A detachable CPO light engine and its packaging method

Abstract

The application discloses a detachable CPO light engine with optical fibers and a packaging method thereof. The packaging method comprises the following steps: obtaining a fiber array gold sample provided with a plurality of guide needle holes and optical fiber channels, and inserting a plurality of guide needles into the guide needle holes one by one; obtaining a light path switching chip prepared by using a glass substrate, processing a plurality of coupling holes on the light path switching chip, and setting the diameter of the coupling holes to be larger than the outer diameter of the guide needles; inserting the part of the guide needles extending out of the guide needle holes into the coupling holes, and performing active coupling alignment between the optical fiber channels in the fiber array gold sample and a mode spot conversion optical waveguide; after the alignment, injecting an adhesive into the coupling holes for curing, so that the guide needles are fixed in the coupling holes; and pulling out the fiber array gold sample, so that the guide needles are retained on the light path switching chip and used for plug-in connection with an external fiber array. The application solves the problem that the glass substrate hole machining precision is insufficient and high-precision passive alignment cannot be realized by using the coupling hole and active coupling mode.

Description

Technical Field

[0001] This application relates to the field of optical communication packaging technology, and in particular to a fiber optic detachable CPO optical engine and its packaging method. Background Technology

[0002] Co-Packaged Optics (CPO) technology, as a cutting-edge solution in data centers and optical communications, significantly improves data transmission rates and energy efficiency by co-packaging optical engines with switching chips. As data centers move towards the 800G / 1.6T era, CPO technology has become a key solution to overcome the "power wall" and "bandwidth wall."

[0003] Currently, the industry has proposed a technical solution to achieve detachable connection of fiber arrays in CPO optical engines through a pin insertion and removal structure. However, the core bottleneck faced by this type of solution in engineering implementation is that high-precision alignment between the pins and the optical path adapter chip is difficult to achieve.

[0004] Specifically, if the optical path adapter chip is fabricated using a glass substrate, the processing characteristics of the glass substrate limit the ability to achieve sub-micron precision (MT level) for the guide pin holes. The aperture tolerance and spacing tolerance are far greater than the precision requirements for optical path alignment. If passive alignment is achieved solely through mechanical means, the positional deviation between the guide pins and the waveguide will directly lead to a significant decrease in the coupling efficiency between the fiber channel and the mode-converting waveguide, failing to meet the CPO optical engine's performance requirements for low insertion loss and high coupling precision. Summary of the Invention

[0005] This application provides a packaging method for a detachable optical fiber CPO optical engine and a CPO optical engine, so as to at least partially solve the technical problem that insufficient processing accuracy of the glass substrate hole in the existing CPO optical engine leads to difficulties in high-precision positioning and fixing of the guide pin.

[0006] In a first aspect, this application provides a method for packaging a fiber-removable CPO optical engine, the method comprising: Obtain a gold sample of an optical fiber array with multiple guide pin holes and optical fiber channels, and insert multiple guide pins into the guide pin holes one by one. An optical path adapter chip prepared by a glass substrate is obtained, and multiple coupling holes are processed on the optical path adapter chip, wherein the diameter of the coupling hole is larger than the outer diameter of the guide pin; Insert the portion of the guide pin extending out of the guide pin hole into the coupling hole to achieve active coupling alignment between the fiber channel in the fiber array gold sample and the mode conversion waveguide. After alignment, inject adhesive into the coupling hole for curing to fix the guide pin into the coupling hole. Remove the optical fiber array sample, leaving the guide pin on the optical path adapter chip for plugging and unplugging connection with an external optical fiber array.

[0007] In one embodiment of this application, the diameter of the coupling hole is 20 μm to 50 μm larger than the outer diameter of the guide pin.

[0008] In one embodiment of this application, the optical path adapter chip has an end face protection groove, and the waveguide port on one side of the mode conversion optical waveguide is located at the bottom of the end face protection groove; the groove depth of the end face protection groove is 2μm to 3μm.

[0009] In one embodiment of this application, an outwardly protruding limiting portion is formed on the optical fiber array gold sample, and the active coupling alignment of the optical fiber channel in the optical fiber array gold sample with the mode-spot conversion waveguide includes the following steps: The limiting part extends into the end face protection groove and is fitted with the bottom of the end face protection groove with a gap. The limiting part is moved along the extension direction of the side wall of the end face protection groove until the optical fiber channel of the optical fiber array gold sample coincides with the mode conversion optical waveguide.

[0010] In one embodiment of this application, when the limiting part is moved along the extending direction of the sidewall of the end face protection groove, the limiting part is fitted to the sidewall of the end face protection groove, so that the optical fiber channel and the mode conversion waveguide are on the same plane.

[0011] In one embodiment of this application, the optical fiber channel includes a first channel and a second channel located on the outermost side of the optical fiber array gold sample, wherein the optical fiber channel extending to the optical fiber array gold sample coincides with the mode-spot conversion waveguide, comprising the following steps: Select the first and second channels as alignment channels; Optical signals are input into the optical fibers of the first channel and the second channel, and the first output optical power and the second output optical power are detected at the other end of the mode-spot conversion optical waveguides corresponding to the first channel and the second channel, respectively. Adjust the relative position of the fiber array sample and the optical path adapter chip in a plane perpendicular to the optical axis, as well as the rotation angle around the optical axis, until the first output optical power and the second output optical power simultaneously reach their maximum values.

