Optical modulator and optical transmitting device

Abstract

The present invention provides an optical modulator and an optical transmitting device, which realize good optical modulation characteristics. An optical modulator comprises: a relay substrate having a signal conductor pattern and a ground conductor pattern for connecting a signal input terminal to a signal electrode of an optical modulation element; and a frame, wherein the signal conductor pattern has a component mounting portion including an electrical circuit element, and two ground conductor patterns sandwiching the signal conductor pattern are formed asymmetrically with respect to a straight line extending along the extension direction of the signal conductor pattern in the component mounting portion within a component mounting range of a top-view square centered on the component mounting portion, wherein the top-view square, i.e., the component mounting range, is a direction with the extension direction of the signal conductor pattern in the component mounting portion as one side, and a distance from the center of the component mounting portion to a portion on the adjacent signal conductor pattern closest to the center as the length of one side.

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 cooperatively perform the DP-QPSK modulation operation.

[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.15 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.16 Yes means Fig.15 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 provided with component mounting portions 2250a, 2250b, 2250c, and 2250d (hereinafter also generally referred to as component mounting portions 2250) on which, for example, electric filters for improving high frequency characteristics are mounted. Fig.17 as well as Fig.18 yes Fig.16 A partial detailed view of the J portion of the relay substrate 2218 shown in FIG. Fig.16 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 (a cross-hatching 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 in a desired thickness in a manner that a portion of the signal conductor pattern 2230b has a desired resistance value, for example, the portion is formed to be thinner than the thickness of other portions. Moreover, the capacitor 2254b is, for example, 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, 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, for example, by wire bonding using a wire 2270. Thus, the component mounting portion 2250b constitutes an electric filter in which the thin film resistor 2252b and the capacitor 2254b are connected 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. With the high frequency of the modulator operation, as the electrical circuit element (capacitor 2254b, etc.) mounted on the 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 become a discontinuous point for 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.16 ) 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, in an optical modulator such as the optical modulator 2200 in which DP-QPSK modulation is performed cooperatively by high-frequency electric signals given to a plurality of signal electrodes 2212, it is desired that all high-frequency electric signals are input to the signal electrodes 2212 of the optical modulator element 2202 without being affected by noise, etc. The generation of noise as described above may have an adverse effect on the operation of the optical modulator element 2202.

[0018] Furthermore, the demand for miniaturization of the optical modulator 2200 remains unchanged, and the miniaturization of the relay substrate 2218 is being promoted along with the miniaturization of the housing 2204 of the optical modulator 2200. As a result, in the narrow relay substrate 2218, a plurality of different high-frequency signals are closely and concentratedly propagated, and the electrical crosstalk between high-frequency signal lines such as the signal conductor pattern 2230 due to the leakage microwave as described above is gradually becoming impossible to ignore.

[0019] That is, in the conventional optical modulator, it is required to reduce the crosstalk between high-frequency electric signals caused by the leakage microwave that may be generated from the component mounting portion provided on the relay substrate, and to realize good modulation characteristics.

[0020] Prior art literature

[0021] Patent Literature

[0022] Patent Document 1: Japanese Patent Application Publication No. 2009-244325

[0023] Patent Document 2: Japanese Patent Application Publication No. 2018-54929 Summary of the invention

[0024] Problems to be solved by the invention

[0025] Based on the above background, it is required that in an optical modulator, in a relay substrate that electrically connects each signal electrode of the optical modulator element with each signal input terminal, the influence of leakage microwaves that may be generated from a portion where electrical circuit elements constituting an electrical filter, etc. are provided be effectively suppressed to achieve good optical modulation characteristics.

[0026] Technical means of solving problems

[0027] One embodiment of the present invention is an optical modulator, comprising: an optical modulator element including a plurality of signal electrodes; a plurality of signal input terminals for inputting electrical signals respectively applied to the signal electrodes; a relay substrate formed with a plurality of signal conductor patterns and a plurality of ground conductor patterns for electrically connecting the signal input terminals to the signal electrodes; and a frame for accommodating the optical modulator element and the relay substrate, wherein at least one of the signal conductor patterns has at least one part mounting portion including an electrical circuit element, and two of the ground conductor patterns sandwiching the at least one signal conductor pattern on the relay substrate have plan view shapes that are asymmetrically formed with respect to a straight line extending along an extension direction of the at least one signal conductor pattern in the part mounting portion within a part mounting range of a plan view square centered on the part mounting portion, the range of the plan view square, i.e., the part mounting range, is a direction with the extension direction of the at least one signal conductor pattern in the part mounting portion as one side, and a distance from the center of the part mounting portion to a portion of the signal conductor pattern that is closest to the center as the length of one side.

[0028] Another embodiment of the present invention is an optical modulator, comprising: an optical modulator element, including multiple signal electrodes; multiple signal input terminals, inputting electrical signals respectively applied to the signal electrodes; a relay substrate, formed with multiple signal conductor patterns and multiple ground conductor patterns that electrically connect the signal input terminals to the signal electrodes; and a frame, accommodating the optical modulator element and the relay substrate, wherein at least one of the signal conductor patterns has at least one part mounting portion including an electrical circuit element, and the two ground conductor patterns sandwiching the at least one signal conductor pattern on the relay substrate are formed asymmetrically within a part mounting range of a top-view square centered on the part mounting portion by the presence or absence of through holes, the diameter of the through holes or the number of through holes being different from each other, and the part mounting range is a top-view square range with the extension direction of the at least one signal conductor pattern in the part mounting portion as the direction of one side and the distance from the at least one signal conductor pattern to the nearest adjacent signal conductor pattern as the length of one side.

[0029] According to another aspect of the present invention, the two ground conductor patterns are formed so that distances from respective edges of the two ground conductor patterns to opposing edges of the at least one signal conductor pattern have portions that are different from each other within the component mounting range.

[0030] According to another aspect of the present invention, one of the two grounding conductor patterns includes the following portion within the part mounting range, wherein the width of the portion measured in a direction orthogonal to the extension direction of at least one of the signal conductor patterns is narrower than the width of the other of the two grounding conductor patterns.

[0031] According to another aspect of the present invention, one of the two ground conductor patterns has a blocked section within the component mounting range, and the other ground conductor pattern has no blocked section within the component mounting range.

[0032] According to another aspect of the present invention, the other grounding conductor pattern of the two grounding conductor patterns has the following portion, which is formed so that the separation distance to the portion of the signal conductor pattern constituting the component mounting portion is longer than the separation distance to other portions of the signal conductor pattern within the corresponding component mounting range.

[0033] According to another aspect of the present invention, the optical modulation element is configured to generate two modulated lights modulated according to the pair of electrical signals, respectively, and the relay substrate is configured to propagate the pair of electrical signals through a pair of adjacent signal conductor patterns.

[0034] Another embodiment of the present invention is an optical transmitting device, comprising: any one of the above-mentioned optical modulators; and an electronic circuit that outputs an electrical signal for causing the optical modulator to perform a modulation operation.

[0035] Effects of the Invention

[0036] According to the present invention, the influence of leakage microwaves that may be generated from a component mounting portion on which an electric circuit element is provided in a relay substrate can be effectively suppressed, thereby achieving good light modulation characteristics.

[0037] In addition, this specification includes the entire content of Japanese Patent Application No. 2019-146242 filed on August 8, 2019. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a plan view of the optical modulator according to the first embodiment of the present invention.

[0039] Figure 2 yes Figure 1 Side view of the light modulator shown.

[0040] Figure 3 yes Figure 1 Detailed view of section A of the light modulator shown.

[0041] Figure 4 This is a diagram showing another example of the parts mounting portion.

[0042] Figure 5 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 6 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 7 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] Figure 8 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. 9 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.10 It is a diagram showing the structure of a relay substrate according to a sixth modified example of the optical modulator according to the first embodiment.

[0048] Fig.11It is a diagram showing the structure of a relay substrate according to a seventh modification example of the optical modulator according to the first embodiment.

[0049] Fig.12 It is a diagram showing the structure of a relay substrate according to an eighth modification example of the optical modulator according to the first embodiment.

[0050] Fig.13 It is a diagram showing the structure of a relay substrate according to a ninth modified example of the optical modulator according to the first embodiment.

[0051] Fig.14 It is a diagram showing the structure of an optical transmission device according to a second embodiment of the present invention.

[0052] Fig.15 This is a diagram showing an example of the structure of a conventional optical modulator.

[0053] Fig.16 This is a partial detailed view showing the periphery of a relay substrate in a conventional optical modulator.

[0054] Fig.17 Yes means Fig.16 A detailed partial detailed view of section J is shown.

[0055] Fig.18 yes Fig.17 The XVIII-XVIII cross-sectional arrow diagram of the partial detailed diagram shown.

