A solar-blind ultraviolet communication system and method based on thermo-optical and photonic quantum properties

Abstract

This invention relates to a solar-blind ultraviolet communication system and method based on thermo-optical quantum properties. The transmitting end utilizes LED and LD light sources, and a light source pulse driver shapes the emitted ultraviolet pulses with consistent average intensity to conceal first-order intensity characteristics. The light source is selected based on the bit stream. The receiving end acquires two original timestamp streams and a merged stream through an HBT module and a time-correlated single-photon counting module. A correlator constructs a g²(τ) curve using the original streams. Synchronization recovery and frame header detection utilize the merged stream to recover the clock and switching mode. In the first mode, a width decision unit extracts the full width at half maximum (FWHM) output to adapt to the first data stream for high-throughput services, while in the second mode, a height decision unit extracts the g²(0) output to adapt to the second data stream for high-security services. This technical solution upgrades the modulation dimension from first-order intensity to second-order correlation, achieving highly concealed, anti-interception, and dual-mode reliable communication under extremely low light conditions.

Description

Technical Field

[0001] This invention belongs to the field of solar-blind ultraviolet communication technology, specifically relating to a solar-blind ultraviolet communication system and method based on thermo-optical quantum properties. Background Technology

[0002] Solar-blind ultraviolet communication systems utilize the "invisible" nature of ultraviolet light in the 200nm-280nm band to achieve secure and interference-resistant communication. Because this band has extremely low solar background noise and can achieve non-linear transmission through atmospheric scattering, it exhibits excellent environmental adaptability in complex terrains or between buildings. Traditional solar-blind ultraviolet communication systems mainly consist of an optical transceiver front-end (ultraviolet LED array, photomultiplier tube, etc.) and a digital control system centered on an FPGA.

[0003] However, traditional solar-blind ultraviolet communication systems mainly employ intensity modulation / direct detection (IM / DD) methods, such as on / off keying (OOK) or pulse position modulation (PPM). As applications expand to deep space exploration, covert communication, and anti-jamming networks, existing technologies have revealed the following inherent limitations: 1. Limited information carrier and channel capacity: Traditional systems only use the first-order statistics of the light field (i.e., light intensity) to carry information. The information is only encoded in the light intensity dimension, and the channel capacity is limited by the intensity modulation upper limit of Shannon's formula.

[0004] 2. Heavily reliant on light intensity for decision-making, failing under extremely weak light: The receiver recovers information by comparing photon counts with a threshold. In long-distance or strongly attenuated channels, the photon count decreases sharply, and the probability of decision error increases exponentially, making reliable communication difficult to achieve.

[0005] 3. Modulation rate and sensitivity are mutually restrictive: Traditional PPM increases the rate by compressing the pulse width, but this leads to a decrease in the signal-to-noise ratio. A trade-off must be made between data rate, transmission distance and power consumption.

[0006] 4. Insufficient concealment: The difference between "light / no light" or "strong light / weak light" in OOK or PPM is easily detected by the interceptor through simple photon counting, resulting in a high risk of exposing the communication behavior.

[0007] 5. Weak ability to counter intelligent interference: The physical layer waveform lacks unique characteristics and is easily imitated or predicted. The enemy can launch false signals to deceive or block it. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a solar-blind ultraviolet communication system and method based on thermo-optical quantum properties.

