A method and device for extracting time-domain information of extremely weak light based on single-photon detection

Abstract

The application discloses a kind of weak light time domain information extraction method and device based on single-photon detection, belong to optical communication and quantum time-frequency transmission technical field.The application is to solve the problem of high link attenuation and far end extremely weak light difficult to detect in no relay amplification long-distance time transmission, mainly using single-photon detection technology combined with scanning tomography technology, through time base module synchronous clock signal, cooperate light source, modulation, amplification, optical fiber transmission and single-photon detection module, the reconstruction of extremely weak light waveform and key time domain information extraction are realized.The application can effectively transmit time-frequency information in no relay amplification long-distance optical communication, overcome the detection problem of extremely weak light.

Description

TECHNICAL FIELD

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

[0002] High-precision long-distance time-frequency transfer plays an indispensable role in satellite navigation, geodesy, time synchronization and other fields. Optical fiber, as a basic infrastructure with long transmission distance and large coverage, is very suitable as a medium for long-distance time-frequency transfer. In existing technical solutions, long-distance time-frequency transfer can be achieved through optical relay of "receiving optical signal-optical power supply-retransmitting optical signal" or electrical relay of "optical-electric conversion-electric amplification-electric-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 environments, such as remote suburban areas where infrastructure is extremely weak, the laying of relay nodes is challenging; in scenarios where long-distance signal regeneration technology is scarce, such as deserts, plateaus, polar regions, and seabed, optical cable laying can only support point-to-point transmission; in emergency applications, such as natural disasters, emergency communication and other sudden scenarios, the flexibility of relay laying is greatly reduced. These scenarios have an urgent need for high-precision relay-free time-frequency signal transmission technology.

[0003] In long-distance signal transmission without relay amplification, compared with dispersion, nonlinear effects and other influences, the high loss of the optical fiber link becomes the main limiting factor. To address the high loss in long-distance signal transmission, there are two typical schemes in classical optical communication for improving transmission distance without relay: 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 utilize the amplification capability of the avalanche effect for weak optical current to recover the weak signal. However, in high-precision time-frequency transfer, both of the above schemes have theoretical and experimental difficulties. At the transmitting end, the above scheme requires the use of an ultra-high linewidth light source to increase the stimulated Brillouin scattering threshold, thereby increasing the input fiber optical power, which has considerable limitations in experiments. At the receiving end, on the one hand, the limited gain-bandwidth product requires a balance and trade-off between high gain and sufficient detection bandwidth, i.e., obtaining sufficient energy of the signal at the receiving end and maintaining 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, losing the detailed time-domain information of the pulse. In high-precision time-frequency transfer, the waveform of the transferred signal needs to be detected to obtain key information such as phase jitter, rising edge position for stability evaluation and time synchronization. Therefore, there is still a considerable distance between the relay-free solution in classical optical communication and the demand for high-precision time-frequency transfer. SUMMARY

[0004] The application aims to provide a single-photon detection-based extremely weak light time-domain information extraction method and device, and solve the problems of high link attenuation and difficult detection of extremely weak light at a remote end in a non-relay amplification long-distance time transfer.

[0005] The technical solution adopted by the application 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, a fiber link module, a single-photon detection module, a third signal source module, a data processing module, and a time base module, wherein,

[0007] The time base module is used to realize clock synchronization of the first signal source module and the third signal source module through electrical signals;

[0008] The first signal source module is used to generate a modulation signal of the first modulation module;

[0009] The third signal source module is used to generate an external gating signal of the single-photon detection module;

[0010] The second signal source module is used to generate a modulation signal of the second modulation module;

[0011] The light source module is used to generate a first optical signal and transmit the first optical signal to the first modulation module;

[0012] The first modulation module modulates the first optical signal by using the modulation signal provided by the first signal source module, and outputs a second optical signal to the second modulation module;

[0013] The second modulation module phase-modulates the second optical signal by using the modulation signal provided by the second signal source module, and outputs a third optical signal to the amplifier module;

[0014] The amplifier module is used to amplify the third optical signal and output a fourth optical signal;

[0015] The fiber link module is used to transmit the fourth optical signal and output a fifth optical signal to the single-photon detection module;

[0016] The single-photon detection module is used to scan and analyze 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;

[0017] The data processing module is used to process the electrical signal, reconstruct a waveform, and extract key time-domain information.

