Antenna-integrated electro-optical modulator

Abstract

The purpose of the present invention is to provide an antenna-integrated electro-optical modulator capable of actively controlling the beam direction of a wireless signal received by an antenna electrode.　An antenna-integrated electro-optical modulator (1) comprises: an optical waveguide (10) for transmitting an optical signal; a plurality of antenna electrodes (20) for receiving a wireless signal for modulating the optical signal with an electro-optical effect; and a voltage circuit (60) for imparting respectively different DC voltages to the antenna electrodes (20).

Description

Antenna-integrated electro-optic modulator

[0001] The present invention relates to an electro-optic modulator with an integrated antenna.

[0002] Patent Document 1 discloses a radio signal receiving and separating device that converts a plurality of radio signals into optical signals by using an electro-optic modulation effect and separates the signals, the radio signal receiving and separating device comprising a plurality of optical waveguides that transmit the optical signals, an antenna that receives the plurality of radio signals, and a plurality of modulation electrodes connected to the antenna, the plurality of modulation electrodes being arranged in close proximity to each of the plurality of optical waveguides so that the optical signals are modulated by the radio signals, and each of the plurality of optical waveguides having a polarization inversion structure with a constant period in the propagation direction of the optical signals, with the polarization inversion periods being different from each other.

[0003] JP 2009-60183 A

[0004] The radio signal receiving and separating device described in Patent Document 1 is said to be capable of detecting only radio signals having an incident angle or frequency specified by the polarization inversion period, each of which has a plurality of optical waveguides having different polarization inversion periodic structures.

[0005] However, the radio signal receiving and separating device described in Patent Document 1 requires one optical waveguide to obtain one beam, and therefore, in order to obtain multiple beams, the number of optical waveguides increases, making the structure more complex.

[0006] The present invention has been made to solve the above problems, and aims to provide an antenna-integrated electro-optical modulator that can actively control the beam direction of a radio signal received by an antenna electrode.

[0007] In a first aspect, the antenna-integrated electro-optical modulator of the present invention comprises an optical waveguide for transmitting an optical signal, a plurality of antenna electrodes for receiving radio signals for modulating the optical signal using the electro-optical effect, and a voltage circuit for applying different DC voltages to each of the antenna electrodes.

[0008] In a second aspect, the antenna-integrated electro-optical modulator of the present invention comprises an optical waveguide for transmitting an optical signal, a plurality of antenna electrodes for receiving radio signals for modulating the optical signal using the electro-optical effect, a plurality of external connection terminals for receiving different DC voltages, and a plurality of wires connecting each external connection terminal to each of the antenna electrodes.

[0009] According to the present invention, it is possible to provide an antenna-integrated electro-optic modulator capable of actively controlling the beam direction of a radio signal received by an antenna electrode.

[0010] Fig. 1 is a schematic diagram showing an example of an antenna-integrated electro-optical modulator of the present invention. Fig. 2 is a plan view showing a portion of the antenna-integrated electro-optical modulator shown in Fig. 1. Fig. 3 is a plan view showing an example of an electrode arrangement in an antenna-integrated electro-optical modulator according to an embodiment within the scope of the present invention. Fig. 4 is an enlarged view of the antenna electrode in Fig. 3. Fig. 5 is an example of the angle dependence of receiving sensitivity when no DC voltage is applied to the antenna electrode. Fig. 6 is an example of the angle dependence of receiving sensitivity when a DC voltage is applied to the antenna electrode.

[0011] The antenna-integrated electro-optic modulator of the present invention will be described below. Note that the present invention is not limited to the following configuration, and may be modified as appropriate without departing from the gist of the present invention. Furthermore, a combination of multiple individual preferred configurations described below also constitutes the present invention.

[0012] The antenna-integrated electro-optic modulator of the present invention is used, for example, in a wireless communication system.

[0013] Wireless communication systems use a technology called Radio over Fiber (RoF), which transmits waveform information of wireless signals over optical fibers. Known types of RoF include Digital Radio over Fiber (D-RoF) and Analog Radio over Fiber (A-RoF).

