Optical Transmitter and Optical Integrated Circuit

Abstract

To provide an optical transmitter and an optical integrated circuit capable of widening a bandwidth and maintaining good high frequency signal quality.SOLUTION: In an optical transmitter, a ring optical modulator 24 is located on a substrate 22 and includes a set of electrical contacts 244, 246, a set of input pads 23a, 23b are electrically connected to the set of electrical contacts 244, 246 and have a modulated impedance value, and a matching circuit 26 is electrically connected between the set of electrical contacts 244, 246. A set of circuit board bond wires 30a, 30b are electrically connected to a set of signal outputs 14a, 14b and a set of input pads 23a, 23b, and the matching circuit 26 and the set of circuit board bond wires 30a, 30b have a matching impedance value, which substantially matches the modulated impedance value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical transmitter and an optical integrated circuit, and more particularly to an optical transmitter and an optical integrated circuit of an integrated silicon photonics component.

Background Art

[0002] Optical fiber communication generally requires a transmitter for transmitting light and a receiver for receiving light. An optical transmitter (light emitter, optical transmitter) generally includes a light emitting element such as a laser. In recent years, with the progress of technology, some optical transmitters have begun to use silicon photonics components such as optical integrated circuits. An optical transmitter equipped with an optical integrated circuit generally includes an electrical signal processing unit and an optical integrated circuit unit.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, when designing an optical transmitter equipped with an optical integrated circuit, a designer (for example, an inventor) needs to ensure that when transmitting a high-frequency signal from the electrical signal processing part to the optical integrated circuit part, good high-frequency signal quality can be maintained by taking measures such as reducing the occurrence of resonance and widening the bandwidth of the system.

Means for Solving the Problems

[0004] In view of the above problems, the present invention has the following configuration.

[0005] An optical transmitter including a circuit board, an optical integrated circuit, and a set of circuit board bonding wires, wherein the circuit board includes a transmission circuit, and the transmission circuit includes a set of signal output parts, the optical integrated circuit includes a substrate, a ring optical modulator, and a matching circuit, the substrate is provided with a set of input pads, The ring optical modulator is located on the substrate. The ring optical modulator includes a set of electrical contacts. The set of input pads is electrically connected to the set of electrical contacts. The ring optical modulator has a modulation impedance value. The matching circuit is electrically connected between the set of electrical contacts. The set of circuit board bonding wires is electrically connected to the set of signal output parts and the set of input pads. The matching circuit and the set of circuit board bonding wires have a matching impedance value, and the matching impedance value substantially matches the modulation impedance value. An optical transmitter characterized by the above.

[0006] Moreover, the matching circuit includes a matching resistor and a set of substrate bonding wires. The matching resistor is electrically connected between the set of electrical contacts by the set of substrate bonding wires. The set of substrate bonding wires, the matching resistor, and the set of circuit board bonding wires have the matching impedance value. The optical transmitter according to claim 1, characterized by the above.

[0007] Moreover, the set of signal output parts includes a drive signal output part and a ground signal output part. The set of input Pa pads includes a drive signal input pad and a ground signal input pad. The set of electrical contacts includes a drive signal electrical contact and a ground signal electrical contact. The set of circuit board bonding wires includes a drive signal circuit board bonding wire and a ground signal circuit board bonding wire. The drive signal circuit board bonding wire and the ground signal circuit board bonding wire electrically connect the drive signal output part and the ground signal output part to the drive signal input pad and the ground signal input pad respectively. The drive signal input pad and the ground signal input pad are electrically connected to the drive signal electrical contact and the ground signal electrical contact respectively. Both ends of the matching resistor are electrically connected to the drive signal electrical contact and the ground signal electrical contact respectively. The optical transmitter according to claim 2, characterized in that...

[0008] Further, the transmission circuit includes a pulse amplitude modulation circuit, a drive circuit, and a set of signal input parts. The pulse amplitude modulation circuit modulates an input signal from the set of signal input parts into a modulation signal, and the drive circuit converts the modulation signal into a drive signal. The optical transmitter according to claim 1 or 2, characterized in that...

[0009] Furthermore, in an optical integrated circuit including a substrate, a ring optical modulator, and a matching circuit, the substrate is provided with a set of input pads. The ring optical modulator is located on the substrate, and the ring optical modulator includes a closed waveguide, a directional light guide, and a set of electrical contacts. The closed waveguide is adjacent to the directional light guide, the set of input pads is electrically connected to the set of electrical contacts, and the ring optical modulator has a modulation impedance value. The matching circuit is electrically connected between the set of electrical contacts, the matching circuit has a matching resistance value, and the matching resistance value substantially matches the modulation impedance value. The optical integrated circuit, characterized in that...

Advantages of the Invention

[0010] According to the configuration of the present invention, in the optical transmitter or optical integrated circuit of the present invention, since the matching impedance value of the optical transmitter or optical integrated circuit matches the impedance value of the modulator, the optical transmitter or optical integrated circuit has at least one of the effects of suppressing resonance and increasing the system bandwidth.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Figure 4A

Figure 4B

Figure 4C

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 7C

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Best Mode for Carrying Out the Invention

[0012] A description will be given with reference to FIG. 1. Here, FIG. 1 is a perspective view of the optical transmitter of the present invention. The optical transmitter includes a circuit board 10, an optical integrated circuit 20, and circuit board bonding wires 30a and 30b (PCB bond wires).

[0013] The circuit board 10 includes a transmission circuit 12 and further has a set of signal output portions 14a and 14b. The optical integrated circuit 20 includes a substrate 22, a ring optical modulator 24, and a matching circuit (matching circuit) 26. The substrate 22 has a set of input pads 23a and 23b.

