Three-dimensional waveguide chip, preparation method thereof and single-multiple core fiber coupler

Abstract

The application relates to the technical field of optical communication, in particular to a three-dimensional waveguide chip, a preparation method thereof and a single-multiple core optical fiber coupler. The three-dimensional waveguide chip comprises a plurality of optical waveguides with equal diameters, an integrated fiber core bundle, a first end of the fiber core bundle is composed of linear arrangement of the optical waveguides, and a second end of the fiber core bundle is composed of circumferential arrangement of the optical waveguides or composed of central and circumferential arrangement; a three-dimensional coordinate system is established with the center of the fiber core bundle at the first end as an origin, an extension direction of the first end to the second end as an x-axis, a linear arrangement direction of the optical waveguides as a z-axis, and a direction perpendicular to the x-axis and the z-axis as a y-axis; the coordinates of the optical waveguides satisfy the following formula: wherein L is a distance between the first end and the second end, a is a y value of the center of the optical waveguide at the second end, b is a difference between a z value of the optical waveguide at the first end and a z value of the optical waveguide at the second end, and c is the z value of the optical waveguide at the first end.

Description

Technical Field

[0001] This application relates to the field of optical communication technology, and in particular to a three-dimensional waveguide chip and its fabrication method, and a single-core or multi-core optical fiber coupler. Background Technology

[0002] With the rapid development of mobile internet, cloud computing, big data, and other technologies, global bandwidth demand has exploded. With the widespread use of wavelength division multiplexing (WDM), polarization multiplexing, coherent reception, and multidimensional multi-order modulation (MMCM), the transmission capacity of single-mode fiber is rapidly approaching its Shannon limit. Seeking new high-speed, high-capacity optical transmission mechanisms has become a major challenge for future optical communication networks. Spatial division multiplexing technology based on mode multiplexing and multi-core fiber (MCF) is expected to be one of the most effective methods to overcome the capacity limitations of single-mode fiber communication.

[0003] Due to the differences in scale and structure between multi-core and single-mode fibers, fan-in-fan-out (FIFO) devices are needed in practical applications of multi-core fibers to achieve coupling between a single multi-core fiber and multiple single-mode fibers. This coupling between multi-core and single-core fibers can be achieved by connecting the input end of a three-dimensional optical waveguide chip to the fiber array and the output end to the multi-core fiber connector.

[0004] To achieve low-loss, high-quality coupling between multi-core and single-core optical fibers, the coupling device needs to meet the following conditions: ① insertion loss less than or equal to 2dB; ② return loss greater than or equal to 45dB; ③ polarization-dependent loss less than or equal to 0.5dB; ④ multi-core crosstalk less than or equal to -35dB. However, the three-dimensional waveguide chips in related technologies cannot fully meet these conditions. Summary of the Invention

[0005] To improve the coupling quality of single-core and multi-core fiber couplers, this application provides a three-dimensional waveguide chip and its fabrication method, as well as a single-core and multi-core fiber coupler.

[0006] The three-dimensional waveguide chip provided in this application adopts the following technical solution:

[0007] A three-dimensional waveguide chip includes several optical waveguides of equal diameter. The optical waveguides are integrated with fiber core bundles. The first end of the fiber core bundle is formed by the linear arrangement of the optical waveguides. The second end of the fiber core bundle is formed by the circumferential arrangement of the optical waveguides or by the central and circumferential arrangement. The optical waveguides extend linearly or bend from the first end to the second end.

[0008] A three-dimensional coordinate system is established with the center of the fiber core bundle at the first end as the origin, the extension direction from the first end to the second end as the x-axis, the direction of the linear arrangement of the optical waveguide as the z-axis, and the direction perpendicular to the x-axis and z-axis as the y-axis; the coordinates of any point of the optical waveguide between the first end and the second end satisfy the following formula:

[0009] x = x;

[0010]

[0011]

[0012] Where L is the distance between the first end and the second end, a is the y-value of the center of the optical waveguide at the second end, b is the difference between the z-value of the optical waveguide at the first end and the z-value at the second end, and c is the z-value of the optical waveguide at the first end.

[0013] By adopting the above technical solution, the bending curve of the optical waveguide in the three-dimensional waveguide chip is designed, so that the three-dimensional waveguide chip has low transmission loss and high transmission quality, which helps to connect multi-core optical fibers and single-core optical fibers.

