JP2020091378A - Optical modulator - Google Patents

Abstract

To provide an optical modulator capable of reducing electric loss in a wiring part of a control electrode, suppressing electric field application to an optical waveguide by the wiring part and crosstalk between electric signals, and further preventing heat generated by a driver element disposed on a relay substrate from propagating to an action part of the optical modulator.SOLUTION: The optical modulator comprises: a housing 7 storing therein an electro-optic substrate 1 on which an optical waveguide 2 and a control electrode 30 are formed, and relay substrates (5, 51, 52) on which trunk line routes (501, 511, 521) are formed; an electric signal input part arranged on one short side of the housing (left in Fig. 2); and a light input part and a light output part arranged on the other short side of the housing (right in Fig. 2). The relay substrate 5 includes a driver element 60, and a relay substrate portion 51 arranged along one long side of the electro-optic substrate 1. The trunk line route is electrically connected to the control electrode at the one long side.SELECTED DRAWING: Figure 2

Description

The present invention relates to an optical modulator, and in particular, includes an electro-optical substrate on which an optical waveguide and a control electrode are formed, and a driver element which relays an electric signal to the control electrode and amplifies at least a part of the electric signal. The present invention relates to an optical modulator that houses a relay board in a housing.

Various optical modulators are widely used in the fields of optical communication and optical measurement. An optical modulator in which a plurality of Mach-Zehnder type optical waveguides are integrated on a single substrate has been proposed as a modulation signal has a wider band and multi-valued.

Further, there is a demand for multi-functionalization of the module including the optical modulator and miniaturization of the entire module. For example, an optical modulation element incorporating an optical waveguide or a control electrode and a relay substrate for supplying an electric signal to the control electrode around the optical modulation element are arranged in one case and an electric signal is supplied to the case. An optical modulator having an electric signal input section and an optical input/output section for inputting/outputting a light wave to/from an optical modulator has also been proposed.

Patent Document 1 proposes a semiconductor optical modulator using polarization combining means as shown in FIG. An optical waveguide 2 is formed on a semiconductor chip 1 having an electro-optical effect, and is housed in a housing 7 together with a relay substrate 5. At the input end of the optical waveguide 2, the input light from the optical fiber L1 is incident on the input waveguide 20 on the chip 1 via the collimator lens L2, the reflecting means L3 and the condenser lens L4. The two light waves emitted from the output waveguides (21, 22) on the chip 1 are light collimating lenses (L5, L7), a wave plate (polarization rotator) L6, a reflecting means L8, and a polarization combining means. (Polarization beam splitter) L9 combines the polarized waves, and enters the optical fiber L11 via the condenser lens L10.

A modulation signal, which is a part of an electric signal, is applied to a modulation electrode (control electrode) 3 for modulating a light wave propagating through an optical waveguide 2 formed on the semiconductor chip 1. A modulation signal from a signal source (not shown) outside the housing 7 is introduced into the housing through an electric signal input section (S is a signal terminal and G is a ground terminal). Further, an electric signal such as a modulation signal passes through the relay line 501 formed on the relay substrate 5 and reaches the control electrode 3 formed on the electro-optical substrate 1 (hereinafter also referred to as the electro-optical substrate 1) which is a light modulation element. Is applied. In FIG. 1, the control electrode 3 is indicated by a dotted line in order to make it easy to distinguish the display of the optical waveguide 2 from the display of the control electrode 3. At the end of the control electrode 3, a terminating element 4 such as a resistor is arranged to terminate the modulated signal.

As shown in FIG. 1, when the housing 7 has a rectangular shape in a plan view and the electro-optical substrate 1 also has a rectangular shape, the longitudinal direction of the housing 7 is substantially the same as the longitudinal direction of the substrate 1. It is common to arrange the both so as to be oriented. In this case, when the electric signal input section is arranged on one short side (left side in FIG. 1) of the housing 7, as shown in FIG. 1, the electric signal input section, the relay board 5, and the electro-optical unit are arranged from the short side. The substrates 1 are arranged in this order. Since the relay substrate 5 is arranged on the short side of the electro-optical substrate 1, it is necessary to connect the relay line 501 and the control electrode (modulation electrode) 3 on the short side of the electro-optical substrate 1. As a result, as shown in the section S, the portion of the control electrode 3 other than the acting portion (the portion that applies an electric field to the optical waveguide) (wiring portion up to the acting portion) becomes longer, and moreover, the plurality of control electrodes are close to each other. It will be placed.

