WO2022218178A1

WO2022218178A1 - Arrayed waveguide grating

Info

Publication number: WO2022218178A1
Application number: PCT/CN2022/084936
Authority: WO
Inventors: 邓磊; 樊航铭; 张伟伟; 王天祥; 李旭
Original assignee: 华为技术有限公司
Priority date: 2021-04-15
Filing date: 2022-04-01
Publication date: 2022-10-20
Also published as: CN115220148A

Abstract

An arrayed waveguide grating, relating to the technical field of wavelength division multiplexing for adjusting a spatial interval between different groups of output waveguides of an arrayed waveguide grating. The arrayed waveguide grating comprises: an input waveguide, an input slab waveguide, an arrayed waveguide, an output slab waveguide and a plurality of output waveguides which are coupled in sequence, wherein the plurality of output waveguides comprise at least two groups of output waveguides, a first spacing between any two adjacent output waveguides in a same group of output waveguides is the same, and output angles of different groups of output waveguides are different.

Description

An arrayed waveguide grating

This application claims the priority of the Chinese patent application with the application number 202110406039.3 and the application name "An Arrayed Waveguide Grating", which was filed with the State Intellectual Property Office on April 15, 2021, the entire contents of which are incorporated into this application by reference.

technical field

The present application relates to the technical field of wavelength division multiplexing, and in particular, to an arrayed waveguide grating.

Background technique

With the continuous development of information technology, people's demand for communication capacity continues to increase. In order to further meet the demand for communication capacity of various bandwidth services, multi-channel multiplexing technology has become an effective solution. Multiplexing technology mainly includes time division multiplexing technology, wavelength division multiplexing technology, space division multiplexing technology and hybrid multiplexing technology, among which, wavelength division multiplexing technology is one of the important multiplexing technologies. Wavelength division multiplexing technology transmits multiple independent light waves of different wavelengths simultaneously on one optical fiber to provide multiple channels and thus greatly increase the communication capacity. As shown in Figure 1, the wavelength division multiplexing system includes a wavelength division multiplexer and a wavelength division multiplexer. An optical fiber is used between the wavelength division multiplexer and the wavelength division multiplexer. The wavelength division multiplexer can Multiple independent light waves of different wavelengths are multiplexed into the same fiber. The multiple independent light waves of different wavelengths are transmitted through the fiber, and then demultiplexed into multiple independent paths at the receiving end through a wavelength demultiplexer. In FIG. 1 , multiple independent wavelengths of different wavelengths including wavelength 1 to wavelength 4 are used as an example for illustration. Among them, the wavelength division multiplexer and the wavelength division multiplexer are arrayed-waveguide grating (AWG), which usually includes five parts: input waveguide, input slab waveguide, arrayed waveguide, output slab waveguide and output waveguide.

In the prior art, as shown in FIG. 2, an arrayed waveguide grating is provided, and the spatial interval between any two adjacent output waveguides in the arrayed waveguide grating is the same, and the spatial interval refers to any two adjacent output waveguides. The distance between the output waveguides. Specifically, the input end of the output slab waveguide in the arrayed waveguide grating is a grating circle, the output end is a Rowland circle, the output ends of the arrayed waveguide are arranged on the grating circle at equal intervals, and the input ends of the output waveguide are arranged at equal intervals on the Rowland circle. , and the output waveguides are all perpendicular to the Rowland circle. In this way, by arranging the output waveguides perpendicular to the Rowland circle at equal intervals, different output waveguides can always maintain the same spatial interval in the subsequent extension process, so that a series of wavelengths with the same wavelength interval can be realized at the final output end. output of light waves. Only a part of the structure of the arrayed waveguide grating is shown in FIG. 2 , and the space interval between two adjacent output waveguides is denoted as d ₀ .

In the above arrayed waveguide grating, since the output waveguides have the same spacing on the Rowland circle and the output waveguides are all perpendicular to the Rowland circle, while ensuring the same wavelength interval of the output light waves, the space interval between the adjacent two output waveguides is ensured. d ₀ is also the same, so it cannot be applied to scenes with different spatial intervals.

SUMMARY OF THE INVENTION

The present application provides an arrayed waveguide grating, which is used to adjust the spatial interval between different groups of output waveguides of the arrayed waveguide grating.

