Extremely weak light time domain information extraction method and device based on single photon detection

Abstract

The invention discloses an extremely weak light time domain information extraction method and device based on single photon detection, and belongs to the technical field of optical communication and quantum time frequency transmission. In order to solve the problems that link attenuation is high and far-end extremely weak light is difficult to detect in non-relay amplification long-distance time transfer, a single-photon detection technology is mainly adopted to be combined with a scanning chromatography technology, clock signals are synchronized through a time base module, a light source module, a modulation module, an amplification module, an optical fiber transmission module and a single-photon detection module are matched, and the time base module and the single-photon detection module are combined. Reconstruction of extremely weak light waveforms and extraction of key time domain information are realized. According to the invention, time-frequency information can be effectively transmitted in long-distance optical communication without relay amplification, and the detection difficulty of extremely weak light is overcome.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical communication and quantum time-frequency transfer, and in particular relates to a method and device for extracting extremely weak light time-domain information based on single-photon detection. Background Art

[0002] High-precision long-distance time and frequency transmission plays an indispensable role in satellite navigation, geodesy, time synchronization and other fields. As an infrastructure with long transmission distance and large coverage, optical fiber is very suitable as a medium for long-distance time and frequency transmission. In existing technical solutions, long-distance time and frequency transmission can be achieved through optical relay of "receiving optical signal-optical power replenishment-optical signal retransmission" or electrical relay of "photoelectric conversion-electrical amplification-electrical-optical conversion". However, in some special and important application scenarios, it is usually difficult to establish an effective relay node environment. For example, in extremely harsh environmental areas, such as remote suburban areas with extremely weak infrastructure, the laying of relay nodes faces challenges; in scenarios where long-distance signal regeneration technology is scarce, such as deserts, plateaus, polar regions, and the seabed, optical cable laying can only support point-to-point transmission; in emergency applications, such as natural disasters, emergency communications and other sudden scenarios, the flexibility of relay laying is greatly reduced. These scenarios have put forward an urgent need for high-precision relay-free transmission technology for time and frequency signals.

[0003] In long-distance signal transmission without relay amplification, the high loss of the optical fiber link becomes the most important limiting factor compared with the effects of dispersion and nonlinear effects. In view of the high loss in long-distance signal transmission, there are usually two typical solutions to increase the transmission distance without relay in classical optical communication: one is to add an amplifier after the transmitter and before the receiver; the other is to use a new detection method, such as a single-photon detector, to use the avalanche effect to amplify weak photocurrent to achieve weak signal recovery. However, in high-precision time-frequency transmission, both of the above solutions have theoretical and experimental difficulties. At the transmitter, the above scheme requires the use of an ultra-high linewidth light source to increase the stimulated Brillouin scattering threshold, thereby increasing the optical power input to the fiber, which has considerable limitations in experiments. At the receiver, on the one hand, the limited gain-bandwidth product requires a balance and trade-off between high gain and sufficiently large detection bandwidth, that is, the receiver obtains a signal with sufficient energy and maintains the rising edge, phase and other information of the signal without serious distortion; on the other hand, the single-photon detector used in the above scheme only judges the high and low levels of the signal, and loses the detailed time domain information of the pulse. In high-precision time and frequency transmission, it is necessary to detect the waveform of the transmitted signal to obtain key information such as phase jitter and rising edge position for stability evaluation and time synchronization. Therefore, the relay-free solution in classical optical communication is still quite far from the demand for high-precision time and frequency transmission. Summary of the invention

[0004] The purpose of the present invention is to provide a method and device for extracting extremely weak light time domain information based on single photon detection, so as to solve the problems of high link attenuation and difficulty in detecting extremely weak light at the far end in long-distance time transmission without relay amplification.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is as follows.

