JP6638515B2 - Light modulator - Google Patents

Description

  The present invention relates to an optical modulator, and more particularly, to a structure of a highly integrated modulator such as a two-wavelength integrated type.

  As the speed and capacity of optical communication systems increase, the performance and density of optical modulators used in the communication systems increase. Also, with the demand for miniaturization of the optical modulator, the miniaturization of the substrate constituting the optical modulator has been promoted. However, high performance, high density, and miniaturization of the optical modulator are contradictory demands, and contrivances for achieving these requirements are required.

With respect to such an optical modulator, the following inventions have been proposed.
For example, Patent Literature 1 discloses an optical modulator in which an optical waveguide and a modulation electrode are formed on a substrate, and includes a plurality of modulation substrate portions that are separated from each other, and each modulation substrate portion is located at a part of a boundary between each other. An optical modulator in which a low dielectric constant portion having a lower dielectric constant than the substrate material of the modulation substrate portion is arranged is disclosed.

JP 201419754 A

  In recent years, highly integrated optical modulators such as a two-wavelength integrated type have been developed. FIG. 1 shows a configuration example of a conventional dual-wavelength integrated DP-QPSK (Dual Polarization-Quadrature Phase Shift Keying) modulator. The optical modulator shown in the figure has an optical waveguide modulator M1 to which a lightwave having a wavelength λ1 is inputted, and an optical waveguide modulator M2 to which a lightwave having a wavelength λ2 different from the wavelength λ1 is inputted. The units M1 and M2 are configured to operate independently of each other.

  Each of the optical waveguide modulating units M1 and M2 has an optical waveguide 2, a control electrode 3 for controlling a lightwave propagating through the optical waveguide 2, and a lightwave propagating through the optical waveguide 2 on a substrate 1 having an electro-optic effect. And a light receiving element 4 for detecting the The control electrode 3 includes an RF electrode 3a to which a high-frequency signal (modulation signal) is applied and DC electrodes 3b and 3c to which a DC voltage (bias voltage) is applied.

The optical waveguides 2 of the optical waveguide modulators M1 and M2 have a structure in which Mach-Zehnder waveguides are nested and multiplexed, and a number of control electrodes 3 and light receiving elements 4 are provided correspondingly. ing. In the figure, four RF electrodes 3a, six DC electrodes 3b and 3c, and two light receiving elements 4 are provided in each of the optical waveguide modulation sections M1 and M2.
A polarization combiner 5 is disposed downstream of the optical waveguide modulator M1, and the optical combiner 5 combines the optical waves propagating through the output-side arm of the main Mach-Zehnder waveguide into an optical fiber. 6 is output. The same applies to the optical waveguide modulator M2. The polarization combining unit 5 has a structure in which polarization combining is performed using a spatial optical system and a structure in which polarization combining is performed using an optical waveguide.

As described above, a substrate (chip) on which a large number of control electrodes and light receiving elements are arranged is used for the highly integrated optical modulator. For this reason, the wiring (routing) of electric wires (not shown) connected to those components increases, and there is a problem that the size of the substrate increases.
In addition, the wiring from the electric pad provided on the side of the substrate to the working part (the part where the electric field generated from the control electrode acts on the optical waveguide) is concentrated in a part of the area, and the arrangement becomes difficult. There was also. This problem has been remarkable especially in a high-frequency line for transmitting a high-frequency signal. As the high-frequency line, a line structure such as a CPW (coplanar waveguide) whose impedance is controlled is used. However, such a line structure has a low degree of freedom in pattern design and crosstalk of a high-frequency signal occurs between adjacent lines. It is.

In addition, there is a concern that unnecessary light interference may occur between optical waveguide modulators that transmit light waves of different wavelengths. The unnecessary light includes uncoupled light between the fiber and the chip, radiation mode light (Off light) from the multiplexing portion of the optical waveguide, and light leaking from the bent or branched portion of the optical waveguide.
Also, for example, in the case of the two-wavelength integrated type, the electrode pattern length of the optical waveguide and control electrode on one chip is more than doubled as compared with the one-wavelength type, so that the pattern yield is less than the square of the one-wavelength type pattern. turn into.

