WO2015154813A1 - Mach-zehnder modulator and method for operating a mach-zehnder modulator - Google Patents

Mach-zehnder modulator and method for operating a mach-zehnder modulator Download PDF

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Publication number
WO2015154813A1
WO2015154813A1 PCT/EP2014/057318 EP2014057318W WO2015154813A1 WO 2015154813 A1 WO2015154813 A1 WO 2015154813A1 EP 2014057318 W EP2014057318 W EP 2014057318W WO 2015154813 A1 WO2015154813 A1 WO 2015154813A1
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Prior art keywords
control electrode
voltage
mach
electrode arrangement
optical
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PCT/EP2014/057318
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French (fr)
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Detlef Hoffmann
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Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
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Priority to PCT/EP2014/057318 priority Critical patent/WO2015154813A1/en
Publication of WO2015154813A1 publication Critical patent/WO2015154813A1/en

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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 
    • G02F1/03—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 ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
    • G02F1/0305—Constructional arrangements
    • G02F1/0316—Electrodes
    • 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 
    • G02F1/21—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  by interference
    • G02F1/212—Mach-Zehnder type
    • 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
    • G02F2201/12—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00 electrode
    • G02F2201/127—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00 electrode travelling wave

Definitions

  • the invention relates to a Mach-Zehnder modulator according to the preamble of claim 1 and a method for operating a Mach-Zehnder modulator according to the preamble of claim 12.
  • Mach-Zehnder modulators are known to be employed as high frequency transmitters in optical communication systems.
  • Such Mach-Zehnder modulators in particular, comprise two optical interferometer branches consisting of optical waveguides and high frequency waveguide electrodes for applying a high frequency voltage across the optical waveguides.
  • additional phase electrodes may be provided for shifting the working point of the modulator in order to compensate different optical path lengths of the interferometer branches caused by fabrication tolerances.
  • the additional phase electrodes are capable of shifting the phase of an optical signal propagating through the modulator branches.
  • the article "Travelling wave Mach-Zehnder modulators", Prosyk, K. et al., International Conference on Indium Phosphide and Related Materials (IPRM), 2013, p. 1 -2 discloses such a modulator.
  • IPRM Indium Phosphide and Related Materials
  • the object of the invention is to provide a Mach-Zehnder modulator that may compensate for fabrication tolerances without deteriorating the extinction ratio of the modulator.
  • a Mach-Zehnder modulator comprising
  • a first control electrode arrangement separate from the first alternating voltage electrode arrangement and for supplying a first DC voltage across the first optical branch;
  • first control electrode arrangement and/or the second control electrode arrangement comprises a first control electrode and a second control electrode
  • the length of the first control electrode is different from the length of the second control electrode.
  • a phase shift is created in the first optical branch by the first DC voltage, wherein an undesired absorption change also caused by the first DC voltage may be compensated by means of the second DC voltage.
  • an absorption is induced in the second optical branch whose value compares to the value of the absorption change that is associated with the phase shift created in the first optical branch by applying the first voltage to the first optical branch.
  • the second voltage is set in such a way that the intensity (or amplitude) of an optical wave that propagated through the first optical branch equals the intensity (or amplitude) of an optical wave that propagated through the second optical branch of the modulator at an output port (e.g. an output coupler) of the modulator.
  • a differential absorber may be realized, i.e. different absorptions are created in the optical branches of the modulator while equal phase shifts are induced (i.e. a phase shift compensation is carried out instead of the above-mentioned absorption compensation according to the first alternative of the invention).
  • phase shift function and the absorber function to realize a phase shift compensation and an absorption compensation at the same time.
  • the absorption compensation would be necessary e.g. also in order to compensate for errors in splitting and/or combining units of the MZI. It is noted that the phase shift and the absorption induced by the first and second voltage in the corresponding optical branches of the modulator increases with increasing voltages.
  • the dependency of the phase shift and the absorption on the applied voltage is different such that by using first and second control electrode arrangements with different effective interaction lengths a phase shift might be induced in the first optical branch, wherein the absorption change associated with this phase shift can be compensated by applying a different (larger) voltage to a second electrode arrangement which has a smaller effective length than the first control electrode arrangement (or vice versa).
  • the dependency of the phase shift on the voltage can be approximated by a second order polynomial, wherein the dependency of the absorption has an exponential behavior as will be explained in more detail below.
  • different effective interaction lengths of the control electrodes are created by different physical lengths of the electrodes.
  • a phase shift is created via the first control electrode that is longer than the second control electrode that is used for absorption compensation.
  • the other way round the shorter control electrode may be used for creating the phase shift and the longer control electrode is employed for compensating the undesired absorption.
  • a phase shift shall be induced into a signal propagating through the first optical branch of the modulator, a first DC voltage is applied to the first control electrode (phase shift electrode) of the first control electrode arrangement (the first control electrode being longer than the second control electrode) while no voltage is supplied to the second control electrode.
  • a second DC voltage is applied to the second control electrode (i.e. the compensation electrode) of the second control electrode arrangement for creating an additional absorption in the second optical branch (and also a (small) phase shift that may be taken into account when setting the first DC voltage).
  • the first alternating electrode arrangement comprises a first high frequency electrode arrangement and the second alternating electrode arrangement comprises a second high frequency electrode arrangement.
  • the Mach- Zehnder modulator may be operated using a high frequency voltage source (a driver) that supplies a high frequency signal to both the first and the second high frequency electrode arrangement.
  • the first high frequency electrode arrangement is a first travelling wave electrode and the second high frequency electrode arrangement is a second travelling wave electrode.
  • the second control arrangement may comprise a first control electrode (e.g. a phase shift electrode) and a second control electrode (e.g. a compensation electrode), the length of the compensation electrode being shorter than the length of the phase shift electrode.
