Optical fiber nutation coupling device and method of use thereof

Abstract

The present invention provides a fiber nutation coupling device and a method for using the device, which relates to the field of laser communication technology. The device mainly includes: a splitter module, a light spot position monitoring module, a fiber coupling adjustment module, a nutation scanning module, a receiving fiber, and a main base. The system is initialized and calibrated using the splitter module, the light spot position monitoring module, and the fiber coupling adjustment module, and the light beam entering the nutation scanning module is constrained to a specific small area. The light beam is then coupled into the receiving fiber through nutation scanning. The device of the present invention can solve the problem of the difficulty in efficiently and stably coupling free-space light to a single-mode fiber in the prior art. At the same time, the device adopts a modular design concept, highly integrating the nutation coupling system, with a compact structure, small size, light weight, low power consumption, and convenient system debugging and assembly.

Description

Technical Field

[0001] The present invention relates to the field of laser communication technology, and in particular to an optical fiber nutation coupling device and a method for using the same. Background Art

[0002] In recent years, as satellite-borne laser communication terminal technology has become increasingly mature, the demand for commercialization of laser communication terminals has become increasingly urgent. Considering factors such as optical machining and assembly deviations, slight mechanical structure deformation caused by temperature and stress changes on the satellite platform in orbit, platform vibration, and the misalignment of the system's transmit and receive axes, coupling the weak signal light entering the optical system into a 9um single-mode fiber is undoubtedly very difficult. Therefore, efficient and stable free-space light-to-single-mode fiber coupling technology is the prerequisite and guarantee for the realization of high-speed, long-distance laser communication technology, and is also a key technology in space laser communication. At the same time, due to optical machining, assembly, vibration, and other factors, the coupled beam will have tilt, defocus, or other aberration problems, resulting in a significant decrease in the coupling quality of space light to single-mode fiber. Therefore, the industry urgently needs to develop automatic fiber coupling technology to improve coupling efficiency and thus ensure the quality of free-space laser communication.

[0003] Patent application CN110401483A, titled "A Laser Communication Device and Method," utilizes a fast-reflection mirror as a nutating coupling mirror for single-mode fiber nutation coupling. However, the position of the light spot cannot be determined during fiber nutation coupling. This uncertainty in the light spot position requires a wide-area scan near the uncertain location before coupling the signal light into the fiber. Consequently, this fiber coupling solution is inefficient and ineffective. Summary of the Invention

[0004] The purpose of the present invention is to provide an optical fiber nutation coupling device and a method of using the same, so as to solve the problem in the prior art of difficulty in efficiently and stably coupling free-space light to a single-mode optical fiber.

[0005] To solve the above technical problems, the present invention provides a fiber nutation coupling device, which includes a light splitting module, a light spot position monitoring module, a fiber coupling adjustment module, a nutation scanning module, a receiving fiber and a main base.

[0006] The spectroscopic surface of the spectroscopic module is fixed at a 45-degree angle to the main base. When incident light strikes the spectroscopic surface at normal incidence, it is split by the spectroscopic surface. The reflected light enters the light spot position monitoring module perpendicular to the incident light, while the transmitted light enters the nutating scanning module along the direction of the incident light. When a light beam strikes the first surface of the spectroscopic module at normal incidence, it strikes the spectroscopic surface at a 45-degree angle of incidence. According to the principle of light reflection, the angle of incidence equals the angle of reflection, and the reflected light is perpendicular to the incident light. According to the law of refraction, when light enters a transparent medium at normal incidence (i.e., an angle of incidence of 0 degrees, perpendicular to the medium surface), the direction of the transmitted light remains unchanged, allowing the transmitted light to enter the nutating scanning module along its original optical path.

[0007] The light spot position monitoring module includes a position detection focusing lens and a position detector for monitoring the reflected light spot position. The reflected light is incident on the position detector through the position detection focusing lens. The position detection focusing lens and the position detector are each bolted to the main base via a slidably adjustable structure (including at least a bolt slot) to adjust the focal length of the light spot position monitoring module. The spectrometer module and the reflected light spot position monitoring module form a mirror image of the receiving optical fiber and the transmitted light spot. By adjusting and monitoring the optical path of the reflected light, the reflected light spot position is confined to a specific small range, thereby confining the transmitted light spot to a specific small range.

[0008] The nutation scanning module includes a nutation coupling quick-reflection mirror and a quick-reflection mirror controller. The quick-reflection mirror controller is used to control the nutation coupling quick-reflection mirror to scan within a coupling scanning area.

[0009] The fiber-coupled adjustment module includes a fiber-coupled focusing lens, an incident lens barrel, a fiber flange, a three-point adjustment disk, and an L-shaped support plate. The fiber flange is arranged at one end of the incident lens barrel and is used to install a receiving optical fiber. The other end of the incident lens barrel passes through the vertical surface of the L-shaped support plate and the three-point adjustment disk and is inserted into the lens barrel of the fiber-coupled focusing lens. The three-point adjustment disk is installed on the vertical surface of the L-shaped support plate. The horizontal surface of the L-shaped support plate and the fiber-coupled focusing lens are respectively connected to the main base through a bolt-fastened sliding adjustable structure for adjusting the focal length of the fiber-coupled adjustment module.

[0010] The transmitted light is reflected by the nutation coupling fast reflection mirror and enters the fiber coupling focusing mirror, and then enters the receiving fiber through the incident lens barrel. The incident lens barrel of the fiber coupling adjustment module is inserted into the fiber coupling focusing mirror as a whole, which can prevent the interference of stray light.

[0011] Furthermore, the three-point adjustment plate is mounted on the vertical plate of the L-shaped support plate through studs.

[0012] Furthermore, three adjusting screws are provided on the three-point adjustment disk, through which the receiving optical fiber and the incident lens barrel can be finely adjusted in position and angle, which can reach the micron level.