[0009] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A solar-blind ultraviolet communication system based on thermo-optical quantum properties, comprising a transmitter and a receiver; The transmitter includes: A time-slot clock generator is used to generate equally spaced time-slot clocks. A statistical time-slot mapper is used to generate a light source selection signal for each time slot based on the input bit stream and the time-slot clock. A light source pulse driver is used to generate drive current and shape electrical pulses; Parallel I / O multiplexer is used to distribute drive current to LED or LD light source according to light source selection signal, so that LED and LD light sources emit ultraviolet light pulses with consistent average light intensity. The receiving end includes: Optical antennas are used to collect light scattered from the atmosphere; Solar-blind ultraviolet filters are used to filter out ambient light outside of the solar-blind wavelength range. The HBT module is used to split and detect the filtered signal. The time-correlated single-photon counting module is used to record the arrival time of photons, output a first original timestamp stream, a second original timestamp stream, and a merged timestamp stream generated by logically merging the two original timestamp streams; The synchronization and clock recovery module is used to receive the merged timestamp stream and to recover the time slot clock from the received signal; The frame header detection module is used to receive the merged timestamp stream and determine the data stream type based on the frame header identifier to switch the working mode. The correlator is used to receive the first and second original timestamp streams, perform cross-correlation operations, and construct the g²(τ) curve. The time slot division and bit recovery module is used to obtain the recovered time slot clock; A width decision unit is used to extract the half-width of the g²(τ) curve in the first mode for decision-making, and output the first data stream in combination with the recovered time slot clock. The height decision unit is used to extract the g²(0) value at zero delay of the g²(τ) curve in the second mode for decision-making, and output the second data stream in combination with the recovered time slot clock.

[0010] Furthermore, the first data stream output by the width decision device and the second data stream output by the height decision device are then demodulated by the demodulation module and decoded by the LDPC decoding module to finally restore the original information.

[0011] Furthermore, the HBT module includes a 50:50 beam splitter and two single-photon detectors; the 50:50 beam splitter is used to split the signal after being filtered by the solar-blind ultraviolet filter into two beams of equal intensity, and the two beams are respectively input to the two single-photon detectors for detection.

[0012] Furthermore, the light source pulse driver shapes the electrical pulse by adjusting the width and intensity of the electrical pulse so that the thermal light pulse generated by the LED light source and the coherent light pulse generated by the LD light source are consistent in the time domain and average light intensity, thereby hiding the first-order intensity modulation trace.

[0013] Furthermore, in the first mode, the width decision device compares the half-width to a first preset threshold, and the narrow half-width is determined to be the bit corresponding to the LED light source, and the wide half-width is determined to be the bit corresponding to the LD light source; in the second mode, the height decision device compares the g²(0) value to a second preset threshold, and the g²(0) value is greater than the second preset threshold and is determined to be the bit corresponding to the LED light source, and the g²(0) value is less than the second preset threshold and is determined to be the bit corresponding to the LD light source.

[0014] Furthermore, the first preset threshold is 1 ps, and the second preset threshold is 1.4 ps.

[0015] Furthermore, the first data stream is adapted to transmit high-throughput service data, and the second data stream is adapted to transmit high-security service data; the high-throughput service data is video data and voice data, and the high-security service data is key data, coordinate data, and distance data.

[0016] Furthermore, the transmitter also includes an LDPC encoding module, which is used to perform LDPC encoding on the input raw information and output the encoded bit stream to the statistical time slot mapper.

[0017] Furthermore, the time slot clock generator, statistical time slot mapper, LDPC encoding module, synchronization and clock recovery module, frame header detection module, correlator, time slot segmentation and bit recovery module, width decision unit, height decision unit, demodulation module, and LDPC decoding module are integrated within the same FPGA.

[0018] A solar-blind ultraviolet communication method based on thermo-optical quantum properties, implemented using the above system, includes the following steps: S1: The time slot clock generator at the transmitting end generates the time slot clock, and the statistical time slot mapper generates a light source selection signal for each time slot based on the input bit stream and the time slot clock; S2: The light source pulse driver generates a shaping drive current, and the parallel I / O multiplexer distributes the drive current to the LED light source or LD light source according to the light source selection signal, emitting solar blind ultraviolet light pulses with the same average light intensity but different photon statistical characteristics. S3: The optical antenna at the receiving end collects atmospheric scattered light, which is filtered by a solar-blind ultraviolet filter, then split and detected by the HBT module, and finally outputs the first original timestamp stream, the second original timestamp stream, and the merged timestamp stream by the time-correlated single-photon counting module. S4: The synchronization and clock recovery module recovers the time slot clock based on the merged timestamp stream and outputs it to the time slot segmentation and bit recovery module. The frame header detection module determines the data stream type and switches the working mode based on the frame header identifier in the merged timestamp stream. S5: The correlator performs cross-correlation operation based on the first and second original timestamp streams to construct the g²(τ) curve; if the current mode is the first mode, the width decision unit extracts the half-width of the g²(τ) curve for decision, and the time slot segmentation and bit recovery module outputs the first data stream in combination with the time slot clock; if the current mode is the second mode, the height decision unit extracts the g²(0) value at zero delay of the g²(τ) curve for decision, and the time slot segmentation and bit recovery module outputs the second data stream in combination with the time slot clock; S6: The first or second data stream is demodulated by the demodulation module, then decoded by the LDPC decoding module, and finally the original information is restored.

