Optical modulator and optical transmitting device using the same

Abstract

In an optical modulator provided with a circuit element on a relay substrate, the influence of leakage microwaves generated from the relay substrate is reduced to achieve good modulation characteristics. The optical modulator (100) comprises: an optical modulator (102) configured to generate two beams of modulated light modulated by two sets of electrical signals, each set of electrical signals including two electrical signals, the optical modulator having a plurality of signal electrodes (112a-112d); a plurality of signal input terminals (124a-124d) for inputting electrical signals; a relay substrate (618) formed with a plurality of signal conductor patterns (630a-630d) and a plurality of ground conductor patterns (640a-640d), wherein the two sets of electrical signals are transmitted respectively through two pairs of adjacent signal conductor patterns; and a housing (104). In the optical modulator (100), at least two signal conductor patterns having at least one component mounting portion including a circuit component (350a-350d) are configured such that the signal transmission directions at the component mounting portions, i.e., the first signal transmission directions, are different from each other.

Description

Technical Field

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

[0002] Optical modulators incorporating waveguide-type optical modulators are widely used in high-speed and high-capacity optical fiber communication systems. Among these, optical modulators using LiNbO3 (hereinafter referred to as LN), a material with a photoelectric effect, as their substrates achieve low optical loss and broadband optical modulation characteristics, leading to their widespread use in high-speed and high-capacity optical fiber communication systems.

[0003] This optical modulator, using an LN substrate, is equipped with a Mach-Zehnder optical waveguide and signal electrodes for applying a high-frequency electrical signal as a modulation signal to the optical waveguide. Furthermore, these signal electrodes are connected to pins or connectors serving as signal input terminals on the housing of the optical modulator, via a relay substrate located within the housing. Thus, by connecting these pins or connectors serving as signal input terminals to a circuit substrate carrying the electronic circuitry that causes the optical modulator to perform modulation, the electrical signal output from the electronic circuitry is applied to the signal electrodes of the optical modulator via the relay substrate.

[0004] The modulation method in the optical fiber communication system has been influenced by the trend of increasing transmission capacity in recent years. Multi-value modulation such as QPSK (Quadrature Phase Shift Keying) and DP-QPSK (Dual Polarization-Quadrature Phase Shift Keying) and transmission standards that incorporate polarization multiplexing into multi-value modulation have become mainstream. In addition to being used in backbone optical transmission networks, they are also being introduced into metropolitan area networks.

[0005] Optical modulators that perform QPSK modulation (QPSK optical modulators) and DP-QPSK modulation (DP-QPSK optical modulators) include multiple Mach-Zehnder optical waveguides in a nested structure, each of which has at least one signal electrode. Therefore, these optical modulators have multiple signal electrodes, and the high-frequency electrical signals applied to these signal electrodes cooperate to perform the DP-QPSK modulation described above. Specifically, the DP-QPSK modulator generates two modulated beams, each modulated by a pair of high-frequency electrical signals. These two modulated beams are then combined and output as a single modulated beam.

[0006] In such an optical modulator, a circuit element such as an electric filter is sometimes mounted on a signal line formed on a relay substrate for improving high-frequency characteristics (Patent Documents 1 and 2).

[0007] Figure 13 This is a top view showing an example of the configuration of a conventional optical modulator equipped with a relay substrate equipped with such circuit elements. Optical modulator 2200 includes an optical modulator element 2202, which serves as a DP-QPSK modulator and is formed on, for example, an LN substrate, and a housing 2204 that houses optical modulator element 2202. Housing 2204 comprises a main body 2214a and a cover 2214b. Optical modulator 2200 also includes an input optical fiber 2208 and an output optical fiber 2210, which are fixed to main body 2214a and transmit light to and from optical modulator element 2202.

[0008] The main body 2214a of the housing 2204 is further provided with four signal input terminals 2224a, 2224b, 2224c, and 2224d (hereinafter collectively referred to as signal input terminals 2224) for inputting high-frequency electrical signals from an external electronic circuit to drive the optical modulator 2202. Specifically, the signal input terminals 2224 are center electrodes of electrical connectors 2216a, 2216b, 2216c, and 2216d (hereinafter collectively referred to as electrical connectors 2216), such as high-frequency coaxial connectors. The high-frequency electrical signals input from the signal input terminals 2224 are respectively input to one end of the 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 shell 2204, and the terminal is formed by a terminator 2220 with 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. The two output lights are combined into one light beam by a polarization combining unit 2228, which is composed of a polarization combining prism, etc. The combined light is output to the outside of the housing 2204 via an output optical fiber 2210.

[0010] Figure 14 Yes Figure 13 The figure shows the relay substrate 2218 and its surroundings in the optical modulator 2200. In the optical modulator 2202, the signal electrodes 2212 are provided with ground electrodes 2222a, 2222b, 2222c, 2222d, and 2222e so as to form coplanar waveguides (CPWs).

[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, connecting the four signal input terminals 2224 to the four signal electrodes 2212 of the optical modulator 2202, respectively. These signal conductor patterns 2230, along 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 plane, constitute a high-frequency signal line.

[0012] The four signal conductor patterns 2230 of the relay substrate 2218 are respectively provided with component mounting portions 2250a, 2250b, 2250c, and 2250d (hereinafter also collectively referred to as component mounting portions 2250) on which electrical filters for improving the high-frequency characteristics of the optical modulator 2200 are mounted. Figure 15 yes Figure 14 The partial detail diagram of the J portion of the relay substrate 2218 is shown. Figure 16 yes Figure 15 These figures show the structure of the component mounting portion 2250b as an example of the component mounting portion 2250, and the other component mounting portions 2250a, 2250c, and 2250d also have the same structure.

[0013] Similar to the electrical filter described in Patent Document 1, for example, component mounting portion 2250b is composed of a thin-film resistor 2252b (shown as a shaded portion) formed as a circuit element in a portion of signal conductor pattern 2230b, and a capacitor 2254b mounted on signal conductor pattern 2230b. Furthermore, signal conductor pattern 2230b in component mounting portion 2250b is formed wider than other portions, for example.

[0014] The thin-film resistor 2252b is a structure in which a portion of the signal conductor pattern 2230b is formed with a desired thickness so that the portion has a desired resistance value, and is formed thinner than the thickness of other portions, for example. Furthermore, for example, the capacitor 2254b is a single-plate 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 by, for example, solder. On the other hand, for example, the upper surface electrode of the capacitor 2254b is connected to the wide portion of the signal conductor pattern 2230b connected to the other end of the thin-film resistor 2252b by wire bonding using a conductor lead 2270. Thus, the component mounting portion 2250b forms an electrical filter in which the thin-film resistor 2252b and the capacitor 2254b are connected in parallel.

[0015] Here, if Figure 14As shown, for example, it is preferable to arrange the component mounting portions 2250 such as electrical filters so as to face the same direction and at substantially the same intervals from the perspectives of manufacturing and inspection, and this has been conventionally practiced.

[0016] While DP-QPSK optical modulators like the one described above are currently mostly used at a transmission rate of 100 Gb / s, development is underway to expand this transmission rate to 400 Gb / s and above. As the modulator operates at higher frequencies, circuit elements (such as capacitors 2254b) mounted on the component mounting portion 2250 are selected to have excellent high-frequency characteristics, and the impedance of the component mounting portion 2250 is matched to the line impedance of the signal conductor pattern 2230.

[0017] However, the component mounting portion 2250 may cause disturbances in the high-frequency (microwave) electrical signal transmitted through the signal conductor pattern 2230 due to, for example, a difference in physical shape between the circuit element and the signal conductor pattern 2230, or a deviation in the mounting position of the circuit element. As a result, a portion of the microwave electrical signal leaks from the component mounting portion 2250 as leakage microwaves 2290 ( Figure 14 ), it may act as noise to the adjacent signal conductor pattern 2230 and the signal electrode 2212 on the optical modulation element 2202.

[0018] Furthermore, as described above, in the conventionally implemented structure where component mounting sections 2250 face the same direction and are arranged at approximately equal intervals, leakage microwaves from each component mounting section 2250 can be propagated with directivity toward the same direction. Furthermore, in the case of an optical modulator such as a DP-QPSK optical modulator that generates two beams of modulated light, each modulated by a pair of high-frequency electrical signals, not only are the high-frequency signals in the paired high-frequency electrical signals approximately in phase, but also the high-frequency components of different pairs are approximately the same. Therefore, leakage microwaves having approximately the same phase and frequency components can be radiated from component mounting sections 2250.

[0019] As a result, the leaked microwaves mutually reinforce each other, creating a new problem not anticipated in conventional 100 Gb / s transmission: they act as electrical noise to the surrounding signal conductor pattern 2230 and the signal electrode 2212 of the optical modulator 2202 connected thereto. Furthermore, if a portion of the leaked microwaves generated from the component mounting portion 2250 constituting the electrical filter in the signal conductor pattern 2230 are recoupled with the signal conductor pattern 2230 itself and the signal electrode 2212 of the optical modulator 2202 connected thereto, not only will they act as electrical noise but they will also cause further problems, such as degradation or changes in the filter characteristics of the electrical filter.

