Optical modulator and optical transmission device using the same

Abstract

The purpose of the present invention is to provide an optical modulator capable of suppressing short-circuiting of wiring or the like of a wiring substrate even when an electronic circuit element such as a drive circuit is disposed close to the wiring substrate. An optical modulator in which an optical modulation element and an electronic circuit element (4) for inputting a high-frequency signal to the optical modulation element are housed in a housing (1), the optical modulator being characterized in that the electronic circuit element (4) is bonded and fixed to a surface opposite to one surface of a block body (40) fixed to the one surface in the housing (1), and the electronic circuit element (4) being bonded and fixed to the other surface of the block body (40). The optical modulator is provided with a wiring substrate (3 (3 ')) which is disposed adjacent to the electronic circuit element (4) and fixed to the one surface, and which is provided with wiring electrically connected to the electronic circuit element (4) on a surface on the opposite side from the one surface, the wiring being electrically connected to the electronic circuit element (4) with respect to the one surface, and the wiring being electrically connected to the electronic circuit element (4) with respect to the one surface. The height (h1) of the block (40) to the surface on which the adhesive fixing is performed and the height (h2) of the wiring substrate (3 (3 ')) to the surface on which the wiring is provided are different from each other.

Description

Technical Field

[0001] The present invention relates to an optical modulator and an optical transmitting device using the optical modulator, and more particularly to an optical modulator in which an optical modulator element and an electronic circuit element for inputting a high-frequency signal to the optical modulator element are housed in a casing and an optical transmitting device using the optical modulator. Background Art

[0002] There is a demand for an optical modulator such as the recent HB-CDM (High Bandwidth Coherent Driver Modulator) that can achieve high-speed driving, low driving voltage, and miniaturization by housing an optical modulator element and electronic circuit elements such as a drive circuit for driving the optical modulator element in a housing.

[0003] Figure 1 This is an example of an optical modulator incorporating a driving circuit, and an optical modulation element 5 is disposed in a housing 1. The optical modulation element includes an optical waveguide made of a material having an electro-optical effect and a modulation electrode for applying an electric field to the optical waveguide to modulate a light wave propagating in the optical waveguide.

[0004] The light wave input to the optical modulator 5 is introduced into the housing 1 through the input collimator 9 connected to the optical fiber FB, and is incident on the optical modulator 5 through the optical block 8, the lens 7, etc. In addition, the light wave modulated by the optical modulator 5 is led out to the outside of the housing 1 through the optical block 8 having the lens 7 and the optical multiplexing and demultiplexing unit, and is incident on the optical fiber FB through the output collimator 10.

[0005] On the other hand, regarding the modulation signal input to the optical modulation element 5, the modulation signal generated outside the housing 1 is introduced into the housing, and is supplied to the drive circuit 4 via the wiring of the input substrate 2. The modulation signal is amplified by the drive circuit 4, and then supplied to the modulation electrode of the optical modulation element 5, and finally introduced to the terminal substrate 6.

[0006] The drive circuit is supplied with direct current (DC) power for driving the drive circuit. The DC power supplied from a DC power source located outside the housing 1 is supplied to the drive circuit 4 via the wiring board 3 (or 3 ′) in the housing.

[0007] Figure 2 express Figure 1 A cross-sectional view of the single-point dashed line A-A'. Figure 2The housing 1 has a cover (not shown) covering the upper side of the drawing, but it is omitted here. The driving circuit 4 is bonded to a block 40 fixed to the inner surface of the housing 1. The heat generated from the driving circuit 4 also affects the operation of the optical modulator, so it needs to be released to the outside of the housing. Therefore, the block 40 is made of a material with high thermal conductivity and acts as a heat sink. In addition, the adhesive that bonds the driving circuit 4 to the block 40 also uses a material with high thermal conductivity and electrical conductivity, such as Ag filler, solder paste, etc. In addition, in Patent Document 1, it is also proposed to use the optical modulator as one of the heat dissipation units of the electronic component.

