Special optical fiber bundle, optical receiving system based on special optical fiber bundle and laser radar based on optical receiving system

Abstract

The invention discloses a special optical fiber bundle, a light receiving system based on the special optical fiber bundle and a laser radar based on the light receiving system, and relates to the technical field of airborne water depth measurement laser radars, the special optical fiber bundle comprises an input end, a first output end and a second output end; the input end is composed of a central multimode optical fiber and an annular multimode optical fiber bundle surrounding the central optical fiber; the first output end is a central multimode optical fiber; and the second output end is a circular optical fiber bundle formed by combining the annular multimode optical fiber bundles in the input end. The special optical fiber bundle provided by the invention can separate a composite light echo signal into a large view field part and a small view field part, and can replace a sub-view-field light reflector.

Description

Technical Field

[0001] The present application relates to the technical field of airborne bathymetric lidar, and particularly to a special optical fiber bundle, an optical receiving system based on the special optical fiber bundle, and a lidar based on the optical receiving system. Background Art

[0002] The airborne bathymetric lidar is installed on a manned aircraft (flight altitude 200 - 1000 m) or an unmanned aircraft (flight altitude 10 - 50 m) for flight operations. The emitted pulsed laser beam performs point-line scanning coverage on the set water surface and bottom areas from top to bottom. The optical echo signals reflected diffusely from the water surface and bottom are received, stored, and processed by the optical receiving system to form a point cloud map, and finally a three-dimensional topographic map of the water surface and bottom is obtained.

[0003] For each pulsed laser spot emitted by the lidar, its optical receiving system will receive a composite optical echo signal containing the water surface echo and the bottom echo. Due to the relatively large absorption and scattering of the light beam by natural environment water bodies such as rivers, lakes, and oceans, the bottom optical echo signal is 10 3 ~10 5 times smaller than the water surface optical echo signal, and may also be much smaller than the scattered optical echo caused by water body scattering. In order to avoid the bottom optical echo signal being submerged or difficult to collect, the optical receiving system of the airborne lidar usually adopts a structure of "main optical receiving mirror + split field optical reflector + two optical receiving components with large and small fields of view".

[0004] However, this traditional and typical optical receiving system for bathymetry with large and small fields of view is limited by the overall machine parameter design. It requires that the relevant optical parts such as the small field of view optical receiving component be arranged coaxially with the main optical receiving mirror, and the relevant optical parts such as the large field of view optical receiving component be arranged perpendicular to the main optical receiving mirror. The entire optical axis structure occupies a certain length and space, and is also not conducive to the lightweight and miniaturization of the entire airborne bathymetric lidar. Summary of the Invention

[0005] The purpose of the present application is to provide a special optical fiber bundle, an optical receiving system based on the special optical fiber bundle, and a lidar based on the optical receiving system, which can replace the split field optical reflector in the optical receiving system with the special optical fiber bundle to achieve the lightweight and miniaturization of the entire airborne bathymetric lidar.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] In the first aspect, the present application provides a special optical fiber bundle, including: an input end, a first output end, and a second output end;

[0008] The input end is composed of a central multimode optical fiber and a ring multimode optical fiber bundle surrounding the central optical fiber;

[0009] The first output end is a central multimode optical fiber; the second output end is a circular optical fiber bundle synthesized from the annular multimode optical fiber bundles in the input ends.

[0010] Optionally, the central multimode optical fiber is a single multimode optical fiber or a multimode optical fiber bundle.

[0011] Optionally, when the central multimode optical fiber is a single multimode optical fiber, the core diameter of the multimode optical fiber ranges from 200 to 500 µm.

[0012] Optionally, when the central multimode optical fiber is a multimode optical fiber bundle, the core diameter of each multimode optical fiber in the multimode optical fiber bundle ranges from 100 to 300 µm; the core diameters of each multimode optical fiber in the multimode optical fiber bundle are the same.

[0013] Optionally, the core diameter of each multimode optical fiber in the annular multimode optical fiber bundle ranges from 100 to 300 µm; the core diameters of each multimode optical fiber in the annular multimode optical fiber bundle are the same.

[0014] Optionally, the multimode optical fibers in the central multimode optical fiber and the annular multimode optical fiber bundle are made of quartz glass material.