[0014] The ring optical modulator 24 is disposed on the substrate 22 and includes a set of electrical contacts 244 and 246. The input pads 23a and 23b are electrically connected to the electrical contacts 244 and 246 of the ring optical modulator 24.

[0015] The ring optical modulator 24 has a modulator impedance value. The circuit board bonding wires 30a and 30b are electrically connected to the signal output portions 14a and 14b and the input pads 23a and 23b. The matching circuit 26 of the optical integrated circuit 20 is electrically connected to the electrical contacts 244 and 246 of the ring optical modulator 24.

[0016] The matching circuit 26 and the circuit board bonding wires 30a and 30b have a matching impedance value, and the matching impedance value substantially matches (matches) the modulator impedance value. In the present embodiment, the matching circuit 26 is electrically connected between the electrical contacts 244 and 246 of the ring optical modulator 24.

[0017] Therefore, since the matching circuit 26 is connected in parallel to the optical integrated circuit 20 and is based on a matching impedance value that matches the modulator impedance value, the matching circuit 26 has a function of suppressing the occurrence of resonance. When the output signals from the signal output portions 14a and 14b of the circuit board 10 pass through the circuit board bonding wires 30a and 30b and the input pads 23a and 23b and are input to the ring modulator 24, reflections that may affect the signal quality are less likely to occur within a predetermined bandwidth.

[0018] In the present embodiment, the statement that "the matching circuit 26 and the circuit board bonding wires 30a and 30b have a matching impedance value" means that "the matching circuit 26 and the circuit board bonding wires 30a and 30b jointly form a matching impedance value".

[0019] In the present embodiment, the inductance value of the circuit board bonding wires 30a and 30b is from 0.1 to 3 nanohenries (nH), the length of one of the circuit board bonding wires 30a and 30b is from 50 to 3000 micrometers (μm), and the diameter of one of the circuit board bonding wires 30a and 30b is from 0.5 to 2 mils.

[0020] In the present embodiment, the matching circuit 26 includes a matching resistor 260 and substrate bonding wires 28a and 28b. The matching resistor 260 is electrically connected between the electrical contacts 244 and 246 via the substrate bonding wires 28a and 28b. The circuit board bonding wires 30a and 30b, the substrate bonding wires 28a and 28b, and the matching resistor 260 form a matching impedance value (matching impedance value) (see FIG. 2, which will be described in detail later).

[0021] The substrate bonding wires 28a and 28b can be electrically connected to both ends of the matching resistor 260 and the electrical contacts 244 and 246 respectively by wire bonding. In this embodiment, the diameter of one of the substrate bonding wires 28a and 28b is 0.5 to 2 mils, and the length of one of the substrate bonding wires 28a and 28b is 50 to 3000 micrometers (μm).

[0022] The resistance value of the matching resistor 260 is 10 to 1000 ohms. The matching resistor 260 may be a sheet resistor (sheet resistance shown in FIG. 1) designed and manufactured by an integrated circuit process, or a single chip resistor or other resistor that can achieve the same effect.

[0023] The aforementioned optical transmitter can be applied to, but is not limited to, an opto - electrical transceiver, a small form factor pluggable transceiver, a quad small factor pluggable - double density (QSFP - DD), and an octal small form factor (OSFP), etc.

[0024] The aforementioned circuit board 10 is used to provide signals transmitted to the optical integrated circuit 20. For example, the transmission circuit 12 receives signals via a set of signal input parts 15a and 15b, processes them by the transmission circuit 12, and then transmits them from the signal output parts 14a and 14b to the optical integrated circuit 20 (details will be described later).

[0025] In this embodiment, the ring optical modulator 24 includes a sealed waveguide 240 and a directional light guide 242. The sealed waveguide 240 is adjacent to the directional light guide 242. The sealed waveguide 240 is a closed loop such as a ring waveguide.

[0026] The above-mentioned directional light guide 242 is an optical waveguide (directional coupler) for signals that propagate directionally, and examples thereof include a curved directional coupler (CDC; or bus waveguide) and a straight directional coupler (SDC).

[0027] The fact that the above-mentioned sealed waveguide 240 is adjacent to the directional light guide 242 means that the distance between the sealed waveguide 240 and the directional light guide 242 is sufficient for both of them to cause an optical coupling effect. That is, this distance is sufficient for coupling light from the directional light guide 242 to the sealed waveguide 240.

[0028] The aforementioned electrical contacts 244 and 246 are usually connected to the PN junction of the ring modulator 24. After an electrical signal is input to the PN junction via the electrical contacts 244 and 246, the bias voltage applied to the PN junction is changed.

[0029] Thereby, the equivalent refractive index in the sealed waveguide 240 is changed together with the input electrical signal, and the intensity or phase of the optical energy coupled from the directional light guide 242 to the sealed waveguide 240 is changed, so as to achieve the effect of modulating light by modifying the magnitude of the amplitude of the light output from the ring modulator 24. Also, the P+ doped region of the PN junction is electrically connected to the signal, and the N+ doped region of the PN junction is grounded.

[0030] The aforementioned matching circuit 26 is electrically connected between the electrical contacts 244 and 246, and there are various implementation forms such as those shown in FIGS. 8 to 9 in addition to FIGS. 1 and 6, although not limited thereto.

[0031] In this embodiment, the number of a set of signal output portions 14a and 14b, the number of a set of input pads 23a and 23b, the number of a set of electrical contacts 244 and 246, and the number of a set of circuit board bonding wires 30a and 30b may be two, three, or more.

