Optical modulator and optical transmission device using the same

Abstract

The present invention provides an optical modulator and an optical transmitting device using the optical modulator. In an optical modulator having a relay substrate, the effects of reflection, radiation, leakage, etc. of electrical signals generated on the relay substrate or its surroundings can be effectively reduced, thereby achieving good optical modulation characteristics. The optical modulator comprises: an optical modulation element having a plurality of signal electrodes; a housing for housing the optical modulation element; a plurality of signal input terminals for inputting electrical signals applied to the respective signal electrodes; and a relay substrate having a plurality of signal conductor patterns and a plurality of ground conductor patterns formed thereon, the plurality of signal conductor patterns electrically connecting the respective signal input terminals to the respective signal electrodes, wherein the relay substrate is housed inside the housing, and at least one input side ground conductor pattern extending from at least one ground conductor pattern is formed on an input side surface having a side on which the electrical signal from the signal input terminal is input to the signal conductor pattern.

Description

Technical Field

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

[0002] High-speed and high-capacity optical fiber communication systems often use optical modulators incorporating waveguide-type optical modulation elements. Among these, optical modulators using LiNbO3 (hereinafter referred to as LN), which exhibits an electro-optical effect, as substrates are widely used due to their low optical loss and ability to achieve wide-bandwidth optical modulation characteristics.

[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. The pins or connectors, serving as signal input terminals, are connected to a circuit substrate carrying the electronic circuitry that causes the optical modulator to perform modulation operations. This allows the electrical signals output from the electronic circuitry to be applied to the signal electrodes of the optical modulator via the relay substrate.

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

[0005] An optical modulator that performs QPSK modulation (QPSK optical modulator) or DP-QPSK modulation (DP-QPSK optical modulator) includes multiple Mach-Zehnder optical waveguides in a nested structure, known as a nested structure. Each of these Mach-Zehnder optical waveguides includes at least one signal electrode. Therefore, these optical modulators include multiple signal electrodes, and the high-frequency electrical signals supplied to these signal electrodes cooperate to perform the DP-QPSK modulation described above.

[0006] Furthermore, in an optical modulator that coordinates high-frequency electrical signals supplied to multiple signal electrodes, it is necessary to effectively reduce leakage and reflection of high-frequency electrical signals within the relay substrate, as all high-frequency electrical signals must be input to the signal electrodes of the optical modulator without being affected by noise. In particular, as the relay substrate size is further reduced to meet the demand for miniaturization of optical modulators, multiple different high-frequency electrical signals are concentrated and propagated within the confined relay substrate. This can lead to interference between the leakage and radiation of the individual high-frequency electrical signals within the relay substrate, which can easily act as noise.

[0007] In the past, in order to suppress the reflection, radiation and / or leakage of high frequencies in the relay substrate as described above, the following measures have been taken: the impedance in the connection portion between the conductor pattern of the relay substrate and the above-mentioned pins is made more accurately consistent with the impedance of the respective high-frequency transmission paths constituting the conductor pattern and the pins (for example, refer to Patent Document 1).

[0008] However, in addition to the demand for miniaturized optical modulators and the continued need for increased transmission capacity, the continued advancement of modulation speeds, such as those required for DP-QPSK modulation, necessitates further suppression of reflections and radiation of high-frequency signals generated in the relay board. For example, currently used DP-QPSK modulators operate at a transmission rate of 100 Gb / s. However, if this transmission rate is increased to 400 Gb / s or higher, the effects of reflections and radiation of high-frequency electrical signals generated in the relay board on the optical modulation operation must be further suppressed. This necessitates new structural measures, either in addition to or in place of the conventional optical modulator structure.

[0009] Furthermore, the solder used to secure the relay substrate to the housing adheres to the relay substrate in an irregular manner, causing impedance variations in the relay substrate, thereby impairing the stable propagation of electrical signals. This problem becomes more serious (and increasingly difficult to ignore) as the transmission rate increases.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Publication No. 2018-106091 Summary of the Invention

[0013] Problems to be solved by the invention

[0014] Based on the above background, in an optical modulator having a relay substrate that electrically connects each signal electrode of an optical modulator element to each signal input terminal, it is required to further reduce the effects of reflection, radiation, leakage, etc. of electrical signals generated in or around the relay substrate, so as to achieve good optical modulation characteristics even when the transmission rate exceeds 400 Gb / s.

[0015] Technical solutions to problems

[0016] One embodiment of the present invention relates to an optical modulator, comprising: an optical modulator element having a plurality of signal electrodes; a housing for accommodating the optical modulator element; a plurality of signal input terminals for inputting electrical signals applied to each of the signal electrodes; and a relay substrate formed with a plurality of signal conductor patterns and a plurality of ground conductor patterns, the plurality of signal conductor patterns electrically connecting each of the signal input terminals with each of the signal electrodes, wherein the relay substrate is accommodated inside the housing, and at least one input side ground conductor pattern extending from at least one of the ground conductor patterns is formed on an input side side having a side on which the electrical signal from the signal input terminal is input to the signal conductor pattern.

[0017] According to another embodiment of the present invention, an input grounding recess is formed on the input side surface, and the input grounding recess extends from the back surface of the relay substrate opposite to the front surface where the signal conductor pattern is formed, and at least a portion of the input side grounding conductor pattern is arranged inside the input grounding recess.

[0018] According to another aspect of the present invention, the input grounding recess extends to both the front surface and the rear surface, and the input side surface grounding conductor pattern is formed inside the input grounding recess.

[0019] According to another aspect of the present invention, at least one side signal conductor pattern extending from at least one of the signal conductor patterns is further formed on the input-side side surface.

[0020] According to another aspect of the present invention, a signal recess is formed on the input-side side surface, extending from the surface on which the signal conductor pattern is formed, and at least a portion of the side signal conductor pattern is formed inside the signal recess.

[0021] According to another embodiment of the present invention, at least one output side ground conductor pattern extending from at least one ground conductor pattern is formed on the output side surface of the relay substrate, the side on which the electrical signal is output from the signal conductor pattern to the signal electrode.

[0022] According to another aspect of the present invention, an output grounding recess extending from the rear surface of the relay substrate is formed on the output side surface, and at least a portion of the output side surface grounding conductor pattern is provided inside the output grounding recess.

[0023] According to another aspect of the present invention, the signal input terminal and the signal conductor pattern are electrically connected by solder, brazing material, or a conductive adhesive, and the signal conductor pattern and the signal electrode are electrically connected via a conductor wire or a conductor ribbon.

[0024] According to another aspect of the present invention, the input-side side surface of the relay substrate abuts against a structure connected to a ground potential, and the input-side surface ground conductor pattern provided on the input-side side surface is electrically connected to the structure.

[0025] According to another aspect of the present invention, the structure is connected to a ground potential via the housing.

[0026] According to another aspect of the present invention, the structure is the housing.

[0027] Another aspect of the present invention relates to an optical transmission device including: 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.

[0028] Effects of the Invention

[0029] According to the present invention, in an optical modulator having a relay substrate, the effects of reflection, radiation, leakage, etc. of electrical signals generated in or around the relay substrate are further reduced, and good optical modulation characteristics can be achieved even when the transmission rate exceeds 400 Gb / s. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a top view of the optical modulator according to the first embodiment of the present invention.

[0031] Figure 2 yes Figure 1 A side view of the light modulator is shown in FIG.

[0032] Figure 3 yes Figure 1 Detail of section A of the light modulator is shown in FIG.

[0033] Figure 4 It is viewed from the side where the signal input terminal is configured. Figure 1 FIG is a perspective view of the front surface of the relay substrate of the optical modulator shown in FIG.

[0034] Figure 5 It is viewed from the side where the signal input terminal is configured. Figure 1FIG2 is a perspective view of the back side of the relay substrate of the optical modulator shown in FIG2.

[0035] Figure 6 The light modulating element is viewed from the side where the light modulating element is configured. Figure 1 FIG is a perspective view of the front surface of the relay substrate of the optical modulator shown in FIG.

[0036] Figure 7 This is a diagram showing a first modified example of the relay substrate used in the optical modulator according to the first embodiment.

