Flexible waveguide coupling structure for high-density optical engine and miniaturized packaging method of flexible waveguide coupling structure

Abstract

According to the flexible waveguide coupling structure for the high-density optical engine and the miniaturized packaging method of the flexible waveguide coupling structure, the polymer optical waveguide is adopted, the waveguide core layer is made of the high-refractive-index material, and the refractive index of the core layer is higher than that of the upper cladding and the lower cladding, so that light beams can reflect light rays on the surface or in the core layer; the light beam is limited in the core layer to be transmitted along the set path; the flexible waveguide is used in high-density optical engine packaging, a traditional ribbon optical fiber array is directly replaced, and the contradiction between space limitation and bending radius is solved; comprising a flexible waveguide, an MT / MPO connector and a microlens array, polymers such as PMMA, BCB, SU-8, FPPE, PSQ, PDMS / M-PDMS and the like are selected as flexible waveguide materials, the thickness is smaller than or equal to 0.2 mm, the bendable radius is smaller than or equal to 2 mm, the core / cladding refractive index difference delta n is larger than or equal to 0.01, the multimode numerical aperture NA is approximately equal to 0.3, the transmission loss in a 850 nm window is smaller than or equal to 0.25 dB / cm, the angle of a coupling end face is 40-50 degrees, and the requirements for low loss and high bandwidth of short-distance parallel optical interconnection are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric communication and its using equipment, in particular to a flexible waveguide coupling structure for high-density optical engine and a miniaturized packaging method thereof. BACKGROUND

[0002] In data centers, especially in short-distance multi-channel parallel optical engines, VCSEL arrays and PIN arrays are core light sources and detectors. They realize optical signal transmission and reception through multi-mode ribbon fiber arrays or the combination of multi-mode ribbon fiber arrays and optical lenses. Among them, the ribbon fiber array assembly is a key element, which is responsible for connecting the internal lens and the external interface, and its optical interface uses standard MT / MPO connectors.

[0003] With the explosive demand for speed and bandwidth in data centers, the increase in the number of channels leads to a sharp increase in the number of optical fibers, and high-density wiring faces severe challenges. Multi-channel high-density packaging such as CPO must rely on ribbon fiber arrays (FA) and high-density connectors such as MT / MPO. However, this packaging process requires extremely high precision, and there are risks of fiber cracking, poor mode spot matching, end face defects, and long-term limited bending performance degradation during the process.

[0004] Conventional optical modules have extremely strict length tolerance requirements for fiber arrays due to limited internal space and the need to control fiber bending loss. Improper length can cause connector misalignment, module function abnormalities; too small bending radius not only significantly increases the loss at a specific location, but also causes the fiber to bear a large stress, which poses a long-term failure risk, which puts high requirements on the manufacturing yield of fiber suppliers.

[0005] When wiring the system, the ribbon fiber bending radius requirement (usually ≥15mm) must be strictly followed to avoid signal attenuation or distortion. The design needs to reserve enough wiring space to ensure smooth bending of the fiber and avoid stacking stress. At the same time, the operator of the fiber disc needs to maintain a safe bending radius throughout the process to prevent damage. Improper operation not only increases the optical loss, but also may cause stress concentration and performance degradation due to improper excess length.

[0006] Specifically includes: 1. Space conflict problem under high-density packaging: Traditional ribbon fibers need to meet the physical limitation of ≥15mm bending radius, which occupies excessive space in the trend of miniaturization and high-density packaging of optical modules. Especially in advanced packaging scenarios such as CPO / NPO / LPO, the layout of multi-channel fibers and the demand for module size reduction create a fundamental contradiction, severely restricting the integration level.

[0007] 2. Reliability defects caused by mechanical stress: Ribbon fibers can cause two types of structural risks due to improper control of excess length (redundant length): Excess length: causes fiber to bear tensile stress, accelerates fatigue fracture; Excess length: causes fiber to bear tensile stress, accelerates fatigue fracture; The stress accumulation will cause fiber cracks, end face damage and long-term optical performance degradation, significantly reducing the system life.