[0014] Optionally, the fiber core bundle includes seven optical waveguides; the seven optical waveguides are arranged in a straight line at the first end, and the center distance between two adjacent optical waveguides is 127 micrometers; they are arranged in the center and circumferential direction at the second end, and the center distance between two adjacent optical waveguides is 41.5 micrometers; the distance between the first end and the second end is 17 millimeters.

[0015] The coordinates of the seven optical waveguides between the first end and the second end are as follows:

[0016] x = x;

[0017] y=0

[0018]

[0019] x = x;

[0020]

[0021]

[0022] x = x;

[0023]

[0024]

[0025] x = x;

[0026] y=0

[0027] z = 0

[0028] x = x;

[0029]

[0030]

[0031] x = x;

[0032]

[0033]

[0034] x = x.

[0035] y=0

[0036]

[0037] Optionally, on the side of the first end away from the second end and on the side of the second end away from the first end, all seven optical waveguides continue to extend in a straight line for a length of 1 to 2 micrometers.

[0038] Optionally, the refractive index difference of the optical waveguide is greater than 0.0020.

[0039] Optionally, the refractive index difference of the optical waveguide is 0.0023.

[0040] This application also provides a method for fabricating a three-dimensional waveguide chip, used to fabricate the three-dimensional waveguide chip described in any embodiment of this application, comprising:

[0041] S1. Construct the femtosecond laser processing system and provide the processing substrate material;

[0042] S2. A femtosecond laser processing system is used to perform femtosecond laser processing on the substrate material; the three-dimensional displacement stage of the femtosecond laser processing system moves the substrate material according to the motion path of the following formula:

[0043] x = x

[0044]

[0045]

[0046] Where L is the distance between the first end and the second end of the three-dimensional waveguide chip, a is the y-value of the center of the optical waveguide of the three-dimensional waveguide chip at the second end, b is the difference between the z-value of the optical waveguide at the first end and the z-value at the second end, and c is the z-value of the optical waveguide at the first end.

[0047] S3. Fine-tune and package the three-dimensional waveguide chip after femtosecond laser processing.

[0048] Optionally, the step of using a femtosecond laser processing system to perform femtosecond laser processing on the substrate material includes:

[0049] The processing substrate material is placed on a three-dimensional displacement stage;

[0050] The substrate material is processed using a femtosecond laser, while the three-dimensional displacement stage is moved according to a formula.

[0051] x = x

[0052]

[0053]

[0054] Optionally, the three-dimensional waveguide chip includes a fiber core bundle composed of seven optical waveguides. The seven optical waveguides are arranged in a straight line at the first end of the fiber core bundle, and the center-to-center distance between any two adjacent optical waveguides is 127 micrometers. The seven optical waveguides are arranged in a center-to-circumferential direction at the second end of the fiber core bundle, and the center-to-center distance between any two adjacent optical waveguides is 41.5 micrometers. The distance between the first end and the second end is 17 millimeters. The specific steps of moving the three-dimensional displacement stage according to the formula include the following:

[0055] x = x

[0056]

[0057]

[0058] The formula is the motion path, which moves the three-dimensional displacement stage:

[0059] x = x;

[0060] y=0

[0061]

[0062] x = x;

[0063]

[0064]

[0065] x = x;

[0066]

[0067]

[0068]

[0069]

[0070]

[0071] Optionally, the step of fine-tuning and packaging the three-dimensional waveguide chip after femtosecond laser processing includes:

[0072] The end face of the three-dimensional waveguide chip is polished and cleaned;

[0073] The three-dimensional waveguide chip is packaged and solidified.

[0074] This application also provides a single-core / multi-core fiber coupler, including a housing and a three-dimensional waveguide chip as described in any embodiment of this application, wherein the three-dimensional waveguide chip is disposed within the housing.

[0075] In summary, this application includes the following beneficial technical effects:

[0076] By designing the bending curve of the optical waveguide within the three-dimensional waveguide chip, lower insertion loss, lower return loss, lower polarization-dependent loss, and lower inter-core crosstalk are achieved, meeting the high-quality requirements of single-core and multi-core fiber couplers for three-dimensional waveguide chips. This helps improve the coupling quality of single-core and multi-core fiber couplers, thereby improving the connection quality between multi-core and single-core fibers. Attached Figure Description

[0077] Figure 1 This is a three-dimensional coordinate diagram of the three-dimensional waveguide chip in Embodiment 1 of this application.

