JP4875297B2 - Variable dispersion compensator, variable dispersion compensation device - Google Patents

Description

The present invention relates to a variable dispersion compensator used in the field of optical communication and a variable dispersion compensation device using the variable dispersion compensator.

In general, an optical transmission line that performs optical communication (optical transmission) has positive chromatic dispersion in the optical transmission band. In order to suppress distortion of signal light due to this chromatic dispersion, conventionally, a dispersion compensating optical fiber having negative chromatic dispersion in the optical transmission band is connected to the optical transmission line to compensate for the chromatic dispersion of the optical transmission line. . This dispersion compensation technique is being put into practical use in optical transmission where the transmission speed of signal light is 10 Gbit / s or less.

However, the above-described dispersion compensation technique is difficult to apply when the transmission speed of the signal light is further increased. For example, when the transmission speed of signal light is 40 Gbit / s or more, a more accurate dispersion compensation technique is required than the above-described dispersion compensation technique.

Further, the dispersion compensating optical fiber described above is configured to control the amount of dispersion compensation by the length of the optical fiber. For this reason, dispersion compensation is difficult when the dispersion compensation amount is several ps / nm to several tens ps / nm or less, and dispersion compensation corresponding to the above-described high-speed transmission of 40 Gbit / s or more is difficult. In addition, in order to perform dispersion compensation of an optical transmission line using a dispersion compensating optical fiber, it is necessary to form a dispersion compensating optical fiber having a length corresponding to each optical transmission line so as to correspond to each optical transmission line. However, it is not preferable in terms of cost and size.

Therefore, in order to cope with the situation as described above, a variable dispersion compensator capable of changing the dispersion value with a configuration different from a conventional configuration using a dispersion compensating optical fiber has been studied. As this variable dispersion compensator, for example, an arrayed waveguide diffraction grating type (hereinafter referred to as AWG type) variable dispersion compensator has been proposed (Patent Document 1).

This AWG type tunable dispersion compensator is configured by connecting a dispersion compensating optical fiber 40 and a tunable dispersion compensator 41 as shown in FIG. The tunable dispersion compensator 41 includes an arrayed waveguide diffraction grating 11 including an arrayed waveguide 4 composed of a plurality of channel waveguides 4 a arranged in parallel with different lengths, and an arrayed waveguide of the arrayed waveguide diffraction grating 11. 4 is formed with a phase distribution providing unit 7 for providing a set phase distribution for generating chromatic dispersion. In the set phase distribution, the number of channel waveguides of the arrayed waveguide 4 is M (M is a positive integer), and the channel waveguide number given in the order of arrangement of the channel waveguides 4a is k (k = 0 to M−1). In this case, the distribution is an even function distribution that is substantially line symmetric with respect to the center (M−1) / 2 of the channel waveguide number k.

As shown in FIG. 13, the set phase distribution is obtained by forming a thin film heater having a length corresponding to the phase distribution on each array waveguide and changing the refractive index of the array waveguide below the heater by the thermo-optic effect. Realized. Here, the number of channel waveguides 4a of the arrayed waveguide 4 is M (M is a positive integer), and the number of the channel waveguides 4a assigned in the order of arrangement of the channel waveguides 4a is k (k = 0 to M−1). ), The transfer function of the circuit 12 in consideration of the phase distribution P (k) formed in the arrayed waveguide 4 is given by (Equation 1).

Here, λ is a wavelength, H (λ) is a transfer function of light of wavelength λ, Ak is an optical electric field amplitude of the channel waveguide 4, n _eff is an equivalent refractive index of the channel waveguide 4a, and ΔL is an adjacent channel waveguide. The optical path length difference of 4a is j = √ (−1).

This H (λ) is a transfer function of the tunable dispersion compensator 41. The phase θ (λ) of H (λ) is expressed by (Equation 2).

By differentiating θ (λ) by wavelength, the group delay τ is obtained as shown in (Equation 3).

C is the speed of light.

A variable dispersion compensator is designed using the equations (Equation 1) to (Equation 3) described above and using the parameters shown in Table 1, for example.

By changing A in (Expression 1) in the range of + π (rad) to −π (rad), variable dispersion characteristics as shown in FIG. 14 can be obtained. The transmission loss spectrum at this time has a Gaussian waveform as shown in FIG. In the above design, the chromatic dispersion amount that can be compensated is −220 to +220 ps / nm, and the wavelength band that can be compensated is about 0.2 nm.

