CN118348699A - Coherent optical modulator chip and coherent modulator - Google Patents

Abstract

The present invention discloses a coherent optical modulator chip and a coherent modulator, which relate to the technical field of optical modulators, wherein in the optical structure of the optical modulator chip, a bilateral directional coupler is used to divide the optical signal coupled into a waveguide into two beams with a phase difference of π, so as to be transmitted through two first waveguide arms respectively, and the optical signal in each waveguide arm is divided into two beams by a first beam splitter, so as to be transmitted through two second waveguide arms respectively; two electro-optical modulators are respectively arranged downstream of the two first beam splitters, and are used to modulate the optical signal in the second waveguide arm, and the optical signals in the two third waveguide arms of each electro-optical modulator are combined into one beam by a first beam combiner, so as to be transmitted through a fourth waveguide arm, and the optical signals in the two fourth waveguide arms are combined into one beam by a second beam combiner; and a phase shifter is arranged in one of the fourth waveguide arms. The technical solution of the present invention reduces the number of phase shifters, can reduce the overall power consumption of the coherent modulator, and improve the stability of the coherent optical modulator chip.

Description

Coherent optical modulator chip and coherent modulator

Technical Field

The present invention relates to the technical field of optical modulators, and in particular to a coherent optical modulator chip and a coherent modulator.

Background technique

In the related art, thin-film lithium niobate electro-optic modulators often use a coherent composite modulation scheme to achieve an exponential increase in data transmission rate. However, the coherent composite modulation scheme requires the use of multiple phase shifters to adjust the phase of the optical signal.

In the coherent optical modulator chip of the correlation modulator, the optical structure usually includes two electro-optic modulators arranged in parallel, each electro-optic modulator includes a pair of waveguide arms, and a phase shifter needs to be set in one of each pair of waveguide arms to lock the bias point of the electro-optic modulator at the destructive interference point. Setting multiple phase shifters not only consumes high power, but may also cause thermal crosstalk, resulting in a high sensitivity of the coherent optical modulator chip to the environment, thereby affecting the stability of the modulator performance.

Summary of the invention

The main purpose of the present invention is to provide a coherent optical modulator chip and a coherent modulator, aiming to reduce the overall power consumption of the coherent optical modulator and improve the stability of the coherent optical modulator chip.

To achieve the above object, the coherent optical modulator chip proposed in the present invention includes:

A bilateral directional coupler, the bilateral directional coupler having an input end and an output end arranged in opposite directions, the output end being provided with two first waveguide arms arranged side by side, the bilateral directional coupler being used to receive an optical signal in TE0 mode from the input end, and to divide the optical signal into two beams with a phase difference of π at the output end, so as to be transmitted through the two first waveguide arms respectively;

Two first beam splitters, the two first beam splitters are arranged downstream of the bilateral directional coupler, each of the first beam splitters is arranged corresponding to one of the first waveguide arms, and is used to split the optical signal in the first waveguide arm into two beams, so as to be transmitted through two second waveguide arms arranged side by side respectively;

Two electro-optical modulators, the two electro-optical modulators are respectively arranged downstream of the two first beam splitters, the electro-optical modulators include two third waveguide arms arranged side by side, each of the third waveguide arms is used to transmit an optical signal in the second waveguide arm to perform in-phase orthogonal modulation on the optical signal;

Two first beam combiners, the two first beam combiners are respectively arranged downstream of the two electro-optical modulators, each of the first beam combiners is respectively arranged corresponding to one of the electro-optical modulators, and are used to combine the optical signals in the two third waveguide arms into one beam for transmission through the fourth waveguide arm;

a second beam combiner, which is disposed downstream of the two first beam combiners and is used to combine the optical signals in the two fourth waveguide arms into one beam; and

A phase shifter is provided in one of the fourth waveguide arms and is used for performing phase shift on the optical signal in the fourth waveguide arm.