[0078] Figure 2 This is a schematic diagram of the first end of the three-dimensional waveguide chip in Embodiment 1 of this application.

[0079] Figure 3 This is a schematic diagram of the second end of the three-dimensional waveguide chip in Embodiment 1 of this application.

[0080] Figure 4 This is a distribution diagram of the Gaussian light spot in a three-dimensional waveguide chip at different transmission distances in Embodiment 1 of this application.

[0081] Figure 5 Figure (a) shows the relationship between the effective refractive index difference and the waveguide transmission efficiency.

[0082] Figure 5 Figure (b) shows the relationship between transmission length and waveguide transmission efficiency.

[0083] Figure 6 Figure (a) shows the relationship between waveguide insertion loss and the number of scans.

[0084] Figure 6 Figure (b) shows the relationship between waveguide insertion loss and writing power.

[0085] Figure 7 These are the single-strand loss and packaging loss of the three-dimensional waveguide chip in Embodiment 1 of this application.

[0086] Figure 8 These are the return loss and polarization-dependent loss of the three-dimensional waveguide chip in Embodiment 1 of this application.

[0087] Figure 9 This is a crosstalk matrix diagram of the three-dimensional waveguide chip in Embodiment 1 of this application.

[0088] Explanation of reference numerals in the attached figures:

[0089] 1. First optical waveguide; 2. Second optical waveguide; 3. Third optical waveguide; 4. Fourth optical waveguide; 5. Fifth optical waveguide; 6. Sixth optical waveguide; 7. Seventh optical waveguide. Detailed Implementation

[0090] The following is in conjunction with the appendix Figure 1-9 This application will be described in further detail.

[0091] It should be noted that the first end and the second end mentioned in this application are the starting end and the ending end of the optical waveguide bending extension within the optical fiber bundle, respectively.

[0092] This application discloses a three-dimensional waveguide chip for single-core and multi-core fiber couplers. The three-dimensional waveguide chip includes several optical waveguides of equal diameter. The optical waveguides integrate fiber core bundles. The first end of the fiber core bundle is composed of optical waveguides arranged linearly. The second end of the fiber core bundle is composed of optical waveguides arranged circumferentially or arranged in the center and circumferentially. The optical waveguides extend linearly or bend from the first end to the second end.

[0093] A three-dimensional coordinate system is established with the center of the fiber core bundle at the first end as the origin, the extension direction from the first end to the second end as the x-axis, the direction of the linear arrangement of the optical waveguide as the z-axis, and the direction perpendicular to the x-axis and z-axis as the y-axis. The coordinates of any point on the optical waveguide between the first end and the second end satisfy the following formula:

[0094] x = x

[0095]

[0096]

[0097] Where L is the distance between the first end and the second end, a is the y-value of the center of the optical waveguide at the second end, b is the difference between the z-value of the optical waveguide at the first end and the z-value at the second end, and c is the z-value of the optical waveguide at the first end.

[0098] By making the above-mentioned settings on the three-dimensional waveguide chip, the bending section of the three-dimensional waveguide chip is optimized, so that the three-dimensional waveguide chip has lower transmission loss and higher transmission quality, thereby improving the coupling quality of single-core and multi-core fiber couplers.

[0099] Example 1

[0100] Reference Figure 1-3 The three-dimensional waveguide chip provided in this embodiment includes seven optical waveguides, namely, a first optical waveguide 1, a second optical waveguide 2, a third optical waveguide 3, a fourth optical waveguide 4, a fifth optical waveguide 5, a sixth optical waveguide 6, and a seventh optical waveguide 7. The first optical waveguide 1, the second optical waveguide 2, the third optical waveguide 3, the fourth optical waveguide 4, the fifth optical waveguide 5, the sixth optical waveguide 6, and the seventh optical waveguide 7 are arranged linearly at equal intervals at the first end. The fourth optical waveguide 4 extends in a straight line from the first end to the second end. The first optical waveguide 1, the second optical waveguide 2, the third optical waveguide 3, the fifth optical waveguide 5, the sixth optical waveguide 6, and the seventh optical waveguide 7 extend in curves from the first end to the second end. Furthermore, the first optical waveguide 1 and the seventh optical waveguide 7 are symmetrical about the x-axis, the second optical waveguide 2 and the sixth optical waveguide 6 are symmetrical about the x-axis, and the third optical waveguide 3 and the fifth optical waveguide 5 are symmetrical about the x-axis. At the second end, seven optical waveguides are arranged circumferentially with the fourth optical waveguide 4 as the center, namely the first optical waveguide 1, the second optical waveguide 2, the third optical waveguide 3, the fifth optical waveguide 5, the sixth optical waveguide 6 and the seventh optical waveguide 7, and the distance between any two adjacent optical waveguides is equal.