[0014] D-RoF is a technology that converts the waveform information of a radio signal into a digital signal before transmitting it over optical fiber. However, D-RoF is thought to have the following problems: (1) Because the transmission capacity required for transmitting digital signals is large, optical communications cannot keep up with next-generation high-capacity communications. (2) Because various processes such as DSP (Digital Signal Processing) are performed in RUs (Radio Units), increasing the number of RUs to achieve high-frequency band wireless communications increases costs accordingly. (3) The power consumption required for processing in RUs is large.

[0015] In contrast, A-RoF is a technology that transmits the waveform information of a radio signal as an analog signal via optical fiber. Unlike D-RoF, A-RoF does not require various processes to be performed in the RU, such as DSP. Therefore, in order to solve the above-mentioned problems that can be considered with D-RoF, studies are being conducted to adopt A-RoF instead of D-RoF and consolidate the functions of the RU into a Distributed Unit (DU) or Centralized Unit (CU), thereby simplifying the RU and reducing the cost and power consumption associated with the RU.

[0016] The antenna-integrated electro-optic modulator of the present invention is preferably used in a wireless communication system employing A-RoF. More specifically, the antenna-integrated electro-optic modulator of the present invention is preferably used as a modulator in an RU that modulates an optical signal by electro-optic effect using a radio signal received by an antenna to obtain an analog signal transmitted from the RU to a DU via an optical fiber.

[0017] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, and other scales may differ from those of the actual product. In the drawings, the same or equivalent parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and duplicate explanations will be omitted.

[0018] In this specification, terms indicating the relationship between elements (e.g., "perpendicular," "parallel," "orthogonal," etc.) and terms indicating the shape of elements are not expressions that only express a strict meaning, but are expressions that also include a range of substantial equivalence, for example, a difference of about a few percent.

[0019] Fig. 1 is a schematic diagram showing an example of an antenna-integrated electro-optical modulator of the present invention, and Fig. 2 is a plan view showing a part of the antenna-integrated electro-optical modulator shown in Fig. 1.

[0020] 1 and 2 includes an optical waveguide 10 for transmitting an optical signal, and a plurality of antenna electrodes 20 for receiving a radio signal for modulating the optical signal by the electro-optic effect. The antenna-integrated electro-optic modulator 1 preferably further includes a substrate 30.

[0021] For example, laser light, which serves as an optical signal, is transmitted via an optical fiber to the optical waveguide 10. The laser light is a light wave that serves as a carrier, and for example, a laser with a wavelength of 1.55 μm is used.

[0022] 1 and 2, one optical waveguide 10 is provided in the antenna-integrated electro-optical modulator 1. The number of optical waveguides 10 is not particularly limited, and may be one, or two or more.

[0023] 1 and 2, the optical waveguide 10 extends linearly when viewed from the main surface side of the substrate 30, but it may extend in a curved manner when viewed from the main surface side of the substrate 30. In this case, the optical waveguide 10 may be bent in a broken line or curved line.

[0024] The optical waveguide 10 is preferably made of an electro-optic material.

[0025] When an electric field is applied to an electro-optic material, the refractive index of the material changes and the phase of the light changes, thereby exhibiting an electro-optic effect.

[0026] The optical waveguide 10 is preferably made of an electro-optical polymer containing electro-optical molecules as the electro-optical material.

[0027] An electro-optic polymer is a polymer that is capable of exhibiting an electro-optic effect.

[0028] Examples of electro-optical polymers include guest-host electro-optical polymers in which a matrix polymer and electro-optical molecules are mixed, side-chain electro-optical polymers in which electro-optical molecules are covalently bonded to the side chains of a base polymer, main-chain electro-optical polymers in which electro-optical molecules are covalently bonded to the main chain of a base polymer, cross-linked electro-optical polymers in which cross-linking occurs between matrix polymers or between base polymers, or between a matrix polymer or base polymer and electro-optical molecules, and molecular glass electro-optical polymers.

[0029] The matrix polymer is a polymer that serves as a base for the electro-optic polymer, and includes an organic polymer that serves as a host for the guest-host electro-optic polymer.

