JP2002131658A - Distributed equalizer - Google Patents

Abstract

(57) [Problem] To provide a variable dispersion equalizer capable of reducing power consumption and improving controllability and reproducibility of dispersion. A substrate having an optical waveguide and a waveguide grating formed in a part of the optical waveguide is supported in a case by two substrate supporting portions, and the waveguide grating of the substrate is formed in the case. Substrate pressing means for bending the bent portion, one of the substrate supporting portions is provided outside one end of the waveguide grating, and the other is provided outside the other end of the waveguide grating. Was provided so as to press the substrate between one end of the waveguide grating or one end of the waveguide grating and one substrate support.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dispersion equalizer for compensating chromatic dispersion of light transmitted through an optical fiber for transmission, which has been increasingly required in recent years with the advancement of a wavelength division multiplexing optical communication system. It is.

[0002]

2. Description of the Related Art In an ultra-high-speed wavelength division multiplexing optical communication system, an optical multiplexer / demultiplexer or a band pass filter for multiplexing / demultiplexing a wavelength multiplexed signal, or a dispersion compensator (dispersion equalizer) for compensating dispersion of an optical fiber serving as a transmission medium is used. It is a key device, and improvement of those characteristics is an important issue. The waveguide grating that is important in configuring these devices has a function of reflecting light of a specific wavelength, and the Bragg wavelength λB is expressed by the following (1)
Defined by an expression. Here, neff is the effective refractive index of the waveguide chirp grating, and Λ is the period of the waveguide chirp grating. λB = 2neffΛ (1)

[0003] In an optical communication, an optical fiber serving as a transmission medium of an optical signal has a dispersion that the speed of propagating through a transmission line differs depending on the wavelength of light, and thus a difference in group delay occurs due to the difference in wavelength. For example, since an optical pulse signal has a spread in wavelength components, if an optical pulse signal having the waveform shown in FIG. 23A originally propagates for several tens of kilometers, the signal spreads as shown in FIG. 23B. Will happen. Therefore, in ultra-high-speed optical communication, a technique for compensating for dispersion of an optical fiber is required.

That is, the relationship between the wavelength and the group delay in an optical fiber is as shown in FIG. 24A, and the dispersion represented by the derivative is as shown in FIG. Therefore, to compensate for this, a device having group delay and dispersion characteristics as shown in FIG. 25 is required. A dispersion equalizer that compensates for this dispersion, for example, as shown in FIG.
It can be realized by the circulator 14 and the waveguide chirp grating 20. The waveguide chirp grating 20 is configured such that its grating period becomes longer as it goes away from the input port side, and the input light is reflected by a portion having a grating period that satisfies the expression (1) depending on its wavelength. That is, light having a longer wavelength is reflected at a position farther from the circulator, and as a result, the group delay increases. Therefore, in the distributed equalizer of FIG. 26, the group delay has a slope as shown in FIG. That is, the dispersion is as shown in FIG.
As shown in FIG. 24B, the dispersion value is opposite to the sign of the dispersion value of the optical fiber shown in FIG. 24, so that dispersion compensation can be performed.

Since the dispersion value required for the dispersion equalizer varies depending on the use environment such as the length of the optical fiber used as the transmission line and the temperature, the dispersion equalizer having a number of different dispersion values is inserted. Was usually done, and the choice was very time-consuming. FIG. 27 is a diagram showing a configuration of a distributed equalizer disclosed in Japanese Patent Application Laid-Open No. H10-224297 in order to solve such a problem. The distributed equalizer of this conventional example (first conventional example) , A variable dispersion equalizer using a fiber chirp grating.
Since the variable dispersion equalizer can finely adjust the dispersion value, the problem in the optimization of the dispersion value is solved.

In the variable dispersion equalizer shown in FIG. 27, temperature applying means 19 controlled by a temperature controller 18 is used.
In this case, heat is applied to the fiber chirp grating 20. At this time, the amount of heat generated by each of the temperature applying means 19 is set to a different amount, thereby generating a heat gradient in the fiber chirp grating 20. In this case, since the effective refractive index neff of the fiber chirped grating 20 is a function of the temperature, the thermal gradient generated by the temperature applying means 19 also affects the effective refractive index neff in the longitudinal distribution (gradient) of the waveguide. Bring). Accordingly, the Bragg wavelength can be changed in the longitudinal direction of the waveguide chirp grating, and the dispersion can be changed by an amount corresponding to the thermal gradient. still,
In the first conventional example, the center wavelength also changes in response to a change in temperature. The change in the center wavelength is adjusted by the tension controlled by the tension controller.

FIG. 28 is a graph showing the characteristics of Japanese Patent Application Laid-Open No. 11-160543.
Is a variable dispersion equalizer using a fiber chirp grating shown as a second conventional example disclosed in Japanese Unexamined Patent Publication (Kokai) No. H11-15095. In the second conventional example, in order to change the dispersion, the stage 7 is moved by the micrometer head 9 to apply a strain to the clamped fiber chirp grating 20. That is, when strain is applied to the grating portion, both Λ and neff change, so that λB can be changed. Here, the amount of change in the strain ε and the change in λB have the relationship shown in the following equation (2). ΔλB / λB = 0.78ε (2)

Therefore, by changing the strain generated in the grating portion, the dispersion can be controlled in accordance with the strain. As shown in FIG. 29, when an inclination occurs so that the average value of distortion changes, the center wavelength of the device changes. Therefore, in order for the center wavelength not to change, it is necessary to change the average value of the distortion so as not to change as shown in FIG. In this regard, in the second conventional example, the fiber chirped grating 20 is provided with an S-shaped bend so that the average value of the strain generated in the grating portion is always constant, and the center wavelength does not fluctuate. , Only the variance is changed. In the second conventional example, as a method of supporting the fiber chirp grating portion, an iron rod is used as a support, an adhesive is used to fix the fiber chirp grating 20 to the support, and the fiber is connected by a heat-shrinkable tube. The chirp grating 20 and the support are assembled.

