2.5 D optical waveguide chip and preparation method and application device thereof

Abstract

The invention relates to a 2.5 D optical waveguide chip and a preparation method and an application device thereof, and belongs to the technical field of integrated photoelectron and optical fiber communication. Aiming at the technical problems that an existing 3D optical waveguide based on a laser direct writing process cannot be manufactured at a wafer level, the production efficiency is low and the cost is high, the invention provides a 2.5 D optical waveguide chip which comprises a substrate and at least two layers of planar optical waveguides which are isolated by a cladding material and each layer is limited to extend in a plane of the planar optical waveguide; the waveguide distribution of the light inlet end face of the chip is matched with the fiber core distribution of the target multi-core optical fiber for coupling alignment, the waveguides of the light outlet end face of the chip are distributed in a step shape, and the waveguides located on different layers have different heights so as to be coupled and aligned with the corresponding optical fiber array distributed in the step shape. The chip is suitable for wafer-level batch manufacturing and is mainly used for forming core optical devices such as a multi-core optical fiber fan-in and fan-out assembly, a multi-core optical fiber optical receiver and a multi-core optical fiber optical transmitter.

Description

Technical Field

[0001] This invention relates to the field of integrated optoelectronics and fiber optic communication technology. More specifically, this invention relates to a 2.5D optical waveguide chip, its fabrication method, and application devices. Background Technology

[0002] With the continuous growth of artificial intelligence technology and the demand for high-performance computing, the scale and interconnection density of data centers have significantly increased, placing higher demands on the transmission capacity and integration of fiber optic cabling systems. In existing technologies, traditional fiber optic cabling solutions generally use single-core optical fibers for device interconnection, leading to problems such as a surge in patch cord counts, complex cabling structures, large physical space occupation, maintenance difficulties, and reduced signal reliability in high-density environments. Particularly in application scenarios oriented towards large-scale AI model training and cross-regional computing power scheduling, high-core-count backbone optical cables need to be deployed within data centers and across campuses, further exacerbating the pressure on existing cabling systems in terms of scalability and management efficiency.

[0003] To address these challenges, multi-core fiber (MCF) has been proposed as a solution to improve space utilization. This type of fiber integrates multiple independent cores within a single cladding, achieving several times the transmission capacity of a single-core fiber with the same wire diameter. This helps simplify cabling structures and reduce conduit occupancy and construction costs. For example, deploying four-core or seven-core MCF in artificial intelligence clusters can significantly improve the resource utilization of existing infrastructure. Furthermore, pre-connected backbone cables based on MCF can help shorten deployment cycles and support the high-speed interconnection needs between data centers.

[0004] However, the introduction of multi-core optical fibers also requires that the accompanying optical modules possess corresponding multi-core optical fiber interface capabilities. Currently, the mainstream technology for realizing this type of interface relies on three-dimensional optical waveguide structures based on laser direct-writing technology. Although this technology can achieve three-dimensional optical path coupling between multi-core optical fibers and optical devices, its manufacturing process has the following significant drawbacks: First, this process relies on monolithic laser direct writing, which cannot achieve wafer-level mass production, resulting in low production efficiency and high manufacturing costs, making it difficult to meet the needs of large-scale deployment. Second, this technology has extremely high requirements for processing precision, and process fluctuations can easily lead to increased coupling loss, affecting the consistency of component performance. In addition, since each waveguide needs to be processed individually, the manufacturing cycle is long and the production capacity is limited, making it difficult to meet the urgent needs of rapidly developing data centers for high-density optical modules.

[0005] Therefore, existing three-dimensional optical waveguide solutions based on laser direct writing technology have significant bottlenecks in terms of manufacturing cost, production efficiency, and scalability, which restricts the widespread application of multi-core optical fiber technology in data centers. Summary of the Invention

[0006] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0007] One objective of this invention is to address the technical problems in existing technologies, such as the complexity and large space occupation of high-density fiber optic cabling in data centers, and the inability to manufacture multi-core fiber optic interfaces at the wafer level due to laser direct-writing processes, resulting in high production costs and low efficiency. Another objective of this invention is to provide a 2.5D optical waveguide chip and its application devices that possess wafer-level manufacturing capabilities, low cost, and a compact structure.