  • phase shift is introduced into an optical signal propagating through the first optical branch using the phase shift electrode of the first control electrode arrangement or a phase shift is induced into an optical signal propagating through the second optical branch using the phase shift electrode of the second control electrode arrangement.
  • the undesired absorption is then compensated by applying a voltage to the compensation electrode of the first control electrode arrangement.
  • the Mach-Zehnder modulator comprises an input power divider (e.g. an MMI), wherein the first and the second control electrode arrangement is arranged between the power divider and the first and the second high frequency electrode arrangement.
  • the Mach-Zehnder modulator may also comprise an output power divider, wherein the first and the second control electrode arrangement is arranged between the first and the second high frequency electrode arrangement and the output power divider.
  • the first and the second optical branch of the modulator may consist of a first and a second optical waveguide, respectively.
  • the first and the second optical branch besides an optical waveguide comprises further components.
  • the first and/or the second optical branch may comprise a sub-Mach-Zehnder modulator for realizing an IQ modulator used e.g. for QPSK (Quaternary Phase Shift Keying) modulation schemes.
  • a Mach-Zehnder modulator thus comprises a parent Mach- Zehnder structure (outer MZ) comprising the first and the second optical branch and the two (child) Mach-Zehnder modulators.
  • IQ modulators may also comprise an input power divider dividing an incoming optical signal into a first signal propagating through the first optical branch and a second signal propagating through the second optical branch.
  • the first and the second control electrode arrangement may then be arranged between the input power divider and the sub-Mach-Zehnder modulators.
  • the invention also relates to an optical circuit comprising a Mach-Zehnder modulator as described above. Furthermore, the invention is related to a method of operating a Mach-Zehnder modulator as described above, comprising the steps of
  • a change of the absorption of the corresponding branch is created that compensates the change of the absorption of the other optical branch created by the first voltage, or - a change of absorption of the corresponding optical branch is created that differs from the change of absorption created by the first voltage and creates a phase shift of an optical signal propagating through the corresponding optical branch that equals the phase shift induced by the first voltage in the other optical branch.
  • Embodiments of the invention are described hereinafter with reference to the drawings, which show: a simulated optical transmission of a Mach-Zehnder modulator dependent on an alternating voltage applied between high frequency electrode arrangements of the modulator; the optical transmission of the modulator of Figure 1 A after a conventional phase correction was carried out; the absorption and the phase shift created in an optical waveguide using a short and a long control electrode, respectively; a Mach-Zehnder modulator according to an embodiment of the invention; the optical transmission of the Mach-Zehnder modulator of Figure 3 after a phase correction was carried out; a Mach-Zehnder modulator according to another embodiment of the invention; and
  • FIG. 6A, 6B further examples of the transmission of a MZI modulator according to the invention.
  • Figure 1 A shows a typical transmission curve (the output intensity) of a Mach-Zehnder modulator, wherein the output intensity is shown on a logarithmic scale (y-axis) relative to an alternating voltage (x-axis, amplitude of the alternating voltage) applied between a first and a second high frequency electrode arrangement of the modulator.
  • the minima of the transmission curve represent possible working points of the modulator. For example, one of the potential working points (at about -1 V, denominated "WP" in Fig. 1 A) is shifted to negative voltages relative to the zero voltage point. Thus, for obtaining efficient operation of the modulator, the transmission curve has to be shifted to the right in order to shift the minimum towards the zero voltage point. This can be achieved by introducing a phase shift in one of the optical branches of the modulator by means of an additional phase shift electrode. The resulting transmission curve is shown in Figure 1 B, wherein the working point WP has been shifted on the zero voltage point. It is noted that instead of a minimum of the transmission function other working points could be used, e.g.
  • a 3 dB point located halfway between a minimum and an adjacent maximum. It is noted that the different amplitudes of the relative minima and the relative maxima of the transmission curve are due to the voltage dependence of the phase and the absorption change.
  • a long phase shift electrode may be used instead of a short electrode since the longer the phase shift electrode, the lower an undesired absorption associated with the phase shift as illustrated in Figure 2. That Figure depicts the absorption versus the phase shift created in an optical waveguide using an exemplary short electrode (having a length of 50 ⁇ , dashed-dotted line) and an exemplary long phase shift electrode (500 ⁇ , continuous line), respectively.
  • the absorption-phase shift behavior of the longer electrode differs considerably from the behavior of the shorter electrode.
  • the different behavior results from the different voltage dependency of the phase shift and the absorption.
  • absorption a of the optical waveguide created by applying the voltage V to the optical wave guide can be approximated by the following potential function (ai , a 2 being suited coefficients):
  • an undesired absorption change created by a phase shift electrode in one of the modulator branches can be equalized by inducing an identical absorption in the other modulator branch, i.e. by using a compensation electrode whose length is shorter than the length of the phase shift electrode of the other modulator branch.
  • a phase shift might be compensated and different absorptions of the modulator branches may be generated.
  • FIG. 3 shows a Mach-Zehnder modulator 1 (MZI modulator) according to the invention capable of compensating an undesired absorption change occurring in one of its optical branches caused by inducing a phase shift in that modulator branch.
  • the modulator 1 comprises a first and a second optical branch 1 1 , 12 formed by a first and a second optical waveguide 1 1 1 , 121 .
  • the MZI modulator 1 comprises an input waveguide 13 via which light can be coupled into the modulator 1 .
  • the input waveguide 13 is coupled to a power divider 14 in the form of an MMI that comprises two output ports connected to the first and the second optical waveguide 1 1 1 , 121 , respectively.
  • An output section of modulator 1 comprises an output MMI 15 that connects the optical waveguides 1 1 1 , 121 to an output waveguide 16.
  • the first modulator branch 1 1 further comprises a first alternating voltage electrode arrangement 1 12 and similarly the second branch 12 comprises a second alternating voltage electrode arrangement 122.
  • Both, the first and the second alternating voltage electrode electrode arrangement 1 12, 122 comprise a high frequency electrode arrangement in the form of a first and a second travelling wave electrode 1 13, 123, respectively.
  • a high bit rate signal (a voltage having frequency components up to e.g. at least 40 GHz) will be supplied to the travelling wave electrode 1 13, 123 which is converted into a high bit rate optical signal available at an output port of the output MMI 15 and thus coupled into output optical waveguide 16.
  • the travelling wave electrodes 1 13, 123 each comprise a section that is arranged on top of the optical waveguides 1 1 1 , 121 .