[0013] By adjusting the adjustable structure in the above device, the device is initialized and calibrated. After initialization and calibration, the optical axis of the incident light entering the light spot position monitoring module and the optical axis of the transmitted light entering the fiber coupling adjustment module after being reflected by the nutating scanning fast reflection mirror are highly aligned.

[0014] In a feasible implementation, the nutation coupling device further includes a light blocking plate fixed outside the gap between the nutation coupling fast reflection mirror and the fiber coupling focusing mirror for eliminating interfering light.

[0015] In a feasible implementation, the light splitting module includes a cubic light splitting prism. The cubic light splitting prism has stable light splitting performance, regular shape, small size, and compact structure, which is conducive to integration and installation and debugging.

[0016] Preferably, the reflection / transmission ratio of the beam splitting surface of the cube beam splitter prism is set to 50 / 50.

[0017] In a feasible embodiment, the position detector includes a spot imaging sensor, a detector packaging cover and a detector window. The spot imaging sensor and the detector window are respectively arranged at the center positions of both ends of the detector packaging cover. The end of the detector packaging cover provided with the detector window is inserted into the lens barrel of the position detection focusing lens. The fastening bolt slots of the position detector are arranged at corresponding positions of the detector packaging cover base and the main base. The spot imaging sensor uses a charge-coupled device (CCD) to collect spot images in real time.

[0018] The CCD consists of a photosensitive pixel array, a charge transfer channel, and a readout circuit. It converts light signals into voltage signals, which are then amplified and converted to digital signals (ADC) to form a digital image. The coordinates of the light spot center are calculated based on the pixel grayscale values. The CCD features high sensitivity and low noise. The detector housing is connected to the position detection focusing lens barrel through a detector window, which prevents reflected light from being interfered with by external light, further enhancing precision.

[0019] In one feasible embodiment, fastening bolt slots are provided at the bases of the L-shaped support plate, the fiber-coupled focusing lens, and the position detection focusing lens, respectively, for lateral sliding adjustment and fixation of the fiber-coupled adjustment module, the fiber-coupled focusing lens, and the position detection focusing lens. The fastening bolt slot of the position detector is configured as an axially oblong circle, which is used to adjust and fix the position detector axially, so that the reflected light spot remains at the center of the position detector.

[0020] In the overall structural design of this device, the optical paths of the spot position monitoring module and the fiber coupling adjustment module are parallel on the same horizontal plane. By setting the fastening bolt slots, the focal lengths of the two modules can be adjusted more finely.

[0021] In a feasible embodiment, the fiber-coupled focusing mirror includes a first focusing mirror base, a first focusing mirror and a first narrow-band filter. The first focusing mirror and the first narrow-band filter are respectively arranged in the middle and one end of the lens barrel of the first focusing mirror base. The incident light enters the first focusing mirror after being filtered by the first narrow-band filter. The other end of the lens barrel is used to insert the incident lens barrel. The fastening bolt grooves of the fiber-coupled focusing mirror are arranged at corresponding positions of the main base and the first focusing mirror base.

[0022] Similarly, the position detection focusing lens includes a second focusing lens seat, a second focusing lens and a second narrow-band filter. The second focusing lens and the second narrow-band filter are respectively arranged in the middle and one end of the lens barrel of the second focusing lens seat. The incident light enters the second focusing lens after being filtered by the second narrow-band filter. The other end of the lens barrel is used to insert one end of the position detector packaging cover where the detector window is provided. The fastening bolt slots of the position detection focusing lens are arranged at corresponding positions of the main base and the second focusing lens seat.

[0023] In another feasible implementation, the first narrowband filter, the second narrowband filter, and the narrowband filter of the detector window can all be replaced with plane mirrors.

[0024] In one feasible embodiment, a nutating coupled fast-reflecting mirror includes a fast-reflecting mirror base, a fast-reflecting mirror magnifying structure, piezoelectric ceramics, a lens holder, a flexible hinge, a reflective lens, and a pressure cover. The fast-reflecting mirror base is an L-shaped panel, the horizontal surface of the L-shaped panel being fixed to the upper surface of the fast-reflecting mirror controller, and the fast-reflecting mirror base being fixed to the vertical surface of the L-shaped panel by bolts fastening a sliding adjustable structure. The fast-reflecting mirror magnifying structure includes four identical triangular connecting rods, the horizontal rods of the triangular connecting rods being fixed to the fast-reflecting mirror base and being equidistant from the center of the bottom surface of the fast-reflecting mirror base. The diagonal support rods of the triangular connecting rods form an acute angle with the horizontal rods. The piezoelectric ceramics are arranged between the horizontal rods and the diagonal support rods of the triangular connecting rods. The lens holder is mounted on top of the four diagonal support rods. The reflective lens is mounted on the lens holder via a flexible hinge. The pressure cover is an annular structure mounted on top of the fast-reflecting mirror base, encapsulating the fast-reflecting mirror magnifying structure, piezoelectric ceramics, lens holder, flexible hinge, and reflective lens within the fast-reflecting mirror base.

[0025] When voltage is applied to the piezoelectric ceramic, the piezoelectric ceramic produces a displacement change, thereby changing the angle between the diagonal support rod and the horizontal rod of the corresponding triangular link, causing the position of the top of the diagonal support rod to rise or fall, driving the corresponding position of the reflector seat and reflective lens to move accordingly, thereby changing the angle of the reflective lens.

[0026] The nutation-coupled fast mirror has a simple and compact structure, is easy to integrate, assemble, disassemble and repair, and has high sensitivity to the control of the reflection angle.