In one embodiment, the bilateral directional coupler comprises:

a gradient waveguide portion, the gradient waveguide portion being configured to receive the optical signal in TE0 mode and convert the optical signal from TE0 mode to TE1 mode; and

A bilateral coupling portion, one end of which is connected to the gradient waveguide portion, and the other end of which is used to connect the two first waveguide arms. The bilateral coupling portion is used to couple the optical signal in the TE1 mode into two optical signals in the TE0 mode, and the phase difference between the two optical signals is π, and the two optical signals are transmitted through the two first waveguide arms respectively.

In one embodiment, the coherent optical modulator chip further comprises an optical cross waveguide, wherein the optical cross waveguide comprises two cross-arranged waveguide structures, wherein the waveguide structure has a first end and a second end that are arranged opposite to each other;

The two first ends are respectively connected to one of the second waveguide arms of the two first beam splitters;

The two second ends are respectively connected to one of the third waveguide arms of the two electro-optic modulators.

In one embodiment, the coherent optical modulator chip further includes an electrical structure, and the electrical structure includes:

three ground electrodes, the three ground electrodes being arranged at intervals; and

Two signal electrodes, each of which is arranged between two adjacent ground electrodes;

A third waveguide arm is disposed between each of the ground electrodes and a signal electrode.

In one embodiment, the coherent optical modulator chip comprises:

substrate layer;

A buried layer, disposed on one side of the substrate layer;

a thin-film lithium niobate waveguide layer, disposed on a side of the buried layer away from the substrate layer, the waveguide layer being formed with the optical structure; and

The upper cladding layer is arranged on a side of the waveguide layer away from the buried layer, and the electrical structure is arranged in the upper cladding layer.

In one embodiment, the electrical structure is a coplanar waveguide structure;

And/or, the optical structure is a thin film lithium niobate ridge waveguide structure.

The present invention also provides a single polarization coherent modulator, comprising any one of the coherent light modulator chips described above.

In one embodiment, the single polarization coherent modulator sequentially connects an input waveguide, a coherent optical modulator chip, and an output waveguide;

One end of the input waveguide facing away from the coherent light modulator chip is used to couple the laser light output by the tunable laser to transmit the optical signal of the TE0 mode to the double-sided directional coupler of the coherent light modulator chip.

The present invention further provides a coherent modulator, comprising the coherent optical modulator chip described in any one of the above, wherein the coherent optical modulator chip comprises:

A bilateral directional coupler, wherein the bilateral directional coupler has an input end and an output end arranged in opposite directions, the output end is provided with two first waveguide arms arranged side by side, the bilateral directional coupler is used to receive an optical signal in TE0 mode from the input end, and to divide the optical signal into two beams with a phase difference of π at the output end, so as to be transmitted through the two first waveguide arms respectively;

Two first beam splitters, the two first beam splitters are arranged downstream of the bilateral directional coupler, each of the first beam splitters is arranged corresponding to one of the first waveguide arms, and is used to split the optical signal in the first waveguide arm into two beams, so as to be transmitted through two second waveguide arms arranged side by side respectively;

Two electro-optical modulators, the two electro-optical modulators are respectively arranged downstream of the two first beam splitters, the electro-optical modulators include two third waveguide arms arranged side by side, each of the third waveguide arms is used to transmit an optical signal in the second waveguide arm to modulate the optical signal;

Two first beam combiners, the two first beam combiners are respectively arranged downstream of the two electro-optical modulators, each of the first beam combiners is respectively arranged corresponding to one of the electro-optical modulators, and are used to combine the optical signals in the two third waveguide arms into one beam for transmission through the fourth waveguide arm;

a second beam combiner, which is disposed downstream of the two first beam combiners and is used to combine the optical signals in the two fourth waveguide arms into one beam; and

A phase shifter is provided in one of the fourth waveguide arms and is used for performing phase shift on the optical signal in the fourth waveguide arm.