[0056] [Explanation of Symbols]

[0057] 100, 2102, 2200: Optical modulator

[0058] 102, 2202: Light modulation element

[0059] 104, 1604, 2204: Frame

[0060] 108, 2208: Input fiber

[0061] 110, 2210: Output fiber

[0062] 112, 112a, 112b, 112c, 112d, 2212, 2212a, 2212b, 2212c, 2212d: signal electrodes

[0063] 114a, 2214a: Shell

[0064] 114b, 2214b: hood

[0065] 116, 116a, 116b, 116c, 116d, 2216, 2216a, 2216b, 2216c, 2216d: electrical connector

[0066] 118, 518, 618, 718, 818, 918, 1018, 1118, 1218, 1318, 1418, 2218: Relay substrate

[0067] 120, 2220: Terminal

[0068] 122, 122a, 122b, 122c, 122d, 122e, 2222a, 2222b, 2222c, 2222d, 2222e: grounding electrode

[0069] 124, 124a, 124b, 124c, 124d, 2224, 2224a, 2224b, 2224c, 2224d: Signal input terminals

[0070] 126a, 126b, 2226a, 2226b: Output optical waveguide

[0071] 318a: Signal input edge

[0072] 318b: Signal output edge

[0073] 318c, 318d: side edge

[0074] 326, 2270: Wire

[0075] 330, 330a, 330b, 330c, 330d, 2230, 2230a, 2230b, 2230c, 2230d: signal conductor pattern

[0076] 340, 340a, 340b, 340c, 340d, 340e, 340f, 540c, 540d, 740a, 740f, 840c, 840d, 940b, 940e, 1040a, 1040b, 1040c, 1040d, 1040e, 1040f, 1140a, 1140c, 1140d, 1140f, 1240a, 1240b, 1240c, 1240d, 1240e, 1240f, 1340a, 1340b, 1340c, 1340d, 1340e, 1340f, 2240a, 2240b, 2240c, 2240d, 2240e: Ground conductor pattern

[0077] 342a, 342b, 342c, 342d: notch

[0078] 350a, 350b, 350c, 350d, 2250a, 2250b, 2250c, 2250d: Parts mounting section

[0079] 352a, 352b: Electrical circuit elements

[0080] 360a, 360b, 360c, 360d, 2260a, 2260b, 2260c, 2260d: Parts loading range

[0081] 362a: Shape Center

[0082] 362b: Direction of transmission

[0083] 742a, 742d, 842b, 842c: interval

[0084] 942, 942a, 942b, 942c, 942d, 1276, 1276a, 1276b, 1276c, 1276d: recess

[0085] 1070, 1072, 1370: Through hole

[0086] 1174a, 1174b, 1174c, 1174d, 1274a, 1274b, 1274c, 1274d: Narrow width

[0087] 2100: Optical transmitter

[0088] 2104: Light Source

[0089] 2106: Modulation signal generation unit

[0090] 2108: Modulation data generation unit

[0091] 2252b: Thin Film Resistors

[0092] 2254b: Capacitor

[0093] 2290: Leaking Microwaves

[0094] w11, w12, w13, w14, w21, w22: distance (spacing) DETAILED DESCRIPTION

[0095] The present invention changes the direction of microwaves that may leak from the component mounting portion of the relay substrate by setting the electrode structure around the component mounting portion to be asymmetric, so as to reduce the influence on its own signal electrode or adjacent signal electrode, etc. Specifically, the optical modulator shown in the following embodiment and its modified example includes: an optical modulation element; and a relay substrate, which is provided with a component mounting portion including an electrical circuit element. In addition, in these optical modulators, in order to solve the above-mentioned problem, in a specified component mounting range of at least one signal conductor pattern provided with a component mounting portion, two ground conductor patterns sandwiching the at least one signal conductor pattern are formed asymmetrically with respect to the extension direction of the signal conductor pattern. Specifically, in the component mounting range, the separation distance between the signal conductor pattern and the two adjacent ground conductor patterns is asymmetric, or the widths of the two ground conductor patterns are asymmetric, or the presence or absence of through holes, the diameter of the through holes and / or the number of through holes in the two ground conductor patterns are different. As a result, in the optical modulator, the intensity of the leaked microwaves generated from the component mounting portion and directed toward the adjacent signal conductor pattern is reduced, and the crosstalk with the adjacent signal conductor pattern is reduced.

[0096] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0097] [First embodiment]

[0098] 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.

[0099] 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 .

[0100] The optical modulator 102 is, for example, a DP-QPSK modulator that performs optical modulation at 400 Gb / s, and includes, for example, four Mach-Zehnder optical waveguides provided on an LN substrate. The four Mach-Zehnder optical waveguides are provided with four signal electrodes 112a, 112b, 112c, and 112d (hereinafter, also collectively referred to as signal electrodes 112) that modulate the light waves propagating in the Mach-Zehnder optical waveguides, respectively. Furthermore, as is known in the prior art, ground electrodes 122a, 122b, 122c, 122d, and 122e are provided on the surface of the LN substrate of the optical modulator 102 (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).

[0101] 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.

[0102] 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.

[0103] 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 modulated according to the respective pairs of electrical signals. The two modulated lights generated are outputted from two output optical waveguides 126a and 126b, respectively, which constitute a part of the optical modulation element 102. In the present embodiment, the two high-frequency electrical signals constituting one pair are applied to the signal electrodes 112a and 112b to generate modulated light 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 modulated light outputted from the output optical waveguide 126b. The two modulated lights are combined into one beam by the polarization combining unit 128 including a polarization combining prism, etc., and then outputted to the outside of the frame 104 via the output optical fiber 110.

[0104] 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 left side of the figure, but in fact, the cover 114b is arranged in a manner to cover the entire box-shaped housing 114a, and the interior 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 direct current (DC) control, but these are omitted in this figure.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] Figure 3 The relay substrate 118 and its surrounding structure are shown. The relay substrate 118 is provided with signal conductor patterns 330a, 330b, 330c, and 330d (hereinafter, also collectively referred to as signal conductor patterns 330) and ground conductor patterns 340a, 340b, 340c, 340d, 340e, and 340f (hereinafter, also collectively referred to as ground conductor patterns 340).

[0109] 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.

[0110] The ground conductor patterns 340a, 340b, 340c, 340d, 340e, and 340f are provided so as to sandwich the signal conductor patterns 330a, 330b, 330c, and 330d in the surface of the relay substrate 118. Thus, the signal conductor patterns 330 and the ground conductor patterns 340 form coplanar lines.

[0111] 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.

[0112] 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 gold 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.

[0113] The ground electrode 122 constituting the coplanar line together with the signal electrode 112 in the optical modulation element 102 is electrically connected to one end of each of the ground conductor patterns 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, ribbon bonding using, for example, a conductor ribbon such as a gold ribbon may be used.

[0114] The signal conductor patterns 330a, 330b, 330c, and 330d each have a portion (a portion marked with a black shadow in the figure) where, for example, an electrical circuit element constituting an electrical filter is provided, namely, a component mounting portion 350a, 350b, 350c, and 350d (hereinafter, also collectively referred to as a component mounting portion 350). Here, the so-called electrical circuit element refers to an active element and / or a passive element as a functional element constituting a circuit, and does not include a wiring pattern or a pad (solder pad) specially provided for electrical connection.

[0115] The component mounting portion 350 may be connected to Fig.17 , Fig.18 Similarly to the component mounting portion 2250b shown in FIG. 1 , an electrical circuit element such as a capacitor is mounted on a portion of the signal conductor pattern 330 which is provided wider than other portions, and / or an electrical circuit element such as a thin film resistor is formed. Fig.17 , Fig.18 Similar to the signal conductor pattern 2230b shown, a wide portion is formed in the signal conductor pattern 330 and a capacitor similar to the capacitor 2254b is mounted thereon, and a thin film resistor similar to the thin film resistor 2252b is formed in a portion of the wide portion of the signal conductor pattern 330, thereby forming a component mounting portion 350.

[0116] In the present embodiment, in particular, the two ground conductor patterns 340a and 340b sandwiching the signal conductor pattern 330a on the relay substrate 118 are formed in a plan view shape that is asymmetrical to each other with respect to a straight line extending along the extension direction of the signal conductor pattern 330a in the part mounting portion 350a within a part mounting range 360a of a plan view square centered on the part mounting portion 350a.

[0117] Moreover, the part mounting range 360a is defined as the range of a top-down square as described below, wherein the top-down square has the extension direction of the signal conductor pattern 330a in the part mounting portion 350a as the direction of one side, and has the distance (spacing) w11 from the center of the part mounting portion 350a to the portion on the adjacent signal conductor pattern 330b closest to the center (for example, the width direction center of the signal conductor pattern 330b of the portion) as the length of one side.

[0118] Here, the center of the component mounting portion 350 may be set to the center of any one of the electrical circuit elements included in the component mounting portion 350, or the center of a circumscribed rectangle (described later) including the electrical circuit elements constituting the component mounting portion 350. Figure 3 In the figure, for the purpose of explanation, the boundary lines in the width direction of the component mounting portion 350 (the boundary lines on the left and right in the figure) represent the edge positions of the corresponding signal conductor patterns 330 in the width direction of the component mounting portion 350. Figure 3 In the embodiment, the width of the component mounting portion 350 in the signal conductor pattern 330 is wider than other portions, but the invention is not limited thereto. The width of the component mounting portion 350 in the signal conductor pattern 330 may be the same as other portions, or may be narrower than other portions.

[0119] In this embodiment, the ground conductor pattern 340a has a notch 342a (the shaded portion shown in the figure), and thus the ground conductor patterns 340a and 340b are formed so that the distance (gap) from the edges of the ground conductor patterns 340a and 340b to the edges facing each other of the signal conductor pattern 330a has different portions (i.e., asymmetric portions) in the component mounting range 360a. In addition, in this embodiment, the signal conductor pattern 330 is formed parallel to the side edge 318d and in a straight line, so the length w11 of one side of the component mounting range 360a is equal to the distance (pitch) w21 between the width direction center line of the signal conductor pattern 330a and the width direction center line of the signal conductor pattern 330b. That is, w11=w21.

[0120] In addition, the signal conductor pattern 330a and the ground conductor patterns 340a and 340b can be formed by adjusting the spacing (separation distance) between these conductor patterns or the formation width of the signal conductor pattern 330a, so that the characteristic impedance of the signal conductor pattern 330a becomes a specified value, for example, inside and outside the part mounting portion 350a.

