Modulation circuit

Abstract

The present invention provides a modulation circuit that increases the freedom of configuration of wiring structures on a substrate. The modulation circuit of the present invention includes: a carrier board (1) having a ground pad (2) on its upper surface; and a wiring section (3) including: a signal line section (31) extending in a predetermined direction and supplying an electrical signal to a modulator (42) for modulating a predetermined signal; a terminating resistor (32) electrically connected to the signal line section (31); and a pad section (33) electrically connected to the terminating resistor (32) and the ground pad (2), wherein the signal line section (31), the terminating resistor (32) and the pad section (33) are arranged sequentially on the carrier board (1) in a direction different from the predetermined direction.

Description

Technical Field

[0001] This invention relates to modulation circuits, particularly modulation circuits used in optical transmitters. Background Technology

[0002] In the past, in modulation circuits, wires (L component) and capacitors (C component) were used to peak the frequency characteristics of the circuit.

[0003] For example, Patent Document 1 discloses a structure in which an RF (Radio Frequency) wiring board and a terminating resistor are positioned on one side of an EA-DFB laser chip (modulation laser chip: Distributed Feedback Laser Integrated with Electro-absorption Modulator) that includes a DFB laser (Distributed Feedback Laser) and an EA modulator (Electro-absorption Modulator). A capacitor and its ground point are positioned on the other side of the modulation laser chip, and a wire is used to connect the terminating resistor and the capacitor across the modulation laser chip. In Patent Document 1, this structure improves the frequency response characteristics even when the wire length varies due to manufacturing errors. Existing technical documents

[0004] Patent Document 1: Japanese Patent Publication No. 2020-127168

[0005] However, in the structure of Patent Document 1, in order to improve the frequency characteristics, the structure for wiring needs to be configured over a wide area on the carrier (substrate) in a way that spans the modulation laser chip, which reduces the degree of freedom in the configuration of the structure for wiring. Summary of the Invention

[0006] Therefore, the object of the present invention is to provide a modulation circuit that enables greater freedom in the configuration of wiring structures on a substrate.

[0007] To achieve the above objectives, the modulation circuit of the present invention employs the following method: the signal line section, the terminating resistor, and the pad section of the wiring section are arranged sequentially in a direction different from the predetermined direction in which the signal line section extends.

[0008] Specifically, the modulation circuit of the present invention includes: a substrate having a ground pad on its upper surface; and a wiring portion including: a signal line portion extending in a predetermined direction for supplying an electrical signal to a modulator that modulates a predetermined signal; a terminating resistor electrically connected to the signal line portion; and a pad portion electrically connected to the terminating resistor and the ground pad, wherein the signal line portion, the terminating resistor, and the pad portion are arranged sequentially on the substrate in a direction different from the predetermined direction.

[0009] Based on the above structure, by arranging the signal line section, terminating resistor, and pad section in a direction different from the direction in which the signal line section extends, the structure for wiring can be compactly and centrally configured. Therefore, the degree of freedom in terminating the wiring is increased, allowing the installation of the wiring termination section to be adjusted according to requirements.

[0010] Alternatively, the wiring section may be surrounded by the grounding pad.

[0011] Therefore, the installation method of the terminal section of the grounding wiring section can be changed.

[0012] Alternatively, a modulated laser chip having the modulator and a chip component for controlling the modulated laser chip may be disposed on the substrate, with the chip component located at a position symmetrical to the wiring portion relative to the modulated laser chip.

[0013] Accordingly, by separating the wiring structure and other structures on both sides of the modulation laser chip, the wiring structure and other structures can be configured without interference, and the degree of freedom of configuration can be increased within their respective given spaces.

[0014] Alternatively, the pad portion may be connected to the grounding pad via multiple wires.

[0015] Therefore, peak control can be appropriately implemented.

[0016] Alternatively, the pad portion may be connected to the ground pad via a chip capacitor.

[0017] Therefore, peak control can be appropriately implemented.

