Linear multi-channel fiber array and arrayed single photon detection system

Abstract

The application provides a linear multi-channel optical fiber array and an arrayed single-photon detection system, the linear multi-channel optical fiber array comprises an optical fiber array and an optical fiber combiner, a receiving end of the optical fiber array is arranged in an optical fiber array probe, and an output end of the optical fiber array is connected with an input end of the optical fiber combiner; the optical fiber array comprises a set number of optical fiber channels, physical lengths of the set number of optical fiber channels are in an increasing arithmetic sequence, and the receiving ends of the set number of optical fiber channels are arranged in sequence at a fixed interval. The linear multi-channel optical fiber array and the arrayed single-photon detection system provided by the embodiment of the application can be used for collecting photons from different transverse positions, realizing a mapping relationship between a transverse position and a transverse momentum, and thus overcoming the limitation of the prior art in detecting the transverse space of photons.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, specifically to a linear multi-channel fiber array and an array-type single-photon detection system. Background Technology

[0002] With the development of single-photon detection technology, related systems are gradually adopting weakly coherent light sources to replace traditional entangled photon pairs, which improves system stability and practicality while ensuring interference visibility.

[0003] Existing displacement measurement techniques based on Hong–Ou–Mandel (HOM) interferometry have limitations when detecting lateral spatial displacement. When the displacement to be measured exceeds the lateral coherence length of the photons, the two photons become spatially indistinguishable, leading to a sharp decrease in interferometric visibility. Traditional bucket detection completely loses its lateral spatial resolution, causing the coincidence counting signal to degenerate into a constant background independent of displacement, resulting in a significant reduction or even failure of measurement sensitivity. To overcome this problem, existing technologies introduce momentum-resolved detection mechanisms, reconstructing displacement information by analyzing the lateral momentum distribution of the photons after interference. However, such solutions face two intractable engineering bottlenecks: First, mechanical scanning momentum resolution schemes require point-by-point sampling of different momentum channels, resulting in extremely low data acquisition efficiency (acquisition time increases linearly with the required resolution). Furthermore, the vibrations and drift introduced by mechanical motion severely affect system stability, making dynamic or real-time measurements impossible. Second, while fixed sparse pixel array schemes based on Single-Photon Avalanche Diodes (SPADs) avoid mechanical scanning, sampling only at a limited number of preset momentum points leads to incomplete momentum space information. Reconstruction still relies on scanning the displacement itself, resulting in high system complexity and an almost exponentially increasing cost with the number of pixels, poor scalability, and difficulty in adapting to high-dimensional parallel detection requirements. Therefore, overcoming the limitations of HOM interferometry-based displacement measurement technology in lateral spatial displacement detection has become a crucial issue urgently needing resolution in this field. Summary of the Invention

[0004] To address the problems in the prior art, embodiments of the present invention provide a linear multi-channel fiber array and an array-type single-photon detection system, which can at least partially solve the problems existing in the prior art.

[0005] In a first aspect, the present invention proposes a linear multi-channel fiber array, comprising a fiber array and a fiber combiner, wherein:

[0006] The receiving end of the fiber array is disposed in the fiber array probe, and the output end of the fiber array is connected to the input end of the fiber combiner; the fiber array includes a set number of fiber channels, the physical lengths of the set number of fiber channels are in an increasing arithmetic sequence, and the receiving ends of the set number of fiber channels are arranged sequentially at a fixed interval.

[0007] Furthermore, the effective coverage width of the linear multi-channel fiber array is W=(N-1)p, where W represents the effective coverage width, N represents the set number, and p represents the center distance between adjacent fiber channels.

[0008] Furthermore, the set quantity satisfies the following constraint relationship:

[0009] Where N represents the set quantity. This indicates the repetition frequency of the laser pulse. This indicates that a safety margin has been reserved. This indicates the time delay between adjacent fiber optic channels. , Represents the group refractive index of the optical fiber. Represents the speed of light. This represents the length difference between adjacent fiber optic channels. , This indicates the pulse width of a single laser pulse.