[0037] Figure 8 This is a diagram showing a second modified example of the relay substrate used in the optical modulator according to the first embodiment.

[0038] Figure 9 This is a diagram showing a third modified example of the relay substrate used in the optical modulator according to the first embodiment.

[0039] Figure 10 yes Figure 9 Detailed diagram of part B of the relay substrate is shown in FIG.

[0040] Figure 11 This is a perspective view of the front surface of a relay substrate according to a fourth modified example of the optical modulator used in the first embodiment, as viewed from the side where the signal input terminals are arranged.

[0041] Figure 12 This is a perspective view of the front surface of a relay substrate used in a fourth modified example of the optical modulator according to the first embodiment, as viewed from the side where the optical modulation element is arranged.

[0042] Figure 13 It is a top view of an optical modulator according to a second embodiment of the present invention.

[0043] Figure 14 yes Figure 13 The CC cross-sectional view of the light modulator shown in FIG.

[0044] Figure 15 It is shown for Figure 13 , which shows the structure of the base of the optical modulator and the positional relationship between the relay substrate fixed to the base and the base.

[0045] Figure 16 It is shown for Figure 13 FIG. 5 is a diagram showing a modified example of a base of an optical modulator.

[0046] Figure 17 This is a diagram showing the configuration of an optical transmission device according to a third embodiment of the present invention.

[0047] Label Description

[0048] 100, 1300, 1702…Optical modulator, 102…Optical modulation element, 104, 1304…Casing, 108…Input optical fiber, 110…Output optical fiber, 112a, 112b, 112c, 112d…Signal electrode, 114a, 1314a…Casing, 114b, 1314b…Cover, 116a, 116b, 116c, 116d…Electrical connector, 118, 718, 818, 918, 1118…Relay substrate, 120…Terminator, 1 22a, 122b, 122c, 122d…ground electrodes, 124a, 124b, 124c, 124d…signal input terminals, 126…conductor wire, 314…inner wall surface, 330a, 330b, 330c, 330d…signal conductor pattern, 340a, 340b, 340c, 340d, 340e, 542…ground conductor pattern, 418a…signal input side, 418b…input side, 418c…signal output side, 418d…output side Side, 442a, 442b, 442c, 442d, 442e... input side ground conductor pattern, 750a, 750b, 750c, 750d, 750e, 850a, 850b, 850c, 850d, 850e... input ground recess, 952a, 952b, 952c, 952d... side signal conductor pattern, 954a, 954b, 954c, 954d... signal recess, 1250a, 1250b, 1250c, 1 250d, 1250e…output side grounding conductor pattern, 1254a, 1254b, 1254c, 1254d, 1254e…output grounding recess, 1360, 1660…base, 1562, 1662…pedestal, 1564a, 1564b, 1564c, 1564d, 1564e, 1664…protrusion, 1700…optical transmitting device, 1704…light source, 1706…modulation signal generating unit, 1708…modulation data generating unit. DETAILED DESCRIPTION

[0049] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0050] [First embodiment]

[0051] First, a first embodiment of the present invention will be described. Figure 1 and Figure 2 : is a diagram showing the structure of the optical modulator of the first embodiment of the present invention. Figure 1 、 Figure 2 They are respectively a top view and a side view of the optical modulator 100 .

[0052] 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 .

[0053] The optical modulator 102 includes, for example, four Mach-Zehnder optical waveguides disposed on an LN substrate. Four signal electrodes 112a, 112b, 112c, and 112d are provided on the four Mach-Zehnder optical waveguides to modulate the light waves propagating through the Mach-Zehnder optical waveguides. As is known in the art, a ground electrode (on the surface of the LN substrate of the optical modulator 102) is provided on each of the four signal electrodes 112a, 112b, 112c, and 112d, for example, to form a coplanar waveguide (CPW). Figure 1 Not shown in the figure. Figure 3 122a, 122b, 122c, 122d, 122e) shown in FIG.

[0054] Specifically, the ground electrodes are arranged on the LN substrate surface 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 predetermined characteristic impedance at a predetermined operating frequency.

[0055] The optical modulator 102 is a DP-QPSK modulator that performs optical modulation at, for example, 400 Gb / s. Four high-frequency electrical signals (modulation signals) are input to four signal electrodes 112a, 112b, 112c, and 112d. These electrical signals coordinate to control the propagation of light waves in the four Mach-Zehnder optical waveguides, thereby performing 400 Gb / s DP-QPSK modulation as a whole.

[0056] The two lights output from the light modulator 102 are polarization-combined by, for example, a lens system (not shown), and are guided to the outside of the housing 104 via the output optical fiber 110 .

[0057] The housing 104 is composed of a shell 114a and a cover 114b that fix the light modulating element 102. Figure 1In the figure, only a portion of cover 114b is shown on the left. However, cover 114b actually covers the entire box-shaped housing 114a, airtightly sealing the interior of housing 104. Housing 114a is made of metal or, for example, gold-plated ceramic, and functions electrically as a conductor. Housing 104 is typically provided with multiple pins for DC control, etc., but these are omitted in this figure.

[0058] The housing 114a is provided with electrical connectors 116a, 116b, 116c, and 116d having signal input terminals 124a, 124b, 124c, and 124d for inputting high-frequency electrical signals to be applied to the signal electrodes 112a, 112b, 112c, and 112d of the optical modulator 102. Furthermore, a relay substrate 118 is housed within the housing 104. As described later, signal conductor patterns 330a, 330b, 330c, 330d and ground conductor patterns 340a, 340b, 340c, 340d, 340e are formed on the relay substrate 118 for electrically connecting the signal input terminals 124a, 124b, 124c, 124d to the signal electrodes 112a, 112b, 112c, 112d of the optical modulator 102, respectively.

[0059] The electrical signals input from the signal input terminals 124a, 124b, 124c, and 124d are input to one end of each of the signal electrodes 112a, 112b, 112c, and 112d of the optical modulator 102 via the relay substrate 118. The other ends of the signal electrodes 112a, 112b, 112c, and 112d are terminated by a terminator 120 having a predetermined impedance. As a result, the electrical signals input to one end of each of the signal electrodes 112a, 112b, 112c, and 112d propagate as traveling waves within the signal electrodes 112a, 112b, 112c, and 112d.

[0060] Electrical connectors 116a, 116b, 116c, and 116d are each a socket of a push-on coaxial connector, for example. The cylindrical grounding conductors of these electrical connectors 116a, 116b, 116c, and 116d are electrically connected to and fixed to housing 114a. Therefore, housing 114a corresponds to a structure connected to ground potential. Furthermore, signal input terminals 124a, 124b, 124c, and 124d are each composed of a central conductor (core wire) extending along the centerline of the cylindrical grounding conductor within the connector sockets of, for example, electrical connectors 116a, 116b, 116c, and 116d.

[0061] Figure 3 yes Figure 1The partial detail diagram of the A portion in FIG is a diagram showing the structure of the relay substrate 118 and its surroundings. Figure 4 This is a perspective view of the front surface of the relay substrate 118 as viewed from the side where the signal input terminal 124a and the like are arranged. Figure 5 This is a perspective view of the back side (ie, the side facing the front side) of the relay substrate 118 from the side where the signal input terminal 124a and the like are configured. Figure 6 This is a perspective view of the front surface of the relay substrate alone as viewed from the side where the light modulation element 102 is arranged.

[0062] On the front side of the relay substrate 118 ( Figure 1 and Figure 3 Signal conductor patterns 330a, 330b, 330c, 330d and ground conductor patterns 340a, 340b, 340c, 340d, 340e are provided (see the diagram in the figure).

[0063] The above-mentioned grounding conductor patterns 340a, 340b, 340c, 340d, and 340e are arranged to clamp the signal conductor patterns 330a, 330b, 330c, and 330d respectively within the surface of the front surface of the relay substrate 118, thereby, the signal conductor patterns 330a, 330b, 330c, and 330d respectively form coplanar lines together with the grounding conductor patterns 340a, 340b, 340c, 340d, and 340e.

[0064] like Figure 3 As shown, the signal electrodes 112a, 112b, 112c, and 112d of the optical modulator 102 are electrically connected to one end of the signal conductor patterns 330a, 330b, 330c, and 330d of the relay substrate 118 by wire bonding using, for example, conductor wires 126. The conductor wires 126 may be, for example, gold wires.