[0015] In a second aspect, the present application provides an optical receiving system based on a special optical fiber bundle, including: an optical receiving primary mirror, a special optical fiber bundle, a small field of view optical receiving component, and a large field of view optical receiving component;

[0016] The center of the input end of the special optical fiber bundle is located at the focus of the optical receiving primary mirror;

[0017] The first output end of the special optical fiber bundle is connected to the small field of view optical receiving component;

[0018] The second output end of the special optical fiber bundle is connected to the large field of view optical receiving component.

[0019] Optionally, the small field of view optical receiving component sequentially includes a first collimating mirror, a first filter, a first focusing mirror, and a first photodetector along the optical path direction.

[0020] Optionally, the large field of view optical receiving component sequentially includes a second collimating mirror, a second filter, a second focusing mirror, and a second photodetector along the optical path direction.

[0021] In a third aspect, the present application provides a lidar based on the optical receiving system, including: an optical receiving system;

[0022] The optical receiving system uses a special optical fiber bundle to replace the split field of view reflecting mirror; the first output end of the special optical fiber bundle is coupled to the optical receiving component of the small field of view channel; the second output end of the special optical fiber bundle is coupled to the optical receiving component of the large field of view channel.

[0023] According to the specific embodiments provided in this application, the following technical effects are disclosed in this application:

[0024] This application provides a special optical fiber bundle, including: an input end, a first output end, and a second output end; the input end is composed of a central multimode optical fiber and a ring-shaped multimode optical fiber bundle surrounding the central optical fiber; the first output end is the central multimode optical fiber; the second output end is a circular optical fiber bundle synthesized from the ring-shaped multimode optical fiber bundle in the input end. The special optical fiber bundle provided by this application can separate the composite optical echo signal into two parts with large and small fields of view, and can replace the split-field optical mirror, thereby enabling the lightweight and miniaturization of the entire airborne bathymetric lidar. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a structural diagram of the special optical fiber bundle provided in an embodiment of this application.

[0027] Figure 2 It is a schematic diagram of a bathymetric optical receiving system in which the special optical fiber bundle provided in an embodiment of this application replaces the split-field reflector.

[0028] Figure 3 It is a schematic diagram of an existing optical system provided in an embodiment of this application.

[0029] Figure 4 It is a simulation diagram of a water surface detection receiving optical system provided in an embodiment of this application.

[0030] Figure 5 It is a simulation diagram of the receiving field of view of a water surface detection receiving optical system provided in an embodiment of this application.

[0031] Figure 6 It is a simulation diagram of a bottom detection receiving optical system provided in an embodiment of this application.

[0032] Figure 7 It is a receiving field of view diagram of a bottom detection receiving optical system provided in an embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0034] After the composite optical echo signal is received and focused by the main optical receiving mirror, it is separated into two parts: a small field of view of 0 to 5 mrad and a large field of view of 5 to 35 mrad. Among them, the amplitude of the optical echo signal in the small field of view accounts for one-fifth or less of the total amplitude. In the shallow water area, the optical receiving component in the small field of view channel can collect the water surface echo and extremely weak bottom echo; while the amplitude of the optical echo signal in the large field of view accounts for four-fifths or more of the total amplitude, and the optical receiving component in the large field of view channel is designed to avoid the water surface optical echo and only receive the bottom optical echo in the deep water area.

[0035] The separation of the composite optical echo signal into two parts, a large field of view and a small field of view, is based on a field-of-view splitting optical mirror (i.e., an optical plane mirror with an elliptical hole in the center). The field-of-view splitting optical mirror is located at the focus of the main optical receiving mirror, the center of the central elliptical hole coincides with the focus of the main mirror, and the major axis of the central elliptical hole is placed at 45° with the main optical axis of the optical receiving system. The composite optical echo signal is focused by the main optical receiving mirror. Among them, the optical echo signal in the small field of view forms a circular spot of фa on the focal plane of the main mirror and completely passes through the central elliptical hole of the field-of-view splitting optical mirror (the elliptical hole is designed with a minor axis a and a major axis of 1.414a) and enters the coaxial small field-of-view optical receiving component (for measuring data on the water surface and shallow water area); the optical echo signal in the large field of view forms an annular circular spot with an inner diameter of фa and an outer diameter of фb on the focal plane of the main mirror, which is completely outside the central elliptical hole of the field-of-view splitting optical mirror and is reflected and enters the large field-of-view optical receiving component perpendicular to the optical axis (for measuring data in the deep water area).

