Optical modulator and optical transceiver

Abstract

According to the optical modulator and the optical transceiver, the transmission efficiency of optical signals can be improved. An optical modulator (10) is provided with: a substrate (50); a coplanar line (40) having a first ground line (41), a second ground line (42), and a signal line (43); a waveguide (20) located between the first ground line (41) and the signal line (43) and having an input unit (21) and an output unit (22) for an optical signal; and an adjustment member (30) that is positioned between the second ground line (42) and the signal line (43) and that does not have an input unit and an output unit for the optical signal.

Description

[0001] [Related application reference]

[0002] This application claims the benefit of Japanese Patent Application No. 2022-116739 filed on July 1, 2022, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The invention relates to an optical modulator and an optical transceiver. Background Art

[0004] A structure is known in which an optical waveguide is located between a ground line and a common signal line on one side of a coplanar line, but the optical waveguide is not located between the ground line and the common signal line on the other side (for example, refer to Fig. 1(a) of Non-Patent Document 1).

[0005] Prior art literature

[0006] Non-patent literature

[0007] Non-patent literature 1: Jianfeng Ding, Hongtao Chen, Lin Yang, Lei Zhang, Ruiqiang Ji, Yonghui Tian, ​​Weiwei Zhu, Yangyang Lu, Ping Zhou, Rui Min, and Mingbin Yu, Ultra-low-power carrier-depletion Mach-Zehnder silicon optical modulator, Optics Express, Vol. 20, No. 7 (2012). Summary of the invention

[0008] An optical modulator according to an embodiment of the present invention includes a substrate, a coplanar line arranged on the substrate, a waveguide, and an adjustment component. The coplanar line has a first ground line, a second ground line, and a signal line located between the first ground line and the second ground line and coupled to the first ground line and the second ground line respectively. When the substrate is viewed from above, the waveguide is located on the substrate along the coplanar line and between the first ground line and the signal line. The waveguide has: an input part for optical signals; an output part, which modulates and outputs the optical signal input from the input part by the signal transmitted in the coplanar line. When the substrate is viewed from above, the adjustment component is located on the substrate along the coplanar line and between the second ground line and the signal line. The adjustment component does not have an input part and an output part for optical signals.

[0009] An optical transceiver according to an embodiment of the present invention has an optical modulator and a light source for inputting an optical signal into the optical modulator. The optical modulator includes a substrate, a coplanar line arranged on the substrate, a waveguide, and an adjustment component. The coplanar line has a first ground line, a second ground line, and a signal line located between the first ground line and the second ground line and coupled to the first ground line and the second ground line respectively. When the substrate is viewed from above, the waveguide is located on the substrate along the coplanar line and between the first ground line and the signal line. The waveguide has: an input part for optical signals; an output part, which modulates and outputs the optical signal input from the input part by the signal transmitted in the coplanar line. When the substrate is viewed from above, the adjustment component is located on the substrate along the coplanar line and between the second ground line and the signal line. The adjustment component does not have an input part and an output part for optical signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a top view showing a structural example of an optical modulator according to one embodiment.

[0011] Figure 2 is along Figure 1 Section view along line AA.

[0012] Figure 3 It is a graph showing the frequency characteristics of the S parameter of the optical modulator of the comparative example.

[0013] Figure 4 This is a graph showing an example of the frequency characteristics of the S parameter of the optical modulator according to the present embodiment.

[0014] Figure 5 It is a plan view showing a structural example in which the adjustment member is divided and arranged.

[0015] Figure 6 This is a graph showing an example of the relationship between the filling factor of the adjustment member and the effective refractive index of the coplanar line.

[0016] Figure 7 is along Figure 5 Cross-sectional view along line BB.