[0121] Generally speaking, in a high-frequency signal line including a signal conductor and a ground conductor, the smaller the distance between the signal conductor and the ground conductor, the stronger the high-frequency signal is confined in the signal conductor.

[0122] In the relay substrate 118, there are portions where the distances between the signal conductor pattern 330a and the ground conductor patterns 340a and 340b are different within the component mounting range 360a. Therefore, the leakage microwave generated from the component mounting portion 350a is emitted in a manner such that it is biased toward the direction of the ground conductor pattern 340a, which is the direction with a larger distance from the adjacent ground conductor pattern (for example, in the direction of the ground conductor pattern 340a). Figure 3 In the figure, it is within the direction range sandwiched by the arrows of the two dot chain lines extending from the component mounting portion 350a), and has greater strength than in other directions.

[0123] On the other hand, the signal conductor pattern 330a can be constructed to have the same characteristic impedance inside and outside the component mounting range 360a, for example, so that the total amount of leakage microwaves generated from the component mounting portion 350a is roughly the same as when the ground conductor patterns 340a and 340b are formed symmetrically.

[0124] As a result, the intensity of the leakage microwave in directions other than the direction range sandwiched by the dot-chain arrows is relatively reduced, and the crosstalk from the signal conductor pattern 330a to 330b caused by the leakage microwave generated from the component mounting portion 350a is reduced.

[0125] Similarly, in the present embodiment, the grounding conductor patterns 340e and 340f are configured such that the grounding conductor pattern 340f has a notch portion 342d (the shaded portion shown in the figure), whereby the spacing distance (gap) from the edges of each of the grounding conductor patterns 340e and 340f to the opposing edges of the signal conductor pattern 330d has different portions within the component mounting range 360d.

[0126] Here, the component mounting range 360d is defined as the range of a square in top view, which has the extension direction of the signal conductor pattern 330d in the component mounting portion 350d as one side and the distance (pitch) w12 from the center of the component mounting portion 350d to the portion of the signal conductor pattern 330c that is closest to the center (for example, the width center of the signal conductor pattern 330c of the portion) as the length of one side. In addition, in the present embodiment, the signal conductor pattern 330 is formed parallel to the side edge 318d and in a straight line, so the length w12 of one side of the component mounting range 360d is equal to the distance (pitch) w22 between the width center line of the signal conductor pattern 330d and the width center line of the signal conductor pattern 330c. That is, w12=w22.

[0127] Thus, the ground conductor patterns 340e and 340f are formed in the component mounting range 360d to have a plan view shape that is asymmetric to each other with respect to a straight line extending along the extension direction of the signal conductor pattern 330d in the component mounting portion 350d, so that the leakage microwave generated from the component mounting portion 350d is not transmitted to the component mounting portion 350d, for example. Figure 3 In the direction range sandwiched by the two dot chain arrows extending from the component mounting portion 350d, the intensity is greater than in other directions. As a result, the crosstalk from the signal conductor pattern 330d to 330c caused by the leakage microwave generated from the component mounting portion 350d is reduced.

[0128] In particular, in an optical modulator that generates two modulated lights modulated according to a pair of high-frequency electrical signals, such as the optical modulator 100 that performs DP-QPSK modulation, the two paired high-frequency electrical signals often carry information in the phase difference between each other. Therefore, the crosstalk between the two paired high-frequency electrical signals generates phase noise in addition to intensity noise, which may have a greater impact on the modulation characteristics of the optical modulator 100 than the crosstalk between unpaired high-frequency electrical signals.

[0129] The paired high-frequency electrical signals are generally relayed using two adjacent signal conductor patterns on a relay substrate, and therefore it is extremely important to suppress crosstalk between the two adjacent signal conductor patterns.

[0130] In the optical modulator 100 of the present embodiment, the structure is such that two high-frequency electrical signals in one pair of two pairs of high-frequency electrical signals are propagated through adjacent signal conductor patterns 330a and 330b, respectively, and the other pair of two high-frequency electrical signals are propagated through the other adjacent signal conductor patterns 330c and 330d. In addition, with the aid of the structure, the crosstalk from the signal conductor pattern 330a to the signal conductor pattern 330b, that is, the crosstalk from one of the two high-frequency electrical signals constituting one pair to the other is reduced. In addition, with the aid of the structure, the crosstalk from the signal conductor pattern 330d to the signal conductor pattern 330c, that is, the crosstalk from one of the two high-frequency electrical signals constituting the other pair to the other is also reduced. As a result, in the optical modulator 100, the influence of the leakage microwave can be effectively reduced, thereby achieving good optical modulation characteristics.

[0131] In addition, in this embodiment, the component mounting portion 350 has Fig.17 , Fig.18 The component mounting portion 2250b shown in FIG. 1 may have the same structure as the component mounting portion 2250b, but is not limited thereto. Figure 4 As shown, the signal conductor pattern 330a is cut and inserted, and two chip parts, namely, electrical circuit elements 352a and 352b, are connected in parallel along the surface direction of the relay substrate. At this time, the range of the component mounting portion 350 can be set to include the range of the circumscribed rectangle (a rectangle with a dotted chain line in the figure) of the electrical circuit elements 352a and 352b constituting the component mounting portion 350.

[0132] In this case, the center of the component mounting portion 350a may be set to the center of a rectangle of a dotted chain line representing the range of the component mounting portion 350a. Alternatively, the center of the shape of any one of the plurality of electrical circuit elements 352a and 352b constituting the component mounting portion 350a (for example, Figure 4 The shape center 362a of the electric circuit element 352a indicated by a plus sign in the figure is set as the center of the component mounting portion 350a.

[0133] Moreover, when the signal conductor pattern 330 has a cutout portion in the component mounting portion 350, the extension direction of the signal conductor pattern 330 in the component mounting portion 350 can be set to be the propagation direction of a high-frequency signal flowing into the signal conductor pattern 330 or the propagation direction of a high-frequency signal flowing out of the signal conductor pattern 330 with respect to any electrical circuit element included in the component mounting portion 350. In addition, Figure 4 In FIG. 3 , as an example, a propagation direction 362b of a high-frequency signal flowing from a signal conductor pattern with respect to the electric circuit element 352a is depicted as an extending direction of the signal conductor pattern 330a in the component mounting portion 350a.

[0134] In addition, in the present embodiment, regarding the two component mounting ranges 360a and 360d defined for the two signal conductor patterns 330a and 330d, the distances between the signal conductor pattern 330 and the two ground conductor patterns 340 are formed asymmetrically, but the present invention is not limited thereto. Furthermore, a plurality of component mounting portions 350 and component mounting ranges 360 may be provided on one signal conductor pattern 330, and a plurality of component mounting portions 350 and component mounting ranges 360 may be provided on one signal conductor pattern 330. Figure 3 Thus, the component mounting portions 350 and the component mounting ranges 360 are provided on the four signal conductor patterns, respectively. Therefore, the separation distances can be configured asymmetrically in at least one component mounting range 360 ​​of at least one signal conductor pattern 330 according to the occurrence of leakage microwaves on the relay substrate 118 .

[0135] In addition, the reason why the part mounting range 360 ​​is set as "a top-view square range with the extension direction of the signal conductor pattern 330 in the part mounting portion 350 as the direction of one side and the distance from the center of the part mounting portion 350 to the portion on the signal conductor pattern 330 closest to the center as the length of one side" as mentioned above is because: since the effective electric field distribution of microwaves is within this range, by setting the electrode structure in this part to be asymmetric, the effective electric field distribution of microwaves can be effectively affected, and as a result, the direction of the leakage microwave can be effectively adjusted.

[0136] Next, a modification of the relay substrate used for the optical modulator 100 will be described.

[0137] <First Modification>

[0138] Figure 5 is a diagram showing the structure of a relay substrate 518 according to a first modification example, which is equivalent to Figure 3 The relay substrate 518 can be Figure 1 In the optical modulator 100 shown in the figure, it is used instead of the relay substrate 118. Figure 5 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.

[0139] The relay substrate 518 has the same structure as the relay substrate 118, but in the part mounting range 360b, 360c of the part mounting parts 350b, 350c of the signal conductor patterns 330b and 330c, the two ground conductor patterns sandwiching the signal conductor patterns 330b and 330c are also asymmetrically constructed with respect to a straight line extending along the extension direction of the signal conductor patterns 330b and 330c in the part mounting parts 350b, 350c.

[0140] Here, the component mounting range 360b is defined as a range of a square in plan view, similarly to the component mounting range 360a, wherein the direction of extension of the signal conductor pattern 330b in the component mounting portion 350b is a direction of one side, and the distance (pitch) w13 from the center of the component mounting portion 350b to the portion of the signal conductor pattern 330a that is closest to the center (for example, the center of the width direction of the signal conductor pattern 330a in the portion) is a length of one side. In addition, in the present embodiment, the signal conductor pattern 330 is formed in a straight line parallel to the side edge 318d, so the length w13 of one side of the component mounting range 360b is equal to the distance (pitch) w21 between the center line of the width direction of the signal conductor pattern 330b and the center line of the width direction of the signal conductor pattern 330a. That is, w13=w21.

[0141] Moreover, the component mounting range 360c is defined as a range of a square in plan view, similarly to the component mounting range 360d, in which the extending direction of the signal conductor pattern 330c in the component mounting portion 350c is a direction of one side, and the distance (pitch) w14 from the center of the component mounting portion 350c to the portion on the signal conductor pattern 330d that is closest to the center (for example, the center in the width direction of the signal conductor pattern 330d in the portion) is a length of one side. In addition, in the present embodiment, the signal conductor pattern 330 is formed parallel to the side edge 318d and in a straight line, so the length w14 of one side of the component mounting range 360c is equal to the distance (pitch) w22 between the center line in the width direction of the signal conductor pattern 330c and the center line in the width direction of the signal conductor pattern 330d. That is, w14=w22.