[0010] Secondly, this invention proposes an array-type single-photon detection system, comprising a light source module, an optical path module, a detection module, and a displacement calculation module. The detection module comprises the linear multi-channel fiber array described in any of the above embodiments, wherein: The light source module is used to output weak coherent light pulses and time synchronization signals; The optical path module is used to generate two weakly coherent optical pulses that satisfy the two-photon interference condition based on the weakly coherent optical pulses. The detection module is used to perform photon detection on each light source generated based on the interference input light in parallel through multiple detection channels to obtain the electrical signal corresponding to each detection channel, and to obtain the photon event timestamp corresponding to each detection channel based on the electrical signal and time synchronization signal corresponding to each detection channel; wherein, the interference input light is generated after the two weakly coherent light pulses interfere; one of the detection channels includes a linear multi-channel fiber array; The displacement calculation module is used to determine the two-photon interference event type based on the photon event timestamps corresponding to each detection channel, and to obtain the displacement value according to the two-photon interference event type, the lateral detection position difference, and the displacement estimation model; wherein, the lateral detection position difference is obtained based on the photon event timestamps corresponding to the detection channels including linear multi-channel fiber arrays in each detection channel; the displacement estimation model is preset.

[0011] Furthermore, the light source module includes a laser, an arbitrary waveform generator, and an intensity modulator, wherein: The output terminal of the laser is connected to the input terminal of the intensity modulator; The first output channel of the arbitrary waveform generator outputs an electrical pulse signal to the laser, causing the laser to output a phase-randomized pulsed light signal; the second output channel of the arbitrary waveform generator outputs a chopping signal to the intensity modulator, causing the intensity modulator to compress the pulse width of the pulsed light signal and output the weakly coherent light pulse; the third output channel of the arbitrary waveform generator outputs a time synchronization signal.

[0012] Furthermore, the optical path module includes an optical fiber beam splitter, a first optical path adjustment unit, and a second optical path adjustment unit, wherein: The input end of the fiber optic beam splitter is connected to the output end of the light source module, and is used to output a first optical signal to the first optical path adjustment unit and output a second optical signal to the second optical path adjustment unit based on the weak coherent optical pulse. The first optical path adjustment unit is used to adjust the polarization state of the first optical signal, and the second optical path adjustment unit is used to adjust the optical path of the second optical signal, so that the first optical path adjustment unit and the second optical path adjustment unit output two weakly coherent optical pulses that satisfy the two-photon interference condition.

[0013] Furthermore, the first optical path adjustment unit includes a first polarization controller, a first collimator, a first polarization beam splitter, and a first plano-convex lens, and the propagation optical path of the first optical signal passes through the first polarization controller, the first collimator, the first polarization beam splitter, and the first plano-convex lens in sequence.

[0014] Furthermore, the second optical path adjustment unit includes an optical fiber of a preset length, an optical delay unit, a second polarization controller, a second collimator, a displacement stage, a second polarization beam splitter, and a second plano-convex lens. The propagation optical path of the second optical signal passes sequentially through the optical fiber of the preset length, the optical delay unit, the second polarization controller, the second collimator, the second polarization beam splitter, and the second plano-convex lens. The second collimator is disposed on the displacement stage.

[0015] Furthermore, the detection module includes a first beam splitter, a second beam splitter, a first optical fiber, a second optical fiber, a linear multi-channel fiber array, a first single-photon detector, a second single-photon detector, a third single-photon detector, and a time-to-digital converter, wherein: The input end of the first beam splitter receives interference input light, the first optical signal output from the first output end of the first beam splitter is incident on the input end of the first optical fiber, the second optical signal output from the second output end of the first beam splitter is incident on the input end of the second beam splitter, the output end of the first optical fiber is connected to the input end of the first single-photon detector, the third optical signal output from the first output end of the second beam splitter is incident on the input end of the second optical fiber, the fourth optical signal output from the second output end of the second beam splitter is incident on the input end of the linear multi-channel fiber array, the output end of the second optical fiber is connected to the input end of the second single-photon detector, and the output end of the linear multi-channel fiber array is connected to the input end of the third single-photon detector. The time-to-digital converter is connected to the output terminals of the first single-photon detector, the second single-photon detector, the third single-photon detector, and the light source module, respectively. The time-to-digital converter receives the time synchronization signal from the light source module. The first optical fiber and the first single-photon detector constitute a first detection channel, the second optical fiber and the second single-photon detector constitute a second detection channel, and the linear multi-channel fiber array and the third single-photon detector constitute a third detection channel. The third detection channel is used to detect photons from different lateral positions.

[0016] Furthermore, the linear multi-channel fiber array includes a set number of single-mode fibers and fiber couplers. The cores of the set number of single-mode fibers are arranged laterally at fixed intervals to cover the size of the light spot generated at the input end of the linear multi-channel fiber array by the fourth optical signal output from the second output end of the second beam splitter. The physical lengths of the set number of single-mode fibers are in an increasing arithmetic sequence. The output end of each single-mode fiber is connected to the input end of the fiber coupler, and the output end of the fiber coupler is connected to the input end of the third single-photon detector.