[0009]

However, in the above-mentioned first conventional example, since a heater or the like must be used to generate a temperature gradient, there is a problem that power consumption is large, and temperature control is performed in several places. Since it is necessary to perform the control, there is a problem that the control is difficult. Also, the first
In the second conventional example, since the fiber chirp grating 20 is used, there is a problem that integration is difficult. Further, in the second conventional example, as described above, the fiber chirp grating 20 and the support are fixed, and the dispersion is controlled using very small strain. Therefore, the fixing method of the fiber chirp grating is poor. In addition, there are problems that dispersion control becomes difficult and reproducibility deteriorates.

Accordingly, an object of the present invention is to provide a variable dispersion equalizer that can reduce power consumption and improve controllability and reproducibility of dispersion.

[0011]

In order to achieve the above object, a first dispersion equalizer according to the present invention comprises an optical waveguide and a waveguide grating formed on a part of the optical waveguide. In a dispersion equalizer, a substrate is supported in at least two substrate support portions in a case, and the case is further provided with substrate pressing means for bending a portion of the substrate on which the waveguide grating is formed. One of the support portions is provided outside one end of the waveguide grating, the other is provided outside the other end of the waveguide grating, and the substrate pressing means is provided on one side of the waveguide grating. Or between the one end of the waveguide grating and the one substrate support portion. In the dispersion equalizer configured as described above, when the substrate is pressed by the substrate pressing means, a distortion that increases or decreases at a fixed ratio (linear) with respect to the position is formed in the portion where the waveguide grating is formed. Can be caused, so that the dispersion value to be compensated can be adjusted according to the gradient of the distortion.

Further, in the first dispersion equalizer according to the present invention, it is preferable that a heater for changing a temperature of a portion of the substrate on which the waveguide grating is formed is provided.

In a first dispersion equalizer according to the present invention, a plurality of the substrate pressing means are provided, and the first substrate pressing means, which is one of the plurality of substrate pressing means, is connected to one end of the waveguide grating. A second substrate pressing means, which is another one of the plurality of substrate pressing means, provided so as to press the substrate between one end of the portion or the waveguide grating and the one substrate supporting portion. The substrate may be provided so as to press the substrate between the other end of the waveguide grating or the other end of the waveguide grating and the other substrate support.

Further, in the first distributed equalizer, the first substrate pressing means presses from one main surface of the substrate, and the second substrate pressing means presses from the other main surface. Is preferred.

Further, in the first distributed equalizer,
The optical waveguide is formed on one main surface side of the substrate, and the plurality of substrate pressing means press each from one main surface of the substrate, and a metal plate is bonded to the other main surface of the substrate. You may make it.

Further, in the first dispersion equalizer, the optical waveguide may be an optical fiber embedded in a substrate.

In a second dispersion equalizer according to the present invention, a substrate including an optical waveguide and a waveguide grating formed on a part of the optical waveguide is supported in a case by a substrate supporting portion. In a dispersion equalizer in which a case is further provided with substrate pressing means for bending a portion of the substrate on which the waveguide grating is formed, one of the substrate support portions is provided at one end of the waveguide grating. It is provided outside, the other is provided outside the other end of the waveguide grating, the substrate is characterized in that the thickness or width sequentially changes from one end to the other end of the waveguide grating. I do.

In the first and second dispersion equalizers, at least one end of the substrate pressing means may have
A load dividing portion may be provided in which two portions come into contact with the substrate and the two portions press the substrate.

Further, in the first and second dispersion equalizers, a temperature detecting means for detecting a temperature of the optical waveguide grating, and a change corresponding to a temperature change based on the temperature detected by the temperature detecting means. And a pressing force control means for changing the pressing force applied to the substrate by the substrate pressing means so as to cancel the reflection center wavelength of the waveguide grating.

Further, in the first and second distributed equalizers, it is preferable that the substrate pressing means is movably provided so as to change the substrate pressing position in the horizontal direction.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a plan view (a) and a side view (b) of a dispersion equalizer according to a first embodiment of the present invention. The dispersion equalizer according to the first embodiment supports a substrate 3 on which an optical circuit for dispersion compensation using the optical waveguide 1 is formed in a case 7 using a substrate supporting portion 4, and further attaches the substrate 3 to the case 7.
Is a variable dispersion equalizer capable of adjusting a dispersion compensation value by providing a substrate pressing mechanism for bending a portion where the waveguide chirp grating 2 is formed.
Even if the above-described waveguide chirp grating is replaced with a waveguide grating having a uniform grating period, it can function as a variable dispersion equalizer.

Here, the optical circuit for dispersion compensation formed on the substrate 3 is composed of a pair of optical waveguides 1 on each of which a waveguide chirp grating 2 is formed, as shown in FIG.
It consists of. The pair of optical waveguides 1 are formed such that a part thereof is close to and coupled to each other, and the 3 dB coupler 5 is configured. In the first embodiment, a silicon substrate is used as the substrate 3, the optical waveguide 1 is formed on the silicon substrate by using a CVD (Chemical vapor deposition) method, and the waveguide chirp grating uses a photosensitive effect. It was formed by irradiation of ultraviolet laser light.

In the dispersion equalizer of the first embodiment, as shown in FIG. 1, the waveguide chirp grating 2 becomes larger as the period of the waveguide chirp grating becomes farther from the incident port side in order to obtain a positive dispersion characteristic. It is formed so that it becomes. An optical fiber connector 6 having ports P1 and P2 as input / output terminals is provided at one end of the substrate 3.

In the dispersion equalizer according to the first embodiment configured as described above, the light input from the port P 1 is split into two by the 3 dB coupler 5. The branched signal lights are respectively reflected by the waveguide chirp grating 2, multiplexed again by the 3 dB coupler 5, and output from the port P2. At this time, in the first embodiment, as described above, the period of the waveguide chirp grating 2 is increased with distance from the incident port side, so that light having a longer wavelength is reflected at a position further away from the incident port side, The group delay increases. As a result, an optical pulse signal that propagates through an optical fiber of several tens of kilometers and spreads due to the arrival of a long-wavelength light with a delay passes through a dispersion equalizer, and is thus transmitted as shown in FIG.
The waveform is corrected to the waveform before transmission through the optical fiber as shown in FIG.

