiber.
Has a relative delay time characteristic approximated by a quadratic equation that is convex upward
An optical dispersion equalizer characterized by being an optical waveguide circuit .

[0010]

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the first embodiment of the present invention, N + 1 (N is an integer) coupling the first optical waveguide, the second optical waveguide, and the first and second optical waveguides at different positions, respectively. Wherein the optical path lengths of the first and second optical waveguides of each portion sandwiched between two adjacent ones of the N + 1 directional couplers are different from each other,
And a two-input two-output optical waveguide circuit in which a phase controller is provided in at least one of the first and second optical waveguides of each portion sandwiched between two adjacent N + 1 directional couplers. By setting the phase of the phase controller and the coupling ratio of the variable coupling directional coupler to appropriate values, it is possible to obtain a group delay time characteristic expressed by a quadratic equation that is upwardly convex with respect to frequency.

Therefore, at least one of the two input portions and the two output portions of the above optical circuit,
By providing a means for compensating the dispersion of the optical fiber, by linearly changing the relative delay time by changing the frequency,
The above-mentioned optical circuit compensates for the group delay time characteristic expressed by a quadratic equation that is convex downward with respect to the frequency of the optical fiber, and the above-mentioned dispersion compensation means shares the group delay time characteristic that changes linearly with frequency. Thus, it is possible to compensate for the influence of the dispersion of the optical fiber, including the influence of the higher-order dispersion.

In a second embodiment of the present invention, a first optical waveguide, a second optical waveguide, an optical waveguide group composed of I optical waveguides (I is an integer of 2 or more), and I optical waveguide groups of the optical waveguide group. I coupling rate variable directional couplers for coupling the optical waveguides to different portions of the first optical waveguide on the one end side, respectively, and input from the other end of each of the I optical waveguides of the optical waveguide group. One-input one having a coupler for outputting the combined signals to the second optical waveguide, and a phase controller provided between the directional coupler and the coupler of each of the I optical waveguides of the optical waveguide group.
By setting the phase of the phase controller and the coupling of the variable coupling directional coupler to appropriate values, the output optical waveguide circuit has a group delay time characteristic expressed by a quadratic equation that is upwardly convex with respect to frequency. Can be obtained.

Therefore, at least one of two input and one output portions of the above optical circuit,
By providing a means for compensating the dispersion of the optical fiber, by linearly changing the relative delay time by changing the frequency,
The above-mentioned optical circuit compensates for the group delay time characteristic expressed by a quadratic equation that is convex downward with respect to the frequency of the optical fiber, and the above-mentioned dispersion compensation means shares the group delay time characteristic that changes linearly with frequency. Thus, it is possible to compensate for the influence of the dispersion of the optical fiber, including the influence of the higher-order dispersion.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments shown in the drawings.

FIG. 1 shows a first embodiment of the optical dispersion equalizer according to the present invention. FIG. 1 shows an example in which N = 8, that is, the first optical waveguide 1 and the second optical waveguide 2 are coupled at N + 1 = 9 locations by the coupling ratio variable directional couplers 3a to 3i, respectively. . The optical waveguides 1 and 2 are respectively divided into ten sections 1a to 1 by directional couplers 3a to 3i.
1j, 2a to 2j, and the optical path length of each section 1b to 1i of the optical waveguide 1 sandwiched by the adjacent directional couplers is set to the corresponding section 2b of the corresponding optical waveguide 2.
Ｉ2i. Furthermore, each section 1b-1 of the optical waveguide 1 sandwiched between adjacent directional couplers
Phase controllers 4a to 4h are provided in at least one of the sections 2b to 2i of the optical waveguide 2 corresponding to i. This embodiment shows an example in which a phase controller is provided only on the optical waveguide 1 side. The ends 1a and 1j of the optical waveguide 1 are an input section and an output section, respectively, and similarly, the ends 2a and 2j of the optical waveguide 2 are an input section and an output section, respectively.
An optical fiber is connected to at least one of these input units and at least one of the output units. At least one of the four input / output units is provided with a dispersion compensator for compensating the dispersion of the optical fiber. In this embodiment, the input unit 1 of the optical waveguide 1
An example in which a dispersion compensator 5 whose relative delay time changes linearly with a change in frequency is provided only in a. The larger the number N of the portions sandwiched by the directional couplers, the greater the compensation effect, but the more complicated the device configuration. On the other hand, if N is small, the compensation effect is not sufficient. A preferred range for N is 4 to 16.