[0018] Alternatively, a flat plate capacitor may be provided on the grounding pad, and the pad portion may be electrically connected to the flat plate capacitor via multiple wires.

[0019] Alternatively, the pad portion may be electrically connected to a capacitor disposed outside the substrate.

[0020] Therefore, peak control can be appropriately implemented.

[0021] Furthermore, the above disclosures can be combined as much as possible.

[0022] The modulation circuit according to the present invention enables greater freedom in the configuration of wiring structures on a substrate. Attached Figure Description

[0023] Figure 1 This is a plan view of the module of the light emitter according to the first embodiment of the present invention. Figure 2 This diagram illustrates the effect of creating a predetermined gap between the grounding and signal line sections. Figure 3 This is a plan view of the module of the light emitter according to the second embodiment of the present invention. Figure 4 This is a plan view of the module of the light emitter according to the third embodiment of the present invention. Figure 5 This is a plan view of the module of the light emitter according to the fourth embodiment of the present invention. Detailed Implementation

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments shown below. These embodiments are merely illustrative, and the present invention can be implemented in various ways with modifications and alterations based on the knowledge of those skilled in the art. Furthermore, in this specification and the accompanying drawings, the same structural elements are designated as identical structural elements.

[0025] (First Embodiment) For the module of the light emitter in the first embodiment of the present invention, refer to... Figure 1 and Figure 2 Please provide an explanation. Figure 1 This is a plan view of the module of the light emitter in the first embodiment. Figure 2 This diagram illustrates the effect of creating a predetermined gap between the grounding and signal line sections. Furthermore, in the following description, the left direction corresponds to the left direction of the module, the right direction corresponds to the right direction of the module, the top direction corresponds to the rear direction of the module, and the bottom direction corresponds to the front direction of the module. The optical transmitter module functions as a "modulation circuit."

[0026] [Structural elements of the optical emitter module] In this embodiment, a grounding pad 2 and an RF (Radio Frequency) wiring section 3 are formed on a carrier board 1, and a laser chip 4 and various chip components 5 are mounted at predetermined locations. The carrier board 1 functions as a "substrate".

[0027] Specifically, the module of the light emitter in this embodiment includes: Carrier plate 1 has a grounding pad 2 on its upper surface; and The wiring section 3 includes: a signal line section 31 extending in a predetermined direction, supplying an electrical signal to an EA modulator 42 (Electro-absorption modulator) that modulates a predetermined signal; a terminating resistor 32 electrically connected to the signal line section 31; and a pad section 33 electrically connected to the terminating resistor 32 and the ground pad 2. The signal line section 31, the terminating resistor 32, and the pad section 33 are arranged sequentially on the carrier board 1 in a direction different from the predetermined direction. The following is a detailed explanation.

[0028] The carrier plate 1 is a flat plate extending in the front-to-back and left-to-right directions. The grounding pad 2 is formed to cover most of the carrier plate 1. The grounding pad 2 is formed on the carrier plate 1 in a shape roughly resembling the katakana character "コ".

[0029] Laser chip 4 is an EA-DFB laser (Distributed Feedback Laser Integrated with Electro-absorption Modulator), disposed at the center of carrier plate 1 extending in a generally front-to-back direction. Laser chip 4 includes a DFB laser 41 (Distributed Feedback Laser) and an EA modulator 42. As a countermeasure against reflected light, the optical guide waveguide of laser chip 4 is a curved waveguide. Therefore, laser chip 4 is configured to emit light forward at an angle other than 90 degrees relative to the emission end face. Laser chip 4 itself is disposed at an angle on carrier plate 1 such that the emitted light is parallel to the front-to-back edge of carrier plate 1, so that the direction of emitted light is forward. Laser chip 4 functions as a "modulated laser chip".

[0030] The DFB laser 41 emits laser light (input light) to the EA modulator 42. The EA modulator 42 modulates the input light from the DFB laser 41 by applying a change corresponding to a predetermined electrical signal described below. The EA modulator 42 functions as a "modulator".