  • the Mach-Zehnder modulator 1 comprises a first and the second control electrode arrangement 1 14, 124, wherein each one of the control electrode arrangement 1 14, 124 consists of a first control electrode in the form of a phase shift electrode 1 15, 125 and a second control electrode in the form of a separate compensation electrode 1 16, 126 arranged on the optical waveguides 1 1 1 , 121 , respectively.
  • the compensation electrodes 1 16, 126 are arranged in a distance (along the optical waveguides 1 1 1 , 121 ) from the phase shift electrodes 1 15, 125, wherein the length of the compensation electrodes 1 16, 126 (measured along the first and the second optical waveguide 1 1 1 , 121 ) is shorter than the length of the corresponding phase shift electrode 1 15, 125.
  • control electrode arrangements 1 14, 124 are arranged between the input MMI 14 and the travelling wave electrodes 1 13, 123. Both, the first and the second control electrode arrangement 1 14, 124 are arranged in distance from the travelling wave electrodes, i.e. there is a gap between the electrode arrangements 1 14, 124 and the corresponding travelling wave electrodes 1 13, 123.
  • a DC voltage source (not shown) is connected to the control electrode arrangements 1 14, 124, wherein a high frequency voltage source is connected to the travelling wave electrodes 1 13, 123.
  • the operation of the control electrode arrangements 1 14, 124 is as follows: Depending on the position of a suited worked point of MZI modulator 1 (such as the working point WP in Fig.
  • a phase shift has to be introduced into the first or into the second optical branch 1 1 , 12 of the modulator 1 in order to shift the working point towards the zero voltage point.
  • a (first) DC voltage is applied to either the phase electrode 1 15 of the first control electrode arrangement 1 14 or the phase electrode 125 of the second control electrode arrangement 124. Applying the first voltage to phase shift electrode 1 15 or 125 also creates an undesired change (in particular an increase) of the absorption in the corresponding optical modulator branch 1 1 , 12.
  • This absorption change is compensated or at least thwarted by supplying a (second) DC voltage to the compensation electrode of the respective other modulator branch, i.e.
  • a longer electrode one of the phase shift electrodes 1 15, 125
  • a shorter electrode one of the compensation electrodes 1 16, 1266
  • the invention is not restricted to the control electrode arrangements (comprising both a control and a compensation electrode) shown in Fig. 3.
  • each one of the control electrode arrangements may comprise a single electrode only, wherein the lengths of the electrode of the first control arrangement may be different from the length of the electrode of the second control arrangement.
  • no phase shift / compensation electrodes in addition to the travelling wave electrodes are provided. Rather, the phase shift and the absorption compensation may be carried out by applying suited DC voltages to the travelling wave electrodes.
  • the MZI modulator 1 may be a semiconductor device, wherein the optical waveguides 1 1 1 , 1 12 may comprise a semiconductor material (e.g. a quaternary material or a multi-quantum well) whose refractive index changes by applying a voltage.
  • the basic optical and electrical layout of the modulator may be designed as described in the article "Travelling wave Mach- Zehnder modulators", Prosyk, K. et al., International Conference on Indium Phosphide and Related Materials (IPRM), 2013, p. 1 -2 already mentioned above, or in the publication "45 GHz Bandwidth Travelling Wave Electrode Mach-Zehnder Modulator with Integrated Spot Size Converter", D. Hoffmann, Proceedings International Conference on Indium Phosphide and Related Materials, p. 585, 2004, wherein the content of these articles in respect to the principle optical and electrical design of the Mach-Zehnder modulator arrangement is incorporated by reference herewith.
  • control electrode arrangements 1 14, 124 could also be operated in such a way that a differential absorber is created.
  • the phase shift electrode of one of the control electrode arrangements 1 14, 124 and the compensation electrode of the other one of the control electrode arrangements 1 14, 124 is used to create equal phase shifts but different absorptions in the optical modulator branches 1 1 , 12.
  • the control electrode arrangements 1 14, 124 are arranged in the rear region of the modulator, i.e. between the travelling wave electrodes 1 13, 123 and the output MMI 15.
  • phase shift electrodes 1 15, 125 are arranged between the input MMI 14 and the compensation electrodes 1 16, 126.
  • Figure 4 shows a simulation of the output of the modulator shown in Figure 3 after correcting the working point by introducing a phase shift using one of the phase shift electrodes 1 15, 125 and compensating the absorption by applying a voltage to one of the compensation electrodes 1 16, 126.
  • the working point WP is shifted onto the zero voltage point, while the output intensity at the zero voltage point is considerably lower relative to the non-compensated case (see Fig. 1 B).
  • the extinction of the modulator drastically improves.
  • Figure 5 depicts a MZI modulator 1 ' according to another embodiment of the invention.
  • the modulator is an IQ modulator. That is, the optical branches 1 1 ', 12' of the modulator do not consist of optical waveguides 1 1 1 ', 121 ' only, but additionally comprise sub-MZI modulators 10, 20.
  • each one of the optical branches 1 1 ', 12' of IQ modulator 1 ' comprises two modulator branches.
  • the first and the second alternating voltage electrode arrangement 1 12', 122' of IQ modulator 1 ' each has a high frequency electrode arrangement 1 13', 123' (each of them comprising the two travelling wave electrodes of sub-MZI modulators 10, 20) and in addition comprises the control electrode arrangements of the corresponding sub-MZI modulators 10, 20.
  • IQ modulator 1 ' comprises a first and a second control electrode arrangement 1 14', 124' arranged on top of the optical waveguides 1 1 1 ', 121 ' and between in input power divider 14' and the sub-MZI modulators 10, 20, respectively.
  • the control electrode arrangements 1 14', 124' each consists of a first control electrode in the form of a phase shift electrode 1 15', 125' and a second control electrode in the form of a compensation electrode 1 16', 126', the compensation electrodes 1 16', 126' being shorter than the phase shift electrodes 1 15', 125'.
  • a first DC voltage will be applied to one of the phase shift electrodes 1 15', 125' for creating a phase shift in one of the optical branches 1 1 ', 12' and a second DC voltage can be applied to one of the compensation electrodes 1 16', 126' of the other optical branch as set forth above with respect to Fig. 3.
  • the sub-MZI modulators 10, 20 do not necessarily have to be designed as the modulator shown in Fig. 3. Rather, other types of sub-MZI modulators could be used that do not comprise a control electrode arrangement such that the phase control and absorption compensation is carried out by the control electrode arrangement 1 14', 124' of the IQ modulator 1 '.
  • the MZI modulator according to the invention may be operated as an optical duobinary component. This operation uses three working points of the transmission curve such as the points "- ⁇ , "0" and “+1 " illustrated in Figures 6A (linear plot of the transmission curve) and 6B (logarithmic plot of the transmission curve).
  • Using the MZI modulator according to the invention on the one hand permits the transmission curve to be shifted in such a way that a minimum ("0") is located at the zero voltage point as set forth above.
  • the MZI modulator according to the invention allows the amplitude of the transmission curve at the maxima "-1 ", "+1 " adjacent the minimum "0” to be adapted such that they assume essentially the same value.

