WO2018146796A1 - Light modulation module - Google Patents
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- WO2018146796A1 WO2018146796A1 PCT/JP2017/004938 JP2017004938W WO2018146796A1 WO 2018146796 A1 WO2018146796 A1 WO 2018146796A1 JP 2017004938 W JP2017004938 W JP 2017004938W WO 2018146796 A1 WO2018146796 A1 WO 2018146796A1
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- light
- modulator
- modulators
- modulation module
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- 230000003287 optical effect Effects 0.000 claims description 321
- 230000008033 biological extinction Effects 0.000 claims description 26
- 230000005684 electric field Effects 0.000 description 17
- 239000004065 semiconductor Substances 0.000 description 15
- 230000000694 effects Effects 0.000 description 14
- 230000031700 light absorption Effects 0.000 description 11
- 238000010586 diagram Methods 0.000 description 10
- 230000007274 generation of a signal involved in cell-cell signaling Effects 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000010521 absorption reaction Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000005699 Stark effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
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- 229910052710 silicon Inorganic materials 0.000 description 1
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0121—Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/524—Pulse modulation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/54—Intensity modulation
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction
- G02F1/0155—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction modulating the optical absorption
- G02F1/0157—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction modulating the optical absorption using electro-absorption effects, e.g. Franz-Keldysh [FK] effect or quantum confined stark effect [QCSE]
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2201/00—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00
- G02F2201/16—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00 series; tandem
Definitions
- the present invention relates to an optical modulation module that outputs an optical modulation signal corresponding to an electric signal.
- Patent Document 1 proposes a Mach-Zehnder modulator in which a phase modulation unit is divided into a plurality of means as means for realizing multilevel modulation using a simple electric signal generation circuit.
- a multi-level modulation signal such as a PAM4 signal can be generated using a plurality of OOK signals that can be generated by a simple circuit.
- the present invention has been made in view of the above, and an object of the present invention is to obtain an optical modulation module capable of generating a multi-level modulation signal without requiring precise phase control.
- an optical modulation module includes a first optical modulator that performs optical intensity modulation on continuous light, and an optical intensity by the first optical modulator.
- a second light modulator that performs light intensity modulation on the modulated light; and a third light modulator that performs light intensity modulation on the light that has been light intensity modulated by the second light modulator.
- the light modulation module applies a first electric signal, which is a binary electric signal, to the first optical modulator, and applies a second electric signal, which is a binary electric signal, to the second optical modulator.
- a signal generator that applies a third electrical signal, which is a binary electrical signal, to the third optical modulator.
- the light modulation module according to the present invention produces an effect that a multi-level modulation signal can be generated without requiring precise phase control.
- FIG. 1 is a block diagram showing a configuration example of a light modulation module according to a first embodiment.
- FIG. The figure which shows the value which the PAM4 signal output from an optical modulation module, ie, an output signal, and the electric signal applied to each optical modulator The figure which shows an example of the voltage dependence of the extinction characteristic of Embodiment 1, and the amplitude of each electric signal External view showing a mounting example of the light modulation module of the first embodiment External view showing a mounting example of the light modulation module of the second embodiment
- FIG. 1 is a block diagram illustrating a configuration example of the light modulation module according to the first embodiment of the present invention.
- an optical modulation module 100 according to the present embodiment includes optical modulators 1 to 3 and an electric signal generation unit 4.
- the light modulation module 100 generates and outputs a light modulation signal based on a given signal, that is, information.
- the light modulation module 100 is used in, for example, an optical communication device.
- the information described above is information to be transmitted.
- the optical modulator 1 receives continuous light (CW: Continuous Wave) output from a light source (not shown in FIG. 1), modulates the intensity of the continuous light, and outputs a first optical modulation signal that is a signal after intensity modulation. Output.
- the light source may be provided inside the light modulation module 100 or may be provided outside the light modulation module 100.
- the optical modulator 2 receives the first optical modulation signal output from the optical modulator 1, intensity-modulates the first optical modulation signal, and outputs a second optical modulation signal that is a signal after intensity modulation.
- the optical modulator 3 receives the second optical modulation signal output from the optical modulator 2, intensity-modulates the second optical modulation signal, and outputs a third optical modulation signal that is a signal after intensity modulation. .
- the optical modulator 1 is a first optical modulator that performs optical intensity modulation on continuous light.
- the light modulator 2 is a second light modulator that performs light intensity modulation on the light whose light intensity is modulated by the light modulator 1.
- the light modulator 3 is a third light modulator that performs light intensity modulation on the light whose light intensity is modulated by the light modulator 2.
- the electrical signals output from the electrical signal generator 4 are applied to the optical modulators 1 to 3, respectively.
- the optical modulators 1 to 3 are formed of semiconductors having the same band structure.
- the optical modulators 1 to 3 are optical modulators called EAM (Electro-Absorption Modulator) using the semiconductor electroabsorption effect, that is, electroabsorption optical modulators.
- the electric field absorption effect of a semiconductor is a phenomenon in which, when an electric field is applied to a semiconductor provided with a quantum well structure, the band gap changes due to the Franz Kelish effect or the quantum Stark effect, and the amount of light absorption changes. Due to this phenomenon, the optical modulators 1 to 3 absorb light by reducing the band gap when an electric field is applied compared to when no electric field is applied. Therefore, the optical modulators 1 to 3 change the amount of light absorption in accordance with the applied electric field, that is, the voltage of the electric signal output from the electric signal generator 4, and change the intensity of the output optical signal. Can do.
- the electric signal generator 4 generates an electric signal for controlling whether or not an electric field is applied to the optical modulators 1 to 3.
- the signals applied from the electric signal generator 4 to the optical modulators 1 to 3 are binary signals indicating ON or OFF. That is, the electrical signal generation unit 4 applies a first electrical signal that is a binary electrical signal to the first optical modulator, and a second electrical signal that is a binary electrical signal is subjected to the second optical modulation. And a signal generator that applies a third electrical signal, which is a binary electrical signal, to the third optical modulator.
- the voltage value of the electrical signal is a first voltage value when off (OFF), and a second voltage value lower than the first voltage value when on (ON).
- the state corresponding to the case where the level of the PAM4 signal output from the light modulation module 100 is high is referred to as ON, and the state corresponding to the case where the level of the PAM4 signal is low. Call off. Therefore, the voltage applied to each optical modulator in the present embodiment is off because the higher the voltage, the lower the level because the amount of light absorption is larger, and the lower the voltage, the smaller the amount of light absorption. Turns on because the level is higher.
- This definition of on and off is an example, and the definition may be reversed between on and off.
- the electric signal generation unit 4 When the electrical signal is off, an electric field is applied to each optical modulator to which the electrical signal is applied. When the electrical signal is on, an electric field is not applied to each optical modulator to which the electrical signal is applied.
- a value obtained by subtracting the second voltage value from the first voltage value is referred to as amplitude.
- a central voltage between the first voltage value and the second voltage value is referred to as a bias value.
- the electric signal generation unit 4 generates an electric signal to be applied to the optical modulators 1 to 3 according to the value of one unit signal, that is, two-bit data, with 2 bits of the given signal as one unit.
- One unit of signal is one of four values of 00, 01, 10, and 11 expressed in binary.
- the electrical signal generator 4 which is a drive circuit for the optical modulators 1 to 3 outputs binary signals to the optical modulators 1 to 3, respectively, it is realized by a simple circuit that generates a binary signal, that is, an OOK signal. Can do.
- each of the optical modulators 1 to 3 performs binary modulation, but the optical modulators 1 to 3 are arranged in series to sequentially perform optical modulation.
- the signal finally output from the optical modulator 3 becomes a PAM4 signal which is a four-level optical modulation signal.
- FIG. 2 is a diagram for explaining the operation of the light modulation module according to the present embodiment.
- an OOK signal # 1 that is a first electric signal applied from the electric signal generator 4 to the optical modulator 1 and a second signal applied from the electric signal generator 4 to the optical modulator 2 are displayed.
- 3 schematically shows an OOK signal # 2 that is an electrical signal and an OOK signal # 3 that is a third electrical signal applied to the optical modulator 3 from the electrical signal generator 4.
- the light intensity when continuous light is output as it is without being absorbed by any of the optical modulator 1, the optical modulator 2, and the optical modulator 3 is a value of 11.
- the light intensity when light is absorbed by the optical modulator 1 and output from the optical modulator 3 without being absorbed by the optical modulator 2 and the optical modulator 3 is made to correspond to a value of 10.
- the optical modulator 1 performs optical modulation, that is, 11/10 modulation that generates an optical modulation signal corresponding to one of the two values of 11 and 10 depending on whether or not an electric field is applied. Do.
- the light intensity when light is absorbed by the light modulator 2 and output from the light modulator 3 without being absorbed by the light modulator 1 and the light modulator 3 is made to correspond to a value of 01.
- the light absorption amount in the optical modulator 2 is larger than the light absorption amount in the optical modulator 1. That is, the amplitude of the OOK signal # 2 is larger than the amplitude of the OOK signal # 1.
- the optical modulator 2 performs optical modulation, that is, 11/01 modulation, which generates an optical modulation signal corresponding to one of the two values of 11 and 01 depending on whether or not an electric field is applied. Do.
- the light intensity when light is absorbed by the optical modulator 3 and output from the optical modulator 3 without being absorbed by the optical modulator 1 and the optical modulator 2 is made to correspond to a value of 00.
- the light absorption amount in the optical modulator 3 is larger than the light absorption amount in the optical modulator 2. That is, the amplitude of the OOK signal # 3 is larger than the amplitude of the OOK signal # 2.
- the optical modulator 3 performs optical modulation, that is, 11/00 modulation that generates an optical modulation signal corresponding to one of the two values of 11 and 00 depending on whether or not an electric field is applied. Do.
- FIG. 3 is a diagram illustrating a PAM4 signal output from the light modulation module 100, that is, a value indicated by the output signal, and an electric signal applied to each light modulator.
- the electrical signal applied to the optical modulator 1, the optical modulator 2, and the optical modulator 3 is on. Accordingly, the continuous light input to the optical modulator 1 is output from the optical modulator 3 without being absorbed by any of the optical modulator 1, the optical modulator 2, and the optical modulator 3.
- the electrical signal applied to the optical modulator 1 is off, and the electrical signal applied to the optical modulator 2 and the optical modulator 3. Is on. Thereby, the continuous light input to the optical modulator 1 is absorbed by the optical modulator 1 and output from the optical modulator 3.
- FIG. 4 is a diagram showing an example of the voltage dependency of the extinction characteristic and the amplitude of each electric signal.
- the horizontal axis indicates the voltage applied to the optical modulator
- the vertical axis indicates the optical output after passing through the optical modulator.
- a value corresponding to each optical output that is, the intensity of the optical signal output from the optical modulation module 100 is shown beside the vertical axis in FIG.
- the extinction curve 200 is a curve indicating the voltage dependence of the extinction characteristics of the modulators used as the optical modulators 1 to 3.
- modulators having the same characteristics can be used as the optical modulators 1 to 3.
- FIG. 4 shows an example in which modulators having the same characteristics are used as the optical modulators 1 to 3.
- the optical path lengths in the optical modulators 1 to 3 are the same, and the band gap is also the same.
- the extinction curves 200 of the optical modulators 1 to 3 are the same.
- the amplitude # 1 indicates the amplitude of the OOK signal # 1
- the amplitude # 2 indicates the amplitude of the OOK signal # 2
- the amplitude # 3 indicates the amplitude of the OOK signal # 3.
- the amplitude is determined based on the extinction curve 200 shown in FIG. 4 so that the intensities of the four-level optical signals output from the optical modulator 3 are equally spaced.
- the difference between the level corresponding to 11 and the level corresponding to 10 is the same as the difference between the level corresponding to 10 and the level corresponding to 01, and the difference between the level corresponding to 01 and the level corresponding to 00 is the same.
- the amplitude of each electrical signal is determined.
- the four levels of light intensity output from the optical modulator 3 can be equally spaced.
- the optical modulators 1 to 3 have the same extinction curves, but the optical modulators 1 to 3 may not have the same extinction curves. Even when the extinction curves of the optical modulators 1 to 3 are not the same, considering the extinction curves, the amplitudes of the electric signals applied to the optical modulators 1 to 3 are set so that the four levels of light intensity are equally spaced. You may adjust to.
- FIG. 5 is an external view showing a mounting example of the light modulation module of the present embodiment.
- the light modulation module 100 is mounted on the semiconductor 5.
- a CW laser 6 is mounted on the semiconductor 5 as a light source together with the optical modulators 1 to 3. That is, in the example illustrated in FIG. 5, the light modulation module 100 includes a light source that generates continuous light.