[0012] In one embodiment of this application, the waveguide spacing of each adjacent mode-spot conversion waveguide is equal to the channel spacing of each adjacent fiber channel in the fiber array sample, and the spacing deviation of adjacent mode-spot conversion waveguides is ≤0.5μm.

[0013] In one embodiment of this application, the bottom wall of the end face protection groove is covered with an anti-reflection membrane.

[0014] In one embodiment of this application, the optical path adapter chip has a dispensing window that connects to the coupling hole, and the adhesive is injected into the coupling hole through the dispensing window; and / or the curing shrinkage of the adhesive is in the nanometer range.

[0015] Secondly, this application provides a CPO optical engine, prepared using the encapsulation method described in any of the above embodiments, wherein the CPO optical engine comprises: Packaging substrate; A driving electrical chip is disposed on the packaging substrate and electrically connected to the packaging substrate; A silicon photonics chip is electrically connected to the driving electrical chip; An optical path conversion chip includes a glass substrate body prepared by a glass substrate and multiple mode-spot conversion optical waveguides formed inside the glass substrate body, wherein the first waveguide port of the mode-spot conversion optical waveguide is coupled to the optical waveguide of the silicon photonic chip. Multiple guide pins are fixed inside the coupling holes of the optical path adapter chip and extend out of the glass substrate body for detachable plug-in connection with an external fiber optic array.

[0016] The packaging method for the detachable CPO optical engine provided in this application involves obtaining a fiber array sample with a guide pin hole and a fiber channel, precisely fixing the guide pin in the guide pin hole, obtaining an optical path adapter chip made of a glass substrate, processing a coupling hole on the chip with a diameter larger than the outer diameter of the guide pin, inserting the protruding part of the guide pin into the coupling hole, using the gap between the coupling hole and the guide pin to actively couple and align the fiber channel in the fiber array sample with the mode conversion waveguide, injecting adhesive into the coupling hole after alignment to fix the guide pin, and finally pulling out the fiber array sample to leave the guide pin on the optical path adapter chip for plugging and unplugging connection with an external fiber array.

[0017] The method provided in this application embodiment utilizes a low-precision coupling hole with an aperture larger than the outer diameter of the guide pin, and combines it with an optical fiber array gold sample carrying the guide pin for active coupling alignment. This transforms the low-precision mechanical structure into a high-precision optical alignment, solving the problem that the glass substrate hole processing precision is insufficient and therefore cannot achieve high-precision passive alignment. Meanwhile, after active coupling alignment, the guide pin is fixed in the optimal position of the optical path in the coupling hole by adhesive, so that the external fiber array can be detachably plugged and unplugged through the guide pin. This takes into account both the high-precision alignment of the optical path and the detachable requirements of the fiber array, and significantly improves the coupling accuracy, yield and maintainability of the CPO optical engine. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the structure of an "end-to-end" optical path transition chip provided in this application embodiment; Figure 2 A schematic diagram of the structure of an "end-to-bottom" optical path transition chip provided in this application embodiment; Figure 3 This is a schematic diagram of the structure of a fiber array gold sample provided in an embodiment of this application; Figure 4 This is a schematic diagram of the structure of a high-precision metal guide needle provided in an embodiment of this application; Figure 5 Schematic diagrams of the optical port types of two silicon photonic chips provided in the embodiments of this application; Figure 6 A schematic diagram of the coupling and bonding process between an "end-to-end" optical path transition chip and an end-to-end coupled silicon photonics chip provided in an embodiment of this application; Figure 7 A schematic diagram of a detachable CPO optical engine for an end-coupled fiber array provided in this application embodiment; Figure 8 A schematic diagram of a switch architecture based on a detachable CPO optical engine of an end-face coupled fiber array provided for embodiments of this application; Figure 9 A schematic diagram of the coupling and bonding process between an "end-to-bottom" light-in / out optical path adapter chip and a surface-coupled silicon photonics chip provided in an embodiment of this application; Figure 10 A schematic diagram of a detachable CPO optical engine for surface-coupled fiber arrays provided in this application embodiment; Figure 11 A schematic diagram of a switch architecture based on a detachable CPO optical engine of a surface-coupled fiber array, provided for embodiments of this application; Figure 12 This is a schematic diagram of the structure of an "end-to-end" optical path adapter chip for multi-core optical fibers, provided in an embodiment of this application.