As described above, when the wiring portions of the control electrodes adjacent to each other become long, not only the electric loss in the wiring portions increases, but also an unnecessary electric field formed by the wiring portions is applied to the optical waveguide or propagates through the wiring portions. This causes a problem such as electrical crosstalk caused by a plurality of electrical signals that occur between the control electrodes.

On the other hand, the relay substrate 5 of FIG. 1 is provided with the driver element 6 for amplifying the modulation signal. The driver element also generates a large amount of heat, and the temperature of the relay substrate easily rises. The heat from the relay substrate 5 is easily conducted to the electro-optical substrate 1 arranged in the housing together with the relay substrate, the temperature of the electro-optical substrate 1 rises, and a phenomenon such as temperature drift occurs.

Further, as shown in FIG. 1, when the wiring part of the control electrode is locally dense, the control electrode (signal electrode, ground electrode, etc.) itself becomes a heat conduction medium, and the substrate temperature of the action part and its vicinity is increased. Will be more likely to rise.

JP, 2014-164243, A

The problem to be solved by the present invention is to solve the above-mentioned problems and to reduce the electrical loss in the wiring portion of the control electrode even when the electric signal input portion is arranged on the short side of the housing, and to reduce the wiring. An object of the present invention is to provide an optical modulator that suppresses an electric field applied to an optical waveguide by a part and crosstalk between electric signals. Another object of the present invention is to provide an optical modulator capable of suppressing the heat generated by the driver element arranged on the relay board from being conducted to the acting portion of the optical modulator.

In order to solve the above problems, the optical modulator of the present invention has the following technical features.
(1) A substrate having an electro-optical effect and having a rectangular shape in a plan view, on which an optical waveguide and a control electrode for conducting an electric signal for controlling a light wave propagating in the optical waveguide are formed. An electro-optical substrate, a relay substrate on which a relay line for relaying the electric signal to the control electrode is formed, the electro-optical substrate and the relay substrate are housed inside, and the shape in plan view is rectangular. A casing, an electric signal input unit arranged on one short side of the casing for inputting the electric signal, and an optical input unit and an optical output unit arranged on the other short side of the casing. At least a part of the relay substrate is arranged on one short side of the electro-optic substrate, and a part of the electrical signal is amplified on the relay substrate. A driver element for driving the modulator is arranged, the relay board has a portion arranged along one long side of the electro-optic board, and the relay line and the control electrode are the electro-optic board. Is electrically connected on the one long side of the above.

(2) In the optical modulator described in (1) above, the relay board includes a portion arranged along the other long side of the electro-optic board, and the relay line and the control electrode are electrically connected. The other long side of the optical substrate is also electrically connected.

(3) In the optical modulator described in (2) above, in the optical waveguide, at least four Mach-Zehnder waveguides are arranged side by side in the short side direction of the electro-optical substrate, and the center in the short side direction. The Mach-Zehnder type waveguide closer to is closer to one short side of the electro-optical substrate on which the relay substrate is disposed.

(4) In the optical modulator according to (1), the control electrode has a modulation electrode for applying a high frequency signal to the optical waveguide and a DC electrode for applying a DC voltage to the optical waveguide, The relay substrate includes a portion arranged along the other long side of the electro-optical substrate, and the relay line and the modulation electrode are electrically connected on the one long side of the electro-optical substrate. The relay line and the DC electrode are electrically connected on the other long side of the electro-optical substrate.