[0032] The electrical connection relationship is a one-to-one electrical connection relationship. Taking the embodiment of FIG. 1 as an example, a set of signal output parts 14a, 14b includes an S signal output part 14a and a G signal output part 14b.

[0033] A set of input pads 23a, 23b includes an S input pad 23a and a G input pad 23b, and a set of electrical contacts 244, 246 includes an S electrical contact 244 and a G electrical contact 246. Also, a set of circuit board bonding wires 30a, 30b includes an S circuit board bonding wire 30a and a G circuit board bonding wire 30b.

[0034] The S circuit board bonding wire 30a and the G circuit board bonding wire 30b electrically connect the S signal output part 14a and the G signal output part 14b to the S input pad 23a and the G input pad 23b respectively, and the S input pad 23a and the G input pad 23b are electrically connected to the S electrical contact 244 and the G electrical contact 246 respectively.

[0035] Both ends of the matching resistor 260 are electrically connected to the S electrical contact 244 and the G electrical contact 246 respectively. Specifically, please refer to FIGS. 1 and 2. Both ends of the matching resistor 260 in FIG. 1 are electrically connected between the electrical contacts 244, 246 by the substrate bonding wires 28a, 28b, and the circuit board bonding wires 30a, 30b, the substrate bonding wires 28a, 28b, and the matching resistor 260 form a matching impedance value (matching impedance value).

[0036] Therefore, by connecting the matching resistor 260 in parallel to the ring modulator 24, the S signal output part 14a and the G signal output part 14b can be input to the ring modulator 24 under the condition of less reflection.

[0037] In this embodiment, the S signal output unit 14a, the S circuit board bonding wire 30a, the S input pad 23a, and the S electrical contact 244 are used to transmit a drive signal (the content will be described later) and are electrically connected to the P+ doped region of the ring modulator 24.

[0038] Accordingly, the G signal output unit 14b, the G circuit board bonding wire 30b, the G input pad 23b, and the G electrical contact 246 are used to transmit a ground signal and are electrically connected to the N+ doped region of the ring modulator 24.

[0039] Specifically, due to the electrical connection relationships among the above-described components, the matching impedance value matches (is matched to) the modulator impedance value of the ring modulator 24, reducing the reflection loss caused by the discontinuity of the interface impedance generated when a high-frequency signal is input to the ring modulator 24, and compensating for the variation in frequency response that easily occurs when the circuit board 10 is connected to the ring modulator 24.

[0040] In this embodiment, the matching impedance value is from 10 to 1000 ohms. However, the matching impedance value can be designed based on the overall impedance of the actual implementation. For example, the matching impedance value can be designed based on the flatness of the required frequency response, the value of the bandwidth, or the degree of compensation for the high-frequency loss of the entire system channel.

[0041] The matching impedance will be described with reference to FIG. 2. Here, FIG. 2 is a schematic diagram of an equivalent circuit of the optical integrated circuit of the present invention.

[0042] FIG. 2 shows that a signal from the S signal output unit 14a of the circuit board 10 reaches the ring modulator 24 via the S circuit board bonding wire 30a, the S input pad 23a, and the S electrical contact 244, and the G signal output unit 14b, the G substrate bonding wire 30b, the G input pad 23b, and the G electrical contact 246 are equivalent circuit diagrams of the ground.

[0043] As can be seen from the figure, when the matching impedance value (in the embodiment of FIG. 1, the matching impedance value formed by the inductance values of the circuit board bonding wires 30a and 30b, the inductance values of the substrate bonding wires 28a and 28b, and the resistance value of the matching resistor 260) can match the modulator impedance value of the ring optical modulator 24, signal reflection can be significantly reduced, and the stability of high-frequency signal transmission can be improved.

[0044] Since the impedance value of the modulator based on the ring optical modulator 24 cannot be determined immediately at the design time, the optical transmitter of this embodiment can match the impedance value (that is, the wire diameters and lengths of the circuit board bonding wires 30a and 30b, the wire diameters and lengths of the substrate bonding wires 28a and 28b, and the resistance value of the matching resistor 260) through appropriate design.

[0045] By conducting corresponding experiments, better resistance values of the matching resistor 260, inductance values of the substrate bonding wires 28a and 28b, and inductance values of the circuit board bonding wires 30a and 30b can be obtained.

[0046] Here, the inductance values of the substrate bonding wires 28a and 28b and the inductance values of the circuit board bonding wires 30a and 30b can be obtained by adjusting the wire diameter (also referred to as the diameter of the wire, wire diameter, or line diameter) and / or the wire length (the length of the wire).

[0047] As can be seen from FIG. 2, the preferred embodiment is as follows. That is, the diameters and lengths of the substrate bonding wires 28a and 28b, the resistance value of the matching resistor 260, and the inductance values of the circuit board bonding wires 30a and 30b match the modulator impedance value of the ring optical modulator 24.

[0048] Table 1 below shows a method of optimizing the bandwidth by adjusting the inductance values of different circuit board bonding wires 30a and 30b, the resistance value of the matching resistor 260, and the inductance values of the substrate bonding wires 28a and 28b, respectively. FIGS. 3A, 3B, and 3C will be described together.

[0049] FIGS. 3A, 3B, and 3C are schematic diagrams of the frequency responses of the optical integrated circuits corresponding to the parameters of Group A, Group B, and Group C in Table 1 of FIGS. 1 and 2, respectively. The horizontal axis in FIGS. 3A to 3C is frequency, with the unit being GHz (gigahertz), and the vertical axis is Response, with the unit being dB (decibel).

[0050] From this figure, it can be seen that the optical integrated circuit 20 corresponds to different sets of design parameters and can obtain a 3dB bandwidth with a flat frequency response in different frequency bands.