[0065] Furthermore, in the optical modulator 102, the ground electrodes 122a, 122b, 122c, 122d, and 122e, which form a coplanar line together with the signal electrodes 112a, 112b, 112c, and 112d, are electrically connected to one end of the ground conductor patterns 340a, 340b, 340c, 340d, and 340e of the relay substrate 118, respectively, by wire bonding using, for example, the conductor wire 126, as described above. The wire bonding using the conductor wire 126 described above is merely an example and is not intended to be limiting. In addition to wire bonding using the conductor wire 126, ribbon bonding using, for example, a conductor ribbon such as a gold ribbon may also be used.

[0066] In addition, if Figure 3 、 Figure 4As shown, signal input terminals 124a, 124b, 124c, and 124d of electrical connectors 116a, 116b, 116c, and 116d disposed on housing 114a of case 104 are respectively fixed and electrically connected to the other ends of signal conductor patterns 330a, 330b, 330c, and 330d of relay substrate 118. The above-mentioned fixing and electrical connection can be performed using, for example, solder, brazing material, or a conductive adhesive.

[0067] In particular, if Figure 4 and Figure 5 As shown, in the relay substrate 118 of the optical modulator 100 of this embodiment, input side ground conductor patterns 442a, 442b, 442c, 442d, and 442e are provided on a side 418b (hereinafter referred to as the input side side 418b) of the relay substrate 118, which is a side on which the electrical signal from the signal input terminals 124a, 124b, 124c, and 124d is input to the signal conductor patterns 330a, 330b, 330c, and 330d.

[0068] Specifically, the input side ground conductor patterns 442a, 442b, 442c, 442d, and 442e are formed to extend from the front-side ground conductor patterns 340a, 340b, 340c, 340d, and 340e of the relay substrate 118, respectively, and to connect to the rear-side ground conductor pattern 542 (or to extend from the rear-side ground conductor pattern 542 and to connect to the front-side ground conductor patterns 340a, 340b, 340c, 340d, and 340e, respectively). Furthermore, the input side ground conductor patterns 442a, 442b, 442c, 442d, and 442e are formed to have, for example, the same width as the ground conductor patterns 340a, 340b, 340c, 340d, and 340e on the signal input side 418a.

[0069] The back side of the relay substrate 118 ( Figure 5 The surface on which the ground conductor pattern 542 is formed (shown in FIG) is fixed to the housing 114a, and the ground conductor pattern 542 on the back side is electrically connected to the housing 114a. In addition, in the relay substrate 118, the input side surface 418b is connected to the inner wall surface 314 ( Figure 3 ) abuts, and the input side ground conductor patterns 442a, 442b, 442c, 442d, and 442e provided on the input side side 418b are electrically connected to the inner wall surface 314 of the shell 114a as the above-mentioned structure (refer to Figure 3 、 Figure 4The above-mentioned fixing and electrical connection between the above-mentioned relay substrate 118 and the housing 114a can be performed by, for example, solder, brazing material or conductive adhesive.

[0070] In addition, if Figure 6 As shown, in this embodiment, a conductor is not provided on a side surface 418d (referred to as output side surface 418d) of the relay substrate 118, which is a side on which an electric signal is output from the signal conductor patterns 330a, 330b, 330c, 330d to the signal electrodes 112a, 112b, 112c, 112d of the optical modulator 102 (referred to as a signal output side 418c). Figure 6 However, this is just an example, and a ground conductor pattern may be formed on the output side surface 418d so as to extend from the ground conductor patterns 340a, 340b, 340c, 340d, and 340e on the front surface and / or the ground conductor pattern 542 on the back surface of each relay substrate 118.

[0071] The optical modulator 100 having the above-described structure has input side surface ground conductor patterns 442a, 442b, 442c, and 442d formed on the input side surface 418b of the relay substrate 118. These patterns extend from the front surface ground conductor patterns 340a, 340b, 340c, 340d, and 340e and the back surface ground conductor pattern 542 of the relay substrate 118, respectively. Consequently, spatial radiation of high-frequency electrical signals due to reflections of these signals generated near the signal input side 418a, or leakage of these signals due to such spatial radiation, is effectively suppressed. Furthermore, the propagation of high-frequency electrical signals radiated or leaked from the signal input side 418a toward the optical modulator 102 is suppressed.

[0072] Furthermore, the extended input side ground conductor pattern 442a and the like can cause molten solder to irregularly seep out. The solder conforms to the shape of the extended input side ground conductor pattern 442a and the like through metal reaction and surface tension, thereby being fixed to the side surface of the relay substrate 118. This can suppress impedance variations caused by manufacturing variations and achieve stable high-frequency electrical signal propagation.

[0073] Specifically, when a high-frequency electrical signal output from a coaxial connector is input to a coplanar line formed by a conductor pattern on a relay substrate, the propagation mode of the high-frequency electrical signal changes from a coaxial mode to a coplanar mode. Consequently, reflection, radiation, and leakage of the high-frequency electrical signal are likely to occur near the signal input side of the relay substrate. In contrast, in optical modulator 100, grounding is enhanced by input side ground conductor patterns 442a, 442b, 442c, and 442d formed on the input-side side surface 418b, which is defined by the signal input side 418a. This suppresses radiation and leakage of high-frequency electrical signals near signal input side 418a. Furthermore, input side ground conductor patterns 442a, 442b, 442c, and 442d act as a barrier, preventing high-frequency electrical signals radiated or leaked near signal input side 418a from propagating within the relay substrate 118 and reaching optical modulator 102.

[0074] As a result, in the optical modulator 100, even when the transmission rate exceeds 400 Gb / s, for example, the effects of reflection, radiation, leakage, etc. of electrical signals generated in or around the relay substrate 118 can be effectively reduced, thereby achieving good optical modulation characteristics.

[0075] Next, a modification of the relay substrate 118 that can be used in the optical modulator 100 according to the first embodiment will be described.

[0076] <First Modification>

[0077] Figure 7 This is a diagram showing the structure of a relay substrate 718 according to a first modification. Figure 1 In the optical modulator 100 shown in FIG. 1 , the relay substrate 118 is used instead. Figure 7 In, with Figure 4 The same structural elements as those of the relay substrate 118 shown in FIG. Figure 4 The same symbols as in the above are used. Figure 4 In addition, Figure 7 Only the relay substrate 718 is shown. Figure 4 The electrical connectors 116a, 116b, 116c, 116d and the signal input terminals 124a, 124b, 124c, 124d shown for reference are not shown. Figure 5 The back surface of the relay substrate 118 shown in FIG is similarly provided with a ground conductor pattern 542. In addition, the structure of the output side surface 418d of the relay substrate 718 is the same as that in FIG. Figure 6 The relay substrate 118 shown in FIG.

[0078] exist Figure 7 The relay substrate 718 shown in FIG. Figure 4 The relay substrate 118 has the same structure as shown in the figure, but has the following differences: input grounding recesses 750a, 750b, 750c, 750d, and 750e are provided on the input side surface 418b, and a portion of each input side grounding conductor pattern 442a, 442b, 442c, 442d, and 442e is provided in the input grounding recesses 750a, 750b, 750c, 750d, and 750e.

[0079] In this modification, the input grounding recesses 750a, 750b, 750c, 750d, and 750e extend from the front surface (the surface provided with the ground conductor pattern 340a and the like) of the relay substrate 718 to the back surface opposite to the front surface.

[0080] Generally, when the back side of the relay substrate is fixed to the housing of the optical modulator by solder, etc., the adjustment accuracy of the solder amount is limited. It is difficult to adjust the solder amount with high precision so that the solder does not overflow outside the relay substrate and is applied to the entire back side of the relay substrate.

[0081] In the relay substrate 718 of this modified example, the input-side side surface 418b includes input grounding recesses 750a, 750b, 750c, 750d, and 750e, in which portions of the input-side grounding conductor patterns 442a, 442b, 442c, 442d, and 442e are formed. Therefore, when the grounding conductor pattern 542 on the rear surface of the relay substrate 718 is secured to the housing 114a using solder or the like, solder overflowing from the rear surface flows into the input grounding recesses 750a, 750b, 750c, 750d, and 750e and accumulates within the input grounding recesses 750a and the like.