To achieve the above object, the application adopts the following technical solutions:

A first aspect provides an arrayed waveguide grating, the arrayed waveguide grating comprising: an input waveguide, an input slab waveguide, an arrayed waveguide, an output slab waveguide and a plurality of output waveguides coupled in sequence; wherein the multiple output waveguides include at least two groups Output waveguides, the at least two groups of output waveguides may include two groups of output waveguides or more than two groups of output waveguides, for example, the at least two groups of output waveguides may include 5 groups of output waveguides. Each of the at least two sets of output waveguides may include one or more output waveguides. The first distance between any two adjacent output waveguides in the same group of output waveguides in the at least two groups of output waveguides is the same, and the first distance may be the distance between any adjacent two output waveguides in the same group of output waveguides The vertical distance, when a certain group of output waveguides in the at least two groups of output waveguides includes only one output waveguide, there is no corresponding first distance between the group of output waveguides. When a certain group of output waveguides in the at least two groups of output waveguides includes two or more output waveguides, there is a first spacing corresponding to the group of output waveguides. The first spacings corresponding to different groups of output waveguides in the at least two groups of output waveguides may be the same or different. The output angles of different groups of output waveguides in the at least two groups of output waveguides are different, and the output angle of each group of output waveguides may refer to the angle between the output waveguides in the group and a specified straight line, and the specified straight line may be a Rowland circle in the horizontal The line on which the diameter in the direction lies.

In the above technical solution, since the output angles of different groups of output waveguides of the arrayed waveguide grating are different, with the extension of the length of the output waveguides, the space interval between the adjacent two groups of output waveguides increases continuously. According to the length, the space interval between the adjacent two groups of output waveguides is set correspondingly, so that the space interval between the adjacent two groups of output waveguides can be different while ensuring the same wavelength space interval of the output light waves.

In a possible implementation manner of the first aspect, the second spacings between any adjacent two groups of output waveguides in the at least two groups of output waveguides are different. Specifically, the at least two groups of output waveguides may include two groups of output waveguides that are adjacent to each other in sequence, and are respectively represented as a first group of output waveguides and a second group of output waveguides, wherein the second spacing may specifically refer to the adjacent first group of output waveguides The linear spacing between the end of the output waveguide and the end of the second output waveguide, the first output waveguide and the second output waveguide may be located in different groups of the adjacent two groups of output waveguides, respectively. This second distance may also be referred to as a spatial spacing. In the above possible implementation manner, the second spacing between any adjacent two groups of output waveguides in the at least two groups of output waveguides is different, so that there is enough space between the output waveguides of different groups for circuit design.

In a possible implementation manner of the first aspect, the second distance is greater than the first distance. In the above possible implementation manner, a large space interval can be made between the output waveguides of different groups for circuit design, and a small first interval between the output waveguides of the same group to connect the corresponding circuit modules, which is beneficial to improve the performance of the circuit. Integration of arrayed waveguide gratings.

In a possible implementation manner of the first aspect, the output angles of different output waveguides in the same group of output waveguides are the same. In the above possible implementation manner, different output waveguides in the same group of output waveguides can be made to be parallel to each other and the first spacing is always kept the same as the length of the waveguides increases, which facilitates the connection of subsequent circuit modules.

In a possible implementation manner of the first aspect, a first group of output waveguides in the at least two groups of output waveguides includes a first output waveguide and a second output waveguide, the first output waveguide and the Rowland circle of the output slab waveguide Vertically, the second output waveguide is parallel to the first output waveguide. In the above possible implementation manners, the output waveguides arranged in the above manner can make the transmission loss of each group of output waveguides for light waves of different wavelengths the same, thereby ensuring the intensity uniformity of light waves transmitted in different groups of output waveguides.

In a possible implementation manner of the first aspect, the second spacing between any adjacent two groups of output waveguides is related to the lengths of the two groups of output waveguides. In the above possible implementation manner, by setting a larger second spacing between different groups of output waveguides of the arrayed waveguide grating, the design of subsequent circuit related modules can be facilitated after the arrayed waveguide grating.

In a possible implementation manner of the first aspect, the output end of the output slab waveguide is a Rowland circle, and the plurality of output waveguides have the same third spacing on the Rowland circle, and the third spacing may refer to the plurality of output waveguides. The curve distance on the Rowland circle between any two adjacent output waveguides in the output waveguide. In the above possible implementation manner, by setting the third spacings of adjacent output waveguides on the Rowland circle to be the same, it can be ensured that the wavelength spacings of light waves of different wavelengths in adjacent output waveguides are equal.

In a second aspect, a wavelength demultiplexer is provided, the wavelength demultiplexer includes an arrayed waveguide grating, and the arrayed waveguide grating is the arrayed waveguide provided by the first aspect or any possible implementation manner of the first aspect grating.

It can be understood that any WDM provided above includes all the contents of the arrayed waveguide grating provided above. Therefore, the beneficial effects that can be achieved can be referred to in the arrayed waveguide grating provided above. The beneficial effects will not be repeated here.

