Two-dimensional coupled grating structure and its crosstalk test structure

Abstract

The present invention discloses a two-dimensional coupled grating structure and a crosstalk test structure thereof. The two-dimensional coupled grating structure comprises: a main body and a grating array, wherein the main body comprises a first incident surface and a second incident surface perpendicular to each other; the grating array is disposed in the main body, wherein gratings in the grating array are distributed along a first direction and a second direction, respectively, wherein the first direction is perpendicular to the first incident surface, and the second direction is perpendicular to the second incident surface; the grating period in the grating array along the first direction and the grating period along the second direction are different; the grating array is configured to couple a first optical signal and a second optical signal with orthogonal polarizations and output them, wherein the first optical signal is an optical signal input from the first incident surface, and the second optical signal is an optical signal input from the second incident surface. Due to the different grating periods, the center wavelengths of the polarized first and second optical signals are different, thereby making the total spectral response of the coupled output optical signal wider and reducing the influence of the grating bandwidth on optical signal attenuation.

Description

Technical Field

[0001] The present invention relates to, but is not limited to, the field of optical communications, and in particular to a two-dimensional coupled grating structure and a crosstalk test structure thereof. Background Art

[0002] Crosstalk is a crucial performance metric for components such as polarization beam splitter rotators (PBSRs) and wavelength division multiplexing (WDMs) in optical chips. During component testing, it's crucial to ensure that crosstalk values ​​remain within a certain range. Because crosstalk is noise mixed in with the optical signal, it can't be directly measured using instruments. Typically, a single polarization-coupled grating structure is connected to each output end of the component test structure. The output spectra of each structure are then compared and analyzed using optical fiber to generate a crosstalk signal curve.

[0003] The coupled grating structure contains a grating array. Due to the limited bandwidth of the grating and the rapid increase in loss at the edges of the bandwidth, the intensity of the optical signal at wavelengths close to the edge of the bandwidth is significantly reduced, drowning out the noise of the test equipment, making it impossible to accurately determine the actual value of crosstalk. To solve this problem, the center wavelength of the optical signal is usually adjusted by adjusting the fiber coupling angle to keep the wavelength of the optical signal within the wavelength range with the lowest loss as much as possible. However, different coupled grating structures have certain process tolerances. When testing large quantities of tests, the fiber coupling angle of each test structure must be adjusted one by one, which reduces test efficiency. Summary of the Invention

[0004] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0005] The embodiment of the present invention provides a two-dimensional coupled grating structure and a crosstalk test structure thereof, which can broaden the response of the total output spectrum of the coupled grating structure without adjusting the central wavelength, thereby improving the test efficiency.

[0006] In a first aspect, an embodiment of the present invention provides a two-dimensional coupled grating structure, comprising:

[0007] A main body, the main body comprising a first incident surface and a second incident surface, the first incident surface and the second incident surface being spliced ​​and perpendicular to each other;

[0008] a grating array, the grating array being disposed in the main body, the gratings in the grating array being distributed along a first direction and a second direction, respectively, the first direction being perpendicular to the first incident surface, the second direction being perpendicular to the second incident surface, and the grating period in the grating array along the first direction and the grating period along the second direction being different from each other;

[0009] The grating array is used to couple a first optical signal and a second optical signal with orthogonal polarizations and then output them. The first optical signal is an optical signal input from the first incident surface, and the second optical signal is an optical signal input from the second incident surface.

[0010] In a second aspect, an embodiment of the present invention further provides a crosstalk test structure, including:

[0011] Input raster;

[0012] a test element, wherein an input end of the test element is connected to the input grating via a third waveguide, the test element comprises at least one output end, and the output end of the test element is connected to a two-dimensional coupled grating structure as described above;

[0013] a spectroscopic element, wherein an input end of the spectroscopic element is connected to an output end of the test element via a fourth waveguide, and an output end of the spectroscopic element is connected to the first incident surface and the second incident surface respectively;

[0014] The optical splitting element is used to split the optical signal outputted from one output end of the test element into the first optical signal and the second optical signal according to a preset splitting ratio.

