Fiber coupling structure and fiber and chip welding method thereof

Abstract

The present invention discloses an optical fiber coupling structure and an optical fiber and chip welding method thereof, belonging to the technical field of optical fiber and wavelength division multiplexer chip coupling structure. The optical fiber coupling structure of the present invention includes a wavelength division multiplexer chip, a metal seat, an optical fiber holder, an optical fiber sleeve, a chip base, an optical fiber, and an optical fiber array; wherein the optical fiber holder and the chip base are placed on the upper surface of the metal seat, the optical fiber holder and the metal seat are connected by laser welding, a wavelength division multiplexer chip is arranged above the chip base, the opening of the optical fiber holder is directly opposite to the chip output end, the bottom of the optical fiber holder is against the bottom of the chip base, the optical fiber and the optical fiber sleeve are coaxially arranged, the optical fiber sleeve passes through the optical fiber holder to achieve positioning, and the optical fiber array is fixed to the chip base. The present invention fixes the optical fiber sleeve by laser welding to ensure that the optical fiber and the wavelength division multiplexer chip are aligned horizontally and vertically. Finally, the chip base is adjusted again, and the chip base is fixed by laser welding to achieve a stable and precise connection between the optical fiber and the wavelength division multiplexer chip.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber and wavelength division multiplexer chip coupling structures, and in particular to an optical fiber coupling structure and an optical fiber and chip welding method thereof. Background Art

[0002] Wavelength division multiplexing devices such as multimode interferometers, arrayed waveguide gratings, and Mach-Zehnder interferometers are indispensable components of optical fiber communication networks. In radio frequency photonic systems, the application demand for high-efficiency, high-power broadband wireless systems in the Sub15GHz golden spectrum will grow rapidly in the future. Breakthroughs in the technologies related to high-power, high-efficiency analog radio frequency fronthaul networks and microwave photonic core devices for photodetector direct-driven antennas will become particularly important. High input optical power requires a stable connection between the optical chip and the optical fiber, while high efficiency requires efficient coupling between the optical chip and the optical fiber to reduce losses. Conventional optical chips and optical fibers are coupled using a curing agent. As described in "Ranno, L., et al. (2022). "Integrated Photonics Packaging: Challenges and Opportunities." ACS Photonics 9(11): 3467-3485.", this method deteriorates the stability of the curing agent used to connect the optical fiber and the device under high power input, affecting the coupling quality and increasing the input loss. In severe cases, the optical chip will be damaged and unable to work properly. Most research on fiber coupling focuses on the coupling of lasers and optical fibers, such as the solution disclosed in the patent application with the publication number CN108879318A and the invention name "A semiconductor laser packaging structure and its welding method". Another example is the free-light-emitting packaged laser introduced in the document "Yi-Cheng, H., et al. (2005). "A novel fiber alignment shift measurement and correction technique in laser-welded laser module packaging." Journal of Lightwave Technology 23(2):486-494." Due to the working characteristics of the laser, the optical chip and the optical fiber only need single-end coupling, which is less difficult than the wavelength division multiplexer that needs to couple the input and output two end faces. On the other hand, as the miniaturization of the device makes coupling more difficult, the input / output coupling technology of passive optical chips such as precision optical fiber and wavelength division multiplexer can reduce the insertion loss of optical devices. While some approaches, such as those proposed in patent application publication number CN103323919A, entitled "Optical Assembly for Precisely Aligning Optical Components with Fibers," can achieve precise alignment of optical components and optical fibers, the process is complex and the coupling requires specialized equipment, making it difficult to operate. Therefore, a new chip-to-fiber coupling method specifically for wavelength division multiplexing devices with a simple structure and ease of operation is needed. Summary of the Invention

[0003] The purpose of the present invention is to provide a coupling structure and coupling method for an optical fiber and a wavelength division multiplexer chip with low loss, stable coupling, and high coupling accuracy in high power input application scenarios based on actual needs.