[0082] Therefore, in the relay substrate 718, the optical modulator 100 can be manufactured reproducibly and stably, ensuring that the solder connection to the housing 114a on the rear surface of the relay substrate 718 is excellent, in other words, that the electrical connection is excellent. Furthermore, even if solder overflows from the rear surface, the presence of the input ground recesses 750a, 750b, 750c, 750d, and 750e and the retention of the overflowed solder within the input ground recess 750a improve the conductivity between the front and rear ground conductor patterns. This allows for more effective grounding near the signal input side 418a than in the relay substrate 118. Consequently, the relay substrate 718 can more effectively suppress reflection, radiation, and leakage of high-frequency electrical signals than in the relay substrate 118, and can prevent such radiated or leaked high-frequency electrical signals from propagating through the interior of the relay substrate 718 toward the optical modulator 102.

[0083] The above-described effects are also achieved in the case where the relay substrate 718 and the housing 114 a are fixed to each other using solder or a conductive adhesive, in addition to the case where the relay substrate 718 and the housing 114 a are fixed to each other using solder.

[0084] Furthermore, in this variation, similar to the case of the relay substrate 118 described above, the extended input side ground conductor pattern 442a and the like can be fixed to the side surface of the relay substrate 718 by allowing molten solder to irregularly seep out and conform to the shape of the extended input side ground conductor pattern 442a and the like through metal reaction and surface tension. This suppresses impedance variations caused by manufacturing variations, enabling stable high-frequency electrical signal propagation.

[0085] <Second Modification>

[0086] Figure 8 This is a diagram showing the structure of a relay substrate 818 according to a second modification. Figure 1 In the optical modulator 100 shown in FIG. 1 , the relay substrate 118 is used instead. Figure 8 In, with Figure 4 The same structural elements as those of the relay substrate 118 shown in FIG. Figure 4 The same symbols as in the above are used. Figure 4 In addition, Figure 8 Only the relay substrate 818 is shown. Figure 4 The electrical connectors 116a, 116b, 116c, 116d and the signal input terminals 124a, 124b, 124c, 124d shown as reference are not shown. Figure 5 The back surface of the relay substrate 118 shown in FIG is similarly provided with a ground conductor pattern 542. In addition, the structure of the output side surface 418d of the relay substrate 818 is similar to that of FIG. Figure 6 The relay substrate 118 shown in FIG.

[0087] Although Figure 8 The relay substrate 818 shown in FIG. Figure 4 The structure of the relay substrate 118 shown in FIG is the same as that of the relay substrate 118 shown in FIG, but the following difference is that the input grounding recesses 850a, 850b, 850c, 850d, and 850e are provided on the input side surface 418b. In addition, although the input grounding recesses 850a, 850b, 850c, 850d, and 850e have the same Figure 7The structure is the same as the input grounding recess 750a of the relay substrate 718 shown in the figure, but it extends from the back surface opposite to the front surface of the relay substrate 818 (the surface provided with the grounding conductor pattern 340a, etc.) to the middle of the thickness of the relay substrate 818, and does not extend to the above-mentioned front surface, which is different from the input grounding recess 750a, etc.

[0088] Furthermore, parts of the input side-surface ground conductor patterns 442a, 442b, 442c, and 442d are provided in the input grounding recesses 850a, 850b, 850c, 850d, and 850e, respectively.

[0089] The relay substrate 818 having the above-mentioned structure is similar to the relay substrate 718 of the first variant. When the grounding conductor pattern 542 on the back side of the relay substrate 818 is fixed to the shell 114a by solder, etc., the solder overflowing from the back side flows into the input grounding recesses 850a, 850b, 850c, 850d, and 850e, and is retained inside the input grounding recesses 850a, etc.

[0090] Therefore, in the relay substrate 818, similarly to the relay substrate 718, the optical modulator 100 can be manufactured stably and reproducibly by ensuring that the solder connection between the back surface of the relay substrate 818 and the housing 114a is good, in other words, the electrical connection is good. Figure 7 In a case where the amount of overflowed solder is small, the above-mentioned effect can be achieved by the input grounding recesses 850a, 850b, 850c, 850d, and 850e extending to the middle in the thickness direction, as in the relay substrate 818.

[0091] The relay substrate 818 is similar to the relay substrate 718 in that it has input grounding recesses 850a, 850b, 850c, 850d, and 850e, and the overflowed solder is retained in the input grounding recess 850a and the like. Figure 4 The grounding near the signal input side 418a can be strengthened more effectively than the relay substrate 118 of FIG. Figure 4 Compared with the relay substrate 118 , the relay substrate 818 can more effectively suppress the reflection, radiation, leakage, etc. of the high-frequency electrical signal, and suppress the radiation or leakage of the high-frequency electrical signal from propagating toward the optical modulation element 102 through the interior of the relay substrate 818 .

[0092] The above-mentioned effects are similar to those of the first modification example, and can be achieved even when the relay substrate 818 and the housing 114a are fixed by solder or a conductive adhesive, in addition to the case where the solder is used.

[0093] Furthermore, in this variation, similar to the case of the relay substrate 118 described above, the extended input side ground conductor pattern 442a and the like can cause molten solder to irregularly seep out. The solder conforms to the shape of the extended input side ground conductor pattern 442a and the like through metal reaction and surface tension, and adheres to the side surface of the relay substrate 818. This can suppress impedance variations caused by manufacturing variations, and achieve stable high-frequency electrical signal propagation.

[0094] <Third Modification>

[0095] Figure 9 1 is a diagram showing the structure of a relay substrate 918 according to a third modification. Figure 7 Similarly, the relay substrate 718 shown in Figure 1 In the optical modulator 100 shown in FIG. 1 , the relay substrate 118 is used instead. Figure 9 Middle pair and Figure 7 The same components as those of the relay substrate 718 shown in FIG. Figure 7 The same symbols as in the above are used. Figure 7 In addition, the structure of the back side of the relay substrate 918 is the same as that of Figure 5 The back surface of the relay substrate 118 shown in FIG is similarly provided with a ground conductor pattern 542. In addition, the structure of the output side surface 418d of the relay substrate 918 is similar to that of FIG. Figure 6 The relay substrate 118 shown in FIG.

[0096] Figure 9 The relay substrate 918 shown in FIG has Figure 7 , but differs in that side signal conductor patterns 952a, 952b, 952c, and 952d are provided on input-side side surface 418b, extending from front-side signal conductor patterns 330a, 330b, 330c, and 330d, respectively. Furthermore, relay substrate 918 differs from relay substrate 718 in that signal recesses 954a, 954b, 954c, and 954d are provided on input-side side surface 418b, extending from the front surface but not to the rear surface.

[0097] In this variation, the side signal conductor patterns 952a, 952b, 952c, and 952d each have a width substantially the same as the width of the signal conductor patterns 330a, 330b, 330c, and 330d on the signal input side 418a. Furthermore, portions of the side signal conductor patterns 952a, 952b, 952c, and 952d are located within the inner side surfaces of the signal recesses 954a, 954b, 954c, and 954d, respectively.

[0098] Figure 10 yes Figure 9 The partial detail diagram of the C portion of FIG is a diagram showing the relationship between the signal conductor pattern 330a, the side signal conductor pattern 952a and the signal recess 954a. The side signal conductor pattern 952a has the same width as the width of the signal conductor pattern 330a in the signal input side 418a, and a portion thereof is provided on the inner side of the signal recess 954a. In addition, the respective corresponding relationships between the other signal conductor patterns 330b, 330c, 330d and the side signal conductor patterns 952b, 952c, 952d and the signal recesses 954b, 954c, 954d are also the same. Figure 10 The relationship between the signal conductor pattern 330a, the side signal conductor pattern 952a, and the signal recess 954a shown in FIG.