Description of drawings

1 is a schematic structural diagram of a wavelength division multiplexing system provided by an embodiment of the present application;

2 is a schematic structural diagram of an arrayed waveguide grating provided by the prior art;

3 is a schematic structural diagram of an arrayed waveguide grating;

4 is a schematic structural diagram of another arrayed waveguide grating;

FIG. 5 is a schematic structural diagram of an arrayed waveguide grating according to an embodiment of the present application;

6 is a schematic diagram of the first spacing and output angle of different groups of output waveguides in an arrayed waveguide grating provided by an embodiment of the present application;

7 is a schematic diagram of a first spacing of the same group of output waveguides and a second spacing of different groups of output waveguides in an arrayed waveguide grating according to an embodiment of the present application;

8 is a schematic diagram of the relationship between the length of the output waveguide and the second spacing in an arrayed waveguide grating according to an embodiment of the present application;

9 is a schematic diagram of a third pitch in an arrayed waveguide grating provided by an embodiment of the present application;

10 is a schematic diagram of spatial grouping of output waveguides of an arrayed waveguide grating according to an embodiment of the present application;

FIG. 11 is a schematic diagram of a spatial grouping of output waveguides of another arrayed waveguide grating provided by an embodiment of the present application;

12 is a schematic diagram of a Rowland circle and a grating circle in a slab waveguide provided by an embodiment of the present application;

13 is a schematic diagram of a slab waveguide provided by an embodiment of the present application;

14 is a schematic diagram of spatial grouping of an arrayed waveguide grating provided by an embodiment of the present application;

FIG. 15 is a schematic structural diagram of a wavelength demultiplexer provided by an embodiment of the present application.

Detailed ways

In this application, "at least one" means one or more, and "plurality" means two or more. "And/or", which describes the relationship of the associated objects, indicates that there can be three kinds of relationships, for example, "A and/or B", it can indicate that A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character "/" generally indicates that the associated objects are an "or" relationship. "At least one item(s) below" or similar expressions thereof refer to any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (a) of a, b, or c can represent: a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, c may be single or multiple .

In the embodiments of the present application, words such as "first" and "second" are used to distinguish the same items or similar items with substantially the same functions and functions. The term "coupled" is used to denote electrical connection, including direct connection through wires or terminals or indirect connection through other devices. Therefore "coupling" should be regarded as an electronic communication connection in a broad sense. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and the sequence of the first threshold is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order.

It should be noted that, in this application, words such as "exemplary" or "for example" are used to represent examples, illustrations or illustrations. Any embodiment or design described in this application as "exemplary" or "such as" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present the related concepts in a specific manner.

Embodiments of the present application provide an arrayed-waveguide grating (AWG), which can be applied to a wavelength division multiplexing system. For example, the arrayed waveguide grating can be used in a wavelength division multiplexer in the wavelength division multiplexing system. .

1 is a schematic structural diagram of a wavelength division multiplexing system provided by an embodiment of the present application. The wavelength division multiplexing system includes: a wavelength division multiplexer and a wavelength division multiplexer. The wavelength division multiplexer and the wavelength division multiplexer The multiplexers are connected by an optical fiber. Wherein, the wavelength division multiplexer can be used to multiplex multiple independent light waves of different wavelengths into the one optical fiber, and the multiplexed light waves are transmitted through one optical fiber, and the wavelength division multiplexer can be used to The multiplexed light waves in the optical fiber are demultiplexed into the multiple independent light waves of different wavelengths, thereby realizing the multiplexing and demultiplexing of the multiple independent light waves of different wavelengths. In FIG. 1, the multi-channel independent different wavelengths include 4 different wavelengths as an example for illustration, and the 4 different wavelengths are respectively represented as wavelength 1 to wavelength 4, and the light waves of the 4 different wavelengths are multiplexed by a wavelength division multiplexer , the multiplexed light waves are transmitted to the wavelength division multiplexer through the optical fiber, and the wavelength division multiplexer demultiplexes the multiplexed light waves into the light waves of the 4 different wavelengths (wavelength 1 to wavelength 4).

FIG. 3 is a schematic structural diagram of an arrayed waveguide grating. As shown in FIG. 3 , the arrayed waveguide grating includes an input waveguide, an input slab waveguide, an arrayed waveguide, an output slab waveguide and a plurality of output waveguides coupled in sequence. The input end of the input slab waveguide is a Rowland circle, the output end of the input slab waveguide is a grating circle, the input end of the output slab waveguide is a grating circle, the output end of the output slab waveguide is a Rowland circle, and the input slab waveguide is a Rowland circle. Similar to the structure of the output slab waveguide and symmetrical about the vertical axis, the input slab waveguide and the output slab waveguide can also be said to be mirror images of each other.

In addition, the input waveguide is located on the circumference of the Rowland circle of the input slab waveguide, the two ends of the arrayed waveguide are respectively located on the circumference of the grating circle of the input slab waveguide and the grating circle of the output slab waveguide, the length of the array waveguide is from The plurality of output waveguides are located on the circumference of the Rowland circle of the output slab waveguide in increments of length ΔL from bottom to top.