[0004] In one aspect, the present invention discloses a fiber coupling structure comprising a metal seat, a fiber holder, a fiber sleeve, a chip base, a wavelength division multiplexer chip, an optical fiber, and an optical fiber array;

[0005] The optical fiber holder and the chip base are placed on the upper surface of the metal base. Both the optical fiber holder and the chip base are in a "X" shape and are fixed to the upper surface of the metal base through the bottom of the optical fiber holder and the bottom of the chip base respectively. The height of the optical fiber holder is greater than the height of the chip base. A wavelength division multiplexer chip is arranged above the chip base.

[0006] The optical fiber and the optical fiber sleeve are coaxially arranged, and the inner diameter of the optical fiber sleeve is not less than the outer diameter of the optical fiber. The optical fiber sleeve passes through the optical fiber holder to face the wavelength division multiplexer chip, and the optical fiber sleeve located in the optical fiber holder is fixedly connected to the optical fiber holder;

[0007] The chip input end of the wavelength division multiplexer chip is connected to the optical fiber array fixed on the chip base, and the chip output end of the wavelength division multiplexer chip is connected to the optical fiber in the optical fiber sleeve passing through the optical fiber holder.

[0008] Furthermore, the chip base upper surface size is larger than the chip size of the wavelength division multiplexer chip, the chip output end face of the wavelength division multiplexer chip is flush with the edge of the chip base upper surface, and the two sides of the wavelength division multiplexer chip are equidistant from the two edges of the chip base upper surface.

[0009] Furthermore, the connection between the optical fiber and the optical fiber array and the wavelength division multiplexer chip can be swapped, so that the opening of the optical fiber holder is opposite to the chip input end face of the wavelength division multiplexer chip. The chip input end of the wavelength division multiplexer chip is used to connect to the optical fiber passing through the optical fiber holder, and the chip output end of the wavelength division multiplexer chip is used to connect to the optical fiber array.

[0010] Furthermore, the length of the upper surface of the chip base is 5 to 7 mm greater than the length of the chip.

[0011] Furthermore, the height of the optical fiber holder is 4 to 5 mm greater than the height of the chip base.

[0012] Furthermore, the metal base, the optical fiber holder, the optical fiber sleeve and the chip base are all made of var alloy.

[0013] Furthermore, windows are provided on the side surfaces of the chip base and / or the extended surface of the side surface located on the upper surface of the metal base, so as to increase and adjust the soldering points and increase the soldering adjustment dimension.

[0014] Furthermore, the side surface of the chip base is in an "X" shape, and two groups of welding fixing points are respectively provided on the left and right sides of the "X"-shaped side surface to weld the chip base to the upper surface of the metal base.

[0015] On the other hand, the present invention also discloses a method for welding an optical fiber and a chip used in the optical fiber coupling structure of the present invention, which comprises the following steps:

[0016] A) Mount the wavelength division multiplexer chip on the chip base;

[0017] B) trimming the optical fiber connector so that the optical fiber connector does not exceed the limited length of the optical fiber cladding, which is 1 to 5 mm;

[0018] C) Use a curing agent to permanently connect the optical fiber and the optical fiber sleeve;

[0019] D) Fixing the optical fiber holder to the metal base by laser welding;

[0020] E) Using a fixture, press the chip base against the fiber holder. Using a precision adjuster, insert the fiber sleeve through the fiber holder. Using a microscope, observe the lateral distance between the fiber and the output end of the WDM chip. Adjust the position of the chip base. When the optical axis of the fiber is aligned with the chip output waveguide, press down on the WDM chip mounted on the chip base to temporarily secure it.