[0027] In a feasible implementation, the method for initializing and calibrating the nutation coupling device is:

[0028] Step a1, controlling the incident light to be incident on the incident surface of the light splitting module, so that the reflected light enters the light spot position monitoring module perpendicular to the incident light, and the transmitted light enters the nutating scanning module along the direction of the incident light;

[0029] Step a2, adjusting the positions of the position detection focusing mirror and the position detector by tightening the sliding adjustable structure with bolts, so that the reflected light is focused on the center position of the position detector and remains stationary;

[0030] Step a3, setting the nutation-coupled fast-reflection mirror at zero position and adjusting the position of the receiving optical fiber on the vertical plane by using the L-shaped support plate and the three-point adjustment plate so that the incident light enters the receiving optical fiber and the optical power reaches the maximum value;

[0031] Step a4, adjusting the focal length by changing the front and rear position of the incident lens barrel extending into the fiber-coupled focusing lens barrel and the three-point adjustment dial to maximize the optical power incident on the receiving optical fiber;

[0032] Step a5: Adjust the position of the nutating coupling fast-reflection mirror on the vertical plane so that the incident light enters the receiving optical fiber and the received optical power reaches a maximum value. Record the current position of the nutating coupling fast-reflection mirror as the ground reference zero position.

[0033] Step a6, fixing the sliding adjustable structures so that the modules are fixed, determining the coupling scanning area of ​​the nutating coupling fast-reflection mirror, and setting it through the fast-reflection mirror controller;

[0034] Step a7: After the device is launched into orbit, the nutation-coupled quick-reflection mirror is fine-tuned again by the quick-reflection mirror controller according to the ground reference zero position so that the optical power incident on the receiving optical fiber reaches the maximum, and the position of the nutation-coupled quick-reflection mirror at this time is set as the onboard reference zero position.

[0035] After initializing and calibrating the device using the above method, the optical axes of the spot position monitoring module and the receiving fiber are parallel and coplanar, and the beams are focused on the center of the position monitor and a small, defined area centered on the receiving fiber core, known as the coupling scanning area. Initial calibration is completed by setting the reference zero position of the nutating scanning mirror and the coupling scanning area using the fast-reflection mirror controller.

[0036] In a feasible embodiment, the specific method of using the nutation coupling device provided by the present invention to receive free-space light into an optical fiber includes:

[0037] Step b1, allowing free-space light to be incident on the incident surface of the spectroscopic module. After being split by the spectroscopic surface, the reflected light enters the light spot position monitoring module perpendicular to the incident light, and the transmitted light enters the nutating scanning module along the direction of the incident light.

[0038] Step b2: Adjust the free-space light so that the reflected light spot remains at the center of the spot position monitoring module. At the same time, the transmitted light enters the fiber-coupled focusing mirror and the incident lens barrel through the nutating coupling fast reflection mirror, and the light spot is within the coupling scanning area.

[0039] Step b3, controlling the nutating coupling fast-reflection mirror by the fast-reflection mirror controller to scan within the coupling scanning area, so that the light spot is coupled into the optical fiber;

[0040] The coupling scanning area refers to the area with the strongest optical fiber coupling within a predetermined range near the reference zero position of the nutating coupling fast reflection mirror calibrated by initialization calibration.

[0041] By adopting the above technical solution, the present invention has the following beneficial effects:

[0042] The present invention provides a fiber nutation coupling device and its use method. This device uses a light splitting module, a spot position detector, and a fiber coupling adjustment module to initialize and calibrate the device. This allows for the pre-calibration of the strongest fiber coupling position, limiting the coupling efficiency variation caused by nutation to a defined, small range. Nutation scanning then allows for rapid and efficient coupling of the light beam into the receiving fiber core. This device addresses the existing technical challenges of efficiently and stably coupling free-space light into single-mode fiber. Furthermore, the device utilizes a modular design concept, highly integrating the nutation coupling system. This compact structure, small size, light weight, and low power consumption facilitate system assembly, commissioning, and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are 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.

[0044] Figure 1 A three-dimensional structural diagram of an optical fiber nutation coupling device provided in an embodiment of the present invention;

[0045] Figure 2 A top view of the structure of the optical fiber nutation coupling device provided by an embodiment of the present invention;

[0046] Figure 3A three-dimensional structural diagram of a fiber coupling assembly module provided in an embodiment of the present invention;

[0047] Figure 4 A top view of the structure of the optical fiber coupling and adjustment module provided in an embodiment of the present invention;

[0048] Figure 5 An exploded view of the structure of a nutation-coupled fast-reflection mirror provided in an embodiment of the present invention;

[0049] Figure 6 Comparison diagram of the light spot positions detected by the position detector before and after initialization calibration provided by an embodiment of the present invention, wherein (a) shows the light spot position detected by the position detector before initialization calibration; (b) shows the light spot position detected by the position detector after initialization calibration;

[0050] Figure 7 A flow chart of a method for initializing and calibrating an optical fiber nutation coupling device provided in an embodiment of the present invention;

[0051] Figure 8 A flow chart of a method for receiving free-space light into a single-mode optical fiber using an optical fiber nutation coupling device provided in an embodiment of the present invention;

[0052] Reference numerals:

[0053] 1-fiber flange; 2-incident lens barrel; 3-L-shaped support plate; 4-three-point adjustment dial; 5-first focusing lens mount; 6-first focusing lens; 7-first spacer; 8-first narrowband filter; 9-second spacer; 10-light baffle; 11-fast mirror base; 12-nutation coupling fast mirror; 13-fast mirror controller; 14-beam splitter prism base; 15-beam splitter prism; 16-third spacer; 17-second narrowband filter; 18- Fourth spacer; 19-second focusing mirror; 20-second focusing mirror seat; 21-detector packaging cover; 22-spot imaging sensor; 23-detector window; 24-main base; 25-sliding adjustable structure; 26-stud; 1201-quick reflex mirror base; 1202-quick reflex mirror magnifying structure; 1203-piezoelectric ceramic; 1204-lens seat; 1205-flexible hinge; 1206-pressure cover; 1207-reflecting lens. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0055] The present invention will be further explained below with reference to specific embodiments.