[0036] The size of the central elliptical hole (minor axis a, major axis 1.414a) of the field-of-view splitting optical mirror and the size of the elliptical shape (minor axis b, major axis 1.414b) are related to the design parameters of the entire optical receiving system.

[0037] This traditional and typical optical receiving system for measuring water depth with two fields of view, a large one and a small one, is limited by the design of the overall machine parameters, requiring that the relevant optical parts such as the optical receiving component in the small field of view be arranged coaxially with the main optical receiving mirror, and the relevant optical parts such as the optical receiving component in the large field of view be arranged perpendicular to the main optical receiving mirror.

[0038] The purpose of the present application is to provide a special optical fiber bundle, an optical receiving system based on the special optical fiber bundle, and a lidar based on the optical receiving system, which can replace the field-of-view splitting optical mirror in the optical receiving system with the special optical fiber bundle to realize the lightweight and miniaturization of the entire airborne water depth measurement lidar.

[0039] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Embodiment 1

[0041] As Figure 1 shown, this embodiment provides a special optical fiber bundle, including: an input end, a first output end, and a second output end;

[0042] The input end is composed of a central multimode optical fiber and an annular multimode optical fiber bundle surrounding the central optical fiber;

[0043] The first output end is a central multimode optical fiber; the second output end is a circular optical fiber bundle formed by synthesizing the annular multimode optical fiber bundle in the input end.

[0044] Among them, the central multimode optical fiber is a single multimode optical fiber or a multimode optical fiber bundle. When the central multimode optical fiber is a single multimode optical fiber, the core diameter range of the multimode optical fiber is 200 - 500 µm. When the central multimode optical fiber is a multimode optical fiber bundle, the core diameter range of each multimode optical fiber in the multimode optical fiber bundle is 100 - 300 µm; the core diameters of each multimode optical fiber in the multimode optical fiber bundle are the same. The core diameter range of each multimode optical fiber in the annular multimode optical fiber bundle is 100 - 300 µm; the core diameters of each multimode optical fiber in the annular multimode optical fiber bundle are the same. The multimode optical fibers in the central multimode optical fiber and the annular multimode optical fiber bundle are made of quartz glass material.

[0045] Specifically, the special optical fiber bundle is an optical fiber bundle used to replace the split-field mirror, Figure 1 in which (a) is the input end of the special optical fiber bundle. The center of the circular end face is the central optical fiber 101 with a diameter of фa (a circular optical fiber bundle composed of one or several, dozens of optical fibers with a core diameter of 100 µm - 200 µm), and the slanted area of the annular end face is an annular optical fiber bundle 102 with an inner diameter of фa - outer diameter of фb composed of dozens (or hundreds) of optical fibers with a core diameter of ф100 - 300 µm. Figure 1 In (c) is the output end of the special optical fiber bundle, where end A is the first output end, that is, the central optical fiber (bundle) 101 - A, and end B is the second output end (the circular optical fiber bundle synthesized from the slanted area of the annular end face optical fiber bundle) 102 - B. Figure 1 In (b) is the overall structure schematic diagram of the special optical fiber bundle.

[0046] Among them, in this embodiment, the optical fibers that make up the special optical fiber bundle use commercially available large numerical aperture (NA = 0.22, 0.33, 0.47, 0.66 optional), large core diameter and thin cladding optical fibers (core diameter = ф105 - 500µm optional). The selection of the numerical aperture and core diameter of the optical fiber and the number of optical fibers is related to the design parameters of the main optical receiver mirror, large and small fields of view, etc. of the entire lidar optical receiving system. The production of the special optical fiber can be completed using conventional and mature optical processing techniques, and the production cost is comparable to that of a high-energy laser mirror with the same aperture.

[0047] Commercially available optical fibers have only three low-loss wavelength "windows" for long-distance optical signal transmission: 850nm, 1310nm, and 1550nm. According to the overall design requirements of the entire machine, the special optical fiber bundle usually has a length of 0.2 - 0.5 meters, and the attenuation of the 532nm optical signal outside the low-loss wavelength "window" during transmission in the special optical fiber bundle can be ignored.