JP 2003-279910 A

In order to change the dispersion compensation amount and the dispersion compensation band design value of the variable dispersion compensator described above, it is possible to change the linear dispersion shown in Table 1. FIG. 16 is a graph showing the relationship between the linear dispersion, the dispersion compensation amount, and the dispersion compensation band. As is apparent from FIG. 16, the dispersion compensation amount increases in proportion to the increase in linear dispersion, but the dispersion compensation band has a trade-off relationship that decreases as the linear dispersion increases. Therefore, for example, there is a problem that the dispersion compensation amount necessary for application to a high-speed transmission system such as 40 Gbit / s cannot be made compatible with the dispersion compensation band.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to increase the dispersion compensation amount while maintaining the dispersion compensation band of signal light, and to reduce the transmission loss spectrum with low loss. An object of the present invention is to provide a tunable dispersion compensator that is less constricted, can suppress the occurrence of waveform distortion, and can prevent deterioration of transmission characteristics.

In order to achieve the above object, the present invention has the following configuration as means for solving the problems. That is, the tunable dispersion compensator of the first invention includes a substrate and a tunable dispersion compensation circuit formed on the substrate, and the tunable dispersion compensation circuit includes at least one optical input waveguide and the light. An array comprising a first slab waveguide connected to the output side of the input waveguide and a plurality of channel waveguides connected in parallel to the output side of the first slab waveguide and having different lengths from each other. A waveguide; a second slab waveguide connected to the output side of the array waveguide; at least one optical output waveguide connected to the output side of the second slab waveguide; And a phase distribution applying unit that gives a set phase distribution to the waveguide, and the variable dispersion compensation circuit is configured by connecting two or more cascades.

According to a second aspect of the present invention, there is provided a variable dispersion compensator comprising a substrate and a variable dispersion compensation circuit formed on the substrate, wherein the variable dispersion compensation circuit includes first and second optical inputs. A waveguide, a first slab waveguide connected to the output side of the first and second optical input waveguides, and a length connected to the output side of the first slab waveguide and having different set amounts from each other An arrayed waveguide composed of a plurality of side-by-side channel waveguides, a second slab waveguide connected to the output side of the arrayed waveguide, and a second connected to the output side of the second slab waveguide An optical circuit having a first optical output waveguide and a second optical output waveguide; and a phase distribution providing unit for providing a set phase distribution to the arrayed waveguide of the optical circuit, wherein the first optical input waveguide includes the first optical input waveguide, outside of the array waveguide on the input side of the focal position of the first slab waveguide Is connected to the input side of said first slab waveguide in the first position of direction, the first optical output waveguides, said array guide relative to the focal position of the output side of the second slab waveguide in a second position outside the direction of the waveguide is connected to the output side of the second slab waveguide, the second optical input waveguide, said array guide relative to the focal position of the first slab waveguide The second optical output waveguide is connected to the input side of the first slab waveguide at a third position that is inward of the waveguide and symmetrical to the first position, and the second optical output waveguide is the second slab waveguide The first optical output waveguide is connected to the output side of the second slab waveguide at a fourth position that is inward of the arrayed waveguide with respect to the focal position of the second waveguide and symmetrical to the second position. And the first optical input waveguide or the second optical output waveguide and the second optical input waveguide are connected to each other It is made of is.

  Furthermore, in the third aspect of the present invention, the set phase distribution is such that the number of channel waveguides of the arrayed waveguide is M (M is a positive integer), and the channel waveguide number given in the order of arrangement of the channel waveguides is k ( When k = 0 to M−1), the distribution is an even function distribution that is substantially line symmetric with respect to the center (M−1) / 2 of the channel waveguide number k.

Furthermore, the fourth aspect of the present invention is a quadratic function distribution P (k) represented by the formula 1 in which the set phase distribution includes the coefficient A.

Furthermore, the fifth aspect of the present invention is a Sin function distribution P (k) represented by the formula 2 in which the set phase distribution includes the coefficient A.

Furthermore, the sixth aspect of the present invention is an Exp function distribution P (k) represented by the formula 3 in which the set phase distribution includes the coefficient A.

Furthermore, the seventh aspect of the present invention is a linear function distribution P (k) represented by the equation (4) in which the set phase distribution includes the coefficient A.