[0017] Figure 8 This is a block diagram showing a configuration example of an optical transceiver according to an embodiment. DETAILED DESCRIPTION

[0018] In a coplanar line, when an optical waveguide is located on one side of a ground line and not on the other side of a ground line, the transmission efficiency of an optical signal transmitted in the optical waveguide is reduced due to resonance. It is necessary to improve the transmission efficiency of an optical signal in an optical waveguide. An optical modulator and an optical transceiver according to an embodiment of the present invention can improve the transmission efficiency of an optical signal.

[0019] (Configuration Example of the Light Modulator 10)

[0020] like Figure 1 and Figure 2 As shown, an optical modulator 10 of one embodiment includes a coplanar line 40, a waveguide 20, an adjustment member 30, and a substrate 50. It is assumed that the optical modulator 10 is held by the substrate 50. The optical modulator 10 further includes a first dielectric layer 51 and a second dielectric layer 52 provided on the substrate 50. The optical modulator 10 further includes a semiconductor layer 53 provided on the first dielectric layer 51.

[0021] The coplanar line 40 has a first grounding line 41 and a second grounding line 42 for grounding, and a signal line 43 for inputting an electrical signal. The first grounding line 41, the second grounding line 42, and the signal line 43 extend along the X-axis direction. The first grounding line 41 is electrically connected to the semiconductor layer 53 through a via wiring 411. The second grounding line 42 is electrically connected to the semiconductor layer 53 through a via wiring 421. The signal line 43 is electrically connected to the semiconductor layer 53 through a via wiring 431. The first grounding line 41, the second grounding line 42, and the signal line 43 are insulated from each other by a second dielectric layer 52. The signal line 43 is located between the first grounding line 41 and the second grounding line 42. The signal line 43 is electrically coupled to the first grounding line 41 and the second grounding line 42, respectively.

[0022] The waveguide 20 extends along the X-axis direction on the semiconductor layer 53. The waveguide 20 is electrically connected to the semiconductor layer 53. The waveguide 20 is located between the first ground line 41 and the signal line 43 of the coplanar line 40. When looking down on a plane (YZ plane) orthogonal to the direction (X-axis direction) in which the waveguide 20 extends (refer to Figure 2 ), the waveguide 20 is electrically connected to the first ground line 41 on the positive direction side of the Y axis, and is electrically connected to the signal line 43 on the negative direction side of the Y axis. As a result, the electrical signal between the signal line 43 and the first ground line 41 is applied to the waveguide 20 in a direction intersecting the direction in which the waveguide 20 extends (the X-axis direction).

[0023] The waveguide 20 has an input portion 21 and an output portion 22. The waveguide 20 transmits an optical signal input from the input portion 21, and outputs it from the output portion 22. While the optical signal is transmitted in the waveguide 20 between the first ground line 41 and the signal line 43, it is affected by an electrical signal applied to the waveguide 20 by the first ground line 41 and the signal line 43. The amplitude of the optical signal changes due to the influence of the electrical signal during the transmission in the waveguide 20. That is, the optical signal is modulated by the electrical signal transmitted in the coplanar line 40 and output from the output portion 22.

[0024] The adjustment member 30 extends along the X-axis direction on the semiconductor layer 53. The adjustment member 30 may be electrically connected to the semiconductor layer 53 or insulated from the semiconductor layer 53. The adjustment member 30 is located between the second ground line 42 and the signal line 43 of the coplanar line 40.

[0025] Although the substrate 50 is composed of silicon (Si) in the present embodiment, it is not limited thereto and may be composed of other semiconductor materials such as GaAs. The substrate 50 may also be composed of a conductor such as metal or a dielectric such as glass or resin. The substrate 50 is not limited to these examples and may be composed of various other materials.

[0026] The first dielectric layer 51 is formed of a silicon oxide film (SiO 2 ), but is not limited thereto and may be formed of other various dielectric materials or insulating materials.

[0027] The second dielectric layer 52 includes a silicon oxide film (SiO2), but is not limited thereto, and may be composed of various other dielectric materials or insulating materials. The second dielectric layer 52 may be composed of a gas such as air, or may be composed of a vacuum.