[0015] An embodiment of the present invention includes: a main body, the main body including a first incident surface and a second incident surface, the first incident surface and the second incident surface being spliced ​​and perpendicular to each other; a grating array, the gratings in the grating array being arranged in the main body, the gratings being distributed along a first direction and a second direction, respectively, the first direction being perpendicular to the first incident surface, the second direction being perpendicular to the second incident surface, the grating period in the grating array along the first direction and the grating period along the second direction being different; the grating array being configured to couple a first optical signal and a second optical signal with orthogonal polarizations and output them, the first optical signal being the optical signal input from the first incident surface, and the second optical signal being the optical signal input from the second incident surface. Due to the different grating periods, the center wavelengths of the polarized first and second optical signals are different, thereby making the total spectral response of the coupled output optical signal wider and reducing the effect of the grating bandwidth on optical signal attenuation.

[0016] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation to the technical solution of the present invention.

[0018] Figure 1 1 is a schematic structural diagram of a two-dimensional coupled grating structure provided by one embodiment of the present invention;

[0019] Figure 2 The output spectrum obtained by coupling polarization when the central wavelengths of the first optical signal and the second optical signal are the same;

[0020] Figure 3 is an output spectrum obtained by coupling polarization when the central wavelengths of the first optical signal and the second optical signal are different from each other;

[0021] Figure 4 is a structural diagram of a crosstalk test structure provided by another embodiment of the present invention;

[0022] Figure 5 is a schematic diagram of a crosstalk test structure in which a test element is a PBSR, provided by another embodiment of the present invention;

[0023] Figure 6 is a schematic diagram of a crosstalk test structure in which a test element is a WDM, provided by another embodiment of the present invention;

[0024] Figure 7 yes Figure 5 The output spectrum of the crosstalk test structure is shown. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] It should be noted that although the device schematics illustrate functional module divisions and the flowcharts illustrate logical sequences, in certain circumstances, the steps shown or described may be performed in a sequence that differs from the module divisions in the device or the sequence in the flowcharts. The terms "first," "second," and the like in the specification, claims, or accompanying drawings are used to distinguish similar items and are not necessarily used to describe a specific sequence or precedence.

[0027] The present invention provides a two-dimensional coupled grating structure and a crosstalk test structure thereof. The two-dimensional coupled grating structure comprises: a main body, comprising a first incident surface and a second incident surface, the first incident surface and the second incident surface being spliced ​​and perpendicular to each other; a grating array, disposed in the main body, wherein gratings in the grating array are distributed along a first direction and a second direction, respectively, the first direction being perpendicular to the first incident surface, and the second direction being perpendicular to the second incident surface; the grating period in the grating array along the first direction and the grating period along the second direction being different; the grating array is configured to couple a first optical signal and a second optical signal with orthogonal polarizations and output them, wherein the first optical signal is an optical signal input from the first incident surface, and the second optical signal is an optical signal input from the second incident surface. Due to the different grating periods, the center wavelengths of the polarized first and second optical signals are different, thereby making the total spectral response of the coupled output optical signal wider and reducing the influence of the grating bandwidth on optical signal attenuation.

[0028] The embodiments of the present invention are further described below with reference to the accompanying drawings.

[0029] like Figure 1 As shown, Figure 1 A two-dimensional coupled grating structure provided by one embodiment of the present invention includes:

[0030] The main body 100 includes a first incident surface 131 and a second incident surface 132, and the first incident surface 131 and the second incident surface 132 are perpendicular to each other;

[0031] A grating array 140 is disposed in the main body 100. The gratings in the grating array 140 are distributed along a first direction and a second direction, respectively. The first direction is perpendicular to the first incident surface 131, and the second direction is perpendicular to the second incident surface 132. The grating period in the grating array 140 along the first direction and the grating period along the second direction are different from each other.

[0032] The grating array 140 is used to couple a first optical signal and a second optical signal with orthogonal polarizations and then output them. The first optical signal is an optical signal input from the first incident surface 131 , and the second optical signal is an optical signal input from the second incident surface 132 .

[0033] It should be noted that the first incident surface 131 and the second incident surface 132 are perpendicular to each other, which can ensure that the first optical signal and the second optical signal form two mutually orthogonal polarizations that are coupled into the optical fiber, so that the light intensity and total spectrum of the output optical signal can be directly detected by the detector.

[0034] In one embodiment, the gratings in the grating array 140 are distributed along a first direction and a second direction, enabling vertical coupling of an input optical signal into the gratings. It should be noted that this embodiment does not limit the relationship between the grating period in the first direction and the grating period in the second direction; they only need to be different. Those skilled in the art are encouraged to adjust the specific values ​​based on actual needs.