[0008] To achieve these objectives and other advantages according to the present invention, a 2.5D optical waveguide chip is provided, which is essentially a multilayer planar optical waveguide. Unlike traditional 2D optical waveguides structured in a single plane, and 3D optical waveguides that can be freely structured in three-dimensional space, the waveguides in this invention cannot be freely structured in three-dimensional space; each waveguide is confined to its own layer for routing. This type of multilayer planar optical waveguide, which allows for free routing within its respective layer but is isolated between layers by cladding material, is defined as a 2.5D optical waveguide.

[0009] This invention provides a 2.5D optical waveguide chip, comprising: Substrate; At least two planar optical waveguides are stacked sequentially on the substrate, wherein each optical waveguide is confined to its own plane and the optical waveguides of different layers are isolated by cladding material. The light-inlet end face of the chip is located on the first side of the chip. The waveguide distribution on the light-inlet end face of the chip matches the core distribution of the target multi-core optical fiber, and is used for coupling and alignment with the target multi-core optical fiber. The light-emitting end face of the chip is located on the second side of the chip opposite to the first side. The waveguides on the light-emitting end face of the chip are distributed in a stepped manner, wherein the waveguides located in different layers have different heights at the light-emitting end face of the chip, which are used for coupling and alignment with the fiber array with the corresponding stepped distribution.

[0010] Preferably, the waveguides on the light-inlet end face of the chip are arranged in a square or star shape to match four-core or seven-core multi-fiber optical fibers, respectively.

[0011] Preferably, the waveguides on the light-emitting end face of the chip are arranged in a two-step or three-step pattern to be coupled and aligned with a double V-groove fiber array having a corresponding two-step or three-step pattern, respectively.

[0012] This invention provides a multi-core fiber fan-in / fan-out assembly, comprising: The aforementioned 2.5D optical waveguide chip; A multi-core fiber capillary assembly, the end face of which is coupled, aligned and fixed with the light-inlet end face of the chip; The fiber array has its end face cores arranged in a stepped pattern and coupled, aligned, and fixed to the light-emitting end face of the chip.

[0013] Preferably, the fiber optic array comprises: The base plate has stepped V-grooves on it; The cover plate mates with the base plate and is provided with stepped V-grooves. Multiple uncoated single-mode optical fibers are snapped and fixed between the V-groove of the base plate and the cover plate; Fiber optic protective adhesive is applied to the root of the stripped fiber for fixation.

[0014] A multi-core fiber optic receiver is provided, comprising: The 2.5D optical waveguide chip has its light-inlet end face polished to a first angle and its light-outlet end face polished to a second angle to form a total reflection surface. A multi-core fiber capillary assembly is coupled and fixed to the light-inlet end face of the chip; A lens assembly is mounted downstream of the light-emitting end face of the chip to converge the light signal that is redirected from the total reflection surface. A photodetector chip is disposed on the light-emitting side of the lens assembly, and is used to receive the light signal focused by the lens assembly and convert it into an electrical signal; A packaging substrate is used to carry and fix the photodetector chip and the 2.5D optical waveguide chip.

[0015] Preferably, the lens assembly is a plano-convex lens array with a stepped distribution of different radii of curvature, and the radii of curvature are configured to converge light from waveguides of different heights to the same photosensitive plane of the photodetector chip.

[0016] A multi-core fiber optic transmitter is provided, comprising: The 2.5D optical waveguide chip has a multi-layered stepped distribution on the light-inlet end face and a multi-group distribution on the light-outlet end face. Multiple laser components are coupled to the light-inlet surface of the chip via coupling lenses; An isolator array is disposed between the laser assembly and the chip; A multi-core fiber array assembly is coupled and fixed to the light-emitting end face of the chip; A thermoelectric controller, located below the laser assembly, is used to control the temperature of the laser assembly; The packaging substrate is used to carry the 2.5D optical waveguide chip, laser assembly, isolator array and thermoelectric controller.

[0017] Preferably, the laser assembly and its optical path pad have multiple thicknesses that match the step distribution of the light-inlet end face of the chip, so as to match the waveguide heights of different layers at the light-inlet end face of the chip respectively.

