A novel space optical communication on-off keying optical signal transmitting device and modulation method

Abstract

This invention provides a novel space optical communication pulse-modulated optical signal transmitting device and modulation method, which combines the characteristics of PAM modulation and pulse modulation. It maintains the timing accuracy of pulse communication systems while enabling each pulse to carry more bits of information. Compared with traditional OOK or PPM systems, it can significantly improve the information transmission capacity per unit bandwidth and the optical link spectrum utilization efficiency. Through the multi-level mechanism of PAM modulation and the cooperation of a high sampling rate photodetector, the system has stronger fault tolerance to non-ideal channel conditions such as jitter and path disturbance, making it suitable for communication scenarios with frequent dynamic changes, such as inter-satellite communication and UAV networking. At the same time, the signal control board has a multi-level adjustable mechanism of 16, 32, and 128 levels, allowing users to flexibly configure the system transmission rate and error resistance according to actual needs such as communication distance, link quality, and power budget, thereby improving the system's adaptability and overall performance.

Description

Technical Field

[0001] This invention relates to the field of space optical communication technology, and in particular to a novel space optical communication pulse-modulated optical signal transmitting device and modulation method. Background Technology

[0002] Space optical communication, as an important direction for next-generation high-speed, high-capacity communication technology, has shown great potential in fields such as deep space exploration, low-Earth orbit satellite constellations, and unmanned aerial vehicle (UAV) communication. With the increasing demands for high-capacity, long-distance, and low-power communication in these applications, space optical communication has attracted widespread attention due to its advantages such as high bandwidth, low latency, strong anti-interference capabilities, small size, and low power consumption. Compared to traditional wireless radio frequency (RF) communication systems, space optical communication can provide data transmission rates of hundreds of Gbps or even higher, and has better anti-eavesdropping capabilities and spectrum utilization efficiency, making it one of the core technologies in aerospace, satellite networks, and high-speed air-to-ground communication. Existing space optical communication systems typically employ basic modulation methods such as amplitude modulation (e.g., OOK), phase modulation (e.g., BPSK, QPSK), or pulse position modulation (PPM). While these technologies exhibit good performance in certain scenarios, they have significant limitations in terms of bandwidth utilization, system robustness, anti-interference capabilities, and hardware implementation complexity.

[0003] Existing problems include: while PPM modulation has high detection efficiency in low signal-to-noise ratio environments, its symbol rate is limited by pulse positioning accuracy, resulting in low spectral efficiency and difficulty in meeting the requirements of high-speed data transmission; although phase modulation has high bandwidth utilization, it is extremely sensitive to phase noise, and the phase demodulation circuit is complex, easily introducing high system bit error rate and link maintenance costs in long-distance space links. In recent years, multilevel pulse amplitude modulation (PAM) has been widely used in high-speed interconnects in data centers due to its advantages such as simple signal structure, direct demodulation method, and ease of implementation by FPGA or ASIC. In particular, PAM4 has become a key modulation technology in the 400G Ethernet standard. Introducing PAM into space optical communication systems can theoretically increase the number of information bits transmitted per unit time, improve spectral efficiency, and reduce the coherence requirements of lasers and the complexity of the receiver. However, the direct application of PAM modulation in space optical communication still faces many challenges, such as signal attenuation caused by long-distance transmission, demodulation failure caused by inter-satellite beam drift, and high precision requirements for system clock synchronization. If pulse modulation technology cannot be effectively combined with pulse synchronization to improve timing accuracy, and PAM modulation cannot be used to enhance the information carrying capacity of each pulse, it will be difficult to achieve a synergistic improvement in communication efficiency and system stability.

[0004] Therefore, there is an urgent need in this field for a novel space optical communication transmitting device and method that can integrate PAM modulation and pulse modulation to solve the technical problems of low bandwidth utilization, high bit error rate, large hardware complexity and weak anti-interference ability in the existing technology, and to achieve a balance between high-speed transmission, high spectral efficiency and system robustness. Summary of the Invention

[0005] The purpose of this invention is to provide a novel space optical communication pulse-modulated optical signal transmitting device and modulation method 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 novel space optical communication pulse-modulated optical signal transmitting device, comprising: an optical frequency comb laser, a coupler, a photodetector, a signal control board, a phase modulator, an erbium-doped fiber amplifier, and an optical telescope; The output end of the optical frequency comb laser is connected to the input end of the coupler; The first output terminal of the coupler is connected to the input terminal of the photodetector, and the second output terminal is connected to the first input terminal of the phase modulator. The output terminal of the photodetector is connected to the input terminal of the signal control board; The output terminal of the signal control board is connected to the second input terminal of the phase modulator; The output of the phase modulator is connected to the input of the erbium-doped fiber amplifier; The output of the erbium-doped fiber amplifier is connected to the input of the optical telescope; The optical telescope is used to collimate and emit light signals.