- the CW laser 6 and the optical modulators 1 to 3 are formed side by side in series in the first direction 300 of the semiconductor 5.
- the electrode 8 is an electrode of the optical modulator 1
- the electrode 9 is an electrode of the optical modulator 2
- the electrode 10 is an electrode of the optical modulator 3
- the electrode 7 is an electrode of the CW laser 6. .
- a constant current for driving the CW laser 6 is applied to the CW laser 6 through the electrode 7.
- the CW laser 6 outputs continuous light having a constant light intensity.
- an OOK signal # 1, an OOK signal # 2, and an OOK signal # 3 are applied from an electric signal generation unit 4 not shown in FIG.
- the optical modulators 1 to 3 may be formed integrally with the CW laser 6 on the semiconductor 5. That is, the optical modulators 1 to 3 and the CW laser 6 may be integrated and integrated on the same chip.
- the arrangement order of the optical modulators 1 to 3 is not limited to the example shown in FIG. 5, and the same effect can be obtained even if the arrangement order is changed.
- the mounting example shown in FIG. 5 is an example, and it is only necessary to realize the operation as the light modulation module 100 of the above-described embodiment, and the shape of each part is not limited to the example of FIG.
- the optical modulators 1 to 3 are arranged in series and sequentially modulated, and an electric field is applied to each of the optical modulators 1 to 3 by the electric signal applied to each of the optical modulators 1 to 3. Whether or not to apply the voltage is controlled, and the voltage of the electric signal applied to the optical modulators 1 to 3 is determined so that the intensity of each of the four levels of the output optical signals is equally spaced. Thereby, the PAM4 signal can be generated without requiring complicated phase control. Further, since the electric signal generation unit 4 can be configured by a circuit that generates an OOK signal, it can be realized by a simple circuit.
- the Mach-Zehnder modulator in which the phase modulation section described in Patent Document 1 is divided into a plurality of parts, good characteristics cannot be obtained even when a difference in optical branching ratio and loss occurs. Therefore, it is necessary to suppress manufacturing variation.
- the optical modulation module of the present embodiment is not affected by the difference between the optical branching ratio and the loss, the demand for manufacturing variation is lower than that of the Mach-Zehnder modulator in which the phase modulation unit is divided into a plurality.
- a Mach-Zehnder modulator in which the phase modulation unit is divided into a plurality of parts requires a large number of terminals for phase control.
- the light modulation module of the present embodiment does not require many terminals for phase control.
- the light modulation module of the embodiment can be realized by a semiconductor having the same band structure, it is easy to manufacture.
- Embodiment 2 the light modulation module 100a according to the second embodiment of the present invention will be described. The description of the same configuration and operation as in the first embodiment will be omitted, and different points from the first embodiment will be described.
- FIG. 6 is an external view showing a mounting example of the light modulation module 100a of the present embodiment.
- the light modulation module 100a includes light modulators 1a to 3a instead of the light modulators 1 to 3 of the first embodiment.
- the electrode 8a is an electrode of the optical modulator 1a
- the electrode 9a is an electrode of the optical modulator 2a
- the electrode 10a is an electrode of the optical modulator 3a.
- the optical modulators 1a to 3a are, for example, EAMs, and the functions of the optical modulators 1a to 3a are the same as those of the optical modulators 1 to 3.
- the optical modulators 1a to 3a are formed of semiconductors having the same band structure.
- the optical modulators 1a to 3a are different from the optical modulators 1 to 3 of the first embodiment in that the optical path length in each of the optical modulators 1a to 3a is greater than the optical path length of the optical modulator 3a> the optical path of the optical modulator 2a. Length> the optical path length of the optical modulator 1a.
- the CW laser 6 and the optical modulators 1a to 3a are arranged in series in the first direction of the semiconductor 5, and the optical path length in the optical modulators 1a to 3a is approximately the optical modulator.
- the length in the first direction is 1a to 3a.
- the lengths of the optical modulators 1a to 3a in the first direction are shorter in the order of the optical modulator 3a, the optical modulator 2a, and the optical modulator 1a.
- the length of the optical modulators 1a to 3a in the first direction is referred to as the length of the optical modulators 1a to 3a.
- the electrical signal generator 4 of the present embodiment generates binary signals to be applied to the optical modulators 1a to 3a, respectively.
- the correspondence between the on / off state of each electrical signal generated by the electrical signal generation unit 4 of the present embodiment and the value indicated by the PAM4 signal output from the light modulation module 100a is the same as in FIG.
- the amplitudes of the voltages of the three electric signals generated by the electric signal generator 4 to be applied to the optical modulators 1a to 3a are the same.
- FIG. 7 is a diagram showing an extinction curve in the optical modulators 1a to 3a of the present embodiment and an amplitude of a voltage of an electric signal applied to the optical modulators 1a to 3a.
- the horizontal axis indicates the voltage applied to the optical modulator
- the vertical axis indicates the optical output after passing through the optical modulator, that is, the intensity of the optical signal.
- a value corresponding to the intensity of each optical output, that is, the optical signal output from the optical modulation module 100a, is shown on the side of the vertical axis in FIG.
- FIG. 7 shows the extinction curves of the optical modulators 1a to 3a.
- the lengths of the optical modulators 1a to 3a are different, the amount of light absorption in each of the optical modulators 1a to 3a with respect to the applied voltage is different. For this reason, in the present embodiment, as shown in FIG. 7, when the optical modulators 1a to 3a are driven with the same amplitude, the optical output after passing through the optical modulators 1a to 3a is Similarly to the PAM4 signal, the lengths of the optical modulators 1a to 3a are determined so that the levels are equally spaced. As a result, the light modulation module 100a of the present embodiment can generate the PAM4 signal as in the first embodiment while driving the light modulators 1a to 3a with electric signals having the same amplitude.
- the arrangement order of the optical modulators 1a to 3a is not limited to the example shown in FIG. 6, and the same effect can be obtained even if the arrangement order is changed.
- the absorption amount of the light modulators 1a to 3a is adjusted so that a desired PAM4 signal is obtained according to the length of the light modulators 1a to 3a. For this reason, the same effects as those of the first embodiment can be obtained, and the optical modulators 1a to 3a can be driven by electric signals having the same amplitude. Therefore, an integrated circuit (IC) that realizes the electric signal generator 4 is realized. Design of a circuit such as an integrated circuit becomes easy. Further, since electric signals having the same amplitude are input to the optical modulators 1a to 3a, it is not necessary to perform amplitude control for each electric signal, so that the time required for product testing can be reduced.
- IC integrated circuit
- the arrangement order of the optical modulators 1a to 3a is not limited to the example shown in FIG. 6, and the same effect can be obtained even if the arrangement order is changed. It should be noted that the amount of absorption is adjusted according to the length of two of the three optical modulators 1a to 3a using the same amplitude electrical signal as in the present embodiment, and the remaining one of the optical modulators. The optical output may be adjusted according to the amplitude of the electrical signal with an arbitrary length. Also in this case, since the two optical modulators can be driven by electric signals having the same amplitude, an effect of facilitating circuit design can be obtained.
- Embodiment 3 the light modulation module 100b according to the third embodiment of the present invention will be described.
- the description of the same configuration and operation as in the first embodiment will be omitted, and different points from the first embodiment will be described.
- FIG. 8 is an external view showing a mounting example of the light modulation module 100b of the present embodiment.
- the light modulation module 100b includes light modulators 1b to 3b instead of the light modulators 1 to 3 of the first embodiment.
- the electrode 8b is an electrode of the optical modulator 1b
- the electrode 9b is an electrode of the optical modulator 2b
- the electrode 10b is an electrode of the optical modulator 3b.
- the optical modulators 1b to 3b are, for example, EAM.
- the optical modulators 1b to 3b are different from the optical modulators 1 to 3 of the first embodiment in that the optical modulators 1b to 3b are formed of semiconductors having different band gaps.
- the band gaps of the optical modulators 1b to 3b are different, the light absorption amounts of the optical modulators 1b to 3b are different when the same electric field is applied.
- the lengths of the optical modulators 1b to 3b are the same.
- FIG. 9 is a diagram showing an extinction curve in the optical modulators 1b to 3b of the present embodiment and an amplitude of the voltage of the electric signal applied to the optical modulators 1b to 3b.
- the horizontal axis indicates the voltage applied to the optical modulator
- the vertical axis indicates the optical output after passing through the optical modulator, that is, the intensity of the optical signal.
- a value corresponding to the intensity of each optical output, that is, the optical signal output from the optical modulation module 100b, is shown beside the vertical axis in FIG.
- FIG. 9 shows the extinction curves of the optical modulators 1b to 3b.
- Amplitude # 1, amplitude # 2, and amplitude # 3 indicate the amplitudes of electrical signals applied to the optical modulator 1b, the optical modulator 2b, and the optical modulator 3b, respectively.
- the extinction curves of the optical modulator 1a and the optical modulator 2a are the same as the extinction curves of the optical modulator 3a. It becomes a shape that is stretched. Therefore, as in the case of the modulation between 11 and 10 in the optical modulator 1a, the optical signal intensity difference is smaller than that of the other optical modulators 2a and 3a, that is, shallow modulation is performed. The same amplitude as the modulation between 11 and 00 in the optical modulator 3a having a large difference in intensity is required.
- the extinction curves of the optical modulator 1b and the optical modulator 2b are as shown in FIG.
- the extinction curve is offset in the voltage direction. Therefore, when generating PAM4 signals at equal intervals, the amplitude of the electrical signal applied to the optical modulator 2b can be made smaller than the amplitude of the electrical signal applied to the optical modulator 3b, and applied to the optical modulator 1b.
- the amplitude of the electrical signal can be made smaller than the amplitude of the electrical signal applied to the optical modulator 2b.
- the same effects as in the first embodiment can be obtained, and the lengths of the optical modulators 1b to 3b are made the same, and the band gaps of the optical modulators 1b to 3b are made different.
- the amplitude of the electric signal can be suppressed. For this reason, the power consumption of the electric signal generation unit 4 can be reduced.
- the arrangement order of the optical modulators 1b to 3b is not limited to the example shown in FIG. 8, and the same effect can be obtained even if the arrangement order is changed.
- the amplitude of the electric signal applied to the optical modulators 1b to 3b is made different.
- the amplitude of the electric signal applied to the optical modulator 1b and the optical modulator 2b is changed to the optical modulator 3b.
- the electric signal to be applied may be the same.
- the optical output when the electric field is not applied even if the amplitude of the electric signal applied to the optical modulator 1b and the optical modulator 2b is extended to the low voltage side is the same.
- PAM4 signals at equal intervals can be generated.
- the power consumption is not reduced, but the circuit for realizing the electrical signal generation unit 4 can be simplified and the product test time can be shortened as in the second embodiment.
- the lengths of the optical modulators 1b to 3b may be different. Also in this case, it is possible to generate PAM4 signals at equal intervals by appropriately setting the amplitude.
- Embodiment 4 FIG. Next, an optical modulation module according to the fourth embodiment of the present invention will be described.
- the configuration of the light modulation module of the present embodiment is the same as that of the second embodiment.
- the description of the same configuration and operation as those of the second embodiment will be omitted, and differences from the second embodiment will be described.
- FIG. 10 is a diagram showing the extinction curves in the optical modulators 1a to 3a of the present embodiment and the amplitude of the voltage of the electric signal applied to the optical modulators 1a to 3a.
- the horizontal axis represents the voltage applied to the optical modulator
- the vertical axis represents the optical output after passing through the optical modulator, that is, the intensity of the optical signal.
- a value corresponding to the intensity of each optical output, that is, the optical signal output from the optical modulation module 100a, is shown on the side of the vertical axis in FIG.
- Amplitude # 1, amplitude # 2, and amplitude # 3 indicate the amplitudes of electrical signals applied to the optical modulator 1a, the optical modulator 2a, and the optical modulator 3a, respectively.
- the amplitudes of the electric signals applied to the optical modulators 1a to 3a are the same.
- the amplitudes of the electric signals applied to the optical modulators 1a to 3a are different. Specifically, as shown in FIG. 10, amplitude # 3> amplitude # 2> amplitude # 1.
- amplitude # 1 when OFF, that is, when the light is absorbed, the voltage value is the same as that in the example of FIG. 7, and when ON, that is, when the light is not absorbed, the amplitude # 2 and the voltage value are increased.
- the extinction ratios of the optical modulators 1a to 3a are different from each other.
- the extinction ratio is a ratio between the intensity of light output when an electric field is applied and the intensity of light output when an electric field is applied. If the amplitude # 2 and the amplitude # 1 are set so that the decrease in the light output does not affect the overall performance, there is no practical problem.