[0035] It is worth noting that for a common one-dimensional single polarization coupled grating structure, the 1dB bandwidth of a single grating is determined by the following formula: Among them, η 1dB is a parameter related to optical fiber, n c is the refractive index of the upper cladding, θ is the coupling angle, A G is the grating period, dn eff (λ) / dλ is the waveguide dispersion, since the central wavelength is affected by θ and A G Influence, when the central wavelength is determined, it is difficult to adjust θ or Λ G To increase the bandwidth, if the waveguide dispersion needs to be adjusted, the only way is to change the waveguide material or use a sub-wavelength grating structure. However, this is difficult to manufacture, and conventional methods are difficult to expand the bandwidth of a one-dimensional single-polarization coupled grating. Therefore, the two-dimensional coupled grating structure of this embodiment is more structurally feasible by adjusting the grating period.

[0036] It should be noted that for the existing coupled grating structure, since the central wavelengths of the two optical signals are the same, the total output spectrum is as follows: Figure 2 As shown in FIG, it drops rapidly near the edge of the grating bandwidth, affecting the normal performance of the crosstalk test. When the grating period in the first direction and the grating period in the second direction of the grating array 140 are different, the center wavelengths of the first optical signal and the second optical signal are staggered. The spectrum of one optical signal is biased towards the region with a smaller wavelength range, and the spectrum of the other optical signal is biased towards the region with a larger wavelength range. After the total spectrum is superimposed, it is as shown in FIG. Figure 3 As shown in FIG. 1 , the decrease in the amplitude at the edge of the grating period is reduced, which is more conducive to judging the size of the crosstalk.

[0037] In one embodiment, the grating array 140 can be of any shape, such as a rectangular array or a Figure 1The square array shown can be adjusted according to actual needs. It is understandable that in order to achieve different grating periods in the first direction and the second direction in the grating array 140, the grating period in one direction can be adjusted while the grating period in the other direction remains unchanged. Alternatively, the grating can be adjusted from the existing cylindrical shape to other symmetrical shapes, such as Figure 1 The specific shape can be adjusted according to actual needs, and this embodiment does not impose too many restrictions.

[0038] In addition, in one embodiment, the two-dimensional coupled grating structure further includes a first waveguide 111 and a second waveguide 112 , the first waveguide 111 and the second waveguide 112 are perpendicular to each other, the first waveguide 111 is perpendicular to the first incident surface 131 , and the second waveguide 112 is perpendicular to the second incident surface 132 .

[0039] In one embodiment, the first waveguide 111 and the second waveguide 112 may be straight waveguides or curved waveguides, and their shapes may be adjusted according to actual transmission requirements of optical signals.

[0040] It should be noted that the first waveguide 111 and the second waveguide 112 are perpendicular to each other, which can ensure that the first optical signal can be perpendicularly incident on the first incident surface 131 and the second optical signal can be perpendicularly incident on the second incident surface 132 , thereby achieving orthogonal polarization in the grating array 140 .

[0041] Those skilled in the art will appreciate that the optical signals input through the first waveguide 111 and the second waveguide 112 may be transverse electric (TE) polarized, and the specific polarization type may be adjusted according to the test element 300 .

[0042] In addition, in one embodiment, the two-dimensional coupled grating structure further includes:

[0043] A first beam expanding waveguide 121 , which is connected between the first waveguide 111 and the first incident surface 131 ;

[0044] The second beam expanding waveguide 122 is connected between the second waveguide 112 and the second incident surface 132 .

[0045] In one embodiment, the first beam expanding waveguide 121 and the second beam expanding waveguide 122 may be waveguides with a trapezoidal cross section, which can expand the optical signals input by the first waveguide 111 and the second waveguide 112 to the incident plane respectively, so that the first optical signal and the second optical signal are polarized in the grating array 140. For example, Figure 1In the manner shown, both ends of the output side of the first beam expanding waveguide 121 are connected to both ends of the first incident surface 131 . The specific beam expanding ranges of the first beam expanding waveguide 121 and the second beam expanding waveguide 122 can be adjusted according to actual needs and will not be described in detail here.