[0018] Further, the light source module is a single-frequency continuous light laser.

[0019] Further, the first signal source module generates a time signal to be transmitted.

[0020] Further, the first modulation module is an intensity modulator.

[0021] Further, the second signal source module generates a modulation signal which is Gaussian white noise.

[0022] Further, the second modulation module is a phase modulator, which expands the line width of the second optical signal and increases the fiber Brillouin scattering threshold.

[0023] Further, the amplifier module is an optical amplifier.

[0024] Further, the single-photon detection module is a photon-number-resolving single-photon detector, and the output electrical signal is a photon counting rate.

[0025] Further, the single-photon detection module realizes fine scanning of the rising edge of the fifth optical signal by adjusting the gate signal delay.

[0026] Further, the data processing module records the counting rate under different relative delays, completes fitting, realizes waveform recovery of the fifth optical signal, and extracts key time-domain information.

[0027] A weak light time-domain information extraction method based on single-photon detection, comprising the following steps:

[0028] The time base module generates an electrical signal C and inputs it into the first signal source module, and generates an electrical signal D and inputs it into the third signal source module, to realize clock synchronization.

[0029] The first signal source module generates an electrical signal A and inputs it into the first modulation module as a modulation signal.

[0030] The light source module generates a first optical signal and inputs it into the first modulation module.

[0031] 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.

[0032] The second signal source module generates an electrical signal and inputs it into the second modulation module as a modulation signal.

[0033] After the second optical signal is phase-modulated by the second modulation module, the laser line width is increased, and a third optical signal is output.

[0034] The third optical signal enters the amplifier module, is amplified, and a fourth optical signal is output.

[0035] The fourth optical signal is input into the optical fiber link module, is transmitted through the optical fiber link, and a fifth optical signal is output.

[0036] The third signal source module generates an electrical signal E and inputs the electrical signal E as an applied gating signal into the single-photon detection module to control the gating signal.

[0037] The fifth optical signal inputs the single-photon detection module, and the single-photon detection module performs scanning tomography through the applied electrical signal E, and outputs an electrical signal F after detection.

[0038] The electrical signal F inputs the data processing module to complete waveform reconstruction and key time domain information extraction.

[0039] The present application has the following beneficial effects.

[0040] 1. The present application is based on single-photon detection technology, and can realize reconstruction of extremely weak light waveform and extraction of key time domain information.

[0041] 2. The present application can use ordinary continuous laser light source and all-loss optical fiber link without gain, avoiding high-cost laser gain equipment and simplifying the system structure.

[0042] 3. The present application overcomes the detection difficulty of extremely weak light through scanning tomography technology, and can effectively transmit time-frequency information in long-distance optical communication without relay amplification.

[0043] 4. The present application can use photon number indistinguishable detector to realize high-precision time domain information extraction, and has higher detection sensitivity and precision.

[0044] 5. The present application has wide application prospect, and can be applied to optical communication, quantum time-frequency transmission and other fields. DETAILED DESCRIPTION

[0045] Figure 1 The present application is a module composition diagram of the extremely weak light time domain information extraction device based on single-photon detection.

[0046] Figure 2 The present application is a scanning process schematic diagram in the extremely weak light waveform tomography recovery based on single-photon detection.

[0047] Figure 3 The present application is a module composition diagram of the extremely weak light time domain information extraction device based on single-photon detection.

[0048] Figure 4 The present application is a scanning process schematic diagram in the extremely weak light waveform tomography recovery based on single-photon detection. DETAILED DESCRIPTION

[0049] In order to make the technical features and advantages or technical effects of the above technical solutions of the present application more obvious and easy to understand, the following will be described in detail with reference to the drawings.