[0056] The design concept of the device of the present invention is based on the principle of light reflection and the law of light refraction. A spectrometer module, a light spot position detection module, and a fiber coupling adjustment module are added to the traditional nutation coupling device. The light spot position of the reflected light from the same source as the receiving light source is used as a reference. The strongest position of the fiber coupling is calibrated in advance through initialization calibration, and the coupling efficiency change caused by nutation is controlled within a certain small range. Then, the free-space light is quickly and efficiently coupled into the core of the receiving fiber through nutation scanning.

[0057] Example 1

[0058] like Figure 1 and Figure 2 The figures show the front view and top cross-sectional view of the structure of the optical fiber nutation coupling device provided by an embodiment of the present invention, which mainly includes a light splitting module, a light spot position monitoring module, an optical fiber coupling adjustment module, a nutation scanning module, a receiving optical fiber and a main base 24;

[0059] The splitting surface of the splitting module is fixed at a 45-degree angle to the main base 24. The incident light is incident on the incident surface of the splitting module. After being split by the splitting surface, the reflected light enters the light spot position monitoring module perpendicular to the incident light, and the transmitted light enters the nutating scanning module along the direction of the incident light.

[0060] The light spot position monitoring module includes a position detection focusing lens and a position detector, which are used to monitor the light spot position of the reflected light. The reflected light is incident on the position detector through the position detection focusing lens. The position detection focusing lens and the position detector are respectively connected to the main base 24 by bolts fastening the sliding adjustable structure 25, which is used to adjust the focal length of the light spot position monitoring module;

[0061] A nutation scanning module includes a nutation coupling fast-reflection mirror 12 and a fast-reflection mirror controller 13, wherein the fast-reflection mirror controller 13 is used to control the nutation coupling fast-reflection mirror 12 to perform nutation scanning within a coupling scanning area;

[0062] In this embodiment, the fiber coupling adjustment module includes a fiber coupling focusing lens, an incident lens barrel 2, a fiber flange 1, a three-point adjustment disk 4 and an L-shaped support plate 3. The fiber flange 1 is provided at one end of the incident lens barrel 2 for mounting a receiving optical fiber. The other end of the incident lens barrel 2 passes through the vertical surface of the L-shaped support plate 3 and the three-point adjustment disk 4 and is inserted into the lens barrel of the fiber coupling focusing lens. The three-point adjustment disk 4 is mounted on the vertical surface of the L-shaped support plate 3. The horizontal surface of the L-shaped support plate 3 and the fiber coupling focusing lens are respectively connected to the main base 24 by bolt-fastening sliding adjustable structures 25 for adjusting the focal length of the fiber coupling adjustment module.

[0063] The three-point adjustment plate 4 is mounted on the vertical plate of the L-shaped support plate 3 through the studs 26. The three-point adjustment plate 4 is provided with three adjustment screws, through which the receiving optical fiber and the incident lens barrel 2 can be finely adjusted in position and angle, which can reach the micron level.

[0064] The transmitted light is reflected by the nutation-coupled fast-reflecting mirror 12 and enters the fiber-coupled focusing mirror, and then passes through the incident lens barrel 2 and enters the receiving optical fiber.

[0065] In this embodiment, in addition to the aforementioned modules, the device also includes a light baffle 10, secured outside the gap between the nutating-coupled fast-reflection mirror 12 and the fiber-coupled focusing mirror. This baffle is used to exclude interfering light and prevent ambient light (e.g., sunlight) or internal system reflected light from entering the fiber-coupled alignment module. A triangular support plate with a base is located on the back of the light baffle 10, which is secured to the upper surface of the fast-reflection mirror controller 13 or the main base 24 via screws, providing a more stable overall structure. The light baffle 10 is preferably made of metal, and its surface is black-plated to absorb stray light.

[0066] The main base 24 is used to fix the modules, compactly combining the modules together, and at the same time making the overall structure more stable and improving the accuracy of the system.

[0067] In this embodiment, the beam splitting module uses a cubic beam splitter prism 15. The beam splitter prism 15 splits the incident light into two paths. One path enters the spot position monitoring module, and the other path passes through the nutating scanning module, the fiber coupling adjustment module, and the receiving fiber, and enters the coupling fiber. The splitting ratio is 1:1 or 2:8.

[0068] In a specific implementation, the beam splitter prism 15 is formed by gluing two right-angle prisms together, and a beam splitter film is coated on the interface to achieve reflection and transmission beam splitting of the incident light; the beam splitter film has different coating designs according to the laser wavelength.

[0069] Furthermore, in order to protect the dichroic prism body and facilitate fixation, a protective cover is provided on the outside of the dichroic prism 15. Windows are left on three sides of the protective cover, which are used for the entry of incident light and the emission of transmitted light and reflected light respectively. The bottom surface is fixed on the dichroic prism base 14 so that the centers of each module in the device are kept in the same horizontal plane to ensure the consistency of the optical path. The other surfaces are preferably made of shading materials to reduce the interference of stray light on the signal light.

[0070] In this embodiment, the position detector includes a spot imaging sensor 22, a detector housing 21, and a detector window 23. The spot imaging sensor 22 and detector window 23 are located at the center of each end of the detector housing 21. The end of the detector housing 21 with the detector window 23 is inserted into the barrel of the position detection focusing lens. The position detector's fastening bolt slots are located at corresponding positions on the base of the detector housing 21 and the main base 24. The spot imaging sensor 22 uses a CCD to capture the spot image in real time. The spot position can be viewed and monitored in real time using an external device or software. The CCD's photosensitive pixel size can be micron-scale, meeting the high-resolution requirements of fiber-optic communications.