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Abstract

The invention relates to an electro-optic Mach-Zehnder modulator, comprising a first and a second optical branch (11, 11', 12, 12'); a first alternating voltage electrode arrangement (112, 112') for applying an alternating voltage across the first optical branch (11, 11'); a second alternating voltage electrode arrangement (122, 122') for applying an alternating voltage across the second optical branch (12, 12'); a first control electrode arrangement (114, 114') separate from the first alternating voltage electrode arrangement (112, 112') and for supplying a DC voltage across the first optical branch (11, 11'); a second control electrode arrangement (124, 124') separate from the second alternating voltage electrode arrangement (122, 122') and for supplying a DC voltage across the second optical branch (12, 12'), wherein the first control electrode arrangement (114, 114') and/or the second control electrode arrangement (124, 124') comprises a first control electrode (115, 115', 125, 125') and a second control electrode (116, 116', 126, 126'). According to the invention, the length of the first control electrode (115, 115', 125, 125') is different from the length of the second control electrode (116, 116', 126, 126'). The invention also relates to a method for operating a Mach-Zehnder modulator.

Description

Mach-Zehnder Modulator and Method for Operating a Mach-Zehnder Modulator
Description
The invention relates to a Mach-Zehnder modulator according to the preamble of claim 1 and a method for operating a Mach-Zehnder modulator according to the preamble of claim 12.
Mach-Zehnder modulators are known to be employed as high frequency transmitters in optical communication systems. Such Mach-Zehnder modulators, in particular, comprise two optical interferometer branches consisting of optical waveguides and high frequency waveguide electrodes for applying a high frequency voltage across the optical waveguides. Further, additional phase electrodes may be provided for shifting the working point of the modulator in order to compensate different optical path lengths of the interferometer branches caused by fabrication tolerances. The additional phase electrodes are capable of shifting the phase of an optical signal propagating through the modulator branches. For example, the article "Travelling wave Mach-Zehnder modulators", Prosyk, K. et al., International Conference on Indium Phosphide and Related Materials (IPRM), 2013, p. 1 -2 discloses such a modulator. However, the creation of an additional phase shift may deteriorate the extinction ratio of the modulator.
The object of the invention is to provide a Mach-Zehnder modulator that may compensate for fabrication tolerances without deteriorating the extinction ratio of the modulator. According to the invention, a Mach-Zehnder modulator is provided, comprising
- a first and a second optical branch;
- a first alternating voltage electrode arrangement for applying an alternating voltage across the first optical branch;
- a second alternating voltage electrode arrangement for applying an alternating voltage across the second optical branch;
- a first control electrode arrangement separate from the first alternating voltage electrode arrangement and for supplying a first DC voltage across the first optical branch;
- a second control electrode arrangement separate from the second alternating voltage electrode arrangement and for supplying a second DC voltage across the second optical branch, wherein the first control electrode arrangement and/or the second control electrode arrangement comprises a first control electrode and a second control electrode, and wherein
- the length of the first control electrode is different from the length of the second control electrode.
For example, a phase shift is created in the first optical branch by the first DC voltage, wherein an undesired absorption change also caused by the first DC voltage may be compensated by means of the second DC voltage. In particular, by applying the second DC voltage to the second optical branch, an absorption is induced in the second optical branch whose value compares to the value of the absorption change that is associated with the phase shift created in the first optical branch by applying the first voltage to the first optical branch. In particular, the second voltage is set in such a way that the intensity (or amplitude) of an optical wave that propagated through the first optical branch equals the intensity (or amplitude) of an optical wave that propagated through the second optical branch of the modulator at an output port (e.g. an output coupler) of the modulator.
As an alternative application, a differential absorber may be realized, i.e. different absorptions are created in the optical branches of the modulator while equal phase shifts are induced (i.e. a phase shift compensation is carried out instead of the above-mentioned absorption compensation according to the first alternative of the invention).
Another application could be the combination of the phase shift function and the absorber function to realize a phase shift compensation and an absorption compensation at the same time. The absorption compensation would be necessary e.g. also in order to compensate for errors in splitting and/or combining units of the MZI. It is noted that the phase shift and the absorption induced by the first and second voltage in the corresponding optical branches of the modulator increases with increasing voltages. However, the dependency of the phase shift and the absorption on the applied voltage is different such that by using first and second control electrode arrangements with different effective interaction lengths a phase shift might be induced in the first optical branch, wherein the absorption change associated with this phase shift can be compensated by applying a different (larger) voltage to a second electrode arrangement which has a smaller effective length than the first control electrode arrangement (or vice versa). In particular, the dependency of the phase shift on the voltage can be approximated by a second order polynomial, wherein the dependency of the absorption has an exponential behavior as will be explained in more detail below.