- the amplitudes of electric signals applied to the optical modulators 1a to 3a are suppressed as compared with the second embodiment using the optical modulators 1a to 3a of the second embodiment. For this reason, the same effects as those of the first embodiment can be obtained, and the power consumption can be suppressed as compared with the second embodiment.
- the arrangement order of the optical modulators 1a to 3a is not limited to the example shown in FIG. 6, and the same effect can be obtained even if the arrangement order is changed.
- Embodiment 5 the configuration example in which the CW laser 6 for generating continuous light and the modulator are integrated has been described.
- the light modulation module of the present embodiment deletes the CW laser 6 from the light modulation module described as the mounting example in the first embodiment.
- continuous light input from an external light source such as a CW laser is input to the light modulation module. That is, continuous light is input to the light modulation module from the outside.
- the external light source and the light modulation module are optically connected using an optical lens or by a Butt-Joint connection.
- the configuration and operation of this embodiment other than those described above are the same as those of the first embodiment.
- the CW laser 6 may be deleted from the light modulation module described as the mounting example in any one of Embodiments 2 to 4, and optically connected to an external light source. Also in this case, the configuration and operation of the light modulation module are the same as the operations of the corresponding embodiments except that a light source is provided outside and optically connected to the light source.
- the manufacture of the light modulation module is facilitated, and the defect rate at the time of manufacture can be reduced.
- FIG. 11 is a diagram illustrating a configuration example of the light modulation module 100c according to the present embodiment.
- FIG. 11 shows an example in which a ring resonator is used as a switch for switching the optical path.
- An optical modulation module 100c illustrated in FIG. 11 includes a ring resonator 21, a ring resonator 22, and a ring resonator 23, each of which is an optical modulator.
- the optical modulation module 100 c includes an input port 24, drop ports 25, 27, 29, through ports 26, 28, 30 and an output port 31. Electric signals output from the electric signal generator 4 (not shown in FIG. 11) are applied to the ring resonators 21 to 23 of the present embodiment.
- the ring resonators 21 to 23 are designed and controlled so that when the applied electrical signal is on, all the light input from the optical waveguide is transferred to the ring resonators 21 to 23 by optical coupling. . Further, when the applied electrical signal is OFF, the light input from the optical waveguide is designed and controlled so that part of it moves to the ring resonators 21 to 23 and the rest moves to the through port.
- the optical waveguide on the input side of the ring resonator 21 is the input port 24, the optical waveguide on the input side of the ring resonator 22 is the drop port 25, and the optical waveguide on the input side of the ring resonator 23 is the drop port. 27.
- the light transferred to the ring resonator 21 is transferred to the drop port 25
- the light transferred to the ring resonator 22 is transferred to the drop port 27
- the light transferred to the ring resonator 23 is transferred to the drop port 29. Be controlled.
- the ring resonator 21 performs 11/10 modulation
- the ring resonator 22 performs 11/01 modulation
- the ring resonator 23 performs 11/00 modulation.
- the electrical signal generator 4 applies an OOK signal to each of the ring resonators 21 to 23 that are optical modulators.
- Each of the ring resonators 21 to 23 resonates when an electrical signal indicating ON is input, and does not resonate when an electrical signal indicating OFF is input.
- the correspondence between the PAM4 signal output from the light modulation module 100c of the present embodiment, that is, the value indicated by the output signal, and the electric signal applied to each of the ring resonators 21 to 23 is the same as that shown in FIG. It is the same.
- the electrical signals applied to all the ring resonators 21 to 23 are on.
- the continuous light output from the light source is input to the ring resonator 21 through the input port 24, resonates at the ring resonator 21, and moves to the drop port 25.
- the light transferred to the drop port 25 is input to the ring resonator 22, resonates at the ring resonator 22, and moves to the drop port 27.
- the light transferred to the drop port 27 is input to the ring resonator 23, resonates at the ring resonator 23, and moves to the drop port 29.
- the light transferred to the drop port 29 is output from the output port 31 as a PAM4 signal.
- the electrical signal applied to the ring resonator 21 is off, and the electrical signal applied to the ring resonator 22 and the ring resonator 23. Is on. For this reason, a part of the continuous light input from the light source via the input port 24 remains in the through port 26 and the rest moves to the drop port 25. At this time, the ring resonator 21 is designed and controlled so that the intensity of light transferred to the drop port 25 becomes an intensity corresponding to a value of 10.
- the light that has moved to the drop port 25 resonates by the ring resonator 22 and moves to the drop port 27.
- the light transferred to the drop port 27 is input to the ring resonator 23, resonates at the ring resonator 23, and moves to the drop port 29.
- the light transferred to the drop port 29 is output from the output port 31 as a PAM4 signal.
- the PAM4 signal corresponding to each value is output by applying the electrical signal shown in FIG. Is done.
- the ring resonator 22 is designed and controlled so that the intensity of light transferred to the drop port 27 becomes a value of 01 when the ring resonator 21 is on and the ring resonator 22 is off.
- the ring resonator 23 is designed so that the intensity of light transferred to the drop port 29 becomes a value of 00 when the ring resonator 21 and the ring resonator 22 are on and the ring resonator 23 is off. Be controlled.
- a PAM4 signal is generated using an OOK signal as in the first embodiment, using a ring resonator as an optical modulator. Therefore, a multilevel modulation signal can be generated without requiring precise phase control.
- the configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.
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Abstract
A light modulation module (100) according to the present invention includes: a light modulator (1) that performs light-intensity modulation on continuous light; a light modulator (2) that performs light-intensity modulation on the light that has been subjected to light-intensity modulation by the light modulator (1); a light modulator (3) that performs light-intensity modulation on the light that has been subjected to light-intensity modulation by the light modulator (2); and an electrical-signal generating unit (4) that applies a first electrical signal, which is a binary electrical signal, to the light modulator (1), that applies a second electrical signal, which is a binary electrical signal, to the light modulator (2), and that applies a third electrical signal, which is a binary electrical signal, to the light modulator (3).
Description
本発明は、電気信号に応じた光変調信号を出力する光変調モジュールに関する。
The present invention relates to an optical modulation module that outputs an optical modulation signal corresponding to an electric signal.
400ギガビットイーサネット(登録商標)をはじめとした最新の光イーサネット規格では、従来のOOK(On-Off-Keying)方式ではなく、PAM4(4-level Pulse-Amplitude-Modulation)方式が用いられる。特許文献1では、多値変調を簡易な電気信号生成回路を用いて実現する手段として、位相変調部を複数に分割したマッハツェンダー変調器が提案されている。特許文献1で提案されている方式では、単純な回路で生成可能なOOK信号を複数用いてPAM4信号のような多値変調信号を生成可能である。
In the latest optical Ethernet standards such as 400 Gigabit Ethernet (registered trademark), the PAM4 (4-level Pulse-Amplitude-Modulation) method is used instead of the conventional OOK (On-Off-Keying) method. Patent Document 1 proposes a Mach-Zehnder modulator in which a phase modulation unit is divided into a plurality of means as means for realizing multilevel modulation using a simple electric signal generation circuit. In the system proposed in Patent Document 1, a multi-level modulation signal such as a PAM4 signal can be generated using a plurality of OOK signals that can be generated by a simple circuit.
特許文献1に記載のマッハツェンダー変調器では、両アームの位相を調整し、干渉させることで光を消光させている。このため、両アーム間の位相の差が生じた場合、十分に消光されず光変調信号の品質が低下する。したがって、光変調信号の品質の低下を防ぐには、両アームの位相は精密に制御される必要があり、装置が複雑化するという課題がある。
In the Mach-Zehnder modulator described in Patent Document 1, light is quenched by adjusting the phases of both arms and causing interference. For this reason, when a phase difference occurs between the arms, the light is not sufficiently quenched and the quality of the optical modulation signal is lowered. Therefore, in order to prevent the quality of the optical modulation signal from being deteriorated, the phases of both arms need to be precisely controlled, and there is a problem that the apparatus becomes complicated.
本発明は、上記に鑑みてなされたものであって、精密な位相の制御を必要とせずに多値変調信号を生成することができる光変調モジュールを得ることを目的とする。
The present invention has been made in view of the above, and an object of the present invention is to obtain an optical modulation module capable of generating a multi-level modulation signal without requiring precise phase control.
上述した課題を解決し、目的を達成するために、本発明にかかる光変調モジュールは、連続光に対して光強度変調を行う第1の光変調器と、第1の光変調器により光強度変調された光に対して光強度変調を行う第2の光変調器と、第2の光変調器により光強度変調された光に対して光強度変調を行う第3の光変調器と、を備える。また、光変調モジュールは、2値の電気信号である第1の電気信号を第1の光変調器に印加し、2値の電気信号である第2の電気信号を第2の光変調器に印加し、2値の電気信号である第3の電気信号を第3の光変調器に印加する信号生成部と、を備える。
In order to solve the above-described problems and achieve the object, an optical modulation module according to the present invention includes a first optical modulator that performs optical intensity modulation on continuous light, and an optical intensity by the first optical modulator. A second light modulator that performs light intensity modulation on the modulated light; and a third light modulator that performs light intensity modulation on the light that has been light intensity modulated by the second light modulator. Prepare. The light modulation module applies a first electric signal, which is a binary electric signal, to the first optical modulator, and applies a second electric signal, which is a binary electric signal, to the second optical modulator. And a signal generator that applies a third electrical signal, which is a binary electrical signal, to the third optical modulator.
本発明にかかる光変調モジュールは、精密な位相の制御を必要とせずに多値変調信号を生成することができるという効果を奏する。
The light modulation module according to the present invention produces an effect that a multi-level modulation signal can be generated without requiring precise phase control.
以下に、本発明の実施の形態にかかる光変調モジュールを図面に基づいて詳細に説明する。なお、この実施の形態によりこの発明が限定されるものではない。
Hereinafter, an optical modulation module according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.
実施の形態1.
図1は、本発明の実施の形態1にかかる光変調モジュールの構成例を示すブロック図である。図1に示すように、本実施の形態の光変調モジュール100は、光変調器1~3と、電気信号生成部4とを備える。光変調モジュール100は、与えられた信号すなわち情報に基づいて光変調信号を生成して出力する。光変調モジュール100は、例えば光通信装置において用いられる。光変調モジュール100が光通信装置において用いられる場合、上述した情報は、伝送する情報である。Embodiment 1 FIG.
FIG. 1 is a block diagram illustrating a configuration example of the light modulation module according to the first embodiment of the present invention. As shown in FIG. 1, anoptical modulation module 100 according to the present embodiment includes optical modulators 1 to 3 and an electric signal generation unit 4. The light modulation module 100 generates and outputs a light modulation signal based on a given signal, that is, information. The light modulation module 100 is used in, for example, an optical communication device. When the light modulation module 100 is used in an optical communication device, the information described above is information to be transmitted.
図1は、本発明の実施の形態1にかかる光変調モジュールの構成例を示すブロック図である。図1に示すように、本実施の形態の光変調モジュール100は、光変調器1~3と、電気信号生成部4とを備える。光変調モジュール100は、与えられた信号すなわち情報に基づいて光変調信号を生成して出力する。光変調モジュール100は、例えば光通信装置において用いられる。光変調モジュール100が光通信装置において用いられる場合、上述した情報は、伝送する情報である。
FIG. 1 is a block diagram illustrating a configuration example of the light modulation module according to the first embodiment of the present invention. As shown in FIG. 1, an
光変調器1は、図1では図示していない光源から出力された連続光(CW:Continuous Wave)を受け取り、連続光を強度変調し、強度変調後の信号である第1の光変調信号を出力する。なお、光源は光変調モジュール100内部に設けられていてもよいし光変調モジュール100の外部に設けられていてもよい。光変調器2は、光変調器1から出力された第1の光変調信号を受け取り、第1の光変調信号を強度変調し、強度変調後の信号である第2の光変調信号を出力する。光変調器3は、光変調器2から出力された第2の光変調信号を受け取り、第2の光変調信号を強度変調し、強度変調後の信号である第3の光変調信号を出力する。
The optical modulator 1 receives continuous light (CW: Continuous Wave) output from a light source (not shown in FIG. 1), modulates the intensity of the continuous light, and outputs a first optical modulation signal that is a signal after intensity modulation. Output. The light source may be provided inside the light modulation module 100 or may be provided outside the light modulation module 100. The optical modulator 2 receives the first optical modulation signal output from the optical modulator 1, intensity-modulates the first optical modulation signal, and outputs a second optical modulation signal that is a signal after intensity modulation. . The optical modulator 3 receives the second optical modulation signal output from the optical modulator 2, intensity-modulates the second optical modulation signal, and outputs a third optical modulation signal that is a signal after intensity modulation. .