  The problem to be solved by the present invention is to provide an optical modulator which can solve the above-mentioned problems and can easily route electric wires on a substrate.

In order to solve the above problems, an optical modulator according to the present invention has the following technical features.
(1) A first substrate on which a light modulation area for phase polarization modulation or quadrature amplitude modulation for modulating light of a first wavelength is formed, and phase polarization modulation or light for modulating light of a second wavelength. A second substrate on which a light modulation region for quadrature amplitude modulation is formed, wherein the first and second substrates are arranged in parallel in the width direction of the substrate, and A relay board for inputting a high-frequency signal for light modulation to the first and second boards on a side opposite to the first board, wherein the second board receives an input from the relay board; An electric wire for transmitting a high-frequency signal to the first substrate to the first substrate is formed, and the first and second substrates are displaced in a length direction of the substrate. An optical modulator.

(2) In the optical modulator according to (1), a DC electrode and an RF electrode are formed on the first and second substrates, respectively, and the first and second substrates are formed of a substrate. The arrangement order of the DC electrode and the RF electrode in the length direction of the optical modulator is different.

(3) The optical modulator according to (1) or (2), wherein the first and second substrates are arranged so as to be shifted in a thickness direction of the substrate. .

(4) The optical modulator according to any one of the above (1) to (3), wherein the first and second substrates have an edge of a substrate edge removed. It is.

  An optical modulator according to the present invention modulates a first substrate on which an optical modulation region for phase polarization modulation or quadrature amplitude modulation for modulating light of a first wavelength is formed, and light of a second wavelength. A second substrate on which an optical modulation region for phase polarization modulation or quadrature amplitude modulation is formed, wherein the first and second substrates are arranged in parallel and extend in the length direction of the substrate. The optical modulator can be provided so that the electric wires on the substrate can be easily routed because the optical modulator is shifted.

FIG. 10 is a plan view illustrating a configuration example of a conventional two-wavelength integrated DP-QPSK modulator. FIG. 2 is a plan view illustrating an optical modulator according to a first embodiment of the present invention. FIG. 7 is a plan view illustrating an optical modulator according to a second embodiment of the present invention. FIG. 11 is a plan view illustrating an optical modulator according to a third embodiment of the present invention. FIG. 13 is a plan view illustrating an optical modulator according to a fourth embodiment of the present invention. FIG. 14 is a plan view illustrating an optical modulator according to a fifth embodiment of the present invention. FIG. 14 is a side sectional view illustrating an optical modulator according to a fifth embodiment of the present invention. FIG. 14 is a side sectional view illustrating a modification of the optical modulator according to the fifth embodiment of the present invention. FIG. 14 is a side view illustrating an optical modulator according to a sixth embodiment of the present invention.

Hereinafter, the optical modulator according to the present invention will be described in detail.
The optical modulator according to the present invention is, for example, as shown in FIG. 2, a first substrate 1A on which an optical modulation region for phase polarization modulation or quadrature amplitude modulation for modulating light of a first wavelength λ1 is formed. And a second substrate 1B on which a light modulation region for phase polarization modulation or quadrature amplitude modulation for modulating light of the second wavelength λ2 is formed. Further, the first substrate 1A and the second substrate 1B are arranged in parallel and are arranged so as to be shifted in the length direction of the substrate.

Substrates 1A and 1B may be any substrates that can form an optical waveguide, such as quartz and a semiconductor. In particular, substrates having an electro-optic effect, such as LiNbO ₃ (lithium niobate), LiTaO ₃ (lithium tantalate), or PLZT A substrate using any single crystal of (lead lanthanum zirconate titanate) or the like can be suitably used.

The optical waveguide 2 formed on the substrates 1A and 1B is formed, for example, by thermally diffusing a high refractive index material such as titanium (Ti) onto a LiNbO ₃ substrate (LN substrate). Further, a rib-type optical waveguide in which grooves are formed on both sides of a portion to be an optical waveguide, and a ridge-type waveguide having a convex optical waveguide portion can also be used. In addition, the present invention can be applied to an optical circuit in which an optical waveguide is formed on a different waveguide substrate such as a PLC, and these waveguide substrates are bonded and integrated.