[0018] A method for fabricating a 2.5D optical waveguide chip is provided, comprising the following steps: S1. Clean the substrate; S2. Deposit a first waveguide material layer on the substrate and control its thickness error to be within ±0.2μm; S3. Perform photolithography and etching on the first waveguide material layer to form the first planar optical waveguide; S4. Deposit a first cladding material layer on the first planar optical waveguide and control its thickness error to be within ±0.2μm; S5. Deposit a second waveguide material layer on the first cladding material layer, and control its thickness error to be within ±0.2μm; S6. Perform photolithography and etching on the second waveguide material layer to form a second planar optical waveguide; S7. Deposit a second cladding material layer on the second planar optical waveguide and control its thickness error to be within ±0.2μm; Repeat steps S5 to S7 to sequentially prepare the third and above planar optical waveguides and their corresponding cladding material layers until all preset number of optical waveguide layers are prepared. S8. Slice the wafer after all layers have been prepared to obtain a single 2.5D optical waveguide chip; S9. Polish the light-inlet and light-outlet surfaces of the 2.5D optical waveguide chip.

[0019] The present invention has at least the following beneficial effects: First, this invention proposes an innovative 2.5D optical waveguide chip architecture, which employs a multi-layer planar optical waveguide design. Each waveguide layer is confined to its own plane, and interlayer isolation is achieved through cladding materials. This architecture maintains the flexibility of optical path layout while laying the foundation for wafer-level ultra-large-scale manufacturing.

[0020] Secondly, this invention applies the 2.5D optical waveguide chip to the field of multi-core fiber (MCF) communication. Based on this chip, three core devices were invented: a multi-core fiber fan-in fan-out (FIFO) fiber assembly, a multi-core fiber optical receiver, and a multi-core fiber optical transmitter. This provides a complete optical interface solution for the large-scale application of multi-core fiber in scenarios such as data centers.

[0021] Third, the 2.5D optical waveguide chip described in this invention adopts standard semiconductor manufacturing process, has wafer-level production capability, and can achieve wafer-level production followed by slicing. Compared with the existing 3D optical waveguide solutions based on laser direct writing technology, it significantly reduces manufacturing costs and production time.

[0022] Fourth, the multi-core fiber optic transmitter and receiver based on the 2.5D optical waveguide chip have a simple structure, and their packaging process is compatible with the existing AI optical module manufacturing process. They have strong manufacturability and can quickly realize the large-scale production and deployment of multi-core fiber optic modules.

[0023] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the four-channel 2.5D optical waveguide chip structure of the present invention; Figure 2 This is a schematic diagram of the seven-channel 2.5D optical waveguide chip structure of the present invention; Figure 3 This is a schematic diagram of the four-channel double V-groove two-step distributed fiber array structure of the present invention; Figure 4 This is a schematic diagram of the seven-channel double V-groove three-step distributed fiber array structure of the present invention; Figure 5 This is a schematic diagram of the structure of the four-core fiber fan-in and fan-out fiber assembly based on a four-channel 2.5D optical waveguide chip of the present invention. Figure 6 This is a schematic diagram of the structure of the seven-core fiber fan-in and fan-out fiber assembly based on a seven-channel 2.5D optical waveguide chip of the present invention. Figure 7 This is a schematic diagram of the two-tiered distribution four-channel photodetector chip structure of the present invention. Figure 8 This is a schematic diagram of the two-step distributed four-channel plano-convex lens array structure of the present invention; Figure 9 This is a schematic diagram of the single four-core multi-core optical fiber receiver structure based on a four-channel 2.5D optical waveguide chip of the present invention. Figure 10 This is a schematic diagram of the eight-channel 2.5D optical waveguide chip structure for an optical transmitter according to the present invention; Figure 11 This is a schematic diagram of the dual four-core multi-core fiber optic transmitter structure based on an eight-channel 2.5D optical waveguide chip of the present invention. Figure 12This is a flowchart illustrating the fabrication process of the 2.5D optical waveguide chip of the present invention; wherein 1201 is a wafer substrate, 1202 is a first waveguide material layer, 1203 is a first planar optical waveguide layer, 1204 is a first cladding material layer, 1205 is a second waveguide material layer, 1206 is a second planar optical waveguide layer, 1207 is a second cladding material layer, and 1208 is a single 2.5D optical waveguide chip. Detailed Implementation

[0025] The core concept of this invention lies in providing an innovative 2.5D optical waveguide chip architecture. This architecture integrates multiple planar optical waveguides stacked vertically, with cladding material introduced between each waveguide layer to achieve optical isolation. This maintains the degree of freedom in the wiring within each waveguide plane while enabling optical path reconstruction and integration in three-dimensional space. On one hand, this architecture achieves low-loss end-face coupling at the chip's input end face through a high degree of matching between the waveguide distribution and the core distribution of the target multi-core optical fiber. On the other hand, at the chip's output end face, the stepped distribution design of the waveguides solves the alignment problem with conventional fiber arrays in the vertical direction. Furthermore, this invention applies the 2.5D optical waveguide chip to core optical devices such as multi-core fiber fan-in / fan-out components, optical receivers, and optical transmitters. Combined with corresponding optical and packaging structures, a complete multi-core fiber interface solution suitable for wafer-level manufacturing is constructed, effectively overcoming the technical bottlenecks of high manufacturing costs, low production efficiency, and difficulty in large-scale application caused by laser direct-writing processes in existing three-dimensional optical waveguides.