[0020] 1. First optical path adapter chip; 101. First mode-spot conversion optical waveguide; 102. Silicon photonics chip coupling end face waveguide port; 103. Fiber optic coupling end face waveguide port; 104. Coupling hole; 105. Adhesive dispensing window; 106. End face protection groove; 2. Second optical path adapter chip; 201. Second mode conversion optical waveguide; 202. Silicon photonics chip coupling bottom waveguide port; 3. Fiber optic array gold sample; 301. Guide pin hole; 302. Substrate; 303. Fiber optic channel; 304. Fiber optic coating layer; 4. Guide needle; 501. End-face coupled silicon photonics chip; 502. Surface coupled silicon photonics chip; 702. Driver chip; 703. TGV substrate; 704. Hybrid bonding pad; 705. BGA solder joint; 706. Contact pad; 707. UV adhesive; 708. Optical matching adhesive; 709. End-face light-emitting silicon waveguide; 801. Switch chip; 802. Switch motherboard; 1002, Surface-emitting silicon waveguide; 1003, UV optical matching adhesive; 1004, Encapsulation substrate; 1201. Square-distributed waveguide end face. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0022] In the embodiments of this application, "at least one" refers to one or more; "multiple" refers to two or more. In the description of this application, the terms "first," "second," "third," etc., are used only for the purpose of distinguishing descriptions and should not be construed as indicating or implying relative importance, nor should they be construed as indicating or implying order.

[0023] References such as "one embodiment" or "some embodiments" as used in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the terms "comprising," "including," "having," and variations thereof in this specification mean "including but not limited to," unless otherwise specifically emphasized.

[0024] To clearly understand the packaging method and the CPO optical engine with detachable fiber optic cable provided in this application embodiment, the relevant application scenarios are first described below. Specifically, CPO (Co-Packaged Optics) technology, by co-packaging the optical engine with the switching chip, can significantly improve the data transmission rate and energy efficiency of data centers. In the CPO optical engine, the fiber array (FA) is used to realize the input and output of optical signals and is a key component of the optical engine.

[0025] This application provides a packaging method for a detachable optical fiber CPO optical engine and a CPO optical engine. By using an optical path adapter chip made of glass substrate, coupling holes with a diameter larger than the outer diameter of the guide pin are processed on the optical path adapter chip. Active coupling alignment is performed by using a gold sample of an optical fiber array to carry the guide pin. This solves the problem that the low hole processing accuracy of the glass substrate makes it impossible to achieve high-precision passive alignment, and transforms the low-precision mechanical structure into high-precision optical alignment.

[0026] This application provides a method for packaging a fiber-removable CPO optical engine, the method comprising the following steps: Obtain a gold sample 3 of an optical fiber array with multiple guide pin holes 301 and optical fiber channels 303, and insert multiple guide pins 4 into the guide pin holes 301 in a corresponding manner.

[0027] In one embodiment of this application, please refer to Figure 3 The fiber array gold sample 3 includes a substrate 302, a guide pin hole 301 and a fiber channel 303, all of which are formed on the substrate 302.

[0028] In one embodiment of this application, the substrate 302 is prepared using PPI plastic doped with glass fibers. The purpose of doping with glass fibers is to improve the dimensional stability of the PPI plastic substrate 302 under high and low temperature environments. It should be noted that this application does not impose specific limitations on the material selection of the substrate 302. In other embodiments, other suitable forms may also be used, such as using metal materials.

[0029] The fiber optic channel 303 contains a bare single-mode fiber optic cable, which is fixed to the fiber optic channel 303 by adhesive bonding. The outer fiber optic cable has a fiber coating layer 304, which, together with the tail fiber protective adhesive, is used to protect the fiber optic cable.

[0030] It should be noted that the fiber array gold sample 3 is not a material used in batches for the product, but a sample with near-zero tolerance selected from multiple samples, used to assist the active coupling positioning of the guide pin 4.

[0031] For example, the screening criteria for the fiber optic array gold sample 3 are as follows: The inner diameter tolerance of the guide pin hole 301 is less than 0.3μm, the spacing tolerance of the guide pin hole 301 is less than 0.4μm, the fiber core spacing of the fiber channel 303 is 250μm, the number of channels is 4, and the spacing tolerance is less than 0.3μm.

[0032] Before inserting the guide pin 4 into the guide pin hole 301, the optical fiber array gold sample 3 needs to be visually inspected to ensure that the tolerance of the above-mentioned key assembly dimensions is close to zero and there are no wear or other appearance defects.

[0033] For example, the fiber array gold sample 3 also needs to be tested for insertion loss (IL). In one specific embodiment, the test IL is required to be less than 0.3 dB. The bare fiber in the fiber channel 303 is bonded and fixed with thermosetting adhesive at a curing temperature below 110°C for 1 hour.

[0034] Please see Figure 4 After the guide pin 4 is inserted into the guide pin hole 301, the outer diameter of the guide pin 4 matches the inner diameter of the guide pin hole 301, so that the guide pin 4 cannot move within the guide pin hole 301, and the spacing between multiple guide pins 4 is precisely fixed.

[0035] After insertion, the position of the guide pin 4 is constrained by the hole wall of the guide pin hole 301, and the relative positional relationship between the guide pin 4 and the fiber optic channel 303 is fixed, providing a mechanical reference for subsequent active coupling alignment. When adjusting the position of the gold sample during subsequent active coupling alignment, the guide pin 4 will also move synchronously to the optimal position corresponding to the alignment state.