Control electrodes 3 for controlling light waves propagating through the optical waveguide 2 are provided on the substrates 1A and 1B. The control electrode 3 includes an RF electrode 3a constituting a modulation electrode, a ground electrode (not shown) surrounding the RF electrode 3a, and DC electrodes 3b and 3c for applying a DC voltage. These control electrodes 3 can be formed by forming an electrode pattern of Ti / Au on the substrate surface and using a gold plating method or the like. Further, if necessary, a buffer layer such as dielectric SiO ₂ can be provided on the substrate surface after the formation of the optical waveguide.

  The main feature of the optical modulator according to the present invention is that the substrates 1A and 1B are arranged in parallel with each other and are shifted in the length direction of the substrates. Hereinafter, a detailed description will be given with reference to examples. In this specification, the length direction of the substrate is referred to as “X direction”, and the width direction of the substrate is referred to as “Y direction”. The X direction corresponds to the traveling direction of the light wave (the direction of arrow X in the figure), and the direction orthogonal to this (the direction of arrow Y in the figure) is the Y direction.

FIG. 2 is a plan view illustrating the optical modulator according to the first embodiment of the present invention.
In the optical modulator of this example, the substrates 1A and 1B are arranged in parallel with each other, and the substrate 1B is arranged to be shifted downstream in the X direction from the substrate 1A.
A terminal substrate 11 for terminating a high-frequency signal to the RF electrode 3a of the substrate 1A is provided on a side of the substrate 1A on a side facing the substrate 1B. In addition, a termination substrate 12 that terminates a high-frequency signal to the RF electrode 3a of the substrate 1B is provided on a side of the substrate 1B on a side facing the substrate 1A. Further, a relay board 13 and a DC wiring board 16 are also provided on the side of the board 1B on the side facing the board 1A.

  An electric wire 41 for relaying a high-frequency signal input from the RF connector 21 is wired on the relay board 13. The electric wires 41 are electrically connected to the connection pads 31 provided on the side of the substrate 1B by wire bonding or the like. The high-frequency signal for the substrate 1A is relayed to the substrate 1A through the electric wire 42 on the substrate 1B, and is applied to the RF electrode 3a of the substrate 1A. The high frequency signal for the substrate 1B is applied to the RF electrode 3a of the substrate 1B through the electric wire 43 on the substrate 1B. The connection pads 31 can be arranged at intervals of about 500 μm. On the other hand, the RF connector 21 is larger than the connection pad 31 and requires a space of 2.5 mm or more even for a small one. The relay board 13 has a role of adjusting the electric wires 41 connected to the RF connector 21 so as to reduce the distance toward the connection pads 31.

  On the DC wiring board 16, an electric wire 44 for relaying a DC voltage input from the DC pin 22 is wired. The electric wires 44 are electrically connected to the connection pads 32 provided on the side of the substrate 1B by wire bonding or the like. The DC voltage for the substrate 1A is relayed to the substrate 1A through the electric wire 45 on the substrate 1B, and is applied to the DC electrodes 3b and 3c of the substrate 1A. The DC voltage for the substrate 1B is applied to the DC electrodes 3b and 3c of the substrate 1A through electric wires (not shown) on the substrate 1B. That is, the extraction portion of the DC electrode 3c is shared by the substrate 1A and the substrate 1B. In the present example, the electric wires 45 for the substrate 1A are formed so as to straddle the substrate 1B by bonding wiring, but may be wired directly on the substrate 1B. Alternatively, the DC pins 22 and the connection pads 32 may be directly connected to each other so that the DC wiring board 16 is not used.

