Star waveguide and fiber optic communication system

Abstract

The application provides a star waveguide and an optical fiber communication system, wherein the star waveguide comprises a silica cladding layer, a central waveguide and a plurality of satellite waveguides arranged in the silica cladding layer; the central waveguide is used for receiving input light, and is arranged in a cuboid structure, and the propagation direction of the input light is parallel to the length direction of the central waveguide; the plurality of satellite waveguides are arranged in the silica cladding layer, and are arranged in a cuboid structure; the satellite waveguides are arranged on both sides of the central waveguide in the width direction, and are arranged on both sides of the central waveguide in the height direction; the plurality of satellite waveguides are arranged in parallel with the central waveguide in the propagation direction of the input light; the plurality of satellite waveguides are coupled by the central waveguide through evanescent waves, the coupling efficiency of the plurality of satellite waveguides is the same, and the input light coupled out is output by the plurality of satellite waveguides. The star waveguide can replace a beam splitter, so that the loss is reduced.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, specifically to a star waveguide and optical fiber communication system. Background Technology

[0002] As one of the most basic devices in integrated on-chip photonics systems, beam splitters are widely used in many optical circuits. Their main function is to split the input light into two or more parts. Beam splitters play a very important role in interferometers, laser systems, space optical communication systems, and other applications.

[0003] However, when a beam splitter splits light, for example, when splitting the input light into four parts, it is usually a cascaded design consisting of four directional couplers connected in series. The input beam will be split by four independent directional couplers. At each directional coupler, mode mismatch and scattering will occur at the input and output interfaces of each directional coupler. That is, the beam splitter that splits the light into four parts has eight transition interfaces and four independent propagation segments. Moreover, the manufacturing defect is that each coupler has independent loss. Therefore, the total loss is the sum of the losses of each stage. As a result, the loss of the beam splitter increases, leading to the instability of the output beam. Summary of the Invention

[0004] The primary objective of this invention is to provide a star waveguide that reduces optical loss.

[0005] A second objective of this invention is to provide an optical fiber communication system that utilizes the aforementioned star waveguide.

[0006] To achieve the first objective of this invention, the star-shaped waveguide provided by this invention is characterized by comprising a silica cladding layer, within which a central waveguide and multiple satellite waveguides are disposed; the central waveguide is used to receive input light and is configured as a cuboid structure, with the propagation direction of the input light parallel to the length direction of the central waveguide; multiple satellite waveguides are disposed within the silica cladding layer and are also cuboid structures; satellite waveguides are disposed on both sides of the central waveguide in the width direction and on both sides of the central waveguide in the height direction, and the multiple satellite waveguides are arranged parallel to the central waveguide in the propagation direction of the input light; the multiple satellite waveguides are evanescently coupled through the central waveguide, with each satellite waveguide having the same coupling efficiency, and the multiple satellite waveguides output the coupled input light.

[0007] As can be seen from the above scheme, the input light enters from the input end of the central waveguide and propagates along the direction of input light propagation. During the propagation process in the central waveguide, multiple satellite waveguides are evanescently coupled through the central waveguide, thereby obtaining a split beam from the four satellite waveguides, thus completing the beam splitting. Loss occurs during the evanescent coupling process. Specifically, the loss of the star-shaped waveguide of this invention includes the loss at the input end face and the output end face of the star-shaped waveguide, as well as the loss in the coupling propagation region of one star-shaped waveguide. Compared with existing beam splitters, it reduces the losses at the input end and the output end of three couplers, thereby reducing the loss during beam splitting and maintaining the accuracy of waveguide beam splitting.

[0008] In a further embodiment, the central waveguide has a first attenuation coefficient in the width direction and a second attenuation coefficient in the height direction. The satellite waveguide and the central waveguide are provided with a first edge spacing in the width direction and a second edge spacing in the height direction. The product of the first attenuation coefficient and the first edge spacing is equal to the product of the second attenuation coefficient and the second edge spacing.

[0009] Therefore, it can be seen that the coupling efficiency between multiple satellite waveguides is equal by determining the edge spacing and attenuation coefficient.

[0010] In a further embodiment, multiple satellite waveguides include a first satellite waveguide, a second satellite waveguide, a third satellite waveguide, and a fourth satellite waveguide; the first satellite waveguide is located at the first end of the central waveguide, the second satellite waveguide is located at the second end of the central waveguide, the third satellite waveguide is located at the third end of the central waveguide, and the fourth satellite waveguide is located at the fourth end of the central waveguide; the first and second satellite waveguides are arranged along the width direction of the central waveguide, and the third and fourth satellite waveguides are arranged along the height direction of the central waveguide.