(5) In the optical modulator described in (1) above, the control electrode has a modulation electrode for applying a high frequency signal to the optical waveguide and a DC electrode for applying a DC voltage to the optical waveguide, The relay substrate includes a portion arranged along the other long side of the electro-optical substrate, and the relay line, the modulation electrode, and the relay line and the DC electrode are provided on the one side of the electro-optical substrate. It is characterized in that it is electrically connected to both the long side and the other long side.

(6) In the optical modulator described in any one of (1) to (5) above, the relay substrate is formed of one substrate.

(7) In the optical modulator according to any one of (1) to (5) above, the relay substrate includes a portion disposed on the one short side of the electro-optical substrate and the electro-optical substrate. The portion arranged along the long side is characterized in that it is constituted by a separate and separate substrate.

(8) In the optical modulator described in the above (7), the driver element is arranged in a portion of the relay substrate arranged on one short side of the electro-optical substrate.

(9) In the optical modulator described in (7) above, the thermal conductivity of the relay substrate on which the driver element is disposed is the thermal conductivity of the relay substrate disposed along the long side of the electro-optical substrate. It is characterized by being set higher than.

(10) In the optical modulator according to any one of (1) to (9), the driver element and the driver element are provided on a back surface of a relay substrate arranged along one short side of the electro-optical substrate. A groove is formed between the electro-optical substrate and the electro-optical substrate.

(11) In the optical modulator described in any one of (1) to (10) above, a plurality of irregularities are formed on the outside of the housing located near the driver element. ..

The present invention is a substrate having an electro-optical effect and having a rectangular shape in a plan view, on which an optical waveguide and a control electrode for conducting an electric signal for controlling a light wave propagating through the optical waveguide are formed. Electro-optical substrate, a relay substrate on which a relay line for relaying the electric signal to the control electrode is formed, the electro-optical substrate and the relay substrate are housed inside, and the shape in plan view is rectangular. Of the housing, an electric signal input section arranged on one short side of the case for inputting the electric signal, and an optical input section and an optical output section arranged on the other short side of the case. In the optical modulator consisting of, at least a part of the relay board is arranged on one short side of the electro-optic board, and a part of the electric signal is amplified on the relay board. A driver element for driving the optical modulator is arranged, the relay substrate has a portion arranged along one long side of the electro-optical substrate, and the relay line and the control electrode are the electro-optical substrate. Since the one long side of the substrate is electrically connected, it is possible to reduce the electrical loss in the wiring portion of the control electrode and suppress the electric field application to the optical waveguide by the wiring portion and the crosstalk between electric signals. Further, it is possible to provide the optical modulator capable of suppressing the heat generation of the driver element arranged on the relay substrate from being conducted to the acting portion of the optical modulator.

It is a figure which shows an example of the conventional optical modulator. It is a figure explaining 1st Example which concerns on the optical modulator of this invention. It is a figure explaining 2nd Example which concerns on the optical modulator of this invention. It is a figure explaining 3rd Example which concerns on the optical modulator of this invention. It is a figure explaining 4th Example which concerns on the optical modulator of this invention. It is sectional drawing in the arrow X-X' of FIG. It is a figure explaining 5th Example which concerns on the optical modulator of this invention. It is a figure explaining 6th Example which concerns on the optical modulator of this invention. It is a figure explaining 7th Example which concerns on the optical modulator of this invention.

Hereinafter, the optical modulator of the present invention will be described in detail with reference to suitable examples.
As shown in FIGS. 2 to 5, the optical modulator of the present invention is a substrate having an electro-optical effect and having a rectangular shape in a plan view, and an optical waveguide 2 and an optical wave propagating through the optical waveguide on the substrate. And an electro-optical substrate 1 on which control electrodes (30 to 33) for transmitting electric signals for controlling the electric signals are formed, and relay lines (501, 511, 521, 531, for relaying the electric signals to the control electrodes). 541, 551, 561, 562) formed on the relay board (5, 51, 52, 53, 54, 55, 56), and the electro-optical board and the relay board housed inside and having a plan view shape. Is a rectangular casing 7, an electric signal input section for arranging the rectangular casing 7 on one short side (left side of FIG. 2) of the casing and inputting the electric signal, and the other short side of the casing (see FIG. 2) (a right side of 2), an optical modulator including an optical input unit and a light output unit, at least a part of the relay substrate is disposed on one short side of the electro-optical substrate. A driver element (60, 61) for amplifying a part of the electric signal and driving the optical modulator is arranged on the upper side, and the relay substrate is arranged along one long side of the electro-optical substrate. The relay line and the control electrode are electrically connected on the one long side of the electro-optical substrate.