すなわち、光変調器1は、連続光に対して光強度変調を行う第1の光変調器である。光変調器2は、光変調器1により光強度変調された光に対して光強度変調を行う第2の光変調器である。光変調器3は、光変調器2により光強度変調された光に対して光強度変調を行う第3の光変調器である。
That is, the optical modulator 1 is a first optical modulator that performs optical intensity modulation on continuous light. The light modulator 2 is a second light modulator that performs light intensity modulation on the light whose light intensity is modulated by the light modulator 1. The light modulator 3 is a third light modulator that performs light intensity modulation on the light whose light intensity is modulated by the light modulator 2.
光変調器1~3には、電気信号生成部4から出力される電気信号がそれぞれ印加される。光変調器1~3は、同一のバンド構造を持つ半導体により形成される。光変調器1~3は、半導体の電界吸収効果を利用したEAM(Electro-Absorption Modulator:電界吸収型光変調器)と呼ばれる光変調器、すなわち電界吸収型の光変調器である。半導体の電界吸収効果は、量子井戸構造が設けられた半導体に電界を印加すると、フランツケルディッシュ効果または量子シュタルク効果によりバンドギャップが変化し、光の吸収量が変化する現象である。この現象により、光変調器1~3は、電界を印加されたときは、電界が印加されていない場合に比べて、バンドギャップが縮小し光を吸収する。したがって、光変調器1~3は、印加される電界すなわち、電気信号生成部4から出力された電気信号の電圧に応じて光の吸収量を変化させ、出力する光信号の強度を変化させることができる。
The electrical signals output from the electrical signal generator 4 are applied to the optical modulators 1 to 3, respectively. The optical modulators 1 to 3 are formed of semiconductors having the same band structure. The optical modulators 1 to 3 are optical modulators called EAM (Electro-Absorption Modulator) using the semiconductor electroabsorption effect, that is, electroabsorption optical modulators. The electric field absorption effect of a semiconductor is a phenomenon in which, when an electric field is applied to a semiconductor provided with a quantum well structure, the band gap changes due to the Franz Kelish effect or the quantum Stark effect, and the amount of light absorption changes. Due to this phenomenon, the optical modulators 1 to 3 absorb light by reducing the band gap when an electric field is applied compared to when no electric field is applied. Therefore, the optical modulators 1 to 3 change the amount of light absorption in accordance with the applied electric field, that is, the voltage of the electric signal output from the electric signal generator 4, and change the intensity of the output optical signal. Can do.
電気信号生成部4は、光変調器1~3へ電界を印加するか否かを制御する電気信号を生成する。電気信号生成部4から光変調器1~3へそれぞれ印加される信号は、オンまたはオフを示す2値信号である。すなわち、電気信号生成部4は、2値の電気信号である第1の電気信号を第1の光変調器に印加し、2値の電気信号である第2の電気信号を第2の光変調器に印加し、2値の電気信号である第3の電気信号を第3の光変調器に印加する信号生成部である。電気信号の電圧値は、オフ(OFF)の場合には第1の電圧値であり、オン(ON)の場合には、第1の電圧値より低い第2の電圧値である。なお、各電気信号のオンまたはオフについては、以下、光変調モジュール100から出力されるPAM4信号のレベルの高い場合に相当する状態をオンとよび、PAM4信号のレベルの低い場合に相当する状態をオフと呼ぶ。したがって、本実施の形態で各光変調器へ印加される電圧は、電圧が高い方が光の吸収量が多いためレベルが低くなるためオフとなり、電圧が低い方が光の吸収量が少ないためレベルが高くなるためオンとなる。なお、このオンおよびオフの定義は一例であり、定義はオンとオフとで逆であってもよい。
The electric signal generator 4 generates an electric signal for controlling whether or not an electric field is applied to the optical modulators 1 to 3. The signals applied from the electric signal generator 4 to the optical modulators 1 to 3 are binary signals indicating ON or OFF. That is, the electrical signal generation unit 4 applies a first electrical signal that is a binary electrical signal to the first optical modulator, and a second electrical signal that is a binary electrical signal is subjected to the second optical modulation. And a signal generator that applies a third electrical signal, which is a binary electrical signal, to the third optical modulator. The voltage value of the electrical signal is a first voltage value when off (OFF), and a second voltage value lower than the first voltage value when on (ON). Regarding the on / off of each electric signal, hereinafter, the state corresponding to the case where the level of the PAM4 signal output from the light modulation module 100 is high is referred to as ON, and the state corresponding to the case where the level of the PAM4 signal is low. Call off. Therefore, the voltage applied to each optical modulator in the present embodiment is off because the higher the voltage, the lower the level because the amount of light absorption is larger, and the lower the voltage, the smaller the amount of light absorption. Turns on because the level is higher. This definition of on and off is an example, and the definition may be reversed between on and off.
電気信号がオフの場合、該電気信号が印加された各光変調器には電界が印加され、電気信号がオンの場合、該電気信号が印加された各光変調器には電界が印加されない。以下、第1の電圧値から第2の電圧値を減じた値を振幅と呼ぶ。第1の電圧値と第2の電圧値との間の中央の電圧をバイアス値と呼ぶ。電気信号生成部4は、与えられた信号の2ビットを1単位として、1単位の信号すなわち2ビットデータの値に応じて、光変調器1~3へ印加する電気信号を生成する。1単位の信号は、2進法であらわされる00,01,10,11の4値のいずれかの値である。
When the electrical signal is off, an electric field is applied to each optical modulator to which the electrical signal is applied. When the electrical signal is on, an electric field is not applied to each optical modulator to which the electrical signal is applied. Hereinafter, a value obtained by subtracting the second voltage value from the first voltage value is referred to as amplitude. A central voltage between the first voltage value and the second voltage value is referred to as a bias value. The electric signal generation unit 4 generates an electric signal to be applied to the optical modulators 1 to 3 according to the value of one unit signal, that is, two-bit data, with 2 bits of the given signal as one unit. One unit of signal is one of four values of 00, 01, 10, and 11 expressed in binary.
光変調器1~3の駆動回路である電気信号生成部4は、光変調器1~3へそれぞれ2値信号を出力するため、2値信号すなわちOOK信号を生成する単純な回路で実現することができる。
Since the electrical signal generator 4 which is a drive circuit for the optical modulators 1 to 3 outputs binary signals to the optical modulators 1 to 3, respectively, it is realized by a simple circuit that generates a binary signal, that is, an OOK signal. Can do.
図1に示すように、本実施の形態の光変調モジュール100では、各光変調器1~3はそれぞれが2値の変調を行うが、光変調器1~3を直列に並べて順次光変調を行うことで、最終的に光変調器3から出力される信号は4レベルの光変調信号であるPAM4信号となる。
As shown in FIG. 1, in the optical modulation module 100 of the present embodiment, each of the optical modulators 1 to 3 performs binary modulation, but the optical modulators 1 to 3 are arranged in series to sequentially perform optical modulation. As a result, the signal finally output from the optical modulator 3 becomes a PAM4 signal which is a four-level optical modulation signal.
本実施の形態の動作について説明する。図2は、本実施の形態の光変調モジュールにおける動作を説明するための図である。図2の上部には、電気信号生成部4から光変調器1に印加される第1の電気信号であるOOK信号#1と、電気信号生成部4から光変調器2に印加される第2の電気信号であるOOK信号#2と、電気信号生成部4から光変調器3に印加される第3の電気信号であるOOK信号#3とを模式的に示している。
The operation of this embodiment will be described. FIG. 2 is a diagram for explaining the operation of the light modulation module according to the present embodiment. In the upper part of FIG. 2, an OOK signal # 1 that is a first electric signal applied from the electric signal generator 4 to the optical modulator 1 and a second signal applied from the electric signal generator 4 to the optical modulator 2 are displayed. 3 schematically shows an OOK signal # 2 that is an electrical signal and an OOK signal # 3 that is a third electrical signal applied to the optical modulator 3 from the electrical signal generator 4.
図2に示すように、本実施の形態では、連続光が光変調器1、光変調器2および光変調器3のいずれでも吸収されずに、そのまま出力される場合の光強度を11の値に対応させる。そして、光変調器1で光が吸収され、光変調器2および光変調器3では吸収されずに光変調器3から出力される場合の光強度を10の値に対応させる。このように、光変調器1は、電界の印加の有無により、11の値と10の値との2値のいずれかに対応する光変調信号を生成するような光変調すなわち11/10変調を行う。
As shown in FIG. 2, in this embodiment, the light intensity when continuous light is output as it is without being absorbed by any of the optical modulator 1, the optical modulator 2, and the optical modulator 3 is a value of 11. To correspond to. Then, the light intensity when light is absorbed by the optical modulator 1 and output from the optical modulator 3 without being absorbed by the optical modulator 2 and the optical modulator 3 is made to correspond to a value of 10. As described above, the optical modulator 1 performs optical modulation, that is, 11/10 modulation that generates an optical modulation signal corresponding to one of the two values of 11 and 10 depending on whether or not an electric field is applied. Do.
また、光変調器2で光が吸収され、光変調器1および光変調器3では光が吸収されずに光変調器3から出力される場合の光強度を01の値に対応させる。図2に示すように、光変調器2における光の吸収量は光変調器1における光の吸収量より多い。すなわち、OOK信号#2の振幅は、OOK信号#1の振幅より大きい。このように、光変調器2は、電界の印加の有無により、11の値と01の値との2値のいずれかに対応する光変調信号を生成するような光変調すなわち11/01変調を行う。
Also, the light intensity when light is absorbed by the light modulator 2 and output from the light modulator 3 without being absorbed by the light modulator 1 and the light modulator 3 is made to correspond to a value of 01. As shown in FIG. 2, the light absorption amount in the optical modulator 2 is larger than the light absorption amount in the optical modulator 1. That is, the amplitude of the OOK signal # 2 is larger than the amplitude of the OOK signal # 1. In this way, the optical modulator 2 performs optical modulation, that is, 11/01 modulation, which generates an optical modulation signal corresponding to one of the two values of 11 and 01 depending on whether or not an electric field is applied. Do.
また、光変調器3で光が吸収され、光変調器1および光変調器2では吸収されずに光変調器3から出力される場合の光強度を00の値に対応させる。図2に示すように、光変調器3における光の吸収量は光変調器2における光の吸収量より多い。すなわち、OOK信号#3の振幅は、OOK信号#2の振幅より大きい。このように、光変調器3は、電界の印加の有無により、11の値と00の値との2値のいずれかに対応する光変調信号を生成するような光変調すなわち11/00変調を行う。
Also, the light intensity when light is absorbed by the optical modulator 3 and output from the optical modulator 3 without being absorbed by the optical modulator 1 and the optical modulator 2 is made to correspond to a value of 00. As shown in FIG. 2, the light absorption amount in the optical modulator 3 is larger than the light absorption amount in the optical modulator 2. That is, the amplitude of the OOK signal # 3 is larger than the amplitude of the OOK signal # 2. As described above, the optical modulator 3 performs optical modulation, that is, 11/00 modulation that generates an optical modulation signal corresponding to one of the two values of 11 and 00 depending on whether or not an electric field is applied. Do.
以上のように、OOK信号#1~OOK信号#3の振幅を異ならせて、2ビットの情報の値に応じてOOK信号#1~OOK信号#3のオンまたはオフを決定することにより、光変調モジュール100は、PAM4信号を出力することができる。図3は、光変調モジュール100から出力されるPAM4信号すなわち出力信号の示す値と、各光変調器に印加する電気信号とを示す図である。
As described above, by varying the amplitudes of the OOK signals # 1 to # 3 and determining whether the OOK signals # 1 to # 3 are turned on or off according to the 2-bit information value, The modulation module 100 can output a PAM4 signal. FIG. 3 is a diagram illustrating a PAM4 signal output from the light modulation module 100, that is, a value indicated by the output signal, and an electric signal applied to each light modulator.
図3に示すように、11に対応する出力信号を出力する場合には、光変調器1、光変調器2および光変調器3に印加される電気信号はオンである。これにより、光変調器1へ入力された連続光は、光変調器1、光変調器2および光変調器3のいずれにおいても吸収されずに光変調器3から出力される。図3に示すように、10に対応する出力信号を出力する場合には、光変調器1に印加される電気信号はオフであり、光変調器2および光変調器3に印加される電気信号はオンである。これにより、光変調器1へ入力された連続光は、光変調器1で吸収されて光変調器3から出力される。
As shown in FIG. 3, when an output signal corresponding to 11 is output, the electrical signal applied to the optical modulator 1, the optical modulator 2, and the optical modulator 3 is on. Accordingly, the continuous light input to the optical modulator 1 is output from the optical modulator 3 without being absorbed by any of the optical modulator 1, the optical modulator 2, and the optical modulator 3. As shown in FIG. 3, when an output signal corresponding to 10 is output, the electrical signal applied to the optical modulator 1 is off, and the electrical signal applied to the optical modulator 2 and the optical modulator 3. Is on. Thereby, the continuous light input to the optical modulator 1 is absorbed by the optical modulator 1 and output from the optical modulator 3.