[0101] In one specific embodiment, the diameter of the seven optical waveguides ranges from 7 micrometers to 9 micrometers, preferably 8 micrometers. At the first end, the center-to-center distance between two adjacent optical waveguides ranges from 70 micrometers to 270 micrometers, preferably 127 micrometers; at the second end, the center-to-center distance between two adjacent optical waveguides ranges from 35 micrometers to 46 micrometers, preferably 41.5 micrometers. The length of the fourth optical waveguide 4 between the first and second ends ranges from 14 millimeters to 20 millimeters, preferably 17 millimeters; typically, in a three-dimensional waveguide chip, on the side of the first end away from the second end and on the side of the second end away from the first end, all seven optical waveguides continue to extend linearly for a length of 1 micrometer to 2 micrometers, preferably 1 micrometer. The refractive index difference of the optical waveguides is greater than 0.0020, preferably 0.0023.

[0102] At the first end, the center-to-center distance between any two adjacent optical waveguides is 127 micrometers; at the second end, the center-to-center distance between any two optical waveguides is 41.5 micrometers.

[0103] Therefore, in a three-dimensional coordinate system (unit: millimeters), at the first end,

[0104] The coordinates of the first optical waveguide 1 are: x = 0, y = 0, z = 0.381;

[0105] The coordinates of the second optical waveguide 2 are: x = 0, y = 0, z = 0.254;

[0106] The coordinates of the third optical waveguide 3 are: x = 0, y = 0, z = 0.127;

[0107] The coordinates of the fourth optical waveguide 4 are: x = 0, y = 0, z = 0;

[0108] The coordinates of the fifth optical waveguide 5 are: x = 0, y = 0, z = -0.127;

[0109] The coordinates of the sixth optical waveguide 6 are: x = 0, y = 0, z = -0.254;

[0110] The coordinates of the seventh optical waveguide 7 are: x = 0, y = 0, z = -0.381.

[0111] At the second end,

[0112] The coordinates of the first optical waveguide 1 are: x = 17, y = 0, z = 0.0415;

[0113] The coordinates of the second optical waveguide 2 are: x = 17, y = 0.03594, z = 0.02075;

[0114] The coordinates of the third optical waveguide 3 are: x = 17, y = -0.03594, z = 0.02075;

[0115] The coordinates of the fourth optical waveguide 4 are: x = 17, y = 0, z = 0.381;

[0116] The coordinates of the fifth optical waveguide 5 are: x = 17, y = 0.03594, z = -0.02075;

[0117] The coordinates of the sixth optical waveguide 6 are: x = 17, y = -0.03594, z = -0.02075;

[0118] The coordinates of the seventh optical waveguide 7 are: x = 17, y = 0, z = -0.0415.

[0119] Between the first end and the second end,

[0120] The coordinates of the first optical waveguide 1 are:

[0121] x = x;

[0122] y=0

[0123]

[0124] The coordinates of the second optical waveguide 2 are:

[0125] x = x;

[0126]

[0127]

[0128] The coordinates of the third optical waveguide 3 are:

[0129] x = x;

[0130]

[0131]

[0132] The coordinates of the fourth optical waveguide 4 are:

[0133] x = x;

[0134] y=0

[0135] z = 0

[0136] The coordinates of the fifth optical waveguide 5 are:

[0137] x = x;

[0138]

[0139]

[0140] The coordinates of the sixth optical waveguide 6 are:

[0141] x = x;

[0142]

[0143]

[0144] The coordinates of the seventh optical waveguide 7 are:

[0145] x = x

[0146] y=0

[0147]

[0148] The implementation principle of the three-dimensional waveguide chip provided in Embodiment 1 of this application is as follows: by designing the bending curve of the optical waveguide in the three-dimensional waveguide chip, the three-dimensional waveguide chip has low transmission loss and high transmission quality, thereby facilitating the connection of multi-core optical fibers and single-core optical fibers.