[0017] Furthermore, the shift estimation model includes:

[0018] in, This represents the probability of a two-photon interference event. This indicates the lateral detection position difference on the detection plane. Indicates the beam radius on the detection plane. Indicates displacement parameters, This represents an effective parameter that comprehensively characterizes the interference quality of a real system. , Indicates wavelength. This represents the wavefront curvature radius at the probe plane. , Indicates the transmission distance. Indicates Rayleigh length, , Indicates the waist radius, , , The standard deviation represents the transverse spatial distribution of photons on the beam waist surface; the two-photon interference event type is a beam-gathering event. The two-photon interference event type is an anti-beaming event. , [] represents the natural exponential function, and cosh[] represents the hyperbolic cosine function. The average photon number constant, , .

[0019] Thirdly, the present invention provides a displacement measurement method based on single-photon detection, employing the array-type single-photon detection system described in any of the above embodiments, comprising: The light source module outputs weakly coherent light pulses and a time synchronization signal; The optical path module generates two weakly coherent optical pulses that satisfy the two-photon interference condition based on the weakly coherent optical pulses. The two weakly coherent optical pulses interfere with each other in the detection module and are then detected. The detection module performs photon detection on each path of light generated based on the interference input light in parallel through multiple detection channels to obtain the electrical signal corresponding to each detection channel, and obtains the photon event timestamp corresponding to each detection channel based on the electrical signal and time synchronization signal corresponding to each detection channel. The displacement calculation module is used to determine the two-photon interference event type based on the photon event timestamps corresponding to each detection channel, and to obtain the displacement value according to the two-photon interference event type, the lateral detection position difference, and the displacement estimation model; wherein, the lateral detection position difference is obtained based on the photon event timestamps corresponding to the detection channels used to detect photons from different lateral positions in each detection channel.

[0020] Furthermore, each detection channel includes a first detection channel, a second detection channel, and a third detection channel; correspondingly, determining the two-photon interference event type based on the photon event timestamps corresponding to each detection channel includes: If the photon event timestamp corresponding to the first detection channel matches the photon event timestamp corresponding to the third detection channel, then the two-photon interference event type is determined to be a beam-gathering event; If the photon event timestamp corresponding to the second detection channel matches the photon event timestamp corresponding to the third detection channel, then the two-photon interference event type is determined to be an anti-beaming event.

[0021] Furthermore, based on the photon event timestamps corresponding to the detection channels used to detect photons from different lateral positions in each detection channel, the following are obtained: The detection delay time is obtained based on the photon event timestamps corresponding to the detection channels used to detect photons from different lateral positions and the reference time base. Based on the detection delay time and the correspondence between the detection delay time and the spatial channel, the spatial channel corresponding to the detection delay time is obtained; wherein, the correspondence between the detection delay time and the spatial channel is pre-established; The lateral detection position difference is obtained based on the spatial channel corresponding to the detection delay time and the correspondence between the spatial channel and the lateral position difference; wherein, the detection channel for detecting photons from different lateral positions includes multiple spatial channels; the correspondence between the spatial channel and the lateral position difference is established in advance.

[0022] The linear multi-channel fiber array and array-type single-photon detection system provided in this invention include a fiber array and a fiber combiner. The receiving end of the fiber array is disposed in the fiber array probe, and the output end of the fiber array is connected to the input end of the fiber combiner. The fiber array includes a set number of fiber channels, the physical lengths of which are in an increasing arithmetic sequence. The receiving ends of the set number of fiber channels are arranged sequentially at a fixed interval, which can be used to collect photons from different lateral positions and realize the mapping relationship between lateral position and lateral momentum, thereby overcoming the limitations of existing technologies in detecting photons in the lateral space. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of a linear multi-channel fiber array provided in an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the structure of an array-type single-photon detection system provided in an embodiment of the present invention.

[0026] Figure 3This is a schematic diagram of the structure of a light source module provided in an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of the structure of an optical path module provided in an embodiment of the present invention.

[0028] Figure 5 This is a schematic diagram of the optical path module provided in another embodiment of the present invention.

[0029] Figure 6 This is a schematic diagram of the structure of a detection module provided in an embodiment of the present invention.