[0142] More specifically, the relay substrate 518 has the same structure as the relay substrate 118, but the difference is that the ground conductor patterns 340c and 340d are replaced with ground conductor patterns 540c and 540d. The ground conductor pattern 540c has the same structure as the ground conductor pattern 340c, but the difference is that it has a notch 342b (shaded portion in the figure) in the component mounting range 360b. Therefore, the ground conductor patterns 340b and 540c are formed so that the spacing distance (gap) from the edge of each of the ground conductor patterns 340b and 540c to the facing edge of the signal conductor pattern 330b has different parts in the component mounting range 360b.

[0143] Therefore, similarly to the component mounting portion 350a, the leakage microwave generated from the component mounting portion 350b is directed toward the ground conductor pattern 540c where the high-frequency signal is less enclosed due to the presence of the notch portion 342b, for example. Figure 5 In the direction range sandwiched by the arrows of the two dotted chain lines extending from the component mounting portion 350b, the intensity is greater than in other directions. As a result, the crosstalk from the signal conductor pattern 330b to the signal conductor pattern 330a caused by the leakage microwave generated from the component mounting portion 350b is reduced.

[0144] Therefore, in the relay substrate 518 , crosstalk between the signal conductor patterns 330 a and 330 b that propagate one of the two high-frequency electrical signals forming a pair is effectively suppressed.

[0145] Similarly, the ground conductor pattern 540d has the same structure as the ground conductor pattern 340d, but is different in that it has a notch 342c (shaded portion in the figure) in the component mounting range 360c. Thus, the ground conductor patterns 540d and 340e are formed so that the spacing distance (gap) from the edges of the ground conductor patterns 540d and 340e to the facing edges of the signal conductor pattern 330c has different portions in the component mounting range 360c.

[0146] As a result, the leakage microwave generated from the component mounting portion 350c is transmitted in the direction of the ground conductor pattern 540d where the high-frequency signal is less enclosed due to the presence of the notch portion 342c, for example, Figure 5 The intensity is greater in the direction range between the two dot chain arrows extending from the component mounting portion 350c than in other directions. As a result, the crosstalk from the signal conductor pattern 330c to the signal conductor pattern 330d caused by the leakage microwave generated from the component mounting portion 350c is reduced.

[0147] Therefore, in the relay substrate 518, crosstalk between the signal conductor patterns 330c and 330d that propagate the other pair of two high-frequency electrical signals is also effectively suppressed.

[0148] As a result, in the relay substrate 518 , better light modulation characteristics can be achieved than in the case of using the relay substrate 118 .

[0149] In addition, in the first embodiment and the first variant, the signal conductor pattern 330 is formed in a straight line, but is not limited thereto. In other variants and embodiments shown below, the signal conductor pattern 330 can also be formed in any shape including a curve or bend according to the required electrical characteristics, the configuration of the signal input terminal 124 and / or the configuration of the signal electrode 112 of the optical modulation element 102, etc.

[0150] Here, in an optical modulator having an optical modulation element using an LN substrate, the relay substrate typically has an outer dimension of, for example, several mm×tens of mm. In a relay substrate of this size, the length of one side of a square component mounting range 360 ​​in a plan view is, for example, about several hundred μm, and within the component mounting range, the signal conductor pattern 330 can generally be regarded as a straight line.

[0151] <Second Modification>

[0152] Figure 6 is a diagram showing the structure of a relay substrate 718 according to a second modification example, which is equivalent to Figure 3 The 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 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.

[0153] The relay substrate 718 has signal conductor patterns 330 formed at the same positions as the relay substrate 118, and each of these signal conductor patterns 330 has a component mounting portion 350, similarly to the relay substrate 118. Therefore, in the relay substrate 718, component mounting ranges 360a and 360d are defined for each component mounting portion 350 of the signal conductor pattern 330, similarly to the relay substrate 118.

[0154] The relay substrate 718 has the same structure as the relay substrate 118, but is different in that it includes ground conductor patterns 740a and 740f instead of the ground conductor patterns 340a and 340f. The ground conductor pattern 740a has the same Figure 3 The illustrated ground conductor pattern 340a has the same structure as the ground conductor pattern 340a of the relay substrate 118, but differs from the ground conductor pattern 340a in that a blocked section 742a (ie, a section without a conductor) is provided in the component mounting range 360a.

[0155] Therefore, in the relay substrate 718, the high-frequency signal confinement effect of the signal conductor pattern 330a on the ground conductor pattern 740a side in the component mounting range 360a becomes weaker than when the ground conductor pattern 340a is used. Figure 3 As a result, in the relay substrate 718, the crosstalk caused by the leakage microwave from the signal conductor pattern 330a to 330b is further reduced than in the relay substrate 118.

[0156] Similarly, the ground conductor pattern 740f has Figure 3 The structure of the relay substrate 118 shown in FIG. 1 is similar to that of the ground conductor pattern 340f, but the difference from the ground conductor pattern 340f is that the leakage microwave generated in the component mounting range 360d is blocked by a section 742d. Figure 3 As a result, in the relay substrate 718, the crosstalk caused by the leakage microwave from the signal conductor pattern 330d to 330c is further reduced than in the relay substrate 118.

[0157] Especially, like Figure 6 The structure of providing the interrupted sections 742a and 742d in the ground conductor patterns 740a and 740f is similar to Figure 3 Compared with the structure with the notches 342a and 342d shown in the figure, the grounding strength of the ground conductor patterns 740a and 740f can be greatly weakened relative to the ground conductor patterns 340b and 340e (that is, the impedance of the ground conductor patterns 740a and 740f to the ground line can be made higher than the impedance of the ground conductor patterns 340b and 340e to the ground line). Therefore, the relay substrate 718 of this modified example is an effective structure when it is desired to bias the propagation direction of the leakage microwave generated from the component mounting portion 350 while shortening the length of the asymmetric portion of the two ground conductor patterns 340 in the component mounting range 360 ​​as much as possible.

[0158] <Third Modification>

[0159] Figure 7 is a diagram showing the structure of a relay substrate 818 according to a third modification example, which is equivalent to Figure 3 The relay substrate 818 may be provided in the 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 , Figure 5 , Figure 6 The same components as those of the relay substrates 118, 518, and 718 are used. Figure 3 , Figure 5 , Figure 6 The same symbols are used to represent and refer to the Figure 3 , Figure 5 , Figure 6 Description.

[0160] The relay substrate 818 has Figure 5 The relay substrate 518 of the first modified example shown in FIG. 1 has the same structure as that of the relay substrate 518, but includes a ground conductor pattern 340a, 340f instead of the ground conductor pattern 340a, 340f. Figure 6 The relay substrate 718 of the second modification shown includes ground conductor patterns 840c and 840d in place of the ground conductor patterns 540c and 540d, similarly to the ground conductor patterns 740a and 740f.

[0161] The ground conductor patterns 840c and 840d have Figure 5 The illustrated relay substrate 518 has the same structure as the ground conductor patterns 540c and 540d, but differs from the ground conductor patterns 540c and 540d in that they have blocked sections 842b and 842c in the component mounting ranges 360b and 360c, respectively.

[0162] The relay substrate 818 having the above structure includes the ground conductor patterns 740a and 740f, and thus Figure 6 The relay substrate 718 of the second modified example shown in FIG. Figure 3 Compared to the illustrated relay substrate 118 , the crosstalk from the signal conductor pattern 330 a toward 330 b and the crosstalk from the signal conductor pattern 330 d toward 330 c are further reduced.

[0163] Furthermore, the relay substrate 818 has sections 842b and 842c where no conductor is formed in the ground conductor patterns 840c and 840d, respectively. Therefore, the leakage microwaves generated in the component mounting ranges 360b and 360c are Figure 5 As a result, in the relay substrate 818, compared with the relay substrate 518, the crosstalk caused by the leakage microwave from the signal conductor pattern 330b toward 330a and from 330c toward 330d is further reduced.

[0164] <Fourth Modification>

[0165] Figure 8 is a diagram showing the structure of a relay substrate 918 according to a fourth modification example, which is equivalent to Figure 3 The relay substrate 918 is a partial detailed view of the first embodiment shown in FIG. Figure 7 The relay substrate 818 of the third modified example shown in the figure can also be 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 , Figure 7 The same components as those of the relay substrates 118 and 818 are used. Figure 3 , Figure 7 The same symbols are used to represent and refer to the Figure 3 , Figure 7 Description.

[0166] The relay substrate 918 has Figure 7 The third modified example shown in FIG. 8 has the same structure as the relay substrate 818, and similarly to the relay substrate 818, Figure 5 Compared with the relay substrate 518 of the first modified example shown, the crosstalk caused by the leakage microwave between the signal conductor patterns 330a-330b and between 330c-330d is further reduced.

[0167] As described above, the relay substrate 918 has Figure 7 The third modification example shown in FIG. 8 has the same structure as the relay substrate 818, but is different from the Figure 7 The relay substrate 818 of the third modified example shown in FIG. 1 is different in that it includes ground conductor patterns 940b and 940e instead of the ground conductor patterns 340b and 340e. The ground conductor pattern 940b has the same Figure 7 The third variant example shown has the same structure as the ground conductor pattern 340b of the relay substrate 818, but differs in that recesses 942a and 942b are provided on the edges facing the component mounting portions 350a and 350b, respectively, within the component mounting ranges 360a and 360b.