[0149] In other embodiments, the fiber core bundle of the three-dimensional waveguide chip can also be composed of bundles of four, eight, or nine optical waveguides; similarly, at the first end, the center distance between two adjacent optical waveguides can be 85 micrometers, 250 micrometers, etc. Likewise, the first end of the fiber core bundle is composed of multiple optical waveguides arranged linearly, and the second end is composed of multiple optical waveguides arranged circumferentially or centrally and circumferentially, and any given coordinate on each optical waveguide between the first and second ends also satisfies the above general formula. Under the inventive concept of this application, the three-dimensional waveguide chip can be designed according to actual needs, and this application does not impose any limitations.

[0150] This application also discloses a method for fabricating a three-dimensional waveguide chip.

[0151] Example 2

[0152] Reference Figure 4 and Figure 5 The fabrication method for the three-dimensional waveguide chip provided in this embodiment is used to fabricate the three-dimensional waveguide chip in Embodiment 1. The fabrication method includes the following steps:

[0153] S1. Build a femtosecond laser processing system and provide processing substrate materials.

[0154] The substrate material used in the processing is Corning Eagle XG glass, which is 20 mm long, 2.5 mm wide, and 1.1 mm high.

[0155] The femtosecond laser processing system includes a light source module, a beam control module, a motion control module, and an imaging module. The light source module emits the femtosecond laser and includes a femtosecond laser and a first reflecting mirror; the femtosecond laser has a wavelength of 1030 nm, a repetition rate of 500 kHz, and a pulse width of 400 fs. The beam control module adjusts the femtosecond laser and includes filters, cylindrical lenses, convex lenses, a second reflecting mirror, a beam splitter, a third reflecting mirror, a fourth reflecting mirror, and a slit; the slit width is 800 micrometers. The motion control module adjusts the position of the glass and includes an objective lens and a three-dimensional displacement stage; the objective lens is a 40x objective lens with an NA value of 0.75. The imaging module detects the femtosecond laser and includes a camera.

[0156] S2. A femtosecond laser processing system is used to process the substrate material using femtosecond lasers.

[0157] Specifically, the glass to be processed is placed on a three-dimensional displacement stage; a femtosecond laser is emitted from the femtosecond laser, reflected by the first reflecting mirror to a filter, which controls the power of the femtosecond laser, outputting a power of 400mW. The femtosecond laser is then shaped into an elliptical Gaussian beam by a cylindrical lens, collimated by a convex lens, and reflected by the second reflecting mirror to a beam splitter, where it is split into two beams. One beam illuminates a slit, is shaped into an elongated spot, and is then focused onto the glass through a 40x objective lens to process the glass to a depth ranging from 114.06 micrometers to 185.94 micrometers, with more than 10 scans during the process; the other beam illuminates a camera, thereby detecting and adjusting the laser light illuminating the glass.

[0158] During the machining process, the three-dimensional displacement stage moves according to the motion path of the following formula:

[0159] x = x

[0160]

[0161]

[0162] Where L represents the length of the bent section of the 3D waveguide chip, i.e., the distance between the starting end (first end) and the ending end (second end) of the bend in the optical waveguide chip; a represents the y-value of the center of the optical waveguide at the second end; b represents the difference between the z-values ​​of the optical waveguide at the first end and the second end; and c represents the z-value of the optical waveguide at the first end. It is important to note that L, the first end, the second end, and the diameter of the optical waveguide are all preset according to actual needs. Typically, the 3D waveguide chip also has straight waveguides of 1 mm to 2 mm on the side of the first end away from the second end, and on the side of the second end away from the first end.

[0163] Specifically, corresponding to the three-dimensional waveguide chip with seven fiber cores in Embodiment 1 above, the three-dimensional displacement stage is moved according to the following formula to prepare the first optical waveguide 1, the second optical waveguide 2, the third optical waveguide 3, the fourth optical waveguide 4, the fifth optical waveguide 5, the sixth optical waveguide 6 and the seventh optical waveguide 7 respectively, thereby forming the fiber core bundle of the three-dimensional waveguide chip.