Table 1

[0051] Next, referring to FIGS. 4A, 4B, and 4C, FIG. 4A is a schematic diagram of the frequency response of the ring modulator itself in the embodiment of FIG. 1. That is, in FIGS. 1 and 2, the circuit board bonding wires 30a and 30b, the substrate bonding wires 28a and 28b, and the matching resistor 260 are removed, and it is a frequency response diagram of the ring modulator 24 itself.

[0052] Here, FIG. 4B is a schematic diagram of the frequency response of the optical integrated circuit 20 including the circuit board bonding wires 30a and 30b in the embodiment of FIG. 1 and not including the substrate bonding wires 28a and 28b and the matching resistor 260. FIG. 4C is a schematic diagram of the frequency response of the optical integrated circuit in the embodiment of FIG. 1.

[0053] From FIG. 4B, it can be seen that the ring modulator 24 (optical integrated circuit 20) has an obvious protruding phenomenon of the frequency response due to resonance around 25 GHz after assembly and bonding.

[0054] will be described with reference to FIG. 4C. In FIG. 4C, the optical integrated circuit 20 includes appropriate matching resistors 260, circuit board bonding wires 30a and 30b, and substrate bonding wires 28a and 28b, and the above-described resonance problem is solved and the frequency response is flattened.

[0055] Continuing to refer to FIG. 1, in the present embodiment, the transmission circuit 12 includes a pulse amplitude modulation circuit 16, a drive circuit 18, and a set of signal input portions 15a and 15b (FIG. 1 shows the pulse amplitude modulation circuit 16 and the drive circuit 18 as two blocks respectively).

[0056] The pulse amplitude modulation circuit 16 converts the input signals from the signal input portions 15a and 15b into modulation signals according to system requirements, and the drive circuit 18 converts the modulation signals into drive signals and outputs them to the optical integrated circuit 20 via the signal output portions 14a and 14b.

[0057] In the present embodiment, the pulse amplitude modulation circuit 16 is a 4-level Pulse Amplitude Modulation (PAM4) that modulates the input signals into 4-level pulse amplitude modulation signals.

[0058] This will be described with reference to FIG. 5. Here, FIG. 5 is a schematic top view of the optical integrated circuit according to the present embodiment of the present invention. The optical integrated circuit 20m includes a substrate 22, a ring optical modulator 24, and a plurality of impedance pads 27a, 27b, 27c, and 27d (referred to as the first set of impedance pads 27a and 27b and the second set of impedance pads 27c and 27d respectively).

[0059] The impedance pads 27a, 27b, 27c, and 27d are arranged beside the ring optical modulator 24. In the present embodiment, each set of impedance pads 27a, 27b, 27c, and 27d is substantially at the same distance from the electrical contacts 244 and 246 of the ring optical modulator 24.

[0060] For example, the distance between the S resistance pad 27a of the first group (first group) and the S electrical contact 244 is the same as the distance between the G resistance pad 27b of the first group and the G electrical contact 246, and the distance between the S resistance pad 27c of the second group and the S electrical contact 244 is the same as the distance between the G resistance pad 27d of the second group and the G electrical contact 246.

[0061] The optical integrated circuit 20m can be used to test the substrate bonding wires 28a and 28b corresponding to an appropriate matching impedance value when the modulator impedance value of the ring optical modulator 24 is unknown.

[0062] Specifically, the designer can configure different matching resistors 260 on the impedance pads 27a, 27b, 27c, and 27d of each group, and use substrate bonding wires 28a and 28b with different wire diameters and lengths to obtain different matching circuit 26 and corresponding matching impedance values. Then, based on the frequency response diagram, an appropriate matching impedance value and the wire diameters and lengths of the corresponding substrate bonding wires 28a and 28b are determined.

[0063] The number of groups (number of sets) of the above-mentioned impedance pads 27a, 27b, 27c, and 27d can be adjusted as needed. For example, the optical integrated circuit 20m includes three groups of impedance pads 27a, 27b, 27c, 27d, 27e, and 27f. However, it is not limited to this, and the number of groups of the resistance pads 27a, 27b, 27c, 27d, 27e, and 27f may be four or more groups.

[0064] This will be described with reference to FIG. 6. Here, FIG. 6 is a schematic top view of an optical transmitter according to an embodiment of the present invention.

[0065] In this embodiment, the optical transmitter includes a circuit board 10, an optical integrated circuit 20, and circuit board bonding wires 30a and 30b. The circuit board 10 includes a transmission circuit 12 and has a set of signal output portions 14a and 14b. The optical integrated circuit 20 includes a substrate 22, a ring optical modulator 24, and a matching circuit 26.

[0066] The substrate 22 has a set of input pads 23a and 23b. The ring optical modulator 24 is disposed on the substrate 22 and includes a sealed waveguide 240, a directional light guide 242, and a set of electrical contacts 244 and 246. The sealed waveguide 240 is adjacent to the directional light guide 242.

[0067] The input pads 23a and 23b are electrically connected to the electrical contacts 244 and 246 of the ring optical modulator 24. The ring optical modulator 24 has a modulator impedance value. The circuit board bonding wires 30a and 30b are electrically connected to the signal output portions 14a and 14b and the input pads 23a and 23b.

[0068] The matching circuit 26 of the optical integrated circuit 20 is electrically connected to the electrical contacts 244 and 246 of the ring optical modulator 24. The matching circuit 26 and the circuit board bonding wires 30a and 30b have a matching impedance value, and this matching impedance value is matched (matched) with the impedance value of the modulator.