  In this way, by arranging the substrates 1A and 1B in parallel with each other and disposing the substrate 1B so as to be shifted to the downstream side in the X direction from the substrate 1A, it is possible to easily route the electric wires on the substrate. . In particular, there is an effect that the electric wire 42 for the RF electrode 3a of the substrate 1A can be shortened. That is, for example, when the substrates 1A and 1B are arranged without being shifted in the X direction, the electric lines 42 need to be routed so as to bypass the electric lines 43 for the RF electrodes 3a of the substrate 1B. By displacing in the X direction, there is no need for such a detour. The electric wires 42 and 43 for transmitting high-frequency signals need to be high-frequency lines whose impedance is controlled, such as CPW, and the line structure is limited. Shortening the wiring length is very effective in reducing loss of high-frequency signals. It is effective for Further, as compared with the case where elements for two wavelengths are integrated on one chip, the number of fine patterns of waveguides and electrodes mounted on one chip is reduced, so that yield deterioration due to pattern defects and the like can be reduced. Further, since the length of the element can be made shorter than the case where two wavelengths are integrated, the number of patterns mounted on one wafer can be increased.

FIG. 3 is a plan view illustrating an optical modulator according to a second embodiment of the present invention.
In the optical modulator of this example, the substrates 1A and 1B are arranged in parallel with each other, and the substrate 1B is arranged to be shifted downstream in the X direction from the substrate 1A.
On the substrate 1A, an RF electrode 3a, a DC electrode 3b, and a DC electrode 3c are arranged in this order from upstream to downstream in the X direction. On the other hand, on the substrate 1B, the DC electrode 3c, the RF electrode 3a, and the DC electrode 3b are arranged in this order from upstream to downstream in the X direction. That is, the arrangement order of the DC electrode and the RF electrode in the X direction differs between the substrate 1A and the substrate 1B.

  Thus, by arranging the DC electrode 3c of the substrate 1B upstream of the RF electrode 3a, the electric wire 44 is wired on the upstream portion of the DC electrode 3c on the substrate 1B, and the downstream portion of the DC electrode 3c of the substrate 1B. The electric wire 43 can be routed. Thereby, even if the shift width of the substrates 1A and 1B is reduced, the shift width of the RF electrode 3a of the substrate 1A and the RF electrode 3b of the substrate 1B can be sufficiently ensured. That is, even if the shift width of the substrates 1A and 1B is reduced, it is possible to easily perform wiring routing effective in reducing loss of high-frequency signals. Therefore, the length L from the upstream edge of the substrate 1A in the X direction to the downstream edge of the substrate 1B in the X direction is set to match the arrangement order of the DC electrode and the RF electrode (for example, the structure of the first embodiment). (FIG. 2)). That is, by changing the arrangement order of the DC electrode and the RF electrode in the X direction between the substrate 1A and the substrate 1B, the effect of further reducing the total length in the length direction of the substrate can be obtained.

FIG. 4 is a plan view illustrating an optical modulator according to a third embodiment of the present invention.
In the optical modulator of this example, the substrates 1A and 1B are arranged in parallel with each other, and the substrate 1B is arranged to be shifted downstream in the X direction from the substrate 1A. Further, the board 1A and the board 1B are separated from each other, and the relay board 14 and the DC wiring board 16 are arranged between the board 1A and the board 1B. A high-frequency signal for the board 1A is input from the RF connector 21, is relayed to the board 1A through the relay board 13, the board 1B, and the relay board 14, and is applied to the RF electrode 3a of the board 1A.

  In this way, by adopting a structure in which the substrate 1A and the substrate 1B are separated from each other, an effect that an optical system (for example, the polarization combining unit 6 using a spatial optical system) can be easily arranged can be obtained.

FIG. 5 is a plan view illustrating an optical modulator according to a fourth embodiment of the present invention.
In the optical modulator of this example, the substrates 1A and 1B are arranged in parallel with each other, and the substrate 1B is arranged to be shifted downstream in the X direction from the substrate 1A. Further, the arrangement order of the DC electrode and the RF electrode in the X direction is different between the substrate 1A and the substrate 1B. Further, the board 1A and the board 1B are separated from each other, and the relay board 14 and the DC wiring board 16 are arranged between the board 1A and the board 1B.

  That is, the fourth embodiment has a structure in which the second embodiment and the third embodiment are combined. For this reason, not only can the wiring of the electric wires on the substrate be easily routed, but also the effect of shortening the total length in the length direction of the substrate and the effect of easily disposing the optical system can be obtained.