According to the invention, different effective interaction lengths of the control electrodes are created by different physical lengths of the electrodes. In particular, a phase shift is created via the first control electrode that is longer than the second control electrode that is used for absorption compensation. However, it is not excluded that the other way round the shorter control electrode may be used for creating the phase shift and the longer control electrode is employed for compensating the undesired absorption. For example, if a phase shift shall be induced into a signal propagating through the first optical branch of the modulator, a first DC voltage is applied to the first control electrode (phase shift electrode) of the first control electrode arrangement (the first control electrode being longer than the second control electrode) while no voltage is supplied to the second control electrode. It is also possible to apply the first DC voltage to both the first and the second control electrode, thereby using the total length of both electrodes to create the phase shift. A second DC voltage is applied to the second control electrode (i.e. the compensation electrode) of the second control electrode arrangement for creating an additional absorption in the second optical branch (and also a (small) phase shift that may be taken into account when setting the first DC voltage).
According to another embodiment of the invention, the first alternating electrode arrangement comprises a first high frequency electrode arrangement and the second alternating electrode arrangement comprises a second high frequency electrode arrangement. That is, the Mach- Zehnder modulator may be operated using a high frequency voltage source (a driver) that supplies a high frequency signal to both the first and the second high frequency electrode arrangement. For example, the first high frequency electrode arrangement is a first travelling wave electrode and the second high frequency electrode arrangement is a second travelling wave electrode. For example, not only the first control electrode arrangement but also the second control arrangement may comprise a first control electrode (e.g. a phase shift electrode) and a second control electrode (e.g. a compensation electrode), the length of the compensation electrode being shorter than the length of the phase shift electrode. Thus, depending on the sign of the desired phase shift for adjusting the working point of the modulator either a phase shift is introduced into an optical signal propagating through the first optical branch using the phase shift electrode of the first control electrode arrangement or a phase shift is induced into an optical signal propagating through the second optical branch using the phase shift electrode of the second control electrode arrangement. The undesired absorption is then compensated by applying a voltage to the compensation electrode of the first control electrode arrangement.
According to another embodiment of the invention, the Mach-Zehnder modulator comprises an input power divider (e.g. an MMI), wherein the first and the second control electrode arrangement is arranged between the power divider and the first and the second high frequency electrode arrangement. The Mach-Zehnder modulator may also comprise an output power divider, wherein the first and the second control electrode arrangement is arranged between the first and the second high frequency electrode arrangement and the output power divider. It is further noted that the first and the second optical branch of the modulator may consist of a first and a second optical waveguide, respectively. However, it is also possible that the first and the second optical branch besides an optical waveguide comprises further components. In particular, the first and/or the second optical branch may comprise a sub-Mach-Zehnder modulator for realizing an IQ modulator used e.g. for QPSK (Quaternary Phase Shift Keying) modulation schemes. Such a Mach-Zehnder modulator thus comprises a parent Mach- Zehnder structure (outer MZ) comprising the first and the second optical branch and the two (child) Mach-Zehnder modulators. Several optical high-order modulation formats can be realized as well with the IQ-modulator. IQ modulators may also comprise an input power divider dividing an incoming optical signal into a first signal propagating through the first optical branch and a second signal propagating through the second optical branch. The first and the second control electrode arrangement may then be arranged between the input power divider and the sub-Mach-Zehnder modulators. The invention also relates to an optical circuit comprising a Mach-Zehnder modulator as described above. Furthermore, the invention is related to a method of operating a Mach-Zehnder modulator as described above, comprising the steps of
- supplying a first DC voltage to the first control electrode of one of the control electrode arrangements, the first DC voltage creating a phase shift of an optical signal propagating through the corresponding optical branch and a change of the absorption of this optical branch, and
- supplying a second voltage to the other branch electrode arrangement in such a way that
- a change of the absorption of the corresponding branch is created that compensates the change of the absorption of the other optical branch created by the first voltage, or - a change of absorption of the corresponding optical branch is created that differs from the change of absorption created by the first voltage and creates a phase shift of an optical signal propagating through the corresponding optical branch that equals the phase shift induced by the first voltage in the other optical branch. Embodiments of the invention are described hereinafter with reference to the drawings, which show: a simulated optical transmission of a Mach-Zehnder modulator dependent on an alternating voltage applied between high frequency electrode arrangements of the modulator; the optical transmission of the modulator of Figure 1 A after a conventional phase correction was carried out; the absorption and the phase shift created in an optical waveguide using a short and a long control electrode, respectively; a Mach-Zehnder modulator according to an embodiment of the invention; the optical transmission of the Mach-Zehnder modulator of Figure 3 after a phase correction was carried out; a Mach-Zehnder modulator according to another embodiment of the invention; and
Fig. 6A, 6B further examples of the transmission of a MZI modulator according to the invention. Figure 1 A shows a typical transmission curve (the output intensity) of a Mach-Zehnder modulator, wherein the output intensity is shown on a logarithmic scale (y-axis) relative to an alternating voltage (x-axis, amplitude of the alternating voltage) applied between a first and a second high frequency electrode arrangement of the modulator.