In one embodiment, the coherent modulator is a single polarization coherent modulator, and the single polarization coherent modulator includes an input waveguide, a coherent optical modulator chip, and an output waveguide connected in sequence;

One end of the input waveguide facing away from the coherent light modulator chip is used to couple the laser light output by the tunable laser to transmit the optical signal of the TE0 mode to the double-sided directional coupler of the coherent light modulator chip.

The coherent modulator is a dual-polarization coherent modulator, and the dual-polarization coherent modulator comprises an input waveguide, two coherent optical modulator chips and an output waveguide;

In one embodiment, the two coherent light modulator chips are arranged in parallel between the input waveguide and the output waveguide.

In one embodiment, the dual-polarization coherent modulator comprises:

The input waveguide, one end of which is used to couple the laser light output by the tunable laser to transmit the optical signal of TE0 mode;

a second beam splitter, the second beam splitter being arranged downstream of the input waveguide and being used for splitting the optical signal in the input waveguide into two beams, so as to be transmitted respectively through two fifth waveguide arms arranged side by side;

two coherent light modulator chips, the two coherent light modulator chips are arranged downstream of the second beam splitter, and each coherent light modulator chip is arranged corresponding to one of the fifth waveguide arms; and

A polarization rotation beam combiner is provided downstream of the two coherent light modulator chips and is used for converting the optical signals output by the two coherent light modulator chips into TE0 mode and TM0 mode and combining them into one beam.

The technical solution of the present invention replaces the traditional beam splitter by arranging a bilateral directional coupler upstream of two parallel electro-optic modulators. The bilateral directional coupler can split a single optical signal into two beams for transmission, and can make the phase difference of the two split optical signals π. With such an arrangement, there is no need to arrange a phase shifter at the waveguide arm of each electro-optic modulator, and the phase of the optical signal can be pre-adjusted by the bilateral directional coupler so that the bias point of the electro-optic modulator is locked at the destructive interference point, thereby reducing the number of phase shifters in the coherent optical modulator chip to reduce the overall power consumption of the device, and avoiding the risk of thermal crosstalk caused by the thermal phase shifter, thereby helping to reduce the sensitivity of the coherent optical modulator chip to the environment and improve the stability of the coherent optical modulator chip.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

FIG1 is a schematic structural diagram of an embodiment of a coherent optical modulator chip provided by the present invention;

FIG2 is a diagram showing simulation results of the double-sided directional coupler input TE1 mode of the coherent optical modulator chip in FIG1 ;

FIG3 is a diagram showing simulation results of the double-sided directional coupler inputting the TE0 mode of the coherent optical modulator chip in FIG1;

FIG4 is a schematic structural diagram of an embodiment of a coherent modulator provided by the present invention;

FIG5 is a schematic structural diagram of another embodiment of a coherent modulator provided by the present invention;

Description of Figure Numbers:

100, coherent optical modulator chip; 10, substrate layer; 20, buried layer; 30, thin-film lithium niobate waveguide layer; 40, optical structure; 41, bilateral directional coupler; 411, gradient waveguide section; 412, bilateral coupling section; 42, first waveguide arm; 43, first beam splitter; 44, second waveguide arm; 45, electro-optic modulator; 451, third waveguide arm; 46, first beam combiner; 461, fourth waveguide arm; 47, second beam combiner; 48, phase shifter; 49, optical cross waveguide; 50, upper cladding; 60, electrical structure; 61, ground electrode; 62, signal electrode;

200. Single polarization coherent modulator;

300, dual polarization coherent modulator; 310, second beam splitter; 320, polarization rotation beam combiner.

The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings.

Detailed ways

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and/or" or "and/or" appears in the full text, its meaning includes three parallel schemes. Taking "A and/or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

In the related art, thin-film lithium niobate electro-optic modulators often use a coherent composite modulation scheme to achieve an exponential increase in data transmission rate. However, the coherent composite modulation scheme requires the use of multiple phase shifters to adjust the phase of the optical signal.