[0048] Embodiment Two

[0049] This embodiment provides an optical receiving system based on a special optical fiber bundle, including: a main optical receiver mirror, a special optical fiber bundle, a small field of view optical receiving component, and a large field of view optical receiving component;

[0050] The center of the input end of the special optical fiber bundle is located at the focus of the main optical receiver mirror;

[0051] The first output end of the special optical fiber bundle is connected to the small field of view optical receiving component;

[0052] The second output end of the special optical fiber bundle is connected to the large field of view optical receiving component.

[0053] As Figure 2 shown, the water depth measurement optical receiving system that separates the large and small field of view optical echo signals based on the special optical fiber bundle is as Figure 2 shown. The center of the input end of the special optical fiber bundle 200 is located at the focus of the main optical receiver mirror 201 (the center of the input end face coincides with the focal plane). The optical echo signal reflected diffusely by the target is received and focused by the main optical mirror 201. Among them, the small field of view optical echo signal is focused and coupled into the central optical fiber (bundle), and enters the collimating mirror 2021, filter 2022, and converging mirror 2023 of the small field of view optical receiving component 202 through the output end 200-A, and finally reaches the photodetector 2024. The large field of view optical echo signal is focused and coupled into the annular optical fiber bundle, and enters the collimating mirror 2031, filter 2032, and converging mirror 2033 of the large field of view optical receiving component 203 through the output end 200-B, and finally reaches the photodetector 2034.

[0054] The main optical receiver mirror, the small field of view optical receiving component, and the large field of view optical receiving component are relatively independent of each other, and together with the special optical fiber bundle, they constitute the water depth measurement optical receiving system.

[0055] Embodiment III

[0056] This embodiment provides a lidar based on an optical receiving system, including: an optical receiving system;

[0057] The optical receiving system uses a special optical fiber bundle to replace the split field-of-view mirror; the first output end of the special optical fiber bundle is coupled to the optical receiving component of the small field-of-view channel; the second output end of the special optical fiber bundle is coupled to the optical receiving component of the large field-of-view channel.

[0058] Among them, the rest of the lidar are some existing off-the-shelf components.

[0059] 1) Laser

[0060] Lidar usually uses a laser as the light source to emit a laser beam. This part can use existing semiconductor lasers or fiber lasers, which have been widely used in various lidar systems and have characteristics such as high stability, high power, and low noise.

[0061] 2) Scanning system

[0062] The scanning system is used to change the direction of the laser beam to achieve scanning of different areas. This can be achieved through technologies such as mechanical scanning, optical phased array, or microelectromechanical systems (MEMS). These technologies are all existing and have been widely used in the lidar field.

[0063] 3) Signal processing system

[0064] The signal processing system is used to receive and process the signals collected by the optical receiving system. This part may include components such as a high-speed data acquisition module (AD), a digital signal processor (DSP), or a field-programmable gate array (FPGA). These components can efficiently convert optical signals into digital signals and perform processing such as filtering, amplification, and parsing to extract useful information.

[0065] 4) Power management system

[0066] The power management system is responsible for providing a stable power supply for each component of the lidar. This may include components such as a power converter, a voltage regulator, and a battery. These components are all existing and can be selected and configured according to the specific requirements of the lidar.

[0067] Please note that the above are only examples of some existing off-the-shelf components that may be used in the lidar and do not constitute a complete lidar system. An actual lidar system may include more components and subsystems.

[0068] In addition, this application also provides an example of a design scheme for the receiving optical system, which can be specifically as follows:

[0069] 1. Receiver optical system design:

[0070] 1.1 Receiver optical system scheme design:

[0071] Design requirements: The optical receiving aperture is about 100 mm, the optical receiving field of view is 0 - 21 mrad, of which the small field of view is 0 - 5 mrad and the large field of view is 5 - 21 mrad. Shelf products should be selected for optical lenses as much as possible. The photosensitive surface of the water surface optical detector is Φ0.5 mm, and the photosensitive surface of the underwater optical detector is Φ8 mm.

[0072] The receiver optical system mainly completes the reception of the ranging laser echo, improves the reception efficiency, and effectively differentiating the water surface and underwater echoes is the design key point of the receiver optical system. In order to meet the design requirements of miniaturization, lightweight and low power consumption of the receiver optical system, considering the advantages and disadvantages of various optical path forms and the actual requirements of this application, this optical system uses a field lens to distinguish the water surface and underwater echoes, as Figure 3 shown.