[0069] This embodiment can be applied to an optical transmitter in which the input signal is in the GSG (Ground-Signal-Ground) format. As not apparent from the figure, the matching circuit 26 of the embodiment of FIG. 6 is a matching resistor 260, and both ends of the matching resistor 260 are directly and electrically connected between the electrical contacts 244 and 246.

[0070] A description will be given with reference to FIGS. 7A to 7C. Here, FIG. 7A is a schematic diagram of the frequency response of an optical integrated circuit without a matching circuit in the embodiment of FIG. 2. Further, FIG. 7B is a schematic diagram of the frequency response of an optical integrated circuit (the matching circuit includes a matching resistor) in the embodiment of FIG. 6. Furthermore, FIG. 7C is a schematic diagram of the frequency response of the optical integrated circuit (the matching circuit includes a matching resistor and substrate bonding wires) in the embodiment of FIG. 2.

[0071] From FIG. 7A, it can be seen that the optical integrated circuit 20 without the matching circuit 26 causes resonance, the frequency response becomes non-uniform, and a convex portion occurs at a frequency of 30 GHz.

[0072] The matching circuit 26 of the optical integrated circuit 20 shown in FIG. 7B includes only the matching resistor 260. Since the matching resistor 260 has an effect of suppressing resonance, the frequency response has no protrusion at 30 GHz. However, the 3 dB bandwidth of the optical integrated circuit 20 is affected and decreased.

[0073] The matching circuit 26 of the optical integrated circuit 20 shown in FIG. 7C includes the matching resistor 260 and the substrate bonding wires 28a, 28b. The bandwidth of the optical integrated circuit 20 not only does not increase near 30 GHz, but also the 3 dB bandwidth (which decreased in FIG. 7B) increases.

[0074] Therefore, in the embodiment where the matching circuit 26 includes the matching resistor 260 and the substrate bonding wires 28a, 28b, the optical integrated circuit 20 not only has an effect of suppressing resonance, but also has an effect of widening the bandwidth of the system.

[0075] A description will be given with reference to FIG. 8. FIG. 8 is a schematic top view of an optical transmitter according to an embodiment of the present invention. The optical transmitter of the embodiment of FIG. 8 includes a circuit board 10, an optical integrated circuit 20, and a set of circuit board bonding wires 30a, 30b, 30c.

[0076] The circuit board 10 includes a set of signal output parts 14a, 14b, and 14c. The optical integrated circuit 20 includes a substrate 22, a ring optical modulator 24, and a matching circuit 26. The substrate 22 includes a set of input pads 23a, 23b, and 23c.

[0077] The matching circuit 26 includes a first matching resistor 260 and a second matching resistor 262. The ring optical modulator 24 includes a sealed waveguide 240, a directional light guide 242, and a set of electrical contacts 244, 246, and 248.

[0078] The circuit board bonding wires 30a, 30b, and 30c include an S circuit board bonding wire 30a, a first G circuit board bonding wire 30b, and a second G circuit board bonding wire 30c.

[0079] The signal output parts 14a, 14b, and 14c include an S signal output part 14a, a first G signal output part 14b, and a second G signal output part 14c. The input pads 23a, 23b, and 23c include an S input pad 23a, a first G input pad 23b, and a second G input pad 23c.

[0080] The electrical contacts 244, 246, and 248 include an S electrical contact 244, a first G electrical contact 246, and a second G electrical contact 248.

[0081] The S circuit board bonding wire 30a, the first G circuit board bonding wire 30b, and the second G circuit board bonding wire 30c electrically connect the S signal output part 14a, the first G signal output part 14b, and the second G signal output part 14c to the pads 23a, the first G input pad 23b, and the second G input pad 23c respectively.

[0082] The S input pad 23a, the first G input pad 23b, and the second G input pad 23c are electrically connected to the S electrical contact 244, the first G electrical contact 246, and the second G electrical contact 248 respectively.

[0083] Both ends of the first matching resistor 260 are electrically connected to the S electrical contact 244 and the first G electrical contact 246, respectively, and the two terminals of the second matching resistor 262 are electrically connected to the S electrical contact 244 and the second G electrical contact 248, respectively.

[0084] In the embodiment of FIG. 8, both ends of the first matching resistor 260 are directly and electrically connected to the S electrical contact 244 and the first G electrical contact 246, respectively. Both ends of the second matching resistor 262 are directly and electrically connected to the S electrical contact 244 and the second G electrical contact 248, respectively.

[0085] Therefore, the first matching resistor 260, the second matching resistor 262, and the circuit board bonding wires 30a, 30b, 30c have a matching impedance value. Since the matching impedance value substantially matches the impedance of the modulator, the matching circuit 26 has the effect of suppressing resonance.

[0086] In the embodiment of FIG. 9, both ends of the first matching resistor 260 are indirectly and electrically connected to the S electrical contact 244 and the first G electrical contact 246, respectively, and both ends of the second matching resistor 262 are indirectly and electrically connected to the S electrical contact 244 and the second G electrical contact 248, respectively.

[0087] In this embodiment, the matching circuit 26 includes a set of substrate bonding wires 28a, 28b, 28c, and the substrate bonding wires 28a, 28b, 28c include an S substrate bonding wire 28a, a first G substrate bonding wire 28b, and a second G substrate bonding wire 28c.

[0088] The S substrate bonding wire 28a and the first G substrate bonding wire 28b electrically connect both ends of the first matching resistor 260 to the S electrical contact 244 and the first G electrical contact 246, respectively.

[0089] The S substrate bonding wire 28a and the second G substrate bonding wire 28c electrically connect both ends of the second matching resistor 262 to the S electrical contact 244 and the second G electrical contact 248, respectively.