[0168] That is, in the relay substrate 918, another ground conductor pattern 940b facing one of the ground conductor patterns 740a having a section 742a without a conductor has a recess 942a, and the recess 942a is formed so that the separation distance to the portion of the signal conductor pattern 330a constituting the part mounting portion 350a is longer than the separation distance to other portions of the signal conductor pattern 330a within the corresponding part mounting range 360a.

[0169] Generally, in the component mounting portion 350a, when an electric circuit element is mounted on the signal conductor pattern 330a, the mounting position of the electric circuit element may vary due to manufacturing variations. Figure 7 In the illustrated relay substrate 818 , if such a mounting position shift occurs toward the ground conductor pattern 340 b that is spaced from the signal conductor pattern 330 a by a smaller distance than the ground conductor pattern 740 a , the characteristic impedance of the signal conductor pattern 330 a may change.

[0170] In the relay substrate 918, a grounding conductor pattern 940b having a recess 942a is included instead of the grounding conductor pattern 340b. Therefore, even if the installation position of the electrical circuit element in the component mounting portion 350a deviates toward the grounding conductor pattern 940b, the ratio of the deviation of the installation position to the separation distance between the component mounting portion 350a and the grounding conductor pattern 940b is smaller than that of the relay substrate 818 without the recess 942a.

[0171] Therefore, in the relay substrate 918 , the change in the characteristic impedance of the signal conductor pattern 330 a due to the deviation of the mounting position within the component mounting range 360 ​​a can be made milder (smaller) than in the relay substrate 818 .

[0172] Similarly, in the relay substrate 918, the other ground conductor pattern 940b facing one of the ground conductor patterns 840c having the section 842b without a conductor has a recess 942b, and the recess 942b is formed so that the distance between the portion of the signal conductor pattern 330b constituting the component mounting portion 350b is longer than the distance between the portion of the signal conductor pattern 330b in the corresponding component mounting range 360b. Therefore, in the relay substrate 918, the change in the characteristic impedance of the signal conductor pattern 330b caused by the deviation of the mounting position of the electrical circuit element in the component mounting portion 350b can be made milder (smaller) than in the relay substrate 818.

[0173] Similarly, the ground conductor pattern 940e of the relay substrate 918 has Figure 7 The ground conductor pattern 340e of the relay substrate 818 of the third variant shown has the same structure, but differs in that recesses 942c and 942d are provided on the edges facing the signal conductor patterns 330c and 330d within the component mounting ranges 360c and 360d, respectively.

[0174] That is, in the relay substrate 918, the other ground conductor pattern 940e facing one of the ground conductor patterns 840d having the section 842c without a conductor has a recess 942c formed so that the distance between the portion of the signal conductor pattern 330c constituting the component mounting portion 350c is longer than the distance between the portion of the signal conductor pattern 330c in the corresponding component mounting range 360c. Furthermore, in the relay substrate 918, the other ground conductor pattern 940e facing one of the ground conductor patterns 740f having the section 742d without a conductor has a recess 942d formed so that the distance between the portion of the signal conductor pattern 330d constituting the component mounting portion 350d is longer than the distance between the portion of the signal conductor pattern 330d in the corresponding component mounting range 360d.

[0175] Thus, in the relay substrate 918, within the component mounting range 360c, 360d, the change in the characteristic impedance of the signal conductor patterns 330c, 330d caused by the deviation of the mounting position of the electrical circuit elements in the component mounting portions 350c, 350d can be mitigated (smaller) than that of the relay substrate 818.

[0176] in addition, Figure 8 In the embodiment, the recesses 942a, 942b, 942c, and 942d (hereinafter collectively referred to as the recesses 942) are formed to be longer than the length of the component mounting portion 350 along the extension direction of the corresponding signal conductor pattern 330, but the present invention is not limited thereto. The recesses 942 may also be formed to be shorter than the length of the component mounting portion 350 along the extension direction of the corresponding signal conductor pattern 330.

[0177] <Fifth Modification>

[0178] Fig. 9 is a diagram showing the structure of a relay substrate 1018 according to a fifth modification example, which is equivalent to Figure 3 The relay substrate 1018 may be Figure 3 In the optical modulator 100 shown in the figure, it is used instead of the relay substrate 118. Fig. 9 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.

[0179] The relay substrate 1018 is connected to Figure 3The signal conductor pattern 330 is formed at the same position as the relay substrate 118 of the first embodiment shown, and each signal conductor pattern 330 is provided with a component mounting portion 350 similar to the relay substrate 118. Therefore, in the relay substrate 1018, for each component mounting portion 350, a component mounting range 360 ​​similar to that of the relay substrate 118 is defined.

[0180] The first embodiment and the first to fourth modifications described above, Figure 3 , Figure 5 , Figure 6 , Figure 7 In the illustrated relay substrates 118, 518, 818, and 918, the two ground conductor patterns 1040 sandwiching the signal conductor pattern 330 within the component mounting range 360 ​​are configured to have mutually asymmetric contour shapes. In contrast, in the relay substrate 1018 of the present modified example, the diameters and numbers of through holes provided in the two ground conductor patterns sandwiching the signal conductor pattern 330 within the component mounting range 360 ​​are different, and thus the through holes are configured to be mutually asymmetric in terms of the formation form.

[0181] Specifically, the relay substrate 1018 of this variation has Figure 3 The structure is the same as the relay substrate 118 shown in the figure, but the difference from the relay substrate 118 is that the grounding conductor patterns 340a, 340b, 340c, 340d, 340e, and 340f are replaced by grounding conductor patterns 1040a, 1040b, 1040c, 1040d, 1040e, and 1040f (also collectively referred to as grounding conductor patterns 1040).

[0182] The ground conductor patterns 1040a, 1040b, 1040c, 1040d, 1040e, and 1040f have the same structures as the ground conductor patterns 340a, 340b, 340c, 340d, 340e, and 340f, respectively.

[0183] However, the ground conductor patterns 1040a and 1040f are Figure 3 The ground conductor patterns 340a and 340f of the illustrated relay substrate 118 are different and do not have the cutouts 342a and 342d. Moreover, the ground conductor patterns 1040a, 1040b, 1040c, 1040d, 1040e, and 1040f each have a plurality of through holes 1070 having the same diameter as each other, for example. Fig. 9 In order to avoid redundant description, for each ground conductor pattern 1040 , only one through hole is labeled with the symbol 1070 , but it should be understood that other circles having the same diameter as the circle labeled with the symbol 1070 are also through holes 1070 .

[0184] Furthermore, in particular, in the relay substrate 1018, the two ground conductor patterns 1040 sandwiching the signal conductor pattern 330 are configured so that the diameters and numbers of through holes provided in these ground conductor patterns are different from each other within the component mounting range 360. Specifically, within the component mounting range 360a, six through holes 1070 are provided in the ground conductor pattern 1040b, whereas four through holes 1070 and one through hole 1072 having a smaller diameter than the through hole 1070 are provided in the ground conductor pattern 1040a.

[0185] Generally speaking, in a high-frequency signal line including a signal conductor and a ground conductor, the lower the impedance from the ground conductor to the ground line (that is, the more sufficient the so-called ground reinforcement), the stronger the confinement of the high-frequency signal in the signal conductor.

[0186] In the component mounting range 360a of the relay substrate 1018, through holes are provided in the ground conductor patterns 1040a and 1040b in the above-described structure, so that the impedance of the ground conductor pattern 1040a with respect to the back ground conductor (not shown) constituting the ground line provided on the back surface of the relay substrate 1018 is higher than the impedance of the ground conductor pattern 1040b with respect to the back ground conductor. That is, in the component mounting range 360a, the high frequency confinement effect in the signal conductor pattern 330a is lower on the ground conductor pattern 1040a side than on the ground conductor pattern 1040b side.

[0187] Therefore, the leakage microwave generated in the component mounting portion 350a is biased toward the ground conductor pattern 1040a (for example, Fig. 9 The propagation is carried out in a manner having a greater intensity than in other directions) within the direction range sandwiched by the arrows of the two dot chain lines extending from the component mounting portion 350a.

[0188] As a result, the intensity of the leakage microwave in the direction range other than the direction range sandwiched by the dot-chain arrow is relatively reduced, and the crosstalk from the signal conductor pattern 330a to 330b caused by the leakage microwave generated from the component mounting portion 350a is reduced.

[0189] Similarly, within the component mounting range 360b of the relay substrate 1018, six through holes 1070 are provided in the ground conductor pattern 1040b, whereas four through holes 1070 and one through hole 1072 having a smaller diameter than the through hole 1070 are provided in the ground conductor pattern 1040c. Therefore, as described above, the impedance of the ground conductor pattern 1040c with respect to the back ground conductor is higher than the impedance of the ground conductor pattern 1040b with respect to the back ground conductor, and crosstalk from the signal conductor pattern 330b to 330a due to leakage microwaves generated from the component mounting portion 350b is reduced.

[0190] The same is true for the component mounting ranges 360c and 360d. That is, within the component mounting ranges 360c and 360d, six through holes 1070 are provided at corresponding portions on the ground conductor pattern 1040d, respectively, whereas four through holes 1070 and one through hole 1072 having a smaller diameter than the through hole 1070 are provided in the ground conductor patterns 1040d and 1040f.

[0191] Therefore, the leakage microwaves generated in the component mounting portions 350c and 350d are deflected toward the ground conductor patterns 1040d and 1040f, respectively. As a result, the crosstalk caused by the leakage microwaves from the signal conductor pattern 330c toward 330d, from the signal conductor pattern 330d toward 330c, and from the signal conductor pattern 330d toward 330c is reduced.