[0030] The base polymer is a polymer that forms the basic skeleton of the electro-optic polymer, and includes an organic polymer that forms the main chain of a polymer in a side-chain electro-optic polymer, a main-chain electro-optic polymer, or a cross-linked electro-optic polymer.

[0031] The matrix polymer and base polymer are preferably transparent polymers that do not scatter light in order to be used as optical materials, and examples thereof include (meth)acrylate polymers, polyamides, polyimides, polycarbonates, polydicyclopentanyl methacrylate, polyadamantyl methacrylate, cycloolefin polymers, cycloolefin copolymers, polynorbornenes, polystyrenes, polyethylenes, polymethylpentenes, polypropylenes, polyvinyl alcohols, polyethylene terephthalates, polysulfones, polyethersulfones, polyesters, polyolefins, polyphenylene sulfide, polyureas, silicon-based resins, epoxy-based resins, fluororesins, etc. As the matrix polymer and base polymer, only one type of these organic polymers may be used, or multiple types may be used in combination.

[0032] Electro-optic molecules are compounds capable of exhibiting an electro-optic effect.

[0033] The electro-optic molecule is preferably a compound having a conjugated chemical structure and further having an electron-donating group and an electron-withdrawing group in the molecule.

[0034] Examples of conjugated chemical structures include aromatic compounds such as benzene, naphthalene, anthracene, perylene, biphenyl, indene, and stilbene; heterocyclic compounds such as furan, pyran, pyrrole, imidazole, pyrazole, thiophene, thiazole, pyridine, pyridazine, pyrimidine, pyrazine, quinoline, and coumarin; and compounds in which these compounds are bonded to each other via a carbon-carbon unsaturated bond or a nitrogen-nitrogen unsaturated bond.

[0035] Examples of the electron-donating group include an amino group which may be substituted with an alkyl group, an aryl group, or an acyl group, an alkoxy group, an allyloxy group, and a thioether group.

[0036] Examples of the electron-withdrawing group include a nitro group, a cyano group, a dicyanovinyl group, a tricyanovinyl group, a halogen atom, a carbonyl group, a sulfone group, a perfluoroalkyl, a tricyanovinylfuran, and a tricyanofuran.

[0037] The optical waveguide 10 is made of an electro-optical material such as lithium niobate (LiNbO ３ ), lithium tantalate (LiTaO ３ ), potassium titanate phosphate (KTiOPO ４ The dielectric layer may be made of a ferroelectric material having optical anisotropy, such as KTP.

[0038] Each of the plurality of antenna electrodes 20 receives a radio signal for modulating the optical signal transmitted through the optical waveguide 10 by the electro-optic effect.

[0039] The antenna electrode 20 is preferably provided on the main surface of the substrate 30 .

[0040] 1 and 2, three antenna electrodes 20 are provided. The number of antenna electrodes 20 is not limited to three as long as there is a plurality of antenna electrodes 20, and may be two, or four or more.

[0041] The antenna electrodes 20 are preferably arranged along the optical waveguide 10, and more preferably arranged at equal intervals along the optical waveguide 10. For example, the pitch of the antenna electrodes 20 (L in FIG. 2) may be set to 1 / 2. Ａ It is preferable that the lengths of the antenna electrodes 20 are equal to each other. Ａ This includes not only the case where they are completely equal, but also the case where they are substantially equal, for example, with a difference of about a few percent.

[0042] The shape of the antenna electrodes 20 is not particularly limited, and some or all of them may be different, but it is preferable that they are the same. For example, it is preferable that all of the antenna electrodes 20 have the same length (the length indicated by L in FIG. 2 ). The length L of the antenna electrodes 20 here refers to the length in the direction in which the optical waveguide 10 extends. Note that the term "same length" does not only refer to cases in which the lengths L of the antenna electrodes 20 are completely equal, but also includes cases in which they are substantially equal, for example, with a difference of about a few percent. As shown in FIG. 2 , it is preferable that all of the antenna electrodes 20 have the same length not only in the direction in which the optical waveguide 10 extends, but also in the direction perpendicular to the direction in which the optical waveguide 10 extends.