Examples of the electro-optical substrate 1 having an electro-optical effect used in the optical modulator of the present invention include crystalline materials such as lithium niobate (LN), lithium tantalate, and lanthanum zirconate titanate (PLZT), and semiconductors such as InP. A substrate can be used. As a method of forming the optical waveguide, for example, a method of thermally diffusing a high refractive index substance such as titanium (Ti) on a lithium niobate substrate (LN substrate) or a proton exchange method is used. It is also possible to form the electro-optic substrate 1 by forming irregularities like a ridge type waveguide.

The control electrode includes a modulation electrode that applies an electric field based on a modulation signal to the optical waveguide and a DC electrode that applies an electric field based on a DC bias voltage. These control electrodes can be formed by forming a Ti/Au electrode pattern on the surface of the substrate and then using a gold plating method or the like. Further, if necessary, it is possible to provide a buffer layer such as a dielectric SiO _{2 on the} surface of the electro-optical substrate after the optical waveguide is formed. 2 to 5, the control electrode formed on the electro-optical substrate 1 is indicated by a bold solid line or dotted line in order to distinguish it from the optical waveguide. Further, in order to make it easier to see the positional relationship between the optical waveguide and the control electrode, the ground electrode is omitted.

The material of the relay substrate is not particularly limited, but for example, a ceramic substrate using Al ₂ O ₃ , AlN, or the like, an epoxy resin substrate (PPE: polyphenylene ether, etc.) based on a glass cloth base material, a sapphire substrate, A quartz substrate can be used.

The feature of the optical modulator according to the present invention is that, as shown in FIG. 2, when the electro-optical substrate 1 having a rectangular shape in a plan view is used as a light modulation element, the electro-optical substrate 1 is also viewed in a plan view. Is accommodated in a housing 7 having a rectangular shape. An electric signal input unit for inputting an electric signal is provided on one short side (left side in FIG. 2) of the housing 7, and a light input/output unit is arranged on the other short side (right side in FIG. 2). is doing.

The method of introducing the input light into the optical waveguide 2 of the electro-optical substrate 1 is as shown in FIG. 2 in which the input light from the optical fiber L1 is passed through the condenser lens L12 and the reflecting means L13 and L14. It is incident on the beam No. 2, but is not limited to this. Alternatively, the spatial optical system shown in FIG. 1 can be used. In addition to forming the input portion of the optical waveguide on the short side of the electro-optical substrate 1 as shown in FIG. 2, the input portion of the optical waveguide is formed on the long side of the electro-optical substrate 1 as shown in FIG. It can also be formed.

The method of deriving the output light emitted from the electro-optical substrate 1 to the outside of the housing 7 is, for example, a condenser lens (L15, L17), a wave plate (polarization rotator) L6, a reflecting means L8, and a polarization combining means. (Polarization beam splitter) The polarized light beams are combined by L9 and incident on the optical fiber L11. Of course, it is also possible to employ a spatial optical system using collimator lenses (L5, L7) as shown in FIG. Further, the optical modulator of the present invention is not limited to the polarization-combining type optical modulator, and the output light from a plurality of Mach-Zehnder type optical waveguides is integrated into one and output from the electro-optical substrate 1. It is also possible to adjust.