[0021] F) Connect the other end of the optical fiber to the laser and place the near-infrared imaging microscope at the input end face of the wavelength division multiplexer chip;

[0022] G) Turn on the laser, observe the output through a near-infrared imaging microscope, adjust the position of the fiber ferrule, and when a light spot appears on the output channel of the wavelength division multiplexer chip, use two symmetrical laser beams to weld the fiber ferrule to the fiber holder to achieve a permanent connection between the fiber ferrule and the fiber holder;

[0023] H) releasing the pressure on the WDM chip and adjusting the chip base by observing the output of the near-infrared imaging microscope. When the near-infrared microscope imaging shows the emission channel spot, press down the temporarily fixed WDM chip;

[0024] 1) Connect the fiber array to the optical power meter and use a precision adjuster to clamp the fiber array. When the output optical power is maximum, fix the fiber array to the wavelength division multiplexer chip.

[0025] J) Two symmetrical laser beams are used to laser weld the chip base to the metal base, relieving the pressure on the WDM chip.

[0026] Furthermore, if light loss occurs, the chip base is adjusted using adjustment soldering to find the best coupling position.

[0027] Since the wavelength division multiplexer is a passive optical device and light waves can propagate in both directions, the optical fiber and chip welding method of the present invention is also applicable to the coupling of wavelength division multiplexer and optical fiber with optical fiber as input end and optical fiber array as output end.

[0028] Furthermore, in step D), when the optical fiber holder is fixed to the metal base by laser welding, spot welds are simultaneously performed on both sides of the bottom of the optical fiber holder to ensure that the optical fiber holder is not offset perpendicular to the axis of the optical fiber. After the front pair of welding points are fixed, the rear pair are fixed.

[0029] Furthermore, in step G), when the optical fiber sleeve is fixed to the optical fiber holder by laser welding, spot welding is performed on both sides of the opening of the optical fiber holder at the same time to ensure that the optical fiber holder is not offset in the direction perpendicular to the axis of the optical fiber. After fixing the front pair of welding points, the rear pair is fixed.

[0030] When the output channel of the wavelength division multiplexer chip shows a light spot, two symmetrical laser beams are used to weld the optical fiber sleeve and the optical fiber holder to achieve a permanent connection between the optical fiber sleeve and the optical fiber holder;

[0031] The technical solution provided by the present invention brings at least the following beneficial effects:

[0032] Compared with the existing coupling structure, the fiber coupling structure of the present application first adjusts the lateral position of the chip base after fixing the fiber holder to achieve rough alignment in the horizontal direction, and then adjusts the height of the fiber sleeve in the fiber holder to achieve fine alignment between the fiber and the chip. Since the fiber sleeve undergoes thermal deformation and offset after cooling after laser welding, the coupling efficiency will decrease. After the fiber is partially fixed, it is necessary to adjust the chip base again to achieve additional dimensional adjustment. The fiber and chip welding method provided by the present invention enables the obtained fiber coupling structure to achieve efficient docking between the chip and the fiber array by simply adjusting the fiber array after the fiber is fixed. Compared with the fiber holder, the chip base is larger in size, and the chip offset after laser welding is smaller. The use of symmetrical laser welding, combined with the restriction of the chip base by the coupling structure, can effectively prevent displacement during the base welding process. In addition, after the chip base and the fiber sleeve are laser welded, the adjustment weld can be used to adjust the offset caused by deformation for a second time, which can achieve higher precision adjustment than that of the input fiber by laser welding alone. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 This is a schematic diagram of the optical fiber coupling structure of this application.

[0035] Figure 2 This is a top view of the optical fiber holder of this application.

[0036] Figure 3 This is a schematic diagram of the laser welding portion of the optical fiber sleeve and optical fiber holder of the optical fiber coupling structure of this application.

[0037] Figure 4 This is a schematic diagram of the fiber-coupled structure chip base of this application.