[0043] As shown in Figures 1 and 2, each antenna electrode 20 is composed of, for example, two planar electrodes 21 and 22 adjacent to each other in a direction perpendicular to the extension direction of the optical waveguide 10, and a gap is formed between the planar electrodes 21 and 22 (at the center of the antenna electrode 20 in Figures 1 and 2). For example, the planar electrodes 21 and 22 are both rectangular and arranged symmetrically across the gap. The gap distance is, for example, 5 µm. The shorter the gap distance, the stronger the electric field can be near the sides where the planar electrodes 21 and 22 face each other.

[0044] Examples of materials constituting the antenna electrode 20 include gold, silver, copper, tin, chromium, aluminum, titanium, alloys containing at least one of these metals, and oxides containing at least one of these metals (e.g., indium tin oxide, indium zinc oxide, aluminum-doped zinc oxide, etc.). The materials constituting the antenna electrode 20 may be the same as or different from each other.

[0045] Preferably, the optical waveguide 10 is provided inside the substrate 30 so as to extend along the main surface of the substrate 30 .

[0046] The substrate 30 may be made up of only one layer, or may be made up of multiple layers.

[0047] The substrate 30 may include, for example, a support base 31 and an electro-optical layer 32 in this order toward the antenna electrode 20. In this case, the optical waveguide 10 is preferably provided between the support base 31 and the electro-optical layer 32. The antenna electrode 20 is preferably provided on the surface of the electro-optical layer 32 opposite to the support base 31.

[0048] The constituent material of the support substrate 31 may be, for example, an inorganic material such as silicon or glass, or an organic material such as a cycloolefin polymer or a cycloolefin copolymer. The support substrate 31 may contain only one type of these materials, or may contain multiple types of these materials.

[0049] It is preferable that at least the main surface of the support substrate 31 facing the antenna electrode 20 is made of a material with a low dielectric constant, such as a cycloolefin polymer. In this case, it is preferable that the optical waveguide 10 is provided on the main surface of the support substrate 31 facing the antenna electrode 20.

[0050] The support substrate 31 may be composed of only one layer, or may be composed of multiple layers.

[0051] The electro-optical layer 32 may be made of, for example, lithium niobate (LiNbO ３ ), lithium tantalate (LiTaO ３ ), potassium titanate phosphate (KTiOPO４ Examples of suitable ferroelectric materials include ferroelectric materials having optical anisotropy such as KTP.

[0052] The electro-optical layer 32 may be made up of only one layer, or may be made up of multiple layers.

[0053] The antenna-integrated electro-optical modulator 1 may further include a ground electrode (not shown).

[0054] The ground electrode may be provided on the main surface of the substrate 30 opposite to the main surface on which the plurality of antenna electrodes 20 are provided, or may be provided inside the substrate 30. In either case, the optical waveguide 10 is located between the ground electrode and the antenna electrode 20.

[0055] Examples of the constituent material of the ground electrode include gold, silver, copper, tin, chromium, aluminum, titanium, alloys containing at least one of these metals, and oxides containing at least one of these metals (e.g., indium tin oxide, indium zinc oxide, aluminum-doped zinc oxide, etc.). The constituent material of the ground electrode may be the same as or different from the constituent material of the antenna electrode 20.

[0056] The antenna-integrated electro-optic modulator 1 functions as a modulator that modulates an optical signal by the electro-optic effect using a radio signal received by the antenna electrode 20 in the following manner.

[0057] In the antenna-integrated electro-optical modulator 1, an optical signal is transmitted to the optical waveguide 10. Meanwhile, each of the multiple antenna electrodes 20 receives a radio signal. At this time, a resonance phenomenon occurring in the antenna electrode 20 increases the electric field, and an electro-optical effect occurs in the optical waveguide 10 passing through the location where this electric field is generated. When the electro-optical effect occurs in the optical waveguide 10, the refractive index of the optical waveguide 10 with respect to the optical signal transmitted to the optical waveguide 10 changes, causing a phase change in the optical signal according to the magnitude of the electric field. In this way, the antenna-integrated electro-optical modulator 1 modulates the optical signal transmitted to the optical waveguide 10 by the electro-optical effect using the radio signals received by the multiple antenna electrodes 20. In other words, the antenna-integrated electro-optical modulator 1 utilizes the electro-optical effect to directly superimpose the radio signals received by the multiple antenna electrodes 20 on the optical signal transmitted to the optical waveguide 10.