[0019] The beneficial effects that this invention can achieve are as follows: 1. Breaking through the traditional IM / DD framework to achieve multi-dimensional multiplexing: Converting traditional intensity or phase modulation into photonic statistical characteristic modulation (second-order correlation characteristics of the optical field), extending communication from the "intensity domain" to the "statistical domain". It not only utilizes time slot location, but also photon arrival modes (spotted or uniform) to carry information, thereby improving channel capacity with the same time-frequency resources.

[0020] 2. Supports extremely weak optical communication: Statistical decision-making replaces intensity-based decision-making. Statistical characteristics remain relatively constant during light intensity attenuation and are independent of the absolute photon count. Even under ultra-low light intensity conditions where the average photon count per bit is <1, reliable decision-making can still be achieved through accumulated statistics, significantly improving the maximum transmission distance.

[0021] 3. Significantly improves time slot utilization and communication rate: Traditional 4-PPM requires 4 time slots to transmit only 2 bits, while this solution uses all 4 time slots to emit light, with each time slot independently carrying 1 bit, and can transmit 4 bits. The communication rate is directly increased to twice that of 4-PPM, breaking the PPM rate bottleneck.

[0022] 4. Achieving "stealthy" communication at the physical layer: The transmitter ensures that the average light intensity of the LED and LD is the same, so that the total light intensity remains constant regardless of whether "0" or "1" is sent. The information is hidden in the statistical correlation of photon arrival time, making it impossible for the enemy to detect the communication behavior through simple power detection, thus achieving extremely high stealth.

[0023] 5. Strong anti-interference capability: The physical layer waveform carries the unique quantum statistical characteristics of the light source (fluctuations in coherence time / photon number), which are difficult for the enemy to imitate or predict, effectively resisting deception and jamming interference. Attached Figure Description

[0024] Figure 1 This is a structural block diagram of the transmitter in an embodiment of the present invention.

[0025] Figure 2 This is a structural block diagram of the receiving end in an embodiment of the present invention. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Example

[0027] A solar-blind ultraviolet communication system based on thermo-optical quantum properties includes a transmitter and a receiver.

[0028] The transmitter includes an LDPC encoding module, a time-slot clock generator, a statistical time-slot mapper, a light source pulse driver, a parallel I / O multiplexer, an LED light source, and an LD light source. The LED light source is a UV LED chip integrating multiple mini-LEDs, and the LD light source is a UV LD laser array chip integrating multiple LD chips.

[0029] At the transmitting end, the LDPC encoding module performs LDPC encoding on the input raw information and outputs the encoded bitstream to the statistical time-slot mapper. The time-slot clock generator produces strictly equal-interval time-slot clocks. Driven by the time-slot clocks, the statistical time-slot mapper maps the LDPC-encoded bitstream to a light source selection signal in each time slot. When the input bit is "1", the output signal selects the LED; when the input bit is "0", the output signal selects the LD. To ensure concealment, the electrical pulses generated by the light source pulse driver are rigorously shaped. By adjusting the pulse width and intensity, the thermal light pulses generated by the LED light source and the coherent light pulses generated by the LD light source are completely consistent in time-domain envelope and average light intensity, thus concealing first-order intensity modulation traces. The parallel I / O multiplexer precisely conducts the drive current to the corresponding LED or LD branch in each time slot according to the light source selection signal.