In the distributed equalizer according to the first embodiment, the substrate pressing mechanism by the stress adjusting actuator 8 has a specific structure as described below, so that controllability and reproduction can be achieved with less power consumption than the conventional example. The dispersion compensation value can be adjusted efficiently. That is, the first embodiment
In the above, the substrate support 4, the substrate 3, and the stress adjusting actuator 8 are provided in the following positional relationship. Condition 1. One of the two substrate supports 4 is provided outside the input / output end (front end) of the waveguide chirp grating (input / output terminal side), and The other is provided outside the end (rear end) of the waveguide chirp grating that is remote from the input / output terminal, and supports the substrate 3 before and after the waveguide chirp grating 2. In this specification, the input / output side is referred to as front, and the open side is referred to as rear. Condition 2. The stress adjusting actuator 8 is provided so as to press the substrate between the rear end of the waveguide chirped grating 2 or between the rear end and the substrate supporting portion 4 located outside the rear end.

The substrate support 4, the substrate 3, and the stress adjusting actuator 8 are provided so that the positional relationship that satisfies the conditions 1 and 2 is provided. When the substrate 3 is bent, the stress (or strain) shown in FIG. In FIG. 2, the point indicated by S1 where the stress is the largest corresponds to the point where the substrate 3 is pressed by the stress adjusting actuator 8, and the points S2 and S3 at both sides where the stress is 0 are respectively determined by the substrate supporting portion 4. This corresponds to the point where the substrate 3 is supported. Lines L1, L2, L3 indicated by different line types are L3, L
This is a stress generated on the substrate when the pressing force is increased in order of 2 and L1. As described above, the largest strain occurs on the substrate 1 at the point of pressing the substrate 1, and the strain changes substantially linearly between the points S <b> 1 and S <b> 2 and the points S <b> 1 to S <b> 3, and the pressing force is The inclination changes correspondingly.

If the distortion can be linearly changed in this way, the amount of change in the Bragg wavelength represented by the equation (2) can also be linearly changed as shown in FIG. The variance value can be changed.
FIG. 3 shows the amount of change in the Bragg wavelength corresponding to the change in the amount of distortion between points S1 and S2 in FIG. The lines L11, L21, L31 in FIG.
Lines L12, L22, and L32 in FIG. 4 correspond to lines L1, L2, and L3 in FIG. 2, respectively.
1, L2 and L3. Here, in the dispersion equalizer of FIG. 1, since the respective elements are arranged so as to satisfy the conditions 1 and 2, the waveguide chirp grating 2 formed on the substrate 3 is positioned between S1 and S2 in FIG. It is provided to be. Therefore, according to the configuration of the first embodiment, the rate at which the grating period of the waveguide chirp grating increases can be changed by changing the stress that bends the substrate 3 by the stress adjusting actuator 8. As a result, as shown in FIG. 4, the dispersion compensation value can be changed.

As described above, in the first embodiment, the dispersion compensation value can be changed by arranging the elements so as to satisfy the positional relationship of the above-described conditions 1 and 2. When the stress that causes the substrate 3 to bend is changed by the actuator 8 for use, the center wavelength of the Bragg wavelength of the waveguide chirped grating changes to the line L1 in FIG.
3, L23 and L33. Therefore, the distributed equalizer according to the first embodiment further has a configuration shown in FIG.
As shown in the figure, even when a heater 9 is provided and the stress is adjusted by the stress adjusting actuator 8 to change the inclination of the black wavelength with respect to the position, the waveguide chirp grating 2 of the substrate 3 is changed so that the center wavelength C1 does not change. The temperature of the formed part is controlled. This situation is shown by line L in FIG.
14, L24 and L34.

The distributed equalizer according to the first embodiment configured as described above satisfies the conditions 1 and 2 described above.
Substrate 3, substrate support 4, and stress adjusting actuator 8
Are arranged and the dispersion compensation value is adjusted by controlling the strain (bending) of the substrate by the stress adjusting actuator 8, so that the control can be performed with a simpler configuration than in the first and second conventional examples. The dispersion compensation value can be adjusted with good reproducibility and reproducibility. Further, the dispersion equalizer of the first embodiment adjusts the dispersion compensation value by controlling the distortion (bending) of the substrate as described above, and the heater 9 cancels the change in the central wavelength of the Bragg wavelength due to the adjustment. Since the center wavelength is kept constant, the dispersion compensation value can be adjusted with better controllability and reproducibility.

Embodiment 2 FIG. FIG. 7 is a plan view (a) and a side view (b) of a dispersion equalizer according to a second embodiment of the present invention. In FIG. 7, the same components as those in FIG. 1 are denoted by the same reference numerals. The dispersion equalizer according to the second embodiment uses a substrate 31 in which the thickness of the substrate is gradually changed, and applies a load to the substrate 31 to deflect the substrate as shown in FIG. , The gradient of the strain amount with respect to the position is changed in accordance with the magnitude of the load. In other words, in the distributed equalizer according to the second embodiment, when a load is applied to the substrate and the substrate is bent, the distortion of the substrate is caused by L15, L25, and L3 in FIG.
As shown in FIG. 5, the thickness of the substrate is gradually changed so as to linearly change with respect to the position, and a waveguide chirp grating is formed at a portion where the thickness of the substrate is gradually changed. . Also in this case, the gradient of the distortion with respect to the position can be changed as indicated by L15, L25, and L35 in FIG. 8 according to the load, and dispersion compensation is performed in accordance with the gradient of the distortion as in the first embodiment. The value can be adjusted. In the second embodiment, similarly to the first embodiment, the heater 9 is used to control the center wavelength of the Bragg wavelength so as not to change. Even if the above-described waveguide chirp grating is replaced with a waveguide grating having a uniform grating period, it can function as a variable dispersion equalizer.