[0006] An extremely weak light time domain information extraction device based on single photon detection comprises a light source module, a first modulation module, a first signal source module, a second modulation module, a second signal source module, an amplifier module, an optical fiber link module, a single photon detection module, a third signal source module, a data processing module and a time base module; wherein, The time base module is used to achieve clock synchronization between the first signal source module and the third signal source module through electrical signals; The first signal source module is used to generate a modulation signal of the first modulation module; The third signal source module is used to generate an external gating signal for the single photon detection module; The second signal source module is used to generate a modulation signal of the second modulation module; The light source module is used to generate a first optical signal and transmit it to the first modulation module; The first modulation module modulates the first optical signal using the modulation signal provided by the first signal source module, and outputs the second optical signal to the second modulation module; The second modulation module performs phase modulation on the second optical signal using the modulation signal provided by the second signal source module, and outputs a third optical signal to the amplifier module; The amplifier module is used to amplify the third optical signal and output a fourth optical signal; The optical fiber link module is used to transmit the fourth optical signal and output the fifth optical signal to the single photon detection module; The single photon detection module is used to perform scanning chromatography on the fifth optical signal according to the external gating signal provided by the third signal source module, and output an electrical signal to the data processing module; The data processing module is used to process electrical signals, reconstruct waveforms, and extract key time domain information.

[0007] Furthermore, the light source module is a single-frequency continuous light laser.

[0008] Furthermore, the first signal source module generates a time signal to be transmitted.

[0009] Furthermore, the first modulation module is an intensity modulator.

[0010] Furthermore, the modulation signal generated by the second signal source module is Gaussian white noise.

[0011] Furthermore, the second modulation module is a phase modulator, which widens the line width of the second optical signal to increase the Brillouin scattering threshold of the optical fiber.

[0012] Furthermore, the amplifier module is an optical amplifier.

[0013] Furthermore, the single-photon detection module is a single-photon detector whose photon number cannot be distinguished, and the output electrical signal is the photon counting rate.

[0014] Furthermore, the single-photon detection module achieves fine scanning of the rising edge of the fifth optical signal by adjusting the gate signal delay.

[0015] Furthermore, the data processing module records the count rates under different relative time delays and completes fitting to achieve waveform recovery of the fifth optical signal and extraction of key time domain information.

[0016] A method for extracting extremely weak light time domain information based on single photon detection, the steps of which include: The time base module generates an electrical signal C and connects to the first signal source module, generates an electrical signal D and connects to the third signal source module to achieve clock synchronization; The first signal source module generates an electrical signal A and connects it to the first modulation module as a modulation signal; The light source module generates a first optical signal and connects to the first modulation module; After the first optical signal is intensity modulated in the first modulation module, clock information is loaded and a second optical signal is output to the second modulation module; The second signal source module generates an electrical signal and connects to the second modulation module as a modulation signal; After the second optical signal is phase modulated by the second modulation module, the laser line width increases and a third optical signal is output; The third optical signal enters the amplifier module and outputs a fourth optical signal after being amplified; The fourth optical signal is connected to the optical fiber link module, and outputs a fifth optical signal after passing through the optical fiber link; The third signal source module generates an electrical signal E and is connected to the single photon detection module as an external gating signal to control the gating signal; The fifth optical signal is connected to the single-photon detection module, and is scanned and tomographically processed by an external electrical signal E, and an electrical signal F is output after detection; The electrical signal F is connected to the data processing module to complete waveform reconstruction and key time domain information extraction.

[0017] The beneficial effects achieved by the present invention are as follows.

[0018] 1. The present invention is based on single-photon detection technology, which can realize the reconstruction of extremely weak light waveforms and extract key time domain information.

[0019] 2. The present invention can use an ordinary continuous laser light source and a full-loss optical fiber link without gain, avoiding high-cost laser gain equipment and simplifying the system structure.

[0020] 3. The present invention overcomes the difficulty of detecting extremely weak light through scanning tomography technology, and can effectively transmit time and frequency information in long-distance optical communications without relay amplification.

[0021] 4. The present invention can use a photon number indistinguishable detector to achieve high-precision time domain information extraction, and has higher detection sensitivity and accuracy.

[0022] 5. The present invention has broad application prospects and can be applied to the fields of optical communication, quantum time-frequency transfer, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a module composition diagram of the extremely weak light time domain information extraction device based on single photon detection of the present invention.