[0099] Since the relay substrate 918 having the above-described structure includes the input grounding recesses 750a, 750b, 750c, 750d, and 750e, similarly to the relay substrate 718 of the first modified example, the optical modulator 100 can be manufactured with good reproducibility and stability, ensuring good electrical connection to the housing 114a on the rear surface of the relay substrate 918. Furthermore, for the same reason, similarly to the relay substrate 718, the relay substrate 918 can more effectively strengthen the grounding near the signal input side 418a than the relay substrate 118, thereby suppressing reflection, radiation, and leakage of high-frequency electrical signals and preventing such radiated or leaked high-frequency electrical signals from propagating through the interior of the relay substrate 918 toward the optical modulator 102.

[0100] Furthermore, in the relay substrate 918, side signal conductor patterns 952a, 952b, 952c, 952d extending from the front signal conductor patterns 330a, 330b, 330c, 330d are provided on the input side side 418b, and a portion of each of them is provided in a signal recess 954a, 954b, 954c, 954d extending from the front but not extending to the back.

[0101] Therefore, in relay substrate 918, when signal input terminals 124a, 124b, 124c, and 124d are connected to signal conductor patterns 330a, 330b, 330c, and 330d, respectively, using solder, even if there is a difference in the amount of solder, the excess solder will flow through side signal conductor patterns 952a, 952b, 952c, and 952d and accumulate in signal recesses 954a, 954b, 954c, and 954d. Therefore, in relay substrate 918, more suitable solder connections can be achieved at the connection portions between signal input terminals 124a, 124b, 124c, and 124d and signal conductor patterns 330a, 330b, 330c, and 330d, compared to a case without such signal recesses, and connections can be made uniformly at each connection portion. As a result, impedance variations between the connection portions can be suppressed, and good optical modulation characteristics can be stably ensured.

[0102] Furthermore, in this variation, similar to the case of the relay substrate 118 described above, the extended input side ground conductor pattern 442a and the like can cause molten solder to irregularly seep out. The solder conforms to the shape of the extended input side ground conductor pattern 442a and the like through metal reaction and surface tension, and adheres to the side surface of the relay substrate 918. This can suppress impedance variations caused by manufacturing variations and achieve stable high-frequency electrical signal propagation.

[0103] <Fourth Modification>

[0104] Figure 11 、 Figure 12 1118 is a diagram showing the structure of a relay substrate 1118 according to a fourth modification. Figure 9 Similarly, the relay substrate 918 shown in Figure 1 In the optical modulator 100 shown in FIG, the relay substrate 118 is used instead. Figure 11 This is a perspective view of the front surface of the relay substrate 1118 as viewed from the side where the signal input terminal 124a and the like are arranged. Figure 12 This is a perspective view of the front surface of the relay substrate 1118 alone as viewed from the side where the light modulation element 102 is arranged.

[0105] exist Figure 11 In, with Figure 9 The same structural elements as those of the relay substrate 918 shown in FIG. Figure 9 The same symbols as in the above Figure 9 In addition, the structure of the back side of the relay substrate 1118 is the same as Figure 5 Similarly, a ground conductor pattern 542 is provided on the back surface of the relay substrate 118 shown in FIG.

[0106] Figure 11 、 Figure 12 The relay substrate 1118 shown in FIG has Figure 9 The relay substrate 918 shown in FIG has the same structure, but the following points are different: Figure 12 As shown, output side surface 418d is provided with output side surface ground conductor patterns 1250a, 1250b, 1250c, 1250d, and 1250e, respectively, extending from the front surface ground conductor patterns 340a, 340b, 340c, 340d, and 340e to the rear surface. Furthermore, unlike relay substrate 918, relay substrate 1118 is provided with output ground recesses 1254a, 1254b, 1254c, 1254d, and 1254e, extending from the front surface to the rear surface, on output side surface 418d.

[0107] In this variation, output-side ground conductor patterns 1250a, 1250b, 1250c, 1250d, and 1250e have widths equal to those of ground conductor patterns 340a, 340b, 340c, 340d, and 340e on signal output side 418c. Furthermore, portions of output-side ground conductor patterns 1250a, 1250b, 1250c, 1250d, and 1250e are located within the inner surfaces of output ground recesses 1254a, 1254b, 1254c, 1254d, and 1254e, respectively.

[0108] In the relay substrate 1118 having the above-mentioned structure, since the relay substrate 1118 has the same structure as that in the third modification, Figure 9 , and thus exhibits the same effects as those of the relay substrate 918 described above. Furthermore, in relay substrate 1118, when a large amount of solder, for example, is used to secure relay substrate 1118 to housing 114a, solder overflowing from relay substrate 1118 flows into output side ground conductor patterns 1250a, 1250b, 1250c, 1250d, and 1250e within output ground recesses 1254a, 1254b, 1254c, 1254d, and 1254e and remains within these output ground recesses 1254a, 1254b, 1254c, 1254d, and 1254e. This significantly relaxes the accuracy required for adjusting the amount of solder.

[0109] Furthermore, since the solder overflows into the grounding recess on both the signal input side 418a and the signal output side 418c, the amount of overflowed solder is more symmetrical. This reduces uneven distribution of stress in the relay substrate 1118 caused by solidification of the solder, and improves reliability by reducing peeling and cracking of the relay substrate 1118.

[0110] In addition, by having output side grounding conductor patterns 1250a, 1250b, 1250c, 1250d, and 1250e, and by having the above-mentioned overflowed soft solder retained inside the output grounding recesses 1254a, 1254b, 1254c, 1254d, and 1254e, the high-frequency electrical signal radiated or leaked from the vicinity of the signal input edge 418a can be more effectively suppressed from reaching the optical modulator 102 compared to the relay substrate 118.

[0111] Here, in relay substrate 1118, similar to relay substrate 118, signal conductor patterns 330a, 330b, 330c, and 330d, together with ground conductor patterns 340a, 340b, 340c, 340d, and 340e, respectively, form a coplanar line. Therefore, on signal input side 418a, where signal input terminal 124a and the like are arranged, the propagation mode of the high-frequency electrical signal input from signal input terminal 124a and the like is converted from a coaxial mode to a coplanar mode. In contrast, on signal output side 418c, where electrical signals are output to optical modulator 102, the high-frequency electrical signal in the coplanar mode propagating through relay substrate 1118 undergoes no mode conversion and is output to signal electrodes 112a, 112b, 112c, and 112d forming the coplanar line on optical modulator 102.

[0112] Therefore, compared with the signal input side 418a, reflection, radiation, leakage, etc. of high-frequency electrical signals are less likely to occur at the signal output side 418c, and the output grounding recess 1254a set on the output side surface 418d can be narrowed compared with the input grounding recess 750a set on the input side surface 418b.

[0113] In this modification, the output grounding recess 1254a provided on the output side surface 418d has an opening width narrowed to about half that of the input grounding recess 750a provided on the input side surface 418b.

[0114] Furthermore, in this variation, similar to the case of the relay substrate 118 described above, the extended input side ground conductor pattern 442a and the like can cause molten solder that has irregularly seeped out to conform to the shape of the extended input side ground conductor pattern 442a and the like through metal reaction and surface tension, thereby adhering to the side surface of the relay substrate 1118. This can suppress impedance variations caused by manufacturing variations, thereby achieving stable high-frequency electrical signal propagation.

[0115] [Second embodiment]

[0116] Next, an optical modulator according to a second embodiment of the present invention will be described. Figure 131 is a diagram showing the structure of the optical modulator 1300 of this embodiment. Figure 13 In the embodiment, the same components as those of the optical modulator 100 of the first embodiment are used. Figure 1 The same symbols and reference to the above Figure 1 Description.

[0117] The optical modulator 1300 has the same structure as the optical modulator 100, but includes a relay substrate 718 in place of the relay substrate 118. The relay substrate 718 is fixed to and electrically connected to the housing 114a of the housing 104 via a base 1360, which is a structure separate from the housing 104. The use of the relay substrate 718 as the relay substrate in the optical modulator 1300 is merely illustrative; the relay substrates 118, 818, 918, or 1118 may also be used in place of the relay substrate 718.

[0118] In optical modulator 1300, housing 104, which is composed of housing 114a and cover 114b, is replaced with housing 1304, which is composed of housing 1314a and cover 1314b. Housing 1314a has the same structure as housing 114a, but differs in that it has a slightly larger width than housing 114a to ensure space for accommodating base 1360. However, it can be made the same width as housing 114a by adjusting the design of the optical element and the interior of the housing.