Further, according to an eighth aspect of the present invention, the phase distribution providing unit can change the set phase distribution.

Further, according to a ninth aspect of the present invention, the phase distribution providing unit has a heating unit that heats at least the setting region of the arrayed waveguide forming region.

  Furthermore, in the tenth aspect of the present invention, a flattening filter for flattening the wavelength characteristic of the transmission loss of the tunable dispersion compensation circuit is connected to at least one of the optical input waveguide and the optical output waveguide. Is.

  In the eleventh aspect of the present invention, the flattening filter has substantially zero chromatic dispersion in the transmission band of the tunable dispersion compensation circuit.

  Furthermore, a twelfth aspect of the present invention includes any one of the tunable dispersion compensators described above and a dispersion compensating optical fiber connected to the tunable dispersion compensator.

According to the tunable dispersion compensator of the present invention, a plurality of tunable dispersion compensators are connected in cascade, so that signal light is transmitted through the tunable dispersion compensator multiple times without changing the circuit parameters of the tunable dispersion compensator. It becomes possible. As a result, the dispersion compensation amount can be increased while maintaining the dispersion compensation band of the signal light.

According to the tunable dispersion compensator of the present invention, the tunable dispersion compensation circuit includes at least one light input waveguide among the light input waveguides and at least one light output waveguide of the light output waveguide. Since it is configured to be optically connected, it is possible to accurately match the transmission center wavelength when transmitting the same variable dispersion compensation circuit multiple times. A compensator can be provided.

Furthermore, according to the tunable dispersion compensator of the present invention, since the flattening filter is connected to the tunable dispersion compensation circuit, the loss spectrum of the transmission band of the signal light can be flattened and waveform distortion hardly occurs. Optical transmission is possible.

Furthermore, according to the tunable dispersion compensator of the present invention, since the chromatic dispersion of the connected flattening filter is almost zero, it is possible to suppress the influence due to the chromatic dispersion of the flattening filter, and light without deterioration in transmission characteristics. Transmission is possible.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the present embodiment, the same reference numerals are assigned to the same names as those in the conventional example, and the duplicate description is omitted or simplified.

FIG. 1 schematically shows a main part configuration diagram of a first embodiment of a tunable dispersion compensator according to the present invention. A tunable dispersion compensator 100 according to this embodiment shown in FIG. 1 has a structure in which two tunable dispersion compensation circuits 102 having the same configuration are connected in cascade on a substrate 101. The tunable dispersion compensation circuit 102 is made of silica-based PLC, and includes one optical input waveguide 104, a first slab waveguide 106 connected to the output side of the optical input waveguide 104, and a first An array waveguide 110 that is connected to the output side of the slab waveguide 106 and includes a plurality of juxtaposed channel waveguides 108 having different lengths from each other, and a second slab connected to the output side of the array waveguide 110 Formed between the waveguide 112, one optical output waveguide 114 connected to the output side of the second slab waveguide 112, and the first slab waveguide 106 and the second slab waveguide 112. A phase distribution providing unit 116 that is provided in a part of the arrayed waveguide 110 and provides a set phase distribution for each channel waveguide 108 is configured.

The dispersion characteristic of the tunable dispersion compensator 100 shown in FIG. 1 is the sum of the dispersion characteristics of the two tunable dispersion compensation circuits 102. The measurement results of the dispersion characteristics of the tunable dispersion compensator 100 are shown in FIG. 2, and the transmission loss spectrum is shown in FIG. As is clear from FIG. 2, the tunable dispersion compensator 100 of the present embodiment has a dispersion compensation amount that is substantially the same as the dispersion compensation band compared with the performance of the conventional tunable dispersion compensator shown in FIG. You can see that it has been enlarged. In the tunable dispersion compensator 100 shown in FIG. 1, the dispersion compensation amount is variable in the range of −440 to +440 ps / nm, and the dispersion compensation band is about 0.18 nm.

Note that the tunable dispersion compensator 100 passes through the tunable dispersion compensation circuit 102 having the wavelength filter characteristics twice, and the transmission center wavelengths of the two tunable dispersion compensation circuits 102 are different by about 0.05 nm. There is an increase in losses. Further, the dispersion compensation band is slightly narrower than twice that of a single AWG type variable dispersion compensator (it is considered that the transmission center wavelengths of the two variable dispersion compensation circuits 102 are different). For this reason, transmission characteristics may be deteriorated due to these effects. However, carrier-suppressed return to zero (CS-RZ) modulation, optical single sideband (SSB) modulation, and so on. This can be solved by performing optical transmission using a modulation method capable of suppressing the occupied wavelength band, such as modulation and optical sideband modulation (VSB) modulation.