Further, in the optical modulator of the present invention, as shown in FIG. 2, the relay board (5, 51, 52) is arranged in the housing 7, and the electric signal from the electric signal input section is controlled by the electro-optical board 1. A relay line for transmitting to the electrodes is formed on the relay substrate. Further, a driver element 60 for amplifying a modulation signal which is an electric signal and applying it to a control electrode (modulation electrode) of the electro-optical substrate 1 is arranged on the relay substrate 5. The driver element 60 is preferably arranged at a position as close to the electric signal input portion as possible. Specifically, the relay board on the side where the electric signal input is arranged on the short side of the electro-optical board 1. Is used.

In the optical modulator of the present invention, in addition to the relay substrate 5 arranged on the short side of the electro-optical substrate 1, the relay substrate portion (51, 51, 52). By providing the relay substrate portion arranged along the long side of the electro-optical substrate 1, the wiring portion of the control electrode arranged in the section S of the electro-optical substrate 1 as shown in FIG. 1 is omitted. Therefore, it is possible to prevent the portion (wiring portion up to the acting portion) other than the acting portion (the portion for applying an electric field to the optical waveguide) of the control electrode from being unnecessarily long.

Since the wiring portion of this section S is wired as the relay line 511 of the relay substrate portion 51 or the relay line 521 of the relay substrate portion 52, the electrical loss can be reduced, and the wiring portion as shown in FIG. It is possible to suppress the electric field application and crosstalk between electric signals. Further, it is possible to suppress the heat generation of the driver element 60 arranged on the relay substrate 5 from being conducted to the acting portion of the electro-optical substrate 1 via the wiring portion of the control electrode.

In FIG. 2, the optical path of the input light when the input light passes between the reflecting means L13 and the reflecting means L14 overlaps with the relay substrate 51. Moreover, since the optical waveguide 2 on which the input light is incident and the control electrode for inputting the electric signal are both formed on the surface of the electro-optical substrate 1, the plane through which the input light passes and the surface of the relay substrate are almost the same. It becomes the same plane.
Therefore, in order to prevent interference between the input light and the relay substrate (for example, 51), the following configuration can be adopted.
Note that the height direction of each substrate in the following configuration is perpendicular to the paper surface of FIG.
(1) The height of the relay substrate at the portion where the input light interferes with the relay substrate 51 (between the reflecting means L13 and L14) is lower than the other portions of the same relay substrate 51.
(2) The height of the relay board 51 that interferes with the input light is lower than the height of the other relay boards (5 or 52). (The surface heights of the other relay boards and the electro-optical board 1 are substantially the same)
(3) All the relay boards (51, 5 and 52) have the same height and are lower than the height of the electro-optic board 1.
(4) All the relay boards (51, 5 and 52) and the electro-optical board 1 have the same height, and the input light passes through a position higher than the relay board. In this case, the reflecting means L14 is replaced with a reflecting means that reflects in the depth direction perpendicular to the drawing and then further reflects in the right direction in the drawing.
(5) As a result of adopting the above (2), the height is different between the relay substrates (between the relay substrates 5 and 51) or at the wire bonding portion between the relay substrate 51 and the electro-optical substrate 1, so that the height is high. A three-dimensional wiring board is arranged on the low-relay relay board 51, and the heights of the wire bonding portions are made uniform.

The relay substrates and the relay substrate and the electro-optical substrate 1 are electrically connected by wire bonding portions. If the heights of the substrates to be wire-bonded are different, the high-frequency characteristics are deteriorated. Therefore, it is preferable to make the heights of the substrates at the wire-bonding portions as uniform as possible.
Further, the optical system can be simplified and alignment can be facilitated by using a reflecting member having one reflection as in L14 of FIG. 2 rather than the reflecting member performing a plurality of reflections as in the above (4). become.

In the optical modulator of the present invention, the relay substrate portion arranged along the long side of the electro-optical substrate 1 can be arranged on both of the two long sides as shown in FIG. As shown in FIG. 3, it is possible to arrange the relay board portion 53 along only one long side of the electro-optic substrate 1 and collect all the relay lines 531 in the relay board portion.