[0090] Therefore, the first matching resistor 260, the second matching resistor 262, the substrate bonding wires 28a, 28b, 28c, and the circuit board bonding wires 30a, 30b, 30c have matching impedance values. Since the matching impedance substantially matches the modulator impedance (also used in the sense of "matching"), the matching circuit 26 can suppress resonance and increase (widen) the bandwidth of the system.

[0091] This will be described with reference to FIG. 10. Here, FIG. 10 is a schematic top view of an optical integrated circuit according to an embodiment of the present invention.

[0092] The optical integrated circuit 20n includes a substrate 22, a ring optical modulator 24, and a plurality of impedance pads 27a, 27b, 27c, 27d, 27e, 27f (also referred to as the first group (first set) of impedance pads 27a, 27b, 27c and the second group of impedance pads 27d, 27e, 27f, respectively), and these impedance pads 27a, 27b, 27c, 27d, 27e, 27f are arranged beside the ring optical modulator 24.

[0093] A set of impedance pads 27a, 27b, 27c may be constituted by the first matching resistor 260 and the second matching resistor 262.

[0094] In this embodiment, the impedance pads 27a, 27b, 27c, 27d, 27e, 27f of each set (each group) are at substantially the same distance from the electrical contacts 244, 246, 248 of the ring optical modulator 24. Since this part is the same as the description of FIG. 5, it will not be repeated here.

[0095] The optical integrated circuit 20n can be used to test the substrate bonding wires 28a, 28b, 28c (not shown in FIG. 10, see FIG. 8) corresponding to an appropriate matching impedance value when the modulator impedance value of the ring optical modulator 24 is unknown.

[0096] Specifically, the designer can configure different matching resistors 260 on each group of the impedance pads 27a, 27b, 27c, 27d, 27e, 27f, use substrate bonding wires 28a, 28b, 28c with different wire diameters and lengths, obtain the corresponding matching impedance values for different matching circuits 26, and together, based on the frequency response diagram, determine the appropriate matching impedance value and the corresponding wire diameters and lengths of the substrate bonding wires 28a, 28b, 28c.

[0097] The number of groups (number of sets) of the above-mentioned resistance pads 27a, 27b, 27c, 27d, 27e, 27f can be adjusted as needed. For example, the optical integrated circuit 20n can include three groups of impedance pads 27a, 27b, 27c, 27d, 27e, 27f, 27g, 27h, 27i.

[0098] However, it is not limited to this. The number of groups of impedance pads may be four or more, such as 27a, 27b, 27c, 27d, 27e, 27f, 27g, 27h, 27i, etc.

[0099] Next, it will be described with reference to FIG. 11. FIG. 11 is a schematic top view of an optical integrated circuit according to an embodiment of the present invention. The optical integrated circuit 20p includes a substrate 22, a ring optical modulator 24, and a plurality of impedance pads 27a, 27b, 27c, 27d, 27e, 27f, 27g, 27h, 27i, 27j, 27k, 27l (hereinafter, may be referred to as the first set of impedance pads 27a, 27b, the second set of impedance pads 27c, 27d, etc., respectively).

[0100] A pair of resistance pads 27a and 27b can be configured using a matching resistor 260. The optical integrated circuit 20p can be used to test the substrate bonding wires 28a, 28b, 28a', and 28b' corresponding to an appropriate matching impedance value when the modulator impedance value of the ring optical modulator 24 is unknown.

[0101] Specifically, the designer can configure different matching resistors 260 on each set of impedance pads 27a, 27b, 27c, 27d, 27e, 27f, 27g, 27h, 27i, 27j, 27k, and 27l, and use substrates with different wire diameters and lengths. The bonding wires 28a, 28b, 28a', 28b', and different matching circuits 26 can be used to obtain corresponding matching impedance values. Based on the frequency response diagram, an appropriate matching impedance value and the wire diameters and lengths of the corresponding substrate bonding wires 28a, 28b, 28a', and 28b' can be determined.

[0102] The number of groups (number of sets) of the above-mentioned resistance pads 27a, 27b, 27c, 27d, 27e, 27f, 27g, 27h, 27i, 27j, 27k, 27l can be adjusted as needed. For example, but not limited to, it can be three groups, four groups, five groups, six groups, or more groups.

[0103] Table 2 shows the inductance values and corresponding impedance characteristics composed of different wire diameters and wire lengths with a 3dB bandwidth of a flat frequency response of 26GHz. The designer can adjust and adapt the required characteristics of the ring optical modulator 24 based on Table 2 to optimize the signal quality (suppress resonance and broaden the bandwidth).

[0104] The following table shows the heights of three identical wire bondings (200, 300, 400 um) and their corresponding wire lengths (570, 641, 722 um). To correspond to different wire diameters (0.5, 1, 2 mil), different impedance characteristics are obtained. The real part of the impedance characteristic is denoted as R, and the imaginary part is denoted as X. The impedance characteristic corresponding to each set of wire diameter, wire height, and wire length is R + J*X. [Table 2]

[0105] Next, it will be described with reference to FIG. 12. Here, FIG. 12 is a schematic diagram of the frequency response of the optical integrated circuit according to the embodiment of FIG. 2.

[0106] This figure is based on the equivalent circuit diagrams of the embodiments of FIGS. 1 and 2. Before the inductance values of the circuit board bonding wires 30a and 30b are fixed and the matching resistor 260 is fixed, the inductive peaking method is used to obtain the desired inductance values of the substrate bonding wires 28a and 28b.

[0107] The frequency response curves m1, m2, m3, m4, and m5 correspond to the parameters of different substrate bonding wires 28a and 28b, respectively. The inductance values of the corresponding substrate bonding wires 28a and 28b are 0.3 nH, 0.6 nH, 0.9 nH, 1.2 nH, and 1.5 nH (nanohenry), respectively.