[0192] In addition, in this modification, the following case is described, that is, the diameter and number of through holes in the two ground conductor patterns sandwiching the signal conductor pattern are different from each other, but the present invention is not limited to this. For example, the diameter of the through hole may be the same in the two ground conductor patterns and only the number may be different from each other, or the number of through holes may be the same in the two ground conductor patterns but the diameter of at least some of the through holes may be different from the diameter of the other through holes.

[0193] <Sixth Modification>

[0194] Fig.10 is a diagram showing the structure of a relay substrate 1118 according to a sixth modification example, which is equivalent to Figure 3 The relay substrate 1118 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 , Fig. 9 The same components as those of the relay substrates 118 and 1080 are used. Figure 3 , Fig. 9 The same symbols are used to represent and refer to the Figure 3 , Fig. 9 Description.

[0195] In the relay substrate 1118, different numbers of through holes are provided in the two ground conductor patterns sandwiching the signal conductor pattern 330 within the component mounting range 360. Furthermore, the two ground conductor patterns are formed so as to include portions having different widths measured in a direction orthogonal to the extending direction of the signal conductor pattern 330 within the component mounting range 360.

[0196] Specifically, the relay substrate 1118 has Fig. 9 The relay substrate 1018 of the fifth modification shown has the same structure, but is different in that it includes ground conductor patterns 1140a, 1140c, 1140d, and 1140f instead of the ground conductor patterns 1040a, 1040c, 1040d, and 1040f.

[0197] The ground conductor pattern 1140a has Fig. 9 The relay substrate 1018 of the fifth modified example shown has the same structure as the ground conductor pattern 1040a, but includes a through hole 1070 in place of the through hole 1072 instead of the through hole 1072. That is, the relay substrate 1118 has different numbers of through holes 1070 having the same diameter in the ground conductor patterns 1140a and 1040b within the component mounting range 360a.

[0198] Furthermore, the ground conductor pattern 1140a has a narrow width portion 1174a (shaded portion in the figure) within the component mounting range 360a. The narrow width portion 1174a is formed so that the width measured in the direction perpendicular to the extending direction of the signal conductor pattern 330a is shorter than the width direction length of the portion of the ground conductor pattern 1040b extending within the component mounting range 360a.

[0199] Thus, in the relay substrate 1118, within the component mounting range 360a, the ground conductor pattern 1140a includes the narrow width portion 1174a as a portion having a higher impedance with respect to the ground line (eg, back surface ground conductor) than the ground conductor pattern 1040b.

[0200] Therefore, in the component mounting range 360a, the effect of confining the high-frequency signal in the signal conductor pattern 330a decreases on the ground conductor pattern 1140a side having the narrow width portion 1174a than on the ground conductor pattern 1040b side.

[0201] Therefore, the leakage microwave generated in the component mounting portion 350a is biased in the direction of the ground conductor pattern 1140a (for example, Fig.10 In the direction range sandwiched by the arrows of the two dot chain lines extending from the part mounting portion 350a), it is released in a manner having greater strength than in other directions.

[0202] As a result, the intensity of the leakage microwave in the direction range other than the direction range sandwiched by the dot-dash line arrows is relatively reduced, and the crosstalk caused by the leakage microwave from the signal conductor pattern 330a to 330b is reduced.

[0203] Similarly, the ground conductor pattern 1140c has a narrow width portion 1174b (shaded portion in the figure) within the component mounting range 360b. The narrow width portion 1174b is formed so that the width measured in the direction perpendicular to the extending direction of the signal conductor pattern 330b is shorter than the width direction length of the portion of the ground conductor pattern 1040b extending into the component mounting range 360b.

[0204] Therefore, the leakage microwave generated in the component mounting portion 350b is deflected and emitted in the direction of the ground conductor pattern 1140c, and the crosstalk caused by the leakage microwave from the signal conductor pattern 330b to 330a is reduced.

[0205] Similarly, in the relay substrate 1118, the ground conductor patterns 1140d and 1140f have different numbers of through holes 1070 from the ground conductor pattern 1040e in the respective component mounting ranges 360c and 360d. In the relay substrate 1118, the ground conductor patterns 1140d and 1140f have narrow width portions 1174c and 1174d in the component mounting ranges 360c and 360d, respectively. The narrow width portions 1174c and 1174d are formed so that the width measured in the direction orthogonal to the extending direction of the signal conductor patterns 330c and 330d is shorter than the width direction length of the portion of the ground conductor pattern 1040c extending into the component mounting ranges 360c and 360d, respectively.

[0206] Therefore, the leakage microwaves generated in the component mounting portions 350c and 350d propagate in the directions of the ground conductor patterns 1140d and 1140f, respectively. As a result, the crosstalk caused by the leakage microwaves from the signal conductor pattern 330b toward 330a, from 330c toward 330d, and from 330d toward 330c is reduced.

[0207] in addition, Fig.10 In the illustrated relay substrate 1118 , the narrow width portion 1174 a and the like are formed to be wider than the diameter of the through hole 1070 , but the present invention is not limited thereto. The narrow width portion 1174 a and the like may be formed to be narrower than the diameter of the through hole 1070 .

[0208] <Seventh Modification>

[0209] Fig.11 is a diagram showing the structure of a relay substrate 1218 according to a seventh modification example, which is equivalent to Figure 3 The relay substrate 1218 and the Fig.10 Similarly, the relay substrate 1118 of the sixth variation shown in FIG. Figure 1 In the optical modulator 100 shown in the figure, it is used instead of the relay substrate 118. Fig.11 In Fig.10 The same components as those of the relay substrate 1118 shown in FIG. Fig.10 The same symbols are used to represent and refer to the Fig.10 Description.

[0210] The relay substrate 1218 has Fig.10 The relay substrate 1118 of the sixth variant shown has the same structure, but is different in that it includes ground conductor patterns 1240a, 1240b, 1240c, 1240d, 1240e, and 1240f instead of the ground conductor patterns 1140a, 1040b, 1040c, 1140d, 1140e, and 1040f.

[0211] The ground conductor patterns 1240a, 1240c, 1240d, and 1240f have Fig.10 The ground conductor patterns 1140a, 1140c, 1140d, and 1140f of the relay substrate 1118 of the sixth variation shown in the figure have the same structure, but the difference is that they include narrow width portions 1274a, 1274b, 1274c, and 1274d in the component mounting ranges 360a, 360b, 360c, and 360d, respectively. Fig.10 The narrow width portions 1174 a , 1174 b , 1174 c , and 1174 d of the sixth modification shown in the figure similarly have a width narrower than the diameter of the through hole 1070 .

[0212] That is, the narrow width portions 1274a and 1274b are formed so that the width measured in the direction perpendicular to the extending direction of the signal conductor patterns 330a and 330b is shorter than the width direction length of the ground conductor pattern 1240b extending into the component mounting ranges 360a and 360b, respectively, and is narrower than the diameter of the through hole 1070. Furthermore, the narrow width portions 1274c and 1274d are formed so that the width measured in the direction perpendicular to the extending direction of the signal conductor patterns 330c and 330d is shorter than the width direction length of the ground conductor pattern 1240e extending into the component mounting ranges 360c and 360d, respectively, and is narrower than the diameter of the through hole 1070.

[0213] Therefore, the ground conductor patterns 1240a, 1240c, 1240d, and 1240f have an impedance ratio with the ground line. Fig.10The narrow width portions 1174a, 1174b, 1174c, 1174d of the relay substrate 1118 of the sixth variant shown are higher than the narrow width portions 1274a, 1274b, 1274c, 1274d, and the crosstalk caused by leakage microwaves between the signal conductor patterns 330a and 330b, and between 330c and 330d is reduced.

[0214] Furthermore, the ground conductor patterns 1240b and 1240e of the relay substrate 1218 have Fig.10 The ground conductor patterns 1040b and 1040e of the relay substrate 1118 of the sixth modification shown in FIG. Fig.10 The relay substrate 1118 of the sixth variation shown in FIG. 1 is different in that the parts mounting ranges 360a, 360b, 360c, and 360d include the parts mounted on the relay substrate 1118. Figure 8 The recessed portions 942a, 942b, 942c, and 942d of the interconnect substrate 914 of the fourth modification shown are similar to the recessed portions 1276a, 1276b, 1276c, and 1276d (hereinafter, also collectively referred to as the recessed portions 1276).

[0215] That is, in the relay substrate 1218, the ground conductor pattern 1240b has recesses 1276a and 1276b, and the recesses 1276a and 1276b are formed so that the distances between the signal conductor patterns 330a and 330b constituting the component mounting portions 350a and 350b are longer than the distances between the signal conductor patterns 330a and 330b in the corresponding component mounting ranges 360a and 360b. Furthermore, the ground conductor pattern 1240e has recesses 1276d and 1276d, and the recesses 1276d and 1276d are formed so that the distances between the signal conductor patterns 330c and 330d constituting the component mounting portions 350c and 350d are longer than the distances between the signal conductor patterns 330c and 330d in the corresponding component mounting ranges 360c and 360d.

[0216] As a result, in the relay substrate 1218, Figure 8 Similarly, in the relay substrate 914 of the fourth variant shown, when the electrical circuit elements constituting the part mounting portions 350a, 350b, 350c, 350d are mounted on the signal conductor patterns 330a, 330b, 330c, 330d, even if the mounting position of the electrical circuit elements deviates toward the adjacent ground conductor patterns 1240b, 1240e, the change in the characteristic impedance of the signal conductor patterns 330a, 330b, 330c, 330d caused by the deviation of the mounting position can be mitigated compared to the relay substrate 1118.