[0020] Prior art literature

[0021] Patent Literature

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

[0023] Patent Document 2: Japanese Patent Application Laid-Open No. 2018-54929 Summary of the Invention

[0024] Summary of the Invention

[0025] Problems to be solved by the invention

[0026] Based on the above background, in an optical modulator in which circuit elements such as an electrical filter are provided on a relay substrate that electrically connects the signal electrode of the optical modulator element to the signal input terminal, it is required to suppress electrical noise caused by leakage microwaves that may be generated from a part of the circuit element, and deterioration or fluctuation of high-frequency characteristics, so as to achieve good modulation characteristics.

[0027] Solutions to Problems

[0028] According to one embodiment of the present invention, there is provided an optical modulator comprising: an optical modulator element configured to generate two beams of modulated light modulated by two groups of electrical signals, each group of electrical signals comprising two electrical signals, the optical modulator element comprising a plurality of signal electrodes; a plurality of signal input terminals for inputting electrical signals applied to the signal electrodes, respectively; a relay substrate formed with a plurality of ground conductor patterns and a plurality of signal conductor patterns electrically connecting the signal input terminals to the signal electrodes, and configured to transmit the two groups of electrical signals respectively through two pairs of the signal conductor patterns, each pair of the signal conductor patterns comprising two adjacent signal conductor patterns; and a shell housing the optical modulator element and the relay substrate, wherein at least two of the signal conductor patterns in the optical modulator have at least one component mounting portion comprising a circuit element, and at least two of the signal conductor patterns having the component mounting portions are configured so that the signal transmission directions at the component mounting portions, i.e., the first signal transmission directions, are different from each other.

[0029] According to another embodiment of the present invention, at least one of the signal conductor patterns having the component mounting portion is configured such that the signal transmission direction at the connection portion connected to the signal input terminal, i.e., the second signal transmission direction, is different from the first signal transmission direction, and / or is configured to include a portion in the interval from the connection portion connected to the signal electrode to the component mounting portion where the signal transmission direction changes to a third signal transmission direction different from the first signal transmission direction.

[0030] According to another aspect of the present invention, the at least two signal conductor patterns having the component mounting portion include two signal conductor patterns forming a pair, and the first signal transmission directions are different between the two signal conductor patterns forming the same pair.

[0031] According to another aspect of the present invention, all of the signal conductor patterns each include at least one component mounting portion, and two signal conductor patterns forming the same pair are configured such that the first signal transmission directions in the respective pairs are different from each other.

[0032] According to another embodiment of the present invention, all of the signal conductor patterns are respectively configured such that the signal transmission direction at the connection part connected to the signal input terminal, i.e., the second signal transmission direction, is different from the first signal transmission direction, and / or are configured to include a part in the interval from the connection part connected to the signal electrode to the component mounting part where the signal transmission direction changes to a third signal transmission direction different from the first signal transmission direction.

[0033] According to another aspect of the present invention, all of the signal conductor patterns are configured so that the first signal transmission directions thereof are different from each other.

[0034] According to another aspect of the present invention, the component mounting portions provided on all the signal conductor patterns are not arranged on a common straight line on the interconnect substrate.

[0035] According to another aspect of the present invention, the circuit elements constituting the component mounting portion constitute an electric filter.

[0036] Another aspect of the present invention provides an optical transmission device comprising: any one of the above-described optical modulators; and an electronic circuit that outputs an electrical signal for causing the optical modulator to perform a modulation operation.

[0037] It should be noted that this specification incorporates the entire contents of Japanese Patent Application No. 2019-175516 filed on September 26, 2019.

[0038] Effects of the Invention

[0039] According to the present invention, in an optical modulator having circuit elements such as an electrical filter on a relay substrate, electrical noise caused by leakage microwaves that may be generated from part of the circuit elements and degradation or fluctuation of high-frequency characteristics can be suppressed, thereby achieving good modulation characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a top view of the optical modulator according to the first embodiment of the present invention.

[0041] Figure 2 yes Figure 1 A side view of the light modulator is shown.

[0042] Figure 3 yes Figure 1 Detailed view of section A of the light modulator shown.

[0043] Figure 4 This is a diagram showing the structure of a relay substrate in a first modified example of the optical modulator according to the first embodiment.

[0044] Figure 5 This is a diagram showing the structure of a relay substrate in a second modified example of the optical modulator according to the first embodiment.

[0045] Figure 6 This is a diagram showing the structure of a relay substrate in a third modified example of the optical modulator according to the first embodiment.

[0046] Figure 7 This is a diagram showing the structure of a relay substrate in a fourth modified example of the optical modulator according to the first embodiment.

[0047] Figure 8 It is a plan view showing the structure of the optical modulator according to the second embodiment.

[0048] Figure 9 yes Figure 8 Detailed view of part B of the light modulator shown.

[0049] Figure 10 It is a plan view showing the structure of the optical modulator according to the third embodiment.

[0050] Figure 11 yes Figure 10 Detailed view of section C of the light modulator shown.

[0051] Figure 12 This is a diagram showing the configuration of an optical transmission device according to a fourth embodiment of the present invention.

[0052] Figure 13 An example of the structure of a conventional optical modulator is shown.

[0053] Figure 14This is a diagram showing a partial detail of the periphery of a relay substrate in a conventional optical modulator.

[0054] Figure 15 Yes Figure 14 A detailed partial view of the details of section J is shown.

[0055] Figure 16 yes Figure 15 The XVI-XVI sectional view of the partial detail drawing is shown. DETAILED DESCRIPTION

[0056] Typically, leakage microwaves generated by the component mounting portion of a relay substrate spread as a whole, with the component mounting portion serving as a point source. However, they exhibit directivity along the propagation direction of the high-frequency signal on the signal conductor pattern within the component mounting portion. The present invention, by setting the orientation (extension direction) and position of the portions on the signal conductor pattern supporting each component mounting portion to predetermined orientations and positions, prevents these directional leakage microwaves from reinforcing each other and acting as electrical noise, or from recoupling on their own signal conductor patterns and thus fluctuating high-frequency characteristics, thereby achieving excellent modulation characteristics. It should be noted that, hereinafter, the "direction of the leakage microwaves" refers to the direction of the aforementioned directivity of the leakage microwaves.

[0057] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0058] [First embodiment]

[0059] First, a first embodiment of the present invention will be described. Figure 1 1 is a plan view showing the structure of the 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 view of part A in FIG.

[0060] The optical modulator 100 includes an optical modulator 102 , a housing 104 that houses the optical modulator 102 , an input optical fiber 108 for allowing light to enter the optical modulator 102 , and an output optical fiber 110 that guides light output from the optical modulator 102 to the outside of the housing 104 .

[0061] The optical modulator 102 is a DP-QPSK modulator that performs optical modulation at, for example, 400 Gb / s, and is composed of two nested Mach-Zehnder optical waveguides disposed on, for example, an LN substrate, each of which includes two Mach-Zehnder optical waveguides. The four Mach-Zehnder optical waveguides constituting the two nested Mach-Zehnder optical waveguides are provided with four signal electrodes 112a, 112b, 112c, and 112d (hereinafter collectively referred to as signal electrodes 112) that modulate the light waves propagating through the Mach-Zehnder optical waveguides. Furthermore, as is known in the art, ground electrodes 122a, 122b, 122c, 122d, and 122e are provided on the surface of the LN substrate of the optical modulator 102, such that, for example, the four signal electrodes 112a, 112b, 112c, and 112d constitute coplanar waveguides (CPWs). Figure 3 .exist Figure 1 Not shown in the figure. ).

[0062] Specifically, the ground electrodes 122a, 122b, 122c, 122d, and 122e (hereinafter collectively referred to as ground electrodes 122) are arranged within the plane 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.

[0063] Four high-frequency electrical signals (modulation signals) are input to each of the four signal electrodes 112. These high-frequency electrical signals cooperate to control the propagation of light waves in the four Mach-Zehnder optical waveguides, and perform 400 Gb / s DP-QPSK modulation as a whole.

[0064] Specifically, two pairs of high-frequency electrical signals are applied to each of the four signal electrodes 112, each pair consisting of two high-frequency electrical signals. The optical modulator 102 is configured to generate two modulated light beams 106a and 106b (arrows in the figure), each modulated by a pair of electrical signals. The generated two modulated light beams 106a and 106b are output from the two output optical waveguides 126a and 126b of the two nested Mach-Zehnder optical waveguides constituting the optical modulator 102. In this embodiment, one pair of two high-frequency electrical signals is applied to the signal electrodes 112a and 112b, generating the modulated light 106a output from the output optical waveguide 126a. The other pair of two high-frequency electrical signals is applied to the signal electrodes 112c and 112d, generating the modulated light 106b output from the output optical waveguide 126b. The two modulated lights 106 a and 106 b are combined into one beam by a polarization combining unit 128 composed of a polarization combining prism or the like, and then output to the outside of the housing 104 via an output optical fiber 110 .

[0065] The housing 104 is composed of a main body 114a and a cover 114b that fix the light modulating element 102. Figure 1 In the figure, only a portion of cover 114b is shown on the right side. However, in reality, cover 114b is arranged to cover the entire box-shaped main body 114a, thereby hermetically sealing the interior of housing 104. Main body 114a is made of metal or, for example, gold-plated ceramic, and functions electrically as a conductor. Furthermore, housing 104 is typically provided with multiple pins for DC bias control, etc., but these are omitted in this figure.

