Optical modulator and optical transmission device using the same

Abstract

The present invention provides an optical modulator and an optical transmitting device using the optical modulator, in which the influence of leakage microwaves generated from a relay substrate provided with an electrical circuit element is reduced to achieve good modulation characteristics. The optical modulator includes: an optical modulation element including a plurality of signal electrodes, generating two modulated lights respectively modulated by two sets of electrical signals; a plurality of signal input terminals, inputting electrical signals; and a relay substrate, which is formed with a plurality of signal conductor patterns and a plurality of ground conductor patterns, and is configured to propagate the two sets of electrical signals respectively through two adjacent pairs of signal conductor patterns; and a frame, wherein at least one signal conductor pattern has at least one component mounting portion of a parallel circuit including at least a resistor and a capacitor, and the relay substrate has a metal body or a substrate removal portion connected to the ground conductor pattern, which is provided at a position sandwiching a portion of the signal conductor pattern downstream of the component mounting portion along the propagation direction of the electrical signal.

Description

Technical Field

[0001] The present invention relates to an optical modulator including a relay substrate for relaying propagation of an electric signal between a signal input terminal and a signal electrode of an optical modulation element, and an optical transmission device using the optical modulator. Background Art

[0002] In high-speed / large-capacity optical fiber communication systems, optical modulators equipped with waveguide-type optical modulators are often used. Among them, optical modulators using LiNbO3 (hereinafter also referred to as LN) with an electro-optical effect as a substrate can achieve optical modulation characteristics with low optical loss and wide bandwidth, and are therefore widely used in high-speed / large-capacity optical fiber communication systems.

[0003] The optical modulator using the LN substrate is provided with a Mach-Zehnder type optical waveguide and a signal electrode for applying a high-frequency electric signal as a modulation signal to the optical waveguide. Furthermore, these signal electrodes provided in the optical modulator are connected to a lead pin or a connector as a signal input terminal provided in the frame via a relay substrate provided in the frame of the optical modulator that accommodates the optical modulator. Thus, by connecting the lead pin or the connector as the signal input terminal to a circuit substrate equipped with an electronic circuit for causing the optical modulator to perform a modulation operation, the electric signal output from the electronic circuit is applied to the signal electrode of the optical modulator via the relay substrate.

[0004] The modulation methods in optical fiber communication systems have been influenced by the trend of increasing transmission capacity in recent years. Multi-value modulation such as Quadrature Phase Shift Keying (QPSK) or Dual Polarization-Quadrature Phase Shift Keying (DP-QPSK), or transmission formats that introduce polarization multiplexing in multi-value modulation have become mainstream. In addition to being used in backbone optical transmission networks, they are also gradually being introduced into urban networks.

[0005] An optical modulator that performs QPSK modulation (QPSK optical modulator) or an optical modulator that performs DP-QPSK modulation (DP-QPSK optical modulator) includes a plurality of Mach-Zehnder optical waveguides in a so-called nested structure, each of which includes at least one signal electrode. Therefore, these optical modulators include a plurality of signal electrodes, and the high-frequency electrical signals given to these signal electrodes cooperate to perform the DP-QPSK modulation operation. Specifically, the DP-QPSK modulator is configured to generate two modulated lights that are modulated by a pair of high-frequency electrical signals, respectively, and synthesize the two modulated lights to output as one modulated light.

[0006] In such an optical modulator, there may be a case where an electric circuit element such as an electric filter is mounted on a signal line formed on a relay substrate in order to improve high-frequency characteristics (Patent Documents 1 and 2).

[0007] Fig.18 2 is a plan view showing an example of the structure of a conventional optical modulator including a relay substrate on which such an electrical circuit element is mounted. The optical modulator 2200 includes, for example, an optical modulation element 2202 as a DP-QPSK modulator formed on an LN substrate, and a frame 2204 that accommodates the optical modulation element 2202. Here, the frame 2204 includes a housing 2214a and a cover 2214b. The optical modulator 2200 further includes an input optical fiber 2208 and an output optical fiber 2210, which are fixed to the housing 2214a and input / output light to / from the optical modulation element 2202.

[0008] The housing 2214a of the frame 2204 is further provided with four signal input terminals 2224a, 2224b, 2224c, and 2224d (hereinafter, also collectively referred to as signal input terminals 2224) for inputting high-frequency electrical signals for driving the optical modulation element 2202 from an external electronic circuit. Specifically, the signal input terminal 2224 is, for example, a central electrode of an electrical connector 2216a, 2216b, 2216c, and 2216d (hereinafter, also collectively referred to as an electrical connector 2216) which is a high-frequency coaxial connector. The high-frequency electrical signals input from each signal input terminal 2224 are respectively input to one end of four signal electrodes 2212a, 2212b, 2212c, and 2212d (hereinafter collectively referred to as signal electrodes 2212) provided on the optical modulator 2202 via the relay substrate 2218 housed in the frame 2204, and are terminated by a terminator 2220 having a specified impedance provided at the other end of the signal electrode 2212.

[0009] The light modulator 2202 outputs two modulated lights from two output optical waveguides 2226a and 2226b, and the two output lights are combined into one beam by a polarization combining unit 2228 including a polarization combining prism, etc. The combined light is output to the outside of the housing 2204 via an output optical fiber 2210 .

[0010] Fig.19 Yes means Fig.18 FIG. 2 is a diagram showing a relay substrate 2218 and its surroundings in the optical modulator 2200. In the optical modulator 2202, ground electrodes 2222a, 2222b, 2222c, 2222d, and 2222e are provided so that the signal electrodes 2212 form coplanar waveguides (CPW).

[0011] Furthermore, signal conductor patterns 2230a, 2230b, 2230c, and 2230d (hereinafter collectively referred to as signal conductor patterns 2230) are formed on the relay substrate 2218 to respectively connect the four signal input terminals 2224 to the four signal electrodes 2212 of the optical modulation element 2202. These signal conductor patterns 2230, together with ground conductor patterns 2240a, 2240b, 2240c, 2240d, and 2240e arranged on the relay substrate 2218 so as to sandwich the signal conductor patterns 2230 in the substrate surface direction, constitute a high-frequency signal line.

[0012] The four signal conductor patterns 2230 of the relay substrate 2218 are respectively provided with component mounting portions 2250a, 2250b, 2250c, and 2250d (hereinafter also collectively referred to as component mounting portions 2250) on which, for example, electrical filters for improving high-frequency characteristics of the optical modulator 2200 are mounted. Fig. 20 yes Fig.19 A partial detailed view of the J portion of the relay substrate 2218 shown in FIG. Fig.21 yes Fig. 20 In these figures, as an example of the component mounting portion 2250, the structure of the component mounting portion 2250b is shown, and the other component mounting portions 2250a, 2250c, and 2250d may also have the same structure.

[0013] The component mounting portion 2250b has, for example, the same structure as the electric filter described in Patent Document 1. That is, the component mounting portion 2250b includes: a thin film resistor 2252b (shaded portion in the figure) formed as an electric circuit element in a part of the signal conductor pattern 2230b; and a capacitor 2254b mounted on the signal conductor pattern 2230b. In addition, the signal conductor pattern 2230b of the component mounting portion 2250b is formed to be wider than other portions, for example.

[0014] The thin film resistor 2252b is formed by forming a portion of the signal conductor pattern 2230b to a desired thickness in such a manner that the portion has a desired resistance value, for example, forming the portion to be thinner than the thickness of other portions. Moreover, for example, the capacitor 2254b is a monolithic capacitor, and its lower surface electrode portion is fixed to the wide portion of the signal conductor pattern 2230b connected to one end of the thin film resistor 2252b, for example, by solder. On the other hand, for example, the upper surface electrode of the capacitor 2254b is connected to the wide portion of the signal conductor pattern 2230b connected to the other end of the thin film resistor 2252b by wire bonding using a wire 2270. Thus, the component mounting portion 2250b constitutes an electric filter formed by connecting the thin film resistor 2252b and the capacitor 2254b in parallel.

[0015] In addition, the DP-QPSK optical modulator described above is currently used at a transmission rate of 100 Gb / s, but development is also being promoted to expand its transmission rate to 400 Gb / s or more. With the high frequency of such modulator operation, as the electrical circuit element (capacitor 2254b, etc.) mounted on such a component mounting portion 2250, it is necessary to select components with excellent high-frequency characteristics, or to match the impedance of the component mounting portion 2250 with the line impedance of the signal conductor pattern 2230, etc.

[0016] However, the component mounting portion 2250 may cause disturbance of the high-frequency (microwave) electrical signal propagating in the signal conductor pattern 2230 due to, for example, a difference in physical shape between the electrical circuit element and the signal conductor pattern 2230, or a deviation in the mounting position of the electrical circuit element. As a result, a part of the microwave electrical signal may leak from the component mounting portion 2250 and become a leakage microwave 2290 ( Fig.14 ) and acts as noise on the adjacent signal conductor pattern 2230 or the signal electrode 2212 on the optical modulation element 2202.

[0017] In particular, when leakage microwaves generated from the component mounting portion 2250 constituting the electric filter in a part of the signal conductor pattern 2230 are recoupled to the signal conductor pattern 2230 itself and the signal electrode 2212 of the optical modulation element 2202 connected to the signal conductor pattern 2230, it will not only act as electrical noise but may also cause new problems such as deterioration or changes in the filtering characteristics of the electric filter.

[0018] Prior art literature

[0019] Patent Literature

[0020] Patent Document 1: Japanese Patent Application Publication No. 2009-244325

[0021] Patent Document 2: Japanese Patent Application Publication No. 2018-54929 Summary of the invention

[0022] Problems to be solved by the invention

[0023] Based on the above background, it is required to suppress the degradation or variation of frequency characteristics (for example, high-frequency characteristics) caused by leakage microwaves that may be generated from part of the electrical circuit elements in an optical modulator having an electrical circuit element such as an electrical filter on a relay substrate that electrically connects the signal electrode of the optical modulator element to the signal input terminal, so as to achieve good modulation characteristics.