図3に示すように、01に対応する出力信号を出力する場合には、光変調器2に印加される電気信号はオフであり、光変調器1および光変調器3に印加される電気信号はオンである。これにより、光変調器1へ入力された連続光は、光変調器2で吸収されて光変調器3から出力される。図3に示すように、00に対応する出力信号を出力する場合には、光変調器3に印加される電気信号はオフであり、光変調器1および光変調器2に印加される電気信号はオンである。これにより、光変調器1へ入力された連続光は、光変調器3で吸収されて光変調器3から出力される。
As shown in FIG. 3, when an output signal corresponding to 01 is output, the electrical signal applied to the optical modulator 2 is off, and the electrical signal applied to the optical modulator 1 and the optical modulator 3. Is on. Thereby, the continuous light input to the optical modulator 1 is absorbed by the optical modulator 2 and output from the optical modulator 3. As shown in FIG. 3, when outputting an output signal corresponding to 00, the electrical signal applied to the optical modulator 3 is off, and the electrical signal applied to the optical modulator 1 and the optical modulator 2. Is on. Thereby, the continuous light input to the optical modulator 1 is absorbed by the optical modulator 3 and output from the optical modulator 3.
図4は、消光特性の電圧依存性と各電気信号の振幅の一例を示す図である。図4では、横軸には光変調器に印加される電圧を示し、縦軸は光変調器通過後の光出力を示している。図4の縦軸の横には、各光出力すなわち光変調モジュール100から出力される光信号の強度に対応する値が示されている。消光カーブ200は、光変調器1~3として用いられる変調器の消光特性の電圧依存性を示す曲線である。本実施の形態では、光変調器1~3としては、同じ特性の変調器を用いることができる。図4では、光変調器1~3としては、同じ特性の変調器を用いた例を示している。この場合、光変調器1~3における光路長は同一であり、バンドギャップも同一である。光変調器1~3の消光カーブ200は同一である。振幅#1はOOK信号#1の振幅を示し、振幅#2はOOK信号#2の振幅を示し、振幅#3はOOK信号#3の振幅を示す。PAM4信号では、光強度は等間隔とする必要がある。このため、図4に示す消光カーブ200に基づいて、光変調器3から出力される4レベルの各光信号の強度が等間隔となるように、振幅を決定する。すなわち、11に対応するレベルと10に対応するレベルとの差、10に対応するレベルと01に対応するレベルとの差、および01に対応するレベルと00に対応するレベルとの差が同一となるように、各電気信号の振幅を決定する。これにより、光変調器3から出力される4レベルの光強度を等間隔とすることができる。
FIG. 4 is a diagram showing an example of the voltage dependency of the extinction characteristic and the amplitude of each electric signal. In FIG. 4, the horizontal axis indicates the voltage applied to the optical modulator, and the vertical axis indicates the optical output after passing through the optical modulator. A value corresponding to each optical output, that is, the intensity of the optical signal output from the optical modulation module 100 is shown beside the vertical axis in FIG. The extinction curve 200 is a curve indicating the voltage dependence of the extinction characteristics of the modulators used as the optical modulators 1 to 3. In the present embodiment, as the optical modulators 1 to 3, modulators having the same characteristics can be used. FIG. 4 shows an example in which modulators having the same characteristics are used as the optical modulators 1 to 3. In this case, the optical path lengths in the optical modulators 1 to 3 are the same, and the band gap is also the same. The extinction curves 200 of the optical modulators 1 to 3 are the same. The amplitude # 1 indicates the amplitude of the OOK signal # 1, the amplitude # 2 indicates the amplitude of the OOK signal # 2, and the amplitude # 3 indicates the amplitude of the OOK signal # 3. In the PAM4 signal, the light intensity needs to be equally spaced. For this reason, the amplitude is determined based on the extinction curve 200 shown in FIG. 4 so that the intensities of the four-level optical signals output from the optical modulator 3 are equally spaced. That is, the difference between the level corresponding to 11 and the level corresponding to 10 is the same as the difference between the level corresponding to 10 and the level corresponding to 01, and the difference between the level corresponding to 01 and the level corresponding to 00 is the same. Thus, the amplitude of each electrical signal is determined. Thereby, the four levels of light intensity output from the optical modulator 3 can be equally spaced.
なお、図4に示した上述した例では、光変調器1~3の消光カーブが同一であるとして説明したが、光変調器1~3の消光カーブは完全に同一でなくてもよい。光変調器1~3の消光カーブが同一でない場合も、それぞれの消光カーブを考慮して、光変調器1~3にそれぞれ印加する電気信号の振幅を4レベルの光強度が等間隔となるように調整すればよい。
In the above-described example shown in FIG. 4, it has been described that the optical modulators 1 to 3 have the same extinction curves, but the optical modulators 1 to 3 may not have the same extinction curves. Even when the extinction curves of the optical modulators 1 to 3 are not the same, considering the extinction curves, the amplitudes of the electric signals applied to the optical modulators 1 to 3 are set so that the four levels of light intensity are equally spaced. You may adjust to.
図5は、本実施の形態の光変調モジュールの実装例を示す外観図である。図5に示した例では、光変調モジュール100は、半導体5上に実装される。また、半導体5には、光変調器1~3とともに光源としてCWレーザ6も実装される。すなわち、図5に示した例では、光変調モジュール100は、連続光を生成する光源を備える。CWレーザ6および光変調器1~3は、半導体5の第1の方向300に直列に並んで形成される。電極8は、光変調器1の電極であり、電極9は、光変調器2の電極であり、電極10は、光変調器3の電極であり、電極7は、CWレーザ6の電極である。CWレーザ6には、電極7を介してCWレーザ6の駆動用の一定の電流が印加される。これにより、CWレーザ6からは、一定の光強度の連続光が出力される。電極8、電極9、電極10からは、図5では図示していない電気信号生成部4からそれぞれOOK信号#1、OOK信号#2、OOK信号#3が印加される。上述した図5に示すように、光変調器1~3は、半導体5上にCWレーザ6と一体化されて形成されてもよい。すなわち、光変調器1~3とCWレーザ6とは同一チップに一体化されて集積されてもよい。なお、光変調器1~3の並び順は図5に示した例に限定されず、並び順を変更しても同様の効果が得られる。図5に示した実装例は一例であり、上述した本実施の形態の光変調モジュール100としての動作を実現可能であればよく、各部の形状は図5の例に限定されない。
FIG. 5 is an external view showing a mounting example of the light modulation module of the present embodiment. In the example shown in FIG. 5, the light modulation module 100 is mounted on the semiconductor 5. Further, a CW laser 6 is mounted on the semiconductor 5 as a light source together with the optical modulators 1 to 3. That is, in the example illustrated in FIG. 5, the light modulation module 100 includes a light source that generates continuous light. The CW laser 6 and the optical modulators 1 to 3 are formed side by side in series in the first direction 300 of the semiconductor 5. The electrode 8 is an electrode of the optical modulator 1, the electrode 9 is an electrode of the optical modulator 2, the electrode 10 is an electrode of the optical modulator 3, and the electrode 7 is an electrode of the CW laser 6. . A constant current for driving the CW laser 6 is applied to the CW laser 6 through the electrode 7. As a result, the CW laser 6 outputs continuous light having a constant light intensity. From the electrode 8, the electrode 9, and the electrode 10, an OOK signal # 1, an OOK signal # 2, and an OOK signal # 3 are applied from an electric signal generation unit 4 not shown in FIG. As shown in FIG. 5 described above, the optical modulators 1 to 3 may be formed integrally with the CW laser 6 on the semiconductor 5. That is, the optical modulators 1 to 3 and the CW laser 6 may be integrated and integrated on the same chip. The arrangement order of the optical modulators 1 to 3 is not limited to the example shown in FIG. 5, and the same effect can be obtained even if the arrangement order is changed. The mounting example shown in FIG. 5 is an example, and it is only necessary to realize the operation as the light modulation module 100 of the above-described embodiment, and the shape of each part is not limited to the example of FIG.
以上のように、本実施の形態では、光変調器1~3を直列に並べて順次光変調を行い、各光変調器1~3へ印加する電気信号により各光変調器1~3に電界を印加するか否かを制御し、光変調器1~3に印加する電気信号の電圧を出力される4レベルの各光信号の強度が等間隔となるように決定するようにした。これにより、複雑な位相制御を必要とせずに、PAM4信号を生成することができる。また、電気信号生成部4は、OOK信号を生成する回路で構成できるため、簡単な回路で実現できる。
As described above, in this embodiment, the optical modulators 1 to 3 are arranged in series and sequentially modulated, and an electric field is applied to each of the optical modulators 1 to 3 by the electric signal applied to each of the optical modulators 1 to 3. Whether or not to apply the voltage is controlled, and the voltage of the electric signal applied to the optical modulators 1 to 3 is determined so that the intensity of each of the four levels of the output optical signals is equally spaced. Thereby, the PAM4 signal can be generated without requiring complicated phase control. Further, since the electric signal generation unit 4 can be configured by a circuit that generates an OOK signal, it can be realized by a simple circuit.
また、特許文献1に記載されている位相変調部を複数に分割したマッハツェンダー変調器では、光分岐比率および損失の差が生じた場合にも、良好な特性が得られない。したがって、製造バラつきを抑える必要がある。これに対し、本実施の形態の光変調モジュールは、光分岐比率および損失の差の影響を受けないため、製造バラつきに対する要求は位相変調部を複数に分割したマッハツェンダー変調器より低い。また、位相変調部を複数に分割したマッハツェンダー変調器では、位相制御のために多くの端子数を必要とする。これに対し、本実施の形態の光変調モジュールは、位相制御のために多くの端子も必要としない。また、実施の形態の光変調モジュールは、同一のバンド構造を持つ半導体により実現できるため、製造が容易である。
Further, in the Mach-Zehnder modulator in which the phase modulation section described in Patent Document 1 is divided into a plurality of parts, good characteristics cannot be obtained even when a difference in optical branching ratio and loss occurs. Therefore, it is necessary to suppress manufacturing variation. On the other hand, since the optical modulation module of the present embodiment is not affected by the difference between the optical branching ratio and the loss, the demand for manufacturing variation is lower than that of the Mach-Zehnder modulator in which the phase modulation unit is divided into a plurality. Further, a Mach-Zehnder modulator in which the phase modulation unit is divided into a plurality of parts requires a large number of terminals for phase control. On the other hand, the light modulation module of the present embodiment does not require many terminals for phase control. In addition, since the light modulation module of the embodiment can be realized by a semiconductor having the same band structure, it is easy to manufacture.
実施の形態2.
次に、本発明にかかる実施の形態2の光変調モジュール100aについて説明する。実施の形態1と同様の構成および動作については説明を省略し、実施の形態1と異なる点を説明する。Embodiment 2. FIG.
Next, thelight modulation module 100a according to the second embodiment of the present invention will be described. The description of the same configuration and operation as in the first embodiment will be omitted, and different points from the first embodiment will be described.