[0066] The main body 114a is provided with electrical connectors 116a, 116b, 116c, 116d (hereinafter also collectively referred to as electrical connectors 116) as coaxial connectors having signal input terminals 124a, 124b, 124c, 124d (hereinafter also collectively referred to as signal input terminals 124), and the signal input terminals 124a, 124b, 124c, 124d input high-frequency electrical signals respectively applied to the signal electrodes 112a, 112b, 112c, 112d of the optical modulator 102.

[0067] The electrical connectors 116 are each a socket for a push-on coaxial connector, for example, and include a cylindrical ground conductor. The signal input terminals 124 are formed by a center conductor (core wire) extending along the centerline of this cylindrical ground conductor. These cylindrical ground conductors are each electrically connected to and fixed to the main body 114a. Therefore, the main body 114a forms part of the grounding line that supplies the ground potential. Furthermore, the signal input terminals 124 are each electrically connected to one end of the signal electrode 112 of the optical modulator 102 via the relay substrate 118.

[0068] 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 is propagated within the signal electrode 112 as a traveling wave.

[0069] Figure 3 yes Figure 1 The detailed view of section A shows the structure of the relay substrate 118 and its surroundings. Signal conductor patterns 330a, 330b, 330c, and 330d (hereinafter collectively referred to as signal conductor patterns 330) and ground conductor patterns 340a, 340b, 340c, 340d, and 340e (hereinafter collectively referred to as ground conductor patterns 340) are formed on the relay substrate 118.

[0070] Signal conductor patterns 330a, 330b, 330c, and 330d connect signal electrodes 112a, 112b, 112c, and 112d to their corresponding signal input terminals 124, respectively. Specifically, the high-frequency electrical signal pair that generates modulated light 106a is delivered to signal electrodes 112a and 112b via the mutually adjacent signal conductor patterns 330a and 330b. Furthermore, the high-frequency electrical signal pair that generates modulated light 106b is delivered to signal electrodes 112d and 112d via the mutually adjacent signal conductor patterns 330c and 330d. Specifically, signal conductor patterns 330a and 330b form one pair of signal conductor patterns and transmit the high-frequency electrical signal pair (group) on one side, while signal conductor patterns 330c and 330d form the other pair of signal conductor patterns and transmit the high-frequency electrical signal pair (group) on the other side.

[0071] The relay substrate 118 is connected to the surface (where the signal conductor pattern 330 and the ground conductor pattern 340 are formed) of the relay substrate 118. Figure 3 A back ground conductor (not shown) is formed on, for example, the entire back surface of the housing 104 (opposite to the back surface shown). The back ground conductor is secured to the main body 114a of the housing 104 using, for example, solder, brazing material, or a conductive adhesive. Thus, the back ground conductor becomes a component of the ground line. The ground conductor pattern 340 is connected to the back ground conductor via appropriate through-holes (not shown) and is thus connected to the ground line.

[0072] Ground conductor patterns 340a, 340b, 340c, 340d, and 340e are provided on the surface of the interconnect substrate 118 so as to sandwich the signal conductor patterns 330a, 330b, 330c, and 330d.

[0073] In this embodiment, the signal conductor pattern 330 extends in the vertical direction as shown in the figure, and one end thereof is connected to the signal input terminal 124 at the lower side of the relay substrate 118. Here, the side of the relay substrate 118 where the signal conductor pattern 330 is connected to the signal input terminal 124 is referred to as the signal input side 318a.

[0074] 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 shown in the figure by wire bonding using, for example, a conductor lead 326. The conductor lead 326 can be set as, for example, a gold wire. Here, the side of the side of the relay substrate 118 that connects the signal conductor pattern 330 to the signal electrode 112 of the optical modulator 102 is called the signal output side 318b. In this 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 Among the sides of the relay substrate 118 , the other two opposing sides other than the signal input side 318 a and the signal output side 318 b are referred to as side edges (side sides) 318 c and 318 d .

[0075] In the optical modulator 102, the ground electrodes 122, which form a coplanar line with the signal electrode 112, are electrically connected to respective ends of the ground conductor pattern 340 at the signal output side 318b of the relay substrate 118 by wire bonding using, for example, the conductor wires 326, as described above. Note that the wire bonding using the conductor wires 326 described above is merely an example and is not limiting. Alternatively, ribbon bonding using, for example, a conductor ribbon such as a gold ribbon may be used in place of wire bonding using the conductor wires 326.

[0076] Signal conductor patterns 330a, 330b, 330c, and 330d have component mounting portions 350a, 350b, 350c, and 350d, respectively (hereinafter collectively referred to as component mounting portion 350). These component mounting portions 350a, 350b, 350c, and 350d are portions (deeply shaded in the figure) where circuit elements constituting electrical filters (bandpass filters, highpass filters, etc.) are located. Here, circuit elements refer to active and / or passive components that serve as functional elements constituting a circuit, and do not include wiring patterns or pads provided solely for electrical connection.

[0077] The component mounting portion 350 is, for example, Figures 13 to 16 Similarly to the component mounting portion 2250 shown in FIG. 1 , a circuit element such as a capacitor and / or a circuit element such as a thin film resistor can be mounted on a portion of the signal conductor pattern 330 that is wider than the other portions. Figure 15 、 Figure 16 The illustrated signal conductor pattern 2230b also has a wide portion formed in the signal conductor pattern 330, and carries a capacitor similar to capacitor 2254b. Furthermore, a thin-film resistor similar to 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. However, the widening of the signal conductor pattern 330 in the component mounting portion 350 is merely an example, and the signal conductor pattern 330 in the component mounting portion 350 may also be formed to have the same width as the rest of the component mounting portion.

[0078] In this embodiment, the two signal conductor patterns 330, into which the two paired high-frequency electrical signals are input, extend at an angle to each other, thereby causing the signal transmission directions at the component mounting portions 350 to differ. It should be noted that the signal transmission direction at the component mounting portions 350 corresponds to the first signal transmission direction.

[0079] Specifically, the signal conductor pattern 330a of one of the two paired signal conductor patterns 330a and 330b to which the high-frequency electrical signals are input is formed to extend in a direction having an angle relative to the extension direction of the other signal conductor pattern 330b (in the example shown in the figure, a direction inclined to the right in the figure).

[0080] Typically, the direction of leaked microwaves generated from the component mounting portion 350 is along the signal transmission direction of the component mounting portion 350. Furthermore, the signal transmission direction of the component mounting portion 350 is typically along the extending direction of the signal conductor pattern 330 at the portion where the component mounting portion 350 is formed.

[0081] In this embodiment, the signal conductor pattern 330a is formed along a direction that is angled with respect to the signal conductor pattern 330b, so the directions of the leaked microwaves generated from the component mounting portions 350a and 350b are also angled with each other. Figure 3 As shown, the leakage microwaves generated from the component mounting portions 350a and 350b have a large intensity distribution in a directional range centered on the extending direction of the signal conductor patterns 330a and 330b, as shown in the range sandwiched by the two single-dash arrows extending from the component mounting portions 350a and 350b.

[0082] As a result, mutual interference between the leaked microwaves generated from the component mounting portions 350a and 350b is suppressed, preventing these leaked microwaves from reinforcing each other and acting as electrical noise. Specifically, the generation of electrical noise caused by interference between the leaked microwaves generated from the component mounting portions 350a and 350b can be suppressed between the signal conductor patterns 330a and 330b, which each transmit a pair of high-frequency electrical signals that are prone to interference.

[0083] Similarly, one of the two paired signal conductor patterns 330c and 330d, to which the other high-frequency electrical signal is input, is formed so as to extend in a direction that is angled relative to the extending direction of the other signal conductor pattern 330c (in the example shown in the figure, in a direction inclined to the left in the figure). Figure 3 In the embodiment shown as a range sandwiched between two dashed arrows extending from the component mounting portions 350c and 350d, a large intensity distribution is present in a direction range having a center along the extending direction of the signal conductor patterns 330c and 330d.

[0084] As a result, generation of electrical noise caused by interference between leaked microwaves generated from the component mounting portions 350c and 350d can be suppressed even between the signal conductor patterns 330c and 330d that transmit a pair of high-frequency electrical signals that are prone to interference.

[0085] Here, in relay substrate 118, for example, signal conductor patterns 330a and 330b, to which a paired high-frequency electrical signal is input, are configured such that the signal transmission directions at component mounting portions 350a and 350b are separated from each other. However, this is not limiting. The signal transmission directions at component mounting portion 350 need only be different from each other, and may also be configured such that the signal transmission directions are close to each other.

[0086] Next, a modification of the relay substrate used in the optical modulator 100 will be described.

[0087] <First Modification>

[0088] Figure 4 This is a diagram showing the structure of a relay substrate 418 according to a first modification example, which is equivalent to Figure 3 The relay substrate 418 is a partial detail diagram of the first embodiment shown in FIG. Figure 1 The optical modulator 100 shown in FIG. 1 can be used to replace the relay substrate 118. Figure 4 In, about Figure 3 The same components as those of the relay substrate 118 shown in FIG. Figure 3 The same reference numerals as in Figure 3 Description.