In the present embodiment shown in FIG. 1, two variable dispersion compensation circuits 102 are integrated on one chip (one substrate 101), but the present invention is not limited to this. For example, although not shown, two variable dispersion compensation circuits 102 formed on separate chips (substrate 101) may be optically connected directly or using an optical fiber or the like. With such a configuration, the temperature of each tunable dispersion compensation circuit 102 can be adjusted separately, and the deviation of the transmission center wavelength between the two circuits can be further reduced.

Next, a second embodiment of the present invention will be described.
FIG. 4A schematically shows a main part configuration diagram showing a second embodiment of the variable dispersion compensator of the present invention. 4B is an enlarged view of a main part showing a connection portion between the optical input waveguide 104 and the first slab waveguide 106 on the input side in FIG. 4A, and FIG. FIG. 5 is an enlarged view of a main part showing a connection portion between the optical output waveguide 114 and the output-side second slab waveguide 112 in FIG.

In addition to the conventional configuration shown in FIG. 12, the tunable dispersion compensator 120 of the present embodiment includes another optical waveguide in which the first slab waveguide 106 and the second slab waveguide 112 are different from the arrayed waveguide 110. It is different in that it is connected at 122.

That is, in the present embodiment, as shown in FIG. 4B, the input side end face of the first slab waveguide 106 on the input side is arrayed with respect to the focal position 124 of the first slab waveguide 106. The optical input waveguide 104 is connected to the outside direction of the waveguide 110 (left side as viewed on the paper surface), and the input end 122a of the optical waveguide 122 is connected to the inside direction of the arrayed waveguide 110 (right side as viewed on the paper surface). ing. Further, as shown in FIG. 4C, the output side end surface of the second slab waveguide 112 on the output side has an inner direction of the arrayed waveguide 110 with respect to the focal position 126 of the second slab waveguide. The output end 122b of the optical waveguide 122 is connected to the left side (on the paper surface), and the optical output waveguide 114 is connected to the outer side of the arrayed waveguide 110 (right side on the paper surface).

The optical input waveguide 104 and the input end 122a of the optical waveguide 122 are connected to a symmetrical position with respect to the focal position 124 of the first slab waveguide 106 , and the optical output waveguide 114 and the output end 122b of the optical waveguide 122 are The second slab waveguide 112 is connected to a symmetrical position with respect to the focal position 126. In the tunable dispersion compensator 120 shown in FIG. 4A, the optical input waveguide 104 is an optical waveguide for input from the outside, and the optical output waveguide 114 is an optical waveguide for output to the outside.

As described above, two sets of optical input / output waveguides (104 and 122, 114 and 122) formed at symmetrical positions with respect to the focal positions 124 and 126 of the first and second slab waveguides 106 and 112, respectively. The optical characteristics when signal light is input from the optical input waveguide 104 to the tunable dispersion compensation circuit 121 and output from the output end 122b of the optical waveguide 122, and input from the input end 122a of the optical waveguide 122 are input. Thus, the optical characteristics when output from the light output waveguide 114 are substantially the same. The optical characteristics are transmission loss spectrum, dispersion, and the like.

By adopting such a configuration, the same effect as passing the same variable dispersion compensation circuit 121 twice can be obtained. Therefore, as in the first embodiment, the dispersion compensation band is maintained and the dispersion compensation is maintained. The amount can be doubled compared to a single pass. Furthermore, since the same variable dispersion compensation circuit 121 is used, the driving power may be equivalent to one circuit, and the transmission center wavelength automatically matches by designing as described above, so the transmission center wavelength is matched. You can save time and effort. Further, as apparent from the comparison between FIG. 1 and FIG. 4A, the chip size can be reduced to about half compared with the configuration of the first embodiment.