[0011] Therefore, since multiple satellite waveguides are set at the four ends of the central waveguide, the coupling efficiency can be adjusted by adjusting the width or height of the central waveguide and the spacing between the central waveguide and the satellite waveguides.

[0012] In a further embodiment, the first spacing between the first satellite waveguide and the third satellite waveguide is greater than the first distance.

[0013] Therefore, by setting the first spacing between the first satellite waveguide and the third satellite waveguide to be greater than the first distance, the distance between the first satellite waveguide and the third satellite waveguide is made to exceed the attenuation wave range, thereby reducing the cross coupling between the first satellite waveguide and the third satellite waveguide.

[0014] In a further proposed design, multiple satellite waveguides and the central waveguide are composed of silicon nitride.

[0015] It is evident that silicon nitride can make the optical field easier to extend, greatly improving coupling efficiency and reducing losses.

[0016] In a further design, the height of the central waveguide and each satellite waveguide is 400 nanometers, the width of the central waveguide and each satellite waveguide is 800 nanometers, and the length of the central waveguide and each satellite waveguide is 300 micrometers.

[0017] It can be seen that the length of the central waveguide and multiple satellite waveguides is 300 micrometers. Since the refractive index of silicon nitride is lower than that of silicon, silicon nitride requires a longer coupling length than silicon.

[0018] In a further design, the central waveguide is equipped with a receiving surface that is perpendicular to the propagation direction of the input light.

[0019] Therefore, the receiving surface is used to receive the input light.

[0020] To achieve the second objective, the present invention provides an optical fiber communication system that utilizes the star waveguide described above. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of an embodiment of the star waveguide of the present invention.

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0023] The star-shaped waveguide provided by this invention receives input light through a central waveguide 12, while multiple satellite waveguides are evanescently coupled through the central waveguide 12, thereby obtaining a split beam from the four satellite waveguides and completing the beam splitting. Since the loss of the star-shaped waveguide of this invention includes the loss at the input and output ends of the star-shaped waveguide, as well as a loss during transmission in the coupling region, the loss during beam splitting is reduced, ensuring the accuracy of waveguide beam splitting.

[0024] Star waveguide example: See Figure 1 In this embodiment, the star-shaped waveguide includes a silica cladding layer 11, within which a central waveguide 12 and multiple satellite waveguides are disposed. The central waveguide 12 and the multiple satellite waveguides are embedded in the silica cladding layer 11.

[0025] The central waveguide 12 is used to receive the input light. The central waveguide 12 is configured as a cuboid structure. The propagation direction of the input light is parallel to the length direction z of the central waveguide 12, the width direction y of the central waveguide, and the height direction x of the central waveguide.

[0026] Multiple satellite waveguides are housed within the silica cladding layer 11, and all satellite waveguides have a cuboid structure. The shape of these satellite waveguides is identical to that of the central waveguide 12.

[0027] The central waveguide 12 has satellite waveguides on both sides in the width direction y and on both sides in the height direction x. Multiple satellite waveguides are arranged parallel to the central waveguide 12 in the direction of input light propagation. Specifically, the multiple satellite waveguides include a first satellite waveguide 131, a second satellite waveguide 133, a third satellite waveguide 134, and a fourth satellite waveguide 132. The first satellite waveguide 131 is located at the first end of the central waveguide 12, the second satellite waveguide 133 is located at the second end of the central waveguide 12, the third satellite waveguide 134 is located at the third end of the central waveguide 12, and the fourth satellite waveguide 132 is located at the fourth end of the central waveguide 12. The first satellite waveguide 131 and the second satellite waveguide 133 are arranged along the width direction of the central waveguide 12, and the third satellite waveguide 134 and the fourth satellite waveguide 132 are arranged along the height direction of the central waveguide 12.

[0028] The central waveguide 12 and each satellite waveguide have a height of 400 nanometers and a width of 800 nanometers, which allows the central waveguide to have a first attenuation coefficient k in the width direction. y Approximately 2.1 μm - ¹, The central waveguide 12 has a second attenuation coefficient k in the height direction. x Approximately 1.4 μm - ¹.

[0029] The central waveguide 12 and multiple satellite waveguides are 300 micrometers long. Because the central waveguide and multiple satellite waveguides are 300 micrometers long, and because silicon nitride has a lower refractive index than silicon, silicon nitride requires a longer coupling length compared to silicon.