[0071] Furthermore, the detector packaging cover 21 of the position detector is made of a light-shielding material.

[0072] Furthermore, a narrowband filter is provided in the detector window 23 to suppress the interference of stray light and improve the quality of the signal light.

[0073] like Figure 3 and Figure 4 The main view and top cross-sectional view of the fiber coupling adjustment module structure diagram are shown. The L-shaped support plate 3, the base of the fiber coupling focusing mirror and the position detection focusing mirror are all provided with a sliding adjustable structure 25, which is used to slide and adjust the lateral position of the fiber coupling adjustment module, the fiber coupling focusing mirror and the position detection focusing mirror respectively.

[0074] In this embodiment, the fiber-coupled focusing mirror includes a first focusing mirror base 5, a first focusing mirror 6 and a first narrow-band filter 8. The first focusing mirror 6 and the first narrow-band filter 8 are respectively arranged in the middle and one end of the lens barrel of the first focusing mirror base 5. The incident light enters the first focusing mirror 6 after being filtered by the first narrow-band filter 8. The other end of the lens barrel is used to insert the incident lens barrel 2. The sliding adjustable structure 25 of the fiber-coupled focusing mirror is arranged at the corresponding positions of the main base 24 and the first focusing mirror base 5.

[0075] Furthermore, the first focusing lens 6 and the first narrowband filter 8 are secured to the middle of the lens barrel of the fiber-coupled focusing lens and the end where the signal light enters, respectively, via a first spacer 7 and a second spacer 9. A space is reserved at the other end of the lens barrel for inserting the incident lens barrel 2. Adjusting the insertion length of the incident lens barrel 2 adjusts the focal length of the first focusing lens 6.

[0076] Similarly, the position detection focusing mirror includes a second focusing mirror seat 20, a second focusing mirror 19 and a second narrow-band filter 17. The second narrow-band filter 17 and the second focusing mirror 19 are fixed to the middle and one end of the position detection focusing mirror barrel respectively through the third spacer 16 and the fourth spacer 18. The incident light enters the second focusing mirror 19 after being filtered by the second narrow-band filter 17. The other end of the barrel is used to insert the detector packaging cover 21 and is provided with an end of the detector window 23. The sliding adjustable structure 25 of the position detection focusing mirror is set at the corresponding positions of the main base 24 and the second focusing mirror seat 20.

[0077] Furthermore, the first narrowband filter 8, the second narrowband filter 17 and the narrowband filter of the detector window 23 can be configured or exchanged according to the wavelength of the signal light to enhance the suppression of interference waves and improve the quality of the signal light.

[0078] like Figure 5 As shown, in this embodiment, the nutation-coupled quick-reflection mirror 12 includes a quick-reflection mirror base 11 , a quick-reflection mirror base 1201 , a quick-reflection mirror magnifying structure 1202 , piezoelectric ceramics 1203 , a lens holder 1204 , a flexible hinge 1205 , a reflective lens 1207 and a pressure cover 1206 .

[0079] Furthermore, the quick-reflection mirror base 11 is an L-shaped panel, the horizontal surface of the L-shaped panel is fixed to the upper surface of the quick-reflection mirror controller 13, and the quick-reflection mirror base 1201 is fixed to the vertical surface of the L-shaped panel by fastening the sliding adjustable structure 25 with bolts. The quick-reflection mirror magnifying structure 1202 includes four triangular connecting rods with the same structure. The horizontal rods of the triangular connecting rods are all fixed to the quick-reflection mirror base 11 and are at equal distances from the center of the bottom surface of the quick-reflection mirror base 1201; the diagonal support rods of the triangular connecting rods form an acute angle with the horizontal rods, and the pressure The piezoelectric ceramic 1203 is arranged between the horizontal rod and the diagonal support rod of the triangular connecting rod, the lens seat 1204 is installed on the top of the four diagonal support rods, the reflective lens 1207 is installed on the lens seat 1204 through the flexible hinge 1205, and the pressure cover 1206 is a ring structure and is installed on the top of the quick-reflection mirror base 1201, encapsulating the quick-reflection mirror magnifying structure 1202, piezoelectric ceramic 1203, lens seat 1204, flexible hinge 1205 and reflective lens 1207 in the quick-reflection mirror base 1201.

[0080] Furthermore, a fastening bolt groove of the bolt fastening sliding adjustable structure 25 is provided on the bottom of the quick reflex mirror base 1201 and / or the vertical surface of the quick reflex mirror base 11, so as to adjust the position of the quick reflex mirror base 1201 on the vertical plane (including the longitudinal X direction and Y direction).

[0081] Furthermore, a high-precision displacement sensor is provided on the piezoelectric ceramic 1203 to feed back the displacement of the piezoelectric ceramic 1203 to the fast mirror controller 13, so that the fast mirror controller 13 can adaptively control the nutation coupling fast mirror 12 to complete the coupling of the signal light to the receiving optical fiber.

[0082] like Figure 7 As shown, in this embodiment, the method for initializing and calibrating the optical fiber nutation coupling device is:

[0083] Step a1, controlling the incident light to be incident on the incident surface of the light splitting module, so that the reflected light enters the light spot position monitoring module perpendicular to the incident light, and the transmitted light enters the nutating scanning module along the direction of the incident light.

[0084] The position of the beam splitter prism 15 is fixed, and the incident light can be adjusted by the self-collimation method to ensure that the light is incident on the first surface of the beam splitter prism 15. The reflecting surface of the beam splitter prism 15 is fixed at 45 degrees to ensure that the reflected light is perpendicular to the incident light.