[0024] Technical means of solving problems

[0025] One embodiment of the present invention is an optical modulator, comprising: an optical modulator element, comprising a plurality of signal electrodes, and configured to generate two modulated lights, respectively, by two groups of electrical signals each including two electrical signals; a plurality of signal input terminals, inputting electrical signals applied to the signal electrodes respectively; a relay substrate, formed with a plurality of signal conductor patterns electrically connecting the signal input terminals to the signal electrodes and a plurality of ground conductor patterns, and configured to respectively propagate the two groups of electrical signals by two pairs of signal conductor patterns each including two adjacent signal conductor patterns; and a frame, accommodating the optical modulator element and the relay substrate, at least one of the signal conductor patterns having at least one parts mounting portion of a parallel circuit including at least a resistor and a capacitor, the relay substrate having a metal body connected to the ground conductor pattern or a substrate removal portion from which the substrate raw material of the relay substrate is removed, arranged at a portion downstream of the part mounting portion along the propagation direction of the electrical signal sandwiching the at least one signal conductor pattern.

[0026] According to another aspect of the present invention, the metal body or the substrate removal portion is arranged at a distance shorter than the wavelength of a high-frequency signal serving as the electrical signal from an end of an electrical circuit element constituting the component mounting portion along a propagation direction of the electrical signal.

[0027] According to another aspect of the present invention, the metal body is formed to be higher than a height of an electric circuit element constituting the component mounting portion.

[0028] According to another aspect of the present invention, in the at least one signal conductor pattern, a characteristic impedance downstream of the component mounting portion along the propagation direction of the electrical signal is set lower than a characteristic impedance upstream.

[0029] According to another aspect of the present invention, the portion where the characteristic impedance is set to be low is provided by forming the width of the at least one signal conductor pattern to be wider than the width of the upstream signal conductor pattern.

[0030] According to another aspect of the present invention, the at least one signal conductor pattern has a bent portion downstream of the component mounting portion along a propagation direction of the electrical signal.

[0031] According to another aspect of the present invention, the metal body includes a conductive wire, a conductive strip, or a conductive pin at least one end of which is connected to the ground conductor pattern.

[0032] According to another aspect of the present invention, the substrate removal portion is a guide hole or a through hole.

[0033] Another embodiment of the present invention is an optical transmission device, comprising: any one of the optical modulators described above; and an electronic circuit that outputs an electrical signal for causing the optical modulator to perform a modulation operation.

[0034] In addition, this specification includes the entire content of Japanese Patent Application No. 2019-175517 filed on September 26, 2019.

[0035] Effects of the Invention

[0036] According to the present invention, in an optical modulator having electrical circuit elements such as an electrical filter on a relay substrate, electrical noise or degradation or variation of frequency characteristics caused by leakage microwaves that may be generated from these electrical circuit elements can be suppressed to achieve good modulation characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a plan view of the optical modulator according to the first embodiment of the present invention.

[0038] Figure 2 yes Figure 1 Side view of the light modulator shown.

[0039] Figure 3 yes Figure 1 Detailed view of section A of the light modulator shown.

[0040] Figure 4 yes Figure 3 A detailed partial view of section B is shown.

[0041] Figure 5 yes Figure 4 The VV cross-sectional arrow diagram of the local detail is shown.

[0042] Figure 6 It is a diagram showing the structure of a relay substrate of a first modified example of the optical modulator according to the first embodiment.

[0043] Figure 7 It is a diagram showing the structure of a relay substrate according to a second modified example of the optical modulator according to the first embodiment.

[0044] Figure 8 It is a diagram showing the structure of a relay substrate according to a third modified example of the optical modulator according to the first embodiment.

[0045] Fig. 9 It is a diagram showing the structure of a relay substrate according to a fourth modified example of the optical modulator according to the first embodiment.

[0046] Fig.10 It is a diagram showing the structure of a relay substrate according to a fifth modified example of the optical modulator according to the first embodiment.

[0047] Fig.11 It is a plan view showing the structure of the optical modulator according to the second embodiment.

[0048] Fig.12 yes Fig.11 Detailed view of section C of the light modulator shown.

[0049] Fig.13 It is a diagram showing the structure of a relay substrate of a first modified example of the optical modulator according to the second embodiment.

[0050] Fig.14 It is a diagram showing the structure of a relay substrate according to a second modified example of the optical modulator according to the second embodiment.

[0051] Fig.15 It is a plan view showing the structure of the optical modulator according to the third embodiment.

[0052] Fig.16 yes Fig.15 Detailed view of portion D of the light modulator shown.

[0053] Fig.17 It is a diagram showing the structure of an optical transmission device according to a fourth embodiment of the present invention.

[0054] Fig.18 This is an example of the structure of a conventional optical modulator.

[0055] Fig.19 This is a detailed view showing a portion of the periphery of a relay substrate in a conventional optical modulator.

[0056] Fig. 20 Yes means Fig.19 A detailed partial detailed view of section J is shown.

[0057] Fig.21 yes Fig. 20The XXI-XXI cross-sectional arrow diagram of the partial detailed diagram shown.

[0058] [Explanation of Symbols]

[0059] 100, 1100, 1500, 2200: Optical modulator

[0060] 102, 1102, 1502, 2202: Light modulation element

[0061] 104, 2204: Frame

[0062] 106a, 106b: Modulated light

[0063] 108, 2208: Input fiber

[0064] 110, 2210: Output fiber

[0065] 112, 112a, 112b, 112c, 112d, 1112, 1112a, 1112b, 1112c, 1112d, 1512, 1512a, 1512b, 1512c, 1512d, 2212, 2212a, 2212b, 2212c, 2212d: signal electrodes

[0066] 114a, 2214a: Shell

[0067] 114b, 2214b: hood

[0068] 116, 116a, 116b, 116c, 116d, 2216, 2216a, 2216b, 2216c, 2216d: electrical connector

[0069] 118, 618, 718, 818, 918, 1018, 1118, 1318, 1418, 1518, 2218: Relay substrate

[0070] 120, 2220: Terminal

[0071] 122, 122a, 122b, 122c, 122d, 122e, 1122, 1122a, 1122b, 1122c, 1122d, 1122e, 1522, 1522a, 1522b, 1522c, 1522d, 1522e, 2222a, 2222b, 2222c, 2222d, 2222e: ground electrode

[0072] 124, 124a, 124b, 124c, 124d, 2224, 2224a, 2224b, 2224c, 2224d: Signal input terminals

[0073] 126a, 126b, 2226a, 2226b: Output optical waveguide

[0074] 128, 2228: Polarization synthesis department

[0075] 318a: Signal input edge

[0076] 318b: Signal output edge

[0077] 318c, 318d: side edge

[0078] 326, 328, 360, 1660, 2270: Wire

[0079] 330, 330a, 330b, 330c, 330d, 730, 730a, 730b, 730c, 730d, 1230, 1230a, 1230b, 1230c, 1230d, 1330, 1330a, 1330b, 1330c, 1330d, 1630, 1630a, 1630b, 1630c, 1630d, 2230, 2230a, 2230b, 2230c, 2230d: signal conductor pattern

[0080] 340, 340a, 340b, 340c, 340d, 340e, 1240, 1240a, 1240b, 1240c, 1240d, 1240e, 1640, 1640a, 1640b, 1640c, 1640d, 2240, 2240a, 2240b, 2240c, 2240d, 2240e: Ground conductor pattern

[0081] 350, 350a, 350b, 350c, 350d, 2250a, 2250b, 2250c, 2250d: Parts mounting section

[0082] 352c, 2252b: Thin film resistors

[0083] 354c, 2254b: Capacitors

[0084] 660: Conductor pin

[0085] 860: Guide hole

[0086] 862, 962, 1062, 1462, 1464, 1466, 1662, 1664: Substrate removal unit

[0087] 2100: Optical transmitter

[0088] 2104: Light Source

[0089] 2106: Modulation signal generation unit

[0090] 2108: Modulation data generation unit

[0091] 2290: Leaking Microwaves

[0092] d, h: height

[0093] Dw1, Dw2: Width

[0094] L: distance DETAILED DESCRIPTION

[0095] Generally speaking, the leakage microwave generated in the component mounting portion of the relay substrate will spread the component mounting portion as a point wave source to the entire part, but has a directivity whose intensity is concentrated in the direction of propagation of the high-frequency signal of the signal conductor pattern in the component mounting portion. In the embodiment of the present invention shown below, a recoupling suppression structure is provided in the relay substrate, and the recoupling suppression structure is used to prevent the propagation of the leakage microwave generated from the component mounting portion, thereby preventing the leakage microwave from recoupling to its own generation source, that is, the signal conductor pattern (or the high-frequency propagation mode propagating inside it).

[0096] These recoupling suppression structures are, as a means to prevent the spatial propagation of leakage microwaves, for example, metal wires (e.g., bonding wires) and / or metal pins erected in a bridge shape on the substrate, and / or, as a means to prevent the propagation of leakage microwaves in the raw material of the relay substrate, a substrate removal portion (e.g., a guide hole or a through hole) from which the raw material of the relay substrate is removed. In addition, hereinafter, the so-called "(propagation) direction of leakage microwaves" refers to the direction of the directivity of the leakage microwaves (i.e., the direction in which the intensity of the leakage microwaves is concentrated and propagated).

[0097] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0098] [First embodiment]

[0099] First, a first embodiment of the present invention will be described. Figure 1 is a plan view showing the structure of an optical modulator 100 according to the first embodiment of the present invention. Figure 2 is a side view of the optical modulator 100, Figure 3 yes Figure 1 A detailed partial view of section A in FIG.

