Shockproof Space Light Receiving Device Based on Novel Fiber Collimator

Abstract

This invention discloses a shockproof spatial light receiving device based on a novel fiber optic collimator, comprising: a femtosecond pulse light source, a reflector, a three-dimensional electrically controlled displacement adjustment module, a fixture, a novel fiber optic collimator, and a power detector. The novel fiber optic collimator is obtained by cascading and encapsulating a collimating lens and fiber optic devices. The fiber optic devices include: a multimode-to-single-mode fiber directional coupler, a multi-core-to-single-mode fiber directional coupler, and a tapered multi-core-expanded single-mode fiber cascade. The femtosecond pulse light source emits spatial light, which is reflected by the reflector and enters the three-dimensional electrically controlled displacement adjustment module for calibration and coupling. The received spatial light is then sent to the novel fiber optic collimator on the fixture, where it is coupled into the single-mode fiber with a high coupling ratio. Finally, the power detector records the output power of the spatial light. This invention can couple spatial light into three different fiber optic devices, achieving a high coupling ratio optical power at the single-mode output end, and also exhibits certain anti-perturbation performance.

Description

Technical Field

[0001] This invention belongs to the field of spatial light to fiber optic receiving device coupling technology, and in particular relates to a shockproof spatial light receiving device based on a novel fiber optic collimator. Background Technology

[0002] Currently, devices used for space light reception on the market mainly employ three methods: free-space optical coupling based on a single lens, spatial optical coupling based on a fiber optic ball lens, and spatial optical coupling based on a tapered fiber. The tapered coupling method typically involves fused-tapered multimode fiber until its mode field diameter matches that of a single-mode fiber, then using quartz powder to bond the tapered region of the multimode fiber to the single-mode fiber. This fused connection is followed by side polishing to obtain a tapered fiber receiver. Due to the large core diameter of the multimode fiber, this method offers good shock resistance.

[0003] For the existing space light receiving technologies, although the single-mode fiber coupling technology based on lenses can achieve a coupling efficiency of about 90%, its vibration resistance is not strong. Even a small deviation of the beam will cause a sharp drop in coupling efficiency. It can only be used in static environments and cannot be applied to environments with micro-vibrations, such as satellite receiving platforms. In addition, the fabrication of spherical lenses on the fiber end face has high process requirements and is difficult to operate.

[0004] The improved fiber optic coupling device with a tapered section fuses a segment of fused-tapered multimode fiber to the end face of a single-mode fiber. The large core diameter of the multimode fiber allows for high-quality coupling efficiency while ensuring the shock resistance of the space optical receiving system. Furthermore, the tapering process degrades higher-order modes in the multimode fiber into fundamental modes for transmission to the single-mode fiber. However, this receiving device has a complex manufacturing process, and the mismatch between the tapered cladding of the multimode fiber and the single-mode fiber increases the difficulty of fusion splicing and may increase insertion loss at the splice. Additionally, the sides of the tapered section require polishing, which is time-consuming. Summary of the Invention

[0005] The purpose of this invention is to provide a shockproof spatial light receiving device based on a novel fiber optic collimator to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides a shockproof spatial light receiving device based on a novel fiber optic collimator, comprising: a femtosecond pulse light source, a reflector, a three-dimensional electrically controlled displacement adjustment module, a fixture, a novel fiber optic collimator, and a power detector; wherein, the novel fiber optic collimator is obtained by cascading and encapsulating a collimating lens and fiber optic devices, and the fiber optic devices include: a multimode-single-mode fiber directional coupler, a multicore-single-mode fiber directional coupler, and a tapered multicore-expanded single-mode fiber cascade;

[0007] The femtosecond pulse light source emits spatial light, which is reflected by the mirror and enters the three-dimensional electrically controlled displacement adjustment module to calibrate and couple the spatial light. Then, it is sent to the novel fiber collimator on the fixture to couple the received spatial light into the single-mode fiber with a high coupling ratio. Finally, the output power of the spatial light is recorded based on the power detector.

