A laser receiving device adaptable to atmospheric turbulence

Abstract

This invention provides a laser receiving device that can adapt to atmospheric turbulence, featuring efficient and stable reception of optical signals. Through a cooperative receiving architecture of central fiber coupling and peripheral ring detection, it reduces sensitivity to beam drift and improves the spatial tolerance of optical coupling. Combined with a dynamic decision feedback mechanism based on real-time optical power monitoring, it can quickly track light intensity fluctuations and adaptively adjust the decision threshold, thereby maintaining a low bit error rate throughout the dynamic range. At the same time, it eliminates the need for complex mechanical tracking or a large aperture averaging system, achieving a balance between high performance, high robustness, and compact structure.

Description

Technical Field

[0001] This invention relates to the field of free-space laser communication and photoelectric detection technology, and in particular to a laser receiving device that can adapt to atmospheric turbulence. Background Technology

[0002] Free-space laser communication (FSO), as an important development direction in the field of wireless communication, has shown broad application prospects in military, civilian, and commercial fields due to its outstanding advantages such as high bandwidth, convenient deployment, and no need for spectrum licensing. This technology transmits data through a laser beam in the atmosphere, overcoming the spectrum limitations of traditional radio frequency communication, and is particularly suitable for scenarios such as long-distance communication, emergency communication, and satellite links. In recent years, with the advancement of optoelectronic devices and signal processing technologies, the transmission rate and reliability of FSO systems have been continuously improved, making it a key supplementary technology for next-generation communication networks.

[0003] However, free-space laser communication (FSO) faces severe challenges from atmospheric turbulence in practical applications. Caused by uneven temperature, pressure, and humidity, atmospheric turbulence leads to random fluctuations in the refractive index along the laser transmission path, resulting in adverse effects such as intensity flicker, beam drift, and phase distortion. These effects significantly degrade the receiver signal-to-noise ratio (SNR) and increase the system bit error rate, severely hindering the practical application of FSO. Traditional FSO receivers typically use small-core single-mode fiber or a single avalanche photodiode (APD) for optical coupling. Such solutions are extremely sensitive to beam alignment accuracy; if turbulence causes the beam center to deviate from the receiving fiber core, the coupling efficiency drops sharply, rapidly depleting the system's link margin. To reduce alignment difficulty, existing technologies attempt to use large-core multimode fiber or lens arrays for coupling. However, the inherent modal dispersion of multimode fiber limits the system's transmission bandwidth, while complex optical structures like lens arrays increase system size and significantly enhance the complexity of assembly and calibration. On the other hand, atmospheric scintillation can cause dynamic fluctuations in received optical power exceeding 20 dB. Receivers with fixed decision thresholds perform poorly in this environment: the bit error rate rises sharply during deep fading, while waveform distortion occurs due to front-end saturation when the signal is too strong. Furthermore, existing compensation schemes, such as automatic gain control (AGC) amplifiers or variable optical attenuators (VOAs), can mitigate power fluctuations to some extent, but their electrical gain adjustment range is limited, and their response speed is often insufficient to track rapid changes in turbulence. More importantly, these methods can only perform post-stage compensation in the electrical domain and cannot fundamentally solve the signal energy loss caused by beam drift coupling mismatch at the physical layer.

[0004] Therefore, the current technology system still lacks a receiving solution that can simultaneously address the dual challenges of spatial coupling tolerance and power dynamic adaptability. The industry urgently needs a new type of laser receiving device that can simultaneously achieve wide field of view, low loss optical signal capture and coupling, as well as intelligent level decision and stable output for wide dynamic range signals in complex turbulent channels, thereby improving the reliability and environmental adaptability of free space laser communication systems. Summary of the Invention