[0031] The RF wiring section 3 is arranged on the left side of the carrier board 1, surrounded by the grounding pad 2. The RF wiring section 3 includes a signal line section 31, a terminating resistor 32, and a pad section 33. The RF wiring section 3 functions as a "wiring section".

[0032] The signal line section 31 is configured to extend in the left-right direction and supply the modulated electrical signal input from its left end to the laser chip 4. Specifically, the electrode of the EA modulator 42 of the laser chip 4 and the right end of the signal line section 31 are electrically connected by a predetermined wire 10. Thus, the modulated electrical signal input from the left end of the signal line section 31 is supplied to the laser chip 4 (EA modulator 42) via the wire 10. The EA modulator 42 generates output light by applying a change to the input light from the DFB laser 41 corresponding to the modulated electrical signal from the signal line section 31. The modulated electrical signal is an example of an "electrical signal".

[0033] The signal line section 31 includes a first line 31A and a second line 31B. The first line 31A functions as a coplanar line formed by being sandwiched between ground pads 2 in the front-to-back direction. Similarly, the second line 31B functions as a coplanar line formed by being sandwiched between pad section 33 and ground pad 2 in the front-to-back direction. The width of the first line 31A in the front-to-back direction is wider than that of the second line 31B in the front-to-back direction. Specifically, the first line 31A and the second line 31B are formed by providing metal wiring on a ceramic material (such as aluminum nitride) with high thermal conductivity.

[0034] The terminating resistor 32 is disposed at the rear end of the second line 31B and is approximately rectangular. The width of the terminating resistor 32 in the front-to-back direction is approximately equal to the width of the second line 31B and the grounding pad 2 in the front-to-back direction.

[0035] The pad portion 33 is electrically connected to the rear of the terminating resistor 32 and is generally rectangular. The pad portion 33 is formed to have a predetermined area on which various components can be mounted. Specifically, in this embodiment, the width of the pad portion 33 in the front-to-back direction is 200 μm and the width in the left-to-right direction is 300 μm. In this embodiment, the pad portion 33 is electrically connected to the ground pad 2 using two wires 13 and 14.

[0036] The details of the relationship between the signal line section 31, the terminating resistor 32, and the pad section 33 will be described later.

[0037] Chip component 5 can be any chip component, such as a passive component like a capacitor or a thermistor. Chip component 5 (capacitor) is electrically connected to DFB laser 41 via wire 11, as shown in the figure, and can be used for controlling DFB laser 41. Chip component 5 is, for example, a square with approximately 400 μm sides.

[0038] [Regarding the configuration relationships of various structural elements] Next, the arrangement of the structural elements described above on the carrier plate 1 will be explained in detail.

[0039] like Figure 1 As shown, the laser chip 4 is mounted approximately at the center of the carrier board 1 in the left-right direction, extending in the approximately front-back direction. On the other hand, the signal line section 31 of the RF wiring section 3 is disposed to the left of the laser chip 4, and is in the shape of a generally rectangular parallelepiped extending in the left-right direction. That is, the signal line section 31 extends in a direction different from that of the laser chip 4. By having the signal line section 31 extend in a generally rectangular parallelepiped shape in the left-right direction, different from the front-back direction of the laser chip 4, space can be ensured in front of or behind the signal line section 31 for the centralized arrangement of the terminating resistor 32 and the pad section 33.

[0040] Furthermore, the signal line section 31, the terminating resistor 32, and the pad section 33 are arranged sequentially in the front-to-back direction. That is, the direction in which the signal line section 31, the terminating resistor 32, and the pad section 33 are arranged is approximately the same as the direction in which the laser chip 4 extends. In other words, the direction in which the signal line section 31, the terminating resistor 32, and the pad section 33 are arranged is approximately orthogonal to the direction in which the signal line section 31 extends. In this way, by arranging the signal line section 31, the terminating resistor 32, and the pad section 33 in a direction different from the direction in which the signal line section 31 extends, the structure for RF wiring can be compactly and centrally configured. The degree of freedom of the RF wiring termination section is increased, thereby allowing the installation of the RF wiring termination section to be adjusted according to requirements.