次に、本発明にかかる実施の形態2の光変調モジュール100aについて説明する。実施の形態1と同様の構成および動作については説明を省略し、実施の形態1と異なる点を説明する。
Next, the
図6は、本実施の形態の光変調モジュール100aの実装例を示す外観図である。光変調モジュール100aは、実施の形態1の光変調器1~3の代わりに光変調器1a~3aを備える。電極8aは、光変調器1aの電極であり、電極9aは、光変調器2aの電極であり、電極10aは、光変調器3aの電極である。光変調器1a~3aは、例えばEAMであり、光変調器1a~3aのそれぞれの機能は光変調器1~3と同様である。光変調器1a~3aは、同一のバンド構造を持つ半導体で形成される。光変調器1a~3aが、実施の形態1の光変調器1~3と異なる点は、各光変調器1a~3aにおける光路長が、光変調器3aの光路長>光変調器2aの光路長>光変調器1aの光路長となっている点である。図6に示した実装例では、CWレーザ6および光変調器1a~3aは、半導体5の第1の方向に直列に並んでおり、光変調器1a~3a内の光路長は概ね光変調器1a~3aの第1の方向の長さとなる。したがって、光変調器1a~3aの第1の方向の長さは、光変調器3a、光変調器2a、光変調器1aの順に短くなっている。以下、光変調器1a~3aの第1の方向の長さを光変調器1a~3aの長さという。このように、光変調器1a~3aに同一のバンド構造を持つ半導体を用いて、光変調器1a~3a内の光路長を異ならせることで、光変調器1a~3aでは、同一の電界が印加された場合の光の吸収量が異なることになる。
FIG. 6 is an external view showing a mounting example of the light modulation module 100a of the present embodiment. The light modulation module 100a includes light modulators 1a to 3a instead of the light modulators 1 to 3 of the first embodiment. The electrode 8a is an electrode of the optical modulator 1a, the electrode 9a is an electrode of the optical modulator 2a, and the electrode 10a is an electrode of the optical modulator 3a. The optical modulators 1a to 3a are, for example, EAMs, and the functions of the optical modulators 1a to 3a are the same as those of the optical modulators 1 to 3. The optical modulators 1a to 3a are formed of semiconductors having the same band structure. The optical modulators 1a to 3a are different from the optical modulators 1 to 3 of the first embodiment in that the optical path length in each of the optical modulators 1a to 3a is greater than the optical path length of the optical modulator 3a> the optical path of the optical modulator 2a. Length> the optical path length of the optical modulator 1a. In the mounting example shown in FIG. 6, the CW laser 6 and the optical modulators 1a to 3a are arranged in series in the first direction of the semiconductor 5, and the optical path length in the optical modulators 1a to 3a is approximately the optical modulator. The length in the first direction is 1a to 3a. Accordingly, the lengths of the optical modulators 1a to 3a in the first direction are shorter in the order of the optical modulator 3a, the optical modulator 2a, and the optical modulator 1a. Hereinafter, the length of the optical modulators 1a to 3a in the first direction is referred to as the length of the optical modulators 1a to 3a. In this way, by using semiconductors having the same band structure for the optical modulators 1a to 3a and making the optical path lengths in the optical modulators 1a to 3a different, the same electric field is generated in the optical modulators 1a to 3a. The amount of light absorption when applied is different.
本実施の形態の電気信号生成部4は、光変調器1a~3aへそれぞれ印加する2値信号を生成する。本実施の形態の電気信号生成部4が生成する各電気信号のオンまたはオフの状態と、光変調モジュール100aから出力されるPAM4信号の示す値との対応は、図3と同様である。ただし、本実施の形態では、実施の形態1と異なり、電気信号生成部4が光変調器1a~3aへ印加するために生成する3つの電気信号の電圧の振幅は同一である。
The electrical signal generator 4 of the present embodiment generates binary signals to be applied to the optical modulators 1a to 3a, respectively. The correspondence between the on / off state of each electrical signal generated by the electrical signal generation unit 4 of the present embodiment and the value indicated by the PAM4 signal output from the light modulation module 100a is the same as in FIG. However, in the present embodiment, unlike the first embodiment, the amplitudes of the voltages of the three electric signals generated by the electric signal generator 4 to be applied to the optical modulators 1a to 3a are the same.
図7は、本実施の形態の光変調器1a~3aにおける消光カーブと光変調器1a~3aに印加される電気信号の電圧の振幅とを示す図である。図7では、横軸には光変調器に印加される電圧を示し、縦軸は光変調器通過後の光出力すなわち光信号の強度を示している。図7の縦軸の横には、各光出力すなわち光変調モジュール100aから出力される光信号の強度に対応する値が示されている。図7では、光変調器1a~3aのそれぞれの消光カーブを図示している。光変調器1a~3aの長さが異なると、印加された電圧に対する各光変調器1a~3aにおける光の吸収量が異なる。このため、本実施の形態では、図7に示すように、光変調器1a~3aを同一振幅で駆動した場合の、光変調器1a~3aを通過した後の光出力が、実施の形態1のPAM4信号と同様にレベル間が等間隔となるように、光変調器1a~3aの長さが決定される。これにより、本実施の形態の光変調モジュール100aは、光変調器1a~3aを同一振幅の電気信号で駆動しつつ、実施の形態1と同様に、PAM4信号を生成することができる。なお、光変調器1a~3aの並び順は図6に示した例に限定されず、並び順を変更しても同様の効果が得られる。
FIG. 7 is a diagram showing an extinction curve in the optical modulators 1a to 3a of the present embodiment and an amplitude of a voltage of an electric signal applied to the optical modulators 1a to 3a. In FIG. 7, the horizontal axis indicates the voltage applied to the optical modulator, and the vertical axis indicates the optical output after passing through the optical modulator, that is, the intensity of the optical signal. A value corresponding to the intensity of each optical output, that is, the optical signal output from the optical modulation module 100a, is shown on the side of the vertical axis in FIG. FIG. 7 shows the extinction curves of the optical modulators 1a to 3a. When the lengths of the optical modulators 1a to 3a are different, the amount of light absorption in each of the optical modulators 1a to 3a with respect to the applied voltage is different. For this reason, in the present embodiment, as shown in FIG. 7, when the optical modulators 1a to 3a are driven with the same amplitude, the optical output after passing through the optical modulators 1a to 3a is Similarly to the PAM4 signal, the lengths of the optical modulators 1a to 3a are determined so that the levels are equally spaced. As a result, the light modulation module 100a of the present embodiment can generate the PAM4 signal as in the first embodiment while driving the light modulators 1a to 3a with electric signals having the same amplitude. The arrangement order of the optical modulators 1a to 3a is not limited to the example shown in FIG. 6, and the same effect can be obtained even if the arrangement order is changed.
本実施の形態の光変調モジュール100aによれば、光変調器1a~3aの長さにより、所望のPAM4信号が得られるように光変調器1a~3aの吸収量を調整するようにした。このため、実施の形態1と同様の効果が得られるとともに、光変調器1a~3aを同じ振幅の電気信号で駆動することができるため、電気信号生成部4を実現する、IC(Integrated Circuit:集積回路)等の回路の設計が容易となる。また、光変調器1a~3aに同じ振幅の電気信号を入力することから、各々の電気信号に関して振幅制御を行う必要が無いため、製品試験の時間短縮が可能である。なお、光変調器1a~3aの並び順は図6に示した例に限定されず、並び順を変更しても同様の効果が得られる。なお、3個の光変調器1a~3aのうち2個に対して本実施形態と同様に同一の振幅の電気信号を用いて長さにより吸収量を調節し、残りの1つの光変調器の長さは任意として、電気信号の振幅により光出力を調整するようにしてもよい。この場合も、2つの光変調器については同一の振幅の電気信号で駆動できるため、回路の設計が容易となる効果は得られる。
According to the light modulation module 100a of the present embodiment, the absorption amount of the light modulators 1a to 3a is adjusted so that a desired PAM4 signal is obtained according to the length of the light modulators 1a to 3a. For this reason, the same effects as those of the first embodiment can be obtained, and the optical modulators 1a to 3a can be driven by electric signals having the same amplitude. Therefore, an integrated circuit (IC) that realizes the electric signal generator 4 is realized. Design of a circuit such as an integrated circuit becomes easy. Further, since electric signals having the same amplitude are input to the optical modulators 1a to 3a, it is not necessary to perform amplitude control for each electric signal, so that the time required for product testing can be reduced. The arrangement order of the optical modulators 1a to 3a is not limited to the example shown in FIG. 6, and the same effect can be obtained even if the arrangement order is changed. It should be noted that the amount of absorption is adjusted according to the length of two of the three optical modulators 1a to 3a using the same amplitude electrical signal as in the present embodiment, and the remaining one of the optical modulators. The optical output may be adjusted according to the amplitude of the electrical signal with an arbitrary length. Also in this case, since the two optical modulators can be driven by electric signals having the same amplitude, an effect of facilitating circuit design can be obtained.
実施の形態3.
次に、本発明にかかる実施の形態3の光変調モジュール100bについて説明する。実施の形態1と同様の構成および動作については説明を省略し、実施の形態1と異なる点を説明する。Embodiment 3 FIG.
Next, thelight modulation module 100b according to the third embodiment of the present invention will be described. The description of the same configuration and operation as in the first embodiment will be omitted, and different points from the first embodiment will be described.
次に、本発明にかかる実施の形態3の光変調モジュール100bについて説明する。実施の形態1と同様の構成および動作については説明を省略し、実施の形態1と異なる点を説明する。
Next, the
図8は、本実施の形態の光変調モジュール100bの実装例を示す外観図である。光変調モジュール100bは、実施の形態1の光変調器1~3の代わりに光変調器1b~3bを備える。電極8bは、光変調器1bの電極であり、電極9bは、光変調器2bの電極であり、電極10bは、光変調器3bの電極である。光変調器1b~3bは、例えばEAMである。光変調器1b~3bが、実施の形態1の光変調器1~3と異なる点は、光変調器1b~3bが、バンドギャップが異なる半導体で形成される点である。詳細には、光変調器1bのバンドギャップ>光変調器2bのバンドギャップ>光変調器3bのバンドギャップである。本実施の形態では、光変調器1b~3bのバンドギャップが異なるため、同一の電界が印加された場合の光変調器1b~3bの光の吸収量が異なることになる。光変調器1b~3bの長さは、同一である。
FIG. 8 is an external view showing a mounting example of the light modulation module 100b of the present embodiment. The light modulation module 100b includes light modulators 1b to 3b instead of the light modulators 1 to 3 of the first embodiment. The electrode 8b is an electrode of the optical modulator 1b, the electrode 9b is an electrode of the optical modulator 2b, and the electrode 10b is an electrode of the optical modulator 3b. The optical modulators 1b to 3b are, for example, EAM. The optical modulators 1b to 3b are different from the optical modulators 1 to 3 of the first embodiment in that the optical modulators 1b to 3b are formed of semiconductors having different band gaps. Specifically, the band gap of the optical modulator 1b> the band gap of the optical modulator 2b> the band gap of the optical modulator 3b. In the present embodiment, since the band gaps of the optical modulators 1b to 3b are different, the light absorption amounts of the optical modulators 1b to 3b are different when the same electric field is applied. The lengths of the optical modulators 1b to 3b are the same.
図9は、本実施の形態の光変調器1b~3bにおける消光カーブと光変調器1b~3bに印加される電気信号の電圧の振幅とを示す図である。図9では、横軸には光変調器に印加される電圧を示し、縦軸は光変調器通過後の光出力すなわち光信号の強度を示している。図9の縦軸の横には、各光出力すなわち光変調モジュール100bから出力される光信号の強度に対応する値が示されている。図9では、光変調器1b~3bのそれぞれの消光カーブを図示している。振幅#1、振幅#2、振幅#3は、光変調器1b、光変調器2b、光変調器3bにそれぞれ印加される電気信号の振幅を示す。
FIG. 9 is a diagram showing an extinction curve in the optical modulators 1b to 3b of the present embodiment and an amplitude of the voltage of the electric signal applied to the optical modulators 1b to 3b. In FIG. 9, the horizontal axis indicates the voltage applied to the optical modulator, and the vertical axis indicates the optical output after passing through the optical modulator, that is, the intensity of the optical signal. A value corresponding to the intensity of each optical output, that is, the optical signal output from the optical modulation module 100b, is shown beside the vertical axis in FIG. FIG. 9 shows the extinction curves of the optical modulators 1b to 3b. Amplitude # 1, amplitude # 2, and amplitude # 3 indicate the amplitudes of electrical signals applied to the optical modulator 1b, the optical modulator 2b, and the optical modulator 3b, respectively.
各光変調器の長さが異なる実施の形態2の場合には、図7に示した通り、光変調器1aおよび光変調器2aの消光カーブは、光変調器3aの消光カーブが電圧方向に引きのばされたような形状となる。したがって、光変調器1aにおける11と10との間の変調のように、光信号の強度の差が他の光変調器2a,3aに比べて少ない変調すなわち浅い変調を行うにも、光信号の強度の差の大きい光変調器3aにおける11と00との間の変調と同じ振幅が必要である。これに対し、本実施の形態では、光変調器1b~3bは長さが同一であるため、図9に示すように、光変調器1bおよび光変調器2bの消光カーブは、光変調器3bの消光カーブを電圧方向にオフセットさせたものとなる。したがって、等間隔なPAM4信号を生成する際に、光変調器2bに印加する電気信号の振幅を光変調器3bに印加する電気信号の振幅より小さくすることができ、光変調器1bに印加する電気信号の振幅を光変調器2bに印加する電気信号の振幅より小さくすることができる。
In the case of Embodiment 2 in which the lengths of the respective optical modulators are different, as shown in FIG. 7, the extinction curves of the optical modulator 1a and the optical modulator 2a are the same as the extinction curves of the optical modulator 3a. It becomes a shape that is stretched. Therefore, as in the case of the modulation between 11 and 10 in the optical modulator 1a, the optical signal intensity difference is smaller than that of the other optical modulators 2a and 3a, that is, shallow modulation is performed. The same amplitude as the modulation between 11 and 00 in the optical modulator 3a having a large difference in intensity is required. On the other hand, in the present embodiment, since the optical modulators 1b to 3b have the same length, the extinction curves of the optical modulator 1b and the optical modulator 2b are as shown in FIG. The extinction curve is offset in the voltage direction. Therefore, when generating PAM4 signals at equal intervals, the amplitude of the electrical signal applied to the optical modulator 2b can be made smaller than the amplitude of the electrical signal applied to the optical modulator 3b, and applied to the optical modulator 1b. The amplitude of the electrical signal can be made smaller than the amplitude of the electrical signal applied to the optical modulator 2b.