[0024] Figure 2 It is a schematic diagram of the scanning process in the extremely weak light waveform tomography recovery based on single photon detection of the present invention.

[0025] Figure 3 3 is a module composition diagram of an extremely weak light time domain information extraction device based on single photon detection according to an embodiment.

[0026] Figure 4 Schematic diagram of the scanning process in extremely weak light waveform tomography recovery based on single photon detection in an embodiment. DETAILED DESCRIPTION

[0027] In order to make the various technical features and advantages or technical effects in the above technical solutions of the present invention more obvious and easy to understand, they are described in detail below with reference to the accompanying drawings.

[0028] The present invention discloses an extremely weak light time domain information extraction device based on single photon detection, comprising a light source module 1, a first modulation module 2, a first signal source module 3, a second modulation module 4, a second signal source module 5, an amplifier module 6, an optical fiber link module 7, a single photon detection module 8, a third signal source module 9, a data processing module 10 and a time base module 11. The module composition and signal processing process of the device are as follows: Figure 1 The specific steps are as follows.

[0029] (1) The electrical signal C generated by the time base module 11 is connected to the first signal source module 3 for clock synchronization of the first signal source module 3; the electrical signal D generated by the time base module 11 is connected to the third signal source module 9 for clock synchronization of the third signal source module 9.

[0030] (2) The electrical signal A (i.e., the time signal to be transmitted) generated by the first signal source module 3 is connected to the first modulation module 2 and used as the modulation signal of the first modulation module 2.

[0031] (3) A single-frequency continuous light laser is selected to form a light source module 1 , and a first optical signal generated by the light source module 1 is connected to a first modulation module 2 .

[0032] (4) After the first optical signal is intensity modulated by the first modulation module 2 (eg, intensity modulator), the source end clock information is loaded and the second optical signal is output to the second modulation module 4.

[0033] (5) The electrical signal B (such as Gaussian white noise) generated by the second signal source module 5 is connected to the second modulation module 4 and used as the modulation signal of the second modulation module 4.

[0034] (6) After the second optical signal is connected to the second modulation module 4 (eg, phase modulator), it undergoes phase modulation, increases the stimulated Brillouin scattering threshold, and then outputs a third optical signal.

[0035] (7) The third optical signal is connected to the amplifier module 6 (such as an optical amplifier), and after amplification, a fourth optical signal is output.

[0036] (8) The fourth optical signal is connected to the optical fiber link module 7, and outputs the fifth optical signal after passing through the optical fiber link. The optical fiber link module 7 is an ordinary single-mode optical fiber, does not contain any form of amplification or gain, and is a full-loss link. The fifth optical signal output by it is an extremely weak optical signal at the energy level of a single photon, and its waveform cannot be observed through existing detection schemes.

[0037] (9) After the clock is synchronized, the electrical signal E generated by the third signal source module 9 is connected to the single photon detection module 8 as an external gating signal for external gate signal control.

[0038] (10) The fifth optical signal is connected to the single-photon detection module 8 (e.g., a single-photon detector whose photon count is indistinguishable), and scanning tomography is implemented through the electrical signal E, including a coarse scanning process and a fine scanning process, wherein the rising edge of the fifth optical signal is finely scanned by adjusting the gate signal delay, and the electrical signal F (e.g., a photon counting rate) is output.

[0039] (11) The electrical signal F is connected to the data processing module 10. The data processing module 10 records the count rates under different relative delays and completes the fitting, thereby realizing the fifth optical signal waveform recovery and key time domain information extraction.

[0040] In the above process, the frequency of the electrical signal E is the same as that of the electrical signal A, and the relative phase between the electrical signal E and the electrical signal A is adjustable. By adjusting the relative phase, the relative delay between the electrical signal E and the fifth optical signal is equivalently changed, thereby achieving a coarse scan of the fifth optical signal.

[0041] The scanning process of this device based on single-photon detection and extremely weak light waveform tomography recovery is as follows Figure 2 The specific instructions are as follows.