[0100] The optical modulator 100 includes an optical modulator 102 , a housing 104 accommodating the optical modulator 102 , an input optical fiber 108 for allowing light to enter the optical modulator 102 , and an output optical fiber 110 for guiding the light output from the optical modulator 102 to the outside of the housing 104 .

[0101] The optical modulation element 102 is, for example, a DP-QPSK modulator that performs optical modulation at 400 Gb / s, and includes, for example, two nested Mach-Zehnder optical waveguides provided on an LN substrate and each including two Mach-Zehnder optical waveguides. In the four Mach-Zehnder optical waveguides constituting the two nested Mach-Zehnder optical waveguides, there are provided four signal electrodes 112a, 112b, 112c, and 112d (hereinafter, also collectively referred to as signal electrodes 112) that modulate light waves propagating in the Mach-Zehnder optical waveguides, respectively. Furthermore, as is known in the prior art, on the surface of the LN substrate of the optical modulation element 102, for example, ground electrodes 122a, 122b, 122c, 122d, and 122e are provided (see Figure 3 , Figure 1 (not shown in the figure) so that the four signal electrodes 112a, 112b, 112c, and 112d respectively form a coplanar waveguide (CPW).

[0102] Specifically, the ground electrodes 122a, 122b, 122c, 122d, and 122e (hereinafter, also collectively referred to as the ground electrodes 122) are arranged in a plane on the surface of the LN substrate so as to sandwich the signal electrodes 112a, 112b, 112c, and 112d, respectively, and together with the four signal electrodes 112a, 112b, 112c, and 112d, form a coplanar line having a specified characteristic impedance at a specified operating frequency.

[0103] Four high-frequency electrical signals (modulation signals) are input to the four signal electrodes 112. These high-frequency electrical signals cooperatively control the propagation of light waves in the four Mach-Zehnder optical waveguides, thereby performing 400 Gb / s DP-QPSK modulation as a whole.

[0104] Specifically, two pairs of high-frequency electrical signals including two high-frequency electrical signals are applied to the four signal electrodes 112. The optical modulation element 102 is configured to generate two modulated lights 106a and 106b (arrows in the figure) modulated according to the respective pairs of electrical signals. The two modulated lights 106a and 106b generated are outputted from the two output optical waveguides 126a and 126b of the two nested Mach-Zehnder optical waveguides constituting the optical modulation element 102, respectively. In the present embodiment, the two high-frequency electrical signals constituting one pair are applied to the signal electrodes 112a and 112b to generate the modulated light 106a outputted from the output optical waveguide 126a, and the other two high-frequency electrical signals constituting the other pair are applied to the signal electrodes 112c and 112d to generate the modulated light 106b outputted from the output optical waveguide 126b. The two modulated lights 106 a and 106 b are combined into one beam by a polarization combining unit 128 including a polarization combining prism and the like, and then output to the outside of the housing 104 via an output optical fiber 110 .

[0105] The frame 104 includes a housing 114a and a cover 114b for fixing the light modulator 102. Figure 1 In the figure, only a part of the cover 114b is shown on the right side of the figure, but in fact, the cover 114b is arranged to cover the entire box-shaped housing 114a, and the inside of the frame 104 is hermetically sealed. The housing 114a includes metal or, for example, gold-plated ceramics, and functions as an electrical conductor. In addition, the frame 104 may generally be provided with a plurality of pins for DC bias control, etc., but these are omitted in this figure.

[0106] The housing 114a is provided with electrical connectors 116a, 116b, 116c, 116d (hereinafter also collectively referred to as electrical connector 116) as coaxial connectors, and the electrical connectors 116a, 116b, 116c, 116d include signal input terminals 124a, 124b, 124c, 124d (hereinafter also collectively referred to as signal input terminals 124) for inputting high-frequency electrical signals applied to the signal electrodes 112a, 112b, 112c, 112d of the optical modulator element 102, respectively.

[0107] Each of the electrical connectors 116 is, for example, a push-on type coaxial connector receptacle, and includes a cylindrical ground conductor, and the signal input terminal 124 includes a center conductor (core wire) extending along the center line of the cylindrical ground conductor. Each of the cylindrical ground conductors is electrically connected to the housing 114a and fixed. Therefore, the housing 114a constitutes a part of the ground line for supplying the ground potential. Furthermore, each of the signal input terminals 124 is electrically connected to one end of each of the signal electrodes 112 of the optical modulation element 102 via the relay substrate 118.

[0108] The other end of the signal electrode 112 of the optical modulation element 102 is terminated by a terminator 120 having a predetermined impedance. Thus, the electrical signal input to each end of the signal electrode 112 propagates in the signal electrode 112 as a traveling wave.

[0109] Figure 3 yes Figure 1 The detailed view of the A portion shown shows the structure of the relay substrate 118 and its surroundings. The relay substrate 118 is formed with signal conductor patterns 330a, 330b, 330c, 330d (hereinafter, also collectively referred to as signal conductor patterns 330) and ground conductor patterns 340a, 340b, 340c, 340d, 340e (hereinafter, also collectively referred to as ground conductor patterns 340).

[0110] The signal conductor patterns 330a, 330b, 330c, and 330d respectively connect the signal electrodes 112a, 112b, 112c, and 112d to the corresponding signal input terminals 124. In particular, one pair of high-frequency electrical signals generating the modulated light 106a is given to the signal electrodes 112a and 112b via the signal conductor patterns 330a and 330b adjacent to each other. Moreover, the other pair of high-frequency electrical signals generating the modulated light 106b is given to the signal electrodes 112d and 112d via the signal conductor patterns 330c and 330d adjacent to each other. That is, the signal conductor patterns 330a and 330b constitute one pair of signal conductor patterns and propagate one pair (group) of high-frequency electrical signals, and the signal conductor patterns 330c and 330d constitute another pair of signal conductor patterns and propagate another pair (group) of high-frequency electrical signals.

[0111] The relay substrate 118 is provided with a surface (where the signal conductor pattern 330 and the ground conductor pattern 340 are formed) Figure 3 A back ground conductor (not shown) is formed on the entire back surface (for example, the entire surface) facing the back surface (shown in the figure). The back ground conductor is fixed to the housing 114a of the frame 104 by, for example, solder, welding material, or a conductive adhesive. Thus, the back ground conductor becomes a ground line component. Each of the ground conductor patterns 340 is connected to the back ground conductor via an appropriate through hole (not shown) and is connected to the ground line.

[0112] The ground conductor patterns 340a, 340b, 340c, 340d, and 340e are provided so as to sandwich the signal conductor patterns 330a, 330b, 330c, and 330d within the surface of the relay substrate 118. Thus, the signal conductor patterns 330 and the ground conductor patterns 340 form coplanar lines.

[0113] In the present embodiment, the signal conductor pattern 330 extends in the vertical direction as shown in the figure, and one end of the signal conductor pattern 330 is connected to the signal input terminal 124 on the lower side of the side of the relay substrate 118. Here, the side of the side of the relay substrate 118 that connects the signal conductor pattern 330 and the signal input terminal 124 is referred to as the signal input side 318a.

[0114] The signal electrode 112 of the optical modulator 102 is electrically connected to the other end of the signal conductor pattern 330 of the relay substrate 118 at the upper side of the side of the relay substrate 118, for example, by wire bonding using a wire 326. The wire 326 can be, for example, a metal wire (such as a gold (Au) wire). Here, the side of the side of the relay substrate 118 that connects the signal conductor pattern 330 and the signal electrode 112 of the optical modulator 102 is called a signal output side 318b. In the present embodiment, the signal input side 318a and the signal output side 318b constitute two opposite sides of the relay substrate 118 when viewed from above. Figure 3 The two opposing sides of the relay substrate 118 other than the signal input side 318a and the signal output side 318b are referred to as side edges (side edges) 318c and 318d.

[0115] The ground electrode 122 constituting the coplanar line with the signal electrode 112 in the optical modulation element 102 is electrically connected to one end of each of the ground conductor pattern 340 at the signal output side 318b of the relay substrate 118 by wire bonding using, for example, a wire 326, as described above. The wire bonding using the wire 326 is an example and is not limited thereto. Instead of the wire bonding using the wire 326, strip bonding using, for example, a conductor strip such as a metal strip (for example, a gold (Au) strip) may be used.

[0116] The signal conductor patterns 330a, 330b, 330c, and 330d each have a portion (the portion marked with a black shadow in the figure) where, for example, electrical circuit elements constituting an electrical filter (bandpass filter, high-pass filter, etc.) are provided, namely, component mounting portions 350a, 350b, 350c, and 350d (hereinafter, collectively referred to as component mounting portions 350). Here, the so-called electrical circuit elements refer to active components and / or passive components that are functional components constituting a circuit, and do not include wiring patterns or pads (solder pads) specifically provided for electrical connection. The component mounting portion 350 can be, for example, a parallel circuit that includes at least a resistor and a capacitor.

[0117] Figure 4 yes Figure 3 The partial detailed view of the B portion shown is a view showing the structure of the component mounting portion 350c and its surroundings. Figure 4The component mounting portion 350c shown is an example, and the other component mounting portions 350a, 350b, 350d and their surrounding structures should also be understood as similar. Figure 4 same.

[0118] The component mounting portion 350c is, for example, Figures 18 to 21 Similarly, the component mounting portion 2250, which shows an example, is an electric filter formed by mounting an electric circuit element such as a capacitor on a portion of the signal conductor pattern 330c which is provided wider than other portions, and / or forming an electric circuit element such as a thin film resistor. The electric filter can be provided as a bandpass filter, a high-pass filter, or a low-pass filter, for example. However, forming the signal conductor pattern 330 in the component mounting portion 350 in a wide width is an example, and the signal conductor pattern 330 in the component mounting portion 350 can also be formed in the same width as other portions.