FIG. 5 is a measurement result of dispersion characteristics by the variable dispersion compensator 120 shown in FIG. 4A, and FIG. 6 is a transmission loss spectrum. As can be seen from FIG. 5, with respect to the dispersion characteristics, the dispersion compensation amount can be expanded to about twice while maintaining the same dispersion compensation band as that of the conventional example. More specifically, a dispersion compensation amount of −440 to +440 ps / nm was obtained, and a dispersion compensation band of about 0.20 nm was obtained. Further, as shown in FIG. 6, it can be seen that the transmission loss spectrum is slightly wider than Example 1 and can be maintained at a low loss. This is considered to be because narrowing and an increase in loss due to the difference in center wavelength between the two variable dispersion compensation circuits were avoided.

As described above, in addition to the first embodiment, the second embodiment further provides effects such as reduction of driving power, expansion of transmission loss spectrum, suppression of loss, and miniaturization.

Next, a third embodiment of the present invention will be described with reference to FIG.
This embodiment is a tunable dispersion compensator 130 obtained by further improving the second embodiment, and has a configuration in which a flattening filter 132 is connected to a tunable dispersion compensation circuit 121. Since the tunable dispersion compensation circuit 121 exhibits Gaussian wavelength filter characteristics, there is a possibility that the transmission loss spectrum is narrowed by transmitting the signal light twice, for example. For this reason, in the vicinity of the transmission band of the tunable dispersion compensation circuit 121, the flattening filter 132 showing the spectrum shape opposite to the transmission loss spectrum shape of the tunable dispersion compensation circuit 121 is installed, thereby narrowing the transmission loss spectrum described above. Compensation is made to flatten the spectrum. Note that, as the flattening filter 132, in principle, a filter that does not generate chromatic dispersion is used so that the dispersion compensation operation of the tunable dispersion compensator 130 is not affected.

Next, the configuration of the tunable dispersion compensator 130 of the third embodiment will be specifically described with reference to FIG. The tunable dispersion compensator 130 is configured by further installing a flattening filter 132 composed of Mach-Zehnder interferometers 132a and 132b in the subsequent stage of the tunable dispersion compensation circuit 121 according to the second embodiment. The flattening filter 132 has a coupler coupling ratio of about 5 to 40%, and the interferometer arm phase difference is set to a value that is about the free spectral region of the variable dispersion compensation circuit 121 to several tens of times the free spectral region. In the vicinity of the transmission band of the tunable dispersion compensation circuit 121, 2 × 2 Mach-Zehnder interferometers 132a and 132b having a spectrum shape opposite to the transmission loss spectrum shape of the tunable dispersion compensation circuit 121 are cascade-connected. ing. The first-stage 2 × 2 Mach-Zehnder interferometer 132a uses an input / output waveguide 134 on the long arm side, and the second-stage 2 × 2 Mach-Zehnder interferometer 132b has an input / output waveguide 136 on the short arm side. Is used.

Next, the 2 × 2 Mach-Zehnder interferometers 132a and 132b constituting the flattening filter 132 will be described with reference to FIG. FIG. 8 is a configuration diagram of one stage of the 2 × 2 Mach-Zehnder interferometers 132a and 132b constituting the flattening filter 132. The 2 × 2 Mach-Zehnder interferometers 132a and 132b shown in FIG. 8 are input from the port a in FIG. 8, where φ is the phase difference between the two waveguide arms and θ is the phase of the two directional couplers. The transfer function Ta-c of the path a-c that is output from the port c and the transfer function Tb-d of the path b-d that is input from the port b and output from the port d are expressed by Equations 4 and 5, respectively. .

Further, the coupling ratios ηa-c and ηb-d of each path and the phases Ψa-c and Ψb-d after passing are expressed by (Equation 6) to (Equation 9), respectively, using the real part and the imaginary part of each equation. It is represented by

As is clear from (Equation 6) to (Equation 9), the path characteristic is the same in the path ac and the path bd, and the phase characteristic is in the relationship of positive / negative inversion. For this reason, by connecting the paths a-c and b-d of two Mach-Zehnder interferometers having the same configuration, it is possible to configure a wavelength filter that cancels phase characteristics and does not generate chromatic dispersion.

FIG. 9 shows, as an example of the flattening filter configured as described above, a transmission wavelength spectrum when the coupling ratio of the coupler constituting the flattening filter is about 17% and the interferometer arm phase difference is about 6000 μm. It is a graph which shows. As can be seen from FIG. 9, a spectrum shape almost opposite to that in FIG. 6 can be realized in the vicinity of the transmission band.