[0008] On the other hand, wiring is exposed on the surface of the wiring substrate 3 (3') (the surface of the wiring substrate opposite to the surface fixed to the housing 1), and the electrode pad portion (the portion to be wire-bonded) of the wiring is bonded to the terminal of the drive circuit 4 via a wire (not shown) such as Au.

[0009] However, the drive circuit 4 is arranged close to the wiring substrate 3 (3'), and the height of the joint surface of the drive circuit 4 and the block 40 and the surface of the wiring substrate 3 are also configured to be substantially the same. Therefore, when the drive circuit 4 is bonded, the adhesive AD overflows from the joint surface and contacts the wiring substrate 3, which may cause the wiring arranged on the surface of the wiring substrate to short-circuit. As one method to eliminate this problem, the interval between the drive circuit 4 and the wiring substrate 3 can also be increased, but a new problem arises that the optical modulator cannot be fully miniaturized.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Publication No. 2019-207362

[0013] Patent Document 2: Japanese Patent Application Publication No. 2017-134241

[0014] Patent Document 3: Japanese Patent Application Publication No. 2022-144126

[0015] Patent Document 4: International Publication No. WO2023 / 053406 A1 Summary of the invention

[0016] Problems to be solved by the invention

[0017] The present invention aims to solve the above-mentioned problems and provide an optical modulator capable of preventing short circuits of wirings of a wiring board even when electronic circuit elements such as a drive circuit are arranged close to the wiring board. In addition, an optical transmission device using the optical modulator is provided.

[0018] Means for solving problems

[0019] In order to solve the above-mentioned problems, an optical modulator and an optical transmission device using the optical modulator according to the present invention have the following technical features.

[0020] (1) An optical modulator that houses an optical modulator element and an electronic circuit element that inputs a high-frequency signal to the optical modulator element in a housing, wherein the electronic circuit element is adhesively fixed to a surface of a block on the side opposite to a surface, the block is fixed to the one surface in the housing, the optical modulator has a wiring substrate that is arranged adjacent to the electronic circuit element and fixed to the one surface, and has wiring electrically connected to the electronic circuit element on the surface of the wiring substrate on the side opposite to the one surface, and with the one surface as a reference, the height (h1) of the block to the surface to which the adhesive is performed is different from the height (h2) of the wiring substrate to the surface on which the wiring is provided.

[0021] (2) In the optical modulator described in (1) above, the height (h1) of the block is higher than the height (h2) of the wiring board.

[0022] (3) In the optical modulator described in (1) above, a difference between the height (h1) of the block and the height (h2) of the wiring board is 0.2 mm or more.

[0023] (4) In the optical modulator described in (1) above, at least a portion of the periphery of a surface of the block to which the electronic circuit element is bonded is chamfered.

[0024] (5) In the optical modulator described in (1) above, the adhesive bonding the electronic circuit element to the block is conductive.

[0025] (6) In the optical modulator described in (1) above, it is characterized in that an input substrate is arranged in a manner that clamps the electronic circuit element, and the input substrate supplies a high-frequency signal to the optical modulator and the electronic circuit element, and the input substrate, the electronic circuit element and the optical modulator are arranged and fixed in the housing in a manner that a wiring position connecting the input substrate and the electronic circuit element and a wiring position connecting the electronic circuit element and the optical modulator are located on the same plane.

[0026] (7) An optical transmission device comprising the optical modulator according to any one of (1) to (6) above and a data generation unit that supplies a high-frequency signal to the optical modulator.

[0027] The present invention is not limited to the above-mentioned contents, and can of course be configured by combining the technical features (2) to (6) as required.