[0038] Figure 1: 1. chip base; 2. optical fiber holder; 3. optical fiber sleeve; 4. metal base; 5. wavelength division multiplexer chip; 6. optical fiber; 7. optical fiber array; 11 and 12 are different pairs of fixing points on the chip base for welding the metal base, 21 and 22 are different pairs of fixing points on the optical fiber holder for welding the metal base, and 23 and 24 are different pairs of fixing points on the optical fiber holder for welding the optical fiber sleeve. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in detail and completely in conjunction with the drawings in the implementation of the present invention. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings can be arranged and designed using different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present invention.

[0040] like Figure 1As shown, the fiber coupling structure of the present application includes a metal base 4, a fiber holder 2, a fiber sleeve 3, a chip base 1, a wavelength division multiplexer chip 5, an optical fiber 6, and a fiber array 7. The fiber holder 2 and the chip base 1 are each fixedly connected to the upper surface of the metal base 4 via their bottoms, and the height of the fiber holder 2 is greater than that of the chip base 1. Preferably, in this embodiment, the bottoms of the fiber holder 2 and the chip base 1 are each welded to the upper surface of the metal base 4. A wavelength division multiplexing (WDM) chip 5 is disposed above the chip base 1. The opening of the optical fiber holder 2 faces the chip output end face of the WDM chip 5. An optical fiber 6 is coaxially disposed with an optical fiber sleeve 3, and the inner diameter of the optical fiber sleeve 3 is not less than the outer diameter of the optical fiber 1. The optical fiber sleeve 3 passes through the optical fiber holder 2 to face the WDM chip 5, and the optical fiber sleeve 3 located within the optical fiber holder 2 is fixedly connected to the optical fiber holder 2. The chip input end of the WDM chip 5 is connected to the optical fiber array 7 fixed to the chip base 1, and the chip output end of the WDM chip 5 is connected to the optical fiber 6 in the optical fiber sleeve 3 passing through the optical fiber holder 2. Preferably, the top surface of the chip base 1 is larger than the chip size of the WDM chip 5, the chip output end face of the WDM chip 5 is flush with the edge of the top surface of the chip base 1, and the two sides of the WDM chip 5 are equidistant from the two edges of the top surface of the chip base 1. In addition, in the specific implementation, the metal seat 4, the optical fiber holder 2, the optical fiber sleeve 3, and the chip base 1 are all made of Kovar alloy. Kovar alloy is easy to weld, has strong thermal conductivity and a small thermal expansion coefficient, and can reduce positional deviation after laser welding.

[0041] The present application provides a method for welding an optical fiber and a chip for the above-mentioned optical fiber coupling structure, comprising the following steps:

[0042] Mount the wavelength division multiplexer chip 5 on the chip base 1. When mounting, ensure that the chip output end surface of the wavelength division multiplexer chip 5 is flush with the upper edge of the chip base 1, and that both sides of the wavelength division multiplexer chip 5 are equidistant from the two edges of the chip base 1.

[0043] After trimming the fiber optic connector, the optical fiber 6 is inserted into the optical fiber sleeve 3 and fixed with a curing agent;

[0044] The optical fiber holder 2 is fixed to the metal base 4 by laser welding, as shown in FIG. Figure 2 As shown, two symmetrical laser beams are used to first weld the fixed point pair 21 and then the fixed point pair 22;

[0045] Use a clamp to press the chip base 1 against the fiber holder 2 to prevent the chip base 1 from moving in the axial direction of the optical fiber. Use a precision adjuster to pass the optical fiber sleeve 3 through the optical fiber holder 2. Use a microscope to observe the lateral distance between the optical fiber 6 and the chip output end face of the wavelength division multiplexer chip 5. Keep the chip base 1 against the fiber holder 2 while adjusting the position of the chip base 1. When the optical axis of the optical fiber 6 is aligned with the output waveguide of the wavelength division multiplexer chip 5, press down on the wavelength division multiplexer chip 5 mounted on the chip base 1 to temporarily fix it and prevent lateral distance deviation.