[0058] In the conventional configuration, the beam direction of the radio signal received by the antenna electrode 20 is completely determined by the arrangement of the antenna electrode 20, such as the pitch and length, and therefore it is impossible to change the beam direction.

[0059] In contrast, the antenna-integrated electro-optic modulator 1 is characterized in that different DC voltages (bias voltages) are applied to the respective antenna electrodes 20. Since the application of DC voltages causes a phase change in the optical signal, it is possible to change the beam direction of the radio signal received by the antenna electrodes 20 by changing the value of the DC voltage applied to each antenna electrode 20. Therefore, the beam direction can be actively controlled.

[0060] Specifically, as shown in Figures 1 and 2, the antenna-integrated electro-optical modulator 1 has a plurality of external connection terminals 40 for receiving different DC voltages, and a plurality of wirings 50 connecting each external connection terminal 40 to each antenna electrode 20.

[0061] 1, the antenna-integrated electro-optical modulator 1 includes a voltage circuit 60 for applying different DC voltages to each of the antenna electrodes 20. The voltage circuit 60 is connected to the external connection terminal 40, and a plurality of wirings 50 connect the voltage circuit 60 to each of the antenna electrodes 20.

[0062] 1 , the antenna-integrated electro-optical modulator 1 preferably further includes a controller 70 for receiving a control optical signal and controlling the voltage circuit 60. For example, the controller 70 receives a control optical signal from the RU of the base station device 100.

[0063] In A-RoF, it is desirable to remotely control the steering angle of the beam from the RU, and the above configuration makes this possible.

[0064] Furthermore, in the above configuration, when receiving beams in a plurality of directions, it is only necessary to add one optical fiber for transmitting a control optical signal, so the number of optical fibers can be reduced.

[0065] In the example shown in Figures 1 and 2, the antenna-integrated electro-optical modulator 1 further includes a plurality of external connection terminals 45 for connection to ground GND, and a plurality of wirings 55 connecting each of the external connection terminals 45 to ground GND.

[0066] 1 and 2 , when each antenna electrode 20 is composed of a planar electrode 21 and a planar electrode 22, a voltage circuit 60 is connected to an external connection terminal 40 to apply different DC voltages to each planar electrode 21, and multiple wirings 50 connect the voltage circuit 60 to each planar electrode 21. Meanwhile, ground GND is connected to an external connection terminal 45, and multiple wirings 55 connect ground GND to each planar electrode 22. The wirings 50 and 55 are preferably designed as high-impedance lines so that the electric field received by the antenna electrode 20 does not flow into the ground electrode 85 (see FIG. 3 ).

[0067] The planar electrodes 21 and 22 constituting the antenna electrode 20 are both provided on the main surface of the substrate 30 and are preferably on the same plane, but may be on different planes. For example, the planar electrode 21 may be provided on one main surface of the substrate 30, and the planar electrode 22 may be provided inside the substrate 30 or on the other main surface of the substrate 30.

[0068] The voltage circuit 60 includes, for example, a plurality of voltage dividing circuits whose resistance values ​​can be varied by a plurality of switch elements.

[0069] The controller 70 includes, for example, a light receiving element (such as a photodiode) that converts the control optical signal into a current signal, a current-voltage conversion element that converts the current signal into a voltage signal, and an integrated circuit (IC) that controls the DC voltage applied to each antenna electrode 20.

[0070] EXAMPLES Examples that more specifically disclose the antenna-integrated electro-optic modulator of the present invention are described below, but the present invention is not limited to these examples.

[0071] In the following example, the number of antenna electrodes is six, and the phase difference between the antenna electrodes is π / 3.

[0072] Fig. 3 is a plan view showing a schematic example of an electrode arrangement in an antenna-integrated electro-optic modulator according to an embodiment within the scope of the present invention, and Fig. 4 is an enlarged view of the antenna electrode in Fig. 3.