In the coherent optical modulator chip of the correlation modulator, the optical structure usually includes two electro-optic modulators arranged in parallel, each electro-optic modulator includes a pair of waveguide arms, and a phase shifter needs to be set in one of each pair of waveguide arms to lock the bias point of the electro-optic modulator at the destructive interference point. Setting multiple phase shifters may cause thermal crosstalk, resulting in high overall power consumption of the coherent optical modulator chip and high sensitivity to the environment, which will affect the stability of the modulator performance.

The present invention provides a coherent optical modulator chip 100 .

Referring to FIG. 1 to FIG. 5 , in one embodiment of the present invention, the coherent optical modulator chip 100 includes an optical structure 40, and the optical structure 40 includes:

A bilateral directional coupler 41, wherein the bilateral directional coupler 41 has an input end and an output end disposed opposite to each other, wherein the output end is provided with two first waveguide arms 42 disposed side by side, and the bilateral directional coupler 41 is used to receive an optical signal from the input end and to split the optical signal into two beams at the output end, so as to be transmitted through the two first waveguide arms 42 respectively;

Two first beam splitters 43, the two first beam splitters 43 are arranged downstream of the bilateral directional coupler 41, each first beam splitter 43 is arranged corresponding to one first waveguide arm 42, and is used to split the optical signal in the first waveguide arm 42 into two beams, so as to be transmitted respectively through two second waveguide arms 44 arranged side by side;

Two electro-optical modulators 45, the two electro-optical modulators 45 are respectively arranged downstream of the two first beam splitters 43, the electro-optical modulator 45 comprises two third waveguide arms 451 arranged side by side, each of the third waveguide arms 451 is used to transmit an optical signal in the second waveguide arm 44 to modulate the optical signal;

Two first beam combiners 46, the two first beam combiners 46 are respectively arranged downstream of the two electro-optical modulators 45, each of the first beam combiners 46 is respectively arranged corresponding to one electro-optical modulator 45, and are used to combine the optical signals in the two third waveguide arms 451 into one beam, so as to transmit through the fourth waveguide arm 461;

A second beam combiner 47, which is disposed downstream of the two first beam combiners 46 and is used to combine the optical signals in the two fourth waveguide arms 461 into one beam; and

The phase shifter 48 is disposed in one of the fourth waveguide arms 461 and is used to shift the phase of the optical signal in the fourth waveguide arm 461 .

The first beam splitter 43 may be, but is not limited to, a Y-type beam splitter or a 1×2 multimode interferometer, the electro-optic modulator 45 is a Mach-Zehnder interferometer electro-optic modulator 45, and the phase shifter 48 is a π/2 phase shifter. Specifically, the optical signal of the TE0 waveguide mode coupled into the optical structure 40 is first coupled into the fundamental mode TE0 with equal power and phase difference of π by the bilateral directional coupler 41, and then output in two paths through two first waveguide arms 42 arranged side by side; then, the two paths of optical signals are divided into four paths by two first beam splitters 43, and enter the third waveguide arms 451 of two parallel electro-optical modulators 45 to be modulated by the two electro-optical modulators 45; thereafter, two first beam combiners 46 are arranged, each of which combines the optical signals in the two third waveguide arms 451 of an electro-optical modulator 45 into one beam, so as to combine to form two paths of optical signals, and transmit them respectively through two fourth waveguide arms 461, and a π/2 phase shifter 48 is provided at one of the fourth waveguide arms 461 for phase shifting the optical signal in the fourth waveguide arm 461; finally, the two paths of optical signals in the two fourth waveguide arms 461 are combined by the second beam combiner 47 and output externally.