[0030] While the light emitted by LED and LD light sources is indistinguishable in terms of macroscopic intensity, they differ fundamentally in their quantum statistical properties: LEDs have extremely short photon coherence time and a beam-gathering effect (g²(0)→2), while LDs have longer coherence time and no beam-gathering effect (g²(0)=1).

[0031] The receiver includes an optical antenna, a solar-blind ultraviolet filter, an HBT module, a time-correlated single-photon counting module, a synchronization and clock recovery module, a frame header detection module, a correlator, a time slot division and bit recovery module, a width decision unit, a height decision unit, a demodulation module, and an LDPC decoding module.

[0032] At the receiver, an optical antenna collects non-line-of-sight ultraviolet signals scattered by the atmosphere, while a solar-blind ultraviolet filter removes strong background light outside the solar-blind band. The signal light enters the HBT module, which includes a 50:50 beam splitter and two single-photon detectors (SPD1 and SPD2). The 50:50 beam splitter splits the filtered signal into two beams of equal intensity, which are then input to the two single-photon detectors for detection. The Time-Correlated Single-Photon Counting (TCSPC) module records the photon arrival time, generating a first raw timestamp stream (from SPD1) and a second raw timestamp stream (from SPD2). Simultaneously, the two raw timestamp streams are logically ORed and merged to generate a merged timestamp stream.

[0033] These three timestamp streams are fed into the processing core (in this embodiment, a single FPGA is used) for processing: The synchronization and clock recovery module receives the merged timestamp stream and recovers the time slot clock from the received signal; The frame header detection module receives the merged timestamp stream, identifies the frame header identifier, and distinguishes whether the currently transmitted data is high-throughput service data or high-security service data, thereby switching the working mode accordingly. The merged timestamp stream contains all detected photon events, increasing the event occurrence rate and thus improving the probability of synchronization header capture and the accuracy of time slot clock recovery.

[0034] The correlator receives the first and second raw timestamp streams. The correlator only performs cross-correlation on the timestamps of the two independently detected streams to construct a second-order correlation function g²(τ) curve that reflects the statistical characteristics of photons, thus avoiding interference from autocorrelation terms caused by the merged streams.

[0035] In the first mode, the width decision unit measures the half-width at half maximum (FWHM) of the g²(τ) curve. Because the coherence time of thermo-optical signals is extremely short, the FWHM is extremely narrow (e.g., <1 ps), while the FWHM of coherent optical signals is wider. This is compared with the 1 ps threshold to determine the bit width; a narrow FWHM results in a "1" bit, and a wide FWHM results in a "0" bit. Since the FWHM difference spans orders of magnitude, the required integration time is short, supporting high symbol rates. The time slot division and bit recovery module, combined with the recovered time slot clock, outputs a first data stream adapted for high-throughput services such as video and voice.

[0036] In the second mode, the height decision unit extracts the g²(0) value at zero delay. For thermal light, g²(0) is close to 2, and for coherent light, g²(0) is close to 1. Based on this, a bit is determined by comparing it with a 1.4 threshold; if g²(0) > 1.4, the bit is determined to be "1", and if g²(0) < 1.4, the bit is determined to be "0". Because the difference in g²(0) is small, a longer integration time is needed to overcome shot noise. Although this limits the rate, it possesses inherent resistance to strong eavesdropping and robustness against extremely weak light. The time-slot segmentation and bit recovery module outputs a second data stream adapted to high-security services such as keys, coordinates, and distance.

[0037] Finally, the output data stream is demodulated by the demodulation module and then sent to the LDPC decoding module to correct channel transmission errors and restore the original information from the transmitter. Example

[0038] A solar-blind ultraviolet communication method based on thermo-optical quantum properties, implemented according to the system of Example 1, includes the following steps: S1: The time slot clock generator at the transmitting end generates the time slot clock, and the statistical time slot mapper generates a light source selection signal for each time slot based on the input bit stream and the time slot clock.