[0028] Effects of the Invention

[0029] According to the present invention, there can be provided an optical modulator, wherein an optical modulator and an electronic circuit element for inputting a high-frequency signal to the optical modulator are housed in a housing, wherein the electronic circuit element is adhesively fixed to a surface of a block body on the side opposite to one surface, the block body being fixed to the one surface in the housing, the optical modulator having a wiring substrate arranged adjacent to the electronic circuit element and fixed to the one surface, the wiring substrate having wiring electrically connected to the electronic circuit element on the surface opposite to the one surface, and the height (h1) of the block body to the surface to which the adhesive is fixed and the height (h2) of the wiring substrate to the surface provided with the wiring are different from each other with respect to the one surface, so that even when an electronic circuit element such as a drive circuit is arranged close to the wiring substrate, even if the adhesive overflows from a joint portion where the electronic circuit element and the block body are joined, short circuits such as wiring of the wiring substrate can be suppressed. In addition, there can be provided an optical transmission device using an optical modulator having such an effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a top view showing an example of a light modulator.

[0031] Figure 2 yes Figure 1 A cross-sectional view taken along the dashed line A-A'.

[0032] Figure 3 The optical modulator of the present invention is Figure 2 Same cross-section view.

[0033] Figure 4 The optical modulator of the present invention is Figure 2 Another cross-sectional view of the same.

[0034] Figure 5 This is a diagram (part 1) for explaining the process of mounting electronic circuit elements on a light modulator.

[0035] Figure 6 This is a diagram (part 2) for explaining the process of mounting electronic circuit elements on the optical modulator.

[0036] Figure 7 yes Figure 1 A cross-sectional view taken along the dashed line BB'.

[0037] Figure 8 This is a diagram for explaining a block 40 used in the optical modulator of the present invention.

[0038] Fig. 9 This is a diagram for explaining an optical transmission device obtained by connecting a data generation unit to the optical modulator of the present invention.

[0039] Fig.10 This is another conceptual diagram of the optical transmitting device of the present invention.

[0040] Fig.11 It is a diagram for explaining an application example of the optical transmission device of the present invention. DETAILED DESCRIPTION

[0041] Hereinafter, the present invention will be described in detail using preferred examples.

[0042] like Figure 3 and Figure 4 As shown, the present invention relates to an optical modulator, wherein an optical modulator element and an electronic circuit element 4 for inputting a high-frequency signal to the optical modulator element are housed in a housing 1, and is characterized in that the electronic circuit element 4 is bonded and fixed to a surface of a block 40 on the side opposite to a surface, and the block 40 is fixed to the one surface in the housing 1, and the optical modulator has a wiring substrate 3 (3'), which is arranged adjacent to the electronic circuit element 4 and fixed to the one surface, and has wiring electrically connected to the electronic circuit element 4 on the surface of the wiring substrate on the side opposite to the one surface, and with the one surface as a reference, a height h1 of the block 40 to the surface where the bonding is performed and a height h2 of the wiring substrate 3 (3') to the surface where the wiring is provided are different from each other. In addition, Figure 3 and Figure 4 and Figure 2 Likewise, Figure 1 A cross-sectional view of the light modulator taken along the dashed line AA'.

[0043] In the optical modulator element used in the optical modulator of the present invention, as the material for forming the optical waveguide, various materials such as substrates having an electro-optical effect such as lithium niobate (LN), lithium tantalate (LT), PLZT (lead lanthanum zirconate titanate), vapor-grown films formed from these materials, and semiconductor materials, organic materials, etc. can be used.

[0044] The optical modulator forms a modulation electrode along the optical waveguide on the surface of the substrate on which the optical waveguide is formed, and applies a modulation signal as a high-frequency signal to the modulation electrode, thereby modulating the light wave propagating in the optical waveguide. The substrate on which the optical waveguide is formed can also be made into a thin plate of about several μm, and made into a composite substrate bonded to a holding substrate. In addition to the modulation electrode, a bias electrode for applying a DC bias voltage can also be configured separately.

[0045] In the housing used in the optical modulator of the present invention, a metal material with high thermal conductivity such as SUS and Kovar is selected in consideration of machinability, laser welding, sealing and other assembly processes. Figure 3 and 4 The lower surface of the housing 1 is made of metal material, and the housing side surface can also be made of ceramic material or a composite material made of laminated ceramics. When the housing side surface is formed of ceramic material or its composite material, the wiring substrate 3 (3') and the input substrate 2 described later can also be formed integrally with the housing side surface. In addition, although Figure 3 and Figure 4 Although not shown in the figure, a cover made of a metal material is provided on the upper surface side of the housing 1, and the cover and the upper part of the side surface of the housing are hermetically sealed by welding or the like.