FIG. 10 shows the measurement result of the dispersion characteristic after passing through the flattening filter, and FIG. 11 shows the transmission loss spectrum. As shown in FIG. 10, the dispersion characteristic measurement result shows that the dispersion compensation amount can be expanded about twice while maintaining the same dispersion compensation band as in the conventional example. More specifically, a dispersion compensation amount of −430 to +435 ps / nm was obtained, and a dispersion compensation band of about 0.20 nm was obtained. Furthermore, as shown in FIG. 11, the transmission loss spectrum shows that although the loss at the transmission center wavelength is increased by about 7 dB, the transmission band is substantially flattened. Thereby, it is possible to perform optical transmission in which waveform distortion hardly occurs.

In the above embodiment, the design parameters shown in Table 1 were used and the quartz PLC was used. However, the effect of the present invention is not limited to these parameters and materials, and the required dispersion compensation amount. -It can be appropriately selected in view of characteristics such as a dispersion compensation band, reliability, cost, and the like. For example, by controlling (changing) the variable dispersion compensation circuit parameters such as linear dispersion and ΔL, the dispersion compensation amount and the dispersion compensation band can be adjusted as described above, so that various required characteristics can be satisfied. As an alternative to quartz-based PLC, polymer waveguides and semiconductor waveguides can be applied to all or part of the circuit. In this case, it has a larger thermo-optic constant than quartz-based glass, reducing power consumption and response speed. be able to. In addition, a waveguide having an electro-optic effect or a magneto-optic effect can be applied to all or a part of the circuit. In this case, the response speed can be further improved, and problems such as transmission wavelength fluctuation due to the heat of the heater can be improved. Can do.

Further, in order to increase the dispersion compensation amount, in the above-described embodiment, the signal light is passed through the variable dispersion compensation circuit twice. However, the number of times of passing is not limited. For example, you may let it pass 3 times, 4 times ... n times. That is, by passing the tunable dispersion compensation circuit n times, a dispersion compensation amount approximately n times the dispersion compensation amount when the tunable dispersion compensation circuit is passed once can be obtained. However, as the number of passes increases, the transmission loss spectrum becomes narrower and the loss increases as described above. Therefore, it is necessary to determine the number of passes in view of the necessary transmission band and the like.

Furthermore, in the above-described Embodiments 2 and 3, the first and second input / output waveguides are arranged symmetrically with respect to the focal position of the slab waveguide, but the arrangement structure is not limited to this. . Transmission center wavelength of light input from the first input waveguide and output from the first output waveguide, and transmission center wavelength of light input from the second input waveguide and output from the second output waveguide And the position may be determined appropriately in consideration of design parameters such as the amount of linear dispersion. However, in order to increase the identity of the optical characteristics at the first and second AWG passes, it is more preferable to adopt the configuration as in the second and third embodiments.

Further, in the third embodiment, a Mach-Zehnder interferometer type flattening filter is installed. However, the flattening filter is not limited to this, and the transmission loss spectrum of the variable dispersion compensation circuit such as a ring resonator or a lattice filter is used. It is only necessary to realize a reverse shape (reverse spectrum). Further, a flattening filter such as an etalon that is not a waveguide type may be optically connected. Furthermore, the flattening filter is installed at various positions, such as before and after the variable dispersion compensation circuit, after passing through the first variable dispersion compensation circuit, or before passing through the second variable dispersion compensation circuit. can do. Furthermore, the transmission loss spectrum expansion technique using such a flattening filter can also be applied to the configurations of the first and second embodiments.

It is a schematic block diagram of one Embodiment of this invention. It is a graph which shows the dispersion characteristic of one Embodiment of this invention shown in FIG. It is a graph which shows the transmission loss spectrum of one Embodiment of this invention shown in FIG. (A) is a schematic block diagram of one Embodiment of this invention, (b) And (c) is the principal part enlarged view of (a). It is a graph which shows the dispersion characteristic of one Embodiment of this invention shown in FIG. It is a graph which shows the transmission loss spectrum of one Embodiment of this invention shown in FIG. It is a schematic block diagram of one Embodiment of this invention. It is a principal part enlarged view of one Embodiment of this invention shown in FIG. It is a graph which shows the transmission wavelength spectrum of one Embodiment of this invention shown in FIG. It is a graph which shows the dispersion characteristic of one Embodiment of this invention shown in FIG. It is a graph which shows the transmission loss spectrum of one Embodiment of this invention shown in FIG. It is a schematic block diagram of the conventional variable dispersion compensator. It is a schematic explanatory drawing of the conventional variable dispersion compensator shown in FIG. It is a graph which shows the dispersion characteristic of the conventional variable dispersion compensator shown in FIG. It is a graph which shows the transmission loss spectrum of the conventional variable dispersion compensator shown in FIG. 13 is a graph showing the relationship between linear dispersion, dispersion compensation amount, and dispersion compensation band of the conventional variable dispersion compensator shown in FIG.