[0073] As shown in FIG. 3, each antenna electrode 20 and each DC voltage application electrode 80 are connected by a wire 50 , and each antenna electrode 20 and each ground electrode 85 are connected by a wire 55 .

[0074] In FIG. 3, the pitch L of the antenna electrode 20 Ａ is 4.8 mm.

[0075] In Figure 4, the length L of the antenna electrode 20 in the direction in which the optical waveguide (not shown) extends (Y direction) is 1.0 mm, the length of the antenna electrode 20 in the direction perpendicular to the direction in which the optical waveguide extends (X direction) is 1.9 mm, the gap distance is 5 μm, the width of the wiring 50 and wiring 55 is 40 μm, and the distance from the end face of the antenna electrode 20 to the wiring 50 or wiring 55 is 0.6 mm.

[0076] Other conditions are as follows:

[0077] Optical refractive index of the optical waveguide: 2.2 Overlap constant Γ indicating the degree of overlap between the resonant electric field generated by the electrode and the optical electric field in the optical waveguide: 0.8 Electro-optic constant r ３３ :33pm / V Light wavelength: 1550nm (1.55μm)

[0078] Transmission power: 0 dBm Transmission antenna gain: 16.5 dBi Communication distance: 1 m Electric field enhancement caused by resonance of antenna electrode: 800 Radio wave frequency: 28 GHz

[0079] Here, the total amount of phase change of the optical signal due to N antenna electrodes can be obtained by performing the following integration:

[0080]

[0081]

[0082] In the above formula, k ｍ is the wave number of the radio wave, k ｏｐ is the wave number of light, s is the antenna number, r is the electro-optic coefficient, Γ is the overlap coefficient, n ０ indicates the refractive index of light. In this case, the refractive index is considered to be the group refractive index.

[0083] Furthermore, δφ ｓ is the amount of phase delay required for each antenna electrode, and has a different value for each antenna electrode.

[0084] In this embodiment, the number of antenna electrodes is 6 and the phase difference between the antenna electrodes is π / 3. ｓ = 0, π / 3, 2π / 3, π, 4π / 3, 5π / 3. The phase is set with the antenna with s = 0 as the reference.

[0085] Fig. 5 shows an example of the angle dependency of the receiver sensitivity when no DC voltage is applied to the antenna electrode. Fig. 6 shows an example of the angle dependency of the receiver sensitivity when a DC voltage is applied to the antenna electrode. In Figs. 5 and 6, the horizontal axis represents the incident angle of the radio wave, which indicates the angle from the Z axis in the ZY plane shown in Fig. 3. On the other hand, the vertical axis represents the carrier-to-sideband ratio (CSR), which indicates the power of the first-order sideband relative to the power of the optical carrier. The smaller the CSR, the smaller the power difference between the optical carrier and the sideband, and therefore the higher the sensitivity.

[0086] 5 and 6, it can be seen that by applying different DC voltages to each antenna electrode, the point of maximum reception sensitivity of the main lobe (downward arrow), which was near the incident angle of 0 degrees, shifts to near -20 degrees. Figures 5 and 6 also show that the application of DC voltages also changes the position of the null point of reception sensitivity (upward arrow).

[0087] The change in phase of light due to a DC voltage can be expressed by the following formula.

[0088]

[0089]

[0090]

[0091] In the above formula, the I portion is the n of the lithium niobate constituting the optical waveguide. ０ ３ r ３３ Part II corresponds to the DC electric field calculated assuming that a DC voltage of 10 V is applied across a 5 μm gap between electrodes, part III corresponds to the length of the antenna electrode of 1 mm, and part IV corresponds to the wave number of light.

[0092] From the above, it is thought that a phase difference of π / 3 can be created by applying a DC voltage of approximately 10 V to the antenna electrode. The maximum phase difference of 5π / 3 requires a DC voltage five times that amount, approximately 50 V, but this is a voltage that can be output by a commercially available three-terminal regulator. Furthermore, by increasing the length of the antenna electrode, it is possible to create a phase difference with an even smaller DC voltage.