[0030] Figure 7 This is a schematic diagram of the structure of a linear multi-channel fiber array provided in an embodiment of the present invention.

[0031] Figure 8 This is a flowchart illustrating a displacement measurement method based on single-photon detection provided in an embodiment of the present invention.

[0032] Figure 9 This is a flowchart illustrating a displacement measurement method based on single-photon detection provided in an embodiment of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other. The acquisition, storage, use, and processing of data in the technical solutions of this application all comply with the relevant provisions of laws and regulations. The user information in the embodiments of this application is obtained through legal and compliant means, and the acquisition, storage, use, and processing of user information have been agreed upon by the customer.

[0034] To facilitate understanding of the technical solution provided in this application, the relevant content of the technical solution in this application will be explained below.

[0035] Theoretical research and experimental results show that when two photons separated in the transverse space interfere at a beam splitter, if their spatial positions are not directly imaged, but their transverse momentum is measured under far-field conditions, the probability distribution of the two-photon coincidence count will exhibit periodic oscillations with the transverse momentum difference. The oscillation period is inversely proportional to the spatial separation between the photons. This indicates that the transverse displacement information is not lost due to spatial distinguishability, but is fully encoded in the interference structure of momentum space.

[0036] Although the aforementioned physical principles have been verified, existing space quantum beat interferometry schemes still generally face significant technical bottlenecks in practical engineering implementation. These bottlenecks primarily stem from the difficulty in simultaneously meeting the requirements of high resolution, high efficiency, and high stability within the detection architecture itself. Currently, the technical solutions used to acquire spatial or momentum-resolved information mainly fall into two categories: one is to use mechanical scanning to measure different spatial locations point-by-point using a single-channel detector; the other is to arrange a limited number of multi-pixel single-photon detectors on the detection plane to collect photon signals from different locations in parallel in space.

[0037] Both of these approaches have significant drawbacks. Mechanical scanning requires point-by-point movement of optical elements, making data acquisition essentially a serial operation with low efficiency, making real-time or dynamic measurements difficult, and placing extremely high demands on the system's mechanical stability and long-term drift control. While multi-pixel array detection avoids mechanical movement to some extent, its pixel count is typically limited by the cost and manufacturing capabilities of single-photon detectors, resulting in insufficient spatial sampling density and limited coverage. Furthermore, it faces engineering challenges such as multi-channel synchronization, dead-time conflicts, and a significant increase in system complexity. These problems are particularly pronounced under single-photon or low-light conditions.

[0038] Therefore, in addressing the problems of low measurement efficiency due to the use of single-channel mechanical scanning or incomplete momentum information acquisition and high system cost caused by the use of fixed sparse detector arrays in existing displacement measurement schemes based on momentum space quantum beat interferometry, this application proposes an array-type single-photon detection system that can achieve high-resolution and high-efficiency acquisition of spatially distributed photon information without mechanical scanning and large-scale detector arrays, and achieve efficient parallel acquisition of spatial or momentum distributed photon information to meet the practical application requirements of high precision and rapid measurement.

[0039] Figure 1 This is a schematic diagram of the structure of a linear multi-channel fiber optic array provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the linear multi-channel fiber array provided in this embodiment of the invention includes a fiber array 100-1 and a fiber combiner 100-2, wherein: The receiving end of the fiber array 100-1 is disposed in the fiber array probe 100-1-1, and the output end of the fiber array 100-1 is connected to the input end of the fiber combiner 100-2. The fiber array 100-1 includes a set number of fiber channels 100-1-2, the physical lengths of the set number of fiber channels 100-1-2 are in an increasing arithmetic sequence, and the receiving ends of the set number of fiber channels 100-1-2 are arranged sequentially at a fixed interval.

[0040] Specifically, the receiving ends of each fiber optic channel 100-1-2 are arranged at a fixed interval p along the fiber optic array probe 100-1-1. The effective coverage width of the set number of fiber optic channels 100-1-2 is W, which can completely cover the light spot size at the input end of the linear multi-channel fiber optic array, thereby enabling the collection of photons from different lateral positions. The physical lengths of the set number of fiber optic channels 100-1-2 form an increasing arithmetic sequence, and the photon event timestamps obtained by photons passing through different fiber optic channels 100-1-2 are different. The output ends of the set number of fiber optic channels 100-1-2 are connected to the input end of the fiber optic combiner 100-2, and the output end of the fiber optic combiner 100-2 can be connected to a single-photon detector. The number of fiber optic channels 100-1-2 included in the fiber optic array 100-1 is set according to actual needs, and this embodiment of the invention does not limit it. The fiber optic channels 100-1-2 can be single-mode fiber.