The minima of the transmission curve represent possible working points of the modulator. For example, one of the potential working points (at about -1 V, denominated "WP" in Fig. 1 A) is shifted to negative voltages relative to the zero voltage point. Thus, for obtaining efficient operation of the modulator, the transmission curve has to be shifted to the right in order to shift the minimum towards the zero voltage point. This can be achieved by introducing a phase shift in one of the optical branches of the modulator by means of an additional phase shift electrode. The resulting transmission curve is shown in Figure 1 B, wherein the working point WP has been shifted on the zero voltage point. It is noted that instead of a minimum of the transmission function other working points could be used, e.g. a 3 dB point located halfway between a minimum and an adjacent maximum. It is noted that the different amplitudes of the relative minima and the relative maxima of the transmission curve are due to the voltage dependence of the phase and the absorption change. For creating the phase shift a long phase shift electrode may be used instead of a short electrode since the longer the phase shift electrode, the lower an undesired absorption associated with the phase shift as illustrated in Figure 2. That Figure depicts the absorption versus the phase shift created in an optical waveguide using an exemplary short electrode (having a length of 50 μηι, dashed-dotted line) and an exemplary long phase shift electrode (500 μηι, continuous line), respectively.
As shown in Fig. 2, the absorption-phase shift behavior of the longer electrode differs considerably from the behavior of the shorter electrode. The different behavior results from the different voltage dependency of the phase shift and the absorption.
More particularly, the phase shift φ generated in the optical waveguide by applying a voltage V to the optical waveguide using an electrode with an active length Lact can be approximated by the following polynomial (pi and p2 being suited coefficients): φ = p1V + p2V2) - Lact On the other hand, the absorption a of the optical waveguide created by applying the voltage V to the optical wave guide can be approximated by the following potential function (ai , a2 being suited coefficients):
a = (αι α2■ I act
Thus, because of the different dependency of the absorption and the phase shift on the applied voltage, an undesired absorption change created by a phase shift electrode in one of the modulator branches can be equalized by inducing an identical absorption in the other modulator branch, i.e. by using a compensation electrode whose length is shorter than the length of the phase shift electrode of the other modulator branch. Similarly, a phase shift might be compensated and different absorptions of the modulator branches may be generated.
Figure 3 shows a Mach-Zehnder modulator 1 (MZI modulator) according to the invention capable of compensating an undesired absorption change occurring in one of its optical branches caused by inducing a phase shift in that modulator branch. The modulator 1 comprises a first and a second optical branch 1 1 , 12 formed by a first and a second optical waveguide 1 1 1 , 121 . Further, the MZI modulator 1 comprises an input waveguide 13 via which light can be coupled into the modulator 1 . The input waveguide 13 is coupled to a power divider 14 in the form of an MMI that comprises two output ports connected to the first and the second optical waveguide 1 1 1 , 121 , respectively. An output section of modulator 1 comprises an output MMI 15 that connects the optical waveguides 1 1 1 , 121 to an output waveguide 16.
The first modulator branch 1 1 further comprises a first alternating voltage electrode arrangement 1 12 and similarly the second branch 12 comprises a second alternating voltage electrode arrangement 122. Both, the first and the second alternating voltage electrode electrode arrangement 1 12, 122 comprise a high frequency electrode arrangement in the form of a first and a second travelling wave electrode 1 13, 123, respectively. A high bit rate signal (a voltage having frequency components up to e.g. at least 40 GHz) will be supplied to the travelling wave electrode 1 13, 123 which is converted into a high bit rate optical signal available at an output port of the output MMI 15 and thus coupled into output optical waveguide 16. The travelling wave electrodes 1 13, 123 each comprise a section that is arranged on top of the optical waveguides 1 1 1 , 121 .
Moreover, the Mach-Zehnder modulator 1 comprises a first and the second control electrode arrangement 1 14, 124, wherein each one of the control electrode arrangement 1 14, 124 consists of a first control electrode in the form of a phase shift electrode 1 15, 125 and a second control electrode in the form of a separate compensation electrode 1 16, 126 arranged on the optical waveguides 1 1 1 , 121 , respectively. The compensation electrodes 1 16, 126 are arranged in a distance (along the optical waveguides 1 1 1 , 121 ) from the phase shift electrodes 1 15, 125, wherein the length of the compensation electrodes 1 16, 126 (measured along the first and the second optical waveguide 1 1 1 , 121 ) is shorter than the length of the corresponding phase shift electrode 1 15, 125.
Further, the control electrode arrangements 1 14, 124 are arranged between the input MMI 14 and the travelling wave electrodes 1 13, 123. Both, the first and the second control electrode arrangement 1 14, 124 are arranged in distance from the travelling wave electrodes, i.e. there is a gap between the electrode arrangements 1 14, 124 and the corresponding travelling wave electrodes 1 13, 123. In particular, a DC voltage source (not shown) is connected to the control electrode arrangements 1 14, 124, wherein a high frequency voltage source is connected to the travelling wave electrodes 1 13, 123. The operation of the control electrode arrangements 1 14, 124 is as follows: Depending on the position of a suited worked point of MZI modulator 1 (such as the working point WP in Fig. 1 A), a phase shift has to be introduced into the first or into the second optical branch 1 1 , 12 of the modulator 1 in order to shift the working point towards the zero voltage point. For this, a (first) DC voltage is applied to either the phase electrode 1 15 of the first control electrode arrangement 1 14 or the phase electrode 125 of the second control electrode arrangement 124. Applying the first voltage to phase shift electrode 1 15 or 125 also creates an undesired change (in particular an increase) of the absorption in the corresponding optical modulator branch 1 1 , 12. This absorption change is compensated or at least thwarted by supplying a (second) DC voltage to the compensation electrode of the respective other modulator branch, i.e. by supplying the second voltage to the compensation electrode 126 of the second control electrode arrangement 124 if the first (phase shifting) voltage is applied to the phase shift electrode 1 15 of the first control electrode arrangement 1 14 or by supplying the second voltage to the compensation electrode 1 16 of the first control electrode arrangement 1 14 if the first (phase shifting) voltage is applied to the phase shift electrode 125 of the second control electrode arrangement 124.