[0007] Preferably, the optical frequency comb laser is used to generate a highly stable, ultrashort, and equally spaced optical pulse sequence, the spectrum of which consists of a series of equally spaced, phase-coherent discrete frequency components.

[0008] Preferably, the signal control board includes a high-speed photoelectric signal receiving interface, a clock extraction and recovery circuit, a digital signal processor, a digital-to-analog converter, a PAM modulation driver, and a power management module; the signal control board is used to receive electrical pulse signals from the photodetector, extract clock signals, and generate multi-level PAM drive voltage signals according to the digital data to be transmitted.

[0009] Preferably, the PAM modulation driver is a multi-level modulation driver that supports at least one modulation scheme among PAM16, PAM32, and PAM128.

[0010] Preferably, the PAM modulation driver maps digital data to multi-level voltage symbols, wherein each 4 bits of data in PAM16 is mapped to a 16-level voltage symbol, each 5 bits of data in PAM32 is mapped to a 32-level voltage symbol, and each 7 bits of data in PAM128 is mapped to a 128-level voltage symbol.

[0011] Preferably, the phase modulator linearly changes the phase of the optical pulse from the second output of the coupler according to the magnitude of the PAM driving voltage signal from the signal control board, thereby realizing multi-level shift of the optical pulse position in the time domain.

[0012] Preferably, the erbium-doped fiber amplifier is used to amplify the optical pulse signal modulated by the phase modulator, compensate for optical losses in the phase modulator and the link, and increase the signal optical power to the level required for long-distance free space transmission.

[0013] Preferably, the optical telescope is used to collimate the divergent beam output by the erbium-doped fiber amplifier into a highly parallel beam, so as to realize long-distance space optical communication.

[0014] The present invention also provides a modulation method, comprising the following steps: S1. The optical frequency comb laser generates a highly stable, ultra-short, and equally spaced optical pulse sequence; S2. The coupler splits the optical pulse sequence into two paths, one of which is sent to the phase modulator and the other to the photodetector; S3. The photodetector converts optical pulse signals into electrical pulse signals; S4. The signal control board extracts the clock signal from the electrical pulse signal and generates a multi-level PAM drive voltage signal based on the digital data; S5. The phase modulator modulates the phase of the optical pulse according to the PAM driving voltage signal to achieve pulse position modulation; S6. The erbium-doped fiber amplifier amplifies the modulated optical signal; S7. The optical telescope collimates and emits light signals.

[0015] Preferably, the number of levels of the multi-level PAM driving voltage signal is configurable, and the user can select PAM16, PAM32 or PAM128 modulation mode according to the communication distance, link quality or power budget requirements.

[0016] The present invention achieves the following beneficial technical effects compared to the prior art: This invention provides a novel space optical communication pulse-modulated optical signal transmitting device and modulation method, which combines the characteristics of PAM modulation and pulse modulation. It maintains the timing accuracy of pulse communication systems while enabling each pulse to carry more bits of information. Compared with traditional OOK or PPM systems, it can significantly improve the information transmission capacity per unit bandwidth and the optical link spectrum utilization efficiency. Through the multi-level mechanism of PAM modulation and the cooperation of a high sampling rate photodetector, the system has stronger fault tolerance to non-ideal channel conditions such as jitter and path disturbance, making it suitable for communication scenarios with frequent dynamic changes, such as inter-satellite communication and UAV networking. At the same time, the signal control board has a multi-level adjustable mechanism of 16, 32, and 128 levels, allowing users to flexibly configure the system transmission rate and error resistance according to actual needs such as communication distance, link quality, and power budget, thereby improving the system's adaptability and overall performance. 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 novel space optical communication pulse-modulated optical signal transmitting device provided by the present invention; In the diagram: 1: Optical frequency comb laser, 2: Coupler, 3: Photodetector, 4: Signal control board, 5: Phase modulator, 6: Erbium-doped fiber amplifier, 7: Optical telescope. 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 novel space optical communication pulse-modulated optical signal transmitting device and modulation method 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: like Figure 1 As shown, the novel space optical communication pulse-modulated optical signal transmitting device provided by the present invention mainly includes an optical frequency comb laser 1, a coupler 2, a photodetector 3, a signal control board 4, a phase modulator 5, an erbium-doped fiber amplifier 6, and an optical telescope 7. These components are connected in series via optical fibers or other optical connectors to form a complete optical signal transmission link.