[0089] The relay substrate 418 has Figure 3The relay substrate 118 shown has the same structure as the relay substrate 118, but differs from the relay substrate 118 in that it includes signal conductor patterns 430a and 430d instead of the signal conductor patterns 330a and 330d. Furthermore, the relay substrate 418 differs from the relay substrate 118 in that it includes ground conductor patterns 440a, 440b, 440d, and 440e instead of the ground conductor patterns 340a, 340b, 340d, and 340e.

[0090] Signal conductor patterns 430a and 430d have the same structure as signal conductor patterns 330a and 330d, but their shapes differ from those of signal conductor patterns 330a and 330d. Ground conductor patterns 440a, 440b, 440d, and 440e have the same structure as ground conductor patterns 340a, 340b, 340d, and 340e, but they form coplanar lines with signal conductor patterns 430a and 430d, and therefore their shapes differ from those of ground conductor patterns 340a, 340b, 340d, and 340e.

[0091] Specifically, the signal conductor patterns 430a and 430d have the same structure as the signal conductor patterns 330a and 330d except for the extending directions of the connection portions connected to the signal input terminals 124a and 124d.

[0092] Therefore, in the relay substrate 418, as in the relay substrate 118, the signal transmission direction at the component mounting portions 350a and 350d is different from the signal transmission direction at the adjacent component mounting portions 350b and 350c, respectively. Therefore, between the component mounting portions 350a and 350b, and between the component mounting portions 350c and 350d, the mutually reinforcing interference between the leakage microwaves generated from these component mounting portions can be suppressed.

[0093] However, unlike signal conductor patterns 330a and 330d, signal conductor patterns 430a and 430d on relay substrate 418 are not linear as a whole. Instead, the directions in which signal conductor patterns 430a and 430d extend at the connection portions with signal input terminals 124a and 124d, formed near signal input side 318a, differ from the directions in which they extend at component mounting portions 350a and 350d, respectively. The signal transmission direction at the connection portions between signal conductor patterns 330a, 430a, and 430d and signal input terminal 124 corresponds to the second signal transmission direction.

[0094] Specifically, in relay substrate 418, the signal transmission directions of signal conductor patterns 430a and 430d at component mounting portions 350a and 350d differ from the signal transmission directions at the connection portions with signal input terminals 124a and 124d. For example, in relay substrate 418, the signal conductor patterns 430a and 430d at the connection portions with signal input terminals 124a and 124d extend in a direction parallel to signal conductor patterns 330b and 330c (or parallel to side edges 318c and 318d), and thus differ from the direction of extension at component mounting portions 350a and 350d.

[0095] As a result, the direction of the leakage microwaves generated at the connection portion of the relay substrate 418 differs from the direction of the leakage microwaves generated at the component mounting portion 350a. Therefore, in the relay substrate 418, interference between two leakage microwaves generated at two different portions of a single signal conductor pattern 430a that are prone to interference (i.e., two leakage microwaves generated at the connection portion of the signal conductor pattern 430a connected to the signal input terminal 124a and at the component mounting portion 350a, respectively) can be suppressed.

[0096] Furthermore, similarly to the signal conductor pattern 430a, the signal conductor pattern 430d also generates two leakage microwaves in different directions at the connection portion with the signal input terminal 124d and the component mounting portion 350d, thereby suppressing interference between these leakage microwaves.

[0097] As a result, in interconnect substrate 418 , generation of electrical noise caused by leaked microwaves generated from component mounting portion 350 can be further suppressed compared to interconnect substrate 118 .

[0098] <Second Modification>

[0099] Next, a second modified example of the relay substrate used in the optical modulator 100 will be described.

[0100] Figure 5 This is a diagram showing the structure of a relay substrate 518 according to a second modification example, which is equivalent to Figure 3 The relay substrate 518 is a partial detail diagram of the first embodiment shown in FIG. Figure 1 The optical modulator 100 shown in FIG. 1 can be used to replace the relay substrate 118. Figure 5 In, about Figure 3 The same components as those of the relay substrate 118 shown in FIG. Figure 3 The same reference numerals as in the above are used to indicate Figure 3 Description.

[0101] The relay substrate 518 has Figure 3 Although the structure is similar to that of relay substrate 118 shown in the figure, relay substrate 518 differs from relay substrate 118 in that signal conductor patterns 530a and 530d are included instead of signal conductor patterns 330a and 330d. Relay substrate 518 also differs from relay substrate 518 in that ground conductor patterns 540a, 540b, 540d, and 540e are included instead of ground conductor patterns 340a, 340b, 340d, and 340e.

[0102] Signal conductor patterns 530a and 530d have the same structure as signal conductor patterns 330a and 330d, but their shapes differ from those of signal conductor patterns 530a and 530d. Ground conductor patterns 540a, 540b, 540d, and 540e have the same structure as ground conductor patterns 340a, 340b, 340d, and 340e, but they form coplanar lines with signal conductor patterns 530a and 530d, and therefore their shapes differ from those of ground conductor patterns 340a, 340b, 340d, and 340e.

[0103] Specifically, the signal conductor patterns 530a and 530d have the same shape as the signal electrodes 112a and 112d except for the shape of the section from the connection portion to the component mounting portion 350a and 350d. Figure 4 The signal conductor patterns 430a and 430d of the first modification shown have the same structure.

[0104] Thus, the relay substrate 518 and Figure 4 The relay substrate 418 shown can similarly suppress interference between leakage microwaves between the component mounting portions 350a and 350b and between the component mounting portions 350c and 350d, and can also suppress interference between leakage microwaves between the portion of the signal conductor pattern 530a connecting the signal input terminal 124a and the component mounting portion 350a, and between the portion of the signal conductor pattern 530d connecting the signal input terminal 124d and the component mounting portion 350a, thereby suppressing the generation of electrical noise caused by their interference.

[0105] However, the signal conductor patterns 530a and 530d of the relay substrate 518 are Figure 4 The signal conductor patterns 430a and 430d of the first variant shown are different. The section from the connection portion of the signal output edge 318b connected to the signal electrodes 112a and 112d to the component mounting portions 350a and 350d respectively includes the extension direction of the signal conductor patterns 530a and 530d in the section, and further the section where the signal transmission direction changes to a direction different from the signal transmission direction at the component mounting portions 350a and 350d.

[0106] As a result, on relay substrate 518, signal conductor patterns 530a and 530d include portions within their respective corresponding sections having signal transmission directions different from those of leakage microwaves generated from component mounting portions 350a and 350d. This prevents leakage microwaves generated from component mounting portions 350a and 350d provided on signal conductor patterns 530a and 530d from recoupling to the same signal conductor patterns 530a and 530d, respectively. This suppression of recoupling occurs because leakage microwaves generally have a low tendency to couple with transmission modes within conductor patterns having signal transmission directions different from those of the leakage microwaves.

[0107] Typically, when recoupling of leaked microwaves from the component mounting portions 350a, 350d to their own signal conductor patterns 530a, 530d occurs, the high-frequency characteristics (frequency characteristics) of the signal conductor patterns 530a, 530d as a whole, including the component mounting portions 350a, 350d, which serve as electrical filters, for example, are changed, which may affect the modulation operation of the optical modulator 100.

[0108] In contrast, in the relay substrate 518 having the above-described structure, in addition to suppressing the above-described electrical noise, the above-described recoupling can also be effectively suppressed as described above, thereby also suppressing the fluctuation of high-frequency characteristics associated with the recoupling, and achieving good modulation operation.

[0109] It should be noted that the signal transmission direction of the signal conductor patterns 530a, 530b in the section from the connection portion connected to the signal electrode 112 to the component mounting portion 350 after changing to a direction different from the signal transmission direction of the corresponding component mounting portion 350 corresponds to the third signal transmission direction.

[0110] <Third Modification>

[0111] Next, a third modified example of the relay substrate used in the optical modulator 100 will be described.

[0112] Figure 6 This is a diagram showing the structure of a relay substrate 618 according to a third modification example, which is equivalent to Figure 3 The relay substrate 618 is a partial detail diagram of the first embodiment shown in FIG. Figure 1 The optical modulator 100 shown in FIG. 1 can be used to replace the relay substrate 118. Figure 6 In, about Figure 3 The components of the relay substrate 118 shown in FIG. Figure 5 The components of the relay substrate 518 of the second modified example shown in FIG. 5 are the same as those of the relay substrate 518, and the components of the relay substrate 518 are the same as those of the relay substrate 518. Figure 3 and Figure 5 The same reference numerals as in the above are used to indicate Figure 3 and Figure 5 Description.

[0113] The relay substrate 618 has Figure 5 The relay substrate 518 shown has the same structure as the relay substrate 518, but differs from the relay substrate 518 in that it includes signal conductor patterns 630b and 630c instead of the signal conductor patterns 330b and 330c. Furthermore, the relay substrate 618 differs from the relay substrate 518 in that it includes ground conductor patterns 640b, 640c, and 640d instead of the ground conductor patterns 540b, 540c, and 540d.

[0114] Signal conductor patterns 630b and 630c have the same structure as signal conductor patterns 330b and 330c, but their shapes differ from those of signal conductor patterns 330b and 330c. Ground conductor patterns 640b, 640c, and 640d have the same structure as ground conductor patterns 540b, 540c, and 540d, but they form a coplanar line with signal conductor patterns 630b and 630c, and therefore their shapes differ from those of ground conductor patterns 540b, 540c, and 540d.