[0008] Optionally, the reflector includes a first reflector and a second reflector. By adjusting the pitch angle and azimuth angle of the first and second reflectors, spatial light can be collimated and coupled into the novel fiber optic collimator.

[0009] Optionally, the three-dimensional electrically controlled displacement adjustment module includes a three-dimensional displacement adjustment frame and an open-loop piezoelectric controller;

[0010] The open-loop piezoelectric controller is used to quantitatively move the three-dimensional displacement adjustment frame by adjusting the open-loop voltage, so that spatial light can be collimated and coupled into the novel fiber collimator.

[0011] Optionally, the fabrication process of the novel fiber collimator includes: combining the multimode-single-mode fiber directional coupler, the multicore-single-mode fiber directional coupler, and the tapered multicore-expanded single-mode fiber cascade into a fiber optic device; covering the input end of the fiber optic device with a capillary tube for heating and fixing; and inserting it together with the collimating lens into a glass sleeve for curing treatment to complete the fabrication of the novel fiber collimator.

[0012] Optionally, the fabrication process of the multimode-single-mode fiber directional coupler includes: pre-tapering the multimode fiber using a tapering machine; stopping tapering when the diameter of the tapered region of the multimode fiber reaches a preset size that satisfies the phase matching condition; then knotting and fusion tapering the single-mode fiber and the tapered multimode fiber; stopping tapering when the output power of the single-mode fiber reaches the maximum coupling ratio; placing the processed fiber and coupler into a glass U-groove to complete curing; and finally covering it with a heat-shrink tubing to complete the fabrication of the multimode-single-mode fiber directional coupler.

[0013] Optionally, the fabrication process of the multi-core-single-mode fiber directional coupler includes: tapering the multi-core fiber using a tapering machine; stopping tapering when the diameter of the tapered region of the multi-core fiber reaches a preset size that satisfies the phase matching condition; knotting and fusion tapering the single-mode fiber and the tapered multi-core fiber; stopping tapering when the output power of the single-mode fiber reaches the maximum coupling ratio; placing the processed fiber and coupler into a glass U-groove to complete curing; and finally covering it with a heat-shrink tubing to complete the fabrication of the multi-core-single-mode fiber directional coupler.

[0014] Optionally, the fabrication process of the tapered multi-core-single-mode fiber cascade includes: tapering the multi-core fiber using a tapering machine; stopping tapering when the fiber core array is fused into a single fiber core and the cladding diameter of the tapered region of the fiber core is equal to the cladding diameter of the single-mode fiber; heating and expanding the single-mode fiber using a tapering machine; stopping heating when the core diameter of the single-mode fiber matches the core diameter of the tapered region of the multi-core fiber; fusion splicing the two fibers after the treatment using a fusion splicer; and finally, applying a heat-shrink tubing at the melting point to complete the fabrication of the tapered multi-core-single-mode fiber cascade.

[0015] The technical effects of this invention are as follows:

[0016] The three fiber optic devices in this invention can couple light from multimode fiber and multicore fiber into single-mode fiber with high coupling efficiency. Thus, by simply coupling spatial light into the multimode input end and multicore input end of the three fiber optic devices, high coupling ratio optical power can be obtained at the single-mode output end.

[0017] All three types of fiber optic devices exhibit excellent shock resistance. The multimode-to-single-mode fiber directional coupler utilizes the large core diameter of the multimode fiber at its multimode input end, maintaining high coupling efficiency even in environments with some vibration. Similarly, the multimode input ends of the multi-core to single-mode fiber directional coupler and the tapered multi-core fiber-expanded single-mode fiber cascade utilize the advantages of multi-core fiber arrays, maintaining good coupling efficiency even in environments with some vibration. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0019] Figure 1 This is a schematic diagram of the anti-vibration spatial light receiving device based on a novel fiber optic collimator in an embodiment of the present invention; wherein, 1-femtosecond pulse light source, 2-reflector, 2.1-first reflector, 2.2-second reflector, 3-three-dimensional displacement adjustment frame, 4-clamp, 5-open-loop piezoelectric controller, 6-novel fiber optic collimator, 7-power detector;