The phase controllers 4a to 4h are for controlling the phase of light propagating through the optical waveguides under the phase controllers 4a to 4h, and known ones can be used.

FIGS. 2 and 3 show examples of the configuration of the variable coupling ratio directional couplers 3a to 3j shown in FIG.

The variable coupling rate directional coupler shown in FIG.
The two optical waveguides 6 and 7 are arranged close to each other, and various coupling rates can be obtained by changing the coupling length.

The variable coupling ratio directional coupler shown in FIG.
A plurality of optical waveguides 8 and 9 and a plurality of adjacent portions 10a to 10 coupling the two optical waveguides at a plurality of different positions;
d, the optical waveguide portions sandwiched between adjacent adjacent portions, that is, the optical waveguides 8b and 9b, the optical waveguides 8c and 9c, and the optical waveguides 8d and 9d have the same optical path length and are sandwiched between adjacent adjacent portions. At least one of the two optical waveguides is provided with phase controllers 11a to 11c. In this example, the case where the proximity portion is 4 is shown, and the phase controller is the optical waveguide 8.
The example provided only on the side is shown. Phase controllers 11a-1
The phase of the light can be adjusted using 1c, whereby an arbitrary coupling ratio is obtained, and the device operates as a variable coupling ratio directional coupler.

Referring to FIG. 1, in accordance with the teachings of Jinguji, et al., The phase controllers 4a to 4h are used to appropriately adjust the phase of the optical waveguide, and the coupling ratio is changed.
By setting the coupling ratio of 3i to an appropriate value, the group between (the optical waveguide 1a '(the output side of the dispersion compensator 5) or the optical waveguide 2a) and (the optical waveguide 1j or the optical waveguide 2j) becomes a group. An element whose delay time characteristic can be approximated to a function of an arbitrary frequency can be configured (for example, K. Jin
"Synthesis ofcohe by Guji et al.
rent two-port lattice-for
optical delay-line circ
uit ”, Journal of Lightwave
Technology, vol. 13, No. 1, p
p. 73-82, January 1995).

FIG. 4 is a calculation example of the relative delay time characteristics of the optical fiber having the zero dispersion frequency f ₀ including the influence of the higher-order dispersion (optical fiber length: 1 = 150 km, dispersion slope of the optical fiber: ( 0.06 psec / nm ² / km) The relative delay time characteristic τ _f (f) is a quadratic curve that is convex downward with respect to the frequency f, as represented by the following equation.

[0023]

Τ _f (f) = a (f−f ₀ ) ² + d (Equation 1) where a is a constant determined by the dispersion slope and the fiber length, and the sign is positive and d is a constant.

FIG. 5 shows the optical waveguides (1b and 2b) in FIG.
b), (1c and 2c), (1d and 2d), (1e and 2
e), (1f and 2f), (1g and 2g), (1h and 2g)
h), optical path length difference ΔL = 0.517 m between (1i and 2i)
m, the relative delay time characteristic that can be realized as the characteristic between (optical waveguide 1a 'or optical waveguide 2a) and (optical waveguide 1j or optical waveguide 2j) in FIG. 1 when the refractive index of the optical waveguide is 1.45. Is a calculation example of The relative delay time characteristic is approximately approximated to a quadratic curve that is convex upward with respect to the frequency, and the following relative delay time characteristic τ _eq1 (f) can be realized.

[0025]

Τ _eq1 (f) = − a (f−f ₁ ) ² + b (Equation 2) where f ₁ is a frequency representing a vertex of the horizontal axis, and b is a constant.