[0008] 3. Micro-scale space wiring adaptability is insufficient: Existing optical fibers face the following technical obstacles in ultra-compact bending scenarios with a bending radius ≤5mm: Bending loss increases dramatically, causing signal attenuation; Forced bending leads to deterioration of return loss indicators; Physical interference hinders high-precision disc fiber path planning; It is difficult to meet the wiring needs of continuously miniaturized data center equipment.

[0009] 4. Manufacturing process and operation cost rise; To avoid the high cost problem derived from the defects of traditional optical fibers: The production end needs to strictly control the micron-level length tolerance, significantly reducing the yield; The system design must reserve excess bending space, reducing cabinet space utilization.

[0010] Therefore, it is necessary to provide a flexible waveguide coupling structure for high-density optical engines and a miniaturized packaging method to solve the above problems. SUMMARY

[0011] The purpose of the present application is to provide a flexible waveguide coupling structure for high-density optical engines and a miniaturized packaging method.

[0012] The technical solution is as follows: A flexible waveguide coupling structure for high-density optical engines adopts a polymer optical waveguide, and the waveguide core layer is composed of a material with high refractive index. Since the refractive index of the core layer is higher than that of the upper and lower cladding layers, the light beam can reflect light on its surface or inside, thereby limiting the light beam in the core layer and transmitting it along the set path; Specifically, the flexible waveguide is used in high-density packaging, directly replacing the traditional ribbon fiber array, solving the contradiction between space limitation and bending radius; including a flexible waveguide and an MT / MPO connector; the flexible waveguide material is selected from PMMA, BCB, SU-8, FPPE, PSQ, PDMS / M-PDMS, etc. polymer, thickness ≤0.2mm, bendable radius ≤2mm, core / cladding refractive index difference Δn≥0.01, multi-mode numerical aperture NA≈0.3, transmission loss in the 850nm window ≤0.25dB / cm, coupling end face angle 40-50°, meeting the low loss and high bandwidth requirements of short-distance parallel optical interconnection.

[0013] Further, first, the polymer film is patterned and cut by a photolithography or imprinting process, then the core layer and cladding layer of the waveguide end are micro-nano processed by ultraviolet / femtosecond laser, the etching process is precisely controlled, and a 45° reflective surface array is formed on the light-emitting end surface of the waveguide, with an angle error ≤±0.5°; using the total reflection (TIR) principle of this 45° reflective surface, a 90° turn of the light path is realized, and the VCSEL light beam emitted vertically is folded into the horizontal waveguide core layer, or the received light signal in the waveguide core layer is folded to the detector chip; the loss of the 45° reflective end surface can be controlled within 0.5 dB, realizing low-loss and low-crosstalk coupling between the chip-waveguide-external connector.

[0014] Further, taking the implementation scheme of the VCSEL light-emitting chip and the flexible waveguide assembly in the light engine as an example, the light signal transmission is as follows: 1) the laser chip emits a light beam vertically; 2) the light beam is incident to the 45° end surface of the waveguide; 3) the light beam is reflected by the 45° end surface of the flexible waveguide, and the light path is turned by 90°; 4) the light beam enters the waveguide core layer for horizontal transmission; 5) output through the MT / MPO connector.

[0015] The second technical solution is: A miniaturized packaging method of a flexible waveguide coupling structure for a high-density light engine, comprising the following steps: A. Flexible waveguide fabrication and processing; B. Laser etching a reflective surface on the end surface; C. Assembling an MT / MPO connector with the waveguide; D. Assembling and soldering elements such as optical chips and electrical chips on a PCBA or substrate; E. Clamping the coupling product and the waveguide assembly with a coupling jig; F. Multi-dimensional adjustment and coupling of the light path; G. UV pre-curing between the waveguide assembly and the PCBA or substrate; H. Secondary curing between the waveguide assembly and the PCBA or substrate; I. Enclosure testing.

[0016] Further, the flexible waveguide is used in high-density packaging to directly replace the traditional ribbon fiber array, solving the contradiction between space limitation and bending radius; the flexible waveguide, MT / MPO optical interface and microlens array are included; the flexible waveguide material is selected from polymers such as PMMA, BCB, SU-8, FPPE, PSQ and PDMS / M-PDMS, the thickness is less than or equal to 0.2 mm, the bendable radius is less than or equal to 2 mm, the core / cladding refractive index difference Δn is greater than or equal to 0.01, the multi-mode numerical aperture NA is approximately 0.3, the transmission loss at the 850 nm window is less than or equal to 0.25 dB / cm, and the angle of the coupling end face is 40-50°, meeting the low-loss and high-bandwidth requirements of short-distance parallel optical interconnection.