In addition, the input waveguide can be used to transmit the input multiplexed light wave to the input slab waveguide, and the input slab waveguide can be used to diffract the multiplexed light wave, and the diffracted light wave reaches the front end of the array waveguide and passes through the array waveguide. After the transmission of the arrayed waveguide with a length difference of ΔL, a phase difference is generated (the phase difference of different wavelengths is different), and the light waves of different wavelengths are focused by the output slab waveguide to different output waveguide positions to complete the demultiplexing function.

The arrayed waveguide grating is a passive device, which can work without power supply in the optical path. Compared with other WDM devices, it has the advantages of flexible design, low insertion loss, good filtering performance, long-term stability, and easy coupling with optical fibers. . In addition, the arrayed waveguide grating can be easily combined with active devices such as optical amplifiers and semiconductor lasers to realize monolithic integration.

Fig. 4 is a schematic structural diagram of another arrayed waveguide grating, and the spatial interval between any two adjacent output waveguides in the arrayed waveguide grating can be different. Only a part of the structure of the arrayed waveguide grating is shown in FIG. 4 , and the part of the structure includes an arrayed waveguide, an output slab waveguide and a plurality of output waveguides. The input end of the output slab waveguide is a grating circle, and the output end of the output slab waveguide is a Rowland circle.

Specifically, the output ends of the arrayed waveguides are arranged at equal intervals on the grating circle, the input ends of the plurality of output waveguides are arranged at equal intervals on the Rowland circle, and any two adjacent output waveguides have the same spacing on the Rowland circle and Denoted as d ₁ . Each of the plurality of output waveguides is perpendicular to the tangent of the intersection of the waveguide and the Rowland circle, and the plurality of output waveguides can have bending nodes at different lengths and remain parallel after bending. The spatial intervals of two adjacent output waveguides in the plurality of output waveguides are different. For example, the spatial interval between the two adjacent output waveguides shown in FIG. 4 includes d ₂ , d ₃ , d ₄ and d ₅ . For the arrayed waveguide grating shown in FIG. 4, the spatial interval between two adjacent output waveguides among the plurality of output waveguides can be set by controlling the positions of the bending nodes, so as to ensure the same wavelength interval of adjacent light waves. Then, the adjustment of the spatial interval of any adjacent output waveguides among the multiple output waveguides is realized. However, when a large space interval is required between adjacent output waveguides, the output waveguides need to be extended for a longer length, thereby increasing the area of the arrayed waveguide grating and further reducing the integration degree of the arrayed waveguide grating. In addition, the bending angles of some of the multiple output waveguides are relatively large, which will increase the bending loss of the light wave, thereby reducing the transmission performance of the arrayed waveguide grating for the light wave.

5 is a schematic structural diagram of an arrayed waveguide grating provided by an embodiment of the present application, the arrayed waveguide grating includes: an input waveguide, an input slab waveguide, an arrayed waveguide, an output slab waveguide and a plurality of output waveguides coupled in sequence; The output waveguides include at least two groups of output waveguides, the first spacing between any two adjacent output waveguides in the same group of output waveguides in the at least two groups of output waveguides is the same, and the output waveguides of different groups of the at least two groups of output waveguides have the same first spacing. The output angle is different.

Wherein, the plurality of output waveguides may include at least two output waveguides, and the at least two output waveguides may include two output waveguides or more than two output waveguides. The at least two sets of output waveguides may be obtained by dividing the plurality of output waveguides, and the at least two sets of output waveguides may include two sets of output waveguides or more than two sets of output waveguides. For example, the at least two sets of output waveguides may include five sets of output waveguides waveguide. Each of the at least two sets of output waveguides may include one or more output waveguides.

In addition, the first spacing may be a vertical distance between any two adjacent output waveguides in the same group of output waveguides. When a certain group of output waveguides in the at least two groups of output waveguides includes only one output waveguide, the group of output waveguides does not have a corresponding first spacing. When a certain group of output waveguides in the at least two groups of output waveguides includes two or more output waveguides, the group of output waveguides has a corresponding first spacing. The first spacings corresponding to different groups of output waveguides in the at least two groups of output waveguides may be the same or different.

Furthermore, the output angle of each group of output waveguides may refer to the included angle between the output waveguides in the group and a designated straight line, and the designated straight line may be a straight line where the diameter of the Rowland circle in the horizontal direction is located. For example, the at least two groups of output waveguides may include a first group of output waveguides and a second group of output waveguides, the output angle of the first group of output waveguides is β, the output angle of the second group of output waveguides is γ, and the output angle β Different from this output angle γ. Optionally, when a certain group of output waveguides includes two or more output waveguides, the output angles of different output waveguides in the same group of output waveguides are the same.