[0026] The present invention will now be described in further detail with reference to examples, so that those skilled in the art can implement it based on the description.

[0027] It should be noted that, unless otherwise specified, the experimental methods described in the following implementation plan are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified.

[0028] Example 1 like Figure 1 As shown, this embodiment is a four-core / multi-core fiber fan-in / fan-out assembly. The four-channel 2.5D optical waveguide chip 1 involved includes a chip input end face 101, a chip output end face 102, and a chip waveguide surface 103. The four waveguides on the chip input end face 101 are arranged in a square pattern with a channel spacing of 40μm and a tolerance of ±0.3μm. The center of the square coincides with the center of the cross-section of the four-core / multi-core fiber, with the error controlled within ±0.2μm. The mode field diameter of the waveguide is 8μm × 7μm. This embodiment uses Corning's four-core / multi-core fiber, which has a mode field diameter of 9μm, a numerical aperture of 0.12, and an optical loss of 0.3dB / km at a wavelength of 1310nm.

[0029] The four waveguides on the light-emitting end face 102 of the chip are arranged in a two-tiered configuration, with channels CH1 and CH2 located in the second layer and channels CH3 and CH4 located in the first layer. The horizontal spacing between the four waveguides is 750 μm, the interlayer distance in the tiered direction is 40 μm, and the positional error is ±0.3 μm.

[0030] like Figure 3 As shown, the four-channel dual V-groove two-step distribution fiber array 3 used in this embodiment includes a four-channel base plate stepped V-groove 301, a four-channel cover plate stepped V-groove 302, and four uncoated ordinary single-mode fibers 303. The single-mode fibers are secured between the V-groos of the base plate and the cover plate, and fiber array protective adhesive 304 is coated at the fiber stripping root. The four fiber cores on the end face of this fiber array are arranged in a two-step distribution with a positional accuracy of ±0.5μm, and their core position coordinates are... Figure 1 The waveguide position coordinates of the light-emitting end face 102 of the chip are matched to achieve coupling alignment between the two. In this embodiment, the ordinary single-mode fiber is selected as the bending-resistant G657.B3 fiber, the horizontal spacing of the V-groove is 750μm, the V-groove depth processing error is ±0.3μm, and the angle processing error is ±1°.

[0031] like Figure 5 As shown, the four-core multi-core fiber fan-in and fan-out assembly 5 in this embodiment is constructed by coupling and aligning the four-core multi-core fiber capillary assembly 501 with the chip's light-in end face 101 and bonding it together, and coupling and aligning the four-channel dual V-groove second-order distributed fiber array 3 with the chip's light-out end face 102 and bonding it together, thereby realizing the fan-in and fan-out function of four-core multi-core fiber to four ordinary single-mode fibers. In this embodiment, the coupling loss between the optical waveguide and the fiber is 0.5dB / end, and the total loss of the entire fan-in and fan-out assembly is controlled within 1.5dB (including waveguide loss, process displacement loss, and coupling loss). The coupling adhesive is a UV thermal dual-curing adhesive with a refractive index of 1.45@1310nm and a transmittance of 98.5%. Its shear strength per unit area after curing meets the US military standard 883E, and the optical path does not require additional reinforcing adhesive.

[0032] In this embodiment, the two end faces of the four-channel 2.5D optical waveguide chip are polished at 0 degrees, and the return loss meets the system requirements. In practical engineering applications, polishing at 8 degrees or other angles can also be used to further optimize the return loss performance.