[0030] Multiple satellite waveguides are coupled by evanescent wave through a central waveguide 12, and the coupling efficiency of the multiple satellite waveguides is the same. To ensure that the coupling efficiency of the multiple satellite waveguides is the same, the central waveguide 12 has a first attenuation coefficient k in the width direction. y The central waveguide 12 has a second attenuation coefficient k in the height direction. x A first edge spacing g is provided between the satellite waveguide and the central waveguide 12 in the width direction. y A second edge spacing g is provided between the satellite waveguide and the central waveguide 12 in the height direction. x First attenuation coefficient k y Multiply by the first edge spacing g y The product of these two factors equals the second attenuation coefficient g. y Multiply by the second edge spacing g xThe product of . Wherein, the edge spacing is the distance between the starting point of the central waveguide 12 near the target satellite waveguide and the ending point of the target satellite waveguide near the central waveguide 12.

[0031] Since the first satellite waveguide 131 and the second satellite waveguide 133 are positioned opposite each other along the width direction of the central waveguide 12, the attenuation coefficients of the first satellite waveguide 131 and the second satellite waveguide 133 are the same, which is the first attenuation coefficient k. y Since the third satellite waveguide 134 and the fourth satellite waveguide 132 are positioned opposite each other along the height direction of the central waveguide 12, their attenuation coefficients are the same, i.e., the second attenuation coefficient k. x .

[0032] To ensure that the coupling efficiency of multiple satellite waveguides is the same, the coupling efficiency of the star-shaped waveguides positioned along the width direction of the central waveguide 12 must be the same as the coupling efficiency of the star-shaped waveguides positioned along the height direction of the central waveguide 12. Specifically, the coupling efficiency between the satellite waveguides positioned along the height direction of the central waveguide 12 and the central waveguide must be equal to the coupling efficiency between the satellite waveguides positioned along the width direction of the central waveguide 12 and the central waveguide. ,in, The coupling efficiency between the satellite waveguide and the central waveguide, which is positioned along the height direction of the central waveguide 12, is determined. This refers to the coupling efficiency between the satellite waveguide and the central waveguide, which is positioned along the width of the central waveguide 12. The coupling coefficient is exponentially related to the attenuation coefficient and the edge spacing. ,in, For index, This is the second attenuation coefficient. Second edge spacing. And ,so, The first attenuation coefficient, This is the first edge spacing. Because... ,so equal ,so equal .

[0033] When all satellite waveguides in the width direction adopt the first edge spacing g y In the height direction, the satellite waveguides all employ a second edge spacing g. x At this point, the coupling efficiency of the four satellite waveguides is the same. This identical coupling efficiency ensures that the energy exchange efficiency of the satellite waveguides is completely consistent, thus maximizing the fidelity of matching the coupling coefficients of all satellite waveguides.

[0034] Therefore, the central waveguide 12 and the satellite waveguide are cuboids, and the parameter of the first edge spacing g can be adjusted. y Second edge spacing g x Compared to cylindrical waveguides, it has more adjustable parameters and a higher degree of freedom in adjustment.

[0035] The first spacing between the first satellite waveguide and the third satellite waveguide is greater than a first distance, wherein the first spacing between the first satellite waveguide and the third satellite waveguide is... ,in, This is the distance between the midpoint of the first satellite waveguide and the midpoint of the central waveguide. This is the distance between the midpoint of the third satellite waveguide and the midpoint of the central waveguide. Since the amplitude of the attenuation field decays exponentially, i.e. ,in, This is the first spacing. This is the attenuation coefficient. Because... and The difference is not significant, so... and When the value is D, the first spacing is... Therefore, the coupling strength is based on The multiplier is reduced, and in this embodiment, multiple satellite waveguides and the central waveguide 12 are composed of silicon nitride, therefore, Approximately 1.4 to 2.1 μm - ¹, and D is approximately 300 to 500 nm, so when At the nanometer level, the distance between the first and third satellite waveguides exceeds the attenuation wave range, reducing the cross-coupling between them. Therefore, the first distance is... The first spacing must be greater than 1.07 micrometers.

[0036] Specifically, the second spacing between the first and fourth satellite waveguides is greater than the first spacing, the third spacing between the second and fourth satellite waveguides is greater than the first spacing, and the first spacing between the second and third satellite waveguides is greater than the first spacing.

[0037] Multiple satellite waveguides and the central waveguide 12 are composed of silicon nitride. The refractive index of silicon nitride is between that of silicon dioxide and silicon, which makes the optical field easier to spread, greatly improving coupling efficiency and reducing loss.

[0038] The central waveguide 12 is provided with a receiving surface 121, which is perpendicular to the propagation direction of the input light. The input light enters from the receiving surface 121 and propagates along the length z direction of the central waveguide 12.