[0050] The application discloses a device for extracting time domain information of extremely weak light based on single photon detection, which comprises 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, a 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. Figure 1 The specific steps are as follows.

[0051] (1) The electrical signal C generated by the time base module 11 is connected to the first signal source module 3 and used 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 and used for clock synchronization of the third signal source module 9.

[0052] (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.

[0053] (3) A single-frequency continuous light laser is selected to form the light source module 1, and the first optical signal generated by the light source module 1 is connected to the first modulation module 2.

[0054] (4) After the first optical signal is intensity-modulated by the first modulation module 2 (for example, an intensity modulator), the source end clock information is loaded, and the second optical signal is output to the second modulation module 4.

[0055] (5) The electrical signal B (for example, 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.

[0056] (6) After the second optical signal is connected to the second modulation module 4 (for example, a phase modulator) and phase-modulated, the threshold of stimulated Brillouin scattering is increased, and the third optical signal is output.

[0057] (7) The third optical signal is connected to the amplifier module 6 (for example, an optical amplifier), amplified and output as the fourth optical signal.

[0058] (8) The fourth optical signal is connected to the fiber link module 7, output as the fifth optical signal after passing through the fiber link; the fiber link module 7 is a common single-mode optical fiber and does not contain any form of amplification or gain, and is a full-loss link; the fifth optical signal output by the fiber link module 7 is extremely weak light signal of single photon energy level, and the waveform cannot be observed through the existing detection scheme.

[0059] (9) After clock synchronization, 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 and used for external signal control.

[0060] (10) The fifth optical signal is connected to a single-photon detection module 8 (for example, a photon-number non-distinguishable single-photon detector), and a scanning tomography is realized through an electrical signal E, including a coarse scanning process and a fine scanning process. The rising edge of the fifth optical signal is scanned by adjusting the time delay of the gate signal, and an electrical signal F (for example, a photon counting rate) is output.

[0061] (11) The electrical signal F is connected to a data processing module 10. The data processing module 10 records the counting rate under different relative time delays, and completes fitting, so as to realize the waveform recovery of the fifth optical signal and the extraction of key time domain information.

[0062] 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 of the electrical signal E and the electrical signal A is adjustable. By adjusting the relative phase, the relative time delay of the electrical signal E and the fifth optical signal is equivalent changed, so as to realize the coarse scanning of the fifth optical signal.

[0063] The scanning process in the extremely weak light waveform tomography recovery based on single-photon detection of the device is shown in FIG. 1, and the specific description is as follows. Figure 2

[0064] (1) Figure 2 FIG. 1(a) shows the waveform in one period of the coarse scanning process. 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, the relative time relationship between the electrical signal E and the fifth optical signal is changed by a step size , and an electrical signal F reflecting the counting rate at different positions is obtained. The phase of the electrical signal E is adjusted so that the electrical signal F is located near the position where a significant increase occurs, and the phase of the electrical signal E is fixed.

[0065] (2) Figure 2 FIG. 1(b) shows the waveform in one period of the fine scanning process. The period of the electrical signal E is the same as that of the fifth optical signal, and the width is . By adjusting the time delay of the gate signal provided in the single-photon detection module 8, the relative time relationship between the electrical signal E and the fifth optical signal is changed by a step size , and an electrical signal F reflecting the counting rate at different positions of the rising edge is obtained.

[0066] A specific embodiment is given below.

[0067] In this embodiment, the module composition and signal processing process of the device of the application are shown in FIG. 2, and the specific processing steps are as follows. Figure 3

[0068] (1) A 10 MHz sinusoidal wave signal generated by a time base module 11 is connected to a first signal source module 3 and a third signal source module 9 as an electrical signal C and an electrical signal D respectively, for realizing clock synchronization. ​​

[0069] (2) The first signal source module 3 generates a period after clock synchronization. Duty cycle The square wave clock information is used as electrical signal A and input to the first modulation module 2.

[0070] (3) Light source module 1 generates linewidth The continuous light laser is used as the first optical signal and is input into the first modulation module 2.