The technical solution of the present invention replaces the traditional beam splitter by arranging a bilateral directional coupler 41 upstream of two parallel electro-optic modulators 45. The bilateral directional coupler 41 can split a single optical signal into two beams for transmission, and can make the phase difference of the two split optical signals π. With such an arrangement, there is no need to arrange an additional phase shifter at the waveguide arm of each electro-optic modulator 45. The phase of the optical signal can be pre-adjusted by the bilateral directional coupler 41, so that the bias point of the electro-optic modulator 45 is locked at the destructive interference point, thereby reducing the number of phase shifters 48 in the coherent optical modulator chip 100, so as to reduce the overall power consumption of the device, and reduce the risk of thermal crosstalk caused by the thermal phase shifter 48, so as to reduce the sensitivity of the coherent optical modulator chip 100 to the environment and improve the stability of the coherent optical modulator chip 100.

Furthermore, the technical solution of the present invention can also significantly reduce the overall power consumption of the coherent light modulator chip 100 by reducing the number of phase shifters 48 in the coherent light modulator chip 100 .

Please refer to FIG. 2 , in an embodiment of the present invention, the bilateral directional coupler 41 includes:

a gradient waveguide portion 411, wherein the gradient waveguide portion 411 is used to receive the optical signal in TE0 mode and convert the optical signal from TE0 mode to TE1 mode; and

A bilateral coupling portion 412, one end of which is connected to the gradient waveguide portion 411, and the other end is used to connect the two first waveguide arms 42, and the bilateral coupling portion 412 is used to couple the optical signal in the TE1 mode into two beams of optical signals in the TE0 mode, and the phase difference between the two beams of the optical signal is π, and they are transmitted through the two first waveguide arms 42 respectively.

The gradually changing waveguide portion 411 is a gradually changing tapered waveguide, and its cross-sectional area is gradually increased in a direction toward the double-sided coupling portion 412 .

Further, please refer to Figures 4 and 5, Figure 4 is a diagram showing the simulation results of the TE1 mode intensity and phase of the input of the bilateral directional coupler 41, and Figure 5 is a diagram showing the simulation results of the TE0 mode intensity and phase of the output of the bilateral directional coupler 41. Both Figures 4 and 5 are the results obtained by Lumerical FDTD software simulation.

As can be seen from Figure 4, the optical signal of the TE0 mode entering the bilateral directional coupler 41 passes through the gradient waveguide part 411 and is converted into the TE1 mode; as can be seen from Figure 5, in terms of the spatial distribution of the mode field, the optical signal of the TE1 mode is composed of two mode petals with equal intensity and a phase difference of π. After the optical signal of the TE1 mode passes through the bilateral coupling part 412 of the bilateral directional coupler 41, the two mode petals are respectively coupled into the single-mode waveguide composed of the upper and lower first waveguide arms 42 to realize the TE0 mode output, and the optical signals in the two first waveguide arms 42 maintain equal intensity and a phase difference of π.

Please refer to FIG. 2 . In an embodiment of the present invention, the coherent optical modulator chip 100 further includes an optical cross waveguide 49 . The optical cross waveguide 49 includes two cross-arranged waveguide structures. The waveguide structure has a first end and a second end that are arranged opposite to each other.

The two first ends are respectively connected to one of the second waveguide arms 44 of the two first beam splitters 43;

The two second ends are respectively connected to one of the third waveguide arms 451 of the two electro-optic modulators 45 .

Among them, by setting up a low-crosstalk, low-loss optical cross waveguide 49, the optical signals in the two waveguide structures can be output without interfering with each other.

Please refer to FIG. 2 . In an embodiment of the present invention, the coherent optical modulator chip 100 further includes an electrical structure 60 . The electrical structure 60 includes:

three ground electrodes 61, wherein the three ground electrodes 61 are arranged at intervals; and

Two signal electrodes 62, each of the signal electrodes 62 is disposed between two adjacent ground electrodes 61;

A third waveguide arm 451 is disposed between each of the ground electrodes 61 and each of the signal electrodes 62 .