[0115] Specifically, the signal conductor patterns 630b and 630c have the same structure as the signal conductor patterns 330b and 330c, but differ from the signal conductor patterns 330b and 330c in that they are not linear but have the same shape as the signal conductor patterns 530a and 530d.

[0116] Specifically, signal conductor patterns 630b and 630c are formed so that the signal transmission directions at component mounting portions 350b and 350c are different from the signal transmission directions at component mounting portions 350a and 350d of adjacent signal conductor patterns 530a and 530b, respectively. Here, signal conductor patterns 530a and 630b, and 630c and 530d, respectively, transmit paired high-frequency electrical signals.

[0117] The signal conductor patterns 630b and 630c are formed so that the signal transmission direction at the connection portions with the signal input terminals 124b and 124c differs from the signal transmission direction at the component mounting portions 350b and 350c, respectively. Furthermore, the signal conductor patterns 630b and 630c each include a portion in the section from the connection portion with the signal electrodes 112b and 112c of the optical modulator 102 to the component mounting portions 350b and 350c, respectively, where the extending direction of the conductor pattern in that section, and thus the signal transmission direction in that section, changes to a direction different from the signal transmission direction at the component mounting portions 350b and 350c.

[0118] By adopting the above-mentioned structure, in this modification, in the signal conductor patterns 630b and 630c, as in the signal conductor patterns 530a and 530d, the direction of the leaked microwaves from the connection portions connected to the signal input terminals 124b and 124c is made different from the direction of the leaked microwaves from the component mounting portions 350b and 350c, thereby suppressing the interference between these leaked microwaves. Figure 5 Compared with the relay substrate shown in FIG. 1 , the electrical noise caused by the interference between the leaked microwaves can be further reduced.

[0119] Furthermore, in this variation, similar to signal conductor patterns 530a and 530d, signal conductor patterns 630b and 630c also have a portion where the signal transmission direction changes to a direction different from the signal transmission direction at component mounting portions 350b and 350c, in the section leading to the connection portion with signal electrodes 112b and 112c of optical modulator 102. This prevents leakage microwaves generated from component mounting portions 350b and 350c from recoupling with their own signal conductor patterns 630b and 630c. Consequently, fluctuations in the high-frequency characteristics of the entire signal conductor patterns 630b and 630c, including the component mounting portions 350b and 350c that constitute the electrical filter, can be suppressed.

[0120] As a result, in the relay substrate 618, Figure 5 Compared with the relay substrate 518 shown, better light modulation operation can be achieved.

[0121] <Fourth Modification>

[0122] Next, a fourth modification of the relay substrate used in the optical modulator 100 will be described.

[0123] Figure 7 This is a diagram showing the structure of a relay substrate 718 according to a fourth modification example, which is equivalent to Figure 3 The relay substrate 718 is a partial detail diagram of the first embodiment shown in FIG. Figure 1 The optical modulator 100 shown in FIG. 1 can be used to replace the relay substrate 118. Figure 7 In, about Figure 3 The same components as those of the relay substrate 118 shown in FIG. Figure 3 The same reference numerals as in Figure 3 Description.

[0124] The relay substrate 718 has Figure 6However, the interconnect substrate 718 is configured so that the component mounting portions 350 are not arranged in a straight line in the horizontal direction as shown in the figure, as in the interconnect substrate 618 (ie, not arranged linearly).

[0125] Specifically, the relay substrate 718 has Figure 6 The relay substrate 618 shown in FIG. 1 has the same structure as the relay substrate 618, but differs in that it includes signal conductor patterns 730a, 730b, 730c, and 730d (hereinafter collectively referred to as signal conductor patterns 730) instead of the signal conductor patterns 530a, 630b, 630c, and 530d. Furthermore, the relay substrate 718 differs from the relay substrate 618 in that it includes ground conductor patterns 740a, 740b, 740c, 740d, and 740e (hereinafter collectively referred to as ground conductor patterns 740) instead of the ground conductor patterns 540a, 640b, 640c, 640d, and 540e.

[0126] Signal conductor patterns 730a, 730b, 730c, and 730d have the same structure as signal conductor patterns 530a, 630b, 630c, and 530d, but their shapes differ from those of signal conductor patterns 530a, 630b, 630c, and 530d. Ground conductor patterns 740a, 740b, 740c, 740d, and 740e have the same structure as ground conductor patterns 540a, 640b, 640c, 640d, and 540e, but they form coplanar lines with signal conductor patterns 730a, 730b, 730c, and 730d, and therefore their shapes differ from those of ground conductor patterns 540a, 640b, 640c, 640d, and 540e.

[0127] Specifically, signal conductor patterns 730a, 730b, 730c, and 730d have the same structures as signal conductor patterns 530a, 630b, 630c, and 530d, respectively. However, component mounting portions 350 are arranged not in a straight line, but in a zigzag pattern, for example. However, this zigzag pattern is merely an example, and component mounting portions 350 may be arranged in any position as long as no more than three component mounting portions 350 are arranged on a common straight line.

[0128] Thus, in the relay substrate 718, it is possible to prevent the components mounting portions 350 from functioning as point wave sources (e.g., at a specific location on the relay substrate 718), and to prevent three or more leaked microwaves from overlapping and causing strong interference. Figure 6 Compared with the relay substrate 618 shown, the generation of electrical noise can be further suppressed, and good light modulation characteristics can be achieved.

[0129] It should be noted that, in order to suppress the interference of leaked microwaves from three or more component mounting portions 350, the component mounting portions 350 are not arranged in a straight line but are preferably arranged at irregular positions (random positions). The zigzag arrangement is an example of an irregular arrangement.

[0130] Hereinafter, the signal conductor patterns 330 , 430 a , 430 d , 530 a , 530 d , 630 b , 630 c and the signal conductor pattern 730 are collectively referred to as the signal conductor pattern 330 or the like.

[0131] [Second embodiment]

[0132] Next, we will describe an optical modulator according to a second embodiment of the present invention. In the optical modulator 100 of the first embodiment described above, the arrangement pitch of the signal electrodes 112 of the optical modulator 102 is equal to the arrangement pitch of the signal input terminals 124. However, the present invention is not limited to this. The arrangement pitch of the signal electrodes of the optical modulator can be larger or smaller than the arrangement pitch of the signal input terminals 124. This embodiment is the first example in which the arrangement pitch of the signal electrodes of the optical modulator is smaller than the arrangement pitch of the signal input terminals 124.

[0133] Figure 8 FIG. 1 is a plan view showing the structure of an optical modulator 800 according to a second embodiment of the present invention. Figure 9 yes Figure 8 A detailed view of part B in FIG.

[0134] As described below, the relay substrate 818 used in the optical modulator 800 of this embodiment has Figure 7 Although the optical modulator 802 has the same features as the relay substrate 718 shown in FIG. 1 , the signal conductor pattern 930a and the like are formed in a shape different from the signal conductor pattern 730a and the like of the relay substrate 718. In particular, in this embodiment, the arrangement pitch of the signal electrodes 812 of the optical modulator 802 is narrower than the arrangement pitch of the signal input terminals 124 provided in the housing 104.

[0135] exist Figure 8 In, about Figure 1 The same components as those of the optical modulator 100 of the first embodiment shown in FIG. Figure 1 The same reference numerals as in Figure 1 Description. Figure 8 The light modulator 800 shown has Figure 1 The optical modulator 100 shown has the same structure as that shown, but differs in that it includes an optical modulator 802 and an interconnect substrate 818 instead of the optical modulator 102 and the interconnect substrate 118 .

[0136] The optical modulator 802 has the same structure as the optical modulator 102, but is different in that it includes signal electrodes 812a, 812b, 812c, and 812d (hereinafter collectively referred to as signal electrodes 812) instead of the signal electrode 112, and includes ground electrodes 822a, 822b, 822c, 822d, and 822e (hereinafter collectively referred to as ground electrodes 822) instead of the ground electrode 122 (see FIG. Figure 9 ).

[0137] The signal electrodes 812 have the same structure as the signal electrodes 112, but the spacing between the signal electrodes 812 is different from the spacing between the signal electrodes 112. Furthermore, the ground electrodes 822 have the same structure as the ground electrodes 122, but form a coplanar line with the signal electrodes 812, and therefore their shapes are different from those of the ground electrodes 122.

[0138] Figure 9 yes Figure 8 The partial detail diagram of the B portion shown in FIG. 1 shows the relay substrate 818 and its surrounding structure in the optical modulator 800. Figure 9 In, about Figure 3 The same components as the relay substrate 118 shown in FIG. Figure 3 The same reference numerals as in Figure 3 Description.

[0139] The relay substrate 818 has Figure 7 The relay substrate 718 shown in FIG. 1 has the same structure as the relay substrate 718 shown in FIG. 1 , but differs in that it includes signal conductor patterns 930a, 930b, 930c, and 930d (hereinafter collectively referred to as signal conductor patterns 930) instead of the signal conductor patterns 730a, 730b, 730c, and 730d. Furthermore, the relay substrate 818 differs in that it includes ground conductor patterns 940a, 940b, 940c, 940d, and 940e (hereinafter collectively referred to as ground conductor patterns 940) instead of the ground conductor patterns 740a, 740b, 740c, 740d, and 740e. Figure 7 The relay substrate 718 shown is different.