[0046] exist Figure 3 and 4 In the embodiment, the housing surface of the fixed block 40 or the like can be set as the bottom surface of the optical modulator body, or can be set as the upper surface of the optical modulator body as shown in Patent Document 3. Figure 3 The housing 1 is fixed to a printed circuit board (not shown) in an upside-down state.

[0047] As the electronic circuit element 4 , a drive circuit for amplifying a modulated signal, a multiplexer (parallel / serial converter) described in Patent Document 4, or the like is used.

[0048] In order to conduct the heat generated by the electronic circuit element 4 to the outside of the housing 1, a block 40 with high thermal conductivity is used to give it a heat sink function. The block 40 is preferably made of a material with higher thermal conductivity than SUS or Kovar used in the housing 1, and a composite of Cu-W, Cu-Mo, Al-SiC, etc. is used.

[0049] As an adhesive for bonding and fixing the electronic circuit element 4 to the block 40, an adhesive having electrical conductivity and thermal conductivity such as Ag filler is preferably used. In addition, when the bonding surface of the electronic circuit element 4 is formed into a metal surface by plating or the like, solder paste may also be used.

[0050] like Figure 3 and 4 As shown, the optical modulator of the present invention is characterized in that the height (h1) of the block 40 and the height (h2) of the wiring substrate 3 (3') arranged close to the block are different from each other. Figure 3 In the case of h1>h2, even if the adhesive AD between the electronic circuit element 4 and the block 40 overflows from the side, the adhesive AD will not reach the wiring substrate 3 (3'). Figure 4In the case of h1<h2, the overflowed adhesive AD reaches the side of the wiring substrate 3 (3'). However, the wiring formed on the wiring substrate 3 (3') is formed (exposed) on the upper surface ( Figure 3 The upper side surface of the wiring substrate 3 (3') of or 4), no wiring is formed on the side surface of the substrate body. Therefore, the wiring of the wiring substrate 3 (3') will not be short-circuited.

[0051] like Figure 3 and Figure 4 As shown, the difference Δh between the height h1 of the block 40 and the height h2 of the wiring substrate 3 (3') is preferably 0.2 mm or more, and more preferably in the range of 0.2 mm to 0.3 mm. In addition, considering the miniaturization of the optical modulator and the amount of overflowing adhesive AD, the interval between the block 40 and the wiring substrate 3 (3') is preferably set in the range of 0.1 to 0.2 mm.

[0052] The wiring substrate 3 (3') is a wiring substrate that supplies power to the electronic circuit element 4 such as the drive circuit, and is supplied with DC power in particular. The DC power supplied from the DC power source located outside the housing 1 is introduced into the wiring substrate 3 (3') via the DC pins or the flexible printed circuit (FPC) arranged on the outer wall surface of the housing 1, and the wiring extending inside the housing. In addition, the electrode pad portion of the wiring of the wiring substrate 3 (3') (the terminal of the wiring formed on the upper surface of the substrate body) is bonded to the terminal of the electronic circuit element 4 through a lead wire (not shown) such as Au.

[0053] When the wiring substrate 3 (3') and the side wall of the housing 1 are integrally formed, as in Patent Document 3, they can be made of a ceramic material or a composite material made of laminated ceramics. In this case, the terminals exposed outside the side wall (or part of the bottom surface) of the housing 1 are connected to the FPC, and the part of the side wall of the housing that becomes the wiring substrate is wire-bonded to the wiring (electrode pad portion) exposed inside the housing, thereby making it possible to simply perform wiring for power supply.

[0054] The adhesive AD can be applied by using a dispenser. Furthermore, it is preferable to use a die mounter so that the adhesive sandwiched between the electronic circuit element 4 and the block 40 is thin and evenly spread.