Thus, a longer electrode (one of the phase shift electrodes 1 15, 125) is used to create a phase shift, while a shorter electrode (one of the compensation electrodes 1 16, 126) is used to compensate the undesired absorption increase as explained above with respect to Fig. 2. It is noted that the invention is not restricted to the control electrode arrangements (comprising both a control and a compensation electrode) shown in Fig. 3. Rather, each one of the control electrode arrangements may comprise a single electrode only, wherein the lengths of the electrode of the first control arrangement may be different from the length of the electrode of the second control arrangement. Further, it is also conceivable that no phase shift / compensation electrodes in addition to the travelling wave electrodes are provided. Rather, the phase shift and the absorption compensation may be carried out by applying suited DC voltages to the travelling wave electrodes.
The MZI modulator 1 may be a semiconductor device, wherein the optical waveguides 1 1 1 , 1 12 may comprise a semiconductor material (e.g. a quaternary material or a multi-quantum well) whose refractive index changes by applying a voltage. The basic optical and electrical layout of the modulator may be designed as described in the article "Travelling wave Mach- Zehnder modulators", Prosyk, K. et al., International Conference on Indium Phosphide and Related Materials (IPRM), 2013, p. 1 -2 already mentioned above, or in the publication "45 GHz Bandwidth Travelling Wave Electrode Mach-Zehnder Modulator with Integrated Spot Size Converter", D. Hoffmann, Proceedings International Conference on Indium Phosphide and Related Materials, p. 585, 2004, wherein the content of these articles in respect to the principle optical and electrical design of the Mach-Zehnder modulator arrangement is incorporated by reference herewith.
It is further noted that the control electrode arrangements 1 14, 124 could also be operated in such a way that a differential absorber is created. According to this embodiment, the phase shift electrode of one of the control electrode arrangements 1 14, 124 and the compensation electrode of the other one of the control electrode arrangements 1 14, 124 is used to create equal phase shifts but different absorptions in the optical modulator branches 1 1 , 12. Of course, it is also possible that the control electrode arrangements 1 14, 124 are arranged in the rear region of the modulator, i.e. between the travelling wave electrodes 1 13, 123 and the output MMI 15. It is also conceivable that (front) control electrode arrangements are arranged between the input MMI 15 and the travelling wave electrodes 1 13, 123 and additional (rear) control electrode arrangements are provided between the travelling wave electrodes 1 13, 123 and the output MMI 15. It is also noted that according to Fig. 3, the phase shift electrodes 1 15, 125 are arranged between the input MMI 14 and the compensation electrodes 1 16, 126. However, it is of course also possible to change the order of the phase shift and the compensation electrodes such that the compensation electrodes 1 16, 126 are arranged between the input MMI 14 and the phase shift electrodes 1 15, 125.
Figure 4 shows a simulation of the output of the modulator shown in Figure 3 after correcting the working point by introducing a phase shift using one of the phase shift electrodes 1 15, 125 and compensating the absorption by applying a voltage to one of the compensation electrodes 1 16, 126. The working point WP is shifted onto the zero voltage point, while the output intensity at the zero voltage point is considerably lower relative to the non-compensated case (see Fig. 1 B). Thus, the extinction of the modulator drastically improves.
Figure 5 depicts a MZI modulator 1 ' according to another embodiment of the invention. Unlike the MZI modulator illustrated in Fig. 3, the modulator is an IQ modulator. That is, the optical branches 1 1 ', 12' of the modulator do not consist of optical waveguides 1 1 1 ', 121 ' only, but additionally comprise sub-MZI modulators 10, 20.
For example, the sub-MZI modulators 10, 20 are configured as the modulator shown in Fig. 3. Thus, each one of the optical branches 1 1 ', 12' of IQ modulator 1 ' comprises two modulator branches. Accordingly, the first and the second alternating voltage electrode arrangement 1 12', 122' of IQ modulator 1 ' each has a high frequency electrode arrangement 1 13', 123' (each of them comprising the two travelling wave electrodes of sub-MZI modulators 10, 20) and in addition comprises the control electrode arrangements of the corresponding sub-MZI modulators 10, 20.
Further, IQ modulator 1 ' comprises a first and a second control electrode arrangement 1 14', 124' arranged on top of the optical waveguides 1 1 1 ', 121 ' and between in input power divider 14' and the sub-MZI modulators 10, 20, respectively. The control electrode arrangements 1 14', 124' each consists of a first control electrode in the form of a phase shift electrode 1 15', 125' and a second control electrode in the form of a compensation electrode 1 16', 126', the compensation electrodes 1 16', 126' being shorter than the phase shift electrodes 1 15', 125'. A first DC voltage will be applied to one of the phase shift electrodes 1 15', 125' for creating a phase shift in one of the optical branches 1 1 ', 12' and a second DC voltage can be applied to one of the compensation electrodes 1 16', 126' of the other optical branch as set forth above with respect to Fig. 3. It is noted that the sub-MZI modulators 10, 20 do not necessarily have to be designed as the modulator shown in Fig. 3. Rather, other types of sub-MZI modulators could be used that do not comprise a control electrode arrangement such that the phase control and absorption compensation is carried out by the control electrode arrangement 1 14', 124' of the IQ modulator 1 '.
It is further noted that the MZI modulator according to the invention may be operated as an optical duobinary component. This operation uses three working points of the transmission curve such as the points "-Γ, "0" and "+1 " illustrated in Figures 6A (linear plot of the transmission curve) and 6B (logarithmic plot of the transmission curve). Using the MZI modulator according to the invention on the one hand permits the transmission curve to be shifted in such a way that a minimum ("0") is located at the zero voltage point as set forth above. On the other hand, the MZI modulator according to the invention allows the amplitude of the transmission curve at the maxima "-1 ", "+1 " adjacent the minimum "0" to be adapted such that they assume essentially the same value.