本実施の形態では、実施の形態1と同様の効果が得られるとともに、光変調器1b~3bの長さを同一とするとともに光変調器1b~3bのバンドギャップを異ならせることで、実施の形態2に比べて電気信号の振幅を抑えることができる。このため、電気信号生成部4の消費電力を低減させることができる。なお、光変調器1b~3bの並び順は図8に示した例に限定されず、並び順を変更しても同様の効果が得られる。
In the present embodiment, the same effects as in the first embodiment can be obtained, and the lengths of the optical modulators 1b to 3b are made the same, and the band gaps of the optical modulators 1b to 3b are made different. Compared with the second embodiment, the amplitude of the electric signal can be suppressed. For this reason, the power consumption of the electric signal generation unit 4 can be reduced. The arrangement order of the optical modulators 1b to 3b is not limited to the example shown in FIG. 8, and the same effect can be obtained even if the arrangement order is changed.
また、上述した例では、光変調器1b~3bに印加する電気信号の振幅を異ならせるようにしたが、光変調器1bおよび光変調器2bに印加する電気信号の振幅を光変調器3bに印加する電気信号と同一としてもよい。図9に示すように、光変調器1bおよび光変調器2bに印加する電気信号の振幅を電圧の低い側に延長しても電界が印加されない場合の光出力は同じであるため、この場合も、等間隔なPAM4信号を生成することができる。この場合、消費電力は低減されないが、実施の形態2と同様に、電気信号生成部4を実現する回路の簡易化および製品試験時間の短縮が可能となる。また、光変調器1b~3bの長さは異なっていてもよい。この場合も、振幅を適切に設定することで、等間隔なPAM4信号を生成することができる。
In the above-described example, the amplitude of the electric signal applied to the optical modulators 1b to 3b is made different. However, the amplitude of the electric signal applied to the optical modulator 1b and the optical modulator 2b is changed to the optical modulator 3b. The electric signal to be applied may be the same. As shown in FIG. 9, the optical output when the electric field is not applied even if the amplitude of the electric signal applied to the optical modulator 1b and the optical modulator 2b is extended to the low voltage side is the same. , PAM4 signals at equal intervals can be generated. In this case, the power consumption is not reduced, but the circuit for realizing the electrical signal generation unit 4 can be simplified and the product test time can be shortened as in the second embodiment. Further, the lengths of the optical modulators 1b to 3b may be different. Also in this case, it is possible to generate PAM4 signals at equal intervals by appropriately setting the amplitude.
実施の形態4.
次に、本発明にかかる実施の形態4の光変調モジュールについて説明する。本実施の形態の光変調モジュールの構成は実施の形態2と同様である。実施の形態2と同様の構成および動作については説明を省略し、実施の形態2と異なる点を説明する。Embodiment 4 FIG.
Next, an optical modulation module according to the fourth embodiment of the present invention will be described. The configuration of the light modulation module of the present embodiment is the same as that of the second embodiment. The description of the same configuration and operation as those of the second embodiment will be omitted, and differences from the second embodiment will be described.
次に、本発明にかかる実施の形態4の光変調モジュールについて説明する。本実施の形態の光変調モジュールの構成は実施の形態2と同様である。実施の形態2と同様の構成および動作については説明を省略し、実施の形態2と異なる点を説明する。
Next, an optical modulation module according to the fourth embodiment of the present invention will be described. The configuration of the light modulation module of the present embodiment is the same as that of the second embodiment. The description of the same configuration and operation as those of the second embodiment will be omitted, and differences from the second embodiment will be described.
本実施の形態では、実施の形態2で述べたように、長さの異なる光変調器1a~3aを用いる。図10は、本実施の形態の光変調器1a~3aにおける消光カーブと光変調器1a~3aに印加される電気信号の電圧の振幅とを示す図である。図10では、横軸には光変調器に印加される電圧を示し、縦軸は光変調器通過後の光出力すなわち光信号の強度を示している。図10の縦軸の横には、各光出力すなわち光変調モジュール100aから出力される光信号の強度に対応する値が示されている。図10における光変調器1a~3aの消光カーブは、実施の形態2で示した図7の例と同様である。振幅#1、振幅#2、振幅#3は、光変調器1a、光変調器2a、光変調器3aにそれぞれ印加される電気信号の振幅を示す。
In this embodiment, as described in the second embodiment, the optical modulators 1a to 3a having different lengths are used. FIG. 10 is a diagram showing the extinction curves in the optical modulators 1a to 3a of the present embodiment and the amplitude of the voltage of the electric signal applied to the optical modulators 1a to 3a. In FIG. 10, the horizontal axis represents the voltage applied to the optical modulator, and the vertical axis represents the optical output after passing through the optical modulator, that is, the intensity of the optical signal. A value corresponding to the intensity of each optical output, that is, the optical signal output from the optical modulation module 100a, is shown on the side of the vertical axis in FIG. The extinction curves of the optical modulators 1a to 3a in FIG. 10 are the same as the example of FIG. 7 shown in the second embodiment. Amplitude # 1, amplitude # 2, and amplitude # 3 indicate the amplitudes of electrical signals applied to the optical modulator 1a, the optical modulator 2a, and the optical modulator 3a, respectively.
実施の形態2では、光変調器1a~3aへそれぞれ印加する電気信号の振幅は同一であった。これに対し、本実施の形態では、図10に示すように、光変調器1a~3aへそれぞれ印加する電気信号の振幅は異なっている。詳細には、図10に示したように、振幅#3>振幅#2>振幅#1である。ただし、図10に示すように、OFF時すなわち光を吸収させる場合の電圧値は図7の例と同様とし、ON時すなわち光を吸収させない場合の電圧値を上昇させるように、振幅#2および振幅#1を設定する。この場合、光変調器1aおよび光変調器2aでは、光を吸収させない場合でも、電圧が実施の形態2の場合より高くなるため、実施には若干の吸収が発生して光出力が低下する。したがって、本実施の形態では、光変調器1a~3aの消光比は、互いに異なる。消光比は、電界が印加された場合に出力される光の強度と、電界が印加された場合に出力される光の強度との比である。なお、この光出力の低下が全体の性能に影響のない程度となるように振幅#2および振幅#1を設定すれば実用上は問題ない。
In Embodiment 2, the amplitudes of the electric signals applied to the optical modulators 1a to 3a are the same. On the other hand, in the present embodiment, as shown in FIG. 10, the amplitudes of the electric signals applied to the optical modulators 1a to 3a are different. Specifically, as shown in FIG. 10, amplitude # 3> amplitude # 2> amplitude # 1. However, as shown in FIG. 10, when OFF, that is, when the light is absorbed, the voltage value is the same as that in the example of FIG. 7, and when ON, that is, when the light is not absorbed, the amplitude # 2 and the voltage value are increased. Set amplitude # 1. In this case, in the optical modulator 1a and the optical modulator 2a, even when light is not absorbed, the voltage is higher than in the case of the second embodiment. Therefore, in the present embodiment, the extinction ratios of the optical modulators 1a to 3a are different from each other. The extinction ratio is a ratio between the intensity of light output when an electric field is applied and the intensity of light output when an electric field is applied. If the amplitude # 2 and the amplitude # 1 are set so that the decrease in the light output does not affect the overall performance, there is no practical problem.
以上のように、本実施の形態では、実施の形態2の光変調器1a~3aを用いて、光変調器1a~3aに印加する電気信号の振幅を実施の形態2より抑制する。このため、実施の形態1と同様の効果が得られるとともに、実施の形態2に比べて消費電力を抑制することができる。なお、光変調器1a~3aの並び順は図6に示した例に限定されず、並び順を変更しても同様の効果が得られる。
As described above, in the present embodiment, the amplitudes of electric signals applied to the optical modulators 1a to 3a are suppressed as compared with the second embodiment using the optical modulators 1a to 3a of the second embodiment. For this reason, the same effects as those of the first embodiment can be obtained, and the power consumption can be suppressed as compared with the second embodiment. The arrangement order of the optical modulators 1a to 3a is not limited to the example shown in FIG. 6, and the same effect can be obtained even if the arrangement order is changed.
実施の形態5.
実施の形態1~4では連続光を発生するためのCWレーザ6と変調器とを一体化させた構成例を説明した。本実施の形態の光変調モジュールは、実施の形態1において実装例として述べた光変調モジュールからCWレーザ6を削除する。そして、CWレーザなど外部の光源から入力される連続光が光変調モジュールへ入力される。すなわち、光変調モジュールには、連続光が外部から入力される。外部の光源と光変調モジュールとは、光学レンズを用いてまたはButt-Joint接続により、光学的に接続される。以上述べた以外の本実施の形態の構成および動作は、実施の形態1と同様である。Embodiment 5 FIG.
In the first to fourth embodiments, the configuration example in which theCW laser 6 for generating continuous light and the modulator are integrated has been described. The light modulation module of the present embodiment deletes the CW laser 6 from the light modulation module described as the mounting example in the first embodiment. Then, continuous light input from an external light source such as a CW laser is input to the light modulation module. That is, continuous light is input to the light modulation module from the outside. The external light source and the light modulation module are optically connected using an optical lens or by a Butt-Joint connection. The configuration and operation of this embodiment other than those described above are the same as those of the first embodiment.
実施の形態1~4では連続光を発生するためのCWレーザ6と変調器とを一体化させた構成例を説明した。本実施の形態の光変調モジュールは、実施の形態1において実装例として述べた光変調モジュールからCWレーザ6を削除する。そして、CWレーザなど外部の光源から入力される連続光が光変調モジュールへ入力される。すなわち、光変調モジュールには、連続光が外部から入力される。外部の光源と光変調モジュールとは、光学レンズを用いてまたはButt-Joint接続により、光学的に接続される。以上述べた以外の本実施の形態の構成および動作は、実施の形態1と同様である。
In the first to fourth embodiments, the configuration example in which the
同様に、実施の形態2~4のいずれか1つにおいて実装例として述べた光変調モジュールからCWレーザ6を削除して、外部の光源と光学的に接続されてもよい。この場合も、外部に光源が設けられて光源と光学的に接続される以外は、光変調モジュールの構成および動作は、対応する各実施の形態の動作と同様である。
Similarly, the CW laser 6 may be deleted from the light modulation module described as the mounting example in any one of Embodiments 2 to 4, and optically connected to an external light source. Also in this case, the configuration and operation of the light modulation module are the same as the operations of the corresponding embodiments except that a light source is provided outside and optically connected to the light source.
本実施の形態では、光源との一体化をしないため、光変調モジュールの製造が容易となり、製造時の不良率が低減可能である。
In this embodiment, since it is not integrated with the light source, the manufacture of the light modulation module is facilitated, and the defect rate at the time of manufacture can be reduced.
実施の形態6.
実施の形態1~4では、光変調器としてEAMを用いたが、本実施の形態では、光の経路を切り替えるスイッチ型の強度変調器すなわち光経路切り替え素子を光変調器として用いる。図11は、本実施の形態の光変調モジュール100cの構成例を示す図である。図11では、光経路を切り替えるスイッチとしてリング共振器を用いた例を示している。図11に示した光変調モジュール100cは、それぞれが光変調器であるリング共振器21、リング共振器22およびリング共振器23を備える。また、光変調モジュール100cは、入力ポート24、ドロップポート25,27,29、スルーポート26,28,30および出力ポート31を備える。本実施の形態のリング共振器21~23には、図11では図示を省略した電気信号生成部4から出力される電気信号が印加される。Embodiment 6 FIG.
In the first to fourth embodiments, EAM is used as an optical modulator. However, in this embodiment, a switch-type intensity modulator that switches an optical path, that is, an optical path switching element is used as an optical modulator. FIG. 11 is a diagram illustrating a configuration example of thelight modulation module 100c according to the present embodiment. FIG. 11 shows an example in which a ring resonator is used as a switch for switching the optical path. An optical modulation module 100c illustrated in FIG. 11 includes a ring resonator 21, a ring resonator 22, and a ring resonator 23, each of which is an optical modulator. The optical modulation module 100 c includes an input port 24, drop ports 25, 27, 29, through ports 26, 28, 30 and an output port 31. Electric signals output from the electric signal generator 4 (not shown in FIG. 11) are applied to the ring resonators 21 to 23 of the present embodiment.