[0036] An optical path adapter chip prepared by a glass substrate is obtained, and a plurality of coupling holes 104 are processed on the optical path adapter chip, wherein the diameter of the coupling hole 104 is larger than the outer diameter of the guide pin 4.

[0037] In one embodiment of this application, please refer to Figure 1 The optical path conversion chip is an "end-to-end" input / output optical path conversion chip, which is referred to as the first optical path conversion chip 1 for ease of explanation. This optical path conversion chip uses a glass substrate, and multiple mode-spot conversion optical waveguides are written inside the glass substrate using three-dimensional laser direct writing technology. For ease of explanation, these are referred to as the first mode-spot conversion optical waveguide 101.

[0038] Unlike planar optical waveguide chips manufactured using ordinary PLC processes, the three-dimensional laser direct writing technology allows the two ends of the first mode-spot conversion optical waveguide 101 to be designed with different mode-spot sizes to match the mode-spots of silicon photonic waveguides and single-mode optical fibers, respectively. At the same time, the heights of the two ends of the first mode-spot conversion optical waveguide 101 inside the chip can be designed with different heights to match the height of the silicon photonic chip waveguide and the height of the fiber core of the external fiber array.

[0039] Specifically, the two ends of the first mode-spot conversion waveguide 101 have different mode-spot sizes.

[0040] The mode size on one side of the silicon photonic chip coupling end face waveguide port 102 is 4μm to 6μm, which is used to match the mode size of the silicon photonic chip end face coupler; the mode size on one side of the fiber coupling end face waveguide port 103 is 8μm to 10μm, which is used to match the mode size of ordinary single-mode fiber.

[0041] For example, the mode size of the silicon photonic chip coupling end face waveguide port 102 is 4.5 μm, which is a circular mode, the channel spacing is 127 μm, and the number of channels is 4; the mode size of the fiber coupling end face waveguide port 103 is 8.5 μm, which is a circular mode, the channel spacing is 250 μm, and the number of channels is 4.

[0042] For example, the material of the first optical path adapter chip 1 is EXG glass.

[0043] In one embodiment of this application, please refer to Figure 2 The optical path adapter chip can also be a "face-to-face" input / output optical path adapter chip, which, for ease of explanation, is referred to as the second optical path adapter chip 2, and its corresponding mode-spot conversion optical waveguide is referred to as the second mode-spot conversion optical waveguide 201. The structure of the second optical path adapter chip 2 is roughly the same as that of the first optical path adapter chip 1, the difference being: One end of the second mode-spot conversion waveguide 201 is located on the end face of the chip (corresponding to the fiber coupling surface waveguide port 103), and the other end is located on the bottom surface of the chip, forming the silicon photonic chip coupling bottom surface waveguide port 202. The silicon photonic chip coupling bottom surface waveguide port 202 is used for coupling and bonding with the surface-coupled silicon photonic chip 502.

[0044] For example, the angle between the second mode-spot conversion waveguide 201 and the bottom surface of the chip is set to 82° to match the coupling angle of the silicon photonic surface mount grating coupler. It should be noted that in other embodiments, this angle can also be adaptively adjusted, for example, to 81° or 83°.

[0045] Furthermore, in one embodiment of this application, the diameter of the coupling hole 104 is 20 μm to 50 μm larger than the outer diameter of the guide pin 4.

[0046] Since the hole processing accuracy of glass substrate is difficult to reach the submicron level of MT, based on this situation, the diameter of coupling hole 104 is set to be significantly larger than the outer diameter of guide pin 4, so that guide pin 4 still has a certain amount of movement space after being inserted into coupling hole 104, thereby allowing precise position adjustment through relative movement during active coupling.

[0047] For example, in one specific embodiment, the lower limit of the inner diameter tolerance of the coupling hole 104 is 40 μm larger than the upper limit of the outer diameter tolerance of the guide pin 4.

[0048] Furthermore, in one embodiment of this application, the first optical path adapter chip 1 is provided with an end face protection groove 106, and the waveguide port (i.e., the fiber coupling surface waveguide port 103) on one side of the first mode conversion optical waveguide 101 is located at the bottom of the end face protection groove 106.

[0049] The depth of the end-face protection groove 106 is 2μm to 3μm. The end-face protection groove 106 is formed by etching inward in the corresponding rectangular area of ​​the end face of the optical path adapter chip. Its function is to prevent the external fiber array from directly contacting or impacting the waveguide end face of the chip during insertion and removal, thereby effectively protecting the integrity of the waveguide end face.

[0050] Furthermore, in one embodiment of this application, the bottom wall of the end face protection groove 106 is covered with an anti-reflection film (AR film).

[0051] The antireflective coating effectively reduces reflection caused by the air gap within the end-face protective groove 106, further improving coupling efficiency and the optical path reflection performance of the system. For example, the antireflective coating has a transmittance of 99.5% and a transmission center wavelength of 1310 nm.

[0052] Furthermore, in one embodiment of this application, the optical path adapter chip has a dispensing window 105 communicating with the coupling hole 104. The dispensing window 105 is disposed on the sidewall of the coupling hole 104 and is used to inject adhesive into the coupling hole 104 after active coupling alignment is completed.