In the dispersion equalizer of the second embodiment configured as described above, since the substrate 31 whose thickness changes gradually is used, the substrate 31 is adjusted so as to satisfy the condition 1 described in the first embodiment. By arranging the substrate and the substrate support 4, the same operation and effect as those of the first embodiment can be obtained. Therefore, in the distributed equalizer according to the second embodiment, the substrate 3
There is no particular limitation on the position where a load is applied to deflect 1, so that it is not necessary to satisfy Condition 2 as in Embodiment 1. In the second embodiment, as one preferable example,
A load divider 10 is attached to the tip of the stress adjusting actuator 8.
And the load leading ends 10a, 10a of the load divider 10 are provided.
b applies a load to the substrate so as to straddle the waveguide chirp grating 2 back and forth.

The distributed equalizer of the second embodiment has the same configuration as that of the first embodiment except for the above.
Like the first embodiment, the dispersion equalizer of the second embodiment configured as described above has a simpler configuration than the first and second conventional examples, and has a controllability and a high reproducibility. Can be adjusted.

In the dispersion equalizer according to the second embodiment, the thickness of the substrate is gradually changed. However, the present invention is not limited to this. Instead of changing the thickness of the substrate, the width of the substrate is gradually changed. May be changed. Even in the case described above, the same operation and effect as in the second embodiment can be obtained. In the dispersion equalizer according to the second embodiment, the thickness of the entire substrate is gradually changed.
The present invention is not limited to this, and the thickness of the substrate at least at the portion where the waveguide chirp grating is formed may be gradually changed. Even in this case, the same operation and effect as in the second embodiment can be obtained.

Embodiment 3 FIG. 9 is a plan view (a) and a side view (b) of a dispersion equalizer according to a third embodiment of the present invention. The distributed equalizer of the third embodiment has the same configuration as that of the first embodiment except that the following is different from the distributed equalizer of the first embodiment.

Difference from the first embodiment. Instead of the stress adjusting actuator 8 of the first embodiment, two stress adjusting actuators 81 and 82 are used, and one main surface of the substrate 3 is pressed by the stress adjusting actuator 81. The other main surface of the substrate 3 is configured to be pressed. Accordingly, 1
The substrate 3 is supported by the pair of substrate supporting portions 4 so as to sandwich the substrate 3 outside the input / output side front end (input / output terminal side) of the waveguide chirp grating, and is guided by the other pair of substrate supporting portions 4. The substrate 3 is supported before and after the waveguide chirp grating 2 by sandwiching and supporting the substrate 3 outside the rear end of the waveguide chirp grating away from the input / output terminals. The stress adjusting actuator 81 is provided so as to press the upper surface of the substrate from above the rear end portion of the waveguide chirp grating 2 or between the rear end portion and the substrate supporting portion 4 located outside the rear end portion. Reference numeral 82 is provided so as to press the lower surface of the substrate from below the front end of the waveguide chirp grating 2 or between the front end and the substrate support 4 located outside the front end. Further, the heater 9 provided in the first embodiment is not provided in the third embodiment. Except as described above, the configuration is the same as that of the first embodiment. Even if the above-described waveguide chirp grating is replaced with a waveguide grating having a uniform grating period,
It can function as a variable dispersion equalizer.

The dispersion equalizer of the third embodiment configured as described above can perform control without using the temperature control heater 9 so that the center wavelength of the Bragg wavelength does not change. That is, in FIG. 9, while the substrate 3 is pressed downward by the stress adjusting actuator 81, the vicinity of the rear end of the waveguide chirp grating of the substrate 3 is curved downward, while the stress adjusting actuator 8 is pressed.
By pressing the substrate 3 upward with 2, the vicinity of the front end of the waveguide chirp grating of the substrate 3 is curved upward.
In this way, as shown by L16, L26, and L36 in FIG. 10, distortion occurs in the direction in which the grating period increases near the rear end of the waveguide chirp grating 2, and near the front end of the waveguide chirp grating 2. Distortion occurs in the direction in which the grating period becomes smaller, and the distortion becomes just zero at the center of the waveguide chirp grating 2 (indicated by C1 in FIG. 10). As a result, the dispersion value can be controlled so that the central wavelength of the Bragg wavelength does not change.

Therefore, in the third embodiment configured as described above, the dispersion compensation value can be adjusted similarly to the first and second embodiments, and the center of the Bragg wavelength can be adjusted without using the heater 9. Since the fluctuation of the wavelength can be eliminated, the power consumption can be made substantially zero.

Embodiment 4 FIG. FIG. 11 is a plan view (a) and a side view (b) of a dispersion equalizer 12 according to a fourth embodiment of the present invention. The distributed equalizer according to the fourth embodiment includes:
In the dispersion equalizer of the third embodiment, the stress adjusting actuator 82 presses the upper surface of the substrate from above the front end of the waveguide chirp grating 2 or between the front end and the substrate support 4 located outside the front end. Except for being provided, the configuration is the same as that of the third embodiment. Even if the above-described waveguide chirp grating is replaced with a waveguide grating having a uniform grating period, it can function as a variable dispersion equalizer.

In the distributed equalizer of the fourth embodiment configured as described above, by adjusting the two stress adjusting actuators 81 and 82, the strain generated on the substrate can be changed as shown in FIG. Specifically, when the substrate is distorted only by the stress adjusting actuator 82, the distortion is generated as indicated by a dotted line L37,
When the substrate is distorted only by the stress adjusting actuator 81, the substrate can be distorted as indicated by a broken line L17. When voltage is applied by the stress adjusting actuators 81 and 82 with the same certain strength, the solid line L
The result is as shown in FIG. Further, by continuously changing the applied stress by the stress adjusting actuators 81 and 82, it is possible to set the distortion having various inclinations between the dotted line L37 and the broken line L17, thereby continuously changing the dispersion correction value. Can be.