[0164] The motion path corresponding to the first optical waveguide 1 is:

[0165] x = x;

[0166] y=0

[0167]

[0168] The motion path corresponding to the second optical waveguide 2 is:

[0169] x = x;

[0170]

[0171]

[0172] The motion path corresponding to the third optical waveguide 3 is:

[0173] x = x;

[0174]

[0175]

[0176] The motion path corresponding to the fourth optical waveguide 4 is:

[0177] x = x;

[0178] y=0

[0179] z = 0

[0180] The motion path corresponding to the fifth optical waveguide 5 is:

[0181] x = x;

[0182]

[0183]

[0184] The motion path corresponding to the sixth optical waveguide 6 is:

[0185] x = x;

[0186]

[0187]

[0188] The motion path corresponding to the seventh optical waveguide 7 is:

[0189] x = x

[0190] y=0

[0191]

[0192] S3. Fine-tune and package the three-dimensional waveguide chip after femtosecond laser processing.

[0193] Specifically, after femtosecond laser processing, the end faces of the three-dimensional waveguide chip are polished and cleaned to obtain a fiber core bundle with a total length of 19 mm and a bending section of 17 mm. Then, the three-dimensional waveguide chip is encapsulated and cured, including end face curing and clamping curing on both sides. Custom-sized K9 glass is used for end face curing, and NTT's AT6001 optical waveguide-specific adhesive is used for clamping curing on both sides.

[0194] Subsequently, the three-dimensional waveguide chip in Example 1, prepared through Example 2, was tested and analyzed.

[0195] Please refer to Figure 4 Using Rsoft, a three-dimensional optical waveguide was simulated, with seven emission fields simultaneously emitting Gaussian light. At x=0, the distribution of the Gaussian light spot in the three-dimensional waveguide matched the linear arrangement of the seven optical waveguides at the first end. At x=5 mm, x=10 mm, and x=15 mm, the light spot distribution gradually converged, until at x=17 mm, where the light spot exhibited a distribution of six spots arranged circumferentially around a central spot. This matched the arrangement of the seven optical waveguides at the second end. This demonstrates that the three-dimensional waveguide chip provided in this embodiment successfully achieved the transfer of the Gaussian beam position, realizing high-quality light spot transfer.

[0196] Please refer to Figure 5 When the refractive index difference of the waveguide is greater than 0.002, the transmission efficiency of the waveguide is greater than 99%. While ensuring the refractive index of the waveguide is greater than 0.002, when the length of the waveguide is greater than 17 micrometers, the transmission efficiency is greater than 98%. This demonstrates that the three-dimensional waveguide chip provided in this application embodiment has a high transmission efficiency, reaching up to 98.2%.

[0197] Please refer to Figure 6 In the waveguide fabrication process using femtosecond lasers, the insertion loss of the waveguide is low and tends to stabilize when the number of scans exceeds 10. While maintaining a scan count greater than 10, increasing the writing power of the femtosecond laser from 320mW to 480mW causes the waveguide insertion loss to first decrease and then increase, reaching a minimum of 0.65dB when the writing power is 380mW. This demonstrates that the three-dimensional waveguide chip fabricated using the method described in Example 2 exhibits low insertion loss.

[0198] Please refer to Figure 7 Loss tests were performed on the seven optical waveguides of the three-dimensional waveguide chip, and the individual losses of each waveguide were found to be around 1.5 dB. Loss tests were also performed on the seven optical waveguides of the packaged three-dimensional waveguide chip. Except for the sixth optical waveguide, which had a package loss of 2.17 dB due to packaging process errors, the package losses of the other optical waveguides were all less than 2 dB. This demonstrates that the insertion loss of the three-dimensional waveguide chip in Example 1, prepared using the method of Example 2 of this application, is less than 2 dB, meeting the insertion loss requirements for three-dimensional waveguide chips used in single-core / multi-core fiber couplers.

[0199] Please refer to Figure 8The return loss and polarization-dependent loss of the seven optical waveguides of the three-dimensional waveguide chip were measured. The return loss of all seven channels was greater than 45dB, which meets the return loss requirements of the three-dimensional waveguide chip for use in single-core and multi-core fiber couplers. The polarization-dependent loss of all seven channels was less than 0.3dB and less than 0.5dB, which also meets the polarization-dependent loss requirements of the three-dimensional waveguide chip for use in single-core and multi-core fiber couplers.