[0217] in addition, Fig.10 as well as Fig.11 In the embodiment, through holes are provided in the narrow width parts 1174a, 1274, etc., but the present invention is not limited thereto. The structure in which through holes are not provided in the narrow width parts 1174a, 1274, etc. can also achieve the same effect as described above.

[0218] Furthermore, the relay substrate 1218 and Fig.10 In the relay substrate 1118 of the seventh variation shown, within the component mounting range 360, the two ground conductor patterns are formed to include the following parts, the parts have different numbers of through holes, and the widths measured in the direction orthogonal to the extension direction of the signal conductor pattern 330 are different from each other, but the present invention is not limited to this. For example, within the component mounting range 360, the two ground conductor patterns are formed to include parts with different widths measured in the direction orthogonal to the extension direction of the signal conductor pattern 330, but they may have the same number of through holes or no through holes at all. With such a configuration, the impedances of the two ground conductor patterns and the ground line can also be made different from each other, thereby achieving the same effect as the above effect.

[0219] <Eighth Modification>

[0220] Fig.12 is a diagram showing the structure of a relay substrate 1318 according to an eighth modification example, which is equivalent to Figure 3 The relay substrate 1318 may be Figure 1 In the optical modulator 100 shown in the figure, it is used instead of the relay substrate 118. Fig.12 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.

[0221] The relay substrate 1318 has Figure 3 The relay substrate 118 shown has the same structure as that shown, but is different in that it includes ground conductor patterns 1340a, 1340b, 1340c, 1340d, 1340e, and 1340f instead of the ground conductor patterns 340a, 340b, 340c, 340d, 340e, and 340f.

[0222] The ground conductor patterns 1340a and 1340f have Figure 3The ground conductor patterns 340a and 340f of the relay substrate 118 shown in the figure have the same structure, but the difference is that they do not include the notch portions 342a and 342d. In addition, in this modification, the ground conductor patterns 1340a, 1340c, 1340d, and 1340f do not have through holes in the component mounting ranges 360a, 360b, 360c, and 360d. However, these ground conductor patterns 1340a, 1340c, 1340d, and 1340f may also have through holes (not shown) outside the component mounting ranges 360a, 360b, 360c, and 360d.

[0223] The ground conductor patterns 1340b and 1340e each have two through holes 1370 in the component mounting ranges 360a, 360b, 360c, and 360d. Here, the ground conductor patterns 1340b and 1340e may each have through holes (not shown) outside the component mounting ranges 360a, 360b, 360c, and 360d.

[0224] That is, in the relay substrate 1318, within the component mounting ranges 360a, 360b, 360c, and 360d, the through holes 1370 are respectively present only in the ground conductor patterns 1340b and 1340e, and no through holes are present in the ground conductor patterns 1340a, 1340c, 1340d, and 1340f.

[0225] As a result, in the relay substrate 1318, in the component mounting ranges 360a, 360b, 360c, and 360d, the impedance between the ground conductor patterns 1340b and 1340e and the ground line is lower than that of the ground conductor patterns 1340a, 1340c, 1340d, and 1340f.

[0226] Therefore, in the relay substrate 1318, within the component mounting ranges 360a, 360b, 360c, and 360d, the sealing effect of the high-frequency signals in the signal conductor patterns 330a, 330b, 330c, and 330d is relatively reduced on the ground conductor patterns 1340a, 1340c, 1340d, and 1340f sides compared to the ground conductor patterns 1340b and 1340e sides, respectively.

[0227] As a result, the leakage microwaves generated in the component mounting portions 350a, 350b, 350c, and 350d are deflected and emitted in the directions of the ground conductor patterns 1340a, 1340c, 1340d, and 1340f, respectively.

[0228] Therefore, the crosstalk between the signal conductor patterns 330a and 330b and between 330c and 330d due to the leaked microwaves is reduced.

[0229] <Ninth Modification>

[0230] Fig.13 is a diagram showing the structure of a relay substrate 1418 according to a ninth modification example, which is equivalent to Figure 3 The relay substrate 1418 and Figure 5 , Fig.12 The relay substrates 518 and 1318 of the first and eighth modified examples shown in the figure can be similarly Figure 1 In the optical modulator 100 shown in the figure, it is used instead of the relay substrate 118. Fig.13 In Figure 3 , Figure 5 , Fig.12 The same components as those of the relay substrates 118, 518, and 1318 are used. Figure 3 , Figure 5 , Fig.12 The same symbols are used to represent and refer to the Figure 3 , Figure 5 , Fig.12 Description.

[0231] The relay substrate 1318 has Figure 3 The relay substrate 118 shown in FIG. 1 has the same structure, but includes a ground conductor pattern 340b, 340e instead of the ground conductor pattern 340b, 340e. Fig.12 The relay substrate 1318 of the eighth modification example shown in FIG. 1 includes ground conductor patterns 1340b and 1340e in place of the ground conductor patterns 340c and 340d. Figure 5 The ground conductor patterns 540c and 540d of the relay substrate 518 according to the first modification example are shown.

[0232] Thus, in the relay substrate 1418, Fig.12 Similarly, in the relay substrate 1318 shown in FIG. 1 , only one of the ground conductor patterns is provided with a through hole 1370 within the component mounting range 360, thereby having the effect of reducing crosstalk between the signal conductor patterns 330. Figure 5 The notches 342a, 342b, 342c, and 342d in the relay substrate 518 shown in FIG. Fig.12 The relay substrate 1318 shown has a higher crosstalk reduction effect.

[0233] [Second embodiment]

[0234] This embodiment is an optical transmission device equipped with the optical modulator 100 of the first embodiment and any of the optical modulators 100 using relay substrates 518, 718, 818, 918, 1018, 1118, 1218, 1318, and 1418 of the modified examples thereof.

[0235] Fig.14 2100 is a diagram showing the structure of an optical transmission device according to the present embodiment. The optical transmission device 2100 includes an optical modulator 2102 , a light source 2104 for causing light to enter the optical modulator 2102 , a modulation signal generator 2106 , and a modulation data generator 2108 .

[0236] The optical modulator 2102 may be any one of the optical modulator 100 of the first embodiment and the optical modulator 100 using the relay substrates 518, 718, 818, 918, 1018, 1118, 1218, 1318, and 1418 of the modified examples thereof. Here, in order to avoid redundant description and facilitate understanding, the optical modulator 2102 is hereinafter referred to as the optical modulator 100 of the first embodiment.

[0237] 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.

[0238] The modulation signal generating unit 2106 is an electronic circuit (driving circuit) that outputs an electrical signal for causing the optical modulator 2102 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 2102 to perform an optical modulation operation according to the modulation data, and is input to the optical modulator 2102. 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 2102. Here, the high-frequency electrical signals input to the signal electrodes 112a and 112b constitute one pair, and modulate the output light output from one output optical waveguide 126a of the optical modulation element 102. In addition, the high-frequency electrical signals input to the signal electrodes 112c and 112d constitute another pair, and modulate the output light output from the other output optical waveguide 126b of the optical modulation element 102.

[0239] 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 2102 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.

[0240] As a result, the light output from the light source 2104 is modulated by, for example, DP-QPSK by the optical modulator 2102 , becomes modulated light, and is output from the optical transmission device 2100 .

[0241] In particular, in the optical transmitter 2100, any of the optical modulators 100 of the first embodiment and the optical modulators 100 using the relay substrates 518, 718, 818, 918, 1018, 1118, 1218, 1318, and 1418 of the modified examples thereof is used as the optical modulator 2102. Therefore, in the optical transmitter 2100, the increase in crosstalk between high-frequency electrical signals driving the optical modulator element 102 caused by the spatial leakage microwaves can be effectively reduced, especially the crosstalk caused by the spatial leakage microwaves between the signal lines that propagate the paired two high-frequency electrical signals. Therefore, in the optical transmitter 2100, stable and good optical modulation characteristics can be ensured, thereby realizing stable and good transmission characteristics.

[0242] 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.

[0243] For example, in the relay substrates 118, 518, 718, 818, 918, 1018, 1118, 1218, 1318, and 1418, the two ground conductor patterns 340 include portions that are formed asymmetrically with respect to the component mounting range 360 ​​of two or more signal conductor patterns 330, but the present invention is not limited thereto. In any of the structures of the relay substrates 118, 518, 718, 818, 918, 1018, 1118, 1218, 1318, and 1418, the two ground conductor patterns 340 may include portions that are formed asymmetrically with respect to the component mounting range 360 ​​of at least one signal conductor pattern 330, depending on the generation condition of the leakage microwave in the relay substrate 118 or the like.

[0244] Furthermore, in the first embodiment and its modified example, each of the signal conductor patterns 330 has one component mounting portion 350, but the present invention is not limited thereto. The component mounting portion 350 only needs to be provided in at least one signal conductor pattern 330, and a plurality of component mounting portions 350 may be provided for one signal conductor pattern 330. That is, at least one component mounting portion 350 may be provided in at least one signal conductor pattern 330.

[0245] Moreover, in Fig. 9 , Fig.10 , Fig.11 , Fig.12 , Fig.13 The number of through holes formed in the ground conductor patterns of the relay substrates 1018, 1118, 1218, 1318, and 1418 shown is an example and is not limited thereto. Fig. 9 , Fig.10 , Fig.11 , Fig.12 , Fig.13 The main idea of ​​the above-mentioned characteristic structure is to set any number and size of through holes in any form. For example, Fig. 9 In the relay substrate 1018 of the fifth variation shown, as long as the number and diameter of through holes provided in the two ground conductor patterns within the component mounting range 360 ​​are different, any number and size of through holes can be provided in the two ground conductor patterns in any form.