[0042] (1) Figure 2 Figure (a) shows the waveform of one cycle of the rough scanning process. The cycle of the electrical signal E is the same as that of the fifth optical signal, and the width is , by adjusting the phase of the electrical signal E, with a step size The relative time relationship between the electrical signal E and the fifth optical signal is changed to obtain the electrical signal F, which reflects the counting rate at different positions. The phase of the electrical signal E is adjusted so that the electrical signal F is located near the obvious increase, and the phase of the electrical signal E is fixed.

[0043] (2) Figure 2 Figure (b) shows the waveform of one cycle of the fine scanning process. The cycle of the electrical signal E is the same as that of the fifth optical signal, and the width is By adjusting the gate signal delay in the single photon detection module 8, the step length By changing the relative time relationship between the electrical signal E and the fifth optical signal, an electrical signal F is obtained, which reflects the counting rate at different positions of the rising edge.

[0044] A specific embodiment is given below.

[0045] In this embodiment, the module composition and signal processing process of the device of the present invention are as follows: Figure 3 As shown, the specific processing steps are as follows.

[0046] (1) The 10 MHz sine wave signal generated by the time base module 11 is connected to the first signal source module 3 and the third signal source module 9 as the electrical signal C and the electrical signal D respectively, for clock synchronization.

[0047] (2) The first signal source module 3 generates a period after clock synchronization , duty cycle The square wave clock information is connected to the first modulation module 2 as an electrical signal A.

[0048] (3) Line width generated by light source module 1 The continuous light laser is connected to the first modulation module 2 as the first optical signal.

[0049] (4) After the first optical signal is intensity modulated by the intensity modulator of the first modulation module 2, square wave clock information is loaded and the signal is connected to the second modulation module 4 as the second optical signal.

[0050] (5) The 250 MHz Gaussian white phase noise generated by the second signal source module 5 is connected to the second modulation module 4 as the electrical signal B.

[0051] (6) After the second optical signal is phase modulated by the phase modulator of the second modulation module 4, the laser line width increases and the Brillouin scattering threshold increases to , output the third optical signal and connect it to the amplifier module 6.

[0052] (7) After the third optical signal is amplified by the EDFA serving as the amplifier module 6 , the fourth optical signal is output and connected to the optical fiber link module 7 .

[0053] (8) After the fourth optical signal passes through the optical fiber link module 7 without any form of amplification, the fifth optical signal is output and connected to the single-photon detection module 8.

[0054] (9) The third signal source module 9 generates a period after clock synchronization , duty cycle The square wave is connected to the single-photon detection module 8 as an electrical signal E to be used as an external gating signal for single-photon detection.

[0055] (10) After the fifth optical signal passes through the single-photon detection module 8, the phase of the electrical signal E is adjusted. Coarse scanning, adjusting the gate signal delay inside the single photon detection module 8; fine scanning, to change the relative delay of the electrical signal E compared to the fifth optical signal , complete the scanning tomography of the fifth light signal, and output the count rate as the electrical signal F , access the data processing module 10.

[0056] (11) After the electrical signal F is connected to the data processing module 10, the data processing module 10 calculates the rising edge count rate Sigmoid function is used for fitting: in , , is the fitting parameter. Different relative delay The count rate under It is directly proportional to the intensity of extremely weak light at different positions. The waveform reconstruction and key time domain information extraction are completed through the above fitting and threshold setting.

[0057] The process of scanning the fifth optical signal by adjusting the electrical signal E is as follows: Figure 4 As shown (in order to highlight the description of key information, the figure is not drawn to scale), the specific description is as follows.

[0058] (1) Figure 2 Figure (a) shows the rough scanning process, and the waveform in one cycle is shown in the figure. The period of the electrical signal E is the same as that of the fifth optical signal, and the width is , by adjusting the phase of the electrical signal E within the range of 0 to 360°, in steps of Changing the relative delay between the electrical signal E and the fifth optical signal , and obtain the electrical signal F, which reflects the counting rate at different positions The phase of the electrical signal E is adjusted so that the electrical signal F is located near the point where the apparent increase occurs, and the phase of the electrical signal E is fixed.