In this way, three alternately arranged ground electrodes 61 and two signal electrodes 62 can form a traveling wave electrode structure, which is used to modulate the radio frequency electrical signal by loading it into the optical signal in the waveguide using the electro-optical effect of lithium niobate. The ground electrode 61 and the signal electrode 62 are both metal electrodes, and the traveling wave electrode structure is a coplanar waveguide structure.

In some embodiments, the material of the metal electrode is Au, the thickness is 0.9 microns, the width of the signal electrode 62 is 25 microns, the width of the ground electrode 61 is 100 microns, and the electrode spacing is 5 microns. Of course, the technical solution of the present invention is not limited to this, and the material of the electrical structure 60, the electrode thickness and other parameters can also be set according to actual needs, and are not limited here.

Referring to FIG. 1 , in an embodiment of the present invention, the coherent optical modulator chip 100 includes:

A substrate layer 10;

A buried layer 20, disposed on one side of the substrate layer 10;

A thin-film lithium niobate waveguide layer 30 is disposed on a side of the buried layer 20 away from the substrate layer 10, and the optical structure 40 is formed on the waveguide layer 30; and

The upper cladding layer 50 is disposed on a side of the waveguide layer 30 away from the buried layer 20 , and the electrical structure 60 is disposed in the upper cladding layer 50 .

In some embodiments, the substrate layer 10 is a silicon substrate with a thickness of 500 microns; the buried layer 20 is a low refractive index buried layer 20, which is made of silicon dioxide, has a refractive index of 1.44, and a thickness of 4.7 microns; the waveguide layer 30 is made of a thin film lithium niobate layer, which can be specifically set as a thin film lithium niobate ridge waveguide structure, and the ridge waveguide structure includes a planar waveguide and a ridge waveguide, wherein the planar waveguide has a thickness of 150 nanometers and the ridge waveguide has a thickness of 400 nanometers; the upper cladding layer 50 is a low refractive index upper cladding layer 50, which is made of silicon dioxide, has a refractive index of 1.44, and a thickness of 3 microns. Of course, the technical solution of the present invention is not limited thereto, and the parameters of each layer structure of the coherent optical modulator chip 100 can also be set according to actual needs, and are not limited here.

In the embodiment of the present invention, the phase shifter 48 in the above embodiment includes a thermode. In some embodiments, the thermode is made of nickel-chromium alloy, has a thickness of 200 nanometers, and is 1 micron away from the waveguide layer 30. Of course, the technical solution of the present invention is not limited thereto, and the material, thickness and other parameters of the thermode can also be set according to actual needs, which is not limited here.

The present invention also proposes a phase modulator, which includes a coherent optical modulator chip 100. The specific structure of the coherent optical modulator chip 100 refers to the above-mentioned embodiment. Since the phase modulator adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

Please refer to FIG. 2 . In an embodiment of the present invention, the coherent modulator is a single polarization coherent modulator 200 . The single polarization coherent modulator 200 includes an input waveguide, a coherent optical modulator chip 100 , and an output waveguide connected in sequence.

One end of the input waveguide facing away from the coherent light modulator chip 100 is used to couple the laser light output by the tunable laser to transmit the optical signal of the TE0 mode to the double-sided directional coupler 41 of the coherent light modulator chip 100 .

Specifically, after the laser output by the tunable laser is transmitted through the optical fiber, it can enter the optical structure 40 of the coherent optical modulator chip 100 in the form of edge coupling or grating coupling; the optical signal of the TE0 waveguide mode coupled into the optical structure 40 is first coupled into the fundamental mode TE0 with equal power and phase difference of π by the bilateral directional coupler 41, and then output in two ways through two first waveguide arms 42 arranged side by side; then, the two optical signals are divided into four ways by two first beam splitters 43, and enter the third waveguide arms 451 of two parallel electro-optical modulators 45, so as to pass through the two first waveguide arms 451 of the two parallel electro-optical modulators 45. An electro-optic modulator 45 is used for modulation; then, two first combiners 46 are set, and each first combiner 46 combines the optical signals in the two third waveguide arms 451 of an electro-optic modulator 45 into one beam, so as to form two optical signals, and transmit them through the two fourth waveguide arms 461 respectively, and a π/2 phase shifter 48 is provided at one of the fourth waveguide arms 461 for phase shifting the optical signal in the fourth waveguide arm 461; finally, the two optical signals in the two fourth waveguide arms 461 are combined by a second combiner 47 and output to the output waveguide.