[0046] In addition, in one embodiment, the main body 100 of the two-dimensional coupled grating structure further includes a first exit surface 151 and a second exit surface 152, the first exit surface 151 and the second exit surface 152 are perpendicular to each other, the first exit surface 151 and the first incident surface 131 are parallel to each other, and the second exit surface 152 and the second incident surface 132 are parallel to each other.

[0047] In one embodiment, if Figure 1 As shown, the cross section of the main body 100 may be square or in other shapes, which may be adjusted according to the actual shape of the grating array 140 so as to achieve orthogonal polarization of the optical signal.

[0048] It should be noted that, in actual use, instead of connecting the optical fiber arrays to the first exit surface 151 and the second exit surface 152 respectively, the optical fiber arrays may be connected to the first incident surface 131 and the second incident surface 132 at two ends away from each other, and the first optical signal and the second optical signal are polarized and coupled in the grating array 140 and then output. For example, Figure 4 The main body 100 is placed in the manner shown in FIG.

[0049] In addition, in one embodiment, the duty cycle along the first direction and the duty cycle along the second direction of the grating array 140 are different from each other.

[0050] In one embodiment, different grating periods can be achieved by varying the grating shape or by varying the duty cycle of the gratings in different directions. For example, the duty cycle of each grating in the first direction can be A, while the duty cycle of each grating in the second direction can be B, with the values ​​of A and B being different. This is not further described here. It should be noted that to ensure coupled polarization, the gratings in the same direction are equidistantly spaced, and this is not further described here.

[0051] In addition, reference Figure 4 Another embodiment of the present invention further provides a crosstalk test structure, comprising:

[0052] An input polarization structure 200 , wherein a polarization grating is provided in the input polarization structure 200 ;

[0053] A test element 300, wherein an input end of the test element 300 is connected to the input polarization structure 200 via the third waveguide 210, and the test element 300 includes at least one output end, wherein the output end of the test element 300 is connected to a two-dimensional coupled grating structure as described in the above embodiment;

[0054] A spectroscopic element 160, wherein the input end of the spectroscopic element 160 is connected to the output end of the test element 300 via a fourth waveguide 170, and the output end of the spectroscopic element 160 is connected to the first incident surface 131 and the second incident surface 132 respectively;

[0055] The optical splitting element 160 is used to split the optical signal outputted from one output end of the test element 300 into a first optical signal and a second optical signal according to a preset splitting ratio.

[0056] It should be noted that this embodiment only improves the crosstalk test structure, and the specific test method can adopt the method in the prior art, which will not be described in detail here.

[0057] It should be noted that the crosstalk test structure of this embodiment can be applied to various components of optical chips, such as polarization beam splitter rotator (PBSR) and wavelength division multiplexing (WDM). Those skilled in the art are motivated to add or reduce the above-mentioned two-dimensional coupled grating structure according to the specific test components.

[0058] It should be noted that the spectroscopic element 160 can be any spectroscopic element, such as a common 2*1 multi-mode interference structure, as long as it can realize spectroscopic analysis according to the required spectroscopic ratio, and this embodiment does not impose any limitation thereto.

[0059] The following are combined Figure 5 and Figure 6 , structural examples are given to illustrate the application of the crosstalk test structure to different test elements.

[0060] exist Figure 5In the illustrated embodiment, the test element 300 is a PBSR, and the input polarization structure 200 is connected to the polarization beam splitting rotation element 310 through the third waveguide 210. The polarization beam splitting rotation element is used to separate the input optical signal according to different polarizations and output them as TE polarization. The structure of the polarization beam splitting rotation element 310 can be a common structure in the prior art and will not be repeated here. The output end of the polarization beam splitter rotator 310 is connected to the test element 300. Since the PBSR has two output ends, one of the output ends is connected to the spectroscopic element 160a through the fourth waveguide 170a, and the two output ends of the spectroscopic element 160a are respectively connected to the first waveguide 111a and the second waveguide 112a, and the first waveguide 111a and the second waveguide 112a are connected to the main body 100a; the other output end is connected to the spectroscopic element 160b through the fourth waveguide 170b, and the two output ends of the spectroscopic element 160b are respectively connected to the first waveguide 111b and the second waveguide 112b, and the first waveguide 111b and the second waveguide 112b are connected to the main body 100b. The total output spectrum can be referred to Figure 3 The total spectrum shown in effectively reduces the effect of the grating bandwidth.