Exemplarily, the following takes FIG. 6 as an example to illustrate the first spacings and output angles of different groups of output waveguides. As shown in FIG. 6 , it is assumed that the at least two groups of output waveguides include a first group of output waveguides and a second group of output waveguides. The output angle of the first group of output waveguides is β, the first group of output waveguides includes three output waveguides that are adjacent to each other in sequence and denoted as W1 to W3, the first distance between W1 and W2 and the first distance between W2 and the The first distances between W3 are all d11. The output angle of the second group of output waveguides is γ, and the second group of output waveguides also includes three output waveguides that are adjacent to each other and are respectively denoted as W4 to W6, the first distance between W4 and W5 and the distance between W5 and W5 The first distances between the W6s are all d21. In the embodiment of the present application, d11 and d21 may be the same or different; the output angle β is different from the output angle γ, and the output angles of W1 to W3 in the first group of output waveguides are all β, and the second group of output waveguides The output angles of W4 to W6 are all γ.

It should be noted that the functions of the input waveguide, the input slab waveguide, the arrayed waveguide, the output slab waveguide and the multiple output waveguides coupled in sequence in the arrayed waveguide grating are the same as those of the arrayed waveguide grating provided in FIG. Repeat.

In the arrayed waveguide grating provided by the present application, since the output angles of different groups of output waveguides are different, with the extension of the length of the output waveguides, the interval between the adjacent two groups of output waveguides is continuously increased. The interval between adjacent two groups of output waveguides can be set according to the length, and the lengths of different groups of output waveguides can be different, so that the interval between adjacent two groups of output waveguides can be different while ensuring the same wavelength interval of the output waves. .

Further, the second spacing between any adjacent two groups of output waveguides in the at least two groups of output waveguides may be the same or different, and the second spacing may also be referred to as a spatial spacing.

Specifically, the at least two groups of output waveguides may include three groups of output waveguides that are adjacent to each other in sequence and are respectively represented as the first group of output waveguides, the second group of output waveguides, and the third group of output waveguides, then the first group of output waveguides and the second group of output waveguides The second spacing between the set of output waveguides is different from the second spacing between the second set of output waveguides and the third set of output waveguides. The second spacing may specifically refer to the straight line spacing between the ends of the adjacent first output waveguides and the ends of the second output waveguides, and the first output waveguides and the second output waveguides may be located in two adjacent groups of outputs, respectively. Different groups in the waveguide. Optionally, the second distance may be greater than the first distance.

Exemplarily, as shown in FIG. 7 , three groups of output waveguides that are adjacent in sequence are respectively represented as a first group of output waveguides, a second group of output waveguides, and a third group of output waveguides. The second distance between the first group of output waveguides and the second group of output waveguides is d31, the second distance between the second group of output waveguides and the third group of output waveguides is d32, and d31 and d32 may be different, can also be the same. Further, if the first spacing corresponding to the first group of output waveguides is d13, and the first spacing corresponding to the second group of output waveguides is d14, d31 may be greater than d13 and d14, and d32 may be greater than d13 and d14.

Further, when a certain group of output waveguides in the at least two groups of output waveguides includes multiple output waveguides, the first output waveguide among the multiple output waveguides may be perpendicular to the Rowland circle of the output slab waveguide, and the multiple output waveguides may be perpendicular to the Rowland circle. All other output waveguides except the first output waveguide may be parallel to the first output waveguide, and the first output waveguide may be the first output waveguide or the last output waveguide in the arrangement sequence of the plurality of output waveguides. Exemplarily, the at least two groups of output waveguides include a first group of output waveguides, the first group of output waveguides includes a first output waveguide and a second output waveguide, the first output waveguide is perpendicular to the Rowland circle of the output slab waveguide, and the first output waveguide is perpendicular to the Rowland circle of the output slab waveguide. Two output waveguides are parallel to the first output waveguide. The output waveguides arranged in the above manner can make the transmission loss of each group of output waveguides for light waves of different wavelengths the same, thereby ensuring the uniformity of light intensity transmitted in different groups of output waveguides.

Further, the second spacing between any adjacent two groups of output waveguides is related to the lengths of the two groups of output waveguides. Wherein, the second spacing between any adjacent two groups of output waveguides increases as the lengths of any two groups of output waveguides increase. Exemplarily, as shown in FIG. 8 , taking any adjacent first group of output waveguides and second group of output waveguides as an example, the first group of output waveguides includes a first output waveguide, and the second group of output waveguides includes a second group of output waveguides. an output waveguide, the second spacing between the first output waveguide and the second output waveguide increases as the length of the first output waveguide and the length of the second output waveguide increase. For example, when the length of the first output waveguide and the second output waveguide is L1, the second distance between the first output waveguide and the second output waveguide is d1; when the first output waveguide and the second output waveguide are When the length of the output waveguide is L2, the second distance between the first output waveguide and the second output waveguide is d2, where L2 is greater than L1 and d2 is greater than d1. By setting a larger second spacing between different groups of output waveguides of the arrayed waveguide grating, the design of subsequent circuit-related modules can be facilitated after the arrayed waveguide grating.