[0020] Figure 2 This is a partial enlarged view of the packaged multimode-single-mode fiber directional coupler in an embodiment of the present invention; wherein, 611-multimode input end, 612-single-mode input end, 613-multimode output end, 614-single-mode output end, 615-glass U-groove, 616-heat shrink tubing;

[0021] Figure 3This is a partial enlarged view of the packaged multi-core to single-mode fiber directional coupler in an embodiment of the present invention; wherein, 621-multi-core input end, 622-single-mode input end, 623-multi-core output end, 624-single-mode output end, 625-glass U-groove, 626-heat shrink tubing;

[0022] Figure 4 This is a partially enlarged view of the packaged tapered multi-core-expanded single-mode fiber cascade device according to an embodiment of the present invention; wherein, 631-multi-core fiber, 631.1-multi-core input cladding, 631.2-multi-core tapered cladding, 631.3-multi-core tapered fiber core, 632-single-mode fiber, 632.1-single-mode output cladding, 632.2-single-mode expanded cladding, 632.3-single-mode expanded fiber core, 632.4-single-mode output fiber core, 633-heat shrink tubing;

[0023] Figure 5 This is a partial enlarged view of the novel fiber collimator in an embodiment of the present invention; wherein, 641 - the fabricated fiber device, 642 - the glass sleeve, 643 - the capillary tube, and 644 - the collimating lens. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0026] Example 1

[0027] like Figure 1As shown, this embodiment provides a shockproof space light receiving system device based on a novel fiber optic collimator. The device includes: a femtosecond pulse light source 1, a reflector 2, a clamp 4, a three-dimensional electrically controlled displacement adjustment module, a novel fiber optic collimator 6, and a power detector 7. The three-dimensional electrically controlled displacement adjustment module consists of a three-dimensional displacement adjustment frame 3 and an open-loop piezoelectric controller 5, used to calibrate the coupling optical path. The novel fiber optic collimator 6 is the core component of the receiving system, composed of a collimating lens and cascaded fiber optic devices. These fiber optic devices include three types: multimode-single-mode fiber directional couplers, multi-core-single-mode fiber directional couplers, and tapered multi-core-expanded single-mode fiber cascades. Multimode-to-single-mode fiber directional couplers and multicore-to-single-mode fiber directional couplers are respectively made by fused tapering of multimode and single-mode fibers, and multicore and single-mode fibers: First, the multimode and multicore fibers are pre-stretched, where the tapered core arrays of the multicore fibers need to be brought close together to form a single core. Then, the pre-stretched fibers are knotted with single-mode fibers and fused tapered to obtain the multimode-to-single-mode fiber directional coupler and the multicore-to-single-mode fiber directional coupler, respectively. Tapered multicore-expanded single-mode fiber cascades are made by combining multicore and single-mode fibers: ... The output end of the multi-core fiber is fused and tapered. When the core array of the taper region approaches each other to become a single core and the cladding diameter is equal to the cladding diameter of the ordinary single-mode fiber, the tapering is stopped, the taper region is cut off, and the core diameter of the taper region is measured. Based on the measurement results, the single-mode fiber is expanded. When the core diameter of the single-mode fiber is equal to the core diameter of the taper region of the multi-core fiber, the expansion is stopped. Then, a fusion splicer is used to fuse the cut end of the multi-core fiber with the flattened end face and the flattened end face of the expanded single-mode fiber to obtain a tapered multi-core-expanded single-mode fiber cascade. After being focused by a collimating lens, spatial light is coupled into the input ends of three different fiber optic devices. Utilizing the high conversion efficiency and low insertion loss of multimode-to-single-mode fiber directional couplers and multi-core-to-single-mode fiber directional couplers, as well as the low insertion loss after large fusion splicing of the multi-core fiber taper region and the single-mode fiber expander region in the tapered multi-core-expanded single-mode fiber cascade, the received spatial light can be coupled into the single-mode fiber with a high coupling ratio. The large mode field area of ​​the multimode fiber and the multiple core arrays of the multi-core fiber can still receive the focused spatial light through the collimating lens even in environments with minor perturbations, allowing the spatial light to enter the single-mode fiber with high coupling efficiency. Finally, the optical power is received at the output end of the single-mode fiber. The overall device first requires optical path calibration, i.e., adjusting the pitch and azimuth angles of the two mirrors in the spatial optical path to ensure that the optical path at the femtosecond pulse source output end and the optical path at the receiving end of the novel fiber collimator are parallel and coplanar. Subsequently, the three-dimensional adjustment frame was adjusted so that the pulsed light could be coupled into the new fiber collimator. A power detector was used at the single-mode output end of the new fiber collimator to record the output power and thus calculate the coupling efficiency of the system. The optimal coupling efficiency was achieved by continuously iterating and fine-tuning the reflector and adjustment frame.Then, the environmental vibration was simulated by a three-dimensional electronically controlled displacement adjustment module. Based on the optimal coupling position, the offset of the three-dimensional adjustment frame in different directions was changed, and the coupling efficiency under different offsets was recorded. Through data fitting, the high-efficiency coupling and anti-vibration performance of the system device were characterized.