Please refer to FIG. 3 . In an embodiment of the present invention, the coherent modulator is a dual-polarization coherent modulator 300 . The dual-polarization coherent modulator 300 includes an input waveguide, two coherent optical modulator chips 100 and an output waveguide.

The two coherent optical modulator chips 100 are arranged in parallel between the input waveguide and the output waveguide.

Specifically, the laser output by the tunable laser is coupled into the optical waveguide via the optical fiber and the edge coupler, and then can be split into two paths and enter the two coherent optical modulator chips 100 arranged in parallel respectively to perform two separate modulations; the two optical signals modulated and output by the two coherent optical modulator chips 100 are converted into TE0 and TM0 modes by the polarization rotation combiner, and then combined into one path and output to the output waveguide.

Please refer to FIG. 3 , in an embodiment of the present invention, the dual-polarization coherent modulator 300 includes:

The input waveguide, one end of which is used to couple the laser light output by the tunable laser to transmit the optical signal of the TM0 mode;

A second beam splitter 310, which is disposed downstream of the input waveguide and is used to split the optical signal in the input waveguide into two beams, so as to be transmitted through two fifth waveguide arms disposed side by side respectively;

Two coherent light modulator chips 100, the two coherent light modulator chips 100 are arranged downstream of the second beam splitter 310, and each coherent light modulator chip 100 is arranged corresponding to one of the fifth waveguide arms; and

The polarization rotation beam combiner 320 is disposed downstream of the two coherent optical modulator chips 100 and is used for converting the optical signals output by the two coherent optical modulator chips 100 into TE0 and TM0 modes and then combining them into one beam.

The second beam splitter 310 can be set as a Y-type equalizer or a 1×2 multimode interferometer, or a polarization rotation beam splitter, which is not limited here. The polarization rotation beam combiner 320 is used to encode the two independently modulated optical signals realized by the two coherent optical modulator chips 100 into two orthogonal polarization dimensions, and finally realize dual-polarization coherent in-phase orthogonal modulation output.

The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly/indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims (10)