[0119] Specifically, the component mounting portion 350c includes: a thin film resistor 352c formed on the wide portion of the signal conductor pattern 330c; and a capacitor 354c mounted on the wide portion. The capacitor 354c is, for example, a monolithic capacitor, and its lower surface electrode portion is fixed to the wide portion of the signal conductor pattern 330c connected to one end of the thin film resistor 352c, for example, by solder. On the other hand, the upper surface electrode of the capacitor 354c is connected to the wide portion of the signal conductor pattern 330c connected to the other end of the thin film resistor 352c, for example, by wire bonding using a wire 328. Thus, the component mounting portion 350c constitutes an electric filter (RC filter) formed by connecting the thin film resistor 352c and the capacitor 354c in parallel. Here, the range of the component mounting portion 350c can be set to, for example, Figure 5 The range is from the position of the left end surface of the capacitor 354c in the figure to the position on the signal conductor pattern 330c to which the wire 328 is connected.

[0120] Furthermore, in the present embodiment, in particular, in the relay substrate 118, four wires 360 are provided in a bridge-like manner that connects two adjacent ground conductor patterns 340 and spans the signal conductor pattern 330, at a portion of the signal conductor pattern 330 that is downstream of the component mounting portion 350 in the propagation direction of the electric signal. Here, the wires 360 correspond to, for example, metal bodies that do not constitute an electric circuit and are provided at positions sandwiching a portion of the signal conductor pattern 330 that is downstream of the component mounting portion 350 in the propagation direction of the electric signal. Such metal wires 360 absorb leakage microwaves generated from the component mounting portion 350 and propagating in space, and function as a shield against the leakage microwaves.

[0121] Thus, in this embodiment, leakage microwaves (for example, in the case of a component mounting portion 350c provided in the signal conductor pattern 330c) generated from the component mounting portion 350c and propagating in the air in the downstream direction thereof can be suppressed. Figure 3 The leakage microwaves propagating in the range sandwiched by the two dot-chain arrows extending from the component mounting portion 350c) are recoupled to the signal conductor pattern 330c (or the propagation mode of the electrical signal propagating inside it). That is, the wire 360 ​​as the metal body corresponds to the recoupling suppression structure. In addition, the metal body functions as a recoupling suppression structure that suppresses recoupling by preventing the propagation of the leakage microwaves generated from the component mounting portion 350, and does not include, for example, the wire 326 or the conductor strip that connects the ground electrode 122 of the optical modulator 102 to the ground conductor pattern 340 of the relay substrate 118.

[0122] Therefore, in the optical modulator 100, for example, it is possible to avoid the frequency characteristics of the signal conductor pattern 330 including the component mounting portion 350 when viewed as a whole from changing (degrading) or changing to something different from the frequency characteristics of the component mounting portion 350 designed to constitute the electrical filter. As a result, in the optical modulator 100, the frequency characteristics of each of the signal conductor patterns 330 including the component mounting portion 350 as a whole can be set to a desired characteristic, thereby achieving good optical modulation characteristics. The effect of improving the optical modulation characteristics brought about by the stabilization of the frequency characteristics of the signal conductor pattern is particularly significant in an optical modulator that is configured to generate two modulated lights that are modulated separately based on two groups of electrical signals each including two electrical signals, such as the optical modulator 100 that performs DP-QPSK modulation in the present embodiment. This is because, in this type of modulator, the frequency variation in one signal conductor pattern has a greater influence on the optical modulation characteristics of the optical modulator as a whole than in other types of optical modulators.

[0123] Here, from the viewpoint of effectively preventing the leakage microwave generated from the component mounting portion 350 from being recoupled to the signal conductor pattern 330 itself, it is ideal that Figure 5 As shown, at least one conductor 360 is provided within a range of a predetermined distance L from a generation point of leakage microwaves in the component mounting portion 350. From the viewpoint of avoiding the re-coupling, the distance L is preferably less than a few wavelengths (e.g., 5 times the wavelength) of the center wavelength of the high-frequency electrical signal propagating in the signal conductor pattern 330, and more preferably within 1 wavelength. When the center frequency of the high-frequency electrical signal is 100 GHz, the center wavelength is, for example, a value of about 3 mm. In addition, the generation point of the leakage microwaves can be set to any end of an electrical circuit element constituting the component mounting portion 350 (e.g., Figure 5) In the figure, the right end of the capacitor 354c, which is a monolithic capacitor of the component mounting portion, is shown. In addition, in a modulator that performs a modulation operation of 400 Gb / s or more, the distance L is preferably 6 mm or less, and more preferably 3 mm or less.

[0124] Furthermore, from the viewpoint of re-coupling suppression, it is desirable that the height h of the wire 360 ​​erected from the ground conductor pattern 340 is as follows: Figure 5 As shown, it is greater than the height of the electrical circuit element constituting the component mounting portion 350 (for example, the height d of the capacitor 354c in this embodiment). For example, the general thickness of the monolithic capacitor used in this application is 100 μm, whereas the lead 360 can be erected at a height of about 100 μm to several hundred μm.

[0125] In addition, in the present embodiment, the wire 360 ​​as a metal body is provided to electrically connect two adjacent ground conductor patterns 340 of the signal conductor pattern 330 sandwiching the downstream portion of the component mounting portion 350, and is provided upright in a bridge shape, but the present invention is not limited thereto. The wire 360 ​​does not necessarily need to be provided upright in a bridge shape, and as long as it is provided at a position sandwiching the downstream portion of the component mounting portion 350, it may be provided to be provided upright in a columnar shape from the surface of the relay substrate 118 with only one end connected and fixed to the ground conductor pattern 340. Even with such a configuration, by providing a plurality of wires 360 upright in a manner sandwiching the downstream portion, for example, at a frequency determined by the intervals between the wires 360, it is possible to shield the propagation of the leakage microwave and suppress the change or fluctuation of the frequency characteristics.

[0126] In addition, in this embodiment, the wire 360 ​​as a metal body is connected to each signal conductor pattern 330 as shown in FIG. Figure 3 , Figure 4 As shown in the figure, four wires 360 are provided at substantially equal intervals, but the present invention is not limited thereto. The number of wires 360 can be set to be less than or more than four according to the degree of change in the frequency characteristics associated with the re-coupling of the leakage microwave, and the plurality of wires 360 can also be provided at unequal intervals. Of course, in this case, the greater the number of wires 360, the more the change in the frequency characteristics caused by the leakage microwave can be suppressed.

[0127] In addition, the wire 360 ​​may be a metal wire (for example, a gold (Au) wire) or the like. Furthermore, instead of the wire 360, a conductor strip such as a metal strip (gold (Au) strip) may be used.

[0128] Next, a modification of the relay substrate used for the optical modulator 100 according to the present embodiment will be described.

[0129] <First Modification of First Embodiment>

[0130] Figure 6 is a diagram showing the structure of a relay substrate 618 according to a first modification of the first embodiment, and is equivalent to Figure 3 The relay substrate 618 can be Figure 1 In the optical modulator 100 shown in the figure, it is used instead of the relay substrate 118. Figure 6 In Figure 3 The same components as those of the relay substrate 118 shown in FIG. Figure 3 The same symbols are used to represent and refer to the Figure 3 Description.

[0131] The relay substrate 618 has Figure 3 The structure of the relay substrate 118 shown in FIG. 1 is the same as that of the relay substrate 118 shown in FIG. 1 , but the difference is that a conductor pin 660 is provided instead of the wire 360. That is, in a portion of the signal conductor pattern 330 that is downstream of the component mounting portion 350 along the propagation direction of the electric signal propagating in the signal conductor pattern 330, four conductor pins 660 are provided at the positions of two adjacent ground conductor patterns 340 sandwiching the portion. The conductor pins 660 can be set as metal pins (for example, stainless steel pins). Here, the conductor pins 660 correspond to metal bodies that do not constitute an electric circuit and are provided in the ground conductor patterns 340a and 340b that sandwich the portion of the signal conductor pattern 330 that is downstream of the component mounting portion 350 along the propagation direction of the electric signal.

[0132] Conductor pin 660 with Figure 3 The conductor 360 in the relay substrate 118 shown in the figure also functions as a shield for the leakage microwave generated from the component mounting portion 350 and propagating in space, and can suppress the leakage microwave from propagating and re-coupling to its own signal conductor pattern 330. Therefore, in the relay substrate 618, it is also possible to suppress the frequency characteristics of the signal conductor pattern 330 as a whole including the component mounting portion 350 from changing due to the re-coupling of the leakage microwave, thereby realizing good light modulation characteristics. In addition, the shape of the conductor pin 660 may be a straight line, a curve, or a bent shape as long as it has a shielding function.

[0133] <Second Modification of First Embodiment>

[0134] Next, a second modification example of the relay substrate used for the optical modulator 100 will be described.

[0135] Figure 7 is a diagram showing the structure of a relay substrate 718 according to a second modification of the first embodiment, which is equivalent to Figure 3The relay substrate 718 may be Figure 1 In the optical modulator 100 shown in the figure, it is used instead of the relay substrate 118. Figure 7 In Figure 3 The same components as those of the relay substrate 118 shown in FIG. Figure 3 The same symbols are used to represent and refer to the Figure 3 Description.