As described above, in the distributed equalizer according to the fourth embodiment, the two stress adjusting actuators 81 and 8 are used.
By adjusting 2, a distortion having linear and various inclinations can be generated in a portion of the substrate 3 where the waveguide chirp grating 2 is formed. Also,
Even if the inclination of the strain amount with respect to the position is variously changed in accordance with the force pressing the substrate 3, the strain amount at the central portion of the waveguide chirp cladding 2 can be kept constant (C3 in FIG. 12).
Point), the center wavelength of the Bragg wavelength can be kept from changing. In the dispersion equalizer according to the fourth embodiment, when a distortion corresponding to C3 in FIG. 12 is applied to the central portion of the waveguide chirp cladding 2, the waveguide chirp cladding is adjusted so as to have a desired center wavelength. Initialize the cycle of 2.

The dispersion equalizer according to the fourth embodiment having the above-described configuration can be used when a distortion corresponding to C3 in FIG. 12 is applied to the center of the waveguide chirp cladding 2.
Except that it is necessary to offset and initialize the period of the waveguide chirp cladding 2 so that the desired center wavelength is obtained, the same effect as the dispersion equalizer of the third embodiment is obtained.

Embodiment 5 FIG. FIG. 13 is a plan view (a) and a side view (b) of a dispersion equalizer according to a fifth embodiment of the present invention. In the distributed equalizer according to the fifth embodiment,
The substrate 3 is supported by a stress adjusting actuator 82 provided at the lower part of the case 7 and having a load divider 10 at the tip and a substrate supporter 4 provided at the upper part of the case. Here, the load divider 10 has a load 10c and a load 1
0d, and is in contact with the substrate 3 so as to straddle the waveguide chirp grating 2 by the load portions 10c and 10d. Then, the stress adjusting actuator 81
Is provided so as to press the substrate 3 from above between the rear end of the waveguide chirp grating 2 and the load portion 10c.

In the distributed equalizer of the fifth embodiment configured as described above, the stress adjusting actuator 81
When a load is applied to the substrate only by itself, the amount of strain and the slope of the strain with respect to the position can be changed, and the dispersion value and the center wavelength change. The stress adjusting actuator 82
When a load is applied to the substrate only by using only the center wavelength, only the center wavelength can be changed. As a result, by adjusting the strengths of the stresses applied by the stress adjusting actuators 81 and 82, the strains L18, L28 and L38 in FIG. 14 can be generated on the substrate 3 and the strain at the point C4 can be reduced. Can be constant. Therefore, Embodiment 5
With the configuration described above, only the dispersion can be changed without changing the center wavelength. That is, the dispersion equalizer according to the fifth embodiment has the same operation and effect as the fourth embodiment. Even if the above-described waveguide chirp grating is replaced with a waveguide grating having a uniform grating period, it can function as a variable dispersion equalizer.

Embodiment 6 FIG. FIG. 15 is a plan view (a) and a side view (b) of a dispersion equalizer according to a sixth embodiment of the present invention. In the distributed equalizer according to the sixth embodiment,
A metal plate 11 is bonded to the surface of the substrate 3 where the optical waveguide 1 and the waveguide chirp grating 2 are not formed, and the configuration is as follows. In the sixth embodiment, the metal plate 11
The substrate 3 is supported in the case 7 so that the substrate 3 contacts the substrate support 4. Here, the substrate supporting portions are respectively provided outside the waveguide chirp gratings. Further, the stress adjusting actuator 81 is provided so as to press the substrate between the front end of the waveguide chirp grating 2 or between the front end and the substrate supporting portion 4 located outside the front end, and the stress adjusting actuator 82 includes: The waveguide chirp grating 2 is provided so as to press the substrate between or on the rear end of the waveguide chirped grating 2 and the substrate support 4 located outside the rear end.

In the distributed equalizer of the sixth embodiment configured as described above, the stress adjusting actuator 81
When a load is applied to the substrate only by using the dotted line L in FIG.
When a load is applied to the substrate by only the stress adjusting actuator 82 as shown by 39, a distortion is generated as shown by a broken line L19. When a load is applied to the substrate with the same strength by the stress adjusting actuators 81 and 82, a strain is generated as shown by a solid line L29. By continuously changing the stress applied to the substrate by the stress adjusting actuators 81 and 82, as shown in FIG.
Distortions having various inclinations between L19 and L39 can be generated on the substrate, and the variance value can be changed correspondingly. Further, as shown in FIG. 16, also with the configuration of the sixth embodiment, the amount of distortion can be made constant at point C5 at the center of the waveguide chirped grating 2, and only the dispersion is changed so that the center wavelength is not changed. be able to. Therefore, also in the sixth embodiment, there is no need to perform temperature control using a heater or the like. Further, in the dispersion equalizer of the sixth embodiment configured as described above, the breaking strength of the substrate 3 can be improved by attaching the metal plate 11 to the back surface of the substrate 3, and therefore, compared to the fourth embodiment. The variable dispersion amount can be increased about 10 times. Even if the above-described waveguide chirp grating is replaced with a waveguide grating having a uniform grating period, it can function as a variable dispersion equalizer.

Embodiment 7 FIG. FIG. 17 is a plan view (a) and a side view (b) of a dispersion equalizer 12 according to a seventh embodiment of the present invention. FIG. 17C shows the substrate 13.
FIG. 17B is an end view as viewed from the direction of the arrow in FIG. The dispersion equalizer shown in FIG. 17 has an optical fiber 12 in which a fiber chirp grating 13 is partially formed.
Is embedded in the case 7 as described below, and the circulator 14 is combined with a light reflection circuit section.

More specifically, the substrate 3 is supported in the case 7 such that the surface on which the optical fiber 12 is embedded contacts the substrate support 4. Here, the substrate supporting portions 4 are provided so as to be located outside the fiber chirp grating 13. Further, the stress adjusting actuator 81 is provided so as to press the substrate between the rear end of the fiber chirp grating 13 or between the rear end and the substrate supporting portion 4 located outside the rear end.
Is provided so as to press the substrate between the front end of the fiber chirped grating 13 or between the front end and the substrate support 4 located outside the front end. Here, the fiber chirp grating 13 can be formed by irradiating an ultraviolet laser beam utilizing a photo-sensitive effect, and the optical fiber is embedded in the groove formed in the grooved silicon substrate with an adhesive. The substrate 3 may be made of quartz or metal other than silicon. When a metal substrate is used, it is desirable to use a metal having a low thermal expansion close to the coefficient of thermal expansion of the optical fiber, such as Invar, in order to suppress a variation in strain due to temperature.