[0119] Furthermore, the connection between the signal conductor pattern 330 a and the like on the relay substrate 718 and the signal input terminal 124 a and the like in the optical modulator 1300 can be performed using, for example, solder, brazing material, or a conductive adhesive, similarly to the optical modulator 100. Furthermore, the connection between the signal conductor pattern 330 a and the like and the ground conductor pattern 340 a and the like on the relay substrate 718 and the signal electrode 112 a and the like and the ground electrode 122 a and the like on the optical modulator 102 can be performed using, for example, the conductor wire 126 by wire bonding, similarly to the optical modulator 100.

[0120] Figure 14 yes Figure 13 In the relay substrate 718 , the back surface thereof (more specifically, the ground conductor pattern 542 provided on the back surface) is fixed and electrically connected to the interior of the housing 1314 a via the base 1360 .

[0121] Figure 1513. It is a diagram showing the structure of the base 1360 and the positional relationship between the relay substrate 718 fixed to the base 1360 and the base 1360. The base 1360 is composed of a seat portion 1562 that fixes the back of the relay substrate 718 and protrusions 1564a, 1564b, 1564c, 1564d, and 1564e that are provided along one side and extend in the longitudinal direction of the seat portion 1562. The relay substrate 718 is arranged and fixed at the position shown by the dotted line in the figure on the base 1360 and is electrically connected (hereinafter referred to as "fixed" or "fixed"). At this time, in particular, the input side side 418b of the relay substrate 718 (which is Figure 15 The surface opposite to the output side side surface 418d shown in the figure abuts against the protrusion 1564a of the base 1360, and the input side ground conductor pattern 442a provided on the input side side surface 418b is electrically connected to the protrusion 1564a.

[0122] Protrusions 1564a, 1564b, 1564c, 1564d, and 1564e are spaced apart at predetermined intervals, forming four slits between them. In this embodiment, the spacing between these four slits is preferably set to the same distance as the spacing between signal conductor pattern 330a and the like on relay substrate 718. However, at least one of the four slits may be spaced at a different distance. Relay substrate 718 connects signal input terminal 124a and the like disposed in housing 1314a via these slits.

[0123] For example, the relay substrate 718 is fixed to the base 1360 and then fixed in the housing 1314a. The base 1360 is made of metal, for example, and is connected to the ground potential via the housing 1314a.

[0124] Typically, the relay substrate used within an optical modulator is often made of ceramic. In contrast, the outer casing of an optical modulator is made of a material different from ceramic, such as KOVAR (Kovar alloy). Therefore, when the ambient temperature fluctuates, the difference in linear expansion coefficients between the outer casing and the relay substrate can cause repeated stress at the connection between the relay substrate and the outer casing, potentially leading to cracks or delamination in the connection.

[0125] In the optical modulator 1300 having the above-described structure, the relay substrate 718 is secured to the housing 1314a of the casing 104 via a base 1360 that is separate from the housing 1314a. Therefore, by appropriately selecting the material used for the base 1360, the occurrence of the aforementioned problems such as cracks and peeling can be effectively avoided, thereby improving long-term reliability. Furthermore, the ability to appropriately select the material for the base 1360 as described above increases the degree of freedom in material selection and structural design for the relay substrate 718 and the housing 1314a.

[0126] Furthermore, compared to a solution in which the relay substrate is directly fixed to the housing by solder, etc., by pre-fixing it to a separate base, it is easier to more accurately manage the thermal uniformity and heat conduction during solder melting and fixing, thereby enabling more accurate solder fixing.

[0127] Furthermore, in this variation, similar to the case of the relay substrate 118 described above, the extended input side ground conductor pattern 442a and the like can allow molten solder that has irregularly seeped out to conform to the shape of the extended input side ground conductor pattern 442a and the like through metal reaction and surface tension, thereby adhering to the side surface of the relay substrate 718. This can suppress impedance variations caused by manufacturing variations, and achieve stable high-frequency electrical signal propagation.

[0128] In addition, as a modification of the base 1360, the following can be used in the optical modulator 1300: Figure 16 The simple shape of the base 1660 is shown. Figure 16 Unlike base 1360, base 1660 shown in FIG. has no slits and instead consists of a base portion 1662 and a protrusion 1664 extending along one side of base portion 1662. Relay substrate 718 is secured to, for example, base portion 1662 of base 1660 and then secured within housing 1314a. The height h of protrusion 1664 from the upper surface of base portion 1662 (as shown) is configured to be at least less than the thickness t of relay substrate 718 so that when signal conductor pattern 330a of relay substrate 718 and signal input terminal 124a are connected to each other, signal input terminal 124a and the like do not come into contact with protrusion 1664.

[0129] On the other hand, from the perspective of strengthening the grounding of the input-side side surface 418b of the relay substrate 718 and blocking radiated high-frequency electrical signals, it is desirable to ensure as large a contact area as possible between the input-side side surface 418b of the relay substrate 718 and the protrusion 1664. Therefore, it is desirable that the height h of the protrusion 1664 be greater than, for example, 1 / 2 of the thickness t of the relay substrate 718 (h>1 / 2t).

[0130] [Third embodiment]

[0131] Next, a third embodiment of the present invention will be described. This embodiment is an optical transmission device equipped with any of the optical modulators 100 of the first embodiment, the optical modulators 100 having the relay substrates 718, 818, 918, and 1118 according to the first to fourth modifications of the first embodiment, and the optical modulator 1300 of the second embodiment.

[0132] Figure 17 This diagram shows the configuration of an optical transmitter according to this embodiment. The optical transmitter 1700 includes an optical modulator 1702 , a light source 1704 for inputting light into the optical modulator 1702 , a modulation signal generator 1706 , and a modulation data generator 1708 .

[0133] The optical modulator 1702 may be any of the optical modulator 100 of the first embodiment, the optical modulator 100 including the relay substrates 718 , 818 , 918 , and 1118 of the first to fourth modifications of the first embodiment, and the optical modulator 1300 of the second embodiment.

[0134] The modulation data generation unit 1708 receives transmission data given from the outside, generates modulation data for transmitting the transmission data (for example, converts the transmission data into a prescribed data format or processed data), and outputs the generated modulation data to the modulation signal generation unit 1706.

[0135] The modulation signal generator 1706 is an electronic circuit (driver circuit) that outputs an electrical signal for causing the optical modulator 1702 to perform a modulation operation. Based on the modulation data output by the modulation data generator 1708, the modulation signal is generated as a high-frequency signal for causing the optical modulator 1702 to perform an optical modulation operation in accordance with the modulation data, and is input to the optical modulator 1702. This 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 1702, i.e., the optical modulator 100.

[0136] 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 1702, i.e., the optical modulator 100, to the signal conductor patterns 330a, 330b, 330c, 330d of the relay substrate 118, and are input to the signal electrodes 112a, 112b, 112c, 112d of the optical modulator element 102 via the above-mentioned signal conductor pattern 330a, etc.

[0137] Thus, the light output from the light source 1704 is modulated by, for example, DP-QPSK by the optical modulator 1702 , and becomes modulated light that is output from the optical transmitting apparatus 1700 .

[0138] In particular, in the present optical transmitting device 1700, since the optical modulator 100 of the first embodiment, the optical modulator 100 having the relay substrates 718, 818, 918, 1118 of the first to fourth variants of the first embodiment, and the optical modulator 1300 of the second embodiment are used as the optical modulator 1702, stable and good optical modulation characteristics can be ensured, and therefore stable and good transmission characteristics can be achieved.

[0139] In addition, the present invention is not limited to the configuration of the above-described embodiment, and can be implemented in various forms without departing from the spirit and scope of the present invention.