[0136] The relay substrate 718 has Figure 3 The structure of the relay substrate 118 shown in FIG. 1 is the same as that of the relay substrate 118, but the difference from the relay substrate 118 is that the signal conductor patterns 330a, 330b, 330c, 330d are replaced with signal conductor patterns 730a, 730b, 730c, 730d (hereinafter, also collectively referred to as signal conductor pattern 730). The signal conductor pattern 730 has the same structure as the signal conductor pattern 330, but the difference from the signal conductor pattern 330 is that the width Dw2 of the downstream portion of the component mounting portion 350 along the propagation direction of the electrical signal from the signal input terminal 124 to the signal electrode 112 is formed to be wider than the width Dw1 of the upstream portion.

[0137] As a result, in the signal conductor pattern 770, the characteristic impedance of the downstream becomes lower than the characteristic impedance of the upstream, and the sealing strength of the high-frequency electric signal in the signal conductor pattern 770 becomes stronger in the downstream relative to the upstream. Therefore, in the portion of the signal conductor pattern 730 downstream of the component mounting portion 350, the separation of the high-frequency electric signal (hereinafter also referred to as the propagation microwave) propagating in the signal conductor pattern 730 and the leakage microwave (the difficulty of coupling the leakage microwave with the propagation microwave) is improved. Therefore, in the relay substrate 718, Figure 3 Compared with the relay substrate 118 shown in the figure, the leakage microwave generated from the component mounting portion 350 can be further suppressed from being re-coupled to the signal conductor pattern 730 at the downstream portion, thereby further suppressing the change in the overall frequency characteristics of the signal conductor pattern 730. As a result, in the relay substrate 718, better optical modulation characteristics can be achieved compared with the relay substrate 118.

[0138] <Third Modification of First Embodiment>

[0139] Next, a third modified example of the relay substrate used for the optical modulator 100 will be described.

[0140] Figure 8 is a diagram showing the structure of a relay substrate 818 according to a third modified example of the first embodiment, which is equivalent to Figure 3 The relay substrate 818 may be in the Figure 1 In the optical modulator 100 shown in the figure, it is used instead of the relay substrate 118. Figure 8 In Figure 3 The same components as those of the relay substrate 118 shown in FIG. Figure 3 The same symbols are used to represent and refer to the Figure 3 Description.

[0141] The relay substrate 818 has Figure 3 The relay substrate 118 shown in FIG. 1 has the same structure, but in the ground conductor pattern 340, a guide hole 860 is provided, and the guide hole 860 is used to connect to the back side (connecting to the ground conductor pattern 340) of the relay substrate 818. Figure 8 The ground conductor (not shown) is electrically connected to the surface facing the surface shown. Figure 8 In order to avoid redundant description, only the guide hole arranged at the bottom of the figure is marked with the symbol 860, but it should be understood that the circles drawn along the signal conductor pattern 330 and with the same size as them are the same guide holes 860.

[0142] Furthermore, unlike the relay substrate 118, the relay substrate 818 does not have the conductive wire 360 ​​as a metal body, but has a substrate removal portion 862 obtained by removing the substrate material of the relay substrate 818. The substrate removal portion 862 is provided between two adjacent ground conductor patterns 340 sandwiching a portion downstream of the component mounting portion 350 along the propagation direction of each electrical signal, with respect to each signal conductor pattern 330. Here, the substrate removal portion 862 is provided in the present modification as a through hole that penetrates the relay substrate 818 in the thickness direction and is elliptical in plan view.

[0143] By means of the substrate removal portion 862, in the relay substrate 818, for example, it is possible to suppress the leakage microwave generated from the component mounting portion 350c provided in the signal conductor pattern 330c from propagating in the substrate material of the relay substrate 818 in the downstream direction (for example, in Figure 8 In other words, the substrate removal portion 862 functions as a re-coupling suppression structure to suppress the re-coupling of the leakage microwave propagating in the relay substrate 818 to its own signal conductor pattern 330 (or the propagation mode of the electrical signal propagating therein). As a result, in the relay substrate 818, the frequency characteristics of the signal conductor pattern 330 as a whole including the component mounting portion 350 can be prevented from being changed or degraded due to the re-coupling of the leakage microwave, thereby achieving good optical modulation characteristics.

[0144] In addition, from the viewpoint of effectively suppressing the propagation of the leakage microwave, similarly to the wire 360 ​​in the relay substrate 118, it is desirable that at least a part of the substrate cutout portion 862 is provided within a range of a predetermined distance L from the point of generation of the leakage microwave in the component mounting portion 350 (for example, the end of the capacitor 354c which is a monolithic capacitor). From the viewpoint of avoiding the recoupling, the distance L is preferably a length of several wavelengths (for example, five wavelengths) or less of the central wavelength of the high-frequency electric signal propagating in the signal conductor pattern 330 in the substrate material of the relay substrate 818, and more preferably a length within one wavelength.

[0145] Moreover, in this modification, the substrate removal portion 862 is set to be an ellipse in a plan view, but it is not limited to this. The plan view shape of the substrate removal portion 862 can be set to a circle or any shape. Moreover, from the viewpoint of effectively suppressing the propagation of the leakage microwave, it is preferred that the substrate removal portion 862 is filled with metal inside, or a metal film is formed on its inner surface. For example, the substrate removal portion 862 can be set as a guide hole or a through hole.

[0146] Furthermore, in this modification, the substrate removal portion 862 is provided as a through hole, but the present invention is not limited thereto. The substrate removal portion 862 may not be a through hole, but may be provided as a concave portion where the substrate material is removed to the middle of the thickness direction of the relay substrate 818. In this case, the propagation of the leakage microwave can also be prevented to a certain extent in the portion where the substrate is removed.

[0147] From the viewpoint of effectively suppressing the propagation of the leakage microwave, the size of the substrate cutout portion 862 is preferably longer as measured in a direction orthogonal to the propagation direction of the leakage microwave. For example, the size of the substrate cutout portion 862 is preferably such that the length (for example, the length of the major diameter in the ellipse) measured in the direction of longest length when viewed from above (hereinafter referred to as the maximum length) is larger than the diameter of the guide hole or through hole provided in the portion of the ground conductor pattern 340 on the upstream side of the component mounting portion 350 in the propagation direction of the electrical signal.

[0148] In the relay substrate, the guide hole or through hole used to electrically connect the conductor patterns on the front and back surfaces is generally formed in a circular shape from the viewpoint of the ease of substrate manufacturing. In contrast, regarding the substrate removal portion 862, in order to block the leakage microwaves diffusing in the substrate interior of the relay substrate as widely as possible, it is ideal that the aspect ratio (the ratio of the short diameter to the maximum length) with respect to the maximum length is large, but it can be greater than 1 and less than about 10 based on the relationship between the substrate strength and the adjacent conductor patterns.

[0149] Moreover, in this modification, each of the substrate removal portions 862 is provided as a hole that is elliptical when viewed from above, but the present invention is not limited thereto. The substrate removal portion 862 may be configured as an arrangement of a plurality of holes that are circular when viewed from above, for example. In this case, the interval between adjacent holes constituting the arrangement is preferably less than 5 times the diameter of the hole, and more preferably less than 2 times. Furthermore, when the substrate removal portion 862 is configured as a two-dimensional arrangement of the holes, it is ideally configured so that the holes overlap with each other when viewed from the component mounting portion 350 closest to the two-dimensional arrangement of the holes.

[0150] Furthermore, in this modification, two substrate removal portions 862 are provided for each signal conductor pattern 330, but the present invention is not limited thereto. Adjacent substrate removal portions 862 may be connected to form one substrate removal portion. Figure 8 In the embodiment, the substrate material between the two substrate removal portions 862 provided in the ground conductor pattern 340 b may be further removed, and the two substrate removal portions 862 may be connected to form an elliptical through hole.

[0151] In addition, the direction of the maximum length of the elliptical substrate removal portion 862 may be along a direction orthogonal to the propagation direction of the leakage microwave, or may not be along the orthogonal direction. Figure 8 In the figure, the substrate removal portion 862 may be inclined in a manner such that the direction of its maximum length is at a right angle to the leakage microwave propagating in the direction of the arrow indicated by the dotted chain line.

[0152] <Fourth Modification of First Embodiment>

[0153] Next, a fourth modification example of the relay substrate used for the optical modulator 100 will be described.

[0154] Fig. 9 is a diagram showing the structure of a relay substrate 918 according to a fourth modified example of the first embodiment, which is equivalent to Figure 3 The relay substrate 918 may be Figure 1 In the optical modulator 100 shown in the figure, it is used instead of the relay substrate 118. Fig. 9 In Figure 3 as well as Figure 8 The same components as those of the relay substrates 118 and 818 are used. Figure 3 as well as Figure 8 The same symbols are used to represent and refer to the Figure 3 as well as Figure 8 Description.

[0155] The relay substrate 918 has Figure 8The structure of the relay substrate 818 shown in FIG. 1 is the same as that of the relay substrate 818 shown in FIG. 1 , but the difference from the relay substrate 818 is that it further has a substrate removal portion 962. The substrate removal portion 962 has the same structure as the substrate removal portion 862, and is arranged at a position to fill the gap between two adjacent substrate removal portions 862 (more specifically, the gap viewed from the component mounting portion 350).

[0156] Thus, in the relay substrate 918, the leakage microwaves that pass through the gaps between the substrate removal portions 862 and propagate within the substrate raw material of the relay substrate 818 can be prevented by the substrate removal portion 962. Therefore, compared with the relay substrate 818, the re-coupling of the leakage microwaves can be further suppressed to achieve good optical modulation characteristics.

[0157] <Fifth Modification of First Embodiment>

[0158] Next, a fifth modification example of the relay substrate used for the optical modulator 100 will be described.

[0159] Fig.10 is a diagram showing the structure of a relay substrate 1018 according to a fifth modification of the first embodiment, which is equivalent to Figure 3 The relay substrate 1018 may be Figure 1 In the optical modulator 100 shown in the figure, it is used instead of the relay substrate 118. Fig.10 In Figure 3 , Figure 6 , Figure 8 The same components as those of the relay substrates 118, 618, and 818 are used. Figure 3 , Figure 6 , Figure 8 The same symbols are used to represent and refer to the Figure 3 , Figure 6 , Figure 8 Description.