Further, the plurality of output waveguides included in the arrayed waveguide grating have the same third pitch on the Rowland circle. Wherein, the third distance may refer to the curve distance on the Rowland circle between any two adjacent output waveguides in the plurality of output waveguides. Exemplarily, as shown in FIG. 9 , the plurality of output waveguides include 4 output waveguides which are adjacent in sequence and are respectively denoted as a first output waveguide, a second output waveguide, a third output waveguide and a fourth output waveguide. The third distance between the first output waveguide and the second output waveguide on the Rowland circle is d51, the third distance between the second output waveguide and the third output waveguide on the Rowland circle is d52, and the third output waveguide and The third spacing of the fourth output waveguide on the Rowland circle is d53, and d51, d52 and d53 are all the same. By setting the third spacings of adjacent output waveguides on the Rowland circle to be the same, it can be ensured that the wavelength spacings of light waves of different wavelengths in adjacent output waveguides are equal.

In addition, the number of groups of the at least two groups of output waveguides can be set, and the number of output waveguides included in each group of output waveguides in the at least two groups of output waveguides can be set. Wherein, the at least two groups of output waveguides may include m groups of output waveguides, m is a positive integer greater than 2, each group of output waveguides may include n output waveguides, n is a positive integer greater than 1, the specific values of m and n are The value may be set according to actual requirements or the experience of relevant technical personnel, which is not specifically limited in this embodiment of the present application.

The number of output waveguides in different groups may be the same or different. The following two cases are used as examples to illustrate. When the number of output waveguides in different groups is different, exemplarily, as shown in FIG. 10 , it is assumed that the plurality of output waveguides include 10 output waveguides, and the 10 output waveguides are divided into four groups of output waveguides and are respectively denoted as G1 To G4, G1 may include 4 output waveguides, G2 may include 3 output waveguides, G3 may include 2 output waveguides, and G4 may include 1 output waveguide. When the number of output waveguides in different groups is the same, exemplarily, as shown in FIG. 11 , it is assumed that the plurality of output waveguides includes 16 output waveguides, and the 16 output waveguides are divided into four groups of output waveguides and are respectively denoted as G1 To G4, G1 may include 4 output waveguides, G2 may include 4 output waveguides, G3 may include 4 output waveguides, and G4 may include 4 output waveguides.

The working principle of the arrayed waveguide grating provided by the embodiment of the present application will be described in detail below. 12 is a schematic diagram of a Rowland circle and a grating circle in a slab waveguide provided by an embodiment of the present application, wherein the arrayed waveguide grating has an input slab waveguide and an output slab waveguide, and the input slab waveguide and the output slab waveguide have identical structures and are mirror images of each other Therefore, in order to explain the working principle of the arrayed waveguide grating more clearly, the Rowland circle and grating circle of the input slab waveguide and the Rowland circle and grating circle of the output slab waveguide are overlapped to form (A) in Figure 12.

In Figure 12, the center of the grating circle is point C, the radius of the Rowland circle is r, the diameter of the Rowland circle is the radius of the grating circle, that is, R=2r, and the grating circle and the Rowland circle are tangent to point O. Point O and Point P are the positions of two adjacent arrayed waveguides on the grating circle, P ₁ is the position of the input waveguide on the input slab waveguide, and the light wave from point P ₁ reaches the input slab waveguide after diffraction by the input slab waveguide The O and P points on the grating circle then enter the arrayed waveguide and are transmitted to the output slab waveguide, and then reach the P2 point _on the Rowland circle of the output slab waveguide after diffraction by the output slab waveguide.

The arrayed waveguides in the arrayed waveguide grating are distributed on the grating circle to form a grating. The grating has both the diffraction function of the grating and the focusing function of the concave mirror. The diffraction function can diffract light waves _of different wavelengths at different angles, and the focusing function can focus the light of the same wavelength to the same point. For a point P ₂ , the diffraction angle depends on its diffraction order. For the same diffraction order, the diffraction angles of different wavelengths are different, which satisfies the grating equation shown in formula (1-1):

d(sinθ-sinα)=mλ (1-1)

Among them, m is the diffraction order, and the angle α is the incident angle, which refers to the angle between the light wave and the straight line OC; λ is the wavelength of the light wave; d is the grating constant, that is, the length of PO in Figure 12; θ is the diffraction angle , is the angle between OP ₂ and OC. The specific derivation is as follows: As shown in Figure 12, the light wave emitted from point P ₁ can be divided into two light waves. The first light wave is diffracted by the input slab waveguide to reach point O, and then diffracted by the output waveguide to reach point P _2. The second beam The light wave reaches the point P through the diffraction of the input slab waveguide and then reaches the point P ₂ through the diffraction of the output waveguide. When the two light waves reach different positions of the Rowland circle of the output slab waveguide through diffraction, an optical path difference will occur. Since the distance between point P and point O is very small in practice, it can be approximated that PO is perpendicular to the connecting line OC passing through the tangent point, and OS1 is perpendicular to PP ₁ . Since ∠PP ₁ O is very small, so OP ₁ and PP ₁ The length difference of is approximately equal to PS ₁ , and formula (1-2) and formula (1-3) can be obtained according to the angle complementarity:

∠POS ₁ +∠COS ₁ =90°(PO⊥OC) (1-2)

∠P ₁ OC+∠COS ₁ =90°(P ₁ O⊥OS ₁ ) (1-3)

According to formula (1-2) and formula (1-3), formula (1-4) and formula (1-5) can be deduced:

∠P ₁ OC=∠POS ₁ =α (1-4)

PS ₁ =PO*sinα(1-5)

Similarly, PS ₂ can be assumed to be perpendicular to OP ₂ . Since ∠PP ₂ O is small, the length difference between OP ₂ and PP ₂ is approximately equal to OS ₂ . According to the principle of angle complementarity, formula (1-6) can be obtained:

OS ₂ =PO*sinθ(1-6)

It can be seen from Fig. 12 that the optical path of the first light wave can be expressed as P ₁ O+OP ₂ , and the optical path of the second light wave can be expressed as P ₁ P+PP ₂ , then the optical path difference Δ of the two light waves can be expressed as is formula (1-7):

Δ=P ₁ O+OP ₂ -(P ₁ P+PP ₂ )=P ₁ OP ₁ P+OP ₂ -PP ₂ =OS ₂ -PS ₁ =PO*sinθ-PO*sinα(1-7)

Assuming PO=d, combined with formula (1-7), the optical path difference can finally be obtained to satisfy formula (1-8):

Δ=d(sinθ-sinα) (1-8)

Since two light waves with the same wavelength will interfere in the process of transmission, the optical path difference Δ satisfies Δ=mλ and the interference is maximum, and the above formula (1-1) can be obtained by combining the formula (1-8).

FIG. 13 is a schematic diagram of a slab waveguide, (A) in FIG. 13 is an input slab waveguide, and (B) in FIG. 13 is an output slab waveguide. For the input slab waveguide, the arc on the left side of the input slab waveguide is on the Rowland circle and connected to the input waveguide, and the arc on the right side of the input slab waveguide is on the grating circle and connected to the arrayed waveguide. The output slab waveguide and the input slab waveguide are mirror images of each other, the arc on the left side of the output slab waveguide is located on the grating circle and is connected to the array waveguide, and the arc on the right side of the output slab waveguide is located on the Rowland circle and connected with the output waveguide. The arrayed waveguides are arranged at the same third pitch on the circular arc on the right side of the input slab waveguide and the circular arc on the left side of the output slab waveguide. The refractive index of the array waveguide is na , and the refractive indices of the input slab waveguide and the output slab waveguide are both n _c _.

In formula (1-1), only the optical path difference generated by the two beams of light in the slab waveguide is considered, and the refractive indices of the input slab waveguide and the output slab waveguide are not considered. It is necessary to multiply n _c on the basis of the original formula. The lengths between the arrayed waveguides are all different by ΔL, so _a new optical path difference na ΔL is introduced between adjacent grating units. In practical applications, the position of the input waveguide is located at the center of the input slab waveguide, that is, point P ₁ is located at point C in Figure 12, so the incident angle α is zero. Considering the above conditions, formula (1-1) can be changed to formula (1-10):

n _c dsinθ-n _a ΔL=mλ (1-10)

According to formula (1-10), formula (1-11) can be deduced:

In formula (1-11), na is the refractive index of the arrayed waveguide, _nc is the refractive index of the input slab waveguide and the output slab waveguide, _d is the grating constant (in practice, it represents the spacing between adjacent arrayed waveguides on the grating circle) , λ is the wavelength of the light wave, and θ is the output angle. When these parameters are determined, the output angle θ corresponding to different wavelengths can be determined according to equation (1-11), and light waves of different wavelengths can be output from the output waveguides at different positions. It can be seen that when the wavelength λ changes the same size, the output angle θ changes the same size, which corresponds to the same spacing between adjacent output waveguides on the Rowland circle.

FIG. 14 is a schematic diagram of the spatial grouping of an arrayed waveguide grating provided by an embodiment of the application, (A) in FIG. 14 only shows the output slab waveguide and multiple output waveguides of the arrayed waveguide grating, (B) in FIG. 14 ) shows a simplified model of the Rowland circle and multiple output waveguides. Taking FIG. 14 as an example, when a certain group of output waveguides includes two or more output waveguides, the arrangement of each output waveguide and the arrangement of the second spacing between different groups of output waveguides are illustrated.