[0025] In this configuration, the output of the optical frequency comb laser 1 is connected to the input of coupler 2; the first output of coupler 2 is connected to the input of photodetector 3, and the second output is connected to the first input of phase modulator 5; the output of photodetector 3 is connected to the input of signal control board 4, and the output of signal control board 4 is connected to the second input of phase modulator 5; the output of phase modulator 5 is connected to the input of erbium-doped fiber amplifier 6, and the output of erbium-doped fiber amplifier 6 is connected to the input of optical telescope 7. Optical telescope 7 is used to collimate the optical signal and transmit it to a free-space channel.

[0026] Specifically, the optical frequency comb laser 1, as the system's light source, generates a highly stable, ultrashort, and equally spaced sequence of optical pulses. Its spectrum consists of a series of equally spaced, phase-coherent discrete frequency components. This optical pulse sequence manifests in the time domain as short pulses with a fixed repetition frequency, providing the system with a precise time reference. The coupler 2, acting as a beam splitter, divides the optical pulse stream from the optical frequency comb laser 1 into two paths: one serves as the main optical path, sent to the phase modulator 5 for signal modulation, and the other serves as the reference optical path, sent to the photodetector 3 for clock extraction. The splitting ratio of the coupler 2 can be adjusted according to system requirements to ensure that the main optical path has sufficient optical power for modulation, while the reference optical path provides sufficient optical power for the clock recovery circuit.

[0027] Furthermore, photodetector 3 receives the reference optical path signal from coupler 2, converts it into a corresponding electrical pulse signal, and sends it to signal control board 4. Signal control board 4 is the core processing unit of the system, integrating a high-speed photoelectric signal receiving interface, clock extraction and recovery circuit, digital signal processor, digital-to-analog converter, PAM modulation driver, and power management module. Signal control board 4 first extracts a precise clock signal from the electrical pulse signal using a clock extraction and recovery circuit (such as a phase-locked loop or clock data recovery circuit), serving as the time reference for the entire system. Subsequently, the digital signal processor calculates the required time offset for each pulse based on the digital data to be transmitted, combined with the extracted clock signal, and generates a multi-level PAM drive voltage signal through the digital-to-analog converter and PAM modulation driver. The PAM modulation driver supports configurable multi-level modulation methods; this embodiment uses PAM16, mapping each 4 bits of data to a 16-level voltage symbol. Users can flexibly select the modulation mode to balance transmission rate and error tolerance based on actual needs such as communication distance, link quality, or power budget.

[0028] Furthermore, the phase modulator 5 receives the main optical pulse from the coupler 2 and the multi-level PAM drive voltage signal from the signal control board 4, and linearly changes the phase of the optical pulse according to the magnitude of the voltage signal. In the time domain, the linear change in phase directly corresponds to the translation of the optical pulse on the time axis; that is, different drive voltage levels lead to different phase shifts, thereby producing different time offsets, encoding digital information into the pulse position, and realizing pulse-position modulation. The erbium-doped fiber amplifier 6 optically amplifies the modulated optical pulse signal, compensates for optical losses in the phase modulator 5 and the transmission link, and increases the signal optical power to a level that meets the requirements for long-distance free-space transmission. Finally, the optical telescope 7 collimates the amplified divergent beam into a highly parallel beam to reduce beam divergence loss and ensure stable transmission of the optical signal in the space channel.

[0029] In the specific implementation process, taking PAM16 modulation as an example, the signal control board 4 maps every 4 bits of input data to a voltage symbol of one of 16 levels, and the phase modulator 5 shifts the position of each optical pulse to one of 16 possible time slots, thereby realizing that each pulse carries 4 bits of information.

[0030] This invention also provides a modulation method based on the above-mentioned device, comprising the following steps: an optical frequency comb laser 1 generates a highly stable, ultrashort, and equally spaced optical pulse sequence; a coupler 2 splits the optical pulse sequence into two paths, one path being sent to a phase modulator 5 and the other path being sent to a photodetector 3; the photodetector 3 converts the optical pulse signal into an electrical pulse signal; a signal control board 4 extracts a clock signal from the electrical pulse signal and generates a multi-level PAM driving voltage signal based on the input digital data; the phase modulator 5 modulates the phase of the optical pulse according to the PAM driving voltage signal to achieve pulse-position modulation; an erbium-doped fiber amplifier 6 amplifies the modulated optical signal; and an optical telescope 7 collimates and emits the optical signal. This method, by integrating PAM modulation and pulse modulation, significantly improves spectral efficiency and system robustness while maintaining the timing accuracy of pulse communication.

[0031] Example 2: This embodiment uses PAM32 modulation, where each 5 bits of data is mapped to a 32-level voltage symbol, and each pulse carries 5 bits of information. The remaining steps and principles are the same as those described in Embodiment 1.