[0140] Four signal conductor patterns 930 and Figure 7 The signal conductor pattern 730 of the illustrated relay substrate 718 similarly has the following features, but is formed in a shape different from that of the signal conductor pattern 730 .

[0141] 1) The signal transmission directions at the component mounting portion 350 are different from each other.

[0142] 2) Each signal conductor pattern 930 is formed so that the signal transmission direction at the connection portion with the signal input terminal 124 is different from the signal transmission direction at the component mounting portion 350 .

[0143] 3) Each signal conductor pattern 930 includes a portion where the signal transmission direction changes to a direction different from the signal transmission direction of the component mounting portion 350 in the section from the connection portion of the light modulator 802 to the signal electrode 812 to the component mounting portion 350 .

[0144] 4) The signal conductor pattern 930 is configured so that the component mounting portions 350 (eg, three or more component mounting portions 350 ) are not arranged in a straight line as a whole.

[0145] It should be noted that the ground conductor pattern 940 has the same structure as the ground conductor pattern 740 , but forms a coplanar line together with the signal conductor pattern 930 , and therefore their shapes are different from those of the ground conductor pattern 740 .

[0146] Specifically, signal conductor patterns 930a, 930b, 930c, and 930d have the same structure as signal conductor patterns 730a, 730b, 730c, and 730d, but the portion where component mounting portion 350 is located extends toward the left in the drawing or extends obliquely toward the left in the drawing. Thus, signal conductor patterns 930 connect each of signal input terminals 124 to each of signal electrodes 812 of optical modulation element 802, which are arranged at intervals narrower than the arrangement pitch of the signal input terminals 124.

[0147] Furthermore, the portions of the signal conductor pattern 930 where the component mounting portion 350 is located are tilted leftward at different angles as shown, thereby extending in different directions. It should be noted that the portion of the signal conductor pattern 930d extending leftward as shown can be interpreted as having such a leftward tilt angle of 90 degrees.

[0148] Thus, the relay substrate 818 is configured so that the signal transmission directions at the component mounting portion 350 are different from each other. Figure 3 The relay substrate 118 shown, Figure 4 The relay substrate 418 shown, Figure 5 The relay substrate 518 shown, Figure 6 The relay substrate 618 shown, Figure 7 The illustrated relay substrate 718 can similarly suppress interference between leaked microwaves generated from the component mounting portions 350 , thereby suppressing electrical noise caused by the interference.

[0149] Furthermore, the connection portions of the signal conductor pattern 930 connected to the signal input terminal 124 extend in the vertical direction as shown, that is, in directions parallel to the side edges 318c and 318d perpendicular to the signal input side 318a. Thus, the signal conductor patterns 930a, 930b, 930c, and 930d are configured so that the signal transmission direction at the connection portions connected to the signal input terminal 124 is different from the signal transmission direction at the component mounting portions 350a, 350b, 350c, and 350d. Therefore, in the relay substrate 818, Figure 4 The relay substrate 418 shown, Figure 5 The relay substrate 518 shown, Figure 6 The relay substrate 618 shown, Figure 7 The relay substrate 718 shown in the figure can also suppress the interference between the leakage microwave generated from the connection portion connected to the signal input terminal 124 and the leakage microwave generated from the component mounting portion 350, and can also suppress the electrical noise caused by the interference.

[0150] Furthermore, the signal conductor pattern 930 is formed so as to include a portion where its extension direction changes in a direction parallel to the side edges 318c and 318d in the section from the connection portion of the optical modulator 802 connected to the signal electrode 812 to the component mounting portion 350. Thus, the relay substrate 818 includes a portion where its signal transmission direction changes in a direction different from the signal transmission direction of the component mounting portion 350 in the above-mentioned section. Figure 5 The relay substrate 518 shown, Figure 6 The relay substrate 618 shown, Figure 7 Similarly, the relay substrate 718 shown can suppress recoupling of leaked microwaves generated from the component mounting portions 350a, 350b, 350c, and 350d with their corresponding signal conductor patterns 930a, 80b, 930c, and 930d. Consequently, fluctuations in the high-frequency characteristics of the signal conductor patterns 930 as a whole, including the component mounting portion 350 serving as an electrical filter, can be suppressed.

[0151] As described above, in the relay substrate 818, Figure 7 The relay substrate 718 shown can also suppress the generation of electrical noise and fluctuations in high-frequency characteristics, thereby achieving good modulation characteristics.

[0152] [Third embodiment]

[0153] Next, the optical modulator according to the third embodiment of the present invention will be described. In the relay substrates 118, 418, 518, 618, and 718 of the first embodiment and its variations, as well as the relay substrate 918 of the second embodiment, the signal conductor patterns 330, etc., and 940 are configured to include bends. However, the present invention is not limited to such bends. These signal conductor patterns 330, etc., and 940 can also be configured using curves instead of bends.

[0154] This embodiment is the second example in which the arrangement pitch of the signal electrodes of the optical modulator is smaller than the arrangement pitch of the signal input terminals 124. In particular, as described later, the curved portions of the signal conductor patterns 1130a, 1130b, 1130c, and 1130d of the relay substrate 1018 are not bent but are composed of curves.

[0155] Figure 10 FIG. 1 is a plan view showing the structure of an optical modulator 1000 according to a third embodiment of the present invention. Figure 11 yes Figure 10 Partial detail of section C in the figure. Figure 10 In, about Figure 1 The same components as those of the optical modulator 100 of the first embodiment shown in FIG. Figure 1 The same reference numerals as in Figure 1 Description. Figure 10 The optical modulator 1000 shown has Figure 1 The optical modulator 100 shown has the same structure as that of the optical modulator 100 , but differs in that it includes an optical modulator 1002 and an interconnect substrate 1018 instead of the optical modulator 102 and the interconnect substrate 118 .

[0156] The optical modulator 1002 has the same structure as the optical modulator 102, but is different in that it has signal electrodes 1012a, 1012b, 1012c, and 1012d (hereinafter collectively referred to as signal electrodes 1012) instead of the signal electrode 112, and has ground electrodes 1022a, 1022b, 1022c, 1022d, and 1022e (hereinafter also collectively referred to as ground electrodes 1022) instead of the ground electrode 122.

[0157] The signal electrodes 1012 have the same structure as the signal electrodes 112, but the spacing between the signal electrodes 1012 is different from the spacing between the signal electrodes 112. Furthermore, the ground electrodes 1022 have the same structure as the ground electrodes 122, but form a coplanar line with the signal electrodes 1012, and therefore their shapes are different from those of the ground electrodes 122.

[0158] Figure 11 yes Figure 10The partial detail diagram of the C portion shown in FIG. 1 shows the structure of the relay substrate 1018 and its surroundings in the optical modulator 1000. Figure 11 In, about Figure 3 The same components as the relay substrate 118 shown in FIG. Figure 3 The same reference numerals as in Figure 3 Description.

[0159] The relay substrate 1018 has Figure 7 The relay substrate 718 shown in FIG. 1 has the same structure as the relay substrate 718 shown in FIG. 1 , but differs in that it includes signal conductor patterns 1130a, 1130b, 1130c, and 1130d (hereinafter collectively referred to as signal conductor patterns 1130) instead of the signal conductor patterns 730a, 730b, 730c, and 730d. Furthermore, the relay substrate 1018 differs in that it includes ground conductor patterns 1140a, 1140b, 1140c, 1140d, and 1140e (hereinafter collectively referred to as ground conductor patterns 1140) instead of the ground conductor patterns 740a, 740b, 740c, 740d, and 740e. Figure 7 The relay substrate 718 shown is different.

[0160] Four signal conductor patterns 1130 and Figure 9 The signal conductor pattern 930 of the relay substrate 818 of the second embodiment shown similarly has the above-mentioned four features, but is formed in a shape different from that of the signal conductor pattern 930 .

[0161] It should be noted that the ground conductor pattern 1140 has the same structure as the ground conductor pattern 740 , but forms a coplanar line together with the signal conductor pattern 1130 , and therefore their shapes are different from those of the ground conductor pattern 740 .

[0162] The signal conductor pattern 1130 has the same structure as the signal conductor pattern 730 , but its shape is different from that of the signal conductor pattern 730 , and its bent portion is formed by a curve instead of a bend.

[0163] Furthermore, the signal transmission directions of the portions of the signal conductor patterns 1130 where the component mounting portions 350 are located differ from one another. More specifically, the portions of the signal conductor patterns 1130a, 1130b, and 1130c where the component mounting portions 350a, 350b, and 350c are located extend in a direction tilted toward the left in the figure, with these tilt angles being different. Furthermore, the portion of the signal conductor pattern 1130d where the component mounting portion 350d is located extends in a direction tilted toward the right in the figure.

[0164] Thus, in the relay substrate 1018, Figure 3 The relay substrate 118 shown, Figure 4 The relay substrate 418 shown, Figure 5 The relay substrate 518 shown, Figure 6 The relay substrate 618 shown, Figure 7 The relay substrate 718 shown, Figure 9 The relay substrate 818 shown can similarly suppress interference between the leaked microwaves generated from the component mounting portions 350 , thereby suppressing electrical noise caused by the interference.