As shown in (B) of FIG. 14 , the plurality of output waveguides includes 3 output waveguides and can be denoted as BC, DE and IK respectively, and the 3 output waveguides can be divided into 2 groups of output waveguides, and the two groups output The waveguides are two adjacent groups of output waveguides. Here, a simplified model of the Rowland circle and multiple output waveguides is used to describe the core method flow.

Step 1: Determine the output angle of the most edge output waveguide in the first group of output waveguides, that is, the output angle of BC in FIG. 14 . Specifically, the output angle θ of the BC is determined according to the wavelength of the light wave transmitted in the BC, and the output angle θ is determined by the formula (1-11), that is, the output angle θ is:

Step 2: Determine the output waveguide DE in the first group of output waveguides according to the most edge output waveguide BC in the first group of output waveguides. DE and BC are always parallel with the first distance between them, so the output angle of DE It is the same as the output angle of BC and both are angle θ. With the extension of the output waveguide, the first spacing corresponding to the output waveguide in the group remains the same. The output angle of DE and the output angle of BC can be expressed by formula (1-12) for:

∠EDF=∠CAG=θ (1-12)

Step 3: Determine the output waveguide at the most edge of the adjacent group, that is, IK in (B) in Figure 14. There is a certain angle between IK and DE. This angle can be freely set according to actual needs, such as IK and DE. The included angle is set to 2θ, so the spatial intervals of different groups of output waveguides are constantly increasing. Let the distance of the lateral extension line GH of the Roland circle diameter AG be L, and the distance of the spatial interval EK of different groups of output waveguides is D, then the distance D satisfies Formula (1-13):

Step 4: Determine the extension length of the waveguide according to the distance D of the spatial interval of the output waveguides of different groups. It can be seen from the formula (1-13) that after the extension length L of the output waveguide is determined, the spatial interval of the output waveguides of the different groups is determined. The distance D is also determined accordingly. Therefore, the extension length of the waveguides is adjusted according to the requirements for the spatial intervals of different groups of output waveguides, so as to realize the adjustment of the spatial intervals of different groups of output waveguides.

FIG. 15 is a schematic structural diagram of a wavelength demultiplexer provided in an embodiment of the present application, where the wavelength demultiplexer is an arrayed waveguide grating, and the arrayed waveguide grating can be any of the arrayed waveguide gratings provided above, for example, The arrayed waveguide grating can be any of the arrayed waveguide gratings provided in the above-mentioned FIG. 5 to FIG. 14 .

Optionally, the WDM further includes a plurality of photodetectors (photodetectors, PD) and a plurality of trans-impedance amplifiers (trans-impedance amplifiers, TIA), the plurality of photodetectors and the plurality of trans-impedance amplifiers An electrical connection is used between them. Among them, photodetectors can be used to convert optical signals into current signals, and transimpedance amplifiers can be used to convert current signals into voltage signals.

Finally, it should be noted that: the above are only specific embodiments of the present application, but the protection scope of the present application is not limited to this, and any changes or replacements within the technical scope disclosed in the present application should be covered by the present application. within the scope of protection of the application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

An arrayed waveguide grating, characterized in that the arrayed waveguide grating comprises: an input waveguide, an input slab waveguide, an arrayed waveguide, an output slab waveguide and a plurality of output waveguides coupled in sequence;

Wherein, the plurality of output waveguides include at least two groups of output waveguides, and the first spacing between any two adjacent output waveguides in the same group of output waveguides in the at least two groups of output waveguides is the same, and the at least two groups of output waveguides have the same first spacing. Different groups of output waveguides in the waveguide have different output angles.
The arrayed waveguide grating according to claim 1, wherein the second spacing between any adjacent two groups of output waveguides in the at least two groups of output waveguides is different.
The arrayed waveguide grating according to claim 2, wherein the second pitch is greater than the first pitch.
The arrayed waveguide grating according to any one of claims 1-3, wherein the output angles of different output waveguides in the same group of output waveguides are the same.
The arrayed waveguide grating according to any one of claims 1-4, wherein the first group of output waveguides in the at least two groups of output waveguides comprises a first output waveguide and a second output waveguide, and the first output waveguide The waveguide is perpendicular to the Rowland circle of the output slab waveguide, and the second output waveguide is parallel to the first output waveguide.
The arrayed waveguide grating according to any one of claims 1-5, characterized in that, the second spacing between any adjacent two groups of output waveguides is related to the lengths of the two groups of output waveguides.
The arrayed waveguide grating according to any one of claims 1-6, wherein the output end of the output slab waveguide is a Rowland circle, and the plurality of output waveguides have the same third spacing on the Rowland circle.
A wavelength demultiplexer, characterized in that, the wavelength demultiplexer comprises the arrayed waveguide grating according to any one of claims 1-7.