[0053] The specific operation of injecting adhesive into coupling hole 104 through dispensing window 105 will be explained in detail in the subsequent active coupling alignment steps.

[0054] Insert the portion of the guide pin 4 extending out of the guide pin hole 301 into the coupling hole 104, so that the optical fiber channel 303 in the optical fiber array gold sample 3 is actively coupled and aligned with the first mode spot conversion optical waveguide 101. After alignment, inject adhesive into the coupling hole 104 for curing, so that the guide pin 4 is fixed in the coupling hole 104.

[0055] In one embodiment of this application, an outwardly protruding limiting portion (not shown in the figure) is formed on the optical fiber array gold sample 3. The active coupling alignment of the optical fiber channel 303 in the optical fiber array gold sample 3 with the first mode-spot conversion optical waveguide 101 includes the following steps: The limiting part extends into the end face protection groove 106 and is fitted with the bottom of the end face protection groove 106 with a clearance. The limiting part is moved along the extension direction of the side wall of the end face protection groove 106 until the optical fiber channel 303 of the optical fiber array gold sample 3 coincides with the first mode spot conversion optical waveguide 101.

[0056] Since the depth of the end face protection groove 106 is 2μm to 3μm, a gap fit is formed between the limiting part and the bottom of the end face protection groove 106, thereby realizing the coarse positioning of the optical fiber channel 303 and the first mode spot conversion optical waveguide 101 in the optical axis direction.

[0057] Furthermore, in one embodiment of this application, when the limiting part is moved along the extending direction of the sidewall of the end face protection groove 106, the limiting part is fitted to the sidewall of the end face protection groove 106, so that the optical fiber channel 303 and the first mode conversion optical waveguide 101 are in the same plane.

[0058] Correspondingly, in one embodiment of this application, the cross-section of the end-face protection groove 106 is square, that is, it has a set of first planes and a set of second planes symmetrically arranged. The limiting part is fitted with the first plane or the second plane, so that the optical fiber channel 303 and the first mode conversion optical waveguide 101 are initially aligned in the height direction and are in the same plane.

[0059] For example, after the initial alignment is completed, the limiting part is further moved along the extension direction of the first plane until the fiber channel 303 of the fiber array gold sample 3 coincides with the first mode conversion waveguide 101.

[0060] It should be noted that when the limiting part is limited by the second plane, the limiting part can be attached to one of the second planes or to both of the second planes. No further restrictions are imposed here. The key is to ensure that the second plane can provide a precise straight trajectory for the limiting part, and that the fiber optic channel 303 and the first mode conversion waveguide 101 are in the same plane.

[0061] In one embodiment of this application, the optical fiber channel 303 includes a first channel and a second channel located on the outermost side of the optical fiber array gold sample 3. The optical fiber channel 303 extending to the optical fiber array gold sample 3 coincides with the first mode-spot conversion optical waveguide 101, and includes the following steps: Select the first and second channels as alignment channels; Optical signals are input into the optical fibers of the first channel and the second channel, and the first output optical power and the second output optical power are detected at the other end of the first mode-spot conversion optical waveguide 101 corresponding to the first channel and the second channel, respectively. Adjust the relative position of the fiber array gold sample 3 and the first optical path adapter chip 1 in the plane perpendicular to the optical axis and the rotation angle around the optical axis until the first output optical power and the second output optical power reach their maximum values ​​simultaneously.

[0062] Specifically, during active coupling alignment, the first and second channels located on the outermost side of the fiber array gold sample 3 are selected as alignment channels, and optical signals are input into the optical fibers of these two alignment channels respectively.

[0063] At the other end of the first mode-spot conversion optical waveguide 101 corresponding to the first and second channels (i.e., at the silicon photonic chip coupling end face waveguide port 102), the first output optical power and the second output optical power are detected by a photodetector (PD).

[0064] Then, fix the first optical path adapter chip 1, and adjust the relative positions of the fiber array gold sample 3 and the first optical path adapter chip 1 in a plane perpendicular to the optical axis until the first output optical power and the second output optical power reach their maximum values ​​simultaneously.

[0065] When the output optical power of both optical fiber channels 303 (i.e., the first channel and the second channel) reaches its maximum value simultaneously, it indicates that the optical fiber channel 303 and the waveguide port 103 of the optical fiber coupling surface are perfectly aligned. For example, in one specific embodiment, the photosensitive surface of the photodetector is 300 μm, and the responsivity is 1 A / W.

[0066] In one embodiment of this application, the waveguide spacing of each adjacent first mode-converting waveguide 101 is equal to the channel spacing of each adjacent fiber channel 303 in the fiber array gold sample 3, and the spacing deviation of adjacent first mode-converting waveguides 101 is ≤0.5μm.

[0067] Because the waveguide spacing and the fiber channel 303 spacing are highly matched with minimal deviation, only the two outermost fiber channels 303 need to be coupled and aligned. The alignment of the middle fiber channel 303 is ensured by the material precision design. Understandably, this design simplifies the active coupling alignment process and improves production efficiency.