実施の形態1~4では、光変調器としてEAMを用いたが、本実施の形態では、光の経路を切り替えるスイッチ型の強度変調器すなわち光経路切り替え素子を光変調器として用いる。図11は、本実施の形態の光変調モジュール100cの構成例を示す図である。図11では、光経路を切り替えるスイッチとしてリング共振器を用いた例を示している。図11に示した光変調モジュール100cは、それぞれが光変調器であるリング共振器21、リング共振器22およびリング共振器23を備える。また、光変調モジュール100cは、入力ポート24、ドロップポート25,27,29、スルーポート26,28,30および出力ポート31を備える。本実施の形態のリング共振器21~23には、図11では図示を省略した電気信号生成部4から出力される電気信号が印加される。
In the first to fourth embodiments, EAM is used as an optical modulator. However, in this embodiment, a switch-type intensity modulator that switches an optical path, that is, an optical path switching element is used as an optical modulator. FIG. 11 is a diagram illustrating a configuration example of the
リング共振器21~23では、印加される電気信号がオンの場合には、光導波路から入力される光が光カップリングにより、全てリング共振器21~23へ移るように設計されて制御される。また、印加される電気信号がオフの場合には、光導波路から入力される光が、一部がリング共振器21~23へ移り、残りがスルーポートへ移るように設計されて制御される。リング共振器21の入力側の光導波路は、入力ポート24であり、リング共振器22の入力側の光導波路は、ドロップポート25であり、リング共振器23の入力側の光導波路は、ドロップポート27である。また、リング共振器21に移った光はドロップポート25へ移り、リング共振器22に移った光はドロップポート27へ移り、リング共振器23に移った光はドロップポート29へ移るように設計および制御される。
The ring resonators 21 to 23 are designed and controlled so that when the applied electrical signal is on, all the light input from the optical waveguide is transferred to the ring resonators 21 to 23 by optical coupling. . Further, when the applied electrical signal is OFF, the light input from the optical waveguide is designed and controlled so that part of it moves to the ring resonators 21 to 23 and the rest moves to the through port. The optical waveguide on the input side of the ring resonator 21 is the input port 24, the optical waveguide on the input side of the ring resonator 22 is the drop port 25, and the optical waveguide on the input side of the ring resonator 23 is the drop port. 27. Further, the light transferred to the ring resonator 21 is transferred to the drop port 25, the light transferred to the ring resonator 22 is transferred to the drop port 27, and the light transferred to the ring resonator 23 is transferred to the drop port 29. Be controlled.
リング共振器21は、11/10変調を行い、リング共振器22は、11/01変調を行い、リング共振器23は、11/00変調を行う。電気信号生成部4は、実施の形態1と同様に、光変調器であるリング共振器21~23へそれぞれOOK信号を印加する。各リング共振器21~23は、オンを示す電気信号が入力された場合に共振し、オフを示す電気信号が入力された場合に共振しない。本実施の形態の光変調モジュール100cから出力されるPAM4信号すなわち出力信号の示す値と、各リング共振器21~23に印加する電気信号との対応は、実施の形態1で示した図3と同様である。
The ring resonator 21 performs 11/10 modulation, the ring resonator 22 performs 11/01 modulation, and the ring resonator 23 performs 11/00 modulation. As in the first embodiment, the electrical signal generator 4 applies an OOK signal to each of the ring resonators 21 to 23 that are optical modulators. Each of the ring resonators 21 to 23 resonates when an electrical signal indicating ON is input, and does not resonate when an electrical signal indicating OFF is input. The correspondence between the PAM4 signal output from the light modulation module 100c of the present embodiment, that is, the value indicated by the output signal, and the electric signal applied to each of the ring resonators 21 to 23 is the same as that shown in FIG. It is the same.
光変調モジュール100cでは、11の値のPAM4信号を出力する場合は、全てのリング共振器21~23に印加される電気信号はオンである。光源から出力された連続光は、入力ポート24を介してリング共振器21へ入力され、リング共振器21で共振し、ドロップポート25へ移る。ドロップポート25へ移った光は、リング共振器22へ入力され、リング共振器22で共振し、ドロップポート27へ移る。ドロップポート27へ移った光は、リング共振器23へ入力され、リング共振器23で共振し、ドロップポート29へ移る。ドロップポート29へ移った光は、出力ポート31からPAM4信号として出力される。
In the light modulation module 100c, when the PAM4 signal having the value 11 is output, the electrical signals applied to all the ring resonators 21 to 23 are on. The continuous light output from the light source is input to the ring resonator 21 through the input port 24, resonates at the ring resonator 21, and moves to the drop port 25. The light transferred to the drop port 25 is input to the ring resonator 22, resonates at the ring resonator 22, and moves to the drop port 27. The light transferred to the drop port 27 is input to the ring resonator 23, resonates at the ring resonator 23, and moves to the drop port 29. The light transferred to the drop port 29 is output from the output port 31 as a PAM4 signal.
また、光変調モジュール100cでは、10の値のPAM4信号を出力する場合は、リング共振器21に印加される電気信号はオフであり、リング共振器22およびリング共振器23に印加される電気信号はオンである。このため、光源から入力ポート24を介して入力された連続光は、一部がスルーポート26に残り、残りがドロップポート25へ移る。この時、ドロップポート25へ移る光の強度が10の値に対応する強度となるようにリング共振器21を設計して制御する。リング共振器22およびリング共振器23はオンであるため、ドロップポート25へ移った光は、リング共振器22により共振し、ドロップポート27へ移る。ドロップポート27へ移った光は、リング共振器23へ入力され、リング共振器23で共振し、ドロップポート29へ移る。ドロップポート29へ移った光は、出力ポート31からPAM4信号として出力される。01の値のPAM4信号を出力する場合、および00の値のPAM4信号を出力する場合も、同様に、図3に示した電気信号が印加されることにより、各値に対応するPAM4信号が出力される。また、リング共振器22は、リング共振器21がオンでありリング共振器22がオフの場合に、ドロップポート27へ移る光の強度が01の値となるように、設計され制御される。また、リング共振器23は、リング共振器21およびリング共振器22がオンでありリング共振器23がオフの場合に、ドロップポート29へ移る光の強度が00の値となるように、設計され制御される。
Further, in the light modulation module 100c, when a PAM4 signal having a value of 10 is output, the electrical signal applied to the ring resonator 21 is off, and the electrical signal applied to the ring resonator 22 and the ring resonator 23. Is on. For this reason, a part of the continuous light input from the light source via the input port 24 remains in the through port 26 and the rest moves to the drop port 25. At this time, the ring resonator 21 is designed and controlled so that the intensity of light transferred to the drop port 25 becomes an intensity corresponding to a value of 10. Since the ring resonator 22 and the ring resonator 23 are on, the light that has moved to the drop port 25 resonates by the ring resonator 22 and moves to the drop port 27. The light transferred to the drop port 27 is input to the ring resonator 23, resonates at the ring resonator 23, and moves to the drop port 29. The light transferred to the drop port 29 is output from the output port 31 as a PAM4 signal. Similarly, when outputting a PAM4 signal having a value of 01 and outputting a PAM4 signal having a value of 00, the PAM4 signal corresponding to each value is output by applying the electrical signal shown in FIG. Is done. The ring resonator 22 is designed and controlled so that the intensity of light transferred to the drop port 27 becomes a value of 01 when the ring resonator 21 is on and the ring resonator 22 is off. The ring resonator 23 is designed so that the intensity of light transferred to the drop port 29 becomes a value of 00 when the ring resonator 21 and the ring resonator 22 are on and the ring resonator 23 is off. Be controlled.
以上のように、本実施の形態では、光変調器にリング共振器を用いて、実施の形態1と同様に、OOK信号を用いてPAM4信号を生成する。したがって、精密な位相の制御を必要とせずに多値変調信号を生成することができる。また、本実施の形態では、EAMに用いられる化合物半導体を用いる必要が無く、例えばシリコンのような安価な材料を用いて、多値変調を実現できる。なお、リング共振器21~23の順序を入れ替えても同様の効果が得られる。
As described above, in the present embodiment, a PAM4 signal is generated using an OOK signal as in the first embodiment, using a ring resonator as an optical modulator. Therefore, a multilevel modulation signal can be generated without requiring precise phase control. In this embodiment, it is not necessary to use a compound semiconductor used for EAM, and multilevel modulation can be realized using an inexpensive material such as silicon. The same effect can be obtained even if the order of the ring resonators 21 to 23 is changed.
以上の実施の形態に示した構成は、本発明の内容の一例を示すものであり、別の公知の技術と組み合わせることも可能であるし、本発明の要旨を逸脱しない範囲で、構成の一部を省略、変更することも可能である。
The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.
100,100a,100b,100c 光変調モジュール、1,1a,1b,2,2a,2b,3,3a,3b 光変調器、4 電気信号生成部、5 半導体、6 CWレーザ、21~23 リング共振器。
100, 100a, 100b, 100c light modulation module, 1, 1a, 1b, 2, 2a, 2b, 3, 3a, 3b light modulator, 4 electrical signal generator, 5 semiconductor, 6 CW laser, 21-23 ring resonance vessel.
Claims (11)
- 連続光に対して光強度変調を行う第1の光変調器と、
前記第1の光変調器により光強度変調された光に対して光強度変調を行う第2の光変調器と、
前記第2の光変調器により光強度変調された光に対して光強度変調を行う第3の光変調器と、
2値の電気信号である第1の電気信号を前記第1の光変調器に印加し、2値の電気信号である第2の電気信号を前記第2の光変調器に印加し、2値の電気信号である第3の電気信号を前記第3の光変調器に印加する信号生成部と、
を備えることを特徴とする光変調モジュール。 A first light modulator for performing light intensity modulation on the continuous light;
A second light modulator that performs light intensity modulation on the light that has been light intensity modulated by the first light modulator;
A third light modulator that performs light intensity modulation on the light that has been light intensity modulated by the second light modulator;
A first electrical signal, which is a binary electrical signal, is applied to the first optical modulator, and a second electrical signal, which is a binary electrical signal, is applied to the second optical modulator, and binary A signal generator that applies a third electrical signal that is an electrical signal of the second optical modulator to the third optical modulator;
An optical modulation module comprising: - 前記第1、第2および第3の光変調器は、電界吸収型の光変調器であることを特徴とする請求項1に記載の光変調モジュール。 The light modulation module according to claim 1, wherein the first, second, and third light modulators are electroabsorption type light modulators.
- 前記第1、第2および第3の光変調器のバンドギャップは同一であることを特徴とする請求項2に記載の光変調モジュール。 The optical modulation module according to claim 2, wherein band gaps of the first, second and third optical modulators are the same.
- 前記第1、第2および第3の光変調器のバンドギャップは互いに異なることを特徴とする請求項2に記載の光変調モジュール。 The optical modulation module according to claim 2, wherein band gaps of the first, second, and third optical modulators are different from each other.
- 前記第1、第2および第3の光変調器の光路長は同一であることを特徴とする請求項2から4のいずれか1つに記載の光変調モジュール。 The optical modulation module according to any one of claims 2 to 4, wherein the optical path lengths of the first, second and third optical modulators are the same.
- 前記第1、第2および第3の光変調器の光路長は互いに異なることを特徴とする請求項2から4のいずれか1つに記載の光変調モジュール。 The optical modulation module according to any one of claims 2 to 4, wherein optical path lengths of the first, second, and third optical modulators are different from each other.
- 前記第1、第2および第3の光変調器における消光比は互いに異なることを特徴とする請求項6に記載の光変調モジュール。 The optical modulation module according to claim 6, wherein extinction ratios in the first, second and third optical modulators are different from each other.
- 前記連続光を生成する光源、
を備えることを特徴とする請求項1から7のいずれか1つに記載の光変調モジュール。 A light source for generating the continuous light;
The light modulation module according to claim 1, further comprising: - 前記第1、第2および第3の光変調器と前記光源とが同一チップに集積されることを特徴とする請求項8に記載の光変調モジュール。 9. The light modulation module according to claim 8, wherein the first, second, and third light modulators and the light source are integrated on the same chip.
- 前記連続光は、前記光変調モジュールの外部から入力されることを特徴とする請求項1から7のいずれか1つに記載の光変調モジュール。 The light modulation module according to any one of claims 1 to 7, wherein the continuous light is input from the outside of the light modulation module.
- 前記第1、第2および第3の光変調器は、光経路切り替え素子であることを特徴とする請求項1に記載の光変調モジュール。 The light modulation module according to claim 1, wherein the first, second, and third light modulators are light path switching elements.
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