[0246] Furthermore, the characteristic structures of the relay substrates 118, 518, etc. of the first embodiment and its modified examples can be arbitrarily combined to form a relay substrate. Fig. 9 The characteristic structure shown in FIG. 1 is used to deflect the propagation direction of the leakage microwave by the asymmetry of the through hole. Figure 3 The structures shown in the figure can be combined to form a relay substrate. Figure 8 The recess 942 or Fig.11 The recess 1276 of the interconnect substrate 1218 of the seventh modification example shown is applicable to interconnect substrates of other modifications, and reduces impedance variation of the signal conductor pattern 330 caused by deviation in mounting position of the electric circuit element in the component mounting portion 350 .

[0247] Furthermore, in the above-described embodiment, the optical modulation element 102 is a DP-QPSK modulator configured using an LN substrate, but the present invention is not limited thereto. For example, the optical modulation element 102 may be any optical modulation element configured using a semiconductor substrate.

[0248] Furthermore, in the above-described embodiment, the light modulator 102 and the relay substrate 118 are housed in the housing 104 . However, in addition to these, electronic circuit elements (driver elements) for operating the light modulator 102 may also be housed in the housing 104 .

[0249] As described above, the optical modulator 100 of the embodiment includes: an optical modulation element 102 including a plurality of signal electrodes 112; a plurality of signal input terminals 124 for inputting electrical signals applied to the signal electrodes 112; a relay substrate 118; and a frame 104 for accommodating the optical modulation element 102 and the relay substrate 118. The relay substrate 118 is formed with a plurality of signal conductor patterns 330 and a plurality of ground conductor patterns 340 for electrically connecting the signal input terminals 124 to the signal electrodes 112. In addition, at least one signal conductor pattern 330 has at least one component mounting portion 350 including an electrical circuit element. Two ground conductor patterns 340 sandwiching the at least one signal conductor pattern 330 on the relay substrate 118 are formed in asymmetrical shapes with respect to the at least one signal conductor pattern 330 in a component mounting range 360 ​​of a square in a plan view with the component mounting portion 350 as the center. Here, the part mounting range 360 ​​is a range of a square in top view, with the extension direction of the at least one signal conductor pattern 330 in the part mounting portion 350 as the direction of one side and the distance from the at least one signal conductor pattern 330 to the nearest adjacent signal conductor pattern 330 as the length of one side.

[0250] Moreover, as shown in an example in the relay substrates 1018, 1318, etc., two ground conductor patterns (for example, 1040a, 1040b or 1340a, 1340b) sandwiching at least one signal conductor pattern 330 are asymmetrically formed within a part mounting range 360 ​​of a square in top view centered on the part mounting portion 350, by having different presence or absence of through holes, through hole diameters, or through hole numbers.

[0251] According to these structures, the propagation direction of leakage microwaves that may be generated from the component mounting portion 350 provided with electric circuit elements in the relay substrate 118 can be deflected, and crosstalk between the signal conductor patterns 330 can be suppressed, thereby achieving good optical modulation characteristics.

[0252] Moreover, as shown as an example by the notch portion 342a in the relay substrate 118, 518, etc., two ground conductor patterns sandwiching at least one signal conductor pattern 330 are formed to have portions having distances from respective edges of the two ground conductor patterns to opposing edges of the at least one signal conductor pattern 330 that are different from each other within the component mounting range 360.

[0253] According to this structure, by simply changing the shape of the ground conductor pattern, the propagation direction of the leakage microwave generated from the component mounting portion 350 can be easily deflected, and the crosstalk between the signal conductor patterns 330 can be suppressed, thereby achieving good optical modulation characteristics.

[0254] Moreover, as shown as an example of a narrow width portion 1174a in a relay substrate 1118, etc., one of the two ground conductor patterns sandwiching at least one signal conductor pattern 330 includes a narrow width portion within the part mounting range 360, and the narrow width portion is narrower than the other of the two ground conductor patterns as measured in a direction orthogonal to the extension direction of the at least one signal conductor pattern 330.

[0255] According to this structure, the deviation of the propagation direction of the leakage microwave generated from the component mounting portion 350 can be strengthened, and the crosstalk between the signal conductor patterns 330 can be suppressed, thereby realizing good optical modulation characteristics.

[0256] Furthermore, as shown as an example of the section 742 a in the relay substrate 818 or the like, one of the two ground conductor patterns sandwiching at least one signal conductor pattern 330 has a blocked section within the component mounting range 360 ​​.

[0257] According to this structure, the propagation direction deviation of the leakage microwave generated from the component mounting portion 350 can be further strengthened, and the crosstalk between the signal conductor patterns 330 can be suppressed, thereby achieving better optical modulation characteristics.

[0258] Moreover, as shown as an example by the recesses 942a, 1276a, etc. in the relay substrates 918, 1218, the other ground conductor pattern of the two ground conductor patterns that sandwich at least one signal conductor pattern 330 and does not include the narrow width portion or the blocked interval is formed so that the separation distance to the signal conductor pattern 330 in the part mounting portion 350 is longer than the separation distance to the signal conductor pattern 330 in a portion other than the part mounting portion 350.

[0259] According to this structure, the change of the characteristic impedance of the signal conductor pattern 330 with respect to the mounting position deviation of the electric circuit element in the component mounting portion 350 can be suppressed, thereby reducing manufacturing variations, and the crosstalk between the signal conductor patterns 330 can be suppressed to achieve good optical modulation characteristics.

[0260] Moreover, the optical modulator 100 can use an optical modulation element 102 that is constructed in a manner to generate two modulated lights that are modulated according to a pair of electrical signals, for example, to perform DP-QPSK modulation, and the relay substrate 118, etc. can be constructed to propagate the pair of electrical signals through a pair of adjacent signal conductor patterns, such as signal conductor patterns 330a and 330b.

[0261] According to this structure, the crosstalk between the two high-frequency electric signals forming a pair and propagating through the adjacent signal conductor patterns 330 can be effectively reduced, thereby realizing good optical modulation characteristics.

[0262] Furthermore, the optical transmission device of the second embodiment includes: an optical modulator 100 using any of the relay substrates shown in the first embodiment or its modified example, and a modulation signal generating unit 2106, which is an electronic circuit that outputs an electrical signal for causing the optical modulator 100 to perform a modulation operation. According to this structure, for example, the propagation of leakage microwaves that become significant with the increase in transmission rate can be suppressed, and crosstalk between a plurality of high-frequency electrical signals driving the optical modulation element 102 can be effectively reduced, thereby achieving stable and good transmission characteristics.

Claims

1. An optical modulator, characterized in that: include: A light modulation element including a plurality of signal electrodes; 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 formed thereon for electrically connecting the signal input terminal and the signal electrode; as well as A frame body is provided to accommodate the light modulator and the relay substrate, wherein At least one of the signal conductor patterns has at least one component mounting portion including an electric circuit element, The two ground conductor patterns sandwiching the at least one signal conductor pattern on the relay substrate have a plan view shape that is asymmetrical with respect to a straight line extending along an extension direction of the at least one signal conductor pattern in the component mounting portion within a component mounting range that is a square in plan view centered on the component mounting portion. The range of the square when viewed from above, i.e., the part mounting range, is a direction in which the extension direction of at least one of the signal conductor patterns in the part mounting portion is taken as a direction of one side, and the distance from the center of the part mounting portion to the portion on the signal conductor pattern that is closest to the center is taken as the length of one side.

2. An optical modulator, characterized in that: include: A light modulation element including a plurality of signal electrodes; 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 formed thereon for electrically connecting the signal input terminal and the signal electrode; as well as A frame body is provided to accommodate the light modulator and the relay substrate, wherein At least one of the signal conductor patterns has at least one component mounting portion including an electric circuit element, The two ground conductor patterns sandwiching the at least one signal conductor pattern on the relay substrate are asymmetrically formed within a component mounting range of a square in a plan view centered on the component mounting portion, by making the presence or absence of through holes, the diameter of through holes, or the number of through holes different from each other, The component mounting range is a range of a square in top view having the extension direction of the at least one signal conductor pattern in the component mounting portion as the direction of one side and the distance from the at least one signal conductor pattern to the nearest adjacent signal conductor pattern as the length of one side.

3. The optical modulator according to claim 1 or 2, characterized in that: The two ground conductor patterns are formed to have portions where distances from respective edges of the two ground conductor patterns to opposing edges of the at least one signal conductor pattern are different from each other within the component mounting range.

4. The optical modulator according to claim 1 or 2, characterized in that: One of the two ground conductor patterns includes a portion within the component mounting range, the width of which, measured in a direction orthogonal to the extending direction of the at least one signal conductor pattern, is narrower than the width of the other of the two ground conductor patterns.

5. The optical modulator according to claim 1 or 2, characterized in that: One of the two ground conductor patterns has a blocked section within the component mounting range, and the other ground conductor pattern has no blocked section within the component mounting range.

6. The optical modulator according to claim 4, characterized in that The other of the two ground conductor patterns has a portion formed so that a separation distance to a portion of the signal conductor pattern constituting the component mounting portion is longer than a separation distance to other portions of the signal conductor pattern within a corresponding component mounting range.

7. The optical modulator according to claim 1 or 2, characterized in that: The optical modulation element is configured to generate two modulated lights modulated according to the pair of electrical signals, respectively. The relay substrate is configured to propagate the pair of electrical signals through a pair of adjacent signal conductor patterns.

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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