Explanation of symbols

100, 120, 130 Variable dispersion compensator 101 Substrate 102 Variable dispersion compensation circuit 104 Optical input waveguide 106 First slab waveguide 108 Channel waveguide 110 Array waveguide 112 Second slab waveguide 114 Optical output waveguide 116 Phase Distribution imparting section 121 Variable dispersion compensation circuit 122 Optical waveguide 122a Input end 122b Output end 124, 126 Focus position 132 Flattening filter 132a, 132b Mach-Zehnder interferometer 134, 136 Input / output waveguide

Claims (11)

In a tunable dispersion compensator comprising a substrate and a tunable dispersion compensation circuit formed on the substrate,
The variable dispersion compensation circuit includes:
First and second optical input waveguides;
A first slab waveguide connected to the output side of the first and second optical input waveguides;
An arrayed waveguide comprising a plurality of channel waveguides connected to the output side of the first slab waveguide and having different lengths from each other;
A second slab waveguide connected to the output side of the arrayed waveguide;
An optical circuit having first and second optical output waveguides connected to the output side of the second slab waveguide;
A phase distribution providing unit for providing a set phase distribution to the arrayed waveguide of the optical circuit,
The first optical input waveguide has an input side of the first slab waveguide at a first position outside the arrayed waveguide with respect to a focal position on the input side of the first slab waveguide. Connected,
The first optical output waveguide has an output side of the second slab waveguide at a second position outside the arrayed waveguide with respect to a focal position on the output side of the second slab waveguide. Connected,
The second optical input waveguide is the first slab at a third position which is inward of the arrayed waveguide with respect to the focal position of the first slab waveguide and is symmetric with respect to the first position. Connected to the input side of the waveguide,
The second optical output waveguide is in the fourth direction which is inward of the arrayed waveguide with respect to the focal position of the second slab waveguide and is symmetric with respect to the second position. Connected to the output side of the waveguide,
Variable dispersion compensation characterized in that the first optical output waveguide and the first optical input waveguide or the second optical output waveguide and the second optical input waveguide are connected. vessel.   In the set phase distribution, the number of channel waveguides of the arrayed waveguide is M (M is a positive integer), and the channel waveguide number given in the order of arrangement of the channel waveguides is k (k = 0 to M−1). 2. The variable dispersion compensator according to claim 1, wherein the distribution is an even function distribution which is substantially line symmetric with respect to the center (M−1) / 2 of the channel waveguide number k. 3. The variable dispersion compensator according to claim 2, wherein the set phase distribution is a quadratic function distribution P (k) represented by Formula 1 including a coefficient A.

3. The variable dispersion compensator according to claim 2, wherein the set phase distribution is a Sin function distribution P (k) represented by Formula 2 including a coefficient A.

The variable dispersion compensator according to claim 2, wherein the set phase distribution is an Exp function distribution P (k) represented by Formula 3 including a coefficient A.

3. The variable dispersion compensator according to claim 2, wherein the set phase distribution is a linear function distribution P (k) represented by Formula 4 including a coefficient A.

  The variable dispersion compensator according to any one of claims 1 to 6, wherein the phase distribution providing unit is configured to be able to vary the set phase distribution.   The variable dispersion compensator according to any one of claims 1 to 7, wherein the phase distribution providing unit includes a heating unit that heats at least a setting region of the arrayed waveguide formation region.   The flattening filter for flattening the wavelength characteristic of the transmission loss of the tunable dispersion compensation circuit is connected to at least one of the optical input waveguide and the optical output waveguide. The variable dispersion compensator according to claim 8.   The variable dispersion compensator according to claim 9, wherein the flattening filter has substantially zero chromatic dispersion in a transmission band of the variable dispersion compensation circuit.   A variable dispersion compensation device comprising: the variable dispersion compensator according to claim 1; and a dispersion compensation optical fiber connected to the variable dispersion compensator.

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