[0028] The semiconductor layer 53 may be composed of silicon (Si). The semiconductor layer 53 may also be composed of a material formed by injecting a dopant into a semiconductor. The semiconductor layer 53 may also be replaced by a conductor layer such as a metal.

[0029] The first ground line 41, the second ground line 42 and the signal line 43 may be made of metal such as aluminum, but are not limited thereto and may be made of other various conductive materials. The via wirings 411, 421 and 431 may be made of metal such as tungsten, but are not limited thereto and may be made of other various conductive materials.

[0030] The waveguide 20 and the adjustment member 30 are made of silicon (Si), but are not limited thereto and may be made of various other dielectric materials. The waveguide 20 and the adjustment member 30 may be made of the same material or different materials.

[0031] A portion of the waveguide 20 is surrounded by the second dielectric layer 52. The material of the waveguide 20 is specified so that the relative dielectric constant of the waveguide 20 is greater than the relative dielectric constant of the second dielectric layer 52. In other words, the materials of the waveguide 20 and the second dielectric layer 52 are specified so that the refractive index of the second dielectric layer 52 is greater than the refractive index of the waveguide 20. As a result, the optical signal transmitted in the waveguide 20 can be totally reflected at the boundary with the second dielectric layer 52. As a result, the loss of the optical signal transmitted in the waveguide 20 can be reduced.

[0032] The waveguide 20 is configured so that the signal line 43 and the first ground line 41 are not short-circuited by the waveguide 20. In other words, the waveguide 20 can be configured so that the resistance value between the side connected to the signal line 43 through the via wiring 431 and the semiconductor layer 53 and the side connected to the first ground line 41 through the via wiring 411 and the semiconductor layer 53 reaches a predetermined value or more. The resistance value can be adjusted by, for example, the concentration of the dopant of the semiconductor included in the waveguide 20, or by the resistance between the waveguide 20 and the coplanar line 40.

[0033] In the present embodiment, the waveguide 20 includes an n-type semiconductor located on the side connected to the signal line 43 and a p-type semiconductor located on the side connected to the first ground line 41. The n-type semiconductor and the p-type semiconductor extend in the direction (X-axis direction) in which the waveguide 20 extends, and are arranged in a row in a direction (Y-axis direction) intersecting the direction in which the waveguide 20 extends. The waveguide 20 has a pn junction formed by bonding an n-type semiconductor and a p-type semiconductor. The pn junction portion is arranged in the direction (X-axis direction) in which the waveguide 20 extends. Since the waveguide 20 has a pn junction, it is configured so that a bias voltage when a positive potential is applied to the ground potential of the first ground line 41 to the signal line 43 forms a reverse bias. As a result, the waveguide 20 is configured so that when the potential of the signal line 43 is a positive potential relative to the ground potential of the first ground line 41, the signal line 43 and the first ground line 41 are not short-circuited.

[0034] The adjustment member 30 may be configured to have a pn junction similar to the waveguide 20 , or may be configured to be composed solely of any one of an n-type semiconductor, a p-type semiconductor, or an intrinsic semiconductor.

[0035] (Control of Resonance Frequency in Optical Modulator 10)

[0036] As described above, the optical modulator 10 modulates the light input from the input section 21 to the waveguide 20 by applying an electrical signal to the coplanar line 40, and outputs the modulated light from the output section 22. If a line formed by pairing a ground line and a signal line is used instead of the coplanar line 40, the radiation of the signal increases. The optical modulator 10 of this embodiment can reduce the radiation of the signal by using the coplanar line 40. That is, by using the coplanar line 40, the loss of the signal can be reduced.

[0037] The transmission characteristics of the waveguide 20 of the optical modulator 10 are expressed as frequency characteristics of S parameters (Scattering Parameters). The S parameters of the waveguide 20 include: S12, which represents the ratio of light transmitted from the input part 21 to the output part 22; and S11, which represents the ratio of light input from the input part 21 and reflected inside the waveguide 20 and returned to the input part 21. In other words, the S parameters of the waveguide 20 include the transmittance and reflectance of the light input to the waveguide 20.