[0005] The purpose of this invention is to provide a laser receiving device that can adapt to atmospheric turbulence, so as to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides a laser receiving device adaptable to atmospheric turbulence, comprising an optomechanical system, a large-core multimode fiber, a ring detector, a microlens, a large photosensitive surface APD, a first transimpedance amplifier, a second transimpedance amplifier, an optical power detection module, a dynamic decision level module, a limiting amplification module, and a standard amplitude signal output module. The optomechanic is used to receive and initially focus the incident laser beam; The large-core multimode fiber is positioned at the center of the focusing path of the optical engine. Its input end receives the laser center light signal after being focused by the optical engine, and its output end is connected to the input end of the microlens. The ring detector is a Si-based PIN-ring detector, which is arranged coaxially around the outer periphery of the large-core multimode fiber. Its input end receives the laser edge light signal that has not entered the large-core multimode fiber after being focused by the optomechanical system, and its output end is connected to the input end of the optical power detection module. The microlens is disposed between the output end of the large-core multimode fiber and the large photosensitive surface APD, and is used to focus the light emitted from the fiber onto the photosensitive surface of the large photosensitive surface APD. The output terminal of the large photosensitive surface APD is connected to the input terminal of the first transimpedance amplifier; The output terminal of the first transimpedance amplifier is connected to the input terminal of the second transimpedance amplifier; The output of the second transimpedance amplifier is connected to the first input of the dynamic decision level module; The output terminal of the optical power detection module is connected to the second input terminal of the dynamic decision level module; The output of the dynamic decision level module is connected to the input of the limiting amplification module; The output terminal of the limiting amplification module is connected to the input terminal of the standard amplitude signal output module; The standard amplitude signal output module is used to output a signal with stable amplitude that conforms to the standard interface level.

[0007] Preferably, the large-core multimode optical fiber is positioned inside the central hole of the zirconia ceramic ferrule; an AlN-ZrO2 composite transition layer is provided between the outer cylindrical surface of the zirconia ceramic ferrule and the ring detector, the thermal expansion coefficient of the AlN-ZrO2 composite transition layer is between that of zirconia and silicon, and a gradient matching interface is formed with the inner diameter of the ferrule and the detector ring through low-temperature co-firing or thick film process.

[0008] Preferably, the ring detector has a circular or square ring structure and is coaxially arranged with the large-core multimode fiber; it is used to receive only the laser edge light signal that has not entered the large-core multimode fiber after being focused by the optomechanical system, and convert the edge light signal into a corresponding analog electrical signal and transmit it to the optical power detection module.

[0009] Preferably, the microlens focuses the central optical signal output from the large-core multimode fiber onto the photosensitive surface of the large photosensitive surface APD; the photosensitive diameter of the large photosensitive surface APD is 50 μm, which is used to complete high-speed photoelectric conversion.

[0010] Preferably, the first transimpedance amplifier is used to convert the weak current signal output by the large photosensitive surface APD into a primary voltage signal and provide low-noise, high-gain front-end amplification.

[0011] Preferably, the second transimpedance amplifier is used to further amplify and compensate the bandwidth of the primary voltage signal output by the first transimpedance amplifier, so as to improve the signal amplitude and optimize the signal-to-noise ratio.

[0012] Preferably, the optical power detection module is used to integrate, filter and quantize the analog electrical signal output by the ring detector, acquire laser edge optical power information in real time, and send the power indication voltage to the dynamic decision level module.

[0013] Preferably, the dynamic decision level module is used to adaptively adjust the decision threshold level according to the power indication voltage provided by the optical power detection module, and to make a threshold decision on the data signal from the second transimpedance amplifier.

[0014] Preferably, the limiting amplification module is used to limit and differentially amplify the digital signal output by the dynamic decision level module, eliminate residual amplitude fluctuations, and provide a constant output swing.

[0015] Preferably, the standard amplitude signal output module employs a level converter and an output buffer, and the output signal conforms to the LVDS or PECL standard interface specification.

[0016] The present invention achieves the following beneficial technical effects compared to the prior art: This invention provides a laser receiving device adaptable to atmospheric turbulence, characterized by high efficiency and stable optical signal reception. Through a cooperative receiving architecture of central fiber coupling and peripheral ring detection, it reduces sensitivity to beam drift and improves the spatial tolerance of optical coupling. Combined with a dynamic decision feedback mechanism based on real-time optical power monitoring, it can quickly track light intensity fluctuations and adaptively adjust the decision threshold, thereby maintaining a low bit error rate throughout the dynamic range. At the same time, it eliminates the need for complex mechanical tracking or a large aperture averaging system, achieving a balance between high performance, high robustness, and compact structure. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the structure of the laser receiving device that can adapt to atmospheric turbulence provided by the present invention. Detailed Implementation