[0041] Furthermore, in this embodiment, the signal line section 31 is arranged in a generally cuboid shape extending in a left-right direction, different from the front-back direction of the laser chip 4, thereby ensuring space and appropriately arranging the terminating resistor 32 and the pad section 33 within this space. Moreover, by providing the pad section 33, the mounting method (layout) of the RF wiring section 3's termination section can be varied.

[0042] Furthermore, in this embodiment, the pad portion 33 and the ground pad 2 are electrically connected using multiple wires, utilizing the secured space. Peaking control is then appropriately performed by adjusting the length and number of wires. Additionally, the number of wires is not limited to two. Peaking control can be performed using one wire or three or more wires.

[0043] Furthermore, in this embodiment, the RF wiring section 3 and the chip component are arranged in a position approximately symmetrical with respect to the laser chip 4 (EA modulator 42) in the left-right direction. That is, in this embodiment, the structures for RF wiring are concentrated on the left side of the laser chip 4, and the space formed on the right side of the laser chip 4 is used to arrange structures other than those for RF wiring. In other words, in this embodiment, by installing structures other than those for RF wiring on the opposite side from the RF wiring section 3, sufficient space for mounting the RF terminal is ensured.

[0044] Furthermore, the RF wiring section 3 is surrounded by the grounding pad 2. Therefore, the mounting method of the terminal section of the RF wiring section 3 used for grounding can be varied.

[0045] [Regarding the gap between the signal line section and the grounding pad] Next, regarding the gap between the signal line section 31 formed in the RF wiring section 3 and the ground pad 2, refer to... Figure 2 Detailed explanation. In this embodiment, impedance matching is achieved by adjusting the gap between the signal line section 31 and the ground pad 2.

[0046] like Figure 2 As shown, the first line 31A of the signal line section 31 has a width of a μm in the front-to-back direction. Furthermore, a predetermined gap g1 is formed between the first line 31A and the ground pad 2 in the front-to-back direction. The distance between the two walls of the ground pad 2 forming the gap g1 in the front-to-back direction is set to b μm.

[0047] On the other hand, the second line 31B has a width of a'μm in the front-to-back direction. Furthermore, in the front-to-back direction, a predetermined gap g2 is formed between the second line 31B and the ground pad 2, and between the second line 31B and the pad portion 33. The distance between the wall of the ground pad 2 forming the gap g2 and the wall of the pad portion 33 is set to b'μm.

[0048] Here, the impedance characteristics of a general coplanar line are determined by the ratio of the width of the transmission line to the distance between the grounded wall sandwiching the transmission line. That is, in this embodiment, the impedance characteristics of the first line 31A are determined by the ratio of aμm to bμm, and the impedance characteristics of the second line 31B are determined by the ratio of a'μm to b'μm.

[0049] Furthermore, in this embodiment, in order to perform impedance matching between the first line 31A and the second line 31B, the aforementioned ratio is designed to be constant by adjusting the width of each line and the distance between the walls forming each gap. This suppresses signal reflection.

[0050] (Second Implementation) Regarding the modules of the second embodiment of the present invention, refer to... Figure 3 Please provide an explanation. Figure 3 This is a plan view of the light emitter module according to the second embodiment. Furthermore, structures identical to those in the first embodiment are given the same reference numerals, and descriptions are omitted. Additionally, the structure and configuration of this embodiment provide the same effects as those described in the first embodiment.

[0051] In the second embodiment, the chip capacitor 6 is arranged to span between the pad portion 33 and ground.

[0052] The surface-mount capacitor 6 is a surface-mount type. One end of the surface-mount capacitor 6 is electrically connected to the pad portion 33, and the other end of the surface-mount capacitor 6 is electrically connected to the ground pad 2 and grounded. According to this structure, it also has the effect of suppressing power consumption by removing DC (Direct Current).

