A space laser communication system based on pulsed light modulation and demodulation

Abstract

This invention discloses a space laser communication system based on pulsed light modulation and demodulation, comprising: a transmitter and a receiver; the transmitter includes a pulsed light source, a driving modulation circuit unit, and a transmitting optical path; the pulsed light source carries pulsed signal light; the driving modulation circuit unit directly modulates the pulsed signal light; the transmitting optical path transmits the modulated pulsed signal light into space; the receiver includes a receiving optical path, an optical signal detection unit, and a signal demodulation unit; the receiving optical path receives the modulated pulsed signal light; the optical signal detection unit performs signal conversion and amplification on the modulated pulsed signal light; and the signal demodulation unit performs signal demodulation and data recovery on the modulated pulsed signal light. This invention utilizes a direct modulation pulsed light source, saving modulation bandwidth and reducing the complexity of signal modulation and demodulation at both the transmitter and receiver, making it suitable for constructing low-power and low-cost space laser communication systems.

Description

Technical Field

[0001] This invention belongs to the field of space laser communication technology, and particularly relates to a space laser communication system based on pulsed light modulation and demodulation. Background Technology

[0002] When using continuous light sources as the signal source for space laser communication, a higher transmitted signal power is generally required to increase the transmission distance of the laser communication system. This is typically achieved by amplifying the signal light using an optical amplifier before transmission. However, the electro-optical energy conversion efficiency of optical amplifiers is generally low, thus significantly increasing the average power consumption of the laser communication transmitter. Meanwhile, pulsed light sources can achieve much higher peak power compared to continuous light sources, resulting in higher energy utilization efficiency. Therefore, pulsed laser sources are often used as the signal source in communication scenarios with high transmission channel loss or long transmission distances, such as deep space communication and underwater communication. Furthermore, the modulation and demodulation methods for pulsed light differ significantly from those for continuous light. Commonly used modulation methods for pulsed light include Pulse Position Modulation (PPM) or other similar derivatives, which utilize the time slot position or relative position of the light pulse in the transmission sequence to characterize the signal encoding. However, while PPM modulation improves energy utilization, it sacrifices modulation bandwidth. Therefore, improved modulation methods have emerged to minimize the waste of modulation bandwidth. Meanwhile, the principle of PPM modulation and demodulation is more complex than that of direct intensity modulation or keying modulation (OOK) of continuous light, so the modulation and demodulation of pulsed light signals is also more difficult and complex to implement.

[0003] Therefore, there is an urgent need to propose a space laser communication system based on pulsed light modulation and demodulation. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a space laser communication system based on pulsed light modulation and demodulation, thereby resolving the issues present in the prior art.

[0005] To achieve the above objectives, the present invention provides a space laser communication system based on pulsed light modulation and demodulation, comprising: a transmitter and a receiver;

[0006] The transmitting end includes a high-power narrow pulse light source, a driving modulation circuit unit, and a transmitting optical path;

[0007] The high-power narrow-pulse light source is used to carry pulse signal light; the driving modulation circuit unit is used to drive the high-power narrow-pulse light source to emit light and directly modulate the pulse signal light; the emission optical path is used to spatially emit the modulated pulse signal light according to the beam quality requirements.

[0008] The driving modulation circuit unit is used to use a binary on / off keying OOK modulation signal as an external trigger signal for a high-power narrow pulse light source, directly triggering and controlling the high-power narrow pulse light source to emit light, thereby realizing the carrying of the OOK signal through the narrow pulse signal light.

[0009] The receiving end includes a receiving optical path, an optical signal detection unit, and a signal demodulation unit;

[0010] The receiving optical path is used to couple and receive the modulated pulse signal light emitted from the transmitting end; the optical signal detection unit is used to perform photoelectric signal conversion and signal amplification processing on the received pulse signal light to obtain a pulse electrical signal; the response bandwidth of the optical signal detection unit is allowed to be less than the bandwidth required corresponding to the rise or fall time of the pulse signal light; the signal demodulation unit is used to perform signal demodulation and data recovery on the pulse electrical signal.