[0071] (4) After the first optical signal is intensity modulated by the intensity modulator that serves as the first modulation module 2, it is loaded with square wave clock information and is used as the second optical signal to access the second modulation module 4.

[0072] (5) The 250 MHz Gaussian white phase noise generated by the second signal source module 5 is used as electrical signal B and input to the second modulation module 4.

[0073] (6) After the second optical signal is phase-modulated by the phase modulator, which serves as the second modulation module 4, the laser linewidth increases and the Brillouin scattering threshold increases to [value missing]. The third optical signal is output and connected to amplifier module 6.

[0074] (7) After the third optical signal is amplified by the EDFA, which is used as amplifier module 6, the fourth optical signal is output and connected to the optical fiber link module 7.

[0075] (8) After the fourth optical signal passes through the fiber optic link module 7 without any amplification, the fifth optical signal is output and connected to the single-photon detection module 8.

[0076] (9) The third signal source module 9 generates a period after clock synchronization. Duty cycle The square wave is used as an electrical signal E to enter the single-photon detection module 8, so as to be used as an external gating signal for single-photon detection.

[0077] (10) After the fifth optical signal passes through the single-photon detection module 8, the phase of the electrical signal E is adjusted. A coarse scan is performed, followed by a fine scan by adjusting the gate signal delay within the single-photon detection module 8 to alter the relative delay of the electrical signal E compared to the fifth optical signal. The scanning tomography of the fifth optical signal is completed, and the output is the count rate as the electrical signal F. Connect to data processing module 10.

[0078] (11) After the electrical signal F is input to the data processing module 10, the data processing module 10 counts the rising edge rate. Fitting using the Sigmoid function:

[0079]

[0080] wherein , , are fitting parameters. The count rate under different relative time delays is proportional to the intensity at different positions of the very weak light. The reconstruction of the waveform and the extraction of the key time-domain information are completed by the above fitting and threshold setting.

[0081] The process of scanning tomography for the fifth light signal is realized by adjusting the electrical signal E as shown in FIG. 5 (not drawn to scale to highlight key information), which is described as follows. Figure 4

[0082] (1) Figure 2 The (a) of FIG. 1 is a coarse scanning process, and the waveform in one period is shown in the figure. The period of the electrical signal E is the same as that of the fifth light signal, and the width is . By adjusting the phase of the electrical signal E in the range of 0 to 360°, the relative time delay between the electrical signal E and the fifth light signal is changed by a step size , and the electrical signal F reflecting the count rate at different positions is obtained. The phase of the electrical signal E is adjusted so that the electrical signal F is located in the vicinity of the obvious increase, and the phase of the electrical signal E is fixed.

[0083] (2) Figure 2 The (b) of FIG. 1 is a fine scanning process, and the waveform in one period is shown in the figure. The period of the electrical signal E is the same as that of the fifth light signal, and the width is . By adjusting the time delay of the gate signal provided in the single-photon detection module 8, the relative time delay between the electrical signal E and the fifth light signal is changed by a step size , and the electrical signal F reflecting the count rate at different positions of the rising edge is obtained.

[0084] Although the present application has been disclosed with the above embodiments, it is not intended to limit the present application, and any appropriate modification or equivalent replacement made by those skilled in the art to the technical solutions of the present application shall be covered within the protection scope of the present application, and the protection scope of the present application is defined by the claims.​