[0108] From this figure, it can be seen that the 3 dB bandwidth of the m1 frequency response curve is about 39 GHz (at the position of mark b1 in the figure). The 3 dB bandwidth of the frequency response curve m2 is about 49 GHz (at the position of mark b2 in the figure). Therefore, the 3 dB bandwidth of the frequency response curve m2 increases by about 10 GHz compared to the frequency response curve m1.

[0109] Also, considering the high-frequency response, when comparing the responses at 30 GHz, the response of the frequency response curve m2 at 30 GHz is about -0.6 dB (marked at the position of the frequency response curve m2 in the figure), and the response of the frequency response curve m5 at 30 GHz is about 2.25 dB (marked at the position of the frequency response curve m5 in the figure).

[0110] Therefore, when the inductance values of the substrate bonding wires 28a and 28b are 1.5 nH, the frequency response at 30 GHz is improved by about 2.85 dB (2.25 - (-0.6) = 2.85).

[0111] Therefore, by arranging the substrate bonding wires 28a and 28b having larger inductance values, excessive loss of the system channel at high frequencies can be avoided, and the high-frequency response loss is compensated in advance to maintain a flat frequency response. For this reason, as shown in the experimental results of FIG. 12, a desired resonance suppression effect and an effect of increasing the bandwidth of the system can be obtained.

[0112] Referring back to FIG. 1 for explanation. In the embodiment of the present invention, an optical integrated circuit 20 is further provided. The optical integrated circuit 20 is an electronic component before being electrically connected to the circuit board 10. The optical integrated circuit 20 includes a substrate 22, a ring optical modulator 24, and a matching circuit 26.

[0113] The substrate 22 has a set of input pads 23a and 23b. The ring optical modulator 24 is disposed on the substrate 22 and includes a sealed waveguide 240, a directional light guide 242, and a set of electrical contacts 244 and 246.

[0114] The sealed waveguide 240 is adjacent to the directional light guide 242. The input pads 23a and 23b are electrically connected to the electrical contacts 244 and 246 of the ring optical modulator 24. The ring optical modulator 24 has a modulator impedance value. The matching circuit 26 is electrically connected to the electrical contacts 244 and 246 of the ring optical modulator 24.

[0115] The matching circuit 26 has a matching impedance that substantially matches the impedance of the modulator. In the present embodiment, the matching circuit 26 is electrically connected between the electrical contacts 244 and 246 of the ring optical modulator 24.

[0116] The optical integrated circuit 20 of the present embodiment does not consider the inductance values of the circuit board bonding wires 30a and 30b. The matching impedance value of the matching circuit 26 is directly matched to the impedance value of the modulator. However, even when the circuit board 10 is not matched, the optical integrated circuit 20 of the present embodiment can obtain a good effect of suppressing resonance and increasing the system bandwidth.

[0117] In addition, the optical integrated circuit 20 of the present embodiment can also be adapted to a circuit board 10 with a predetermined specification (standard). The predetermined specification of the circuit board 10 is, for example, the inductance values of a set of circuit board bonding wires 30a and 30b having a specific impedance, for example, the inductance values of specific circuit board bonding wires 30a and 30b as shown in Table 1.

[0118] That is, when selling the optical integrated circuit 20 of the present embodiment, the design specifications can be provided to the user, making it easy for the user to design in the optimal impedance matching mode.

[0119] In addition, the optical integrated circuit 20 of the present embodiment can also be designed with relatively common inductance values of the circuit board bonding wires 30a and 30b.

[0120] That is, the average value, median value, etc. of the inductance values of the more general circuit board bonding wires 30a and 30b are used to match the matching impedance value to the modulator impedance value by using the average inductance value (or median inductance value) of the circuit board bonding wires 30a and 30b and the matching impedance value formed by the matching circuit 26.

[0121] Even in this way, the optical integrated circuit 20 can obtain a good effect of suppressing resonance and increasing the bandwidth of the system.

[0122] In this embodiment, as shown in FIG. 1, the aforementioned matching circuit 26 includes a matching resistor 260 and a pair of substrate bonding wires 28a, 28b. The matching resistor 260 is electrically connected between the electrical contacts 244 and 246 via the substrate bonding wires 28a, 28b. The resistance values of the substrate bonding wires 28a, 28b and the matching resistor 260 form a matching impedance value.

[0123] In this embodiment, as shown in FIG. 6, the aforementioned matching circuit 26 includes a matching resistor 260. Both ends of the matching resistor 260 are directly and electrically connected between the electrical contacts 244 and 246, and the resistance value of the matching resistor 260 forms a matching impedance value.

[0124] In an embodiment of the present invention, the input pads 23a, 23b include an S input pad 23a and a G input pad 23b, and the electrical contacts 244, 246 include an S electrical contact 244 and a G electrical contact 246. The S input pad 23a and the G input pad 23b are electrically connected to the S electrical contact 244 and the G electrical contact 246, respectively, and the matching circuit 26 is electrically connected between the S electrical contact 244 and the G electrical contact 246.

[0125] In this embodiment, the matching impedance value is from 10 to 1000 ohms.

[0126] The optical integrated circuit 20 of the embodiment in FIG. 8 includes a substrate 22, a ring optical modulator 24, and a matching circuit 26. The substrate 22 includes a pair of input pads 23a, 23b, 23c.

[0127] The matching circuit 26 includes a first matching resistor 260 and a second matching resistor 262. The ring modulator 24 includes a sealed waveguide 240, a directional light guide 242, and a set of electrical contacts 244, 246, 248.