[0038] Among the light transmitted in the waveguide 20, light of a predetermined frequency resonates inside the waveguide 20 and is greatly lost. The predetermined frequency at which light resonates is also referred to as the resonance frequency. The resonance frequency changes with the shape of the waveguide 20. For example, the longer the line length of the waveguide 20, the lower the resonance frequency of the waveguide 20.

[0039] The waveguide 20 can be represented by an equivalent circuit including a capacitor and an inductor. The resonant frequency of the waveguide 20 can be associated with the equivalent circuit of the waveguide 20. The equivalent circuit of the waveguide 20 is affected by the configuration of the electrodes or dielectrics around the waveguide 20. Therefore, the resonant frequency changes according to the configuration of the electrodes or dielectrics around the waveguide 20.

[0040] Here, as a comparative example, it is assumed that the waveguide 20 of the optical modulator is located between the first ground line 41 and the signal line 43 but not between the second ground line 42 and the signal line 43. In this case, Figure 3 Graphs showing frequency characteristics of the S parameters of the waveguide 20 are shown. Figure 3 In the graph of , the horizontal axis represents the frequency of the optical signal transmitted in the waveguide 20, and the vertical axis represents the respective values ​​of S11 and S12. At the resonant frequency represented by FR, the value of S12 reaches a minimum. In other words, the transmittance of the signal of the resonant frequency becomes lower. Assume that SB represents the frequency band of the electrical signal input to the signal line 43 to modulate the optical signal in the optical modulator. If the resonant frequency (FR) is within the range of the frequency band (SB) of the electrical signal input to the signal line 43, the loss of a portion of the signal modulated by the optical modulator increases. As a result, the transmission characteristics of the optical modulator deteriorate.

[0041] On the other hand, the optical modulator 10 of the present embodiment includes the adjustment member 30 located between the second ground line 42 and the signal line 43. In this case, Figure 4 Graphs showing frequency characteristics of the S parameters of the waveguide 20 are shown. Figure 4In the graph, the horizontal axis represents the frequency of the optical signal transmitted in the waveguide 20, and the vertical axis represents the respective values ​​of S11 and S12. The value of S12 does not have a minimum value within the frequency band (SB) of the electrical signal input to the signal line 43. That is, in the optical modulator 10 of the present embodiment, resonance does not occur at least within the frequency band (SB) of the electrical signal. Therefore, the loss of the signal modulated by the optical modulator 10 of the present embodiment is less than the loss of the signal modulated by the optical modulator of the comparative example. As a result, the transmission characteristics of the signal modulated in the optical modulator 10 of the present embodiment can be improved.

[0042] As described above, the optical modulator 10 of the present embodiment includes the adjustment member 30 located between the second ground line 42 and the signal line 43, and thus can maintain the transmittance of the modulated signal at a high value within the frequency band (SB) of the electrical signal input to the signal line 43. As a result, the transmission characteristics of the modulated signal can be improved.

[0043] In addition, in the optical modulator 10 of the present embodiment, the adjustment member 30 does not have an input / output portion for an optical signal. Specifically, the adjustment member 30 does not have a structure corresponding to the input portion 21 and the output portion 22 of the waveguide 20. If the adjustment member 30 has an input / output portion for an optical signal, the coupling between the waveguide 20 and the adjustment member 30 may be enhanced. The enhanced coupling between the waveguide 20 and the adjustment member 30 may increase the influence of the adjustment member 30 on the optical signal transmitted in the waveguide 20. On the other hand, since the adjustment member 30 of the optical modulator 10 of the present embodiment does not have an input / output portion for an optical signal, the coupling between the waveguide 20 and the adjustment member 30 may be weakened. The weakened coupling between the waveguide 20 and the adjustment member 30 may reduce the influence of the adjustment member 30 on the optical signal transmitted in the waveguide 20. By reducing the influence from the adjustment member 30, the characteristics of the optical signal modulated in the waveguide 20 can be maintained. As a result, the transmission characteristics of the modulated signal can be improved. In addition, the fact that the adjustment member 30 has an input / output portion for an optical signal limits the length of the adjustment member 30. Since the adjustment member 30 does not have an input / output portion for an optical signal, the length of the adjustment member 30 can be adjusted as described later.