[0200] Please refer to Figure 9 The crosstalk between cores of the three-dimensional waveguide chip was detected and analyzed, and the crosstalk matrix was obtained. The largest crosstalk was -40.43dB, which is less than -35dB, thus meeting the crosstalk requirements of the three-dimensional waveguide chip for use in single- or multi-core fiber couplers.

[0201] The above test analysis shows that the three-dimensional waveguide chip provided in this embodiment has low insertion loss, low return loss, low polarization dependent loss, and low inter-core crosstalk, which meets the high-quality requirements of single-core and multi-core fiber couplers for three-dimensional waveguide chips. This helps to improve the coupling quality of single-core and multi-core fiber couplers, thereby improving the connection quality between multi-core and single-core fibers.

[0202] This application also discloses a single-core or multi-core fiber optic coupler.

[0203] Example 3

[0204] This embodiment provides a single-core / multi-core fiber coupler, including a housing and a three-dimensional waveguide chip as described in this application embodiment, wherein the three-dimensional waveguide chip is disposed inside the housing.

[0205] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A three-dimensional waveguide chip, characterized by, The application relates to a three-dimensional waveguide chip, which comprises a plurality of optical waveguides with equal diameters, the refractive index difference of the optical waveguides is greater than 0.0020, the optical waveguides form a fiber core bundle, the first end of the fiber core bundle is formed by linear arrangement of the optical waveguides, the second end of the fiber core bundle is formed by circumferential arrangement or central and circumferential arrangement of the optical waveguides, the optical waveguides linearly extend or bend from the first end to the second end, and the fiber core bundle comprises seven optical waveguides; the seven optical waveguides are linearly arranged at the first end, the central distance between two adjacent optical waveguides is 127 microns, the seven optical waveguides are centrally and circumferentially arranged at the second end, the central distance between two adjacent optical waveguides is 41.5 microns, and the distance between the first end and the second end is 17 millimeters; the seven optical waveguides linearly extend for 1-2 microns in length on the side, away from the second end, of the first end and on the side, away from the first end, of the second end; a three-dimensional coordinate system is established with the center of the fiber core bundle at the first end as the origin, the extending direction of the first end to the second end as the x-axis, the linear arrangement direction of the optical waveguides as the z-axis, and the direction perpendicular to the x-axis and the z-axis as the y-axis; and the coordinates of any point of the optical waveguides between the first end and the second end satisfy the following formula: ； ； ； ； ； ； 。 2. The three-dimensional waveguide chip of claim 1, wherein, The refractive index difference of the optical waveguides is 0.0023.

3. A method for producing a three-dimensional waveguide chip, for producing a three-dimensional waveguide chip according to any one of claims 1 to 2, characterized in that The application relates to a three-dimensional waveguide chip, which comprises a plurality of optical waveguides with equal diameters, the refractive index difference of the optical waveguides is greater than 0.0020, the optical waveguides form a fiber core bundle, the first end of the fiber core bundle is formed by linear arrangement of the optical waveguides, the second end of the fiber core bundle is formed by circumferential arrangement or central and circumferential arrangement of the optical waveguides, the optical waveguides linearly extend or bend from the first end to the second end, and the fiber core bundle comprises seven optical waveguides; the seven optical waveguides are linearly arranged at the first end, the central distance between two adjacent optical waveguides is 127 microns, the seven optical waveguides are centrally and circumferentially arranged at the second end, the central distance between two adjacent optical waveguides is 41.5 microns, and the distance between the first end and the second end is 17 millimeters; the seven optical waveguides linearly extend for 1-2 microns in length on the side, away from the second end, of the first end and on the side, away from the first end, of the second end; a three-dimensional coordinate system is established with the center of the fiber core bundle at the first end as the origin, the extending direction of the first end to the second end as the x-axis, the linear arrangement direction of the optical waveguides as the z-axis, and the direction perpendicular to the x-axis and the z-axis as the y-axis; and the coordinates of any point of the optical waveguides between the first end and the second end satisfy the following formula: The refractive index difference of the optical waveguides is 0.0023. The application relates to a three-dimensional waveguide chip, which comprises a plurality of optical waveguides with equal diameters, the refractive index difference of the optical waveguides is greater than 0.0020, the optical waveguides form a fiber core bundle, the first end of the fiber core bundle is formed by linear arrangement of the optical waveguides, the second end of the fiber core bundle is formed by circumferential arrangement or central and circumferential arrangement of the optical waveguides, the optical waveguides linearly extend or bend from the first end to the second end, and the fiber core bundle comprises seven optical waveguides; the seven optical waveguides are linearly arranged at the first end, the central distance between two adjacent optical waveguides is 127 microns, the seven optical waveguides are centrally and circumferentially arranged at the second end, the central distance between two adjacent optical waveguides is 41.5 microns, and the distance between the first end and the second end is 17 millimeters; the seven optical waveguides linearly extend for 1-2 microns in length on the side, away from the second end, of the first end and on the side, away from the first end, of the second end; a three-dimensional coordinate system is established with the center of the fiber core bundle at the first end as the origin, the extending direction of the first end to the second end as the x-axis, the linear arrangement direction of the optical waveguides as the z-axis, and the direction perpendicular to the x-axis and the z-axis as the y-axis; and the coordinates of any point of the optical waveguides between the first end and the second end satisfy the following formula: The refractive index difference of the optical waveguides is 0.0023.