The relay substrate may be formed of one substrate 54 as shown in FIG. 4, or the relay substrate portion 5 arranged on one short side of the electro-optical substrate 1 as shown in FIG. It is also possible to form the relay board parts (51, 52) arranged along the long side of the electro-optic board 1 by separate boards. When the relay board is formed by one relay board, the assembly process can be simplified. When the relay board is formed by another body, the heat generated in the driver element is transferred through the relay board to the electro-optical board 1. It is possible to suppress the conduction to the.

Furthermore, in the case where a plurality of Mach-Zehnder type optical waveguides are arranged in parallel in the optical waveguide formed on the electro-optical substrate 1, in FIGS. 1 and 4, the tip portions of all the Mach-Zehnder type optical waveguides are arranged in the longitudinal direction. They are arranged in line. Not limited to this, as shown in FIG. 2, at least four Mach-Zehnder waveguides (M1 to M4) are arranged side by side in the short-side direction of the electro-optical substrate 1 and close to the center in the short-side direction. The Mach-Zehnder waveguide can be arranged closer to one short side (left side in FIG. 2) of the electro-optical substrate 1 on which the relay substrate 5 is arranged.

Further, as shown in FIG. 3, the Mach-Zehnder type optical waveguide that is farther from the relay substrate portion 53 arranged along the longer side of the electro-optical substrate 1 has one shorter side (FIG. It is also possible to arrange it so as to be close to (left side of 3). By arranging the Mach-Zehnder type optical waveguide as shown in FIG. 2 or 3, the length of the wiring portion (wiring from the input end portion to the action portion) of the control electrode in the electro-optical substrate 1 can be further shortened. It will be possible.

In FIG. 5, not only the modulation electrode 33 for applying a high frequency signal to the optical waveguide 2 but also a DC electrode 34 for applying a DC voltage to the optical waveguide 2 is provided as a control electrode. A relay line 551 connected to the modulation electrode 33 is provided in the relay substrate portion 55 arranged along one long side of the electro-optical substrate 1, and a relay line arranged along the other long side is provided. A relay line 561 connected to the DC electrode 34 is provided on the substrate portion 56.

Reference numeral 61 in FIG. 5 is a microcontroller provided on the relay substrate 5, and controls the bias voltage, the voltage of the dither signal superimposed on the bias voltage, and the like.
In FIG. 5, the microcontroller 61 and the driver element 60 are arranged independently of each other, but the microcontroller 61 and the driver element 60 are electrically connected on the relay substrate 5, and the output voltage from the driver element 60 is controlled by the micro controller. You may make it control by the controller 61.
Comparing such a configuration with the case where the microcontroller 61 is arranged outside the casing 7, it is not necessary to input an electric wire connecting the microcontroller 61 and the driver element 60 to the casing 7, so that the casing 7 is not required. The number of electrical input parts of is reduced. This can increase the degree of freedom in designing other electric wiring outside the housing.
Further, since the electric wiring between the microcontroller 61 and the driver element 60 can be shortened, it is possible to reduce external noise to the control signal output from the microcontroller 61. This makes it possible to suppress the deterioration of the high frequency characteristics of the optical modulator.
Note that the portion denoted by reference numeral 61 in FIG. 5 may be a simple wiring having no microcontroller function. In this case, the microcontroller 61 that controls the bias is arranged outside the housing 7.

In addition, a plurality of relay lines connected to the modulation electrode and the DC electrode are provided in the relay substrate portion arranged along the two long sides of the electro-optical substrate 1 like the relay lines (511 and 521) in FIG. It is also possible to arrange them separately.

Next, the driver element 60 arranged on the relay board 5 simultaneously amplifies a plurality of modulated signals, and therefore the amount of heat generated increases. For example, in a part of the relay substrate 5, there is a region where the temperature exceeds 100° C. locally. When this heat generation is conducted to the acting portion of the electro-optical substrate 1 (the portion where the electric field by the control electrode is applied to the optical waveguide), the temperature drift phenomenon is likely to occur. Therefore, it is necessary to control the conduction of heat generated by the driver element or to efficiently discharge the generated heat to the outside.