[0039] S2: The light source pulse driver generates a shaping drive current. The parallel I / O multiplexer distributes the drive current to the LED light source or LD light source according to the light source selection signal, emitting solar blind ultraviolet light pulses with the same average light intensity but different photon statistical characteristics.

[0040] S3: The optical antenna at the receiving end collects atmospheric scattered light, which is filtered by a solar-blind ultraviolet filter, then split and detected by the HBT module, and finally outputs the first original timestamp stream, the second original timestamp stream, and the merged timestamp stream by the time-correlated single-photon counting module.

[0041] S4: The synchronization and clock recovery module recovers the time slot clock based on the merged timestamp stream and outputs it to the time slot segmentation and bit recovery module. The frame header detection module determines the data stream type based on the frame header identifier in the merged timestamp stream and switches the working mode.

[0042] S5: The correlator performs cross-correlation operation based on the first and second original timestamp streams to construct the g²(τ) curve; if the current mode is the first mode, the width decision unit extracts the half-width of the g²(τ) curve for decision, and the time slot division and bit recovery module outputs the first data stream in combination with the time slot clock; if the current mode is the second mode, the height decision unit extracts the g²(0) value at zero delay of the g²(τ) curve for decision, and the time slot division and bit recovery module outputs the second data stream in combination with the time slot clock.

[0043] S6: The first or second data stream is demodulated by the demodulation module, then decoded by the LDPC decoding module, and finally the original information is restored.

[0044] The g²(τ) curve is a concept in quantum optics, statistical optics, and single-molecule spectroscopy. Its full name is the normalized second-order intensity correlation function curve, primarily used to describe the statistical properties of a light field, especially the temporal distribution of photons and the coherence of the light field. τ is the time delay between two detection moments.

[0045] The above description is only one embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A solar-blind ultraviolet communication system based on thermo-optical quantum properties, comprising a transmitter and a receiver, characterized in that: The transmitter includes: A time-slot clock generator is used to generate equally spaced time-slot clocks. A statistical time-slot mapper is used to generate a light source selection signal for each time slot based on the input bit stream and the time-slot clock. A light source pulse driver is used to generate drive current and shape electrical pulses; Parallel I / O multiplexer is used to distribute drive current to LED or LD light source according to light source selection signal, so that LED and LD light sources emit ultraviolet light pulses with consistent average light intensity. The receiving end includes: Optical antennas are used to collect light scattered from the atmosphere; Solar-blind ultraviolet filters are used to filter out ambient light outside of the solar-blind wavelength range. The HBT module is used to split and detect the filtered signal. The time-correlated single-photon counting module is used to record the arrival time of photons, output a first original timestamp stream, a second original timestamp stream, and a merged timestamp stream generated by logically merging the two original timestamp streams; The synchronization and clock recovery module is used to receive the merged timestamp stream and to recover the time slot clock from the received signal; The frame header detection module is used to receive the merged timestamp stream and determine the data stream type based on the frame header identifier to switch the working mode. The correlator is used to receive the first and second original timestamp streams, perform cross-correlation operations, and construct the g²(τ) curve. The time slot division and bit recovery module is used to obtain the recovered time slot clock; A width decision unit is used to extract the half-width of the g²(τ) curve in the first mode for decision-making, and output the first data stream in combination with the recovered time slot clock. The height decision unit is used to extract the g²(0) value at zero delay of the g²(τ) curve in the second mode for decision-making, and output the second data stream in combination with the recovered time slot clock.

2. The solar-blind ultraviolet communication system based on thermo-optical quantum properties according to claim 1, characterized in that, The first data stream output by the width decision device and the second data stream output by the height decision device are then demodulated by the demodulation module and decoded by the LDPC decoding module to finally restore the original information.