The relative delay time characteristic τ _eq2 (f) of the dispersion compensator for compensating the dispersion of the optical fiber whose relative delay time changes linearly with the change of the frequency is represented by

[0027]

Τ _eq2 (f) = 2a (f ₀ −f ₁ ) f + c By setting as shown in (Equation 3), the relative delay time characteristic of light input from 1a in FIG. 1 and output from 1j or 2j Is represented by the following equation as the sum of (Equation 1) to (Equation 3).

[0028]

Equation 4] _{τ f (f) + τ eq1} (f) + τ eq2 (f) = a (f 0 2 -f 1 2) + b + c ( constant) (Equation 4) Therefore, the relative delay time characteristic that does not change with frequency is obtained Thus, it can be understood that the dispersion of the optical fiber including the influence of the higher-order dispersion can be compensated using the configuration of FIG.

As means for compensating the dispersion of the optical fiber, a dispersion compensating fiber, a chirped Bragg grating dispersion equalizer, a two-mode fiber dispersion equalizer, Gi
A res-Tournois interferometer dispersion equalizer, a lattice configuration dispersion equalizer, a transversal configuration dispersion equalizer, or the like can be used.

The lattice dispersion equalizer shown in FIG. 6 is an example of a configuration of a means for compensating for dispersion of an optical fiber in which a relative delay time changes linearly with a change in frequency. The figure shows an example in which an asymmetric Mach-Zehnder interferometer is cascaded in five stages, and includes an optical waveguide 12 (12a to 12g), an optical waveguide 13 (13a to 13g), directional couplers 14a to 14f having a coupling rate of 50%, and a phase. It is composed of controllers 15a to 15e.

In FIG. 6, the phase controllers 15a to 15e
When the phase of the arm of the asymmetric Mach-Zehnder interferometer is adjusted by appropriately adjusting
2a or 13a) and (optical waveguide 12g or 13g).
g), a delay element whose group delay time linearly increases or decreases with respect to frequency can be configured (for example, “Plan” by K. Takiguchi et al.).
ar lightwave circuit optimal
cal distortion equalize
r ", IEEE Photonics Technology
oggy Letters, vol. 6, No. 1, p
p. 86-88, January 1994).

FIG. 7 shows an example of a group delay time characteristic which can be realized by the configuration of FIG. 6 and changes linearly with frequency. In FIG. 6, the optical path length difference ΔL between the optical waveguides 12b and 13b
₁ = 4.276 mm, (optical waveguides 12c and 13c),
(Optical waveguides 12d and 13d), (waveguides 12e and 13
e) optical path length difference ΔL ₂ = 7.483 mm, optical waveguide 1
This is a calculated value when the optical path length difference ΔL ₃ between 2f and 13f is 3.207 mm and the refractive index of the optical waveguide is 1.45.

By adjusting the phase, two characteristics indicated by a solid line and a dotted line are obtained. In any case, a group delay characteristic linear with respect to the frequency is obtained between the relative frequencies of -10 GHz and 10 GHz.

FIG. 8 shows a second embodiment of the optical dispersion equalizer according to the present invention. In the present embodiment, the first optical waveguide 16 (16
a to 16j), a second optical waveguide 17, an optical waveguide group 18 composed of I (eight in this embodiment) optical waveguides 18a to 18h, and eight optical waveguides 18a to 18h of the optical waveguide group 18.
Are coupled to different portions of the first optical waveguide 16 on the side of the one end portions 18a1 to 18h1, respectively, and the eight optical waveguides 18a to 18h of the optical waveguide group 18 are provided. Other end portions 18a2 to 18h
The multiplexing device 19 collectively outputs the signals input from the second to the second optical waveguide 17, the directional couplers 3 a to 3 h of the eight optical waveguides 18 a to 18 h of the optical waveguide group 18 and the multiplexing device 19 of the A dispersion compensator 5 for compensating dispersion of an optical fiber is provided in an optical waveguide 16a which is an input portion of an optical waveguide circuit having phase controllers 4a to 4h provided therebetween.
As the number I of the optical waveguides constituting the optical waveguide group increases, the compensation effect increases, but the device configuration becomes complicated. On the other hand, if the number I is small, the compensation effect is not sufficient. In the present embodiment, eight optical waveguides are exemplified as the optical waveguide group, but the preferred number of optical waveguides is four to sixteen. Although the example in which the dispersion compensator 5 is provided on the input side of the optical waveguide 16 has been described, the dispersion compensator may be provided on at least one of the input side and the output side optical waveguide 17 of the optical waveguide 16.