[0073] The optical system uses a Keplerian transmissive long optical path with a main mirror diameter of 110 mm. The link includes a water surface detection link and an underwater detection link. The water surface detection link and the underwater detection link are split by a field lens. The field lens is a reflecting mirror with a central hole (i.e., a split field-of-view mirror), which is located at the focus of the main mirror, facilitating reducing the size of the hole and thus reducing the reception loss of the underwater detection link.

[0074] 1.2 Analysis of components of the optical receiving system:

[0075] The optical receiving system mainly consists of components such as a Keplerian beam expander telescope group, a field lens, and a focusing lens.

[0076] The Keplerian beam expander telescope group consists of an aspherical main lens and a spherical collimating lens. The effective clear aperture of the optical receiving main mirror is selected as 110 mm, the focal length is 200 mm, the effective clear aperture of the collimating lens is 20 mm, and the focal length is 25 mm, forming a Keplerian telescope group with an expansion ratio of 8 with the main lens. The effective clear aperture of the water surface focusing lens is 20 mm, the focal length is 12.5 mm, and the effective focal length after combination with the telescope group is about 100 mm. The effective clear aperture of the underwater focusing lens is 20 mm, the focal length is 50 mm, and the effective focal length after combination with the telescope group is about 400 mm. The effective clear aperture of the field lens is elliptical, with its outer dimension size of (major axis) 5.66 × (minor axis) 4 mm, and the middle aperture size of (major axis) 1.97 × (minor axis) 1.39 mm. Its surface is coated with a silver film and a protective silver film.

[0077] 1.3 Simulation of the optical receiving system:

[0078] According to the schematic diagram of the receiving optical system and the above design parameter analysis, the receiving optical system can be simulated using the optical design software Zemax.

[0079] Since the photosensitive surface of the water surface detector is relatively small, about 0.5 mm, and the receiving field of view requirement is ≤5 mrad. After optical simulation, the aperture of the water surface detection receiving optical system is 110 mm and the focal length is about 101 mm. Then the receiving field of view of the water surface detection optical system is 0.5 mm / 101 mm = 4.95 mrad, meeting the requirement that the receiving field of view of the water surface detection receiving optical system ≤5 mrad. As Figure 4 、 5 shown, they are the simulation diagram of the water surface detection receiving optical system and the simulation diagram of the receiving field of view.

[0080] Since the photosensitive surface of the water bottom detector is relatively large, about φ8 mm, and the receiving field of view requirement is 5 - 21 mrad. After optical simulation, the aperture of the water surface detection receiving optical system is φ110 mm and the focal length is about 426 mm. Then the receiving field of view of the water surface detection optical system is 8 mm / 426 mm = 18.8 mrad, the size of the elliptical hole in the center of the field lens is (major axis) 1.97 × (minor axis) 1.39 mm, and the focal length of the primary mirror is 200 mm. The field of view angle of the reflected light of this field lens ≥1.39 mm / 200 mm = 6.9 mrad. Then the receiving field of view of the water bottom detector is 6.9 - 18.8 mrad, meeting the requirement that the receiving field of view of the water bottom detection receiving optical system is 5 - 21 mrad. As Figure 6 、 7 shown, they are the simulation diagram of the water bottom detection receiving optical system and the simulation diagram of the receiving field of view.

[0081] 1.4 Special fiber optic bundle replaces the field lens (field-of-view splitting mirror):

[0082] Designed according to the parameters in the optical receiving system of this example, the elliptical outer dimension of the field lens is (major axis) 5.66 × (minor axis) 4 mm, and the size of the central elliptical aperture is (major axis) 1.97 × (minor axis) 1.39 mm. Then the parameters selected for the production of the input end of the special fiber optic bundle are: the diameter of the central fiber optic bundle Φ1.39 mm, the inner diameter of the fiber optic bundle surrounding the central fiber optic bundle Φ1.39 mm, and the outer diameter Φ4 mm.

[0083] In summary, the present application has the following technical effects:

[0084] (1) Benefiting from the "relay" function of the special fiber optic bundle, the primary mirror, the small field-of-view optical receiving component, and the large field-of-view optical receiving component are relatively independent of each other and can be installed, adjusted, and reassembled separately. This separated design makes the assembly and adjustment process simpler and reduces the technical difficulty.