3. The solar-blind ultraviolet communication system based on thermo-optical quantum properties according to claim 1, characterized in that, The HBT module includes a 50:50 beam splitter and two single-photon detectors; the 50:50 beam splitter is used to split the signal after it has been filtered by the solar-blind ultraviolet filter into two beams of equal intensity, and the two beams are respectively input to the two single-photon detectors for detection.

4. The solar-blind ultraviolet communication system based on thermo-optical quantum properties according to claim 1, characterized in that, The light source pulse driver shapes the electrical pulse by adjusting the width and intensity of the electrical pulse so that the thermal light pulse generated by the LED light source and the coherent light pulse generated by the LD light source are consistent in the time domain and average light intensity, thereby hiding the first-order intensity modulation trace.

5. The solar-blind ultraviolet communication system based on thermo-optical quantum properties according to claim 1, characterized in that, In the first mode, the width decision device compares the half-width to a first preset threshold, and the narrow half-width is determined to be the bit corresponding to the LED light source, and the wide half-width is determined to be the bit corresponding to the LD light source; in the second mode, the height decision device compares the g²(0) value to a second preset threshold, and the g²(0) value is greater than the second preset threshold and is determined to be the bit corresponding to the LED light source, and the g²(0) value is less than the second preset threshold and is determined to be the bit corresponding to the LD light source.

6. The solar-blind ultraviolet communication system based on thermo-optical quantum properties according to claim 5, characterized in that, The first preset threshold is 1 ps, and the second preset threshold is 1.4 ps.

7. The solar-blind ultraviolet communication system based on thermo-optical quantum properties according to claim 1, characterized in that, The first data stream is adapted to transmit high-throughput service data, and the second data stream is adapted to transmit high-security service data; the high-throughput service data is video data and voice data, and the high-security service data is key data, coordinate data, and distance data.

8. The solar-blind ultraviolet communication system based on thermo-optical quantum properties according to claim 2, characterized in that, The transmitter also includes an LDPC encoding module, which performs LDPC encoding on the input raw information and outputs the encoded bit stream to the statistical time slot mapper.

9. The solar-blind ultraviolet communication system based on thermo-optical quantum properties according to claim 8, characterized in that, The time slot clock generator, statistical time slot mapper, LDPC encoding module, synchronization and clock recovery module, frame header detection module, correlator, time slot segmentation and bit recovery module, width decision unit, height decision unit, demodulation module, and LDPC decoding module are integrated within the same FPGA.

10. A solar-blind ultraviolet communication method based on thermo-optical quantum properties, implemented according to the system described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1: The time slot clock generator at the transmitting end generates the time slot clock, and the statistical time slot mapper generates a light source selection signal for each time slot based on the input bit stream and the time slot clock; S2: The light source pulse driver generates a shaping drive current, and the parallel I / O multiplexer distributes the drive current to the LED light source or LD light source according to the light source selection signal, emitting solar blind ultraviolet light pulses with the same average light intensity but different photon statistical characteristics. S3: The optical antenna at the receiving end collects atmospheric scattered light, which is filtered by a solar-blind ultraviolet filter, then split and detected by the HBT module, and finally outputs the first original timestamp stream, the second original timestamp stream, and the merged timestamp stream by the time-correlated single-photon counting module. S4: The synchronization and clock recovery module recovers the time slot clock based on the merged timestamp stream and outputs it to the time slot segmentation and bit recovery module. The frame header detection module determines the data stream type and switches the working mode based on the frame header identifier in the merged timestamp stream. S5: The correlator performs cross-correlation operation based on the first and second original timestamp streams to construct the g²(τ) curve; if the current mode is the first mode, the width decision unit extracts the half-width of the g²(τ) curve for decision, and the time slot segmentation and bit recovery module outputs the first data stream in combination with the time slot clock; if the current mode is the second mode, the height decision unit extracts the g²(0) value at zero delay of the g²(τ) curve for decision, and the time slot segmentation and bit recovery module outputs the second data stream in combination with the time slot clock; S6: The first or second data stream is demodulated by the demodulation module, then decoded by the LDPC decoding module, and finally the original information is restored.

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