[0053] (Third implementation) Regarding the modules of the third embodiment of the present invention, refer to... Figure 4 Please provide an explanation. Figure 4 This is a plan view of the light emitter module according to the third embodiment. Furthermore, structures identical to those in the first embodiment are given the same reference numerals, and descriptions are omitted. Additionally, the structure and configuration of this embodiment provide the same effects as those described in the first embodiment.

[0054] In the third embodiment, a flat-plate capacitor 7 is arranged on the ground pad 2 in a left-right direction. The capacitor 7 is electrically connected to the pad portion 33 using two wires 15 and 16. That is, in this embodiment, the pad portion 33 is connected to the ground pad 2 by means of the two wires 15 and 16 and the capacitor 7. Furthermore, the number of wires is not limited to two. One wire can be used, or three or more wires can be used, and peaking control can be performed based on the length and number of wires. According to this structure, power consumption is also suppressed by removing DC current.

[0055] (Fourth implementation) Regarding the modules of the fourth embodiment of the present invention, refer to... Figure 5 Please provide an explanation. Figure 5 This is a plan view of the light emitter module according to the fourth embodiment. Furthermore, structures identical to those in the first embodiment are given the same reference numerals, and descriptions are omitted. Additionally, the structure and configuration of this embodiment provide the same effects as those described in the first embodiment.

[0056] In the fourth embodiment, a chip capacitor 8 is disposed on the outside of the carrier plate 1 in the vertical and horizontal directions of the figure. The chip capacitor 8 is electrically connected to the pad portion 33 using two wires 17 and 18. Furthermore, the number of wires is not limited to two. One wire can be used, or three or more wires can be used, and peaking control can be performed based on the length and number of wires. According to this structure, it also has the effect of suppressing power consumption by removing DC current.

[0057] (Other implementation methods) The aforementioned mounting method for the terminal section of the RF wiring section 3 can be appropriately combined and implemented. Furthermore, the package grounding pins and the like around the carrier board 1 can be electrically connected to the pad section 33.

[0058] Furthermore, the present invention is not limited to optical transmitters, but can be applied to all circuits that use modulated signals. Explanation of reference numerals in the attached figures

[0059] 1: Carrier board 2: Grounding pad 3: RF cabling department 4: Laser chip 41: DFB laser 42: EA modulator 5: Chip components 6, 7, 8: Surface Mount Capacitors 10, 11, 12, 13, 14, 15, 16, 17, 18: Conductors 31: Signal Lines Department 31A: Line 1 31B: Line 2 32: Terminating resistor 33: Solder pad area g1: First gap g2: Second gap.

Claims

1. A modulation circuit, wherein, have: The substrate has a ground pad on its upper surface; and The wiring section includes: a signal line section extending in a predetermined direction, supplying an electrical signal to a modulator that modulates a predetermined signal; a terminating resistor electrically connected to the signal line section; and a pad section electrically connected to the terminating resistor and the ground pad. The signal line section, the terminating resistor, and the pad section are arranged sequentially on the substrate in a direction different from the predetermined direction.

2. The modulation circuit according to claim 1, wherein, The wiring section is surrounded by the grounding pad.

3. The modulation circuit according to claim 1, wherein, A modulated laser chip having the modulator and a chip component for controlling the modulated laser chip are disposed on the substrate. The chip component is located symmetrically to the wiring portion relative to the modulated laser chip.

4. The modulation circuit according to claim 1, wherein, The solder pad is connected to the grounding solder pad by means of multiple wires.

5. The modulation circuit according to claim 1, wherein, The pad portion is connected to the ground pad via a chip capacitor.

6. The modulation circuit according to claim 1, wherein, A flat plate capacitor is provided on the grounding pad. The pads are electrically connected to the flat-plate capacitor via multiple wires.

7. The modulation circuit according to claim 1, wherein, The pad portion is electrically connected to a capacitor disposed outside the substrate.

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