As described above, the variable coupling ratio directional couplers 3a to 3h can use the configuration shown in FIGS.
The phase controllers 4a to 4h and the dispersion compensator 5 are as described above.

9 and 10 show examples of the structure of the merger 19. FIG.

The merger shown in FIG. 9 is configured using a directional coupler, and shows an example in which eight optical waveguides are combined into one optical waveguide. Adjacent optical waveguides 20a and 2
0b, 20c and 20d, 20e and 20f, 20g and 20
h is the directional coupler 21a, 21b, 21c, 2
One optical waveguides 20j and 20k and 20n and 20o on the output side of each directional coupler are coupled by directional couplers 21e and 21f, respectively. One of the optical waveguides 20r and 20r on the output side of the directional couplers 21e and 21f
0s is coupled by the directional coupler 21g. In this way, the light propagating through the eight optical waveguides 20a to 20h is combined by the three-stage directional couplers 21a to 21g and output from the optical waveguides 20u and 20v. The optical waveguides 20a to 20h are respectively replaced with the optical waveguides 18a to 18 in FIG.
h connected to the other end portions 18a2 to 18h2 of the optical waveguide 20.
u or 20v may be connected to the optical waveguide 17 of FIG.

The merger shown in FIG. 10 is configured using a Y-branch waveguide. This figure shows an example of a merger that combines eight optical waveguides into one optical waveguide. Optical waveguides 22a to 22o, three-stage Y branch waveguides 23a to 2
3g, and the optical waveguides 22a to 22h
Is used as an input part, and 22o is used as an output part.

In FIG. 8, the coupling ratio variable directional coupler 3
a to 3h are set to appropriate values and the phase controller 4
By appropriately performing the phase adjustment of the optical waveguide using a to 4h, as a characteristic between the optical waveguide 16b (the output side of the dispersion compensator 5) and the optical waveguide 17, the group delay time can be converted into a function of an arbitrary frequency. Approximable elements can be constructed (eg, “Coherent” by K. Sasayayama et al.
optical transversal filter
er using silica-basedwave
guides for high-speed sig
nal processing ”, Journal o
f Lightwave Technology, vo
l. 9, No. 10, pp. 1225-1230, Oc
Tober 1991), it is possible to obtain a relative delay time characteristic that is approximately approximated by a quadratic expression that is convex upward with respect to the frequency. Therefore, in FIG. 8, a group represented by a quadratic expression that is convex downward with respect to the frequency of the optical fiber is provided by providing the dispersion compensator 5 that compensates for the dispersion of the optical fiber in which the relative delay time changes linearly with the change in frequency. The delay time characteristic is compensated by the characteristic that can be realized between the optical waveguide 16b and the optical waveguide 17 of the optical circuit, and the group delay time characteristic that changes linearly with frequency is compensated by the dispersion compensator 5 sharing. By doing so, it becomes possible to compensate for the effect of the dispersion of the optical fiber, including the effect of higher-order dispersion, as in the case of the first embodiment.

FIG. 11 shows an embodiment in which the light dispersion equalizer of the present invention is combined with a light source. In this embodiment, the optical waveguide 24a
24e, a light source 25, and a light dispersion equalizer 26 shown in FIG. The optical waveguides 24b, 24c, 24 of FIG.
d and 24e correspond to 1a, 2a, 1j and 2j in FIG. 1, respectively.