[0041] In one embodiment, the length of the i-th fiber optic channel is:

[0042] in, Indicates the reference fiber optic channel length. This represents the length difference between adjacent fiber optic channels, and N represents the set quantity.

[0043] The additional length of the i-th fiber channel relative to the 1st fiber channel is:

[0044] The linear multi-channel fiber optic array provided in this embodiment of the invention includes a fiber optic array and a fiber optic combiner. The receiving end of the fiber optic array is disposed in the fiber optic array probe, and the output end of the fiber optic array is connected to the input end of the fiber optic combiner. The fiber optic array includes a set number of fiber optic channels, the physical lengths of which are in an increasing arithmetic sequence. The receiving ends of the set number of fiber optic channels are arranged sequentially at a fixed interval, which can be used to collect photons from different lateral positions and realize the mapping relationship between lateral position and lateral momentum, thereby overcoming the limitations of existing technologies in detecting photons in lateral space.

[0045] Based on the above embodiments, the effective coverage width of the linear multi-channel fiber array is further defined as W = (N-1)p, where W represents the effective coverage width, N represents the set number, and p represents the center distance between adjacent fiber channels.

[0046] Specifically, based on the set number N of the fiber channels 100-1-2 included in the linear multi-channel fiber array and the center distance p between adjacent fiber channels, the effective coverage width of the linear multi-channel fiber array can be determined as W=(N-1)p.

[0047] Based on the above embodiments, the set quantity further satisfies the following constraint relationship:

[0048] Where N represents the set quantity. This indicates the repetition frequency of the laser pulse. This indicates that a safety margin has been reserved. This indicates the time delay between adjacent fiber optic channels. , Represents the group refractive index of the optical fiber. Represents the speed of light. This represents the length difference between adjacent fiber optic channels. , This indicates the pulse width of a single laser pulse.

[0049] Specifically, the repetition frequency of the laser pulse Determined based on laser pulse, with a safety margin reserved. It is preset and set based on practical experience; this embodiment of the invention does not impose limitations. The time delay corresponding to adjacent fiber optic channels is based on... The calculated group refractive index of the fiber is... The speed of light is a constant. The length difference between adjacent fiber optic channels is a constant. The settings should be configured according to actual needs; this embodiment of the invention does not impose any limitations. The time delay between adjacent fiber optic channels should be sufficiently large to avoid overlap between two adjacent time peaks. Pulse width greater than that of a single laser pulse With reserved safety margin sum.

[0050] Figure 2 This is a schematic diagram of the structure of an array-type single-photon detection system provided in an embodiment of the present invention, as shown below. Figure 2 As shown, the array-type single-photon detection system provided in this embodiment of the invention includes a light source module 1, an optical path module 2, a detection module 3, and a displacement calculation module 4. The detection module 3 adopts the linear multi-channel fiber array described in any of the above embodiments, wherein: Light source module 1 is used to output weak coherent light pulses and time synchronization signals; Optical path module 2 is used to generate two weakly coherent optical pulses that satisfy the two-photon interference condition based on the weakly coherent optical pulses; The detection module 3 is used to perform photon detection on each light source generated based on the interference input light in parallel through multiple detection channels to obtain the electrical signal corresponding to each detection channel, and to obtain the photon event timestamp corresponding to each detection channel based on the electrical signal corresponding to each detection channel; wherein, the interference input light is generated after the two weakly coherent light pulses interfere; one of the detection channels includes a linear multi-channel fiber array; The displacement calculation module 4 is used to determine the two-photon interference event type based on the photon event timestamps corresponding to each detection channel, and to obtain the displacement value according to the two-photon interference event type, the lateral detection position difference, and the displacement estimation model; wherein, the lateral detection position difference is obtained based on the photon event timestamps corresponding to the detection channels including linear multi-channel fiber arrays in each detection channel; the displacement estimation model is preset.

[0051] Specifically, the light source module 1 can attenuate the coherent light emitted by the laser to obtain a weak coherent pulse (WCP). This application uses a weak coherent pulse instead of a single photon source to reduce cost and improve stability.