[0068] After active coupling alignment is completed, adhesive is injected into the coupling hole 104 for curing, thereby fixing the guide pin 4 into the coupling hole 104. In one embodiment of this application, the optical path adapter chip has a dispensing window 105 communicating with the coupling hole 104, and the adhesive is injected into the coupling hole 104 through the dispensing window 105.

[0069] Specifically, after active coupling alignment is completed and the optical path is confirmed to be in the optimal alignment state, adhesive is injected into the coupling hole 104 through the dispensing window 105 and cured to firmly bond and fix the guide pin 4 in the optimal position of the optical path inside the coupling hole 104.

[0070] Furthermore, in one embodiment of this application, the curing shrinkage of the adhesive is at the nanometer level, thereby ensuring that the positional offset of the guide pin 4 during the curing process is extremely small, maintaining the high-precision optical path state after active coupling alignment.

[0071] For example, a UV-curing adhesive is selected as the adhesive. In one specific embodiment, the brand and model of the adhesive is EMI 3410vm UV adhesive. This adhesive matches the coefficient of thermal expansion of the glass substrate, which improves the fixation stability of the guide pin 4 in high and low temperature environments.

[0072] Based on the above, after the guide pin 4 is fixed into the coupling hole 104, the optical path adapter chip and the silicon photonics chip need to be coupled, aligned, and the optical path solidified.

[0073] Please see Figure 5 , Figure 5 This diagram illustrates two types of optical port types for silicon photonics chips provided in this application embodiment. The silicon photonics chips include two types: end-coupled silicon photonics chip 501 and surface-coupled silicon photonics chip 502. The end-coupled silicon photonics chip 501 has its optical input and output ports located on the end face (side) of the chip and employs a silicon photonics edge-coupled SSC coupler design. The optical input and output ports of the surface-coupled silicon photonics chip 502 are located on the upper surface of the chip and are designed using a silicon photonics surface grating coupler. For example, the coupling waveguide / coupling grating spacing of the optical input and output ports of both the end-coupled silicon photonics chip 501 and the surface-coupled silicon photonics chip 502 is 127 μm, and the number of channels is 4.

[0074] Please see Figure 6 , Figure 6 This is a schematic diagram illustrating the coupling and bonding process between an "end-to-end" input / output optical path adapter chip (i.e., the first optical path adapter chip 1) and an end-face coupled silicon photonics chip 501, as provided in this embodiment of the application. When the optical path adapter chip is the first optical path adapter chip 1, the semi-finished product with the guide pin 4 fixed in the coupling hole 104 continues to be actively coupled and aligned with the end-face output silicon photonics waveguide 709 of the end-face coupled silicon photonics chip 501.

[0075] This coupling only requires coupling the two outermost fiber channels 303. The waveguides on both sides of the end-coupled silicon photonic chip 501 can be either input waveguides or output waveguides: for input waveguides, monitor the current responded by the backlight detector integrated inside the silicon photonic chip and couple it to the maximum value; for output waveguides, monitor the optical power output by the fiber and couple it to the maximum value.

[0076] For example, in one specific embodiment, the end-coupled silicon photonics chip 501 integrates a beam splitter and a backlight detector. The beam splitter has a splitting ratio of 5%, and the backlight detector has a responsivity of 0.8 A / W, which can be used to monitor the amount of silicon photonics light entering the chip in real time.

[0077] After coupling is completed, the first optical path adapter chip 1, coupled to the optimal position, is fixed to the TGV substrate 703 using bottom UV adhesive 707. Optical matching adhesive 708 is filled in the coupling gap between the waveguide end face of the end face-coupled silicon photonic chip 501, the waveguide end face of the end face-emitting silicon photonic waveguide 709, and the waveguide port 102 of the coupling end face of the silicon photonic chip.

[0078] Optical matching adhesive 708 has refractive index matching capabilities, which can further reduce insertion loss and return loss in the optical path. For example, in one specific embodiment, the optical matching adhesive 708 has a hardness of 20D (Shore hardness) and a refractive index of n=1.43 (wavelength 1310nm).

[0079] It should be noted that the glass material of the first optical path adapter chip 1 is compatible with the coefficient of thermal expansion (CTE) of the TGV substrate 703, and can be directly bonded to the TGV substrate 703, with high bonding reliability and the ability to withstand the high temperature test of the subsequent reflow soldering process.

[0080] Please see Figure 9 , Figure 9 This is a schematic diagram of the coupling and bonding process between an "end-to-bottom" light-in / out optical path adapter chip (i.e., the second optical path adapter chip 2) and a surface-coupled silicon photonics chip 502, provided in an embodiment of this application.

[0081] When the optical path adapter chip is the second optical path adapter chip 2, the semi-finished product with the guide pin 4 fixed in the coupling hole 104 continues to be actively coupled and aligned with the surface-coupled silicon photonic chip 502's surface-emitting silicon photonic waveguide 1002. This coupling also only needs to couple the two outermost fiber channels 303, while the middle fiber channel 303 is guaranteed by the material precision design.