In the dispersion equalizer configured as described above, light input from the port P1 passes through the circulator 14, is reflected by the fiber chirp grating 13, passes through the circulator 14, and is output from the port P2. In this dispersion equalizer, as in Embodiments 1 to 6 using a waveguide, the period of the fiber chirped grating is increased as the distance from the incident port increases in order to obtain positive dispersion. Even with the dispersion equalizer configured as described above, an optical pulse signal that has spread by propagating through a fiber of several tens of kilometers can be made as shown in FIG. 23A by passing through the dispersion equalizer. Is corrected.

In the dispersion equalizer according to the seventh embodiment configured as described above, since the optical fiber 12 is embedded in the groove of the substrate 3 with an adhesive, the optical fiber having the same distortion as the distortion of the substrate is embedded. And the variance can be adjusted on the same principle as in the fourth embodiment. That is, as shown in FIG. 17B, two stress adjusting actuators 8 are used.
When a stress is applied by the pressures 1 and 82, the stress and the strain are changed to FIG.
And the variance can be adjusted. Therefore, the same effect as that of the fourth embodiment can be obtained by the dispersion equalizer of the seventh embodiment. When metal is used for the substrate, use of invar or the like having a coefficient of thermal expansion relatively close to that of an optical fiber can increase the reliability against peeling of the fiber chirp grating due to a change in ambient temperature. Even if the above-described waveguide chirp grating is replaced with a waveguide grating having a uniform grating period, it can function as a variable dispersion equalizer.

Embodiment 8 FIG. FIG. 18 is a plan view (a) and a side view (b) of a dispersion equalizer according to an eighth embodiment of the present invention. The dispersion equalizer of the eighth embodiment differs from the dispersion equalizer of the fourth embodiment in that, based on the temperature detected by the temperature detection mechanism 15 and the temperature detected by the temperature detection mechanism 15, the temperature fluctuation of the center wavelength of the waveguide chirp grating 2 or Control means (not shown) for controlling the applied stress of the stress adjusting actuators 81 and 82 so as to cancel the fluctuation of the dispersion value due to the temperature is provided. With such a configuration, when the ambient temperature changes, the center wavelength due to the change in the refractive index of the grating changes, and the stress applied by the actuator is adjusted based on the temperature detected by the temperature detection mechanism 15 to adjust the center wavelength. Temperature fluctuations,
That is, the fluctuation of the dispersion value due to the temperature is compensated.

The dispersion equalizer according to the eighth embodiment having such a configuration has the same operation and effect as the fourth embodiment.
Furthermore, it is possible to compensate for a change in the dispersion value due to a temperature change during use. That is, when the ambient temperature fluctuates during operation, the Bragg wavelength also fluctuates as shown in FIG. 19, so that the center wavelength also fluctuates. When the ambient temperature increases, the Bragg wavelength increases as indicated by the broken line L100 in FIG. 19, and accordingly, if the applied stress by both the actuators 81 and 82 is reduced,
The stress and strain applied to the waveguide chirp grating are reduced without changing the inclination, as indicated by the broken line L101 in FIG. 20, so that the fluctuation of the center wavelength due to the temperature can be compensated.

In the above-described eighth embodiment, the example in which the temperature detecting mechanism 15 is provided in the dispersion equalizer of the fourth embodiment has been described. However, the present invention is not limited to this, and the dispersion equalizer of the other embodiments may be used. In the equalizer, the temperature detection mechanism 15 may be provided. For example, in the distributed equalizer of FIG.
If a mechanism is provided to reduce the applied stress by the stress adjusting actuator 81 when the temperature rises and to increase the applied stress by the stress adjusting actuator 82, the fluctuation of the center wavelength due to the ambient temperature can be compensated. Can be. Even if the above-described waveguide chirp grating is replaced with a waveguide grating having a uniform grating period, it can function as a variable dispersion equalizer.

Embodiment 9 FIG. FIG. 21 is a plan view (a) and a side view (b) of a dispersion equalizer according to a ninth embodiment of the present invention. The dispersion equalizer according to the ninth embodiment differs from the dispersion equalizer according to the first embodiment in that the stress adjustment actuator 8 can be moved in the horizontal direction. In the dispersion equalizer of the ninth embodiment configured as described above, the stress adjusting actuator 8 is moved in the vertical direction to apply a stress of a predetermined strength, thereby obtaining the dispersion value as described in the first embodiment. Can be adjusted to a desired value. Further, by making the actuator 8 movable in the horizontal direction, the distribution of stress and strain can be changed as shown in FIG. 22, and the variance can be adjusted. Therefore, with the dispersion equalizer of the ninth embodiment, the same operation and effect as those of the first embodiment can be obtained, and further, fine adjustment of the dispersion compensation value becomes possible.

Further, in the dispersion equalizer of the ninth embodiment, the dispersion compensation value can be adjusted by moving the actuator 8 in the horizontal direction while keeping the force pressing the substrate constant. Even if the above-described waveguide chirp grating is replaced with a waveguide grating having a uniform grating period, it can function as a variable dispersion equalizer.

As described above, according to the distributed equalizers of the embodiments according to the present invention, any of the configurations requires less power consumption and higher dispersion controllability and reproducibility as compared with the conventional example. A variable dispersion equalizer can be provided. Further, according to the dispersion equalizer according to the other embodiments except the seventh embodiment, since the waveguide chirp grating formed on the substrate is used, integration with other optical components such as a 3 dB coupler is possible. It is.