Claims

1. An apparatus for extracting time-domain information of extremely weak light based on single-photon detection, characterized in that, The system 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, a fiber link module, a single-photon detection module, a third signal source module, a data processing module, and a time base module. The time base module is configured to synchronize the clock of the first signal source module and the third signal source module through an electrical signal. The first signal source module is configured to generate a modulation signal for the first modulation module. The third signal source module is configured to generate an external gating signal for the single-photon detection module. The second signal source module is configured to generate a modulation signal for the second modulation module, which is a Gaussian white noise. The light source module is configured to generate a first optical signal and transmit the first optical signal to the first modulation module. The first modulation module is an intensity modulator configured to perform intensity modulation on the first optical signal using the modulation signal provided by the first signal source module, and output a second optical signal to the second modulation module. The second modulation module is a phase modulator configured to perform phase modulation on the second optical signal using the modulation signal provided by the second signal source module, broaden the line width of the second optical signal, increase the fiber Brillouin scattering threshold, and output a third optical signal to the amplifier module. The amplifier module is configured to amplify the third optical signal and output a fourth optical signal. The fiber link module is configured to transmit the fourth optical signal and output a fifth optical signal to the single-photon detection module. The single-photon detection module is a photon-number-resolving single-photon detector configured to perform scanning tomography on the fifth optical signal according to the external gating signal provided by the third signal source module, and output an electrical signal photon counting rate to the data processing module. The scanning tomography performed by the single-photon detection module includes a coarse scanning process and a fine scanning process. In the coarse scanning process, the single-photon detection module adjusts the phase of the external gating signal, changes the relative time relationship between the external gating signal and the fifth optical signal by a preset step, generates a new electrical signal, and reflects the counting rate at different positions. In the fine scanning process, the single-photon detection module adjusts the internal gate signal time delay, changes the relative time relationship between the external gating signal and the fifth optical signal by another preset step, generates a new electrical signal, and reflects the counting rate at different positions of the rising edge. The data processing module is configured to process the electrical signal, reconstruct the waveform, and extract key time domain information. The data processing module uses a Sigmoid function to fit the counting rate at different positions of the rising edge.

2. The apparatus of claim 1, wherein, The light source module is a single-frequency continuous light laser.

3. The apparatus of claim 1, wherein, The first signal source module generates a to-be-transferred time signal.

4. The apparatus of claim 1, wherein, The data processing module records the counting rate under different relative time delays, completes fitting, realizes waveform recovery of the fifth optical signal, and extracts key time domain information.

5. A method for extracting time-domain information of extremely weak light based on single-photon detection, implemented based on the device of any one of claims 1-4, characterized in that the steps of The system comprises: The time base module generates an electrical signal C and inputs the electrical signal C into the first signal source module, generates an electrical signal D and inputs the electrical signal D into the third signal source module, and realizes clock synchronization. The first signal source module generates an electrical signal A and inputs the electrical signal A into the first modulation module as a modulation signal. The light source module generates a first optical signal and inputs the first optical signal into the first modulation module. The first optical signal is intensity-modulated in the first modulation module, loads clock information, and outputs a second optical signal to the second modulation module. The second signal source module generates an electrical signal and inputs the electrical signal into the second modulation module as a modulation signal. The second modulation module modulates the second optical signal with a modulation signal provided by the second signal source module, broadens the line width of the second optical signal, increases the fiber Brillouin scattering threshold, and outputs a third optical signal; The third optical signal enters the amplifier module, is amplified, and outputs a fourth optical signal; The fourth optical signal enters the optical fiber link module, passes through the optical fiber link, and outputs a fifth optical signal; The third signal source module generates an electrical signal E and inputs the electrical signal E into the single-photon detection module as an external gating signal, for controlling the gating signal; The fifth optical signal enters the single-photon detection module, is scanned and chromatographed by the external electrical signal E, is detected, and outputs an electrical signal F, which is a photon counting rate; the scanning and chromatography performed by the single-photon detection module includes a coarse scanning process and a fine scanning process; in the coarse scanning process, the single-photon detection module adjusts the phase of the electrical signal E, changes the relative time relationship between the electrical signal E and the fifth optical signal by a preset step, generates the electrical signal F, and reflects the counting rates at different positions; in the fine scanning process, the single-photon detection module adjusts the internal gating signal delay, changes the relative time relationship between the electrical signal E and the fifth optical signal by another preset step, generates a new electrical signal F, and reflects the counting rates at different positions of the rising edge; The electrical signal F enters the data processing module, and waveform reconstruction and key time domain information extraction are completed; wherein the data processing module fits the counting rates at different positions of the rising edge by using a Sigmoid function.

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