[0017] Further, first, the polymer film is patterned and cut by using a photolithography or imprint process, then the core layer and the cladding layer of the waveguide end are micro-nano processed by using ultraviolet / femtosecond laser, the etching process is accurately controlled, a 45° reflecting surface array is formed on the light emitting end face of the waveguide, and the angle error is less than or equal to ±0.5°; by using the total reflection (TIR) principle of the 45° reflecting surface, 90° turning of the light path is realized, and the light beam is shaped and converged through the microlens array, finally the VCSEL light beam vertically emitted is folded to the horizontal waveguide core layer, or the received light signal in the waveguide core layer is folded to the detector chip. The loss of the 45° reflecting end face can be controlled within 0.5 dB, realizing low-loss and low-crosstalk coupling between the chip-waveguide-external connector.

[0018] Compared with the prior art, the flexible waveguide is used in the optical engine, and the application exhibits significant comprehensive advantages in space integration, far exceeding the traditional fiber solution: 1. Excellent bending flexibility: one of the most prominent features is the extremely small allowable bending radius (as low as 2 mm); greatly improving the wiring freedom and space utilization, especially suitable for compact devices with high space limitations.

[0019] 2. Ultra-thin morphology: the waveguide presents an ultra-thin film morphology, and the thickness or height is greatly compressed compared with the traditional ribbon fiber; effectively reducing the space occupied by the device in the Z-axis direction (height direction).

[0020] 3. Unique vertical stacking capability: flexible waveguides can be arranged vertically on the longitudinal space (Z-axis); at the same time, they can be stacked vertically with other planarized or miniaturized electronic components such as resistors, capacitors, etc. This three-dimensional integration capability breaks through the limitations of traditional fiber flat laying. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a direct coupling scheme of the waveguide and the optical chip of embodiment 1 of the application, a flexible waveguide and an optical chip direct coupling scheme light path and structure schematic diagram; Figure 2 is a direct coupling scheme of the waveguide and the optical chip of embodiment 1 of the present application, a flexible waveguide (with a reinforcing plate) and an optical chip direct coupling scheme optical path and structural schematic diagram; Figure 3 is a product process flow diagram of the direct coupling scheme of the waveguide and the optical chip of embodiment 1 of the present application; Figure 4 is a coupling packaging scheme of the present application, which increases the filling of optical glue, a flexible waveguide and an optical chip filled with optical glue scheme optical path and structural schematic diagram; Figure 5 is a coupling packaging scheme of the present application, which increases the filling of optical glue, a flexible waveguide (with a reinforcing plate) and an optical chip filled with optical glue scheme optical path and structural schematic diagram; Figure 6 is a product process flow diagram of the coupling packaging scheme of the present application, which increases the filling of optical glue; Figure 7 is a coupling packaging scheme of the present application, which increases the lens, a flexible waveguide and an optical chip using lens (array) scheme optical path and structural schematic diagram; Figure 8 is a coupling packaging scheme of the present application, which increases the lens, a flexible waveguide (with a reinforcing plate) and an optical chip using lens (array) scheme optical path and structural schematic diagram; Figure 9 is a product process flow diagram of the coupling packaging scheme of the present application, which increases the lens. DETAILED DESCRIPTION Embodiment 1:

[0022] Referring to Figures 1-3 , this embodiment shows a direct coupling scheme of a waveguide and an optical chip, which adopts a polymer optical waveguide. The core layer of the waveguide is composed of a material with high refractive index. Since the refractive index of the core layer is higher than that of the upper and lower cladding layers, the light beam can reflect light on the surface or inside, so as to limit the light beam in the core layer and transmit along the set path. Specifically, the flexible waveguide is used in high-density packaging to directly replace the traditional ribbon fiber array, solving the contradiction between space limitation and bending radius. The flexible waveguide, the MT / MPO connector, the PMMA, BCB, SU-8, FPPE, PSQ, PDMS / M-PDMS polymer, the thickness ≤0.2 mm, the bendable radius ≤2 mm, the core / cladding refractive index difference Δn ≥0.01, the multimode numerical aperture NA ≈0.3, the transmission loss in the 850 nm window ≤0.25 dB / cm, and the coupling end face angle 40-50° are selected, which meet the requirements of short-distance parallel optical interconnection with low loss and high bandwidth.