4. The method of claim 3, wherein the method further comprises: The application relates to a three-dimensional waveguide chip, which comprises a plurality of optical waveguides with equal diameters, the refractive index difference of the optical waveguides is greater than 0.0020, the optical waveguides form a fiber core bundle, the first end of the fiber core bundle is formed by linear arrangement of the optical waveguides, the second end of the fiber core bundle is formed by circumferential arrangement or central and circumferential arrangement of the optical waveguides, the optical waveguides linearly extend or bend from the first end to the second end, and the fiber core bundle comprises seven optical waveguides; the seven optical waveguides are linearly arranged at the first end, the central distance between two adjacent optical waveguides is 127 microns, the seven optical waveguides are centrally and circumferentially arranged at the second end, the central distance between two adjacent optical waveguides is 41.5 microns, and the distance between the first end and the second end is 17 millimeters; the seven optical waveguides linearly extend for 1-2 microns in length on the side, away from the second end, of the first end and on the side, away from the first end, of the second end; a three-dimensional coordinate system is established with the center of the fiber core bundle at the first end as the origin, the extending direction of the first end to the second end as the x-axis, the linear arrangement direction of the optical waveguides as the z-axis, and the direction perpendicular to the x-axis and the z-axis as the y-axis; and the coordinates of any point of the optical waveguides between the first end and the second end satisfy the following formula: The refractive index difference of the optical waveguides is 0.0023. The application relates to a three-dimensional waveguide chip, which comprises a plurality of optical waveguides with equal diameters, the refractive index difference of the optical waveguides is greater than 0.0020, the optical waveguides form a fiber core bundle, the first end of the fiber core bundle is formed by linear arrangement of the optical waveguides, the second end of the fiber core bundle is formed by circumferential arrangement or central and circumferential arrangement of the optical waveguides, the optical waveguides linearly extend or bend from the first end to the second end, and the fiber core bundle comprises seven optical waveguides; the seven optical waveguides are linearly arranged at the first end, the central distance between two adjacent optical waveguides is 127 microns, the seven optical waveguides are centrally and circumferentially arranged at the second end, the central distance between two adjacent optical waveguides is 41.5 microns, and the distance between the first end and the second end is 17 millimeters; the seven optical waveguides linearly extend for 1-2 microns in length on the side, away from the second end, of the first end and on the side, away from the first end, of the second end; a three-dimensional coordinate system is established with the center of the fiber core bundle at the first end as the origin, the extending direction of the first end to the second end as the x-axis, the linear arrangement direction of the optical waveguides as the z-axis, and the direction perpendicular to the x-axis and the z-axis as the y-axis; and the coordinates of any point of the optical waveguides between the first end and the second end satisfy the following formula:

5. The method of claim 4, wherein the method further comprises: The refractive index difference of the optical waveguides is 0.0023. ； ； ； ； ； ； 。 6. The method of claim 3, wherein the method further comprises: ​ ​ ​ 7. A single multi-core fiber coupler, characterized by, ​

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