As described above, the optical dispersion equalizer 26 can compensate for the dispersion of the optical fiber, including the effect of higher-order dispersion. Since the optical dispersion equalizer 26 is a linear element, its installation position may be anywhere between the transmission light source and the reception light receiver of the all-optical linear transmission line. Therefore, by installing the light source 25 in front of the optical dispersion equalizer 26, it becomes possible to configure a light source capable of correcting in advance the influence of dispersion in the optical transmission line before the optical transmission line.

As the light source, any of a semiconductor laser, a solid laser, a gas laser and the like can be used, but the most common method is to install the semiconductor laser in a hybrid integrated manner on the optical waveguide.

FIG. 12 shows another embodiment in which the light dispersion equalizer of the present invention and a light source are combined. In this embodiment, the optical waveguide 2
7a to 27c, light source 28, light dispersion equalizer 2 shown in FIG.
9 is comprised. The optical waveguides 27a and 27c in FIG. 12 correspond to 16a and 17 in FIG. 8, respectively.

As described above, the optical dispersion equalizer 29 can compensate for the dispersion of the optical fiber, including the effect of higher-order dispersion. Since the optical dispersion equalizer 29 is a linear element, its installation position may be anywhere between the transmission light source and the reception light receiver of the all-optical linear transmission line. Therefore, by providing the light source 28 in front of the optical dispersion equalizer 29, it becomes possible to configure a light source capable of correcting in advance the influence of dispersion in the optical transmission line before the optical transmission line.

The optical waveguide constituting the optical dispersion equalizer according to the embodiment of the present invention was manufactured using a silica glass optical waveguide. First, SiO ₂ was deposited on a Si substrate by flame deposition.
After depositing a lower cladding layer and then depositing a core layer of SiO ₂ glass doped with GeO ₂ as a dopant,
Transparent vitrification was performed in an electric furnace. Next, FIG. 1, FIG. 8, FIG.
The core layer was etched using a pattern as shown in FIG. 12 to form a core portion. Finally, an SiO ₂ upper cladding layer was deposited again to form a transparent glass, and a thin film heater as a phase controller and electric wiring were deposited on a predetermined optical waveguide.

It is apparent that the optical waveguide portion constituting the optical dispersion equalizer of the present invention is not limited to a glass optical waveguide, but can be realized by using a ferroelectric optical waveguide, a semiconductor optical waveguide, a polymer optical waveguide, or the like. . It is also apparent that this can be realized by using a hybrid configuration in which several types of waveguides are combined. Further, by combining the light dispersion equalizer of the present invention with a light source, it is possible to provide a light source in which the influence of the dispersion of the optical transmission line is corrected in advance.

[0047]

As described above in detail with reference to the embodiments, the optical dispersion equalizer according to the present invention is capable of transmitting a signal which is distorted by propagating through an optical fiber having dispersion as an optical signal as it is. Waveform shaping can be performed by compensating for the effect of the secondary dispersion.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of an optical dispersion equalizer according to the present invention.

FIG. 2 is a diagram illustrating a configuration example of a variable coupling rate directional coupler.

FIG. 3 is a diagram illustrating a configuration example of a variable coupling ratio directional coupler.

FIG. 4 is a diagram showing a calculation example of a relative delay time characteristic of an optical fiber.

FIG. 5 is a diagram showing an example of calculating characteristics of an optical dispersion equalizer.

FIG. 6 is a diagram illustrating a configuration example of a lattice configuration distributed equalizer.

FIG. 7 is a diagram illustrating a calculation example of a relative delay time characteristic of the lattice configuration dispersion equalizer.

FIG. 8 is a configuration diagram of a second embodiment of the optical dispersion equalizer according to the present invention.

FIG. 9 is a diagram illustrating a configuration example of a merger.

FIG. 10 is a diagram illustrating a configuration example of a merger.

FIG. 11 is a first configuration diagram of an embodiment in which the light dispersion equalizer of the present invention is combined with a light source.

FIG. 12 is a second configuration diagram of an embodiment in which the light dispersion equalizer of the present invention is combined with a light source.