[0044] (Control of the Effective Refractive Index of the Light Modulator 10)

[0045] In the optical modulator 10, an optical signal is transmitted in a waveguide 20, and an electrical signal is transmitted in a coplanar line 40. Here, the transmission speed of the electrical signal in the coplanar line 40 needs to be matched with the transmission speed of the optical signal in the waveguide 20, so as to efficiently modulate the optical signal using the electrical signal. In order to match the transmission speed of the electrical signal with the transmission speed of the optical signal, the difference between the effective refractive index of the waveguide 20 and the effective refractive index of the coplanar line 40 needs to be reduced.

[0046] The effective refractive index of the coplanar line 40 can be adjusted by adjusting the length of the member 30 in the extension direction (X-axis direction). Figure 5 As illustrated, the length of the adjustment member 30 in the extension direction (X-axis direction) can be adjusted by dividing the adjustment member 30 into a plurality of parts. Figure 5 In the embodiment, the adjusting member 30 includes the adjusting member 31, the adjusting member 32 and the adjusting member 3n which are divided into n parts. The adjusting member 30 may be shortened without being divided, while maintaining one adjusting member 30.

[0047] The effective refractive index of the coplanar line 40 is determined according to the ratio of the length of the adjustment member 30 to the length of the waveguide 20. The ratio of the length of the adjustment member 30 to the length of the waveguide 20 is also referred to as the filling rate of the adjustment member 30. The filling rate is calculated by dividing the total length of the adjustment member 30 by the length of the waveguide 20. Assume that L represents the length of the waveguide 20. The lengths of the n adjustment members 30 are represented by L1, L2, ..., Ln, respectively. In this case, the filling rate of the adjustment member 30 is calculated by (L1+L2+...+Ln) / L. In the case where one adjustment member 30 is shortened, the filling rate of the adjustment member 30 is calculated by dividing the shortened length of the adjustment member 30 by the length of the waveguide 20.

[0048] If the adjustment member 30 is divided by a plane perpendicular to the extension direction of the adjustment member 30, the length of each part of the divided adjustment member 30 is consistent with the length in the extension direction. If the adjustment member 30 is divided by a plane inclined from the plane perpendicular to the extension direction of the adjustment member 30, the length of each part of the divided adjustment member 30 can be calculated as the length in the extension direction in the orthographic projection of the waveguide 20.

[0049] exist Figure 6 The relationship between the filling rate of the adjustment member 30 and the effective refractive index of the coplanar line 40 is shown in a curve graph. Figure 6 In the graph of FIG. 1 , the horizontal axis represents the filling rate of the adjustment member 30, and the vertical axis represents the effective refractive index of the coplanar line 40. The smaller the filling rate of the adjustment member 30, the lower the effective refractive index of the coplanar line 40. Therefore, the filling rate of the adjustment member 30 can be adjusted so that the effective refractive index of the coplanar line 40 is close to the effective refractive index of the waveguide 20.

[0050] The total length of the adjustment member 30 (the filling rate of the adjustment member 30) may affect the resonance frequency of the optical signal in the waveguide 20. The total length of the adjustment member 30 in the direction along the coplanar line 40 (the filling rate of the adjustment member 30) can be set so that the resonance frequency of the optical signal transmitted in the waveguide 20 is higher than the frequency band (SB) of the electrical signal transmitted in the signal line 43. As a result, the loss of the signal modulated by the electrical signal becomes small. As a result, the transmission characteristics of the signal modulated in the optical modulator 10 can be improved.