[0028] The overall structural diagram of the device is shown in the product plan. Figure 1 As shown. The laser emitted from the femtosecond pulse source 1 enters the novel fiber collimator 6, which is fixed on the clamp 4 of the three-dimensional displacement adjustment frame 3, after passing through the first reflector 2.1 and the second reflector 2.2. Before the laser enters the novel fiber collimator 6, the laser power is measured and kept constant as the total input power of the system. After being focused by the collimating lens at the incident end of the novel fiber collimator 6, the laser enters the fiber of the novel fiber collimator 6 and is output at the single-mode output end of the novel fiber collimator 6. The output power is monitored using a power detector 7. The optical path is calibrated by fine-tuning the first reflector 2.1, the second reflector 2.2, and the three-dimensional displacement adjustment frame 3 to achieve the optimal coupling state of the system. To test the anti-vibration performance of the system, the positions of the first reflector 2.1, the second reflector 2.2, and the three-dimensional displacement adjustment frame 3 at the optimal coupling state are set as the reference positions. The open-loop piezoelectric controller 5 is adjusted to quantitatively move the three-dimensional displacement adjustment frame 3 to adjust the offset of the novel fiber collimator 6. At the same time, the power detector 7 is used to monitor the output power of the novel fiber collimator 6 at different offsets.

[0029] Figure 2 This is a partially enlarged view of the fabricated and packaged multimode-to-single-mode fiber directional coupler. The multimode-to-single-mode fiber directional coupler is formed by drawing multimode fiber (including a multimode input end 611 and a multimode output end 613) and single-mode fiber (including a single-mode input end 612 and a single-mode output end 614). First, the multimode fiber is pre-drawn. Then, the single-mode fiber is knotted and fused with the pre-drawn tapered multimode fiber and drawn into a tapered shape. After successful drawing, the coupler is placed in a glass U-groove 615, and UV adhesive is applied to both ends of the glass U-groove 615. The coupler is then cured by irradiation with a UV lamp for approximately 20 seconds. Afterward, a heat-shrink tubing 616 is placed over the multimode-to-single-mode fiber directional coupler, and the coupler is heated in a high-temperature heating bath for approximately 1 minute before being removed, resulting in the finished multimode-to-single-mode fiber directional coupler.