[0085] Step a2: Adjust the positions of the position detection focusing mirror and the position detector by tightening the sliding adjustable structure 25 with bolts, so that the reflected light is focused on the center position of the position detector and remains stationary.

[0086] After the incident light is split by the spectrometer, the reflected light passes through the position detection focusing lens, forming a reflected light spot at the center of the position detector's spot imaging sensor 22. The position detection focusing lens and the position detector's bolted, adjustable sliding structure 25 adjust the optical path of the reflected light so that the reflected light spot is focused at the center of the spot imaging sensor 22. The position of the range spot is monitored by monitoring equipment or software. Using CCD imaging technology, micron-level resolution can be achieved. The reflected light spot remains fixed and serves as a reference for subsequent calibration steps.

[0087] In step a3, the nutating-coupled fast-reflection mirror 12 is set to zero and fixed. The position of the receiving fiber in the vertical plane is adjusted using the L-shaped support plate 3 and the three-point adjustment dial 4 to ensure that the incident light enters the receiving fiber and maximizes the optical power. The receiving fiber is fixed to the fiber flange 1. The position of the receiving fiber is adjusted by micro-moving the fiber flange 1 to adjust the focus of the light spot.

[0088] Step a4: adjust the focal length by changing the front and rear positions of the incident lens barrel 2 extending into the optical fiber coupling focusing lens barrel and the three-point adjustment disk 4 to maximize the optical power incident on the receiving optical fiber.

[0089] After the incident light is split by the spectrometer, the transmitted light is reflected by the nutating coupling fast-reflection mirror 12 and enters the fiber-coupled focusing mirror. It then passes through the incident lens barrel 2 and enters the receiving optical fiber. However, because the fiber core end face is extremely small (micrometer level), the light beam cannot be precisely aligned with the fiber end face. The design concept of the device of the present invention is to overcome various errors caused by the objective environment as much as possible through high-precision initialization calibration, and control the received light beam to a small area near the fiber end face. Therefore, in the design of the fiber-coupled adjustment module, in addition to the ability to adjust the position of the L-shaped support plate 3 and the fiber-coupled focusing mirror by tightening the sliding adjustable structure 25 with bolts, a three-point adjustment dial 4 is also designed to fine-tune the receiving light path to the micrometer level.

[0090] In steps a3 and a4, the position of the nutation-coupled fast-reflection mirror 12 is first determined, and then the position of the receiving optical fiber is adjusted in the vertical plane and the axial direction respectively, so that the received light is incident on the end face of the receiving optical fiber as normally as possible.

[0091] The three-point adjustment disk 4 is used to fine-tune the position of the receiving optical fiber. During the system installation process, the initial position of the receiving optical fiber is adjusted by the three top screws on the three-point adjustment disk 4 so that the center of the receiving light spot of the light spot position detector is coaxial with the optical path of the receiving optical fiber under static conditions.

[0092] Step a5: Adjust the position of the nutating coupling fast-reflection mirror 12 on the vertical plane so that the incident light enters the receiving optical fiber and the received optical power reaches a maximum value. Record the current position of the nutating coupling fast-reflection mirror 12 as the ground reference zero position.

[0093] The position of the quick mirror base 1201 in the vertical plane, including the longitudinal X and Y directions, is adjusted by fastening the fastening bolt grooves of the adjustable sliding structure 25 provided on the bottom of the quick mirror base 1201 and / or the vertical surface of the quick mirror base 11 .

[0094] Step a6: fix the sliding adjustable structures 25 to keep the modules in fixed positions, determine the coupling scanning area of ​​the nutating coupling fast reflection mirror 12 , and set it through the fast reflection mirror controller 13 .

[0095] In practice, any of steps a1-a6 can be repeatedly adjusted multiple times based on actual conditions until the preset initial calibration criteria for the device are achieved. Ultimately, the positions of the various components in the fixture remain unchanged, the position detector remains aligned with the optical axis of the optical fiber core, and the optical power entering the receiving fiber is maximized. This completes the ground initialization calibration of the device of the present invention.

[0096] Step a7: After the device is launched into orbit, the nutating coupling fast-reflection mirror 12 is fine-tuned again by the fast-reflection mirror controller 13 according to the ground reference zero position so that the optical power incident on the receiving optical fiber reaches the maximum. The position of the nutating coupling fast-reflection mirror 12 at this time is set as the onboard reference zero position.

[0097] In the above steps, the reference zero position confirmation process is achieved by setting the output voltage of the fast mirror controller 13. Different positions of the nutating coupled fast mirror 12 correspond to different control voltages, and different nutating coupled fast mirrors 12 correspond to different control voltage value ranges. For example, a nutating coupled fast mirror 12 with an input voltage range of -10V to 10V has a scanning range of -2mrad to +2mrad (i.e., the position range of the nutating coupled fast mirror 12). After the initialization calibration is completed, the corresponding initialization configuration is completed by the fast mirror controller 13. In addition to setting the reference zero position and the coupled scanning area, it also includes setting parameters such as the scanning path, scanning speed, and scanning mode.

[0098] From the ground to the satellite, various objective reasons such as micro-deformation of the mechanical structure and drastic changes in ambient temperature will cause slight changes in the position of the receiving light spot, affecting the alignment efficiency and accuracy of the receiving optical fiber and the receiving light spot. Therefore, in the on-orbit environment, it is necessary to recalibrate the reference zero position of the nutating coupling fast reflection mirror 12 and the coupling scanning area corresponding to the new reference zero position to improve the alignment efficiency and accuracy.

[0099] In other embodiments, during routine maintenance of the device of the present invention, the reference zero position of the nutating coupling fast mirror 12 can be periodically and automatically calibrated through program control of the fast mirror controller 13, or a calibration instruction can be sent from the ground to the fast mirror controller 13 to perform reference zero calibration to maintain the validity of the coupled scanning area.