[0039] Each satellite waveguide is provided with an output terminal. Specifically, the first satellite waveguide 131 is provided with a first output terminal 1311, the second satellite waveguide 133 is provided with a second output terminal 1331, the third satellite waveguide 134 is provided with a third output terminal 1341, and the fourth satellite waveguide 132 is provided with a fourth output terminal 1321.

[0040] Specifically, the star waveguide is provided with an input end face 111 and an output end face 112, with a receiving end face 121 disposed on the input end face 111 and the output end face disposed on the output end face 112.

[0041] The central waveguide 12 and the satellite waveguides have the same length. Therefore, after the central waveguide 12 receives the input light, multiple satellite waveguides undergo evanescent wave coupling through it during transmission. This results in four satellite waveguides obtaining a split beam, i.e., the coupled input light, thus completing the beam splitting. The split beam is then output from the output end of the satellite waveguide. Loss occurs during the evanescent wave coupling process. The loss in the star-shaped waveguide of this invention includes scattering loss at the input and output faces of the star-shaped waveguide, as well as loss in a coupling region. Compared to a beam splitter, this reduces the loss at the input ends of three couplers, thereby reducing the loss during beam splitting and maintaining the accuracy of waveguide beam splitting.

[0042] Furthermore, since all satellite waveguides have the same coupling efficiency to the central waveguide, and since all satellite waveguides are parallel to the central waveguide, all satellite waveguides maintain a fixed phase relationship with the central waveguide. This allows for interferometric signal superposition between the satellite waveguides and the central waveguide. Also, because the coupling efficiency is the same for all satellite waveguides, the optical power obtained by each satellite waveguide is the same, avoiding overcoupling in one pair of satellite waveguides and undercoupling in another pair. This ensures entanglement fidelity and signal-to-noise ratio, and reduces errors.

[0043] Example of an optical fiber communication system: The optical fiber communication system in this embodiment uses the star waveguide of the star waveguide embodiment described above.

[0044] The above are merely preferred embodiments of the present invention, but the design concept of the invention is not limited thereto. Without departing from the concept of the present invention, many other equivalent embodiments may be included. Those skilled in the art can make various obvious changes, readjustments and substitutions without departing from the protection scope of the present invention.

Claims

1. A star-shaped waveguide, characterized in that, It includes a silica cladding layer, within which a central waveguide and multiple satellite waveguides are disposed; The central waveguide is used to receive input light. The central waveguide is configured as a cuboid structure, and the propagation direction of the input light is parallel to the length direction of the central waveguide. Multiple satellite waveguides are disposed within the silica cladding layer, and the multiple satellite waveguides are cuboid structures; The central waveguide has satellite waveguides on both sides in the width direction and satellite waveguides on both sides in the height direction. The satellite waveguides are arranged parallel to the central waveguide in the direction of propagation of the input light. Multiple satellite waveguides are coupled by evanescent wave through the central waveguide, and the coupling efficiency of each satellite waveguide is the same. The input light is coupled from the outputs of multiple satellite waveguides; The central waveguide has a first attenuation coefficient in the width direction and a second attenuation coefficient in the height direction. The satellite waveguide in the width direction is provided with a first edge spacing from the central waveguide, and the satellite waveguide in the height direction is provided with a second edge spacing from the central waveguide. The product of the first attenuation coefficient and the first edge spacing is equal to the product of the second attenuation coefficient and the second edge spacing. The plurality of satellite waveguides include a first satellite waveguide, a second satellite waveguide, a third satellite waveguide, and a fourth satellite waveguide; The first satellite waveguide is disposed at the first end of the central waveguide, the second satellite waveguide is disposed at the second end of the central waveguide, the third satellite waveguide is disposed at the third end of the central waveguide, and the fourth satellite waveguide is disposed at the fourth end of the central waveguide. The first satellite waveguide and the second satellite waveguide are arranged opposite each other along the width direction of the central waveguide, and the third satellite waveguide and the fourth satellite waveguide are arranged opposite each other along the height direction of the central waveguide.

2. The star waveguide according to claim 1, characterized in that: The first spacing between the first satellite waveguide and the third satellite waveguide is greater than the first distance, which is 1.07 micrometers.

3. The star waveguide according to claim 1 or 2, characterized in that: The multiple satellite waveguides and the central waveguide are all composed of silicon nitride.

4. The star waveguide according to claim 1 or 2, characterized in that: The central waveguide and each of the satellite waveguides have a height of 400 nanometers, a width of 800 nanometers, and a length of 300 micrometers.

5. The star waveguide according to claim 1 or 2, characterized in that: The central waveguide is provided with a receiving surface, which is perpendicular to the propagation direction of the input light.

6. An optical fiber communication system, wherein the optical fiber communication system uses the star waveguide as described in any one of claims 1 to 5.

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