In the first, fifth, and ninth embodiments, the stress adjusting actuator 8 is provided between the front end of the waveguide chirped grating 2 or the front end and the substrate supporting portion. However, the present invention is not limited to this, and the stress adjusting actuator 8 may be provided at the rear end of the waveguide chirp grating 2 or between the rear end and the substrate support. Even in the case described above, Embodiment 1,
It has the same function and effect as 5 and 9. In the first, second, third, fourth, fifth, seventh, eighth and ninth embodiments, the waveguide or the optical fiber is provided on the lower surface of the substrate. However, the present invention is not limited to this. Alternatively, a waveguide or an optical fiber may be provided on the upper surface of the substrate.
Even in the above manner, Embodiments 1, 2, 3,
It has the same function and effect as 4, 5, 7, 8, and 9. Also,
In the sixth embodiment, the waveguide is provided on the upper surface of the substrate. However, the present invention is not limited to this, and the waveguide may be provided on the lower surface of the substrate. Even in the case described above, the same operation and effect as those of the sixth embodiment can be obtained.

[0057]

As described above, the first embodiment according to the present invention is described.
The dispersion equalizer is provided with a substrate pressing means for supporting the substrate on which the waveguide grating is formed by a substrate supporting portion and bending a portion on which the waveguide grating is formed, wherein the substrate supporting portion is The substrate pressing means is provided outside the waveguide grating, and presses the substrate between one end of the waveguide grating or one end of the waveguide grating and the one substrate support. Since the substrate grating is provided, by pressing the substrate by the substrate pressing means, it is possible to generate a strain that increases or decreases at a fixed rate (linear) with respect to the position in the portion where the waveguide grating is formed. it can. Accordingly, the first dispersion equalizer according to the present invention can adjust the dispersion value to be compensated in accordance with the gradient of the distortion, so that the power consumption can be reduced, and the variable dispersion with high controllability and reproducibility of dispersion can be achieved. An equalizer can be provided.

Further, in the first dispersion equalizer according to the present invention, by providing a heater for changing the temperature of the portion of the substrate where the waveguide grating is formed, the center wavelength of the waveguide grating due to stress is provided. Changes can be counteracted.

Further, in the first dispersion equalizer according to the present invention, the substrate pressing means is provided in a plurality, and the first substrate pressing means is provided at one end of the waveguide grating or at one end of the waveguide grating. Provided so as to press the substrate between the end portion and the one substrate support portion, and the second substrate pressing means is provided with the other end portion of the waveguide grating or the other end portion of the waveguide grating and the other end portion. By providing the substrate so as to press it between the substrate supporting portions, the dispersion compensation value can be finely adjusted.

In the first dispersion equalizer, the first substrate pressing means presses from one main surface of the substrate, and the second substrate pressing means presses from the other main surface. By doing so, without providing a heater,
The center wavelength can be kept constant.

Further, in the first distributed equalizer,
The optical waveguide is formed on one main surface side of the substrate, and the plurality of substrate pressing means press each from one main surface of the substrate, and a metal plate is bonded to the other main surface of the substrate. By doing so, a larger distortion can be generated, so that the adjustment amount of the dispersion compensation value can be increased.

Further, in the first dispersion equalizer, the optical waveguide is an optical fiber embedded in a substrate, whereby a dispersion equalizer using an optical fiber can be provided.

Further, the second dispersion equalizer according to the present invention is characterized in that a substrate provided with a waveguide grating is supported in a case by a substrate support, and a substrate pressing means for bending a portion where the waveguide grating is formed. In the dispersion equalizer provided with, provided outside the waveguide grating of the substrate support portion, the substrate,
Since the thickness or the width is sequentially changed from one end to the other end of the waveguide grating, an inclined strain can be generated in the substrate corresponding to the change in the thickness or the width, and the dispersion value to be compensated for Can be adjusted in accordance with the gradient of the distortion, so that the power consumption can be reduced, and a variable dispersion equalizer with high controllability and reproducibility of dispersion can be provided.

In the first and second dispersion equalizers, at least one tip of the substrate pressing means is provided
By providing a load dividing portion that comes in contact with the substrate at two portions and presses the substrate at the two portions, the load applied to the substrate can be dispersed, so that destruction of the substrate can be prevented.

Further, in the first and second dispersion equalizers, a temperature detecting means for detecting a temperature of the optical waveguide grating, and a change corresponding to a temperature change based on the temperature detected by the temperature detecting means. By providing a pressing force control means for changing the pressing force applied to the substrate by the substrate pressing means so as to cancel the reflection center wavelength of the waveguide grating, the fluctuation of the center wavelength due to the ambient temperature can be compensated.

Further, in the first and second distributed equalizers, the substrate pressing means is movably provided so as to change the substrate pressing position in the horizontal direction.
Fine adjustment of the dispersion compensation value becomes possible.

[Brief description of the drawings]

FIG. 1 is a plan view (a) and a side view (b) of a dispersion equalizer according to a first embodiment of the present invention.

FIG. 2 is a graph showing a distribution of strain generated in the substrate when a load is applied to the substrate in the distributed equalizer according to the first embodiment.

FIG. 3 is a graph showing a change in Bragg wavelength that occurs in response to a distortion of a substrate when a load is applied to the substrate in the dispersion equalizer according to the first embodiment;

FIG. 4 is a graph showing a change in a dispersion compensation value when a load applied to a substrate is changed in the dispersion equalizer according to the first embodiment.

FIG. 5 is a graph showing a change in center wavelength when a load applied to a substrate is changed without using a heater 9 in the dispersion equalizer according to the first embodiment.

FIG. 6 is a graph showing a Bragg wavelength when a change in the center wavelength is compensated for using the heater 9 in the dispersion equalizer of the first embodiment.

FIG. 7 is a plan view (a) and a side view (b) of a dispersion equalizer according to a second embodiment of the present invention.

FIG. 8 is a graph showing a distribution of strain generated in a substrate when a load is applied to the substrate in the distributed equalizer according to the second embodiment.

FIG. 9 is a plan view (a) and a side view (b) of a dispersion equalizer according to a third embodiment of the present invention.

FIG. 10 shows a distributed equalizer according to the third embodiment.
5 is a graph showing a distribution of strain generated in a substrate when a load is applied to the substrate.

FIG. 11 is a plan view (a) and a side view (b) of a dispersion equalizer according to a fourth embodiment of the present invention.

FIG. 12 illustrates a distributed equalizer according to a fourth embodiment.
5 is a graph showing a distribution of strain generated in a substrate when a load is applied to the substrate.