[0100] The coupling scanning area refers to the region of strongest fiber coupling within a predetermined range around the reference zero position of the nutating coupling fast-reflection mirror 12, as determined through initialization calibration. In this embodiment, the coupling scanning area corresponding to the fast-reflection mirror scanning extends to a maximum of ±200 μrad around the reference zero position. To further improve coupling efficiency, the normal coupling scanning area is limited to a range of ±50 μrad around the reference zero position. If the received power within this ±50 μrad range does not meet the predetermined standard, the scanning range is gradually expanded to a maximum of ±200 μrad.

[0101] When receiving optical signals from a nutating coupling device that has been initialized and calibrated using the aforementioned initialization and calibration method, it is ensured that when the reflected light spot is located at the center of the spot position detection module, the transmitted light, reflected by the nutating coupling fast reflection mirror and entering the fiber coupling adjustment module, is also located within the coupling scanning area. If the light beam fails to enter the initialized and calibrated fiber coupling area as expected, the device must be re-initialized and recalibrated to ensure that, under normal operating conditions, the device can quickly, efficiently, and stably receive spatial light from the single-mode fiber within the coupling scanning area, thereby ensuring stable operation of the communication system.

[0102] Example 2

[0103] like Figure 8 As shown, this embodiment provides a specific method for receiving free-space light into a single-mode optical fiber using the above-mentioned nutation coupling device, including:

[0104] Step b1, making the free-space light incident on the incident surface of the spectroscopic module. After being split by the spectroscopic surface, the reflected light enters the light spot position monitoring module perpendicular to the incident light, and the transmitted light enters the nutating scanning module along the direction of the incident light.

[0105] Step b2: Adjust the free-space light so that the reflected light spot remains at the center of the spot position monitoring module. At the same time, the transmitted light enters the fiber-coupled focusing mirror and the incident lens barrel through the nutating coupling fast reflection mirror, and the light spot is within the coupling scanning area.

[0106] Step b3, controlling the nutating coupling fast-reflection mirror by the fast-reflection mirror controller to scan within the coupling scanning area, so that the light spot is coupled into the optical fiber;

[0107] The coupling scanning area refers to the area with the strongest optical fiber coupling within a predetermined range near the reference zero position of the nutating coupling fast reflection mirror calibrated by initialization calibration.

[0108] When receiving free-space light, the light beam needs to be shaped before entering the optical splitter module to enhance the optical signal quality.

[0109] like Figure 6 As shown in the figure, a comparison diagram of the light spot position detected by the position detector before and after initialization calibration is shown. Figure (a) is the light spot position movement trajectory recorded by the position detector before initialization calibration. After initialization calibration, the light spot trajectory is shown in Figure (b). It can be seen that after initialization calibration, the device of the present invention can control the light spot in a certain small range near the center position of the position detector. Since the receiving optical path of the receiving optical fiber is coaxial with the receiving optical path of the position detector light spot, it can be determined that the position of the receiving optical fiber and the receiving light spot will also be controlled in a certain small range, thereby reducing the uncertainty of the nutation-coupled fast mirror in capturing the receiving light spot, and greatly improving the coupling efficiency and accuracy of the nutation scanning.

[0110] The optical fiber nutation coupling device and method provided by the present invention work in combination with a traditional laser communication terminal tracking solution, which can further reduce the tracking residual of the traditional laser communication terminal and effectively improve the communication stability of the space laser communication terminal.

[0111] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An optical fiber nutation coupling device, characterized in that: It includes a light splitting module, a light spot position monitoring module, a fiber coupling adjustment module, a nutation scanning module, a receiving fiber and a main base; The light splitting module adopts a cubic light splitting prism, and the light splitting surface of the cubic light splitting prism is fixed at a 45-degree angle with the main base. The incident light is incident on the incident surface of the light splitting module. After being split by the light splitting surface, the reflected light enters the light spot position monitoring module perpendicular to the incident light, and the transmitted light enters the nutating scanning module along the direction of the incident light. The light spot position monitoring module includes a position detection focusing mirror and a position detector, which are used to monitor the light spot position of the reflected light. The reflected light is incident on the position detector through the position detection focusing mirror. The position detection focusing mirror and the position detector are respectively connected to the main base by bolts to fasten the sliding adjustable structure, which is used to adjust the focal length of the light spot position monitoring module; The nutation scanning module includes a nutation coupling fast-reflection mirror and a fast-reflection mirror controller, wherein the fast-reflection mirror controller is used to control the nutation coupling fast-reflection mirror to perform nutation scanning in the coupling scanning area; The fiber-coupled adjustment module includes a fiber-coupled focusing lens, an incident lens barrel, a fiber flange, a three-point adjustment disk, and an L-shaped support plate. The fiber flange is provided at one end of the incident lens barrel for mounting a receiving optical fiber. The other end of the incident lens barrel passes through the vertical surface of the L-shaped support plate and the three-point adjustment disk and is inserted into the lens barrel of the fiber-coupled focusing lens. The three-point adjustment disk is mounted on the vertical surface of the L-shaped support plate. The horizontal surface of the L-shaped support plate and the fiber-coupled focusing lens are respectively connected to the main base via a bolt-fastened sliding adjustable structure for adjusting the focal length of the fiber-coupled adjustment module. The transmitted light is reflected by the nutation-coupled fast-reflecting mirror and then enters the fiber-coupled focusing mirror, and then enters the receiving optical fiber through the incident lens barrel; By initializing and calibrating the device, the light beam entering the nutation scanning module is constrained within a coupling scanning area; the coupling scanning area refers to the area with the strongest optical fiber coupling within a predetermined range near the reference zero position of the nutation coupling fast reflection mirror calibrated by initialization calibration.