Claims

ms
An electro-optic Mach-Zehnder modulator, comprising
- a first and a second optical branch (1 1 , 1 1 ', 12, 12');
- a first alternating voltage electrode arrangement (1 12, 1 12') for applying an alternating voltage across the first optical branch (1 1 , 1 1 ');
- a second alternating voltage electrode arrangement (122, 122') for applying an alternating voltage across the second optical branch (12, 12');
- a first control electrode arrangement (1 14, 1 14') separate from the first alternating voltage electrode arrangement (1 12, 1 12') and for supplying a DC voltage across the first optical branch (1 1 , 1 1 ');
- a second control electrode arrangement (124, 124') separate from the second alternating voltage electrode arrangement (122, 122') and for supplying a DC voltage across the second optical branch (12, 12'), wherein
- the first control electrode arrangement (1 14, 1 14') and/or the second control electrode arrangement (124, 124') comprises a first control electrode (1 15, 1 15', 125, 125') and a second control electrode (1 16, 1 16', 126, 126'), characterized in that the length of the first control electrode (1 15, 1 15', 125, 125') is different from the length of the second control electrode (1 16, 1 16', 126, 126').
The Mach-Zehnder modulator as claimed in claim 1 , wherein the first alternating voltage electrode arrangement (1 12, 1 12') comprises a first high frequency electrode (1 13, 1 13') and the second alternating voltage electrode arrangement (122, 122') comprises a second high frequency electrode (123, 123').
The Mach-Zehnder modulator as claimed in claim 2, wherein the first high frequency electrode (1 13, 1 13') is a first travelling wave electrode and the second high frequency electrode (123, 123') is a second travelling wave electrode.
The Mach-Zehnder modulator as claimed in one of the preceding claims, wherein a first and the second DC voltage is supplied to the first and the second control electrode arrangement (1 14, 1 14', 124, 124'), respectively, in such a way that the length of interaction between the first voltage and an optical wave propagating through the corresponding optical branch (1 1 , 1 1 ', 12, 12') is different from the length of interaction between the second voltage and an optical wave propagating through the optical branch (1 1 , 1 1 ', 12, 12') to which the second voltage is supplied to.
5. The Mach-Zehnder modulator as claimed in one of the preceding claims, wherein
- the first control electrode arrangement (1 14, 1 14') comprises a first control electrode (1 15, 1 15') and a second control electrode (1 16, 1 16'), the length of the first control electrode (1 16, 1 16') being different from the length of the second control electrode (1 15, 1 15'); and
- the second control electrode arrangement (124, 124') comprises a first control electrode (125, 125') and a second control electrode (126, 126'), the length of the first control electrode (126, 126') being different from than the length of the second control electrode (125, 125').
6. The Mach-Zehnder modulator as claimed in one of the preceding claims, further comprising an input power divider (14, 14'), wherein the first and the second control electrode arrangement (1 14, 1 14', 124, 124') is arranged between the input power divider (14, 14') and the first and the second high frequency electrode arrangement (1 13, 1 13', 123, 123').
7. The Mach-Zehnder modulator as claimed in one of the claims 1 to 5, further comprising an output power divider (15, 15'), wherein the first and the second control electrode arrangement (1 14, 1 14', 124, 124') is arranged between the first and the second high frequency electrode arrangement (1 13, 1 13', 123, 123') and the output power divider (15, 15'). 8. The Mach-Zehnder modulator as claimed in one of the preceding claims, wherein the first and/or the second optical branch (1 1 , 1 1 ', 12, 12') of the Mach-Zehnder modulator (1 , 1 ') comprises a sub-Mach-Zehnder modulator (10, 20).
9. The Mach-Zehnder modulator as claimed in claim 8, further comprising an input power divider (14'), wherein the first and the second control electrode arrangement (1 14', 124') is arranged between the input power divider (14') and the corresponding sub-Mach- Zehnder modulator (10, 20).
10. The Mach-Zehnder modulator as claimed in one of the preceding claims, wherein the first control electrode (1 15, 1 15', 125, 125') and/or the second control electrode (1 16, 1 16',
126, 126') are arranged on an optical waveguide (1 1 1 , 1 1 1 ', 121 , 121 ') of the first and the second optical branch (1 1 , 1 1 ', 12, 12'), respectively.
11. Optical circuit comprising a Mach-Zehnder modulator according to one of the preceding claims.
12. A method for operating a Mach-Zehnder modulator according to one of the preceding claims as far as dependent on claim 5, wherein a first DC voltage is supplied to the first control electrode (115, 115', 125, 125') of one of the control electrode arrangements (114, 114', 124, 124'), the first DC voltage creating a phase shift of an optical signal propagating through the corresponding optical branch (11, 11', 12, 12') and a change of the absorption of this optical branch (11 , 11 ', 12, 12'), characterized by supplying a second DC voltage to the other control electrode arrangement (114, 114', 124, 124') in such a way that
- a change of the absorption of the corresponding optical branch (11, 11', 12, 12') is created that compensates the change of the absorption of the other optical branch (11, 11', 12, 12') created by the first voltage, or
- a change of absorption of the corresponding optical branch (11 , 11 ', 12, 12') is created that differs from the change of absorption of the other optical branch (11, 11', 12, 12') created by the first voltage and creates a phase shift of an optical signal propagating through the corresponding optical branch (11, 11', 12, 12') that equals the phase shift induced by the first voltage in the other optical branch (11, 11', 12, 12').
PCT/EP2014/057318 2014-04-10 2014-04-10 Mach-zehnder modulator and method for operating a mach-zehnder modulator WO2015154813A1 (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017198908A (en) * 2016-04-28 2017-11-02 住友大阪セメント株式会社 Optical transmitter and optical modulator
WO2017188295A1 (en) * 2016-04-28 2017-11-02 住友大阪セメント株式会社 Optical modulator
JP2017198868A (en) * 2016-04-28 2017-11-02 住友大阪セメント株式会社 Optical modulator
JP2018077545A (en) * 2018-02-08 2018-05-17 住友大阪セメント株式会社 Optical transmitter

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5886807A (en) * 1997-01-24 1999-03-23 California Institute Of Technology Traveling-wave reflective electro-optic modulator
US5991471A (en) * 1996-11-07 1999-11-23 Nortel Networks Corporation Configurable chirp mach-zehnder optical modulator
EP1596246A1 (en) * 2004-05-13 2005-11-16 Fujitsu Limited Modulator for an optical transmitter, push-pull driven modulator, and an asymmetric modulator
US20070217733A1 (en) * 2006-03-16 2007-09-20 Hiroshi Wada Mach-Zehnder type semiconductor device and method of controlling the same
EP1923739A1 (en) * 2006-11-14 2008-05-21 Fujitsu Ltd. Differential M-phase-shift optical modulator
US20110064351A1 (en) * 2009-07-16 2011-03-17 Furukawa Electric Co., Ltd. Optical phase modulator and optical phase modulating device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5991471A (en) * 1996-11-07 1999-11-23 Nortel Networks Corporation Configurable chirp mach-zehnder optical modulator
US5886807A (en) * 1997-01-24 1999-03-23 California Institute Of Technology Traveling-wave reflective electro-optic modulator
EP1596246A1 (en) * 2004-05-13 2005-11-16 Fujitsu Limited Modulator for an optical transmitter, push-pull driven modulator, and an asymmetric modulator
US20070217733A1 (en) * 2006-03-16 2007-09-20 Hiroshi Wada Mach-Zehnder type semiconductor device and method of controlling the same
EP1923739A1 (en) * 2006-11-14 2008-05-21 Fujitsu Ltd. Differential M-phase-shift optical modulator
US20110064351A1 (en) * 2009-07-16 2011-03-17 Furukawa Electric Co., Ltd. Optical phase modulator and optical phase modulating device

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
D. HOFFMANN: "45 GHz Bandwidth Travelling Wave Electrode Mach-Zehnder Modulator with Integrated Spot Size Converter", PROCEEDINGS INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS, 2004, pages 585, XP010815073, DOI: doi:10.1109/ICIPRM.2004.1442793
PROSYK, K. ET AL.: "Travelling wave Mach-Zehnder modulators", INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS (IPRM, 2013, pages 1 - 2, XP032436943, DOI: doi:10.1109/ICIPRM.2013.6562568

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017198908A (en) * 2016-04-28 2017-11-02 住友大阪セメント株式会社 Optical transmitter and optical modulator
WO2017188295A1 (en) * 2016-04-28 2017-11-02 住友大阪セメント株式会社 Optical modulator
JP2017198868A (en) * 2016-04-28 2017-11-02 住友大阪セメント株式会社 Optical modulator
JP2018077545A (en) * 2018-02-08 2018-05-17 住友大阪セメント株式会社 Optical transmitter

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