[0030] Specifically: To fabricate a multimode-to-single-mode fiber directional coupler, first connect the multimode fiber to the light source and a tapering machine. Use wire strippers to remove a certain length of the coating from the multimode fiber, and then clean the area with high-concentration alcohol using lint-free paper before placing it on the tapering machine's fixture. Use an oxyhydrogen flame to pre-taper the multimode fiber, and monitor the power change at the multimode fiber's output end in real time. Next, take a certain length of single-mode fiber, similarly remove an appropriate length of coating, and clean it with high-concentration alcohol using lint-free paper. Then, align the areas of the multimode and single-mode fibers with the removed coatings, tie them together, and fix them back onto the tapering machine's fixture. Use an oxyhydrogen flame to melt-taper the knotted portion, again monitoring the single-mode fiber in real time. The output power is controlled, and tapering stops when the single-mode output reaches the maximum coupling ratio. Utilizing the tapering machine's encapsulation function, a multimode-to-single-mode fiber directional coupler is encapsulated using a glass U-groove, UV adhesive, heat shrink tubing, and steel pipe: The tapered section of the drawn multimode-to-single-mode fiber directional coupler is placed inside the glass U-groove. UV adhesive is dripped onto both ends of the glass U-groove and cured using a UV lamp. After curing, a section of heat shrink tubing is placed over the glass U-groove and heated in a high-temperature heating bath for about 1 minute. Finally, a steel pipe is placed over the heat shrink tubing, and UV adhesive is dripped onto both ends of the steel pipe and cured using a UV lamp. This yields the encapsulated multimode-to-single-mode fiber directional coupler.

[0031] Figure 3 This is a partially enlarged view of the fabricated and packaged multi-core to single-mode fiber directional coupler. The multi-core to single-mode fiber directional coupler is formed by drawing multi-core optical fibers (including a multi-core input end 621 and a multi-core output end 623) and single-mode optical fibers (including a single-mode input end 622 and a single-mode output end 624). First, the multi-core optical fibers are pre-drawn until the multi-core array is fused into a single fiber core. Then, the single-mode optical fiber is knotted and fused with the pre-drawn tapered multi-core optical fiber and drawn into a tapered shape. After successful drawing, the coupler is placed in a glass U-groove 625, and UV adhesive is dripped onto both ends of the glass U-groove 625. The coupler is then cured by irradiation with a UV lamp for approximately 20 seconds. Afterward, a heat-shrink tubing 626 is placed over the multi-core to single-mode fiber directional coupler, and the coupler is heated in a high-temperature heating bath for approximately one minute before being removed, resulting in the finished multi-core to single-mode fiber directional coupler.

[0032] Specifically: To fabricate a multi-core to single-mode fiber directional coupler, first connect the multi-core fiber to the light source and a tapering machine. Use wire strippers to remove a certain length of the coating from the multi-core fiber. Clean the stripped area with lint-free paper soaked in high-concentration alcohol, then place it on the tapering machine's fixture. Pre-taper the multi-core fiber using an oxyhydrogen flame, and monitor the power change at the multi-core fiber's output end in real time. Next, take a certain length of single-mode fiber, similarly remove an appropriate length of coating, and clean it with lint-free paper soaked in high-concentration alcohol. Then, align the stripped areas of the multi-core and single-mode fibers, knot them, and fix them back on the tapering machine's fixture. Use an oxyhydrogen flame to perform fusion tapering on the knotted portion, and monitor the single-mode fiber's power change in real time. Output power: Stop tapering when the single-mode output reaches the maximum coupling ratio. Utilize the packaging function of the tapering machine to package the multi-core-single-mode fiber directional coupler using a glass U-groove, UV glue, heat shrink tubing, and steel pipe: Place the tapered section of the drawn multi-core-single-mode fiber directional coupler inside the glass U-groove. Apply UV glue to both ends of the glass U-groove and cure it with a UV lamp. After curing, cover the outside of the glass U-groove with a section of heat shrink tubing and heat it in a high-temperature heating bath for about 1 minute. Finally, cover the outside of the heat shrink tubing with a steel pipe, apply UV glue to both ends of the steel pipe, and cure it with a UV lamp to obtain the packaged multi-core-single-mode fiber directional coupler.