[0160] The relay substrate 1018 has Figure 8 The relay substrate 818 shown in FIG. 1 has the same structure as the relay substrate 818 shown in FIG. 1 , but differs from the relay substrate 818 in that a substrate removal portion 1062 is provided in place of the substrate removal portion 862 in the ground conductor patterns 340b, 340c, and 340d. Figure 6 Similarly, in the illustrated relay substrate 618 , conductor pins 660 are provided at portions sandwiching two ground conductor patterns 340 at portions of the signal conductor pattern 330 that are downstream of the component mounting portion 350 in the propagation direction of the electrical signal.

[0161] Thus, in the relay substrate 1018, the leakage microwaves generated from the component mounting portion 350 and propagating in the air and the leakage microwaves propagating in the substrate material of the relay substrate 1018 can be suppressed by the conductor pins 660 and the substrate cutout portion 1062. Therefore, in the relay substrate 1018, the re-coupling of the leakage microwaves can be further suppressed than in the relay substrates 618 and 818, thereby realizing good optical modulation characteristics.

[0162] In addition, from the perspective of effectively suppressing leakage microwaves, it is ideal that at least one conductor pin and / or at least a portion of the substrate removal portion 862, 1062 is provided within a range of a predetermined distance L from a point of generation of leakage microwaves within the part mounting portion 350 (for example, an end portion of the capacitor 354c which is a single-chip capacitor).

[0163] In addition, in this modification, the conductor pin 660 is used, but the present invention is not limited to this. Instead of the conductor pin 660, a substrate removal portion 1062 may be used together with the substrate removal portion 1062. Figure 3 The conductors 360 (or conductor strips) of the relay substrate 118 are shown.

[0164] and, Fig.10 The order of arrangement of the conductor pin 660 and the substrate cutout portion 1062 on the downstream side of the component mounting portion 350 is an example and is not limited thereto. For example, instead of arranging the conductor pin 660 closest to the component mounting portion 350, the substrate cutout portion 862 or 1062 may be arranged closest to the component mounting portion 350.

[0165] [Second embodiment]

[0166] Next, the optical modulator of the second embodiment of the present invention is described. In the optical modulator 100 of the first embodiment, the arrangement pitch of the signal electrodes 112 of the optical modulator 102 is equal to the arrangement pitch of the signal input terminals 124, but the present invention is not limited to this. The arrangement pitch of the signal electrodes of the optical modulator may be larger than the arrangement pitch of the signal input terminals 124, or may be smaller than the arrangement pitch of the signal input terminals 124. This embodiment is the first example of a case where the arrangement pitch of the signal electrodes of the optical modulator is smaller than the arrangement pitch of the signal input terminals 124.

[0167] Fig.11 is a plan view showing the structure of an optical modulator 1100 according to a second embodiment of the present invention. Fig.12 yes Fig.11 A detailed partial view of section C in FIG.

[0168] As described below, the relay substrate 1118 used in the optical modulator 1100 of this embodiment has Figure 3The optical modulator 1100 has the same features as the relay substrate 118 shown in the figure, but the signal conductor pattern 1230a and the like are formed in a shape different from the signal conductor pattern 330a and the like of the relay substrate 118. In particular, in the optical modulator 1100, the arrangement pitch of the signal electrodes 1112 of the optical modulation element 1102 is narrowed relative to the arrangement pitch of the signal input terminals 124 included in the frame 104.

[0169] Fig.11 In Figure 1 The same components as those of the optical modulator 100 of the first embodiment shown in FIG. Figure 1 The same symbols as in the symbols, and references to the Figure 1 Description. Fig.11 The optical modulator 1100 shown has Figure 1 The light modulator 100 shown has the same structure as that shown in the figure, but differs in that it includes a light modulator 1102 and a relay substrate 1118 instead of the light modulator 102 and the relay substrate 118 .

[0170] The optical modulator 1102 has the same structure as the optical modulator 102, but differs in that it includes signal electrodes 1112a, 1112b, 1112c, and 1112d (also collectively referred to as signal electrodes 1112) instead of the signal electrode 112, and includes ground electrodes 1122a, 1122b, 1122c, 1122d, and 1122e (also collectively referred to as ground electrodes 1122) instead of the ground electrode 122 (see Fig.12 ).

[0171] The signal electrodes 1112 have the same structure as the signal electrodes 112, but the spacing between the signal electrodes 1112 is different from the spacing between the signal electrodes 112. Furthermore, the ground electrodes 1122 have the same structure as the ground electrodes 122, but their shapes are different from those of the ground electrodes 122 in order to form a coplanar line together with the signal electrodes 1112.

[0172] Fig.12 yes Fig.11 The partial detailed view of the C portion shown in FIG. 1 shows the structure of the relay substrate 1118 and its surroundings in the optical modulator 1100. Fig.12 In Figure 3 The same components as the relay substrate 118 shown in FIG. Figure 3 The same symbols as in the symbols, and references to the Figure 3 Description.

[0173] The relay substrate 1118 has Figure 3The relay substrate 118 shown in FIG. 1 has the same structure as the relay substrate 118 shown in FIG. 1 , but differs in that the signal conductor patterns 330a, 330b, 330c, and 330d are replaced with signal conductor patterns 1230a, 1230b, 1230c, and 1230d (also collectively referred to as signal conductor patterns 1230). Figure 3 The relay substrate 118 shown is different in that it includes ground conductor patterns 1240a, 1240b, 1240c, 1240d, and 1240e (hereinafter also collectively referred to as ground conductor patterns 1240) instead of the ground conductor patterns 340a, 340b, 340c, 340d, and 340e.

[0174] The four signal conductor patterns 1230 have Figure 3 The structure is similar to the signal conductor pattern 330 of the relay substrate 118 shown, but the difference from the signal conductor pattern 330 is that each has a bent portion downstream of the component mounting portion 350 along the propagation direction of the electrical signal.

[0175] By having these bent portions, in the signal conductor pattern 1230, the propagation direction of the downstream electrical signal is different from the propagation direction of the electrical signal in the component mounting portion 350 (therefore, the propagation direction of the leakage microwave generated from the component mounting portion 350). Therefore, in the signal conductor pattern 1230, the separation of the propagation microwave and the leakage microwave in the signal conductor pattern 1230 can be improved.

[0176] Furthermore, in the relay substrate 1118, while the separation of propagating microwaves and leakage microwaves is improved as described above, leakage microwaves are suppressed or absorbed by the conductor 360 arranged downstream thereof, so that re-coupling of leakage microwaves can be further suppressed than in the relay substrate 118, thereby achieving good optical modulation characteristics.

[0177] Next, a modification example of the relay substrate used for the optical modulator 1100 according to the second embodiment will be described.

[0178] <First Modification of Second Embodiment>

[0179] Fig.13 is a diagram showing the structure of a relay substrate 1318 according to a first modification of the second embodiment, which is equivalent to Fig.12 The relay substrate 1318 may be Fig.11 In the optical modulator 1100 shown in the figure, it is used instead of the relay substrate 1118. Fig.13 In Fig.12 The same components as those of the relay substrate 1118 shown in FIG. Fig.12The same symbols are used to represent and refer to the Fig.12 Description.

[0180] The relay substrate 1318 has Fig.12 The relay substrate 1118 shown in FIG. 1 is similar in structure to the relay substrate 1118 shown in FIG. 1 , but differs in that signal conductor patterns 1330a, 1330b, 1330c, and 1330d (hereinafter collectively referred to as signal conductor pattern 1330) are provided instead of signal conductor patterns 1230a, 1230b, 1230c, and 1230d. Signal conductor pattern 1330 has the same structure as signal conductor pattern 1230, but the curved portion provided downstream of component mounting portion 350 includes a curve without a corner. In this way, when the curved portion is configured as a curve, the signal conductor pattern 1330 is similar to signal conductor pattern 1230. Fig.12 The bent portion of the signal conductor pattern 1230 in the relay substrate 1118 shown can also improve the separation of propagation microwaves and leakage microwaves.

[0181] Furthermore, the signal conductor pattern 1330 and Figure 7 Similarly to the relay substrate 718 shown in FIG. 1 , the width of the portion downstream of the component mounting portion 350 is formed to be wider than the width of the portion upstream thereof. Thus, in the signal conductor pattern 1330, the characteristic impedance of the downstream is set to be lower than the impedance of the upstream, so that Fig.12 The separation of propagation microwaves and leakage microwaves is further improved compared to the signal conductor pattern 1230 in the relay substrate 1118. As a result, in the relay substrate 1318, the re-coupling of leakage microwaves can be further suppressed compared to the relay substrate 1118, thereby achieving good optical modulation characteristics.

[0182] <Second Modification of Second Embodiment>

[0183] Fig.14 is a diagram showing the structure of a relay substrate 1418 according to a second modification of the second embodiment, and is equivalent to Fig.12 The relay substrate 1418 may be Fig.11 In the optical modulator 1100 shown in the figure, it is used instead of the relay substrate 1118. Fig.14 In Fig.12 The same components as those of the relay substrate 1118 shown in FIG. Fig.12 The same symbols are used to represent and refer to the Fig.12 Description.

[0184] The relay substrate 1418 has Fig.12The structure is similar to the relay substrate 1118 shown in the figure, but it is different from the relay substrate 1118 in that it does not have the wire 360, and the ground conductor pattern 1240 is provided with substrate cutouts 1462, 1464, and 1466.