[0011] The signal demodulation unit includes a signal shaping unit, which is used to trigger and delay the detected narrow pulse electrical signal to obtain a continuous OOK signal.

[0012] Optionally, the high-power narrow-pulse light source has an external signal triggering function to ensure the loading of the pulse signal light.

[0013] Optionally, the transmitter of the space laser communication system also includes an external data interface circuit, which provides a communication data source for communication between the external signal source device of the transmitter and the transmitter of the laser communication system.

[0014] Optionally, the optical signal detection unit includes a photodetector and an amplifier circuit;

[0015] The photodetector is used to detect the received modulated pulse signal light and convert the modulated pulse signal light into a pulse electrical signal; the amplifier circuit is used to linearly amplify the pulse electrical signal.

[0016] Optionally, the signal shaping unit can implement the pulse signal trigger delay function by using an FPGA or a microcontroller with a simple surrounding circuit, or by directly constructing a trigger delay circuit through a trigger timer or other trigger timing circuit; wherein, the control of the pulse signal delay time is consistent with the symbol period length of the OOK modulation signal at the transmitting end.

[0017] Optionally, the signal demodulation unit further includes a data recovery unit, which is used to perform data recovery on the shaped continuous OOK signal using a clock data recovery chip, or to perform oversampling and data recovery on the signal using a sampling chip or FPGA device.

[0018] Optionally, the receiving end of the space laser communication system further includes an external data interface circuit, which is used to transmit the recovered communication data to an external terminal device.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects:

[0020] The present invention provides a space laser communication system based on pulsed light modulation and demodulation. By taking advantage of the higher energy utilization rate of high-power narrow pulse light sources compared to continuous light sources, the average optical power requirement of the transmitter can be reduced, the signal light amplification unit can be eliminated, and the overall power consumption and size of the laser communication system can be reduced, which is conducive to the low-cost and miniaturized design of the laser communication system.

[0021] This invention utilizes a high-power narrow-pulse light source that is externally triggered by the OOK signal to carry the OOK signal. Compared with traditional pulse position modulation (PPM), this method saves modulation bandwidth and reduces the complexity of signal modulation and demodulation at the transmitting and receiving ends.

[0022] When demodulating signals at the receiving end, this invention uses a trigger delay method to first shape the pulse signal into a quasi-continuous or continuous OOK signal before data recovery, which reduces the difficulty of direct demodulation of the pulse signal and also relaxes the bandwidth requirements of the photodetector. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0024] Figure 1 This is a schematic diagram of the structural composition of a space laser communication system based on pulsed light modulation and demodulation according to an embodiment of the present invention. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0027] Example 1

[0028] like Figure 1As shown, this embodiment provides a space laser communication system based on pulsed light modulation and demodulation, including a laser communication transmitter and a receiver. The transmitter mainly includes a high-power narrow-pulse light source, a driving modulation circuit unit, a transmitting optical path, and an external data interface circuit; the receiver mainly includes a receiving optical path, an optical signal detection unit, a signal demodulation unit, and an external data interface circuit.

[0029] A high-power narrow-pulse light source at the transmitting end serves as a signal modulation source to carry communication signals. This high-power narrow-pulse light source, acting as a signal modulation source, can be either a coherent or incoherent pulse source. Specifically, the type of high-power narrow-pulse light source can be selected based on the communication scenario and the design requirements of the communication terminal. For example, the communication scenario may require parameters such as wavelength, power, pulse width, and pulse repetition frequency of the pulse source, while the communication terminal may have specific design requirements regarding power consumption and size. It can be a semiconductor laser, a fiber laser, or other types of pulse source. Simultaneously, the high-power narrow-pulse light source needs to have an external signal triggering function to ensure the loading of the modulation signal.