[0046] Connect the other end of the optical fiber 6 to the laser, place the near-infrared imaging microscope on the chip input end face of the wavelength division multiplexer chip 5, then turn on the laser, observe the output status through the near-infrared imaging microscope, adjust the position of the optical fiber sleeve 3, and when the output channel of the wavelength division multiplexer chip 5 shows a light spot, use two symmetrical laser beams to weld the optical fiber sleeve 3 to the optical fiber holder 2 permanently, as shown in the figure. Figure 3 As shown, first weld the two fixing points 23 and then weld the two fixing points 24. Using a symmetrical laser can effectively suppress the horizontal movement of the optical sleeve 3, reducing the difficulty of subsequent adjustments. After fixing the optical fiber holder 2 and the optical sleeve 3, release the clamp.

[0047] The next step is to align the WDM chip 5 and the fiber array 7. First, release the pressure on the WDM chip 5 and adjust the chip base 1 by observing the output of the near-infrared imaging microscope. When the near-infrared microscope imaging shows the emission channel light spot, press down on the temporarily fixed WDM chip 55 to ensure that the input laser signal can complete the alignment at the chip input end. Connect one end of the fiber array 7 to the optical power meter and use a precision adjuster to clamp the fiber array 7. When the output optical power is maximum, fix the fiber array 7 to the WDM chip 5. By fixing the chip base 1 and adjusting the position of the fiber array 7, the coupling efficiency from the output end of the WDM chip 5 to the fiber array 7 can be improved.

[0048] After the optical fiber array 7 is fixed on the chip base 1, the relative position of the chip base 1 and the optical fiber holder 2 is adjusted again to the maximum output optical power, and the chip base 1 is laser welded to the metal base 4 using two symmetrical laser beams. Figure 4 As shown, welding is performed first at fixing point 11 and then at fixing point 12. Because the chip base is larger than the fiber holder, chip offset after laser welding is minimized, allowing for more precise correction of post-laser weld offset during subsequent adjustment welding. Because both adjustments utilize symmetrical lasers, the horizontal relative displacement between fiber 6 and WDM chip 5 is significantly reduced. Therefore, the fiber sleeve only needs to be adjusted vertically through adjustment welding, simplifying adjustment and improving alignment accuracy.

[0049] In this application, the optical fiber holder 2 and the chip base 1 are placed on the upper surface of the metal base 4. The optical fiber holder 2 and the metal base 4 are connected by laser welding. A wavelength division multiplexer chip 5 is arranged above the chip base 1. The opening of the optical fiber holder 2 is directly opposite to the chip output end face of the wavelength division multiplexer chip 5. The bottom of the optical fiber holder 2 is against the bottom of the chip base 1. The optical fiber 6 is coaxially arranged with the optical fiber sleeve 3. The optical fiber sleeve 3 passes through the optical fiber holder 2 to achieve position limiting. The optical fiber array 7 is fixed to the chip base 1. The optical fiber sleeve 3 is fixed by laser welding to ensure the horizontal and vertical alignment of the optical fiber 6 and the wavelength division multiplexer chip 5. Finally, the chip base 1 is adjusted again and fixed by laser welding to achieve a stable and precise connection between the optical fiber 6 and the wavelength division multiplexer chip 5.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