As shown in FIGS. 2, 4 and 5, the driver element 60 is arranged on the relay substrate portion 5 arranged on one short side of the electro-optical substrate 1. This makes it possible to dispose the driver element, which is a heat source, at a position away from the acting portion of the electro-optical substrate 1.

As shown in FIG. 2, the thermal conductivity of the relay substrate portion 5 in which the driver element 60 is disposed is the thermal conductivity of the relay substrate portion (51, 52) disposed along the long side of the electro-optical substrate 1. By setting it higher than that, it is possible to suppress the amount of heat generated in the driver element from being conducted to the acting portion of the substrate 1 via the relay substrate portions (51, 52). Moreover, the amount of heat accumulated in the relay board portion 5 can be positively released to the outside through the housing 7 faster than it can be conducted to the other relay board portions (51, 52). Therefore, it is possible to suppress the temperature rise of the working portion of the electro-optical substrate 1.

FIG. 6 is a cross-sectional view taken along the arrow X-X' in FIG. As can be seen from FIG. 6, the amount of heat generated in the driver element 60 is either conducted through the relay substrate portion 5 or conducted through the housing 7.

With respect to the amount of heat conducted through the relay substrate portion 5, as shown in FIG. 7, a groove 50 is provided on the back surface of the relay substrate portion 5 between the driver element 60 in the relay substrate portion 5 and the electro-optical substrate 1. .. With such a groove, the thickness of the conductive substrate is locally thinned, and heat conduction can be suppressed.

Further, as shown in FIG. 6, when an optical component such as a prism (L14) is arranged between the relay substrate portion 5 and the electro-optical substrate 1, the amount of heat from the driver element is also conducted to the optical component. However, this causes a change in the optical axis of the optical component. Also, the input loss of the light wave due to the change of the optical axis becomes large. In such a case, the amount of heat conducted to the optical component side can be reduced by the groove 50 on the back surface of the relay substrate portion 5 as shown in FIG.

As another method of suppressing the conduction of the amount of heat from the driver element, it is possible to provide the groove 70 on the bottom surface of the housing 7 as shown in FIG. Further, by disposing the relay substrate portion 5 so as to project above the groove 70, it is possible to suppress heat conduction from the relay substrate portion 5 to the optical component (L14) or the electro-optical substrate 1. It is effective to form the groove 70 not only on the inner surface side of the housing 7 but also on the outer surface side (outer bottom surface of the housing).
Although the groove 70 is formed here so that the relay substrate portion 5 projects above the groove 70, a groove is formed between the relay substrate portion 5 and the electro-optical substrate 1 so that the relay substrate portion 5 does not project. You may do so.

Further, as shown in FIG. 9, by forming a plurality of irregularities (grooves or fins) on the outside of the housing 7, it is possible to adjust the heat transfer direction and improve the heat release efficiency. For example, the groove 72 shown in FIG. 9 is suitable for radiating the heat of the driver element to the upper surface side of the housing. Further, by providing such unevenness, the rigidity of the housing itself can be ensured. If the heat of the driver element is radiated to the bottom surface of the housing, it is preferable to form the groove on the upper side of the side surface of the housing.

Further, the groove or the like formed on the outer surface of the housing may be formed from the side surface of the housing to the upper surface or the bottom surface, or may be formed between the upper surface and the bottom surface. In addition, since the edge (corner) of the groove has a curvature, the internal stress is not concentrated on the corner of the groove, and the biased internal stress is suppressed from being applied to the electro-optical substrate 1. As a result, deterioration of the modulation characteristic can be suppressed.

As described above, according to the present invention, it is possible to reduce the electric loss in the wiring portion of the control electrode, suppress the electric field application to the optical waveguide by the wiring portion and the crosstalk between the electric signals, and also to suppress the occurrence of crosstalk on the relay substrate. It is possible to provide the optical modulator capable of suppressing the heat generation of the driver element arranged in the above from being conducted to the acting portion of the optical modulator.