[0033] Figure 4 This is a partially enlarged view of the fabricated and packaged tapered multicore-expanded single-mode fiber cascade. The multicore tapered fiber core 631.3 is the result of fusing the fiber core array into a single core after tapering the multicore fiber 631. The multicore tapered cladding 631.2 is the tapered cladding of the multicore fiber 631. The multicore input end cladding 631.1 is the initial multicore cladding. The diameter of the single-mode fiber core 632.3 at the left end of the expanded single-mode fiber 632 is equal to the diameter of the multi-core tapered fiber core 631.3 after expansion, while the diameter of the single-mode cladding 632.2 remains unchanged. The diameters of the single-mode output fiber core 632.4 and the single-mode output cladding 632.1 at the right end of the expanded single-mode fiber remain unchanged. The tapered multi-core fiber 631 and the expanded single-mode fiber 632 are fused together using a fusion splicer, and a heat shrink tubing 633 is placed over the fusion point. The fusion splicer is then heated in a high-temperature heating bath for about 1 minute to obtain the finished tapered multi-core-expanded single-mode fiber cascade.

[0034] Specifically: To fabricate a tapered multi-core-expanded single-mode fiber cascade, first connect the multi-core fiber to the light source and a tapering machine. Use wire strippers to remove a certain length of the coating from the multi-core fiber. Clean the stripped area with lint-free paper soaked in high-concentration alcohol before placing it on the tapering machine's fixture. Taper the multi-core fiber using an oxyhydrogen flame. Simultaneously, use the tapering machine's computer to monitor the loss during the tapering process in real time. Stop tapering when the fiber core array melts into a single core. Cut the tapered end face flat and use a microscope to measure the core and cladding diameters in the tapered area. Control the tapering machine parameters to ensure the tapered cladding diameter equals that of a standard single-mode fiber. Take one end of the single-mode fiber and use... Strip a certain length of coating from the single-mode fiber using wire strippers. Clean the stripped area with lint-free paper soaked in high-concentration alcohol and place it on the clamp of a tapering machine. Heat the single-mode fiber with an oxyhydrogen flame to expand its core, controlling the tapering machine parameters as needed. Stop heating when the core diameter of the expanded area of ​​the single-mode fiber matches the core diameter of the tapered area of ​​the multi-core fiber. Use a cleaver to flatten the tapered end face of the prepared tapered multi-core fiber and the expanded end face of the prepared expanded single-mode fiber. Use a fusion splicer to fuse the two fibers. Finally, cover the melting point with a heat shrink tubing and place it in a high-temperature heating bath for about 1 minute to obtain a tapered multi-core-expanded single-mode fiber cascade.

[0035] Figure 5 This is a partially enlarged view of the novel fiber optic collimator. The input ends of the fabricated fiber optic device 641 (corresponding to...) Figure 2 Multi-mode input terminal 611 Figure 3 Multi-core input terminal 621 and Figure 4 The input end of the multi-core optical fiber 631 is fitted with a capillary tube 643, heated and fixed together, and the collimating lens 644 (a type of C-Lens) is inserted into the glass sleeve 642. UV glue is dripped onto both ends and UV lamp is used to irradiate for about 20 seconds to achieve curing.

[0036] Specifically, the study involved encapsulating novel fiber optic collimators and system testing. The input ends of three fabricated fiber optic devices were connected to collimating lenses to obtain three integrated novel fiber optic collimators, which were then placed in a space light receiving system for coupling testing. The vibration resistance of these three novel fiber optic collimators was characterized. First, the optical path of the femtosecond pulse source was calibrated, and the laser power before entering the novel all-fiber space light receiver was measured using a power meter. This measurement result served as the total input power of the receiving system. Then, by iteratively fine-tuning the pitch and azimuth angles of the two reflectors and the offset of the three-dimensional adjustment frame, the laser was collimated and coupled to the novel fiber optic collimator. At this point, the maximum output power could be detected at the single-mode fiber output end of the novel fiber optic collimator. The maximum coupling efficiency of the system was calculated based on the total input power. Subsequently, this position was used as the reference for the three-dimensional electrically controlled displacement adjustment module. The offset was changed to simulate the vibration environment in space light reception, and the coupling efficiency under different offsets was recorded. Data fitting was used to characterize the vibration resistance of the space light receiving system using these three integrated novel fiber optic collimators.