1. A coherent optical modulator chip, characterized in that it comprises an optical structure, wherein the optical structure comprises: A bilateral directional coupler, the bilateral directional coupler having an input end and an output end arranged in opposite directions, the output end being provided with two first waveguide arms arranged side by side, the bilateral directional coupler being used to receive an optical signal in TE0 mode from the input end, and to divide the optical signal into two beams with a phase difference of π at the output end, so as to be transmitted through the two first waveguide arms respectively; Two first beam splitters, the two first beam splitters are arranged downstream of the bilateral directional coupler, each of the first beam splitters is arranged corresponding to one of the first waveguide arms, and is used to split the optical signal in the first waveguide arm into two beams, so as to be transmitted through two second waveguide arms arranged side by side respectively; Two electro-optical modulators, the two electro-optical modulators are respectively arranged downstream of the two first beam splitters, the electro-optical modulators include two third waveguide arms arranged side by side, each of the third waveguide arms is used to transmit an optical signal in the second waveguide arm to modulate the optical signal; Two first beam combiners, the two first beam combiners are respectively arranged downstream of the two electro-optical modulators, each of the first beam combiners is respectively arranged corresponding to one of the electro-optical modulators, and are used to combine the optical signals in the two third waveguide arms into one beam for transmission through the fourth waveguide arm; a second beam combiner, which is disposed downstream of the two first beam combiners and is used to combine the optical signals in the two fourth waveguide arms into one beam; and A phase shifter is provided in one of the fourth waveguide arms and is used for performing phase shift on the optical signal in the fourth waveguide arm. 2. The coherent optical modulator chip according to claim 1, wherein the bilateral directional coupler comprises: a gradient waveguide portion, the gradient waveguide portion being configured to receive the optical signal in TE0 mode and convert the optical signal from TE0 mode to TE1 mode; and A bilateral coupling portion, one end of which is connected to the gradient waveguide portion, and the other end of which is used to connect the two first waveguide arms. The bilateral coupling portion is used to couple the optical signal in the TE1 mode into two optical signals in the TE0 mode, and the phase difference between the two optical signals is π, and the two optical signals are transmitted through the two first waveguide arms respectively. 3. The coherent optical modulator chip according to claim 2, characterized in that the coherent optical modulator chip further comprises an optical cross waveguide, wherein the optical cross waveguide comprises two cross-arranged waveguide structures, wherein the waveguide structure has a first end and a second end that are arranged opposite to each other; The two first ends are respectively connected to one of the second waveguide arms of the two first beam splitters; The two second ends are respectively connected to one of the third waveguide arms of the two electro-optic modulators. 4. The coherent optical modulator chip according to any one of claims 1 to 3, characterized in that the coherent optical modulator chip further comprises an electrical structure, wherein the electrical structure comprises: three ground electrodes, the three ground electrodes being arranged at intervals; and Two signal electrodes, each of which is arranged between two adjacent ground electrodes; A third waveguide arm is disposed between each of the ground electrodes and a signal electrode. 5. The coherent optical modulator chip according to claim 4, characterized in that the coherent optical modulator chip comprises: substrate layer; A buried layer, disposed on one side of the substrate layer; a thin-film lithium niobate waveguide layer, disposed on a side of the buried layer away from the substrate layer, the waveguide layer being formed with the optical structure; and The upper cladding layer is arranged on a side of the waveguide layer away from the buried layer, and the electrical structure is arranged in the upper cladding layer. 6. The coherent optical modulator chip according to claim 4, wherein the electrical structure is a coplanar waveguide structure; And/or, the optical structure is a thin film lithium niobate ridge waveguide structure. 7. A coherent modulator, characterized in that it comprises the coherent optical modulator chip according to any one of claims 1 to 6. 8. The coherent modulator according to claim 7, characterized in that the coherent modulator is a single polarization coherent modulator, and the single polarization coherent modulator comprises an input waveguide, a coherent optical modulator chip and an output waveguide connected in sequence; One end of the input waveguide away from the coherent light modulator chip is used to couple the laser light output by the tunable laser to transmit the optical signal of the TE0 mode to the double-sided directional coupler of the coherent light modulator chip. 9. The coherent modulator according to claim 7, characterized in that the coherent modulator is a dual-polarization coherent modulator, and the dual-polarization coherent modulator comprises an input waveguide, two coherent optical modulator chips and an output waveguide; The two coherent optical modulator chips are arranged in parallel between the input waveguide and the output waveguide. 10. The coherent modulator according to claim 9, wherein the dual-polarization coherent modulator comprises: The input waveguide, one end of which is used to couple the laser light output by the tunable laser to transmit the optical signal of TE0 mode; a second beam splitter, the second beam splitter being arranged downstream of the input waveguide and being used for splitting the optical signal in the input waveguide into two beams, so as to be transmitted respectively through two fifth waveguide arms arranged side by side; two coherent light modulator chips, the two coherent light modulator chips are arranged downstream of the second beam splitter, and each coherent light modulator chip is arranged corresponding to one of the fifth waveguide arms; and A polarization rotation beam combiner is provided downstream of the two coherent light modulator chips and is used for converting the optical signals output by the two coherent light modulator chips into TE0 mode and TM0 mode and combining them into one beam.