[0033] Example 2 like Figure 2As shown, this embodiment is a seven-core multi-core fiber fan-in / fan-out assembly. The seven-channel 2.5D optical waveguide chip 2 involved includes a seven-core chip input end face 201, a seven-core chip output end face 202, and a seven-core chip waveguide surface 203. The seven waveguides on the chip input end face 201 are arranged in a star shape, with channel spacing matching the mainstream seven-core multi-core fiber (such as the G.651 standard). The seven waveguides on the chip output end face 202 are arranged in a three-tiered distribution, with channels CH1 and CH2 located in the third layer, channels CH3, CH4, and CH5 located in the second layer, and channels CH6 and CH7 located in the first layer. The horizontal spacing of the seven waveguides is 250 μm, the interlayer distance in the tiered direction is 40 μm, and the positional error is ±0.3 μm.

[0034] like Figure 4 As shown, the seven-channel dual V-groove three-step distribution fiber array 4 used in this embodiment includes a seven-channel base plate stepped V-groove 401, a seven-channel cover plate stepped V-groove 402, and seven uncoated ordinary single-mode fibers 303. The single-mode fibers are secured between the V-groos of the base plate and the cover plate, and fiber array protective adhesive 304 is coated at the fiber stripping root. The seven fiber cores on the end face of this fiber array are distributed in a three-step manner, with a positional accuracy of ±0.5μm, and their core position coordinates are... Figure 2 The waveguide position coordinates of the light-emitting end face 202 of the chip are matched to achieve coupling alignment between the two.

[0035] like Figure 6 As shown, the seven-core multi-core fiber fan-in and fan-out assembly 6 in this embodiment is constructed by coupling and aligning the seven-core multi-core fiber capillary assembly 601 with the chip's light-in end face 201 and bonding it together, and coupling and aligning the seven-channel dual-V-groove three-step distribution fiber array 4 with the chip's light-out end face 202 and bonding it together, thereby realizing the fan-in and fan-out function of the seven-core multi-core fiber to seven ordinary single-mode fibers. In this embodiment, the coupling loss between the optical waveguide and the optical fiber, the coupling glue specifications, and performance indicators are similar to those in Embodiment 1.

[0036] Example 3 like Figure 9 As shown, this embodiment provides a multi-core fiber optic receiver based on a four-channel 2.5D optical waveguide chip. First, the light-inlet surface 101 and the light-outlet surface 102 of the four-core 2.5D optical waveguide chip 1 are polished. Specifically, the light-inlet surface 101 is polished at an 8-degree angle, and the light-outlet surface 102 is polished at a 45-degree angle to form a total reflection surface, resulting in a four-channel 2.5D optical waveguide chip 906 with polished ends.

[0037] A four-core multi-core fiber capillary assembly 905, with its end face polished to an 8-degree angle, is coupled and bonded to the light-inlet end face 101 of the chip. A four-channel plano-convex lens array 8 with a two-tiered distribution is attached to the light-emitting surface below the 45-degree reflective surface of the light-emitting end face 102 of the chip using transparent adhesive, ensuring that the vertical projection of the center of the four-channel plano-convex lens array is aligned with the center of the waveguide. In this embodiment, the four-channel plano-convex lens array 8 is a plano-convex lens made of silicon, with anti-reflection coatings on both sides. Specifically, the planar side of the lens is coated with an adhesive AR film (adhesive refractive index n=1.5), and the convex side is coated with an air AR film (adhesive refractive index n=1.0). The convex surface curvature radius of channels CH1 and CH2 is 0.4 mm, and the convex surface curvature radius of channels CH3 and CH4 is 0.5 mm. The reason for configuring the lens curvature radius in this way is that, at the light-emitting end face, the waveguide light points of channels CH1 and CH2 are closer to the lens surface, so a surface with a smaller curvature radius is used for convergence; the waveguide light points of channels CH3 and CH4 are farther from the lens surface, so a surface with a larger curvature radius is used for convergence. This design allows light rays from waveguides of different heights to converge to the same height plane, i.e., the upper surface of the photodetector chip.

[0038] In the four-channel photodetector chip 7 with a two-tiered distribution, the high-frequency pad lines of channels CH1 and CH2 are approximately 40 μm longer than those of CH3 and CH4. The different curvature radii of the lenses are configured to compensate for the distance difference between the light-emitting points of different wave layers and the lens surface, so that the light emitted from the four channels converges to the same height plane, i.e., the upper surface of the photodetector chip 7.