[0023] First, the polymer film is patterned and cut by photolithography or embossing process, and then the core layer and cladding layer of the waveguide end are micro-machined by ultraviolet / femtosecond laser. The etching process is precisely controlled to form a 45° reflective surface array on the light-emitting end surface of the waveguide, and the angle error is ≤±0.5°. By using the total reflection (TIR) principle of the 45° reflective surface, a 90° turn of the light path is realized, and the vertically emitted VCSEL light beam is folded into the horizontal waveguide core layer, or the received light signal in the waveguide core layer is folded to the detector chip. The loss of the 45° reflective end surface can be controlled within 0.5 dB, realizing low-loss and low-crosstalk coupling between the chip-waveguide-external connector.

[0024] The packaging step includes: A. Flexible waveguide manufacturing and processing; B. Laser etching a reflective surface on the end surface; C. Waveguide assembly MT / MPO connector; D. Assembly, soldering of elements such as optical chips, electrical chips, etc. on PCBA or substrate; E. Coupling work clamp holds the coupled product and waveguide assembly; F. Multi-dimensional adjustment and coupling of optical path; G. UV pre-curing between waveguide assembly and PCBA or substrate; H. Secondary curing between waveguide assembly and PCBA or substrate; I. Enclosure test. Embodiment 2:

[0025] Referring to Figures 4-6 , this embodiment shows a coupling packaging scheme that increases the filling of optical glue. A polymer optical waveguide is used, and the waveguide core layer is composed of high refractive index material. Because the refractive index of the core layer is higher than that of the upper and lower cladding layers, the light beam can reflect light on the surface or inside, thereby restricting the light beam in the core layer and transmitting along the set path. Specifically, flexible waveguide is used in high-density packaging to directly replace traditional ribbon fiber array, solving the contradiction between space limitation and bending radius; including flexible waveguide, MT / MPO connector, and refractive index matching optical glue; the flexible waveguide material is selected from PMMA, BCB, SU-8, FPPE, PSQ, PDMS / M-PDMS, etc. polymer, thickness ≤0.2mm, bendable radius ≤2mm, core / cladding refractive index difference Δn≥0.01, multi-mode numerical aperture NA≈0.3, transmission loss at 850nm window ≤0.25dB / cm, coupling end surface angle 40-50°, meeting the requirements of low loss and high bandwidth for short-distance parallel optical interconnection.

[0026] First, the polymer film is patterned and cut by photolithography or embossing process, and then the core layer and cladding layer of the waveguide end are micro-machined by UV / femtosecond laser, the etching process is precisely controlled, and a 45° reflective surface array is formed on the waveguide light emitting end face, with an angle error of ≤±0.5°; using the total reflection (TIR) principle of this 45° reflective surface, a 90° turning of the light path is realized, and optical glue with matching refractive index is added between the 45° light emitting end face of the waveguide and the optical chip to reduce the reflection and scattering of light waves on the interface. Finally, the vertically emitted VCSEL light beam is folded into the horizontal waveguide core layer, or the received light signal in the waveguide core layer is folded to the detector. The loss of the 45° reflective end face can be controlled within 0.5 dB, realizing low-loss and low-crosstalk coupling between chip-waveguide-external connector.

[0027] The packaging steps include: A. Flexible waveguide manufacturing and processing; B. Laser etching reflective surface on end face; C. Waveguide assembly MT / MPO connector; D. Assembly of optical chips, electrical chips and other elements on PCBA or substrate, soldering F. Coupling work clamp holds the coupled product and waveguide assembly; G. Fill optical glue; H. Light path multi-dimensional adjustment and coupling; I. UV pre-curing between waveguide assembly and PCBA or substrate; J. Secondary curing between waveguide assembly and PCBA or substrate; K. Enclosure test.