[0185] The substrate removal portions 1462, 1464, 1466 have Figure 8 The substrate removal portion 1462 is similar to the structure of the relay substrate 818 shown in FIG. The substrate removal portion 1462 is provided at a position sandwiching the portion of each signal conductor pattern 1230 downstream of the component mounting portion 350, as in the case of the relay substrate 818. Thus, leakage microwaves generated from the component mounting portion 350 and propagating in the substrate material of the relay substrate 1418 are suppressed.

[0186] In a structure where the signal conductor pattern 1330 in the component mounting portion 350 extends in different directions, such as in the relay substrate 1418, the leakage microwave generated from the component mounting portion 350 may propagate in different directions and be reflected by the edge of the relay substrate 1418 and propagate in a complex form. Therefore, in order to further suppress the propagation of the leakage microwave in the substrate raw material, the relay substrate 1418 is further provided with substrate removal portions 1464 and 1466. As a result, in the relay substrate 1418, it is possible to Fig.12 The relay substrate 1118 shown further suppresses the re-coupling of the leaked microwaves and realizes good optical modulation characteristics.

[0187] In addition, in the relay substrate 1418, for example, Fig.10 The relay substrate 1018 shown in the figure also uses the conductor pins 660 and / or uses Figure 3 The wires 360 of the relay substrate 118 shown can also suppress leakage microwaves propagating in space.

[0188] [Third Embodiment]

[0189] Next, the optical modulator of the third embodiment of the present invention is described. In the relay substrates 1118, 1318, and 1418 of the second embodiment and its modified examples, the signal conductor patterns 1230 and 1330 are configured to include a curved shape, but the present invention is of course not limited to such a curved shape. The signal conductor pattern is not limited to a curved shape, and can also be configured using a gentle curve with a relatively small curvature.

[0190] This embodiment is the second example of a case where the arrangement pitch of the signal electrodes of the optical modulator is smaller than the arrangement pitch of the signal input terminals 124. In particular, as described later, the curved portions of the signal conductor patterns 1630a, 1630b, 1630c, and 1630d of the relay substrate 1518 are not curved but include curves.

[0191] Fig.15 is a plan view showing the structure of an optical modulator 1500 according to a third embodiment of the present invention. Fig.16 yes Fig.15 A detailed partial view of section D in FIG. Fig.15 In Figure 1 The same components as those of the optical modulator 100 of the first embodiment shown in FIG. Figure 1 The same symbols as in the symbols, and references to the Figure 1 Description. Fig.15 The optical modulator 1500 shown has Figure 1 The light modulator 100 shown has the same structure, but differs in that it includes a light modulator 1502 and a relay substrate 1518 instead of the light modulator 102 and the relay substrate 118 .

[0192] The optical modulator 1502 has the same structure as the optical modulator 102, but differs in that it includes signal electrodes 1512a, 1512b, 1512c, and 1512d (hereinafter collectively referred to as signal electrodes 1512) instead of the signal electrode 112, and includes ground electrodes 1522a, 1522b, 1522c, 1522d, and 1522e (hereinafter collectively referred to as ground electrodes 1522) instead of the ground electrode 122.

[0193] The signal electrodes 1512 have the same structure as the signal electrodes 112, but the spacing between the signal electrodes 1512 is different from the spacing between the signal electrodes 112. Furthermore, the ground electrodes 1522 have the same structure as the ground electrodes 122, but their shapes are different from those of the ground electrodes 122 in order to form a coplanar line together with the signal electrodes 1512.

[0194] Fig.16 yes Fig.15 The partial detailed view of the D portion shown in FIG. 1 shows the structure of the relay substrate 1518 and its surroundings in the optical modulator 1500. Fig.16 In Figure 3 , Fig.12 The same components as the relay substrates 118 and 1118 shown in the figure are used. Figure 3 , Fig.12 The same symbols as in the symbols, and references to the Figure 3 , Fig.12 Description.

[0195] The relay substrate 1518 has Fig.12The relay substrate 1118 shown in FIG. 1 has the same structure as the relay substrate 1118 shown in FIG. 1 , but differs in that the signal conductor patterns 1230a, 1230b, 1230c, and 1230d are replaced with signal conductor patterns 1630a, 1630b, 1630c, and 1630d (hereinafter collectively referred to as signal conductor patterns 1630). Fig.12 The relay substrate 1118 shown is different in that it includes ground conductor patterns 1640a, 1640b, 1640c, 1640d, and 1640e (hereinafter also collectively referred to as ground conductor patterns 1640) instead of the ground conductor patterns 1240a, 1240b, 1240c, 1240d, and 1240e.

[0196] The four signal conductor patterns 1630 have Fig.12 The signal conductor pattern 1630 has the same structure as the signal conductor pattern 1230 of the relay substrate 1118 shown in the figure, but is different from the signal conductor pattern 1230 in that it does not have a bent portion but includes a curved shape. The signal conductor pattern 1630 does not have a bent portion as described above, but due to the curved shape, there is a portion downstream of the component mounting portion 350 where the propagation microwave propagates in a direction different from the propagation direction of the leakage microwave, so that in these portions, the separation of the leakage microwave and the propagation microwave can be improved to a certain extent.

[0197] Furthermore, two adjacent ground conductor patterns 1640 sandwiching the signal conductor patterns 1630 downstream of the component mounting portion 350 in the propagation direction of the electrical signal are provided with a lead wire 1660 connected to these ground conductor patterns 1640. Thus, leakage microwaves generated from the component mounting portion 350 and propagating in the air are suppressed.

[0198] The ground conductor pattern 1640 has the same structure as the ground conductor pattern 1240 , but has a different shape from the ground conductor pattern 1240 in order to form a coplanar line together with the signal conductor pattern 1630 .

[0199] Furthermore, in the ground conductor pattern 1640, a substrate removal portion 1662 is provided at a position sandwiching a portion of the signal conductor pattern 1630 located downstream of the component mounting portion 350 in the propagation direction of the electric signal. The substrate removal portion 1662, like the substrate removal portion 862 and the like, suppresses leakage microwaves generated from the component mounting portion 350 and propagating in the substrate material of the relay substrate 1518.

[0200] Through the above structure, in the relay substrate 1518, the separation of propagating microwaves and leakage microwaves in the signal conductor pattern 1630 can be improved, and the re-coupling of leakage microwaves propagating in the air and inside the substrate raw material can be suppressed, thereby achieving good optical modulation characteristics.

[0201] [Fourth Embodiment]

[0202] Next, the fourth embodiment of the present invention is described. This embodiment is an optical transmitter 2100 equipped with the optical modulator 100 including the relay substrate 118 of the first embodiment. In addition, this structure is an example, and the optical modulator 100 using the relay substrates 418, 718, 818, 918, 1018 of the first to fifth variants of the first embodiment, the optical modulator 1100 using the relay substrates 1318 and 1418 of the second embodiment and its variants, and the optical modulator 1500 of the third embodiment may be mounted on the optical transmitter 2100 instead of the optical modulator 100 including the relay substrate 118.

[0203] Fig.17 2 is a diagram showing the structure of an optical transmission device 2100 according to the present embodiment. The optical transmission device 2100 includes an optical modulator 100 , a light source 2104 for causing light to enter the optical modulator 100 , a modulation signal generator 2106 , and a modulation data generator 2108 .

[0204] The modulation data generation unit 2108 receives transmission data given from the outside, generates modulation data for sending the transmission data (for example, converts or processes the transmission data into data in a specified data format), and outputs the generated modulation data to the modulation signal generation unit 2106.

[0205] The modulation signal generating unit 2106 is an electronic circuit (driving circuit) that outputs an electrical signal for causing the optical modulator 100 to perform a modulation operation. Based on the modulation data output by the modulation data generating unit 2108, the modulation signal is generated as a high-frequency signal for causing the optical modulator 100 to perform an optical modulation operation according to the modulation data, and is input to the optical modulator 100. The modulation signal includes four high-frequency electrical signals corresponding to the four signal electrodes 112a, 112b, 112c, and 112d of the optical modulation element 102 included in the optical modulator 100.

[0206] The four high-frequency electrical signals are input from the respective signal input terminals 124a, 124b, 124c, 124d of the electrical connectors 116a, 116b, 116c, 116d of the optical modulator 100 to the signal conductor patterns 330a, 330b, 330c, 330d of the relay substrate 118, and are input to the signal electrodes 112a, 112b, 112c, 112d of the optical modulator element 102 via these signal conductor patterns 330a etc.

[0207] As a result, the light output from the light source 2104 is modulated by, for example, DP-QPSK by the optical modulator 100 , becomes modulated light, and is output from the optical transmission device 2100 .

[0208] In particular, in the optical transmitting device 2100, the optical modulator 100 is used, so that changes in the frequency characteristics of the signal conductor pattern 330 caused by leakage microwaves that may be generated from the component mounting portion 350 can be suppressed in the relay substrate 118, thereby ensuring good modulation characteristics and achieving good transmission characteristics.

[0209] The present invention is not limited to the configurations of the above-described embodiment and its modified examples, but can be implemented in various forms within the scope not departing from the gist of the invention.

[0210] For example, in the first embodiment, the second embodiment, and their variations and the third embodiment, a component mounting portion 350 is provided in each of the signal conductor patterns 330, 1230, 1330, and 1630, but the present invention is not limited thereto. It is sufficient that at least one component mounting portion 350 is provided in one relay substrate according to the degree of stability of the frequency characteristics in the signal conductor pattern required for the optical modulator, and a plurality of component mounting portions 350 may be provided for the same signal conductor pattern. That is, at least one component mounting portion 350 may be provided in at least one signal conductor pattern. In addition, when a plurality of component mounting portions are provided in the same signal conductor pattern, a recoupling suppression structure including the metal body (conducting wire, conductor strip, conductor pin, etc.) or a substrate removal portion may be provided downstream of each component mounting portion.