[0039] The receiver COB packaging substrate 901 and the 2.5D optical waveguide chip optical path pad 902 are used to mount and support the optical path. All components are mounted on the packaging substrate 901 using silver paste. The four-channel 2.5D optical waveguide chip 906, polished at both ends, is fixed to the optical path pad 902 with UV adhesive after the optical path is coupled to the optimal state. In this embodiment, the receiver COB packaging substrate 901 is made of Panasonic M6 resin, and the optical path pad 902 is made of double-sided coarsely polished aluminum nitride. The thermal conductivity of the silver paste used is 3 W / (m·K), and the paste layer thickness is 50 μm. The responsivity of the photodetector chip 7 is 0.7 A / W.

[0040] The working principle of this four-core / multi-core fiber optic receiver is as follows: The incident signal light enters the four-channel 2.5D optical waveguide chip 906, which is polished at both ends, from the four-core / multi-core fiber capillary assembly 905. After being reflected by a 45-degree reflective surface, it enters vertically downwards into the four-channel plano-convex lens array 8. The lenses converge the optical signal and focus it onto the four-channel photodetector chip 7. The photodetector chip converts the optical signal into an electrical signal, which is then input to the transimpedance amplifier (TIA) chip 903 through the bonding wire 904 for signal amplification. The amplified electrical signal is then output to the system.

[0041] Example 4 This embodiment provides a dual-quad-core multi-core fiber optic transmitter based on an eight-channel 2.5D optical waveguide chip. For example... Figure 10 As shown, the eight-channel 2.5D optical waveguide chip 10 for an optical transmitter includes an eight-core chip output end face 1001, an eight-core chip input end face 1002, and an eight-core chip waveguide surface 1003. The eight waveguides of the eight-core chip output end face 1001 are arranged in two sets of squares, with the center of each square coinciding with the fiber core, and a side length of 40 ± 0.5 μm. The eight-core chip input end face 1002 has a two-step arrangement for coupling with the laser; the horizontal spacing between the steps is 0.8 mm, and the spacing between the two waveguide layers is 40 μm.

[0042] like Figure 11 As shown, the transmitter COB packaging substrate 1101 is made of tungsten-copper alloy with a sandblasted matte nickel plating finish. The thermoelectric controller TEC 1102 has a maximum drive current of 1A, the thermistor 1103 has a resistance of 10kΩ, and the control system maintains the temperature of the laser COC component 1105 at 55±3℃. The eight-channel isolator array 1106 has a light-transmitting aperture of 0.5mm, an isolation of 25dB, and an optical insertion loss of 0.3dB. The coupling efficiency of the eight independent coupling lenses 1104 is greater than 75%.

[0043] The packaging process for this dual quad-core multi-core fiber optic transmitter includes the following steps: 1. Silver Paste Mounting: The eight-channel 2.5D optical waveguide chip 10, the eight-channel isolator array 1106, and the thermoelectric controller TEC 1102 are mounted onto the transmitter COB package substrate 1101 using silver paste and then baked and cured. Eight independent single-lens optical path pads 1108, laser COC components 1105, and thermistors 1103 are mounted onto the thermoelectric controller TEC 1102 using silver paste and then baked and cured. The thermal conductivity of the silver paste is 3 W / (m·K), and the paste thickness is 50 μm. The mounting distance between the eight laser COCs is 0.8 mm, and the mounting accuracy is ±10 μm. The mounting accuracy requirement for the eight-channel 2.5D optical waveguide chip 10 is ±10 μm, and the mounting accuracy for the eight-channel isolator array 1106 and the thermoelectric controller 1102 is ±50 μm.

[0044] 2. Gold Wire Bonding: Gold wire bonding is performed on the laser COC component 1105, thermistor 1103, and thermoelectric controller TEC 1102 to achieve electrical connection. Three gold wires are bonded from the pads of the thermoelectric controller TEC 1102 to the circuit board, with a current carrying capacity of 600mA. The length of the gold wire from the laser COC component 1105 to the circuit board is less than 300μm to ensure high-frequency performance.

[0045] 3. Coupling Lens: Activate the thermoelectric controller TEC 1102 to maintain the laser COC assembly 1105 at 55±3℃. Apply an 80mA current to a single laser channel. Use a photodetector chip with a photosensitive surface diameter of 100μm to receive light at the emitting end face 1001 of the eight-core chip and detect the photocurrent. Adjust the position of the coupling lens 1104 to maximize the photocurrent, then pre-cure the lens with UV adhesive and heat-cure it. The measured lens coupling efficiency is 77%. Complete the coupling and bonding of all eight channel lenses sequentially.