[0019] The serial numbers assigned to components in this document, such as "first," "second," etc., are merely for distinguishing the described objects and have no sequential or technical meaning. Unless otherwise specified, the terms "connection" and "linkage" used in this application include both direct and indirect connections (linkages). In the description of this invention, it should be understood that the terms "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0020] In this invention, unless otherwise explicitly specified and limited, the first feature above or below the second feature may be in direct contact with the first feature, or indirect contact via an intermediate medium. Furthermore, "above," "over," and "on top" of the first feature may mean the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "beneath" of the first feature may mean the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The purpose of this invention is to provide a laser receiving device that can adapt to atmospheric turbulence, so as to solve the problems existing in the prior art.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1: Please see Figure 1 The laser receiving device adapted to atmospheric turbulence provided by this invention mainly includes an optomechanical system 1, a large-core multimode fiber 2, a ring detector 3, a microlens 4, a large photosensitive surface APD 5, a first transimpedance amplifier 6, a second transimpedance amplifier 7, an optical power detection module 8, a dynamic decision level module 9, a limiting amplification module 10, and a standard amplitude signal output module 11. These components, through precise optomechanical integration and signal chain design, jointly achieve efficient and stable reception of laser signals under atmospheric turbulence conditions.

[0025] Specifically, the optomechanical system 1 employs a multi-lens assembly structure to receive incident laser light from free space and achieve layer-by-layer focusing. The optomechanical system 1 first uses a front objective lens to initially focus the laser signal transmitted through the atmosphere, then performs a second, precise focusing through the internal lens assembly, ultimately stabilizing the laser signal near its focal plane. The optomechanical system 1 features high light transmittance and resistance to environmental interference, ensuring stable reception of the laser signal even under conditions of spot jitter and intensity fluctuations caused by turbulence. Its output guides the focused optical signal to a large-core multimode fiber 2 and a ring detector 3, respectively.

[0026] Furthermore, a large-core multimode fiber 2 is positioned at the center of the focusing path of the optomechanical system 1. Its input end receives the central portion of the laser signal focused by the optomechanical system 1, and its output end connects to the input end of the microlens 4. The large-core multimode fiber 2 has a core diameter of 105 μm and employs a low refractive index difference design for efficient transmission of the laser center optical signal. Its large core diameter allows it to receive the central portion of the focused spot, significantly reducing the requirements for beam alignment accuracy and avoiding spot drift and deformation caused by atmospheric turbulence, thereby improving optical signal coupling efficiency. The large-core multimode fiber 2 is positioned within the central hole of the zirconia ceramic ferrule 2a. An AlN-ZrO2 composite transition layer 2b is provided between the outer cylindrical surface of the ceramic ferrule and the ring detector 3. The thermal expansion coefficient of this transition layer is between that of zirconia and silicon, and a gradient matching interface is formed with the inner diameter of the ferrule and the detector ring through low-temperature co-firing or thick-film processes to alleviate thermal expansion mismatch and meet the thermal cycling reliability requirements of the device within a temperature range of -40℃ to +85℃.

[0027] Furthermore, the ring detector 3 is a Si-based PIN-ring detector, surrounding the large-core multimode fiber 2 and coaxially positioned with it. Its input end receives the laser edge light signal that, after being focused by the optomechanical 1, does not enter the large-core multimode fiber 2, and its output end is connected to the input end of the optical power detection module 8. The ring detector 3 can adopt a circular or square ring structure, possessing high responsivity and a uniform photosensitive surface, ensuring accurate detection of edge light power changes that have diffused beyond the center due to turbulence. The ring detector 3 only receives the edge light signal and converts it into a corresponding analog electrical signal, which is then transmitted to the optical power detection module 8, thereby converting the edge light energy lost in traditional schemes into an effective control signal.

[0028] Furthermore, a microlens 4 is positioned between the output end of the large-core multimode fiber 2 and the large photosensitive surface APD 5 to focus the diverging beam output from the fiber onto the photosensitive surface of the APD, thereby improving coupling efficiency and reducing alignment tolerance. Through precise optical design, the microlens 4 efficiently focuses the central optical signal output from the large-core multimode fiber 2 onto the photosensitive surface of the large photosensitive surface APD 5, ensuring concentrated optical energy transmission.

[0029] Furthermore, the output of the large photosensitive surface APD5 is connected to the input of the first transimpedance amplifier 6. The large photosensitive surface APD5 has a photosensitive diameter of 50 μm, used to receive the center light signal focused by the microlens 4 and complete high-speed photoelectric conversion. The APD operates in avalanche mode, providing internal gain to convert weak light signals into current signals. Its high sensitivity and large photosensitive surface characteristics are suitable for receiving fluctuating light signals under turbulent conditions.

[0030] Furthermore, the output of the first transimpedance amplifier 6 is connected to the input of the second transimpedance amplifier 7. The first transimpedance amplifier 6 is used to convert the weak current signal output from the large photosensitive surface APD5 into a primary voltage signal and provides low-noise, high-gain front-end amplification. This amplifier adopts a low equivalent input current noise and low feedback resistance design, balancing wide bandwidth and low noise, with a gain of over 60dB, ensuring signal integrity.