FIG. 13 is a diagram showing a structure of a conventional dispersion equalizer using a microwave strip line.

FIG. 14 is a diagram showing propagation delay characteristics of a microwave strip line.

[Explanation of symbols]

 1, 1a to 1j Optical waveguide 2, 2a to 2j Optical waveguide 3a to 3i Coupling rate variable directional coupler 4a to 4h Phase controller 5 Dispersion compensator 6,7 Optical waveguide 8,8a to 8e Optical waveguide 9,9a to 9e Optical waveguides 10a to 10d Proximity parts 11a to 11c Phase controllers 12, 12a to 12g Optical waveguides 13, 13a to 13g Optical waveguides 14a to 14f Directional couplers 15a to 15e Phase controllers 16, 16a to 16j Optical waveguides 17 Optical waveguides Waveguide 18 Optical waveguide group 18a-18h Optical waveguide 19 Combiner 20a-20v Optical waveguide 21a-21g Directional coupler 22a-22o Optical waveguide 23a-23g Y branch waveguide 24, 24a-24c Optical waveguide 25 Light source 26 Optical dispersion, etc. Equalizer 27, 27a to 27c Optical waveguide 28 Light source 29 Optical dispersion equalizer 31 Dielectric 32a, 32 Metal conductor

Continuation of front page (56) References JP-A-9-23187 (JP, A) JP-A-7-281215 (JP, A) JP-A-6-337383 (JP, A) JP-A-6-331842 (JP) JP-A-5-303019 (JP, A) Koichi Takiguchi et. al. , 1995 IEICE Electronics Society Conference Lecture Paper 1, August 15, 1995, p. 230 Koichi Takiguchi et. al. , 1994 IEICE Autumn Conference, Society 1, Advanced Conference, Electronics 1, September 5, 1994, p. 259 Electronics Letters, August 18, 1994, Vol. 30 No. 17, pp. 1404-1406 Electronics Letters, January 18, 1996, Vol. 32 No. 2, pp. 113-114 Electronics Letters, April 11, 1996, Vol. 32 No. 8, pp. 755-757 (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/00-1/035 G02F 1/29-2/02 G02B 6/12-6/14 H04B 10/02-10 / 18 H04J 14/00-14/02

Claims (2)

(57) [Claims] 1. A semiconductor device comprising: a first optical waveguide, a second optical waveguide, and N + 1 (N is an integer) coupling rate variable directional couplers for coupling the first and second optical waveguides at different positions. The optical path lengths of the first and second optical waveguides of respective portions sandwiched between two adjacent ones of the (N + 1) directional couplers are different from each other, and adjacent portions of the (N + 1) directional couplers are adjacent to each other. An optical waveguide circuit in which a phase controller is provided in at least one of the first and second optical waveguides of each portion sandwiched between the two, and at least one of an input / output unit of the optical waveguide circuit. Provided
Also, it has a linear relative delay time characteristic to the optical frequency
The optical waveguide circuit is convex upward with respect to the frequency of the optical fiber.
Optical waveguide with relative delay time characteristics approximated by a simple quadratic equation
An optical dispersion equalizer, which is a circuit . 2. An optical waveguide group comprising a first optical waveguide, a second optical waveguide, and I (I is an integer of 2 or more) optical waveguides,
I variable coupling ratio directional couplers coupling the I optical waveguides of the optical waveguide group to different portions of the first optical waveguide on one end side, and the I optical waveguides of the optical waveguide group. A multiplexing device that collectively outputs signals input from the other ends of the waveguides to the second optical waveguide, and a directional coupler and a multiplexing device for each of the I optical waveguides in the optical waveguide group. Optical waveguide circuit having a phase controller provided therebetween
When, on at least one of the input and output portions of the optical waveguide circuit
Also, it has a linear relative delay time characteristic to the optical frequency
The optical waveguide circuit is convex upward with respect to the frequency of the optical fiber.
Optical waveguide with relative delay time characteristics approximated by a simple quadratic equation
An optical dispersion equalizer, which is a circuit .