[0059] (2) Figure 2 Figure (b) shows the fine scanning process, and the waveform in one cycle is shown in the figure. The period of the electrical signal E is the same as that of the fifth optical signal, and the width is By adjusting the gate signal delay in the single photon detection module 8, the step length Changing the relative delay between the electrical signal E and the fifth optical signal , and obtain the electrical signal F, which reflects the counting rate at different positions of the rising edge .

[0060] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions of the technical solutions of the present invention made by ordinary technicians in the field should all be included in the protection scope of the present invention. The protection scope of the present invention shall be based on what is defined in the claims.

Claims

1. A device for extracting extremely weak light time domain information based on single photon detection, characterized in that: It includes a light source module, a first modulation module, a first signal source module, a second modulation module, a second signal source module, an amplifier module, an optical fiber link module, a single photon detection module, a third signal source module, a data processing module and a time base module; wherein, The time base module is used to achieve clock synchronization between the first signal source module and the third signal source module through electrical signals; The first signal source module is used to generate a modulation signal of the first modulation module; The third signal source module is used to generate an external gating signal for the single photon detection module; The second signal source module is used to generate a modulation signal of the second modulation module; The light source module is used to generate a first optical signal and transmit it to the first modulation module; The first modulation module modulates the first optical signal using the modulation signal provided by the first signal source module, and outputs the second optical signal to the second modulation module; The second modulation module performs phase modulation on the second optical signal using the modulation signal provided by the second signal source module, and outputs a third optical signal to the amplifier module; The amplifier module is used to amplify the third optical signal and output a fourth optical signal; The optical fiber link module is used to transmit the fourth optical signal and output the fifth optical signal to the single photon detection module; The single photon detection module is used to perform scanning chromatography on the fifth optical signal according to the external gating signal provided by the third signal source module, and output an electrical signal to the data processing module; The data processing module is used to process electrical signals, reconstruct waveforms, and extract key time domain information.

2. The device according to claim 1, characterized in that The light source module is a single-frequency continuous light laser.

3. The device according to claim 1, characterized in that The first signal source module generates a time signal to be transmitted.

4. The device according to claim 1, characterized in that The first modulation module is an intensity modulator.

5. The device according to claim 1, characterized in that The modulation signal generated by the second signal source module is Gaussian white noise.

6. The device according to claim 1, characterized in that The second modulation module is a phase modulator, which widens the line width of the second optical signal and increases the Brillouin scattering threshold of the optical fiber.

7. The device according to claim 1, characterized in that The single-photon detection module is a single-photon detector whose photon number cannot be distinguished, and the output electrical signal is the photon counting rate.

8. The device according to claim 1, characterized in that The single-photon detection module achieves fine scanning of the rising edge of the fifth optical signal by adjusting the gate signal delay.

9. The device according to claim 1, characterized in that The data processing module records the count rates under different relative time delays and completes the fitting to achieve the fifth optical signal waveform recovery and key time domain information extraction.

10. A method for extracting extremely weak light time domain information based on single photon detection, implemented based on the device according to any one of claims 1 to 9, characterized in that the steps include: The time base module generates an electrical signal C and connects to the first signal source module, generates an electrical signal D and connects to the third signal source module to achieve clock synchronization; The first signal source module generates an electrical signal A and connects it to the first modulation module as a modulation signal; The light source module generates a first optical signal and connects to the first modulation module; After the first optical signal is intensity modulated in the first modulation module, clock information is loaded and a second optical signal is output to the second modulation module; The second signal source module generates an electrical signal and connects to the second modulation module as a modulation signal; After the second optical signal is phase modulated by the second modulation module, the laser line width increases and a third optical signal is output; The third optical signal enters the amplifier module and outputs a fourth optical signal after being amplified; The fourth optical signal is connected to the optical fiber link module, and outputs a fifth optical signal after passing through the optical fiber link; The third signal source module generates an electrical signal E and is connected to the single photon detection module as an external gating signal to control the gating signal; The fifth optical signal is connected to the single-photon detection module, and is scanned and tomographically processed by an external electrical signal E, and an electrical signal F is output after detection; The electrical signal F is connected to the data processing module to complete waveform reconstruction and key time domain information extraction.

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