[0051] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A fiber coupling structure comprising a metal base, a fiber holder, a fiber sleeve, a chip base, a wavelength division multiplexer chip, an optical fiber, and an optical fiber array, characterized in that: The optical fiber holder and the chip base are placed on the upper surface of the metal base. Both the optical fiber holder and the chip base are in a "X" shape and are fixed to the upper surface of the metal base by the bottom of the optical fiber holder and the bottom of the chip base, respectively. The height of the optical fiber holder is greater than the height of the chip base. A wavelength division multiplexer chip is disposed above the chip base. The opening of the optical fiber holder is directly opposite the chip output end face of the wavelength division multiplexer chip. The length of the bottom of the chip base is greater than the length of the top of the chip base, and the bottom of the optical fiber holder abuts against the bottom of the chip base. The optical fiber and the optical fiber sleeve are coaxially arranged, and the inner diameter of the optical fiber sleeve is not less than the outer diameter of the optical fiber. The optical fiber sleeve passes through the optical fiber holder to face the wavelength division multiplexer chip, and the optical fiber sleeve located in the optical fiber holder is fixedly connected to the optical fiber holder. The chip input end of the wavelength division multiplexer chip is connected to the optical fiber array fixed to the chip base, and the chip output end of the wavelength division multiplexer chip is connected to the optical fiber in the optical fiber sleeve passing through the optical fiber holder. The size of the chip base's upper surface is larger than that of the wavelength division multiplexer chip, the chip output end face of the wavelength division multiplexer chip is flush with the edge of the chip base's upper surface, and the distances between the two sides of the wavelength division multiplexer chip and the two edges of the chip base's upper surface are equal; the length of the chip base's upper surface is 5 to 7 mm longer than the chip length; and the height of the optical fiber holder is 4 to 5 mm longer than the height of the chip base. Reverse the connection between the optical fiber and the optical fiber array and the wavelength division multiplexer chip, so that the opening of the optical fiber holder is directly opposite to the chip input end face of the wavelength division multiplexer chip. The chip input end of the wavelength division multiplexer chip is used to connect to the optical fiber passing through the optical fiber holder, and the chip output end of the wavelength division multiplexer chip is used to connect to the optical fiber array; A pair of welding fixing points are respectively provided at both ends of the opening of the optical fiber holder for welding the optical fiber sleeve located in the optical fiber holder.

2. The optical fiber coupling structure according to claim 1, wherein: The metal base, fiber holder, fiber sleeve and chip base are all made of Kovar alloy.

3. The optical fiber coupling structure according to claim 1, wherein: Windows are provided on the side surface of the chip base and / or the extended surface of the side surface located on the upper surface of the metal base.

4. The optical fiber coupling structure according to claim 1, wherein: The side surface of the chip base is in an "X" shape, and a welding fixing point is respectively provided on the left and right sides of the "X"-shaped side surface to weld the chip base to the upper surface of the metal base.

5. A method for welding an optical fiber and a chip for the optical fiber coupling structure according to any one of claims 1 to 4, characterized in that: The steps include: A) Mount the wavelength division multiplexer chip on the chip base; B) trimming the optical fiber connector so that the optical fiber connector does not exceed the limited length of the optical fiber cladding, which is 1 to 5 mm; C) Using a curing agent to connect the optical fiber and the optical fiber sleeve; D) Fixing the optical fiber holder to the metal base by laser welding; E) Using a fixture, press the chip base against the fiber holder. Using a precision adjuster, insert the fiber sleeve through the fiber holder. Using a microscope, observe the lateral distance between the fiber and the output end of the WDM chip. Adjust the position of the chip base. When the optical axis of the fiber is aligned with the chip output waveguide, press down on the WDM chip mounted on the chip base to temporarily secure it. F) Connect one end of the optical fiber to the laser and place the near-infrared imaging microscope at the input end face of the wavelength division multiplexer chip; G) Turn on the laser, observe the output through a near-infrared imaging microscope, adjust the position of the fiber sleeve, and when a light spot appears on the output channel of the wavelength division multiplexer chip, use two symmetrical laser beams to weld the fiber sleeve to the fiber holder; H) releasing the pressure on the WDM chip and adjusting the chip base by observing the output of the near-infrared imaging microscope. When the near-infrared microscope imaging shows the emission channel spot, press down the temporarily fixed WDM chip; 1) Connect the fiber array to the optical power meter and use a precision adjuster to clamp the fiber array. When the output optical power is maximum, fix the fiber array to the wavelength division multiplexer chip. J) Two symmetrical laser beams are used to laser weld the chip base to the metal base, relieving the pressure on the WDM chip.

Images