[0028] Implementation 3: Referring to Figures 7-9 , this embodiment shows a coupling packaging scheme with increased lens, which uses a polymer optical waveguide. The core layer of the waveguide is composed of high refractive index material. Because the refractive index of the core layer is higher than that of the upper and lower cladding layers, the light beam can reflect light on the surface or inside, thereby restricting the light beam in the core layer and transmitting along the set path; Specifically, the flexible waveguide is used in high-density packaging to directly replace the traditional ribbon fiber array, solving the contradiction between space limitation and bending radius; the flexible waveguide, MT / MPO connector, and microlens array are included; the flexible waveguide material is selected from polymers such as PMMA, BCB, SU-8, FPPE, PSQ, and PDMS / M-PDMS, with a thickness of ≤0.2 mm, a bendable radius of ≤2 mm, a core / cladding refractive index difference Δn≥0.01, a multi-mode numerical aperture NA≈0.3, a transmission loss of ≤0.25 dB / cm at 850 nm window, and an angle of 40-50° at the coupling end face, meeting the requirements of low loss and high bandwidth for short-distance parallel optical interconnection.

[0029] First, the polymer thin film is patterned and cut into waveguides using photolithography or imprinting. Then, ultraviolet / femtosecond lasers are used to micro- and nano-fabricate the core and cladding layers at the waveguide ends, precisely controlling the etching process to form a 45° reflective surface array on the light-emitting end face of the waveguide, with an angle error ≤ ±0.5°. Utilizing the total internal reflection (TIR) ​​principle of this 45° reflective surface, a 90° bend in the optical path is achieved, and a microlens array is used to shape and converge the beam, reducing energy loss during coupling and improving coupling efficiency. Ultimately, the vertically emitted VCSEL beam is refracted back into the horizontal waveguide core layer, or the received optical signal from the waveguide core layer is refracted back to be transmitted to the detector chip. The loss of this 45° reflective end face can be controlled within 0.5dB, achieving low-loss, low-crosstalk coupling between the chip, waveguide, and external connector.

[0030] The packaging process includes: A. Fabrication and processing of flexible waveguides; B. Laser etching is used to create a reflective surface on the end face; C. Waveguide assembly with MT / MPO connectors; D. Waveguide and lens micro / nano-level alignment; E. Curing of the optical adhesive between the waveguide and the lens; F. Assembly and bonding of components such as optical chips and electrical chips on PCBA or substrate; H. Coupling clamps hold the products to be coupled, waveguide components; I. Multidimensional adjustment of optical path coupling; J. UV pre-curing between waveguide components and PCBA or substrate; K. Secondary curing between waveguide components and PCBA or substrate; L. Sealing test.

[0031] Compared with existing technologies, this invention uses flexible waveguides in the optical engine, which can show significant comprehensive advantages in spatial integration, far exceeding traditional fiber optic solutions: 1. Excellent bending flexibility: One of its most outstanding features is its extremely small allowable bending radius (as low as 2mm); which greatly improves the freedom of wiring and space utilization, especially suitable for compact equipment with limited space.

[0032] 2. Ultra-thin morphology and structure: The waveguide is in the form of an ultra-thin film, and its thickness or height is greatly reduced compared to traditional ribbon optical fiber; effectively reducing the space occupied by the device in the Z-axis direction (height direction).

[0033] 3. Unique vertical stacking capability: Flexible waveguides can be stacked on top of each other in the longitudinal space (Z-axis); at the same time, they can be stacked vertically with other planar or miniaturized electronic components such as resistors and capacitors. This three-dimensional integration capability breaks through the limitations of traditional planar fiber optic cabling.

[0034] For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this invention, and these all fall within the protection scope of this invention.

Claims

1. A flexible waveguide coupling structure for high-density optical engines, characterized in that: A polymer optical waveguide is used, with the waveguide core layer made of a high refractive index material. Since the core layer has a higher refractive index than the upper and lower cladding layers, the light beam can be reflected on its surface or inside, thereby confining the light beam in the core layer and transmitting it along a set path. Specifically, this involves using flexible waveguides in high-density optical engine packaging to directly replace traditional ribbon fiber arrays, resolving the conflict between space constraints and bending radius; this includes flexible waveguides, MT / MPO connectors, and microlens arrays. The flexible waveguide material is selected from polymers such as PMMA, BCB, SU-8, FPPE, PSQ, and PDMS / M-PDMS, with a thickness ≤0.2mm, a bendable radius ≤2mm, a core / cladding refractive index difference Δn ≥0.01, a multimode numerical aperture NA≈0.3, a transmission loss ≤0.25 dB / cm in the 850 nm window, and a coupling end face angle of 40-50°, meeting the requirements of low loss and high bandwidth for short-distance parallel optical interconnects.