[0085] (2) The bendability of the special optical fiber bundle allows for flexible design of the length and installation position of the optical fiber bundle according to the requirements of the whole machine. Therefore, as independent units, the large field of view and small field of view optical receiving components do not need to have their optical axes coaxial with the main optical receiving mirror, nor do they have to be perpendicular to the optical axis of the main mirror. They can be flexibly installed at any position inside the whole machine, thus optimizing the utilization of the internal space of the lidar whole machine.

[0086] (3) The optical echo signals of the large field of view and small field of view are respectively coupled into the optical detector from the output end B and end A of the special optical fiber bundle. Drawing on the conventional process of commercial optical fiber collimators in the field of optical communication, the selection of optical collimating mirrors, optical filters and optical focusing mirrors with a smaller clear aperture helps to reduce costs and achieve miniaturization of the system.

[0087] (4) Due to the limitation of the numerical aperture in optical fiber transmission, optical signals with a field of view angle larger than that of the optical fiber cannot be transmitted in the optical fiber. As long as the numerical aperture design of the main optical receiving mirror matches the numerical aperture selection of the special optical fiber bundle, and the large field of view and small field of view optical receiving components adopt a barrel-closed extinction structure, the entire optical receiving system will not be interfered by any stray light outside the set optical receiving field of view (i.e., a field of view larger than 35 mrad).

[0088] (5) The lightweight and volume reduction of the large field of view and small field of view optical receiving components contribute to the lightweight and miniaturization of the lidar whole machine.

[0089] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0090] Specific examples are used in this article to elaborate on the principles and implementation manners of this application. The descriptions of the above embodiments are only used to help understand the method and its core idea of this application; at the same time, for those of ordinary skill in the art, based on the idea of this application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to this application.

Claims

1. A special optical fiber bundle, characterized in that: include: an input terminal, a first output terminal, and a second output terminal; The input end is composed of a central multimode optical fiber and an annular multimode optical fiber bundle surrounding the central optical fiber; The first output end is a central multimode optical fiber; the second output end is a circular optical fiber bundle synthesized from the annular multimode optical fiber bundle in the input end.

2. A special optical fiber bundle according to claim 1, characterized in that: The central multimode optical fiber is a multimode optical fiber or a multimode optical fiber bundle.

3. A special optical fiber bundle according to claim 2, characterized in that: When the central multimode optical fiber is a multimode optical fiber, the core diameter of the multimode optical fiber ranges from 200 to 500 μm.

4. A special optical fiber bundle according to claim 2, characterized in that: When the central multimode optical fiber is a multimode optical fiber bundle, the core diameter of each multimode optical fiber in the multimode optical fiber bundle ranges from 100 to 300 µm; and the core diameter of each multimode optical fiber in the multimode optical fiber bundle is the same.

5. A special optical fiber bundle according to claim 1, characterized in that: The core diameter of each multimode optical fiber in the annular multimode optical fiber bundle ranges from 100 to 300 μm; the core diameter of each multimode optical fiber in the annular multimode optical fiber bundle is the same.

6. A special optical fiber bundle according to claim 1, characterized in that: The central multimode optical fiber and the multimode optical fibers in the annular multimode optical fiber bundle are made of quartz glass material.

7. A light receiving system based on a special optical fiber bundle, characterized in that: include: A light receiving primary mirror, a special optical fiber bundle, a small field of view light receiving assembly, and a large field of view light receiving assembly; The center of the input end of the specially made fiber bundle is located at the focal point of the light receiving primary mirror; The first output end of the specially made optical fiber bundle is connected to the small field of view light receiving component; The second output end of the specially made optical fiber bundle is connected to a large-field-of-view light receiving component.

8. The optical receiving system based on a special optical fiber bundle according to claim 6, characterized in that: The small-field-of-view light receiving assembly comprises a first collimator, a first filter, a first focusing mirror and a first light detector in sequence along the light path direction.

9. The optical receiving system based on a special optical fiber bundle according to claim 6, characterized in that: The large-field-of-view light receiving assembly comprises a second collimator, a second filter, a second focusing mirror and a second light detector in sequence along the light path direction.

10. A laser radar based on a light receiving system, characterized in that: include: Light receiving system; The optical receiving system uses a special optical fiber bundle to replace the field-of-view reflector; The first output end of the specially made optical fiber bundle is coupled to the light receiving component of the small field of view channel; The second output end of the special optical fiber bundle is coupled to the light receiving component of the large field of view channel.

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