[0055] Specifically, if Figure 5 As shown in FIG. 1 , after the adhesive AD is applied to the upper surface of the block 40, the electronic circuit element 4 held by the chuck fixture CH by adsorption or the like is pressed against the block 40. At this time, the electronic circuit element 4 is pressed while applying a load to the upper surface of the block, and as shown in FIG. Figure 6 As shown in FIG. 1 , by performing a rubbing operation of moving the chuck jig CH in a direction parallel to the upper surface of the block 40 , the thickness of the adhesive can be formed thin and uniform.

[0056] To perform such a rubbing operation, the electronic circuit element 4 moves parallel to the upper surface of the block 40 , and therefore the wiring substrate 3 ( 3 ′) disposed near the block 40 is preferably lower than the block 40 ( h1 > h2 ).

[0057] As shown in Patent Documents 2 and 3, in order to suppress the propagation loss of the modulated signal as a high-frequency signal, for example, Figure 1 As shown in the patent document 2, it is preferred that the wiring positions of the input substrate 2, the electronic circuit elements 4 such as the drive circuit, and the optical modulation element 5, which are arranged in the housing 1 of the optical modulator, are respectively connected to each other on the same plane. As shown in the patent document 2, it is also preferred that the positions of the upper surfaces of the optical modulation element 5 and the terminal substrate 6 are also arranged on the same plane.

[0058] The input substrate 2 is used to introduce the modulation signal generated by the data generation unit such as the digital signal processing device (Digital Signal Prosessor, DPS) configured outside the optical modulator into the housing 1, and supply it to the electronic circuit element 4 such as the drive circuit. As shown in Patent Document 2, the input substrate 2 can also be formed integrally with the side wall of the housing 1. The main body of the input substrate 2 is composed of a ceramic material or a composite material thereof, and electrical wiring is applied inside or on the surface of the main body.

[0059] The "wiring substrate" in the optical modulator of the present invention is a concept that also includes the "input substrate." In addition, the "wiring substrate" of the present invention may also include a "optical modulation element." Figure 7 yes Figure 1 In the cross-sectional view taken along the dashed line BB' of FIG. 1 , the wiring 20 on the upper surface of the input substrate 2, the upper surface of the electronic circuit element 4 (the surface where the connection terminals are arranged), and the upper surface of the optical modulation element (the surface where the modulation electrodes and the electrode pad portion (terminals) are arranged) are formed into the same plane. The wiring that electrically connects the components is omitted.

[0060] Although it depends on the thickness of the electronic circuit element 4, for example, when the thickness of the electronic circuit element 4 is 0.2 mm or more, the position of the wiring 20 located on the upper surface of the input substrate 2 and the position of the terminal of the modulation electrode located on the upper surface of the optical modulation element are separated by more than 0.2 mm from the position of the bonding surface between the electronic circuit element 4 and the block 40. Therefore, even if the adhesive overflows, the adhesive will not short-circuit the wiring 20 on the upper surface of the input substrate 2 and the terminal of the modulation electrode.

[0061] It should be noted that, when the "wiring substrate" of the present invention includes an "input substrate", the "wiring substrate height h2" is the thickness of the input substrate; when it includes an "optical modulator", the "wiring substrate height h2" is the sum of the height of the base 50 supporting the optical modulator 5 and the thickness of the optical modulator 5 (including the adhesive layer if there is an adhesive layer between the two).

[0062] like Figure 7 As shown, when the upper surfaces of the components are aligned, the direction of the erasing operation when the electronic circuit element 4 is bonded and fixed to the block 40 is limited to the direction in which the wiring substrate 3 (3') is arranged. Therefore, it is preferred that the height h2 of the wiring substrate 3 (3') is set lower than the height h1 of the block 40.

[0063] In order to suppress the amount of adhesive AD overflowing from the block 40, as shown in FIG. Figure 8 As shown, it is preferable to form a chamfered portion 41 at a part of the periphery of the upper surface of the block 40. Thus, the overflowing adhesive AD is received in the chamfered portion, and as a result, the overflowing amount of the adhesive overflowing from the block 40 is reduced.