[0211] Furthermore, in the first embodiment, the second embodiment, their modified examples, and the third embodiment, the wire 360, the conductor pin 660, the substrate cutout portion 862, etc., which are metal bodies, are provided respectively on the two ground conductor patterns 340 sandwiching the signal conductor pattern 330, but the present invention is not limited thereto. The wire 360, the conductor pin 660, the substrate cutout portion 862, etc. may be provided only on one of the two ground conductor patterns 340 sandwiching the signal conductor pattern 330. Even in the case of such a configuration, the propagation of the leakage microwave can be suppressed to a certain extent, and the change in the frequency characteristic of the signal conductor pattern 330 as a whole including the component mounting portion 350 can be suppressed, thereby realizing a good optical modulation characteristic.

[0212] In addition, the direction of the major diameter of the substrate removal portion 862 described as an elliptical shape on the relay substrate 118 is not limited to the direction of the major diameter of the substrate removal portion 862 described as an elliptical shape on the relay substrate 118. Figure 8 , Fig. 9 , Fig.10 , Fig.14 , Fig.16The direction in which the major diameter of the elliptical substrate cutout portion on the relay substrate extends may be any direction as long as the propagation of the leakage microwave in the relay substrate can be prevented, for example.

[0213] Furthermore, in the above-described embodiment, the optical modulation element 102 and the relay substrate 118 are housed in the frame 104 , but in addition to these, electronic circuit elements (driver elements) for operating the optical modulation element 102 and the like may also be housed in the frame 104 .

[0214] As described above, the optical modulator 100 of the first embodiment includes: the optical modulator 102 including a plurality of signal electrodes 112, the relay substrate 118, and the frame 104 accommodating the optical modulator 102 and the relay substrate 118. The optical modulator 102 is configured to generate two modulated lights 106a and 106b respectively modulated according to two sets of electrical signals respectively including two electrical signals. The relay substrate 118 is formed with a plurality of signal input terminals 124 for inputting electrical signals respectively applied to the signal electrodes 112, a plurality of signal conductor patterns 330 for electrically connecting the signal input terminals 124 and the signal electrodes 112, and a plurality of ground conductor patterns 340. Moreover, the relay substrate 118 is configured to propagate the two sets of electrical signals respectively through two pairs of signal conductor patterns 330 respectively including two adjacent signal conductor patterns 330. Furthermore, at least one signal conductor pattern 330 has at least one component mounting portion 350 including, for example, a parallel circuit of at least a thin film resistor 352c and a capacitor 354c. Furthermore, the relay substrate 118 has a conductive wire 360 ​​as a metal body connected to the ground conductor pattern 340, which is provided at a position downstream of the component mounting portion 350 along the propagation direction of the electrical signal sandwiching at least one signal conductor pattern 330. In this case, the optical modulator 100 may include: the relay substrate 618 including the conductive pin 660 as a metal body, or the relay substrate 818 having a substrate removal portion 862 provided in place of or in addition to the metal body and in which the substrate material is removed.

[0215] According to this structure, in the optical modulator 100 in which the component mounting portion 350 including the electric circuit element such as the electric filter is provided in the signal conductor pattern 330, it is possible to suppress the re-coupling of the leakage microwave that may be generated from the component mounting portion 350 to the signal conductor pattern 330 (or the propagation microwave inside thereof). As a result, for example, the fluctuation of the frequency characteristic of the signal conductor pattern 330 as a whole including the component mounting portion 350, which is the electric filter, can be suppressed, thereby realizing good optical modulation characteristics.

[0216] Furthermore, in the optical modulator 100, the metal body (conducting wire 360 ​​or conductor pin 660) or substrate cutout portion 862 is disposed at a distance shorter than the wavelength of the electric signal, i.e., the high-frequency signal, from the end of the electric circuit element (e.g., capacitor 354c) constituting the component mounting portion 350 along the propagation direction of the electric signal. According to this structure, it is possible to effectively prevent leakage microwaves from propagating in the air and / or inside the substrate material, thereby achieving good modulation characteristics.

[0217] Furthermore, in the optical modulator 100, the metal body (conductor wire 360 ​​or conductor pin 660) is formed to be higher than the height of the electric circuit element (for example, capacitor 354c) constituting the component mounting portion 350. According to this structure, it is possible to effectively prevent leakage microwaves from propagating in the air and / or inside the substrate material, thereby achieving good modulation characteristics.

[0218] Furthermore, the optical modulator 100 may include a relay substrate 718. In the relay substrate 718, in at least one signal conductor pattern 730, a characteristic impedance downstream of the component mounting portion 350 in the propagation direction of the electrical signal is set lower than a characteristic impedance upstream.

[0219] According to this structure, the separation of the propagation microwave and the leakage microwave downstream of the signal conductor pattern 730 can be improved, thereby further suppressing the re-coupling of the leakage microwave. As a result, the change of the frequency characteristics of the signal conductor pattern 730 as a whole including the component mounting portion 350 can be suppressed, thereby achieving good optical modulation characteristics.

[0220] In the relay substrate 718 that the optical modulator 100 may include, the portion where the characteristic impedance is set to be low is provided by forming the width of the signal conductor pattern 730 to be wider than the width of the upstream signal conductor pattern 730. According to this structure, the portion with low characteristic impedance can be easily formed without complicated design, thereby realizing good optical modulation characteristics.

[0221] Furthermore, the optical modulator may be the optical modulator 1100 including the relay substrate 1118 of the second embodiment. In the relay substrate 1118, the signal conductor pattern 1230 has a curved portion at a position downstream of the component mounting portion 350 along the propagation direction of the electric signal. According to this structure, the propagation direction of the propagating microwave in the downstream portion can be made different from the propagation direction of the leakage microwave, and the separation of the two can be improved, thereby further suppressing the re-coupling of the leakage microwave. As a result, the frequency characteristic of the signal conductor pattern 1230 including the component mounting portion 350 can be suppressed from changing as a whole, thereby realizing good optical modulation characteristics.

[0222] Furthermore, the metal body provided in the relay substrate of the optical modulator 100 may include the wire 360 ​​included in the relay substrate 118 or a conductor strip as a substitute thereof, or the conductor pin 660 included in the relay substrate 618, at least one end of which is connected to the ground conductor pattern 340 or the like. According to this structure, it is possible to suppress the re-coupling of the leakage microwave with a simple structure without using special parts, thereby realizing good optical modulation characteristics.

[0223] Furthermore, the substrate cutout 862 of the relay substrate 818 that may be included in the optical modulator 100 may be provided as a guide hole or a through hole. According to this structure, a structure commonly used in relay substrates can be used to suppress re-coupling of leaked microwaves with a simple structure, thereby achieving good optical modulation characteristics.

[0224] Furthermore, the optical transmitter 2100 of the fourth embodiment includes any one of the optical modulators 100 and 1100 of the first and second embodiments or the optical modulators 100 and 1100 using the relay substrates of their modified examples, or the optical modulator 1500 of the third embodiment, and includes an electronic circuit that outputs an electrical signal for causing the optical modulator to perform a modulation operation, i.e., a modulation signal generator 2106. According to this structure, for example, the change in the frequency characteristic of the signal conductor pattern caused by the recoupling of the leakage microwave, which becomes significant with the increase in the transmission rate, can be suppressed, thereby realizing stable and good transmission characteristics.

Claims

1. An optical modulator, characterized in that: include: The light modulation element includes a plurality of signal electrodes and is configured to generate two modulated lights respectively modulated by two sets of electrical signals each including two electrical signals; A plurality of signal input terminals for inputting electrical signals applied to the signal electrodes respectively; a relay substrate having a plurality of signal conductor patterns and a plurality of ground conductor patterns for electrically connecting the signal input terminal and the signal electrode, and configured to propagate the two sets of electrical signals respectively through two pairs of the signal conductor patterns each including two adjacent signal conductor patterns; as well as a frame body, accommodating the light modulation element and the relay substrate, and At least one of the signal conductor patterns has at least one component mounting portion including a parallel circuit of at least a resistor and a capacitor, The relay substrate has a metal body connected to the ground conductor pattern or a substrate removal portion where the substrate material of the relay substrate is removed, which is provided at a position downstream of the component mounting portion along the propagation direction of the electrical signal sandwiching the at least one signal conductor pattern. At least one of the signal conductor patterns has a bent portion downstream of the component mounting portion along a propagation direction of the electrical signal.

2. The optical modulator according to claim 1, characterized in that The metal body or the substrate removal portion is disposed at a distance shorter than a wavelength of a high-frequency signal as the electrical signal from an end of an electrical circuit element constituting the component mounting portion along a propagation direction of the electrical signal.

3. The optical modulator according to claim 1 or 2, characterized in that: The metal body is formed to be higher than the height of the electric circuit element constituting the component mounting portion.

4. The optical modulator according to claim 1 or 2, characterized in that: In the at least one signal conductor pattern, a characteristic impedance downstream of the component mounting portion along the propagation direction of the electrical signal is set lower than a characteristic impedance upstream.

5. The optical modulator according to claim 4, characterized in that The portion where the characteristic impedance is set low is provided by forming the width of the at least one signal conductor pattern to be wider than the width of the upstream signal conductor pattern.

6. The optical modulator according to claim 1 or 2, characterized in that: The metal body includes a conductive wire, a conductive strip, or a conductive pin, at least one end of which is connected to the ground conductor pattern.

7. The optical modulator according to claim 1 or 2, characterized in that: The substrate removal portion is a guide hole or a through hole.

8. An optical transmitting device, characterized in that: include: The optical modulator according to any one of claims 1 to 7; as well as The electronic circuit outputs an electrical signal for causing the optical modulator to perform a modulation operation.

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