FIG. 6 is a plan view illustrating an optical modulator according to a fifth embodiment of the present invention, and FIG. 7 is a side sectional view thereof.
In the optical modulator of this example, the substrates 1A and 1B are arranged in parallel with each other, and the substrate 1B is arranged to be shifted downstream in the X direction from the substrate 1A. The substrate 1A and the substrate 1B are separated from each other, and the DC wiring substrate 16 is arranged between the substrate 1A and the substrate 1B. Further, the substrate 1A and the substrate 1B are arranged so as to be shifted from each other in the thickness direction of the substrate. Specifically, the substrate 1A is arranged above the substrate 1B. Further, the relay board 15 to which the RF connector 21 for inputting a high-frequency signal to the board 1A is connected is arranged so as to overlap a part of the board 1B.

  According to such a structure, not only an effect of facilitating the arrangement of the optical system can be obtained, but also an electric wire for relaying a high-frequency signal to the substrate 1A can be removed from the substrate 1B, and wiring of the electric line of the substrate 1B Can be further simplified. Further, the relay substrate 15 is made of a low-loss substrate material, and the high-frequency line has a line structure with a low transmission loss, so that an optical modulator that is more excellent in high-frequency characteristics than when wired on the substrate 1B. Can be realized.

FIG. 8 is a side sectional view illustrating a modification of the optical modulator according to the fifth embodiment of the present invention.
The optical modulator of this embodiment uses the lead pin 23 as a terminal for inputting a high-frequency signal. That is, instead of inputting a high-frequency signal from the side of the housing through the RF connector 21 provided in the lateral direction (horizontal direction) on the side surface of the housing of the optical modulator, the high frequency signal is input to the side surface of the housing of the optical modulator in the vertical direction (vertical direction). A high frequency signal is inputted from the bottom of the housing through the lead pins 23 provided in the housing. With such a structure, the input of the high-frequency signal can be arranged in a line.

FIG. 9 is a side view illustrating an optical modulator according to a sixth embodiment of the present invention.
In the optical modulator of this example, the substrate 1A (1B) has a structure in which the edge 8 of the substrate end is removed.
This can prevent other components from being damaged by the edge of the substrate end. Such edge elimination is applicable in combination with the above embodiments.

  As described above, the present invention has been described based on the embodiments. However, it is needless to say that the present invention is not limited to the above-described contents, and that the design can be appropriately changed without departing from the spirit of the present invention.

  As described above, according to the present invention, it is possible to provide an optical modulator that can facilitate the routing of electric wires on a substrate.

1, 1A, 1A Substrate 2 Optical waveguide 3 Control electrode 3a RF electrode 3b, 3c DC electrode 4 Light receiving element 5 Polarization combining section 6 Optical fiber 8 Edge 11, 12 Termination board 13-15 Relay board 16 DC wiring board 21 RF connector 22 DC pin 23 Lead pin 31, 32 Connection pad 41-45 Electric wire

Claims (4)

A first substrate on which a light modulation region for phase polarization modulation or quadrature amplitude modulation for modulating light of a first wavelength is formed;
A second substrate on which a light modulation region for phase polarization modulation or quadrature amplitude modulation for modulating light of the second wavelength is formed,
The first and second substrates are arranged in parallel in the width direction of the substrate ,
On the opposite side of the second substrate from the first substrate, a relay substrate for inputting a high-frequency signal for light modulation to the first and second substrates is provided.
An electric wire for transmitting a high-frequency signal for the first substrate input from the relay substrate to the first substrate is formed on the second substrate,
The optical modulator according to claim 1, wherein the first and second substrates are arranged so as to be shifted in a length direction of the substrate. The optical modulator according to claim 1,
A DC electrode and an RF electrode are respectively formed on the first and second substrates,
An optical modulator characterized in that the arrangement order of the DC electrode and the RF electrode in the length direction of the substrate differs between the first and second substrates. In the optical modulator according to claim 1 or 2,
The optical modulator according to claim 1, wherein the first and second substrates are arranged so as to be shifted from each other in a thickness direction of the substrate. The optical modulator according to any one of claims 1 to 3,
An optical modulator according to claim 1, wherein said first and second substrates have an edge of a substrate edge removed.

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