[0165] Furthermore, the connection portions of signal conductor pattern 1130 connected to signal input terminal 124 extend in the vertical direction shown, that is, in directions parallel to side edges 318c and 318d perpendicular to signal input side 318a. Thus, signal conductor patterns 1130a, 1130b, 1130c, and 1130d are configured so that the signal transmission direction at the connection portions connected to signal input terminal 124 differs from the signal transmission direction at component mounting portions 350a, 350b, 350c, and 350d.

[0166] Therefore, in the relay substrate 1018, Figure 4 The relay substrate 418 shown, Figure 5 The relay substrate 518 shown, Figure 6 The relay substrate 618 shown, Figure 7 The relay substrate 718 shown, Figure 9 The relay substrate 818 shown can similarly suppress interference between leakage microwaves generated from the connection portion between the signal conductor pattern 1130 and the signal input terminal 124 and leakage microwaves generated from the component mounting portion 350 , and can also suppress electrical noise caused by this interference.

[0167] Furthermore, the signal conductor pattern 1130 is formed so as to include a portion where its extension direction changes in a direction parallel to the side edges 318c and 318d in the section from the connection portion of the optical modulator 1002 connected to the signal electrode 1012 to the component mounting portion 350. Thus, the relay substrate 1018 includes a portion where its signal transmission direction changes in a direction different from the signal transmission direction of the component mounting portion 350 in the above-mentioned section. Figure 5 The relay substrate 518 shown, Figure 6 The relay substrate 618 shown, Figure 7 The relay substrate 718 shown, Figure 9Similarly, relay substrate 818 shown can suppress recoupling of leaked microwaves generated from component mounting portions 350a, 350b, 350c, and 350d with their corresponding signal conductor patterns 1130a, 1130b, 1130c, and 1130d. Consequently, fluctuations in the high-frequency characteristics of the entire signal conductor pattern 1130, including component mounting portion 350 serving as an electrical filter, can be suppressed.

[0168] As described above, in the relay substrate 1018, Figure 7 The relay substrate 718 shown can also suppress the generation of electrical noise and fluctuations in high-frequency characteristics, thereby achieving good modulation characteristics.

[0169] [Fourth embodiment]

[0170] Next, the fourth embodiment of the present invention will be described. This embodiment is an optical transmission device equipped with an optical modulator 100 having a relay substrate 118 according to the first embodiment. It should be noted that this configuration is merely an example, and the optical transmission device may also incorporate optical modulators 100 using relay substrates 418, 518, 618, and 718 according to the first to fourth modified embodiments, or optical modulators 800 and 1000 according to the second and third embodiments, respectively, having relay substrates 818 and 1018, in place of the optical modulator 100 having a relay substrate 118.

[0171] Figure 12 2100 is a diagram showing the configuration of an optical transmitter according to this embodiment. The optical transmitter 2100 includes an optical modulator 100 , a light source 2104 for causing light to enter the optical modulator 100 , a modulation signal generator 2106 , and a modulation data generator 2108 .

[0172] The modulation data generation unit 2108 receives the transmission data assigned 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.

[0173] The modulation signal generator 2106 is an electronic circuit (driver circuit) that outputs an electrical signal for causing the optical modulator 100 to perform a modulation operation. Based on the modulation data output by the modulation data generator 2108, the modulation signal generator 2106 generates a modulation signal as a high-frequency signal for causing the optical modulator 100 to perform an optical modulation operation in accordance with the modulation data, and inputs the modulation signal to the optical modulator 100. The modulation signal is composed of four high-frequency electrical signals corresponding to the four signal electrodes 112a, 112b, 112c, and 112d of the optical modulation element 102 included in the optical modulator 100.

[0174] The four high-frequency electrical signals are input from the respective signal input terminals 124a, 124b, 124c, 124d of the electrical connectors 116a, 116b, 116c, 116d of the optical modulator 100 to the signal conductor patterns 330a, 330b, 330c, 330d of the relay substrate 118, and are then input to the signal electrodes 112a, 112b, 112c, 112d of the optical modulator element 102 via these signal conductor patterns 330a and the like.

[0175] As a result, the light output from the light source 2104 is modulated by, for example, DP-QPSK by the optical modulator 100 , becomes modulated light, and is then output from the optical transmission device 2100 .

[0176] In particular, in the optical transmitter 2100, interference between leaked microwaves that may be generated from the component mounting portion 350 in the relay substrate 118 of the optical modulator 100 can be suppressed, thereby ensuring good modulation characteristics and achieving good transmission characteristics. Furthermore, in the optical transmitter 2100, if the optical modulator 100 having the relay substrate 118 is replaced with an optical modulator having, for example, Figure 5 The optical modulator 100 using the relay substrate 518 of the second modified example shown can suppress recoupling of leaked microwaves generated from the component mounting portion 350 with its own signal conductor pattern 330, etc., and can also suppress fluctuations in the high-frequency characteristics of the component mounting portion 350 as a whole, including, for example, the electrical filter. As a result, the optical modulator 100 can achieve better modulation characteristics, and thus achieve better transmission characteristics in the optical transmitter 2100.

[0177] It should be noted that the present invention is not limited to the configurations of the above-described embodiment and its modified examples, and can be implemented in various forms without departing from the spirit and scope of the invention.

[0178] For example, in the first embodiment and its variations, as well as the second and third embodiments described above, a component mounting portion 350 is provided for each of the signal conductor patterns 330, 830, and 1130, but this is not limiting. A component mounting portion 350 need only be provided for at least two (i.e., multiple) of the signal conductor patterns 330, 830, and 1130, and multiple components may be provided for the same signal conductor pattern. That is, at least one component mounting portion 350 may be provided for multiple signal conductor patterns. It should be noted that, when multiple component mounting portions are provided for the same signal conductor pattern, the signal conductor pattern is preferably formed so that the signal transmission directions of these component mounting portions differ from each other.

[0179] In addition, Figure 5 、 6In FIG. 7 , for example, regarding the signal conductor pattern 530a, the signal transmission direction (first signal transmission direction) of the component mounting portion 350a is different from the signal transmission direction (second signal transmission direction) at the connection portion connected to the signal input terminal 124a, and the section from the connection portion connected to the signal electrode 112a to the component mounting portion 350a includes a portion where the signal transmission direction changes to a third signal transmission direction different from the first signal transmission direction. However, the present invention is not limited to this. Regarding a single signal conductor pattern 330, the first signal transmission direction of the component mounting portion 350 may be different from the second signal transmission direction, or the section from the connection portion connected to the signal electrode 112 to the component mounting portion 350 may include a portion where the signal transmission direction changes to the third signal transmission direction.

[0180] In the above-described embodiments, the optical modulators 102, 802, and 1002 are DP-QPSK modulators constructed using an LN substrate. However, this is not limiting. Instead of DP-QPSK modulation, the optical modulators 102, 802, and 1002 can employ any modulation scheme, such as QAM modulation, that uses two modulated beams modulated by two paired high-frequency signals. Furthermore, the optical modulators 102, 802, and 1002 can be constructed using a semiconductor substrate instead of an LN substrate.

[0181] In the above embodiment, the housing 104 accommodates the light modulator 102 and the relay substrate 118 . However, electronic circuit elements (driver elements) for operating the light modulator 102 and the like may also be accommodated in the housing 104 .

[0182] As described above, the optical modulator 100 of the first embodiment includes: an optical modulator 102 having a plurality of signal electrodes 112; a relay substrate 118; and a housing 104 that accommodates the optical modulator 102 and relay substrate 118. The optical modulator 102 generates two modulated beams 106a and 106b modulated by two sets of electrical signals, each containing two electrical signals. The relay substrate 118 includes a plurality of signal input terminals 124 for inputting electrical signals applied to the signal electrodes 112, a plurality of signal conductor patterns 330 electrically connecting the signal input terminals 124 to the signal electrodes 112, and a plurality of ground conductor patterns 340. Furthermore, the relay substrate 118 transmits the two sets of electrical signals through two pairs of signal conductor patterns 330, each consisting of two adjacent signal conductor patterns 330. Furthermore, at least two of the signal conductor patterns 330 have at least one component mounting portion 530 containing a circuit element, and the signal transmission direction, i.e., the first signal transmission direction, of the component mounting portions 530 differs from each other.

[0183] According to this structure, in the optical modulator 100 in which the signal conductor pattern 330 on the relay substrate 118 is provided with a component mounting portion 350 composed of circuit elements such as an electrical filter, electrical noise caused by interference between leakage microwaves generated from these component mounting portions 350 can be suppressed, thereby achieving good modulation characteristics.

[0184] Furthermore, the optical modulator 100 may include a relay substrate 418. In the relay substrate 418, at least one of the signal conductor patterns 330 and the like including the component mounting portion 350 is configured such that a second signal transmission direction, which is a signal transmission direction at a connection portion with the signal input terminal 124, is different from the first signal transmission direction.

[0185] According to this structure, the generation of electrical noise caused by, for example, interference between leakage microwaves generated from the connection portion between the signal conductor pattern 430d and the signal input terminal 124d and leakage microwaves generated from the component mounting portion 350d of the signal conductor pattern 430d can be suppressed, thereby achieving better modulation characteristics.