[0061] exist Figure 6 In the embodiment shown, the test element 300 is a WDM, and the input polarization structure 200 is connected to the test element 300 via the third waveguide 210. Since the WDM has four output ends, the connection method is as follows: connecting to the splitter element 160a via the fourth waveguide 170a, the two output ends of the splitter element 160a are connected to the first waveguide 111a and the second waveguide 112a respectively, and the first waveguide 111a and the second waveguide 112a are connected to the main body 100a; connecting to the splitter element 160b via the fourth waveguide 170b, the two output ends of the splitter element 160b are connected to the first waveguide 111b and the second waveguide 112a respectively. 12b, the first waveguide 111b and the second waveguide 112b are connected to the main body 100b; the light splitting element 160c is connected through the fourth waveguide 170c, the two output ends of the light splitting element 160c are connected to the first waveguide 111c and the second waveguide 112c, respectively, and the first waveguide 111c and the second waveguide 112c are connected to the main body 100c; the light splitting element 160d is connected through the fourth waveguide 170d, the two output ends of the light splitting element 160d are connected to the first waveguide 111d and the second waveguide 112d, respectively, and the first waveguide 111d and the second waveguide 112d are connected to the main body 100d. The total output spectrum can be referred to Figure 7 As shown, Figure 7 The uppermost curve is the spectrum of the output light, which effectively reduces the influence of the grating bandwidth.

[0062] In addition, in one embodiment, the polarization grating in the input polarization structure 200 is a single polarization grating.

[0063] In one embodiment, the grating in the input polarization structure 200 may be any existing single polarization grating that can realize polarization input of the optical signal from the optical fiber, which will not be described in detail here.

[0064] It should be noted that when the transmission spectrum of the input polarization structure 200 is T1(λ), ​​after the optical signal is input to the test element 300 and further polarized into the two-dimensional coupling grating structure, the center wavelength difference between the first optical signal and the second optical signal is Δλ, then the transmission spectrum of the polarization coupling structure after translation is The total transmission spectrum is The influence of grating bandwidth on transmission spectrum is effectively reduced.

[0065] In addition, in one embodiment, the two-dimensional coupled grating structure further includes a first waveguide 111 and a second waveguide 112, the first waveguide 111 is connected to the first incident surface 131, the second waveguide 112 is connected to the second incident surface 132, and its spectroscopic element 160 is connected to the first waveguide 111 and the second waveguide 112 respectively.

[0066] In one embodiment, the output direction of the light splitting element 160 can be arbitrary, for example Figure 4 The output direction of the optical splitter shown in the figure is 45 degrees, so the first waveguide 111 and the second waveguide 112 are respectively set to be bent at 90 degrees, so that the first optical signal and the second optical signal can be vertically incident on the grating array 140, avoiding the first optical signal and the second optical signal being not vertically orthogonal and affecting the reception of the optical fiber.

[0067] In one embodiment, the splitting ratio of the splitting element 160 can be arbitrary and can be adjusted according to the wavelength requirements of the optical signal. For example, if it is necessary to ensure that the central wavelengths of the first optical signal and the second optical signal are the same, the splitting ratio of the splitting element 160 is set to 50%. Those skilled in the art are motivated to adjust it according to actual needs, and will not be elaborated here.

[0068] In addition, in one embodiment, the input direction of the beam splitting element 160 and the input direction of the input polarization structure 200 are parallel to each other.

[0069] In one embodiment, the input direction of the optical splitter element 160 and the input direction of the input polarization structure 200 are parallel to each other, which can ensure that the light input direction of the third waveguide 210 and the light output direction of the fourth waveguide 170 are perpendicular to the test element 300, providing a structural basis for connecting the crosstalk test structure to the vertical optical fiber array used for testing. It should be noted that the spacing between the third waveguide 210 and the fourth waveguide 170 can be adjusted according to actual needs. When multiple fourth waveguides 170 are provided, for example Figure 5 As shown, the third waveguide 210, the fourth waveguide 170a and the fourth waveguide 170b are equidistantly distributed. Figure 6As shown, the third waveguide 210, the fourth waveguide 170a, the fourth waveguide 170b, the fourth waveguide 170c and the fourth waveguide 170d are equidistantly distributed, and the specific distance values ​​can be adjusted according to the actual optical fiber array.