1 Electro-Optical Substrate 2 Optical Waveguides 5, 51-55 Relay Substrate (Relay Substrate Part)
6,60 Driver element 7 Housing 30-33 Control electrode (modulation electrode)
34 Control electrode (DC electrode)
511, 521, 531, 541, 551, 561 Relay line L1, L11 Optical fiber L2, L4, L5, L7, L10, L12, L15, L17 Lens L3, L8, L13, L14 Reflecting means L6 Wave plate (polarization rotation) Child)
L9 Polarization combining means (polarization beam splitter)

Claims (11)

An electro-optical substrate having an electro-optical effect and having a rectangular shape in a plan view, on which an optical waveguide and a control electrode for conducting an electric signal for controlling a light wave propagating in the optical waveguide are formed. Board,
A relay board on which a relay line for relaying the electric signal to the control electrode is formed;
A housing that accommodates the electro-optical substrate and the relay substrate inside and has a rectangular shape in plan view;
An electric signal input section that is arranged on one short side of the housing and that inputs the electric signal;
In an optical modulator including an optical input section and an optical output section arranged on the other short side of the housing,
At least a part of the relay substrate is arranged on one short side of the electro-optical substrate,
A driver element for amplifying a part of the electric signal and driving the optical modulator is arranged on the relay substrate,
The relay substrate includes a portion arranged along one long side of the electro-optical substrate, and the relay line and the control electrode are electrically connected on the one long side of the electro-optical substrate. An optical modulator characterized by: 2. The optical modulator according to claim 1, wherein the relay board includes a portion arranged along the other long side of the electro-optic board, and the relay line and the control electrode are provided on the electro-optic board. An optical modulator characterized in that the other long side is also electrically connected. The optical modulator according to claim 2, wherein in the optical waveguide, at least four Mach-Zehnder waveguides are arranged side by side in the short side direction of the electro-optical substrate, and the Mach-Zehnder is close to the center in the short side direction. An optical modulator, wherein the type waveguide is arranged so as to be closer to one short side of the electro-optical substrate on which the relay substrate is arranged. 2. The optical modulator according to claim 1, wherein the control electrode has a modulation electrode for applying a high frequency signal to the optical waveguide and a DC electrode for applying a DC voltage to the optical waveguide, and the relay substrate is A relay line and the modulation electrode are electrically connected on the one long side of the electro-optic substrate, and the relay line is electrically connected to the relay line. An optical modulator, wherein the DC electrode and the DC electrode are electrically connected to each other on the other long side of the electro-optical substrate. 2. The optical modulator according to claim 1, wherein the control electrode has a modulation electrode for applying a high frequency signal to the optical waveguide and a DC electrode for applying a DC voltage to the optical waveguide, and the relay substrate is A portion disposed along the other long side of the electro-optical substrate, wherein the relay line, the modulation electrode, and the relay line and the DC electrode are provided on the one long side of the electro-optical substrate. An optical modulator characterized in that it is electrically connected to both of the other long sides. The optical modulator according to claim 1, wherein the relay substrate is formed of one substrate. The optical modulator according to any one of claims 1 to 5, wherein the relay board extends along a portion of the electro-optic board arranged on the one short side and a long side of the electro-optic board. An optical modulator characterized in that the arranged portion is composed of a separate and separate substrate. The optical modulator according to claim 7, wherein the driver element is arranged in a portion of the relay substrate arranged on one short side of the electro-optical substrate. The optical modulator according to claim 7, wherein the thermal conductivity of the relay substrate on which the driver element is disposed is set higher than the thermal conductivity of the relay substrate disposed along the long side of the electro-optical substrate. An optical modulator characterized in that The optical modulator according to any one of claims 1 to 9, wherein between the driver element and the electro-optical substrate is provided on the back surface of the relay substrate arranged along one short side of the electro-optical substrate. An optical modulator characterized in that a groove is formed in the optical modulator. The optical modulator according to any one of claims 1 to 10, wherein a plurality of irregularities are formed on the outside of the housing located near the driver element.

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