[0140] For example, in the above-described embodiment, input side surface ground conductor patterns 442a, 442b, 442c, 442d, and 442e are provided on the input side surface 418b of the relay substrate 118, etc., extending from the ground conductor patterns 340a, 340b, 340c, 340d, and 340e formed on the front surface to the ground conductor pattern on the rear surface, respectively. However, the present invention is not limited to this embodiment. From the perspective of ground reinforcement for the signal input side 418a of the relay substrate 118, etc., at least one of the input side surface ground conductor patterns 442a, 442b, 442c, 442d, and 442e may be formed to extend from at least one of the ground conductor patterns 340a, 340b, 340c, 340d, and 340e within a required range. Alternatively, from the above viewpoint, within the required range, at least one of the input side ground conductor patterns 442a, 442b, 442c, 442d, and 442e can be formed on the input side surface 418b, for example, by extending only from the ground conductor pattern 542 on the back side of the relay substrate 118, etc., and not extending to the signal input side 418a.

[0141] Similarly, in the relay substrate 1118 of the aforementioned embodiment, from the perspective of ground reinforcement for the signal output side 418c, at least one of the corresponding output side ground conductor patterns 1250a, 1250b, 1250c, 1250d, and 1250e may be formed on the output side 418d, extending from at least one of the ground conductor patterns 340a, 340b, 340c, 340d, and 340e, within a required range. Alternatively, from the aforementioned perspective, at least one of the output side ground conductor patterns 1250a, 1250b, 1250c, 1250d, and 1250e may be formed on the output side 418d, extending only from the ground conductor pattern 542 on the back surface of the relay substrate 1118, etc., and not extending to the signal output side 418c, within a required range.

[0142] Furthermore, in the relay substrate 1118 of the aforementioned embodiment, the widths of the output side ground conductor patterns 1250a, 1250b, 1250c, 1250d, and 1250e may be narrower than the widths of the ground conductor patterns 340a, 340b, 340c, 340d, and 340e on the signal output side 418c, within a desired range from the perspective of grounding enhancement of the signal output side 418c. Furthermore, from the aforementioned perspective, within a desired range from the perspective of grounding enhancement, at least a portion (or, in some cases, all) of each of the output side ground conductor patterns 1250a, 1250b, 1250c, 1250d, and 1250e may be disposed within (on the inner side of) the output grounding recesses 1254a, 1254b, 1254c, 1254d, and 1254e.

[0143] Furthermore, in the relay substrate 1118 in the above-described embodiment, the output grounding recesses 1254a, 1254b, 1254c, 1254d, and 1254e extend to both the front and back surfaces, but the present invention is not limited thereto. From the perspective of strengthening the grounding of the signal output side 418c, etc., the output grounding recesses 1254a, 1254b, 1254c, 1254d, and 1254e may also be formed to extend at least from the back surface (i.e., not necessarily to the signal output side 418c) within a desired range.

[0144] Furthermore, in the relay substrates 918 and 1118 of the above-described embodiments, side signal conductor patterns 952a, 952b, 952c, and 952d are provided, extending from the signal conductor patterns 330a, 330b, 330c, and 330d formed on the front surface, respectively. However, the present invention is not limited thereto. For example, depending on the accuracy of adjusting the amount of solder at the connection portions between the signal conductor patterns 330a, 330b, 330c, and 330d and the signal input terminals 124a, 124b, 124c, and 124d, a corresponding one of the side signal conductor patterns 952a, 952b, 952c, and 952d may be provided on the input-side side surface 418b, extending from at least one of the signal conductor patterns 330a, 330b, 330c, and 330d.

[0145] In the above-described embodiments, the input side surface ground conductor patterns 442a, 442b, 442c, 442d, and 442e extending from the ground conductor patterns 340a, 340b, 340c, 340d, and 340e in the relay substrates 718, 918, and 1118 have the same width as the ground conductor patterns 340a, 340b, 340c, 340d, and 340e on the signal input side 418a, and portions of each of these are located within (inner side surfaces of) the input ground recesses 750a, 750b, 750c, 750d, and 750e. However, the present invention is not limited thereto. The input side surface ground conductor patterns 442a, 442b, 442c, 442d, and 442e may also have a width narrower than the width of the ground conductor patterns 340a, 340b, 340c, 340d, and 340e. In addition, at least a portion of each of the input side grounding conductor patterns 442a, 442b, 442c, 442d, and 442e may be arranged inside (inner side surface) the input grounding recesses 750a, 750b, 750c, 750d, and 750e, or all of each of them may be arranged inside the input grounding recesses 750a, 750b, 750c, 750d, and 750e.

[0146] Similarly, in relay substrates 918 and 1118, the side signal conductor patterns 952a, 952b, 952c, and 952d may have widths narrower than the signal conductor patterns 330a, 330b, 330c, and 330d. Furthermore, at least a portion of each of the side signal conductor patterns 952a, 952b, 952c, and 952d may be disposed within (on the inner side surface of) the signal recesses 954a, 954b, 954c, and 954d, or the entire side signal conductor patterns 952a, 952b, 954c, and 954d may be disposed within the signal recesses 954a, 954b, 954c, and 954d.

[0147] Furthermore, in relay substrates 918 and 1118, side signal conductor patterns 952a and the like are provided simultaneously with signal recesses 954a and the like, but the present invention is not limited thereto. Alternatively, side signal conductor patterns 952a and the like may be provided on input-side side surface 418b without providing signal recesses 954a and the like. With this configuration, excess solder introduced into the connection portions between signal conductor patterns 330a, 330b, 330c, and 330d and signal input terminals 124a, 124b, 124c, and 124d remains on side signal conductor patterns 952a and the like and solidifies, allowing this excess solder to be removed from signal conductor patterns 330a, 330b, 330c, and 330d to a certain extent.

[0148] In the above embodiment, the signal input terminals 124a, 124b, 124c, and 124d are core wires or center conductors of the electrical connector 116a, etc. However, the present invention is not limited thereto. For example, the signal input terminals 124a, 124b, 124c, and 124d may be pins extending from the bottom surface of the housing 114a, etc.

[0149] As described above, the optical modulators 100 and 1300 include an optical modulator element 102 having a plurality of signal electrodes 112a and the like; a housing 104 and 1304 housing the optical modulator element 102; and a plurality of signal input terminals 124a and the like for inputting electrical signals applied to the respective signal electrodes 112a and the like. Furthermore, the optical modulators 100 and 1300 include a relay substrate 118 and the like, on which a plurality of signal conductor patterns 330a and the like, and a plurality of ground conductor patterns 340a and the like, are formed, each electrically connecting the respective signal input terminals 124a and the like to the respective signal electrodes 112a and the like. The relay substrate 118 and the like are housed within the housing 104 and the like, and have at least one input side surface ground conductor pattern 442a and the like extending from at least one ground conductor pattern 340a and the like formed on an input side surface 418b having a signal input side 418a on which electrical signals from the signal input terminals 124a and the like are input to the signal conductor patterns 330a and the like.

[0150] Through such a structure, since the grounding near the signal input edge 418a is strengthened by the input side grounding conductor pattern 442a, etc., even when the transmission rate exceeds 400 Gb / s, for example, the reflection, radiation, leakage, etc. of the electrical signal in the connection part between the signal input terminal 124a and the signal conductor pattern 330a, etc. can be effectively reduced, thereby achieving good optical modulation characteristics of the optical modulation element 102.

[0151] In addition, in the relay substrates 718, 818, 918, and 1118 that can be used in the optical modulator 100, input grounding recesses 750a, 850a, etc. are formed on the input side surface 418b, extending from the back surface opposite to the front surface of the relay substrate 118, etc. that forms the signal conductor pattern 330a, and at least a portion of each of the input side grounding conductor patterns 442a, etc. is arranged inside the input grounding recesses 750a, 850a, etc.

[0152] Through this structure, when the relay substrate 718, 818, 918, 1118 is fixed to the housing 114a of the optical modulator 100, etc. by solder, the solder overflowing from the relay substrate 718, 818, 918, 1118 is retained in the input grounding recess 750a, 850a, etc., so that an appropriate amount of solder can be used to fix the relay substrate 718, 818, 918, 1118 and the housing 114a, etc., thereby ensuring a good electrical connection (for example, a connection to the ground potential).

[0153] In the optical modulator 100 and the like, the input grounding recess 750a and the like of the relay substrate 718, 918, and 1118 extend to both the front and back surfaces, and the input side grounding conductor pattern 442a and the like are formed inside the input grounding recess 750a and the like.