[0064] Fig. 9 Indicates that the data generation unit (DSP) is connected to Figure 1 The optical transmitter is obtained by using the optical modulator shown in FIG. Fig.10 As shown, as the structure of the optical transmitting device 100, a light source LD such as a semiconductor laser that generates a light wave input to the optical modulator OM, a data generating unit DSP that generates a modulated signal input to the optical modulator OM, and an optical fiber FB for deriving output light from the optical modulator OM can be assembled into one package.

[0065] exist Fig.11 In the embodiment, a light source LD such as a semiconductor laser can also be installed in the housing 1 of the light modulator. In addition, when the light wave output from the light source LD has multiple wavelengths, the light wave generated by the light source can be separated according to each wavelength, and a modulation operation can be performed on each of the light waves. Wavelength separation can use a filter assembled together with an optical component provided in the light source LD, a lens installed at the end of the light modulator, etc. Symbol 80 is an optical block that performs polarization synthesis on each of the light waves and derives the output light of each wavelength. A plurality of optical fibers corresponding to each wavelength are connected to the output collimator 12.

[0066] Furthermore, when a light source such as a semiconductor laser is mounted in housing 1 , in order to sufficiently dissipate heat generated from the light source to the outside, a block (base) supporting the semiconductor laser element needs to be reliably connected to housing 1 , similarly to block 40 .

[0067] Industrial Applicability

[0068] As described above, the present invention can provide an optical modulator capable of suppressing short circuits of wirings of a wiring board even when electronic circuit elements such as a drive circuit are arranged close to the wiring board. Also, an optical transmission device using an optical modulator having such excellent effects can be provided.

[0069] Description of symbols

[0070] 1 Housing

[0071] 2 Input substrate (wiring substrate)

[0072] 3. 3' wiring board

[0073] 4 Electronic circuit components (driving circuits, etc.)

[0074] 5 Light Modulation Element

[0075] 6 Terminal substrate

[0076] 7. Optical components such as lenses

[0077] 8 Optical wavelength division and combination unit (optical block)

[0078] DSP data generation unit (digital processing device)

[0079] LD light source (semiconductor laser)

[0080] FB Fiber

Claims

1. An optical modulator, comprising an optical modulator element and an electronic circuit element for inputting a high-frequency signal to the optical modulator element, housed in a housing, characterized in that: The electronic circuit element is bonded and fixed to a surface of a block body on a side opposite to one surface, and the block body is fixed to the one surface in the housing. The optical modulator includes a wiring substrate, the wiring substrate is arranged adjacent to the electronic circuit element and fixed to the one surface, and a wiring electrically connected to the electronic circuit element is provided on a surface of the wiring substrate opposite to the one surface. With the one surface as a reference, a height (h1) of the block to the surface where the bonding and fixing are performed is different from a height (h2) of the wiring board to the surface where the wiring is provided.

2. The optical modulator according to claim 1, characterized in that The height (h1) of the block is higher than the height (h2) of the wiring substrate.

3. The optical modulator according to claim 1, wherein: A difference between the height (h1) of the block and the height (h2) of the wiring substrate is 0.2 mm or more.

4. The optical modulator according to claim 1, wherein: At least a portion of the periphery of the surface of the block to which the electronic circuit element is bonded is chamfered.

5. The optical modulator according to claim 1, characterized in that The adhesive bonding the electronic circuit element to the block has electrical conductivity.

6. The optical modulator according to claim 1, characterized in that An input substrate is arranged so as to sandwich the electronic circuit element, and the input substrate supplies a high-frequency signal to the light modulation element and the electronic circuit element. The input substrate, the electronic circuit element and the light modulation element are arranged and fixed in the housing in such a manner that the wiring position connecting the input substrate and the electronic circuit element and the wiring position connecting the electronic circuit element and the light modulation element are located on the same plane.

7. An optical transmitting device, characterized in that: A light modulator according to any one of claims 1 to 6 and a data generating unit that supplies a high-frequency signal to the light modulator.

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