[0046] 4. Couple the multi-core fiber optic array: Activate the thermoelectric controller TEC 1102 to maintain the temperature of the laser COC assembly 1105. Apply current to all laser channels. Couple and align the dual four-core multi-core fiber optic array assembly 1107 with the eight-core chip output end face 1001 until the output power is at its maximum, then glue them together. The coupling adhesive has a refractive index of 1.5, a transmittance of 99%, and a measured coupling loss of 0.6 dB.

[0047] 5. Optical path temperature cycling: The coupled optical path components are placed in a temperature cycling environment from -40℃ to 85℃, with a heating and cooling rate of 10℃ / minute, to release optical path stress and improve reliability.

[0048] Since channels CH1, CH2, CH5, CH6 and channels CH3, CH4, CH7, CH8 of the eight-channel 2.5D optical waveguide chip 10 are located on two different layers within the chip, channels CH1 / 2 / 5 / 6 use thicker laser COC components 1105 and single-lens optical path pads 1108, while channels CH3 / 4 / 7 / 8 use thinner laser COC components 1105 and single-lens optical path pads 1108. This ensures that the optical paths of all eight channels are in the optimal state of coupling efficiency and coupling tolerance.

[0049] The working principle of this dual four-core multi-core fiber optic transmitter is as follows: The temperature of the laser COC component 1105 is controlled and a high-speed electrical signal is applied. After electro-optical conversion, the eight optical signals generated by the laser are converged by their respective coupling lenses 1104, pass through an eight-channel isolator array 1106, and are coupled into the light-inlet end face 1002 of the waveguide chip. After transmission through the waveguide chip, the optical signals are coupled out from the light-outlet end face 1001 to the dual four-core multi-core fiber optic array component 1107, and finally, the optical signals are output to the system end.

[0050] Example 5 This embodiment details the fabrication method of a 2.5D optical waveguide chip, combined with... Figure 12 The process shown has the following specific steps: S1. Cleaning the wafer substrate: Provide a wafer substrate 1201 and clean it to remove surface contaminants.

[0051] S2. Deposit the first waveguide material layer: Deposit the first waveguide material layer 1202 on the cleaned wafer substrate, and control its deposition thickness error to be within ±0.2μm.

[0052] S3. Forming the first planar optical waveguide: Photolithography and etching are performed on the first waveguide material layer to define and form the first planar optical waveguide 1203 pattern located within the layer.

[0053] S4. Deposit the first cladding material layer: Deposit the first cladding material layer 1204 on the first planar optical waveguide, and control its deposition thickness error to be within ±0.2μm.

[0054] S5. Deposit the second waveguide material layer: Deposit the second waveguide material layer 1205 on the first cladding material layer, and control its deposition thickness error to be within ±0.2μm.

[0055] S6. Forming the second planar optical waveguide: Photolithography and etching are performed on the second waveguide material layer to define and form the second planar optical waveguide 1206 pattern located within the layer.

[0056] S7. Deposit the second cladding material layer: Deposit the second cladding material layer 1207 on the second planar optical waveguide, and control its deposition thickness error to be within ±0.2μm.

[0057] Repeat steps S5 to S7 to sequentially prepare the third and above planar optical waveguides and their corresponding cladding material layers until all preset number of optical waveguide layers are prepared.

[0058] S8. Wafer slicing: The wafer with all layers prepared is sliced ​​to separate individual 2.5D optical waveguide chips 1208.

[0059] S9. End face polishing: Polish the light-incoming end face and the light-outcoming end face of the chip to form an end face that meets the optical performance requirements.

[0060] The above embodiments are merely specific examples of the present invention, used to explain the invention and not to limit it. Those skilled in the art, after reading this specification, can make various modifications or substitutions without departing from the principles and spirit of the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A 2.5D optical waveguide chip, characterized by, Comprising: a substrate; at least two layers of planar optical waveguides stacked on the substrate in sequence, wherein each layer of optical waveguides is confined to extend within its own plane, and the optical waveguides of different layers are isolated from each other by cladding material; a chip-in light end face located on a first side of the chip, the waveguide distribution on the chip-in light end face matching the core distribution of a target multi-core fiber for coupling alignment with the target multi-core fiber; a chip-out light end face located on a second side of the chip opposite to the first side, the waveguides on the chip-out light end face being distributed in a stepped manner, wherein the waveguides located in different layers have different heights at the chip-out light end face for coupling alignment with a fiber array having a corresponding stepped distribution.