[0070] In addition, in one embodiment, the input end of the input polarization structure 200 and the output end of the main body 100 are located in the same plane.

[0071] It should be noted that in a common vertical fiber array, several optical fibers are parallel and vertically distributed with respect to the crosstalk test structure, and their input and output surfaces are on the same plane. Therefore, the input end of the input polarization structure 200 and the output end of the main body 100 are located on the same plane, as shown in FIG. Figure 5 As shown, the input polarization structure 200 and the main bodies 100a and 100b are arranged in a straight line, so that the crosstalk test structure can be connected to the optical fibers in the vertical optical fiber array, providing a structural basis for the test.

[0072] It should be noted that the output end of the input polarization structure 200 is connected to the third waveguide 210. Therefore, the input end of the input polarization structure 200 is the other end connected to the third waveguide 210. The specific shape of the input end can be adjusted according to actual needs and is not limited in this embodiment.

[0073] It should be noted that the output end of the main body 100 can be the endpoint where the first incident surface 131 and the second exit surface 152 are connected, and the endpoint where the second incident surface 132 and the first exit surface 151 are connected. The connection end formed by the above two endpoints can be connected to the vertical optical fiber array.

[0074] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above implementation. Those skilled in the art can make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of the present invention.

Claims

1. A crosstalk test structure, comprising: An input polarization structure, wherein a polarization grating is provided in the input polarization structure; A test element, wherein an input end of the test element is connected to the input polarization structure via a third waveguide, the test element comprises at least one output end, and the output end of the test element is connected to a two-dimensional coupled grating structure; a light-splitting element, wherein an input end of the light-splitting element is connected to an output end of the test element via a fourth waveguide; The optical splitting element is used to split the optical signal outputted from one output end of the test element into a first optical signal and a second optical signal according to a preset splitting ratio; Wherein, the two-dimensional coupled grating structure includes: a main body, the main body comprising a first incident surface and a second incident surface, the first incident surface and the second incident surface being perpendicular to each other, and the output end of the light-splitting element being connected to the first incident surface and the second incident surface respectively; a grating array, the grating array being disposed in the main body, the gratings in the grating array being distributed along a first direction and a second direction, respectively, the first direction being perpendicular to the first incident surface, the second direction being perpendicular to the second incident surface, and the grating period in the grating array along the first direction and the grating period along the second direction being different from each other; The grating array is used to couple a first optical signal and a second optical signal with orthogonal polarizations and then output them. The first optical signal is an optical signal input from the first incident surface, and the second optical signal is an optical signal input from the second incident surface.

2. The crosstalk test structure according to claim 1, wherein: The two-dimensional coupled grating structure further includes a first waveguide and a second waveguide, wherein the first waveguide and the second waveguide are perpendicular to each other, the first waveguide is perpendicular to the first incident surface, and the second waveguide is perpendicular to the second incident surface.

3. A crosstalk test structure according to claim 2, characterized in that: The two-dimensional coupled grating structure further includes: a first beam expanding waveguide connected between the first waveguide and the first incident surface; A second beam expanding waveguide is connected between the second waveguide and the second incident surface.

4. The crosstalk test structure according to claim 3, wherein: The main body further includes a first emitting surface and a second emitting surface, the first emitting surface and the second emitting surface are perpendicular to each other, the first emitting surface and the first incident surface are parallel to each other, and the second emitting surface and the second incident surface are parallel to each other.

5. The crosstalk test structure according to claim 1, wherein: The duty cycle of the grating array along the first direction and the duty cycle along the second direction are different from each other.

6. The crosstalk test structure according to claim 1, wherein: The polarization grating in the input polarization structure is a single polarization grating.

7. The crosstalk test structure according to claim 1, wherein: The two-dimensional coupled grating structure further includes a first waveguide and a second waveguide, the first waveguide is connected to the first incident surface, the second waveguide is connected to the second incident surface, and the spectroscopic element is connected to the first waveguide and the second waveguide respectively.

8. The crosstalk test structure according to claim 7, wherein: The input direction of the light splitting element is parallel to the input direction of the input polarization structure.

9. The crosstalk test structure according to claim 8, characterized in that: The input end of the input polarization structure and the output end of the main body are located in the same plane.

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