[0037] The key technical point of this embodiment is to propose a scheme to prepare a multimode-single-mode fiber directional coupler with high power conversion efficiency and low insertion loss, a multi-core-single-mode fiber directional coupler, and a tapered multi-core-expanded single-mode fiber cascade to replace the tapered device in the traditional space light receiving system, and to integrate these three devices with a collimating lens to obtain a novel all-fiber fiber collimator. Firstly, for multimode-to-single-mode fiber directional couplers and multicore-to-single-mode fiber directional couplers, it is necessary to theoretically simulate and calculate the pre-stretched diameter of the multimode fiber and multicore fiber cladding to achieve maximum coupling efficiency based on coupling mode theory. Furthermore, for multicore fibers, it is essential to ensure that the pre-stretched core array melts into a single core. During experimental preparation, the pre-stretching length, flame height, and oxyhydrogen flame concentration, among other tapering parameters, need to be adjusted to reduce insertion loss during the drawing process. Secondly, for tapered multicore-expanded single-mode fiber cascades, during the tapered multicore fiber experiment, it is necessary to adjust the pre-stretching length, flame height, and oxyhydrogen flame concentration, among other tapering parameters, to ensure that the tapered core array melts into a single core after drawing, and that the cladding diameter is equal to that of a standard single-mode fiber. Similarly, for expanded single-mode fibers, it is necessary to adjust the flame height, oxyhydrogen flame concentration, and heating time, among other heating parameters, to ensure that the expanded single-mode core diameter is equal to the tapered core diameter of the tapered multicore fiber.

[0038] The fabrication methods for multimode-to-single-mode fiber directional couplers and multicore-to-single-mode fiber directional couplers proposed in this embodiment include how to adjust various parameters of the tapering machine to pre-stretch the multimode and multicore fibers to a specific diameter while ensuring that the multicore array is fused into a single core, and how to minimize the insertion loss of the fiber during the pre-stretching and formal tapering processes while achieving high power output efficiency at the single-mode output end. Compared with existing technologies, the fabrication process of the multimode-to-single-mode fiber directional couplers and multicore-to-single-mode fiber directional couplers proposed in this embodiment is simple. After tapering, they can be directly packaged without the need for side polishing. The packaged multimode-to-single-mode fiber directional couplers and multicore-to-single-mode fiber directional couplers have excellent stability. Furthermore, the lengths of the multimode and multicore input ends and the single-mode output end can be flexibly reserved according to the needs of the application scenario, facilitating subsequent operations after receiving spatial light, such as power detection, supercontinuum generation experiments, fiber optic communication, etc.

[0039] The method for fabricating a tapered multi-core-expanded single-mode fiber cascade proposed in this embodiment includes adjusting various parameters of the tapering machine to tapere the multi-core fiber to obtain a multi-core array fused into a single fiber core while maintaining a tapered region with a cladding diameter equal to that of a standard single-mode fiber. It also includes heating the single-mode fiber to achieve a core diameter at the expanded end that matches the core diameter of the tapered multi-core fiber's tapered region. Compared to existing technologies, this embodiment combines tapering and expansion techniques in fabricating the tapered multi-core-expanded single-mode fiber cascade, making the tapered region of the multi-core fiber less need for excessive fineness and more stable. Because the core diameter of the tapered region of the multi-core fiber is equal to that of the expanded single-mode fiber, core alignment can be ensured simply by aligning the cladding during the splicing process of the two fibers.

[0040] This embodiment proposes three approaches to fabricating optical fiber devices, including a scheme for achieving high-efficiency power coupling into single-mode fiber by using near-backside coupling between multimode and single-mode fibers, and a scheme for achieving high-efficiency power coupling into single-mode fiber by combining tapered and expanded core techniques for end-to-end low insertion loss fusion splicing of multimode and single-mode fibers. Compared with existing technologies, all three optical fiber devices exhibit excellent vibration resistance. The multimode input of the multimode-single-mode fiber directional coupler utilizes the advantage of the large core diameter of multimode fiber, maintaining high coupling efficiency even in environments with some vibration. The multimode input of the multimode-single-mode fiber directional coupler and the tapered multimode fiber-expanded single-mode fiber cascade utilizes the advantage of the multi-core fiber array, maintaining good coupling efficiency even in environments with some vibration.