2. The flexible waveguide coupling structure for high-density optical engines according to claim 1, characterized in that: First, the polymer thin film is patterned and cut into waveguides using photolithography or imprinting. Then, ultraviolet / femtosecond lasers are used to micro- and nano-fabricate the core and cladding layers at the waveguide ends, precisely controlling the etching process to form a 45° reflective surface array on the light-emitting end face of the waveguide, with an angle error ≤ ±0.5°. Utilizing the total internal reflection (TIR) ​​principle of this 45° reflective surface, a 90° deflection of the optical path is achieved, refracting the vertically emitted VCSEL beam towards the incident horizontal waveguide core layer, or refracting the received optical signal in the waveguide core layer towards the detector chip. The loss of this 45° reflective end face can be controlled within 0.5dB, achieving low-loss, low-crosstalk coupling between the chip, waveguide, and external connector.

3. A flexible waveguide coupling structure for high-density optical engines according to claim 1, characterized in that: Taking the implementation scheme of VCSEL emitting optical chip and flexible waveguide component in optical engine as an example, optical signal transmission: 1) The laser chip emits a beam vertically; 2) The beam is incident on the 45° end face of the waveguide; 3) The light beam is reflected by the 45° end face of the flexible waveguide, and the optical path undergoes a 90° bend; 4) The light beam enters the waveguide core and propagates horizontally; 5) Output via MT / MPO connector.

4. A miniaturized packaging method for a flexible waveguide coupling structure for high-density optical engines, characterized in that: The packaging process includes: A. Fabrication and processing of flexible waveguides; B. Laser etching is used to create a reflective surface on the end face; C. Waveguide assembly with MT / MPO connectors; D. Components such as optical chips and electrical chips are assembled and wired on PCBAs or substrates; E. Coupling clamps hold the products to be coupled, waveguide components; F. Multidimensional adjustment of optical path coupling; G. UV pre-curing between waveguide components and PCBA or substrate; H. Secondary curing between waveguide components and PCBA or substrate; I. Shell testing.

5. The miniaturized packaging method for a flexible waveguide coupling structure for a high-density optical engine according to claim 4, characterized in that: Flexible waveguides can be used in high-density packaging to directly replace traditional ribbon fiber arrays, solving the contradiction between space constraints and bending radius; including flexible waveguides, MT / MPO connectors, and microlens arrays. The flexible waveguide material is selected from polymers such as PMMA, BCB, SU-8, FPPE, PSQ, and PDMS / M-PDMS, with a thickness ≤0.2mm, a bendable radius ≤2mm, a core / cladding refractive index difference Δn ≥0.01, a multimode numerical aperture NA≈0.3, a transmission loss ≤0.25 dB / cm in the 850 nm window, and a coupling end face angle of 40-50°, meeting the requirements of low loss and high bandwidth for short-distance parallel optical interconnects.

6. The miniaturized packaging method for a flexible waveguide coupling structure for a high-density optical engine according to claim 5, characterized in that... First, the polymer thin film is patterned and cut into waveguides using photolithography or imprinting. Then, ultraviolet / femtosecond lasers are used to perform micro-nano processing on the core and cladding layers at the waveguide ends. The etching process is precisely controlled to form a 45° reflective surface array on the light-emitting end face of the waveguide, with an angle error ≤ ±0.5°. Utilizing the total internal reflection (TIR) ​​principle of this 45° reflective surface, a 90° bend in the optical path is achieved, refracting the vertically emitted VCSEL beam into the incident horizontal waveguide core layer, or refracting the received optical signal in the waveguide core layer to transmit it to the detector chip. The loss of this 45° end face can be controlled within 0.5dB, achieving low-loss, low-crosstalk coupling between the chip, waveguide, and external connector.

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