[0154] With this structure, the relay substrates 718 , 918 , and 1118 can be mechanically unified and simple in the thickness direction, thereby enabling an economical configuration.

[0155] In the relay substrates 918 and 1118 that can be used in the optical modulator 100 , etc., at least one side surface signal conductor pattern 952 a or the like extending from at least one signal conductor pattern 330 a or the like is further formed on the input-side side surface 418 b .

[0156] Through this structure, the remaining soft solder between the signal conductor pattern 330a and the signal input terminal 124a can be guided to the side signal conductor pattern 952a, etc., so that the solder fixation of the signal conductor pattern 330a and the signal input terminal 124a can be performed with good reproducibility and uniformity.

[0157] In addition, in the relay substrates 918, 1118 used in the optical modulator 100, etc., a signal recess 954a, etc. is formed on the input side surface 418b, extending from the surface on which the signal conductor pattern 330a is formed, and at least a portion of each of the side signal conductor patterns 952a, etc. is formed inside the signal recess 954a, etc.

[0158] Through this structure, since the remaining soft solder between the signal conductor pattern 330a and the signal input terminal 124a can be induced and retained inside the signal recess 954a, etc., the solder fixation of the signal conductor pattern 330a and the signal input terminal 124a can be further reproducibly and uniformly performed.

[0159] In addition, in the relay substrate 1118 used in the optical modulator 100, etc., at least one output side ground conductor pattern 1250a, etc. extending from at least one ground conductor pattern 340a, etc. is formed on the output side side 418d having the signal output side 418c as a side for outputting electrical signals from the signal conductor pattern 330a, etc. to the signal electrode 112a, etc.

[0160] Through this structure, the grounding near the connection part between the signal conductor pattern 330a and the signal electrode 112a can be strengthened, and high-frequency noise propagating from the input side side 418b through the interior of the relay substrate 1118 can be prevented, thereby ensuring good optical modulation characteristics of the optical modulation element 102.

[0161] In addition, in the relay substrate 1118 used in the optical modulator 100, etc., an output grounding recess 1254a, etc. extending from the back side of the relay substrate 1118 is formed on the output side side 418d, and at least a portion of each of the output side grounding conductor patterns 1250a, etc. is arranged inside the output grounding recess 1254a, etc.

[0162] Through this structure, since the remaining solder between the relay substrate 1118 and the shell 114a can be induced and retained inside the output grounding recess 1254a, etc., the precision required for adjusting the solder amount can be relaxed, thereby making the electrical connection between the relay substrate 1118 and the shell 114a more stable.

[0163] In the optical modulator 100 , the signal input terminal 124 a and the signal conductor pattern 330 a are electrically connected via solder, brazing material, or a conductive adhesive, and the signal conductor pattern 330 a and the signal electrode 112 a are electrically connected via a conductor wire or a conductor tape.

[0164] With this structure, electrical connection between the signal input terminal 124 a and the signal conductor pattern 330 a and the signal electrode 112 a and the signal conductor pattern 330 a and the signal electrode 112 a can be easily performed without using a special method.

[0165] In addition, in the optical modulator 100, etc., the input side surface 418b of the relay substrate 118, etc. abuts against a structure connected to the ground potential, such as the shell 114a, etc., the base 1360, etc., and the input side ground conductor pattern 442a, etc. arranged on the input side surface 418b is electrically connected to the above-mentioned structure.

[0166] With this configuration, a uniform ground potential without potential distribution within the plane can be easily applied to the input side surface ground conductor pattern 442 a and the like.

[0167] The optical modulator 1300 includes a housing 1304 that houses the optical modulation element 102 and the relay substrate 718 . A base 1360 , which is the aforementioned structure, is connected to the ground potential via a case 1314 a of the housing 1304 .

[0168] With this structure, since the base 1360 as the above-mentioned structure is constructed separately from the housing 1304, the stress applied to the relay substrate 718 due to changes in ambient temperature can be alleviated by, for example, appropriately selecting the material of the base 1360 as the above-mentioned structure, thereby ensuring good long-term reliability.

[0169] In addition, in the optical modulator 100, the structure that the input side ground conductor pattern 442a of the input side side 418b of the relay substrate 118, etc. abuts is the housing 104 of the optical modulator 100 that accommodates the optical modulation element 102 and the relay substrate 118, etc., more specifically, the shell 114a that constitutes the housing 104.

[0170] With this structure, the same ground potential without potential distribution within the surface can be easily and directly applied to the input side surface ground conductor pattern 442 a and the like without using an additional component such as the base 1360 .

[0171] In addition, as another embodiment of the present invention, the optical transmitting device 1700 includes: an optical modulator 100 or 1300 including any one of the above-mentioned relay substrates 118, i.e., an optical modulator 1702; and an electronic circuit that outputs an electrical signal for causing the optical modulator 1702 to perform a modulation operation, such as a modulation signal generating unit 1706 and a modulation data generating unit 1708.

[0172] With this configuration, even in an optical transmission device where the transmission rate exceeds 400 Gb / s, for example, in order to drive the optical modulation element 102 , it is possible to achieve good optical modulation characteristics and thus good optical transmission characteristics.

Claims

1. An optical modulator comprising: A light modulation element having a plurality of signal electrodes; a housing for accommodating the light modulation element; a plurality of signal input terminals for inputting electrical signals to be applied to the respective signal electrodes; and The relay substrate is formed with a plurality of signal conductor patterns and a plurality of ground conductor patterns, wherein the plurality of signal conductor patterns electrically connect the respective signal input terminals with the respective signal electrodes, The relay substrate is housed inside the housing, and has at least one input side surface ground conductor pattern formed on a flat surface portion of an input side surface, the side of the side on which the electrical signal from the signal input terminal is input to the signal conductor pattern. The ground conductor pattern extends from at least one of the ground conductor patterns formed on the upper surface of the relay substrate and is connected to the ground conductor pattern formed on the back surface of the relay substrate. The relay substrate is fixed to the base portion of a structure having a base portion and a protrusion portion, wherein the structure is composed of the base portion to which the back surface of the relay substrate is fixed and the protrusion portion provided along one side extending in the longitudinal direction of the base portion. The input side surface of the relay substrate contacts the protrusion of the structure connected to the ground potential, and the input side surface ground conductor pattern provided on the input side surface is electrically connected to the structure. The signal input terminal and the signal conductor pattern are electrically connected via solder or a conductive adhesive.

2. The optical modulator according to claim 1, wherein An input grounding recess is formed on the input side surface, extending from the back surface of the relay substrate opposite to the front surface where the signal conductor pattern is formed, and at least a portion of the input side grounding conductor pattern is arranged inside the input grounding recess.

3. The optical modulator according to claim 2, wherein The input grounding recess extends to both the front surface and the rear surface, and the input side surface grounding conductor pattern is formed inside the input grounding recess.

4. The optical modulator according to any one of claims 1 to 3, wherein At least one side signal conductor pattern extending from at least one of the signal conductor patterns is further formed on the input side surface.

5. The optical modulator according to claim 4, wherein A signal recess is formed on the input-side side surface, extending from the surface on which the signal conductor pattern is formed. At least a portion of the side signal conductor pattern is formed inside the signal recess.

6. The optical modulator according to any one of claims 1 to 3, wherein: At least one output side surface ground conductor pattern extending from at least one ground conductor pattern is formed on an output side surface of the relay substrate having a side on which an electrical signal is output from the signal conductor pattern to the signal electrode.

7. The optical modulator according to claim 6, wherein An output grounding recess extending from the rear surface of the relay substrate is formed on the output-side side surface, and at least a portion of the output-side-surface grounding conductor pattern is provided inside the output grounding recess.

8. The optical modulator according to any one of claims 1 to 3, wherein: The signal conductor pattern and the signal electrode are electrically connected via a conductor wire or a conductor ribbon.

9. The optical modulator according to any one of claims 1 to 3, wherein: The structure is connected to a ground potential via the housing.

10. The optical modulator according to any one of claims 1 to 3, wherein The structure is the housing.

11. An optical transmission device comprising: The optical modulator according to any one of claims 1 to 10; and The electronic circuit outputs an electrical signal for causing the optical modulator to perform a modulation operation.

Images