[0186] Furthermore, the optical modulator 100 may include a relay substrate 518. In the relay substrate 518, at least one of the signal conductor patterns 330 and the component mounting portion 350 includes a portion where the signal transmission direction changes to a third signal transmission direction different from the first signal transmission direction, in the section from the connection portion connected to the signal electrode 112 to the component mounting portion 350.

[0187] This configuration can suppress, for example, the recoupling of leaked microwaves generated from the component mounting portion 350d within the signal conductor pattern 530d within the aforementioned section into the signal conductor pattern 530d itself. Consequently, in the optical modulator 100 including the relay substrate 518, fluctuations in the high-frequency characteristics of the entire signal conductor pattern 330d, including the component mounting portion 350d, caused by such recoupling can be suppressed, thereby achieving improved modulation characteristics.

[0188] In the optical modulator 100 , at least two signal conductor patterns 330 etc. provided with the component mounting portion 350 include the two signal conductor patterns 330 etc. forming the pair, and the first signal transmission directions of the two signal conductor patterns 330 etc. forming the same pair are different from each other.

[0189] Typically, adjacent signal conductor patterns 330, etc., which transmit two paired high-frequency electrical signals, are susceptible to electrical noise and fluctuations in high-frequency characteristics. In contrast, the above-described configuration suppresses interference between leakage microwaves generated from the component mounting portion 530 between adjacent signal conductor patterns 330, etc., which transmit such paired high-frequency electrical signals, thereby achieving excellent modulation characteristics.

[0190] In the optical modulator 100 , all the signal conductor patterns 330 and the like each include at least one component mounting portion 350 , and two signal conductor patterns 330 and the like forming the same pair are all configured so that the first signal transmission directions are different from each other.

[0191] According to this configuration, in a structure including the component mounting portion 350 such as all the signal conductor patterns 330 , interference between leaked microwaves generated from these component mounting portions 350 can be suppressed, thereby achieving good modulation characteristics.

[0192] Furthermore, the optical modulator 100 may include a relay substrate 618. In the relay substrate 618, all signal conductor patterns 330 and the like are configured such that the first signal transmission direction is different from the second signal transmission direction and the third signal transmission direction. Here, the first signal transmission direction does not necessarily need to be different from both the second signal transmission direction and the third signal transmission direction, and may be different from one of the second and third signal transmission directions.

[0193] According to this structure, electrical noise caused by leakage microwaves and / or fluctuations in high-frequency characteristics of the signal conductor patterns 330 etc. caused by recoupling of leakage microwaves can be suppressed in all signal conductor patterns 330 etc., thereby achieving good modulation characteristics.

[0194] Furthermore, in the optical modulator 100, all signal conductor patterns 330 include component mounting portions 350, and the first signal transmission directions differ for each component mounting portion 350. This configuration suppresses interference between leaked microwaves generated from the component mounting portions 350 among all signal conductor patterns 330, thereby achieving excellent modulation characteristics.

[0195] Furthermore, the optical modulator 100 may include a relay substrate 718. In the relay substrate 718, the component mounting portions 350 provided on all signal conductor patterns 330 and the like are not arranged on a common straight line on the relay substrate 718. This configuration can prevent the occurrence of strong interference of leaked microwaves at specific locations on the relay substrate 718, for example, and achieve excellent modulation characteristics.

[0196] Furthermore, in the optical modulator 100, the component mounting portion constitutes an electrical filter. With this configuration, by providing an electrical filter having desired frequency characteristics as the component mounting portion 350 on the signal conductor pattern 330 or the like, the designed modulation characteristics can be improved, while interference and recoupling of leaked microwaves can be suppressed, achieving the designed modulation characteristics more faithfully.

[0197] Furthermore, the optical transmitter 2100 of the fourth embodiment described above includes the optical modulator 100 using any of the relay substrates described in the first embodiment and its variations, or the optical modulator 800 or 1000 described in the second or third embodiment, and includes, for example, a modulation signal generator 2106, which is an electronic circuit that outputs an electrical signal for causing the optical modulator to perform a modulation operation. This configuration suppresses the effects of leaked microwaves, which become significant as the transmission rate increases, effectively reduces electrical noise and / or fluctuations in high-frequency characteristics, and achieves stable and excellent transmission characteristics.

[0198] Description of labels

[0199] 100, 800, 1000, 2200…Optical modulator, 102, 802, 1002, 2202…Optical modulation element, 104, 2204…Casing, 106a, 106b…Modulated light, 108, 2208…Input optical fiber, 110, 2210…Output optical fiber, 112, 112a, 112b, 112c, 112d, 812, 812a, 812b, 812c, 812d, 1012, 1012a, 1012b, 1012c, 1012d, 2212, 2212a, 2212b, 2212c, 2212d…Signal electrode, 114a, 2214a…Main body, 114b, 2214b…Cover, 116, 116 a, 116b, 116c, 116d, 2216, 2216a, 2216b, 2216c, 2216d…Electrical connector, 118, 418, 518, 618, 718, 818, 1018, 2218…Relay substrate, 120, 2220…Terminator, 122, 122a, 122b, 122c, 122d, 122e, 822, 822a, 822b, 822c, 822d, 822e, 1022, 1022a, 1022b, 1022c, 1022d, 1022e, 2222a, 2222b, 2222c, 2222d, 2222e…Ground electrode, 124, 124a, 124b, 1 24c, 124d, 2224, 2224a, 2224b, 2224c, 2224d…signal input terminal, 126a, 126b…output optical waveguide, 318a…signal input edge, 318b…signal output edge, 318c, 318d…side edge, 326, 2270…conductor lead, 330, 330a, 330b, 330c, 330d, 430a, 430d, 530a, 530d, 630b, 630c, 730, 730a, 730b, 730c, 730d, 930, 930a, 930b, 930c, 930d, 1130, 1130a, 1130b, 1130c, 1130d, 2230 , 2230a, 2230b, 2230c, 2230d ... signal conductor patterns, 340, 340a, 340b, 340c, 340d, 340e, 440a, 440b, 440d, 440e, 540a, 540b, 540d, 540e, 640b, 640c, 640d, 740, 740a, 740b, 740c, 740d, 740e, 940, 940a, 940b, 940c, 940d, 940e, 1140, 1140a, 1140b, 1140c, 1140d, 1140e, 2240a, 2240b, 2240c, 2240d, 2240e ... ground conductor patterns,350, 350a, 350b, 350c, 350d...component mounting portion, 2100...optical transmitter, 2104...light source, 2106...modulation signal generator, 2108...modulation data generator, 2252b...thin-film resistor, 2254b...capacitor, 2290...leakage microwave.

Claims

1. An optical modulator comprising: an optical modulation element configured to generate two modulated beams modulated by two sets of electrical signals, each set of electrical signals including two electrical signals, the optical modulation element comprising a plurality of signal electrodes; a plurality of signal input terminals for inputting electrical signals applied to the signal electrodes respectively, the signal input terminals being central electrodes of an electrical connector serving as a high-frequency coaxial connector; a relay substrate having a plurality of ground conductor patterns and a plurality of signal conductor patterns electrically connecting the signal input terminal and the signal electrode, and configured to transmit the two sets of electrical signals respectively through two pairs of the signal conductor patterns, each pair of the signal conductor patterns being composed of two adjacent signal conductor patterns; and a housing for accommodating the light modulating element and the relay substrate; In the optical modulator, At least two of the signal conductor patterns have at least one component mounting portion including a circuit element. At least two of the signal conductor patterns provided with the component mounting portions are configured so that the signal transmission directions at the component mounting portions, that is, the first signal transmission directions, are different from each other. The at least two signal conductor patterns provided with the component mounting portion include the two signal conductor patterns forming the pair. Between the two signal conductor patterns forming the same pair, the first signal transmission directions are directions separated from each other.

2. The optical modulator according to claim 1, wherein At least one of the signal conductor patterns having the component mounting portion is configured such that a second signal transmission direction at a connection portion connected to the signal input terminal is different from the first signal transmission direction, and / or The section from the connection portion connected to the signal electrode to the component mounting portion is configured to include a portion where the signal transmission direction changes to a third signal transmission direction different from the first signal transmission direction.

3. The optical modulator according to claim 1 or 2, wherein: All of the signal conductor patterns each include at least one component mounting portion. The two signal conductor patterns forming the same pair are configured such that the first signal transmission directions in the respective pairs are different from each other.

4. The optical modulator according to claim 3, wherein All of the signal conductor patterns are respectively configured such that the signal transmission direction at the connection portion connected to the signal input terminal, that is, the second signal transmission direction, is different from the first signal transmission direction, and / or The section from the connection portion connected to the signal electrode to the component mounting portion is configured to include a portion where the signal transmission direction changes to a third signal transmission direction different from the first signal transmission direction.

5. The optical modulator according to claim 3, wherein All the signal conductor patterns are configured so that the first signal transmission directions thereof are different from each other.

6. The optical modulator according to claim 3, wherein The component mounting portions provided on all the signal conductor patterns are not arranged on a common straight line on the relay substrate.

7. The optical modulator according to claim 1 or 2, wherein: The circuit elements constituting the component mounting portion constitute an electric filter.

8. An optical transmission device comprising: The optical modulator according to any one of claims 1 to 7; and The electronic circuit outputs an electrical signal for causing the optical modulator to perform a modulation operation.

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