[0030] The driving modulation circuit unit can drive a high-power narrow-pulse light source to emit light and load a communication modulation signal, avoiding the complex pulse position modulation method used in traditional pulse light sources. Specifically, the driving modulation circuit unit uses a binary on / off keying (OOK) modulation signal as an external trigger signal for the high-power narrow-pulse light source, directly triggering and controlling the light emission of the high-power narrow-pulse light source, thus achieving the carrying of the OOK signal through narrow-pulse signal light. This signal loading method is similar to non-return-to-zero keying modulation (NRZ-OOK) for continuous light sources, and is easy to implement with a very simple structure. This modulation method is much simpler than the traditional pulse position modulation (PPM) method for pulse light sources, as it does not require signal encoding and synchronization control, and also saves modulation bandwidth compared to PPM modulation. In addition, the modulation symbol rate should be less than the highest pulse repetition frequency of the pulse light source.

[0031] The transmitting optical path is used to transmit the modulated pulsed signal light into space according to certain beam quality requirements. Specifically, the transmitting optical path can be designed according to different communication scenarios, front-end light source structures, and communication terminal performance requirements.

[0032] The aforementioned external data interface circuit for the transmitter is used to provide a communication data source for communication between the external signal source device of the transmitter and the transmitter of the laser communication system.

[0033] The receiving optical path at the receiving end is used to couple the spatial signal light emitted by the transmitting end into the signal light detection unit. Specifically, the receiving optical path, like the transmitting optical path, can be designed according to different communication scenarios, back-end detection unit structures, and communication terminal performance requirements.

[0034] The optical signal detection unit includes a photodetector and an amplifier circuit. The photodetector detects the received pulsed light signal and converts it into an electrical signal. The amplifier circuit linearly amplifies the weak electrical signal after detection. The response bandwidth of the photodetector can be greater than or less than the bandwidth required for the rise / fall time of the pulsed light signal, without requiring additional software algorithms or hardware overhead to compensate for the resulting signal distortion. Because the subsequent demodulation unit shapes the pulse signal before data recovery, it does not depend on the pulse shape, and the proportion of the symbol time slot occupied by the pulse width is very small; the width of the entire symbol is much larger than the pulse width. Therefore, distortion-free detection of the pulsed light signal is not required, thus reducing the detection bandwidth requirement of the photodetector.

[0035] The signal demodulation unit is used to demodulate and recover the detected pulse signal, including a signal shaping unit and a data recovery unit. The signal shaping unit converts the detected narrow pulse discrete signal into a continuous or quasi-continuous OOK signal, while the data recovery unit samples, decides on, and recovers the data from the shaped OOK signal. Specifically, the signal shaping unit mainly implements the trigger delay function for the pulse signal, widening and shaping the pulse signal to achieve waveform conversion. The shaping unit mainly implements the trigger delay function for the pulse signal, widening the narrow pulse discrete signal into a continuous signal with a high duty cycle. The specific trigger delay function can be implemented using an FPGA or microcontroller with surrounding simple circuitry, or it can be implemented by directly constructing a trigger delay circuit using a trigger timer or other trigger timing circuits to achieve pulse signal shaping. The trigger delay time of the shaping unit for the pulse signal should be approximately equal to the symbol width of the communication rate. This delay time is much larger than the pulse width of the optical pulse, so the influence of the photodetector's response to the optical pulse can be basically ignored. This is why the detection bandwidth requirement of the photodetector can be reduced. This is more advantageous for pulse light sources with very small pulse widths. A small pulse width means higher energy utilization efficiency, enabling longer-distance communication with lower power consumption, which is more in line with our design goals. In addition, since this scheme uses a narrow pulse light source, the pulse width of the optical pulse signal is generally very small, and the duty cycle within the signal time slot is very small. Therefore, it is relatively difficult to directly determine whether the pulse signal is present at the receiving end, and the bandwidth requirements of the device are also very high. However, the shaped signal is converted into a continuous or quasi-continuous OOK signal, which makes the subsequent data recovery unit's demodulation and data recovery of the signal very simple.