2. A 2.5D optical waveguide chip as claimed in claim 1, characterized in that, The waveguides on the chip-in light end face are distributed in a square or star shape to match a four-core or seven-core multi-core fiber, respectively.

3. A 2.5D optical waveguide chip as claimed in claim 1, characterized in that, The waveguides on the chip-out light end face are distributed in a two-step or three-step manner to couple with a double-V-groove fiber array having a corresponding two-step or three-step distribution, respectively.

4. A multi-core fiber fan-in fan-out assembly, characterized by, Comprising: a 2.5D optical waveguide chip as claimed in any one of claims 1 to 3; a multi-core fiber capillary assembly having an end face coupled and fixed to the chip-in light end face; a fiber array having a stepped core distribution on its end face and coupled and fixed to the chip-out light end face.

5. A multi-fiber optical fiber fan-in fan-out assembly as claimed in claim 4, wherein, The fiber array comprises: a bottom plate having a stepped V-groove distribution thereon; a cover plate cooperating with the bottom plate and having a corresponding stepped V-groove distribution thereon; a plurality of stripped single-mode fibers clamped and fixed between the V-grooves of the bottom plate and the cover plate; a fiber protection glue coated on the stripped fiber roots for fixation.

6. A multi-core fiber optical receiver, characterized by, Comprising: a 2.5D optical waveguide chip as claimed in any one of claims 1 to 3, the chip-in light end face being polished at a first angle and the chip-out light end face being polished at a second angle to form a total reflection surface; a multi-core fiber capillary assembly coupled and fixed to the chip-in light end face; a lens assembly attached downstream of the light path of the chip-out light end face for converging the light signal coming from the total reflection surface; a photodetector chip disposed on the light exit side of the lens assembly for receiving the light signal converged by the lens assembly and converting it into an electrical signal; a packaging substrate for carrying and fixing the photodetector chip and the 2.5D optical waveguide chip.

7. A multi-fiber fiber optic receiver as set forth in claim 6, wherein, The lens assembly is a stepped plano-convex lens array having different radii of curvature configured to converge the light rays from waveguides of different heights to the same light sensing plane of the photodetector chip.

8. A multi-core fiber optical transmitter, characterized by, Comprising: a 2.5D optical waveguide chip as claimed in any one of claims 1 to 3, the chip-in light end face having a multi-layer stepped distribution and the chip-out light end face having a multi-group distribution; a plurality of laser assemblies coupled to the chip-in light end face through coupling lenses; an isolator array disposed between the laser assemblies and the chip; a multi-core fiber array assembly coupled and fixed to the chip-out light end face; a thermoelectric controller disposed below the laser assemblies for temperature control of the laser assemblies; a packaging substrate for carrying the 2.5D optical waveguide chip, the laser assemblies, the isolator array, and the thermoelectric controller.

9. A multi-core fiber optical transmitter as claimed in claim 8, characterized in that, The laser assembly and its optical path pad have multiple thicknesses matching the step distribution of the chip light-in end face to match the waveguide height of different layers at the chip light-in end face respectively.

10. A method of manufacturing a 2.5D optical waveguide chip for manufacturing a 2.5D optical waveguide chip according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1, cleaning a substrate; S2, depositing a first waveguide material layer on the substrate, and controlling the thickness error of the first waveguide material layer to be within ±0.2 μm; S3, performing photolithography and etching on the first waveguide material layer to form a first layer of planar optical waveguide; S4, depositing a first cladding layer material layer on the first layer of planar optical waveguide, and controlling the thickness error of the first cladding layer material layer to be within ±0.2 μm; S5, depositing a second waveguide material layer on the first cladding layer material layer, and controlling the thickness error of the second waveguide material layer to be within ±0.2 μm; S6, performing photolithography and etching on the second waveguide material layer to form a second layer of planar optical waveguide; S7, depositing a second cladding layer material layer on the second layer of planar optical waveguide, and controlling the thickness error of the second cladding layer material layer to be within ±0.2 μm; The steps S5 to S7 are repeatedly performed to sequentially prepare a third layer and above layers of planar optical waveguide and the corresponding cladding layer material layers until the preparation of all the preset layers of optical waveguide layers is completed; S8, slicing the wafer after the preparation of all the layers to obtain a single 2.5D optical waveguide chip; S9, polishing the light-in end face and the light-out end face of the 2.5D optical waveguide chip.

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