[0093] The present specification discloses the following:

[0094] <1> An antenna-integrated electro-optical modulator comprising: an optical waveguide for transmitting an optical signal; a plurality of antenna electrodes for receiving radio signals for modulating the optical signal using an electro-optical effect; and a voltage circuit for applying different DC voltages to each of the antenna electrodes.

[0095] <2> The antenna-integrated electro-optic modulator according to <1>, further comprising a controller that receives a control optical signal and controls the voltage circuit.

[0096] <3> The antenna-integrated electro-optical modulator according to <1> or <2>, further comprising a plurality of wirings connecting the voltage circuit and each of the antenna electrodes.

[0097] <4> An antenna-integrated electro-optical modulator comprising: an optical waveguide for transmitting an optical signal; a plurality of antenna electrodes for receiving radio signals for modulating the optical signal by an electro-optical effect; a plurality of external connection terminals for receiving different DC voltages; and a plurality of wirings for connecting each external connection terminal to each of the antenna electrodes.

[0098] <5> The antenna-integrated electro-optic modulator according to any one of <1> to <4>, wherein the antenna electrodes are arranged at equal intervals along the optical waveguide.

[0099] <6> The antenna-integrated electro-optic modulator according to any one of <1> to <5>, wherein the antenna electrodes have the same shape.

[0100] <7> The antenna-integrated electro-optic modulator according to any one of <1> to <6>, further comprising a substrate, wherein the optical waveguide is provided inside the substrate so as to extend along a main surface of the substrate.

[0101] <8> The antenna-integrated electro-optic modulator according to <7>, wherein the antenna electrode is provided on the main surface of the substrate.

[0102] <9> The antenna-integrated electro-optic modulator according to any one of <1> to <8>, wherein the optical waveguide is made of an electro-optic polymer containing electro-optic molecules as the electro-optic material.

[0103] REFERENCE SIGNS LIST 1 Antenna-integrated electro-optical modulator 10 Optical waveguide 20 Antenna electrode 21, 22 Planar electrode 30 Substrate 31 Support base material 32 Electro-optical layer 40, 45 External connection terminal 50, 55 Wiring 60 Voltage circuit 70 Controller 80 Electrode for applying DC voltage 85 Ground electrode 100 Base station device GND Ground L Ａ Pitch of the antenna electrode L Length of the antenna electrode

Claims

1. An antenna-integrated electro-optic modulator comprising: an optical waveguide for transmitting an optical signal; a plurality of antenna electrodes for receiving a radio signal for modulating the optical signal by an electro-optic effect; and a voltage circuit for applying a different DC voltage to each of the antenna electrodes.

2. The antenna-integrated electro-optic modulator according to claim 1, further comprising a controller for receiving a control optical signal and controlling the voltage circuit.

3. The antenna-integrated electro-optic modulator according to claim 1 or 2, further comprising a plurality of wirings connecting the voltage circuit and each of the antenna electrodes.

4. An antenna-integrated electro-optic modulator comprising: an optical waveguide for transmitting an optical signal; a plurality of antenna electrodes for receiving a radio signal for modulating the optical signal by an electro-optic effect; a plurality of external connection terminals for receiving different DC voltages; and a plurality of wirings connecting each of the external connection terminals and each of the antenna electrodes.

5. The antenna-integrated electro-optic modulator according to any one of claims 1 to 4, wherein the antenna electrodes are arranged at equal intervals along the optical waveguide.

6. The antenna-integrated electro-optic modulator according to any one of claims 1 to 5, wherein the shapes of the antenna electrodes are the same as each other.

7. The antenna-integrated electro-optic modulator according to any one of claims 1 to 6, further comprising a substrate, wherein the optical waveguide is provided inside the substrate so as to extend along the main surface of the substrate.

8. The antenna-integrated electro-optic modulator according to claim 7, wherein the antenna electrodes are provided on the main surface of the substrate.

9. The antenna-integrated electro-optic modulator according to any one of claims 1 to 8, wherein the optical waveguide is composed of an electro-optic polymer containing electro-optic molecules as an electro-optic material.

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