2. The device according to claim 1, characterized in that It also includes a light blocking plate fixed on the outside of the gap between the nutation coupling fast reflection mirror and the fiber coupling focusing mirror, and is used to eliminate interfering light.

3. The device according to claim 1, characterized in that The position detector includes a light spot imaging sensor, a detector packaging cover and a detector window. The light spot imaging sensor and the detector window are respectively arranged at the center positions of both ends of the detector packaging cover. The end of the detector packaging cover provided with the detector window is inserted into the lens barrel of the position detection focusing lens. The sliding adjustable structure of the position detector is arranged at the corresponding positions of the detector packaging cover base and the main base. The light spot imaging sensor uses a charge-coupled device to collect light spot images in real time.

4. The device according to claim 3, characterized in that The bases of the L-shaped support plate, the fiber-coupled focusing mirror and the position detection focusing mirror are all provided with sliding adjustable structures, which are used to slide and adjust the lateral positions of the fiber-coupled adjustment module, the fiber-coupled focusing mirror and the position detection focusing mirror, respectively.

5. The device according to claim 4, characterized in that The fiber-coupled focusing mirror includes a first focusing mirror base, a first focusing mirror and a first narrow-band filter. The first focusing mirror and the first narrow-band filter are respectively arranged in the middle and one end of the lens barrel of the first focusing mirror base. The incident light enters the first focusing mirror after being filtered by the first narrow-band filter. The other end of the lens barrel is used to insert the incident lens barrel. The sliding adjustable structure of the fiber-coupled focusing mirror is arranged at corresponding positions of the main base and the first focusing mirror base.

6. The device according to claim 1, characterized in that The nutation-coupled quick-reflection mirror comprises a quick-reflection mirror base, a quick-reflection mirror pedestal, a quick-reflection mirror magnifying structure, piezoelectric ceramics, a lens seat, a flexible hinge, a reflective lens and a pressure cover.

7. The device according to claim 6, characterized in that The quick-reflection mirror base is an L-shaped panel, the horizontal surface of the L-shaped panel is fixed to the upper surface of the quick-reflection mirror controller, and the quick-reflection mirror base is fixed to the vertical surface of the L-shaped panel by bolts fastening the sliding adjustable structure. The quick-reflection mirror magnifying structure includes four triangular connecting rods with identical structures, the horizontal rods of the triangular connecting rods are all fixed to the quick-reflection mirror base, and the distances from the center of the bottom surface of the quick-reflection mirror base are all equal; the diagonal support rods of the triangular connecting rods form an acute angle with the horizontal rods, the piezoelectric ceramics are arranged between the horizontal rods and the diagonal support rods of the triangular connecting rods, the lens seat is installed on the top of the four diagonal support rods, and the reflective lens is installed on the lens seat via a flexible hinge. The pressure cover is an annular structure and is installed on the top of the quick-reflection mirror base to encapsulate the quick-reflection mirror magnifying structure, piezoelectric ceramics, lens seat, flexible hinge and reflective lens in the quick-reflection mirror base.

8. The device according to claim 7, characterized in that The method for initializing and calibrating the device is: Step a1, controlling the incident light to be incident on the incident surface of the light splitting module, so that the reflected light enters the light spot position monitoring module perpendicular to the incident light, and the transmitted light enters the nutating scanning module along the direction of the incident light; Step a2, adjusting the positions of the position detection focusing mirror and the position detector by tightening the sliding adjustable structure with the bolts, so that the reflected light is focused on the center position of the position detector and remains stationary; Step a3, setting the nutation-coupled fast-reflection mirror at zero position and adjusting the position of the receiving optical fiber on the vertical plane by using the L-shaped support plate and the three-point adjustment plate so that the incident light enters the receiving optical fiber and the optical power reaches the maximum value; Step a4, adjusting the focal length by changing the front and rear position of the incident lens barrel extending into the fiber-coupled focusing lens barrel and the three-point adjustment dial to maximize the optical power incident on the receiving optical fiber; Step a5: Adjust the position of the nutating coupling fast-reflection mirror on the vertical plane so that the incident light enters the receiving optical fiber and the received optical power reaches a maximum value. Record the current position of the nutating coupling fast-reflection mirror as the ground reference zero position. Step a6, fixing the sliding adjustable structures so that the modules are fixed, determining the coupling scanning area of ​​the nutating coupling fast-reflection mirror, and setting it through the fast-reflection mirror controller; Step a7: After the device is launched into orbit, the nutation-coupled quick-reflection mirror is fine-tuned again by the quick-reflection mirror controller according to the ground reference zero position so that the optical power incident on the receiving optical fiber reaches the maximum. The position of the nutation-coupled quick-reflection mirror at this time is set as the onboard reference zero position.

9. The device according to any one of claims 1 to 8, characterized in that The specific method of the device receiving free-space light into the optical fiber includes: Step b1, making the free-space light incident on the incident surface of the spectroscopic module. After being split by the spectroscopic surface, the reflected light enters the light spot position monitoring module perpendicular to the incident light, and the transmitted light enters the nutating scanning module along the direction of the incident light. Step b2: Adjust the free-space light so that the reflected light spot remains at the center of the spot position monitoring module. At the same time, the transmitted light enters the fiber-coupled focusing mirror and the incident lens barrel through the nutating coupling fast reflection mirror, and the light spot is within the coupling scanning area. Step b3, controlling the nutating coupling fast-reflection mirror by the fast-reflection mirror controller to scan within the coupling scanning area, so that the light spot is coupled into the optical fiber; The coupling scanning area refers to the area with the strongest optical fiber coupling within a predetermined range near the reference zero position of the nutating coupling fast reflection mirror calibrated by initialization calibration.

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