[0051] If the adjustment member 30 is divided into a plurality of parts, the arrangement of the divided parts in the X-axis direction has little effect on the effective refractive index of the coplanar line 40. Therefore, the parts formed by dividing the adjustment member 30 can be arranged at any position in the X-axis direction.

[0052] like Figure 7 As shown, the optical modulator 10 may further include a temperature adjustment portion 54. The temperature adjustment portion 54 may be located inside the substrate 50 or below the substrate 50. The characteristics of the waveguide 20 or the coplanar line 40 may be affected by the temperature of the substrate 50. Therefore, the optical modulator 10 may use the temperature adjustment portion 54 to adjust the temperature of the substrate 50 so as to stabilize the characteristics.

[0053] The temperature adjustment unit 54 may be configured to include, for example, a radiator. The temperature adjustment unit 54 may also be configured to include a heater for heating the substrate 50. The temperature adjustment unit 54 may also be configured to include a cooling water pipe for cooling the substrate 50. The temperature adjustment unit 54 may also be configured to include a pipe for circulating water or the like at a predetermined temperature so as to control the temperature of the substrate 50 to a predetermined temperature.

[0054] In the optical modulator 10, the adjustment member 30 can absorb a part of the optical signal transmitted in the waveguide 20 and generate heat. At least a part of the parts formed by dividing the adjustment member 30 is as follows: Figure 7 As shown, it can be arranged to overlap with the temperature adjustment section 54 when the substrate 50 is viewed from above (when the substrate 50 is viewed from the positive direction of the Z axis). This makes it easy to adjust the temperature of the substrate 50. As a result, the characteristics of the optical modulator 10 can be stabilized.

[0055] (summary)

[0056] As described above, the optical modulator 10 of this embodiment includes the adjustment member 30 in addition to the waveguide 20 provided along the coplanar line 40, so that the resonance frequency of the waveguide 20 can be adjusted to a frequency outside the frequency band of the electrical signal (the frequency band of the modulated optical signal). As a result, the transmission characteristics of the signal modulated in the optical modulator 10 can be improved.

[0057] (Configuration Example of Optical Transceiver 100)

[0058] The light modulator 10 can be used in combination with a structure that transmits and receives light. Figure 8 As shown, the optical transceiver 100 includes an optical modulator 10, a light source 110, a signal input unit 120, and an isolator 130. The optical transceiver 100 inputs an optical signal from the light source 110 to the optical modulator 10, modulates the light according to the signal input to the signal input unit 120 by the optical modulator 10, and outputs the modulated light from the optical modulator 10 to the receiver 140 via the isolator 130. The isolator 130 is configured so that the transmittance of the optical signal transmitted from the light source 110 to the receiver 140 is greater than the transmittance of the optical signal transmitted from the receiver 140 to the light source 110. As a result, the optical signal is less likely to be incident on the light source 110. As a result, the light source 110 is protected.

[0059] The light source 110 may be configured to include a semiconductor laser such as an LD (Laser Diode) or a VCSEL (Vertical Cavity Surface Emitting LASER). The light source 110 may be configured to include a device that emits light signals of various wavelengths not limited to visible light. The light source 110 may be formed on the substrate 50 together with the optical modulator 10.

[0060] The optical modulator 10 modulates light by changing the intensity of light input from the light source 110 to the waveguide 20 according to a signal input from the signal input section 120 to the signal line 43 of the coplanar line 40. The optical modulator 10 may be located between the isolator 130 and the receiver 140, rather than between the light source 110 and the isolator 130. The optical modulator 10 may, for example, pulse modulate an optical signal. The signal input section 120 receives an input of a signal from an external device or the like. The signal input section 120 may, for example, include a D / A converter. The signal input section 120 outputs a signal to the signal line 43 of the coplanar line 40 of the optical modulator 10.