FIG. 13 is a plan view (a) and a side view (b) of a dispersion equalizer according to a fifth embodiment of the present invention.

FIG. 14 shows a distributed equalizer according to a fifth embodiment.
5 is a graph showing a distribution of strain generated in a substrate when a load is applied to the substrate.

FIG. 15 is a plan view (a) and a side view (b) of a dispersion equalizer according to a sixth embodiment of the present invention.

FIG. 16 illustrates a distributed equalizer according to the sixth embodiment.
5 is a graph showing a distribution of strain generated in a substrate when a load is applied to the substrate.

FIG. 17 is a plan view (a), a side view (b), and an end view (c) of a dispersion equalizer according to a seventh embodiment of the present invention.

FIG. 18 is a plan view (a) and a side view (b) of a dispersion equalizer according to an eighth embodiment of the present invention.

FIG. 19 illustrates a distributed equalizer according to the eighth embodiment.
5 is a graph showing Bragg wavelength with respect to position in accordance with temperature change.

FIG. 20 illustrates a distributed equalizer according to the eighth embodiment.
5 is a graph showing a distribution of strain generated in a substrate when a load is applied to the substrate.

FIG. 21 is a plan view (a) and a side view (b) of a dispersion equalizer according to a ninth embodiment of the present invention.

FIG. 22 illustrates a distributed equalizer according to the ninth embodiment.
5 is a graph showing a distribution of strain generated in a substrate when a load is applied to the substrate.

FIG. 23 shows a pulse waveform (a) before transmission through an optical fiber and a pulse waveform (b) after transmission.

FIG. 24 is a graph showing group delay (a) and dispersion (b) of an optical fiber.

FIG. 25 is a graph showing a group delay (a) and a variance (b) required as a distributed equalizer.

FIG. 26 is a schematic diagram showing an example of the configuration of a distributed equalizer.

FIG. 27 is a schematic configuration diagram of a first conventional example.

FIG. 28 is a schematic configuration diagram of a second conventional example.

FIG. 29 is a graph showing distortion generated in a waveguide grating.

FIG. 30 is a graph showing distortion required for a distributed equalizer.

[Explanation of symbols]

1 optical waveguide, 2 waveguide grating, 3 substrate,
4 board support section, 5 3 dB coupler, 6 optical fiber connector, 7 case, 8 stress adjustment actuator,
9 heater, 10 load divider, 11 metal plate, 12
Optical fiber, 13 fiber chirp grating, 14 circulator, 15 temperature detector.

Continuing from the front page (72) Inventor Junichiro Hoshizaki 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Takuya Ohira 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Co., Ltd. In-company (72) Inventor Gen Takeya 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Within Mitsubishi Electric Corporation (72) Inventor Shigeru Matsuno 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Yoshishin Kiyoshi 2-3-3 Marunouchi, Chiyoda-ku, Tokyo F-term in Mitsubishi Electric Corporation (reference) 2H041 AA21 AB10 AB38 AC01 AC07 AZ02 2H047 KA03 KA12 KB04 LA03 NA10 RA00 2H049 AA51 AA59 AA62 AA66 AA68

Claims (10)

[Claims] A substrate having an optical waveguide and a waveguide grating formed on a part of the optical waveguide is supported in a case by at least two substrate supports, and the case further includes In a dispersion equalizer provided with a substrate pressing unit that bends a portion where the waveguide grating is formed, one of the substrate support portions is provided outside one end of the waveguide grating, and the other is the other. The substrate pressing means is provided outside the other end of the waveguide grating, and the substrate pressing means is provided between the one end of the waveguide grating or one end of the waveguide grating and the one substrate support. A distributed equalizer characterized by being provided so as to press. 2. The dispersion equalizer according to claim 1, further comprising a heater for changing a temperature of a portion of said substrate on which said waveguide grating is formed. 3. The apparatus according to claim 1, further comprising a plurality of said substrate pressing means, wherein said first substrate pressing means, which is one of said plurality of substrate pressing means, comprises one end of said waveguide grating or one end of said waveguide grating. The second substrate pressing means, which is provided to press the substrate between the portion and the one substrate supporting portion, and is another one of the plurality of substrate pressing means, includes the other end of the waveguide grating. 3. The dispersion equalizer according to claim 1, wherein the dispersion equalizer is provided so as to press the substrate between the other end of the waveguide grating and the other substrate support. 4. The dispersion equalizer according to claim 3, wherein said first substrate pressing means presses from one main surface of said substrate, and said second substrate pressing means presses from the other main surface. 5. The optical waveguide is formed on one main surface side of the substrate, the plurality of substrate pressing means respectively press from one main surface of the substrate, and a metal is provided on the other main surface of the substrate. 4. The dispersion equalizer according to claim 3, wherein the plates are joined. 6. The dispersion equalizer according to claim 1, wherein said optical waveguide is an optical fiber embedded in a substrate. 7. A substrate provided with an optical waveguide and a waveguide grating formed in a part of the optical waveguide is supported in a case by a substrate support, and the case further includes the waveguide of the substrate. In a dispersion equalizer provided with substrate pressing means for bending a portion where a grating is formed, one of the substrate support portions is provided outside one end of the waveguide grating, and the other is the waveguide grating. Wherein the thickness of the substrate changes from one end to the other end of the waveguide grating sequentially from the other end of the waveguide grating. 8. A load dividing portion provided at at least one end of said substrate pressing means, wherein said load dividing portion contacts said substrate at two portions and presses said substrate at said two portions. A distributed equalizer according to one of the above. 9. A temperature detecting means for detecting a temperature of the optical waveguide grating, and a reflection center wavelength of the waveguide grating, which changes in response to a temperature change, is canceled based on the temperature detected by the temperature detecting means. 9. The dispersion equalizer according to claim 1, further comprising a pressing force control unit that changes a pressing force applied to the substrate by the substrate pressing unit. 10. The dispersion equalizer according to claim 1, wherein said substrate pressing means is movably provided to change a substrate pressing position in a horizontal direction.