[0041] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A shockproof spatial light receiving device based on a novel fiber optic collimator, characterized in that, include: The invention comprises a femtosecond pulse source, a reflector, a three-dimensional electrically controlled displacement adjustment module, a fixture, a novel fiber optic collimator, and a power detector; wherein the novel fiber optic collimator is obtained by cascading and packaging a collimating lens and fiber optic devices, and the fiber optic devices include: a multimode-single-mode fiber directional coupler, a multicore-single-mode fiber directional coupler, and a tapered multicore-expanded single-mode fiber cascade; The femtosecond pulse light source emits spatial light, which is reflected by the mirror and enters the three-dimensional electronically controlled displacement adjustment module to calibrate and couple the spatial light. Then, it is sent to the new fiber collimator on the fixture to focus the received spatial light and couple it with a high coupling ratio. Finally, the output power of the spatial light is recorded based on the power detector. The reflector includes a first reflector and a second reflector. By adjusting the pitch angle and azimuth angle of the first and second reflectors, spatial light can be collimated and coupled into the novel fiber optic collimator. The three-dimensional electrically controlled displacement adjustment module includes a three-dimensional displacement adjustment frame and an open-loop piezoelectric controller; The open-loop piezoelectric controller is used to quantitatively move the three-dimensional displacement adjustment frame by adjusting the open-loop voltage, so that spatial light can be collimated and coupled into the novel fiber collimator; The fabrication process of the novel fiber collimator includes: combining the multimode-single-mode fiber directional coupler, the multicore-single-mode fiber directional coupler, and the tapered multicore-expanded single-mode fiber cascade into a fiber optic device; covering the input end of the fiber optic device with a capillary tube for heating and fixing; and inserting it together with the collimating lens into a glass sleeve for curing treatment to complete the fabrication of the novel fiber collimator.

2. The shockproof spatial light receiving device based on a novel fiber optic collimator according to claim 1, characterized in that, The fabrication process of the multimode-single-mode fiber directional coupler includes: pre-tapering the multimode fiber using a tapering machine; stopping tapering when the diameter of the tapered region of the multimode fiber reaches the preset size that satisfies the phase matching condition; then knotting and fusion tapering the single-mode fiber and the tapered multimode fiber; stopping tapering when the output power of the single-mode fiber reaches the maximum coupling ratio; placing the processed fiber and coupler into a glass U-groove to complete curing; and finally covering it with a heat-shrink tubing to complete the fabrication of the multimode-single-mode fiber directional coupler.

3. The shockproof spatial light receiving device based on a novel fiber optic collimator according to claim 1, characterized in that, The fabrication process of the multi-core-single-mode fiber directional coupler includes: tapering the multi-core fiber using a tapering machine; stopping tapering when the diameter of the tapered region of the multi-core fiber reaches the preset size that satisfies the phase matching condition; knotting and fusion tapering the single-mode fiber and the tapered multi-core fiber together; stopping tapering when the output power of the single-mode fiber reaches the maximum coupling ratio; placing the processed fiber and coupler into a glass U-groove to complete curing; and finally covering it with a heat-shrink tubing to complete the fabrication of the multi-core-single-mode fiber directional coupler.

4. The shockproof spatial light receiving device based on a novel fiber optic collimator according to claim 1, characterized in that, The fabrication process of the tapered multi-core-single-mode fiber cascade includes: tapering the multi-core fiber using a tapering machine; stopping tapering when the fiber core array melts into a single fiber core and the cladding diameter of the tapered region of the fiber core is equal to the cladding diameter of the single-mode fiber; heating and expanding the single-mode fiber using the tapering machine; stopping heating when the core diameter of the single-mode fiber matches the core diameter of the tapered region of the multi-core fiber; fusion splicing the two fibers after the expansion process using a fusion splicer; and finally, applying a heat-shrink tubing at the melting point to complete the fabrication of the tapered multi-core-single-mode fiber cascade.

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