[0082] The waveguides on both sides of the surface-coupled silicon photonic chip 502 can be either input or output waveguides, and the coupling method is similar to that of the aforementioned end-face coupled scheme. For example, the surface-output silicon photonic waveguide 1002 of the surface-coupled silicon photonic chip 502 adopts a grating coupler structure with a coupling angle of 8°, which matches the 82° angle between the bottom waveguide port 202 of the silicon photonic chip coupling surface and the bottom surface of the chip, thereby achieving efficient optical path coupling.

[0083] After coupling is complete, the second optical path adapter chip 2, coupled to the optimal position, is directly fixed to the upper surface of the surface-coupled silicon photonic chip 502 using UV optical matching adhesive 1003. The UV optical matching adhesive 1003 has the dual functions of bonding and fixing as well as refractive index matching. Refractive index matching can further reduce the insertion loss and return loss of the optical path.

[0084] For example, in one specific embodiment, the UV optical matching adhesive 1003 is cured by UV, the bonding strength meets the MIL-STD-883E shear strength standard, the refractive index is n=1.43, and the center wavelength is 1310nm.

[0085] Remove the optical fiber array sample 3, leaving the guide pin 4 on the optical path adapter chip for plugging and unplugging connection with the external optical fiber array.

[0086] Specifically, after the optical path coupling between the optical path adapter chip and the silicon photonics chip is solidified, the fiber array gold sample 3 is pulled out from the guide pin 4. After being pulled out, the guide pin 4 remains in the coupling hole 104 of the optical path adapter chip, and the part of the guide pin 4 extending out of the glass substrate body is used for detachable plug-in connection with the external fiber array.

[0087] Understandably, the fiber array gold sample 3 can be used repeatedly as an auxiliary positioning tool for the coupling and positioning of guide pins in other optical engines, thereby effectively reducing production costs.

[0088] Based on the aforementioned encapsulation method embodiments, this application also provides a CPO optical engine, which is prepared using the encapsulation method described in any of the above embodiments.

[0089] The CPO optical engine includes a packaging substrate 1004, a driving electrical chip 702, a silicon photonics chip, and an optical path conversion chip. The driving electrical chip 702 is disposed on the packaging substrate 1004 and electrically connected to the packaging substrate 1004. The silicon photonics chip is electrically connected to the driving electrical chip 702. The optical path conversion chip includes a glass substrate body prepared by a glass substrate and multiple mode-conversion optical waveguides formed inside the glass substrate body. The first waveguide port of the mode-conversion optical waveguide is coupled to the optical waveguide of the silicon photonic chip. Multiple guide pins 4 are fixed in the coupling hole 104 of the optical path conversion chip and extend out of the glass substrate body for detachable plug-in connection with an external fiber array.

[0090] In one embodiment of this application, please refer to Figure 7 and Figure 8 , Figure 7 This is a schematic diagram of a detachable CPO optical engine for an end-coupled fiber array provided in an embodiment of this application. Figure 8This is a schematic diagram of a switch architecture based on a detachable CPO optical engine of an end-face coupled fiber array, provided for an embodiment of this application.

[0091] In this embodiment, the optical path adapter chip is specifically the first optical path adapter chip 1, and the packaging substrate 1004 is specifically the TGV substrate 703. When the silicon photonics chip is an end-coupled silicon photonics chip 501, the end-coupled silicon photonics chip 501 is electrically connected to the driving electrical chip 702 through the hybrid bonding pad 704, the driving electrical chip 702 is electrically connected to the TGV substrate 703 through the BGA solder joint 705, and the TGV substrate 703 is mechanically assembled and electrically connected to the switch motherboard 802 through the contact pad 706.

[0092] The length of the high-frequency trace between the optical engine and the 801 switch chip is less than 50mm.

[0093] For example, in one specific embodiment, the hybrid bonding pad 704 has a size of 30 μm, the pad feature size of the BGA solder joint 705 is 50 μm, the contact pad 706 has a size of 100 μm, and the length of the high-frequency trace between the optical engine and the switch chip 801 is 48 mm.

[0094] In another embodiment of this application, please refer to Figure 10 and Figure 11 , Figure 10 This is a schematic diagram of a detachable CPO optical engine for surface-coupled fiber arrays provided in an embodiment of this application. Figure 11 This is a schematic diagram of a switch architecture based on a detachable CPO optical engine of a surface-coupled fiber array, provided for an embodiment of this application.

[0095] In this embodiment, the optical path adapter chip is specifically the second optical path adapter chip 2. When the silicon photonics chip is a surface-coupled silicon photonics chip 502, the surface-coupled silicon photonics chip 502 is electrically connected to the driving electrical chip 702 through the hybrid bonding pad 704, and the driving electrical chip 702 is electrically connected to the packaging substrate 1004 through the BGA solder joint 705.

[0096] It should be noted that the material of the packaging substrate 1004 is not limited to the glass TGV substrate 703, but can also be other materials such as resin substrate, ceramic substrate, and silicon substrate. The packaging substrate 1004 is mechanically assembled and electrically connected to the switch motherboard 802 through contact pads 706. The length of the high-frequency trace between the optical engine and the switch chip 801 is less than 50mm.