[0036] The data recovery unit is used for sampling, decision-making, and data recovery of the shaped signal. Specifically, since the shaped signal has become a continuous OOK signal, a conventional clock data recovery (CDR) chip can be used directly for data recovery. Alternatively, sampling, decision-making, and data recovery can be performed by oversampling the signal using a sampling chip or FPGA. Because the shaped continuous OOK signal is directly demodulated using a conventional CDR chip, the demodulation complexity is much lower than that of traditional pulse-modulated PPM signals. It is also easier to implement than directly demodulating unshaped pulse keying signals, and the requirements for the detection and demodulation optoelectronic devices are much lower.

[0037] The receiver's external data interface circuit is used to transmit the demodulated data to external terminal equipment after it has been recovered.

[0038] This embodiment employs a high-power narrow-pulse light source as the signal source to improve the energy utilization efficiency of the light source. Simultaneously, a novel modulation and demodulation scheme reduces the complexity of pulsed light signal modulation and demodulation, which is beneficial for the miniaturization, low power consumption, and low-cost design of the space laser communication system. Compared to the scheme of modulating continuous seed light sources and then amplifying the signal light, the space laser communication system designed according to this approach can significantly reduce the power consumption and size of the laser communication system; compared to continuous signal light modulation schemes with the same average emitted light power, it can transmit over a longer communication distance; and compared to traditional pulsed light modulation and demodulation schemes, it can reduce the difficulty and complexity of modulation and demodulation at the transmitting and receiving ends of the laser communication system, and reduce the bandwidth requirements of the devices.

[0039] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A space laser communication system based on pulsed light modulation and demodulation, characterized in that, include: Transmitter and receiver; The transmitting end includes a high-power narrow pulse light source, a driving modulation circuit unit, and a transmitting optical path; The high-power narrow-pulse light source is used to carry pulse signal light; the driving modulation circuit unit is used to drive the high-power narrow-pulse light source to emit light and directly modulate the pulse signal light; the emission optical path is used to spatially emit the modulated pulse signal light according to the beam quality requirements. The driving modulation circuit unit is used to use a binary on / off keying OOK modulation signal as an external trigger signal for a high-power narrow pulse light source, directly triggering and controlling the high-power narrow pulse light source to emit light, thereby realizing the carrying of the OOK signal through the narrow pulse signal light. The receiving end includes a receiving optical path, an optical signal detection unit, and a signal demodulation unit; The receiving optical path is used to couple and receive the modulated pulse signal light emitted from the transmitting end; the optical signal detection unit is used to perform photoelectric signal conversion and signal amplification processing on the received pulse signal light to obtain a pulse electrical signal; the response bandwidth of the optical signal detection unit is allowed to be less than the bandwidth required corresponding to the rise or fall time of the pulse signal light; the signal demodulation unit is used to perform signal demodulation and data recovery on the pulse electrical signal. The signal demodulation unit includes a signal shaping unit, which is used to trigger and delay the detected narrow pulse electrical signal to obtain a continuous OOK signal; The signal shaping unit implements the pulse signal trigger delay function in either an FPGA or a microcontroller with a simple surrounding circuit, or by directly constructing a trigger delay circuit through a trigger timer or other trigger timing circuit; wherein, the control of the pulse signal delay time is consistent with the symbol period length of the OOK modulation signal at the transmitting end; The signal demodulation unit further includes a data recovery unit, which is used to perform data recovery on the shaped continuous OOK signal using a clock data recovery chip, and to perform oversampling and data recovery on the signal using a sampling chip or FPGA device. The high-power narrow-pulse light source has an external signal triggering function to ensure the loading of communication signals; The transmitter of the space laser communication system also includes an external data interface circuit, which is used to provide a communication data source for communication between the external signal source device of the transmitter and the transmitter of the laser communication system. The optical signal detection unit includes a photodetector and an amplifier circuit; The photodetector is used to detect the received modulated pulse signal light and convert the modulated pulse signal light into a pulse electrical signal; the amplifier circuit is used to linearly amplify the pulse electrical signal. The receiving end of the space laser communication system also includes an external data interface circuit, which is used to transmit the recovered communication data to an external terminal device.

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