[0031] Furthermore, the output of the second transimpedance amplifier 7 is connected to the first input of the dynamic decision level module 9. The second transimpedance amplifier 7 is used to further amplify and compensate the bandwidth of the primary voltage signal output by the first transimpedance amplifier 6, so as to improve the signal amplitude and optimize the signal-to-noise ratio. This amplifier has adjustable gain and equalization circuitry to compensate for front-end bandwidth limitations, and the output signal amplitude meets the requirements of subsequent processing.

[0032] Furthermore, the output of the optical power detection module 8 is connected to the second input of the dynamic decision level module 9. The optical power detection module 8 is used to integrate, filter, and quantize the analog electrical signal output by the ring detector 3 to obtain the laser edge optical power information in real time. This module includes an integrator, a low-pass filter, and an analog-to-digital converter (ADC) to convert the edge optical signal into a stable power indication voltage, accurately reflecting the light intensity fluctuations caused by atmospheric turbulence.

[0033] Furthermore, the output of the dynamic decision level module 9 is connected to the input of the limiting amplifier module 10. The dynamic decision level module 9 adaptively adjusts the decision threshold level based on the power indication voltage provided by the optical power detection module 8, and performs threshold decision on the data signal from the second transimpedance amplifier 7. This module employs a high-speed comparator to calculate the optimal decision point in real time based on the edge optical power. It automatically lowers the decision threshold to maintain sensitivity during deep signal fading and raises the threshold to avoid saturation distortion when the signal is too strong, thereby effectively suppressing bit errors caused by turbulence and outputting a regenerated digital signal.

[0034] Furthermore, the output of the limiting amplification module 10 is connected to the input of the standard amplitude signal output module 11. The limiting amplification module 10 is used to limit and differentially amplify the digital signal output by the dynamic decision level module 9, eliminating residual amplitude fluctuations and providing a constant output swing. This module has a limiting buffer and a differential driver, ensuring stable output signal amplitude and compatibility with standard logic levels.

[0035] Furthermore, the standard amplitude signal output module 11 is used to convert the limited and amplified signal into an output signal with stable amplitude that conforms to the standard interface level. This module uses a level converter and an output buffer, and the output signal conforms to standard interface specifications such as LVDS or PECL, which can be directly connected to subsequent digital processing equipment.

[0036] The entire device operates as follows: After the incident laser is focused by the optomechanical unit 1, its central optical signal is transmitted through a large-core multimode fiber 2 and focused by a microlens 4 onto a large photosensitive surface APD5 for photoelectric conversion. The edge optical signal is captured by a ring detector 3 and sent to the optical power detection module 8. The current signal output from the large photosensitive surface APD5 is amplified stepwise by a first transimpedance amplifier 6 and a second transimpedance amplifier 7, and then sent to the first input terminal of the dynamic decision level module 9. Simultaneously, the power indication voltage generated by the optical power detection module 8 is sent to the second input terminal of the dynamic decision level module 9. The dynamic decision level module 9 adaptively adjusts the decision threshold according to the edge optical power, regenerates the amplified data signal, and then passes it through a limiting amplification module 10 to eliminate amplitude fluctuations. Finally, the standard amplitude signal output module 11 outputs the standard interface signal. By separating the central and edge optical signals and dynamically adjusting the decision level, this device effectively overcomes the light intensity fluctuations and spot jitter caused by atmospheric turbulence, improving the reliability and error performance of laser reception.

[0037] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0038] It should be noted that the components mentioned in the above embodiments are all general standard parts or components known to those skilled in the art. Their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.

[0039] This invention has illustrated its principles and implementation methods using specific examples. The descriptions of these embodiments are merely illustrative of the method and its core ideas; furthermore, those skilled in the art will recognize that modifications may be made to the specific implementation methods and application scope based on the principles of this invention. Therefore, the content of this specification should not be construed as limiting the invention.