[0097] Further, please refer to Figure 12 , Figure 12 This application provides a schematic diagram of the structure of an end-to-end optical path adapter chip for multi-core optical fibers, illustrating an embodiment of the present application. The structure of this optical path adapter chip is similar to... Figure 1 The first optical path adapter chip 1 shown is similar, except that: The waveguide distribution at the waveguide port 103 of the fiber coupling surface is changed from a linear array arrangement to a square distribution, forming a square waveguide end face 1201. With this distribution, the mainstream 4-core multi-core fiber (MCF) in the industry can be matched on the fiber side. Using multi-core fiber can improve the fiber output density of the CPO optical engine.

[0098] For example, in one specific embodiment, the spacing of the square-distributed waveguide end faces 1201 is 40μm ± 0.5μm, which can match mainstream Corning and Fujikura four-core MCF optical fibers. The coupling assembly method of this multi-core fiber-type optical path adapter chip is the same as described above. Figure 6 The process shown is similar and will not be repeated here.

[0099] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The above provides a detailed description of the packaging method and the CPO optical engine for a detachable optical fiber provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for packaging a fiber-optic detachable CPO optical engine, characterized in that, Includes the following steps: Obtain a gold sample of an optical fiber array with multiple guide pin holes and optical fiber channels, and insert multiple guide pins into the guide pin holes one by one. An optical path adapter chip prepared by a glass substrate is obtained, and multiple coupling holes are processed on the optical path adapter chip, wherein the diameter of the coupling hole is larger than the outer diameter of the guide pin; Insert the portion of the guide pin extending out of the guide pin hole into the coupling hole to achieve active coupling alignment between the fiber channel in the fiber array gold sample and the mode conversion waveguide. After alignment, inject adhesive into the coupling hole for curing to fix the guide pin into the coupling hole. Remove the optical fiber array sample, leaving the guide pin on the optical path adapter chip for plugging and unplugging connection with an external optical fiber array.

2. The packaging method according to claim 1, characterized in that, The diameter of the coupling hole is 20μm to 50μm larger than the outer diameter of the guide pin.

3. The packaging method according to claim 1, characterized in that, The optical path adapter chip has an end-face protection groove, and the waveguide port on one side of the mode conversion waveguide is located at the bottom of the end-face protection groove; and The depth of the end face protective groove is 2μm to 3μm.

4. The packaging method according to claim 3, characterized in that, The optical fiber array gold sample has an outwardly protruding limiting part formed on it. The active coupling alignment of the optical fiber channel in the optical fiber array gold sample with the mode-spot conversion optical waveguide includes the following steps: The limiting part extends into the end face protection groove and is fitted with the bottom of the end face protection groove with a gap. The limiting part is moved along the extension direction of the side wall of the end face protection groove until the optical fiber channel of the optical fiber array gold sample coincides with the mode conversion optical waveguide.

5. The packaging method according to claim 4, characterized in that, When the limiting part moves along the extension direction of the sidewall of the end face protection groove, the limiting part is fitted to the sidewall of the end face protection groove, so that the optical fiber channel and the mode conversion waveguide are on the same plane.

6. The packaging method according to claim 4, characterized in that, The optical fiber channel includes a first channel and a second channel located on the outermost side of the optical fiber array gold sample. The optical fiber channel extending to the optical fiber array gold sample coincides with the mode-spot conversion waveguide, and includes the following steps: Select the first and second channels as alignment channels; Optical signals are input into the optical fibers of the first channel and the second channel, and the first output optical power and the second output optical power are detected at the other end of the mode-spot conversion optical waveguides corresponding to the first channel and the second channel, respectively. Adjust the relative positions of the fiber array sample and the optical path adapter chip in a plane perpendicular to the optical axis until the first output optical power and the second output optical power reach their maximum values ​​simultaneously.

7. The packaging method according to claim 6, characterized in that, The waveguide spacing of each adjacent mode-spot conversion waveguide is equal to the channel spacing of each adjacent fiber channel in the fiber array gold sample, and the spacing deviation of adjacent mode-spot conversion waveguides is ≤0.5μm.

8. The packaging method according to claim 3, characterized in that, The bottom wall of the end face protection groove is covered with an anti-reflective membrane.

9. The packaging method according to claim 1, characterized in that, The optical path adapter chip has a dispensing window that connects to the coupling hole, and the adhesive is injected into the coupling hole through the dispensing window; and / or The curing shrinkage of the adhesive is in the nanometer range.

10. A CPO light engine, characterized in that, The CPO optical engine is prepared by the encapsulation method according to any one of claims 1-9, and comprises: Packaging substrate; A driving electrical chip is disposed on the packaging substrate and electrically connected to the packaging substrate; A silicon photonics chip is electrically connected to the driving electrical chip; An optical path conversion chip includes a glass substrate body prepared by a glass substrate and multiple mode-spot conversion optical waveguides formed inside the glass substrate body, wherein the first waveguide port of the mode-spot conversion optical waveguide is coupled to the optical waveguide of the silicon photonic chip. Multiple guide pins are fixed inside the coupling holes of the optical path adapter chip and extend out of the glass substrate body for detachable plug-in connection with an external fiber optic array.

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