[0128] The input pads 23a, 23b, 23c include an S input pad 23a, a first G input pad 23b, and a second G input pad 23c. The electrical contacts 244, 246, 248 include an S electrical contact 244, a first G electrical contact 246, and a second G electrical contact 248.

[0129] The S input pad 23a, the first G input pad 23b, and the second G input pad 23c are electrically connected to the S electrical contact 244, the first G electrical contact 246, and the second G electrical contact 248, respectively.

[0130] Both ends of the first matching resistor 260 are electrically connected to the S electrical contact 244 and the first G electrical contact 246, respectively, and both ends of the second matching resistor 262 are electrically connected to the S electrical contact 244 and the second G electrical contact 248, respectively.

[0131] In this embodiment, both ends of the first matching resistor 260 are directly and electrically connected to the S electrical contact 244 and the first G electrical contact 246, and both ends of the second matching resistor 262 are directly and electrically connected to the S electrical contact 244 and the second G electrical contact 248.

[0132] In this embodiment, the matching circuit further includes a set of substrate bonding wires 28a, 28b, 28c. The substrate bonding wires 28a, 28b, 28c include an S substrate bonding wire 28a, a first G substrate bonding wire 28b, and a second G substrate bonding wire 28c.

[0133] The S substrate bonding wire 28a and the first G substrate bonding wire 28b electrically connect both ends of the first matching resistor 260 to the S electrical contact 244 and the first G electrical contact 246, respectively. The S substrate bonding wire 28a and the second G substrate bonding wire 28c electrically connect both ends of the second matching resistor 262 to the S electrical contact 244 and the second G electrical contact 248, respectively.

[0134] As described above, in the embodiment of the present invention, since the matching impedance value of the optical transmitter or the optical integrated circuit matches the impedance value of the modulator, the optical transmitter or the optical integrated circuit exhibits at least one of the effects of suppressing resonance and increasing the system bandwidth.

Description of Reference Numerals

[0135] 10 Circuit board 12 Transmission circuit 14a, 14b, 14c Signal output section 15a, 15b Signal input section 16 Pulse amplitude modulation circuit 18 Drive circuit 20, 20m, 20n, 20p Optical integrated circuit 22 Substrate 23a, 23b, 23c Input pad 24 Ring optical modulator 240 Hermetic waveguide 242 Directional light guide 244, 246, 248 Electrical contact 26 Matching circuit 260, 262 Matching resistor 27a, 27b, 27c, 27d, 27e, 27f Impedance pad 27g, 27h, 27i, 27j, 27k, 27l Impedance pad 28a, 28b, 28c, 28a’, 28b’ Substrate bonding wire 30a, 30b, 30c Circuit board bonding wire m1, m2, m3, m4, m5 Frequency response curve 3dB bandwidth of the b1 and b2 frequency response curves

Claims

1. An optical transmitter comprising a circuit board, an optical integrated circuit, and a set of circuit board bonding wires, wherein the circuit board includes a transmission circuit, and the transmission circuit includes a set of signal output portions, the optical integrated circuit includes a substrate, a ring optical modulator, and a matching circuit, the substrate is provided with a set of input pads, the ring optical modulator is located on the substrate, the ring optical modulator includes a set of electrical contacts, the set of input pads are electrically connected to the set of electrical contacts, the ring optical modulator has a modulation impedance value, and the matching circuit is electrically connected between the set of electrical contacts, the set of circuit board bonding wires are electrically connected to the set of signal output portions and the set of input pads, the matching circuit and the set of circuit board bonding wires have a matching impedance value, and the matching impedance value substantially matches the modulation impedance value An optical transmitter characterized by the above.

2. The matching circuit includes a matching resistor and a set of substrate bonding wires, the matching resistor is electrically connected between the set of electrical contacts by the set of substrate bonding wires, and the set of substrate bonding wires, the matching resistor, and the set of circuit board bonding wires have the matching impedance value The optical transmitter according to claim 1, characterized by the above.

3. The set of signal output portions includes a drive signal output portion and a ground signal output portion, the set of input pads includes a drive signal input pad and a ground signal input pad, the set of electrical contacts includes a drive signal electrical contact and a ground signal electrical contact, the set of circuit board bonding wires includes a drive signal circuit board bonding wire and a ground signal circuit board bonding wire, and the drive signal circuit board bonding wire and the ground signal circuit board bonding wire electrically connect the drive signal output portion and the ground signal output portion to the drive signal input pad and the ground signal input pad, respectively, the drive signal input pad and the ground signal input pad are electrically connected to the drive signal electrical contact and the ground signal electrical contact, respectively, and both ends of the matching resistor are electrically connected to the drive signal electrical contact and the ground signal electrical contact, respectively The optical transmitter according to claim 2, characterized by the above.

4. The transmission circuit includes a pulse amplitude modulation circuit, a drive circuit, and a set of signal input parts. The pulse amplitude modulation circuit modulates an input signal from the set of signal input parts into a modulation signal, and the drive circuit converts the modulation signal into a drive signal. The optical transmitter according to claim 1 or 2, characterized in that.

5. In an optical integrated circuit including a substrate, a ring optical modulator, and a matching circuit, the substrate includes a set of input pads, the ring optical modulator is located on the substrate, and the ring optical modulator includes a closed waveguide, a directional light guide, and a set of electrical contacts. The closed waveguide is adjacent to the directional light guide, the set of input pads is electrically connected to the set of electrical contacts, and the ring optical modulator has a modulation impedance value. The matching circuit is electrically connected between the set of electrical contacts, the matching circuit has a matching resistance value, and the matching resistance value substantially matches the modulation impedance value. An optical integrated circuit, characterized in that.

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