[0032] Example 3: This embodiment uses PAM128 modulation, where each 7 bits of data is mapped to a 128-level voltage symbol, and each pulse carries 7 bits of information. The remaining steps and principles are the same as those described in Embodiment 1.

[0033] The aforementioned multi-level pulse modulation mechanism significantly improves the information carrying capacity of a single pulse. At the same time, the stable pulse sequence provided by the optical frequency comb laser 1 and the precise clock extracted by the signal control board 4 ensure the system's timing accuracy and anti-interference capability.

[0034] 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.

[0035] 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.

[0036] 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 novel space optical communication pulse-modulated optical signal transmitting device, characterized in that, include: Optical frequency comb lasers, couplers, photodetectors, signal control boards, phase modulators, erbium-doped fiber amplifiers, and optical telescopes; The output end of the optical frequency comb laser is connected to the input end of the coupler; The first output terminal of the coupler is connected to the input terminal of the photodetector, and the second output terminal is connected to the first input terminal of the phase modulator. The output terminal of the photodetector is connected to the input terminal of the signal control board; The output terminal of the signal control board is connected to the second input terminal of the phase modulator; The output of the phase modulator is connected to the input of the erbium-doped fiber amplifier; The output of the erbium-doped fiber amplifier is connected to the input of the optical telescope; The optical telescope is used to collimate and emit light signals.

2. The novel space optical communication pulse-modulated optical signal transmitting device according to claim 1, characterized in that, The optical frequency comb laser is used to generate highly stable, ultrashort, and equally spaced optical pulse sequences, the spectrum of which consists of a series of equally spaced, phase-coherent discrete frequency components.

3. The novel space optical communication pulse-modulated optical signal transmitting device according to claim 1, characterized in that, The signal control board includes a high-speed photoelectric signal receiving interface, a clock extraction and recovery circuit, a digital signal processor, a digital-to-analog converter, a PAM modulation driver, and a power management module. The signal control board is used to receive electrical pulse signals from the photodetector, extract clock signals, and generate multi-level PAM drive voltage signals according to the digital data to be transmitted.

4. The novel space optical communication pulse-modulated optical signal transmitting device according to claim 3, characterized in that, The PAM modulation driver is a multi-level modulation driver that supports at least one modulation scheme among PAM16, PAM32 and PAM128.

5. The novel space optical communication pulse-modulated optical signal transmitting device according to claim 4, characterized in that, The PAM modulation driver maps digital data to multi-level voltage symbols, wherein each 4 bits of data in PAM16 is mapped to a 16-level voltage symbol, each 5 bits of data in PAM32 is mapped to a 32-level voltage symbol, and each 7 bits of data in PAM128 is mapped to a 128-level voltage symbol.

6. The novel space optical communication pulse-modulated optical signal transmitting device according to claim 1, characterized in that, The phase modulator linearly changes the phase of the optical pulse from the second output of the coupler according to the magnitude of the PAM driving voltage signal from the signal control board, thereby realizing multi-level shift of the optical pulse position in the time domain.

7. The novel space optical communication pulse-modulated optical signal transmitting device according to claim 1, characterized in that, The erbium-doped fiber amplifier is used to amplify the optical pulse signal modulated by the phase modulator, compensate for optical losses in the phase modulator and the link, and increase the signal optical power to the level required for long-distance free space transmission.

8. The novel space optical communication pulse-modulated optical signal transmitting device according to claim 1, characterized in that, The optical telescope is used to collimate the divergent beam output from the erbium-doped fiber amplifier into a highly parallel beam, thereby enabling long-distance space optical communication.

9. A modulation method, characterized in that, The novel space optical communication pulse-modulated optical signal transmitting device according to any one of claims 1 to 8 includes the following steps: S1. The optical frequency comb laser generates a highly stable, ultra-short, and equally spaced optical pulse sequence; S2. The coupler splits the optical pulse sequence into two paths, one of which is sent to the phase modulator and the other to the photodetector; S3. The photodetector converts optical pulse signals into electrical pulse signals; S4. The signal control board extracts the clock signal from the electrical pulse signal and generates a multi-level PAM drive voltage signal based on the digital data; S5. The phase modulator modulates the phase of the optical pulse according to the PAM driving voltage signal to achieve pulse position modulation; S6. The erbium-doped fiber amplifier amplifies the modulated optical signal; S7. The optical telescope collimates and emits light signals.

10. The modulation method according to claim 9, characterized in that, The number of levels of the multi-level PAM drive voltage signal is configurable, and users can select PAM16, PAM32 or PAM128 modulation modes according to communication distance, link quality or power budget requirements.

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