[0061] Although the embodiments of the present invention have been described according to the drawings and embodiments, it should be noted that those skilled in the art can make various deformations or changes according to the present invention. Therefore, it should be noted that these deformations or changes are included in the scope of the present invention. For example, the functions included in each structural part can be reconfigured in a logically non-contradictory manner, and multiple structural parts can be combined into one or divided. It should be understood that the scope of the present invention also includes these contents.

[0062] In the present invention, the records of "first" and "second" etc. are identifiers used to distinguish the structure. The structures distinguished by the records of "first" and "second" etc. in the present invention can exchange the numbers of the structures. For example, the first grounding wire 41 can exchange "first" and "second" as identifiers with the second grounding wire 42. The exchange of identifiers is carried out simultaneously. The structures can still be distinguished after exchanging the identifiers. The identifiers can be deleted. The structures after deleting the identifiers are distinguished by the figure marks. The order of the structures should not be interpreted only based on the records of the identifiers of the present invention such as "first" and "second", or as the basis for the existence of identifiers with small numbers.

[0063] In the present invention, the X-axis, Y-axis and Z-axis are set for convenience of description and can be replaced with each other. The structure of the present invention has been described using an orthogonal coordinate system consisting of the X-axis, Y-axis and Z-axis. The positional relationship of each structure of the present invention is not limited to an orthogonal relationship.

[0064] Description of Reference Numerals

[0065] 10 Optical Modulator

[0066] 20 waveguide (21: input part, 22: output part)

[0067] 30, 31, 32, 3n adjustment components

[0068] 40 coplanar line (41: first ground line, 42: second ground line, 43: signal line)

[0069] 50 substrate (51, 52: dielectric layer, 53: semiconductor layer, 54: temperature adjustment unit)

[0070] 100 optical transceiver (110: light source, 120: signal input unit, 130: isolator, 140: receiver)

Claims

1. An optical modulator comprising: substrate; A coplanar circuit, arranged on the substrate, comprising a first ground line, a second ground line and a signal line, wherein the signal line is located between the first ground line and the second ground line and is coupled to the first ground line and the second ground line respectively; a waveguide, which is located on the substrate along the coplanar line and between the first ground line and the signal line when the substrate is viewed from above, and has an input part and an output part for optical signals, wherein the output part modulates the optical signal input from the input part using the signal transmitted in the coplanar line and outputs the modulated optical signal; as well as The adjustment component is located on the substrate along the coplanar line and between the second ground line and the signal line when the substrate is viewed from above, and has no input part and output part for optical signals.

2. The optical modulator according to claim 1, wherein The adjustment member is shorter than the waveguide in a direction along the coplanar line.

3. The optical modulator according to claim 2, wherein: The adjusting member is divided into a plurality of parts.

4. The optical modulator according to claim 3, wherein: The optical modulator further comprises: a temperature adjustment unit located inside the substrate or below the substrate, When the substrate is viewed in plan, at least a portion of the portion formed by dividing the adjustment member is provided to overlap with the temperature adjustment portion.

5. The optical modulator according to any one of claims 2 to 4, wherein: The total length of the adjustment member in the direction along the coplanar line is set so that the resonance frequency of the optical signal transmitted in the waveguide is higher than the frequency band of the signal transmitted in the signal line.

6. An optical transceiver, comprising: an optical modulator; and A light source, inputting an optical signal to the light modulator, The light modulator has: substrate; A coplanar circuit, arranged on the substrate, comprising a first ground line, a second ground line and a signal line, wherein the signal line is located between the first ground line and the second ground line and is coupled to the first ground line and the second ground line respectively; a waveguide, which is located on the substrate along the coplanar line and between the first ground line and the signal line when the substrate is viewed from above, and has an input part and an output part for optical signals, wherein the output part modulates the optical signal input from the input part using the signal transmitted in the coplanar line and outputs the modulated optical signal; as well as The adjustment component is located on the substrate along the coplanar line and between the second ground line and the signal line when the substrate is viewed from above, and has no input part and output part for optical signals.

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