Claims

1. A laser receiving device adaptable to atmospheric turbulence, characterized in that, It includes an optomechanical system (1), a large-core multimode fiber (2), a ring detector (3), a microlens (4), a large photosensitive surface APD (5), a first transimpedance amplifier (6), a second transimpedance amplifier (7), an optical power detection module (8), a dynamic decision level module (9), a limiting amplification module (10), and a standard amplitude signal output module (11). The optomechanical system (1) is used to receive and initially focus the incident laser beam; The large-core multimode fiber (2) is located at the center of the focusing path of the optical engine (1), its input end receives the laser center light signal after being focused by the optical engine (1), and its output end is connected to the input end of the microlens (4). The ring detector (3) is a Si-based PIN-ring detector, which is arranged coaxially around the outer periphery of the large-core multimode fiber (2). Its input end receives the laser edge light signal that has not entered the large-core multimode fiber (2) after being focused by the optomechanical (1), and its output end is connected to the input end of the optical power detection module (8). The microlens (4) is disposed between the output end of the large core diameter multimode fiber (2) and the large photosensitive surface APD (5) to focus the light emitted from the fiber onto the photosensitive surface of the large photosensitive surface APD (5). The output terminal of the large photosensitive surface APD (5) is connected to the input terminal of the first transimpedance amplifier (6); The output terminal of the first transimpedance amplifier (6) is connected to the input terminal of the second transimpedance amplifier (7); The output of the second transimpedance amplifier (7) is connected to the first input of the dynamic decision level module (9); The output terminal of the optical power detection module (8) is connected to the second input terminal of the dynamic decision level module (9); The output terminal of the dynamic decision level module (9) is connected to the input terminal of the limiting amplifier module (10); The output terminal of the limiting amplification module (10) is connected to the input terminal of the standard amplitude signal output module (11); The standard amplitude signal output module (11) is used to output a signal with stable amplitude that conforms to the standard interface level.

2. The laser receiving device adaptable to atmospheric turbulence according to claim 1, characterized in that, The large-core multimode optical fiber (2) is positioned inside the central hole of the zirconia ceramic ferrule (2a); an AlN-ZrO2 composite transition layer (2b) is provided between the outer cylindrical surface of the zirconia ceramic ferrule (2a) and the ring detector (3). The thermal expansion coefficient of the AlN-ZrO2 composite transition layer (2b) is between that of zirconia and silicon, and a gradient matching interface is formed with the inner diameter of the ferrule and the detector ring through low-temperature co-firing or thick film process.

3. The laser receiving device adaptable to atmospheric turbulence according to claim 1, characterized in that, The ring detector (3) is a circular or square ring structure and is coaxially arranged with the large core diameter multimode fiber (2); it is used to receive only the laser edge light signal that has not entered the large core diameter multimode fiber (2) after being focused by the optomechanical (1), and convert the edge light signal into a corresponding analog electrical signal and transmit it to the optical power detection module (8).

4. The laser receiving device adaptable to atmospheric turbulence according to claim 1, characterized in that, The microlens (4) focuses the central optical signal output from the large-core multimode fiber (2) onto the photosensitive surface of the large photosensitive surface APD (5); the photosensitive diameter of the large photosensitive surface APD (5) is 50 μm, which is used to complete high-speed photoelectric conversion.

5. The laser receiving device adaptable to atmospheric turbulence according to claim 1, characterized in that, The first transimpedance amplifier (6) is used to convert the weak current signal output by the large photosensitive surface APD (5) into a primary voltage signal and provide low noise and high gain front-end amplification.

6. The laser receiving device adaptable to atmospheric turbulence according to claim 1, characterized in that, The second transimpedance amplifier (7) is used to further amplify and compensate the bandwidth of the primary voltage signal output by the first transimpedance amplifier (6) in order to improve the signal amplitude and optimize the signal-to-noise ratio.

7. The laser receiving device adaptable to atmospheric turbulence according to claim 1, characterized in that, The optical power detection module (8) is used to integrate, filter and quantize the analog electrical signal output by the ring detector (3), obtain laser edge optical power information in real time, and send the power indication voltage to the dynamic decision level module (9).

8. The laser receiving device adaptable to atmospheric turbulence according to claim 1, characterized in that, The dynamic decision level module (9) is used to adaptively adjust the decision threshold level according to the power indication voltage provided by the optical power detection module (8), and to make a threshold decision on the data signal from the second transimpedance amplifier (7).

9. The laser receiving device adaptable to atmospheric turbulence according to claim 1, characterized in that, The limiting amplification module (10) is used to limit and differentially amplify the digital signal output by the dynamic decision level module (9), eliminate residual amplitude fluctuations, and provide a constant output swing.

10. The laser receiving device adaptable to atmospheric turbulence according to claim 1, characterized in that, The standard amplitude signal output module (11) uses a level converter and an output buffer, and the output signal conforms to the LVDS or PECL standard interface specification.

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