[0052] After receiving the weakly coherent optical pulse, optical path module 2 splits it into a first optical signal and a second optical signal. Then, it adjusts the polarization state and optical path of the first and second optical signals respectively, thereby outputting two weakly coherent optical pulses that satisfy the two-photon interference conditions. In this application, the two-photon interference conditions are: First, the two weakly coherent optical pulses are incident on the two input ports of the 50:50 beam splitter. Second, the time difference between the arrival times of the two weakly coherent optical pulses at the input ports of the 50:50 beam splitter is less than a time threshold, which can be a nanosecond or a picosecond. Third, the polarization states of the two weakly coherent optical pulses must be consistent.

[0053] Two weakly coherent light pulses satisfying the two-photon interference condition interfere within detection module 3, forming the interference input light. Detection module 3 splits the interference input light into multiple paths, each input to a detection channel for photon detection. These detection channels perform photon detection in parallel to improve detection efficiency. After each detection channel detects a photon event, it obtains the corresponding photon event timestamp. One of the detection channels includes a linear multi-channel fiber array, which is used to detect photons from different lateral positions.

[0054] The displacement calculation module 4 determines the two-photon interference event type based on the photon event timestamps corresponding to each detection channel. Each detection channel includes a third detection channel for detecting photons from different lateral positions. Based on the photon event timestamps corresponding to the third detection channel, the lateral detection position difference corresponding to the photons detected by the third detection channel can be determined. The displacement calculation module 4 calculates the displacement value based on the two-photon interference event type, the lateral detection position difference, and the displacement estimation model. The lateral detection position difference is equivalent to the momentum difference. The displacement calculation module 4 can be implemented using a host computer.

[0055] The array-type single-photon detection system provided in this invention includes a light source module, an optical path module, a detection module, and a displacement calculation module. The light source module outputs weakly coherent light pulses and a time synchronization signal. The optical path module generates two weakly coherent light pulses that satisfy the two-photon interference condition based on the weakly coherent light pulses. The detection module performs parallel photon detection on each of the light pulses generated based on the interference input light through multiple detection channels to obtain the electrical signal corresponding to each detection channel, and obtains the photon event timestamp corresponding to each detection channel based on the electrical signal corresponding to each detection channel. The interference input light is the two weakly coherent light pulses... The displacement is generated by the interference of weakly coherent optical pulses; one of the detection channels includes a linear multi-channel fiber array; the displacement calculation module is used to determine the two-photon interference event type based on the photon event timestamps corresponding to each detection channel, and obtain the displacement value according to the two-photon interference event type, the lateral detection position difference, and the displacement estimation model; wherein, the lateral detection position difference is obtained based on the photon event timestamps corresponding to the detection channels including the linear multi-channel fiber array in each detection channel; the displacement estimation model is preset, and the accuracy of displacement measurement is improved because photon detection can be performed in parallel. The cost of displacement measurement is reduced because a complex photon detection system is not required.

[0056] Figure 3 This is a schematic diagram of the structure of a light source module provided in an embodiment of the present invention, as shown below. Figure 3 As shown, based on the above embodiments, the light source module 1 further includes a laser 101, an arbitrary waveform generator 102, and an intensity modulator 103, wherein: The output terminal of laser 101 is connected to the input terminal of intensity modulator 103; The first output channel of the arbitrary waveform generator 102 outputs an electrical pulse signal to the laser 101, causing the laser 101 to output a phase-randomized pulsed light signal; the second output channel of the arbitrary waveform generator 102 outputs a chopping signal to the intensity modulator 103, causing the intensity modulator 103 to compress the pulse width of the pulsed light signal and output the weakly coherent light pulse; the third output channel of the arbitrary waveform generator outputs a time synchronization signal.

[0057] Specifically, the first output channel of the Arbitrary Waveform Generator (AWG) 102 outputs an electrical pulse signal to the laser 101, internally modulating the injected current of the laser 101 to achieve phase randomization, thereby causing the laser 101 to output a phase-randomized pulsed optical signal. The pulsed optical signal can be a pulsed optical signal with a repetition frequency of 5 MHz and a pulse width of 5 ns.

[0058] Intensity modulator 103 (IM) receives the pulsed optical signal. The second output channel of arbitrary waveform generator 102 outputs a chopping signal to intensity modulator 103, causing intensity modulator 103 to compress the pulse width of the pulsed optical signal, for example, to 1~2 ns, thereby obtaining the weakly coherent optical pulse. Intensity modulator 103 outputs the weakly coherent optical pulse to optical path module 2. The weakly coherent optical pulse can be two weakly coherent optical pulses with the same spectrum and statistical characteristics approximating a single photon.

[0059] The second output channel of the arbitrary waveform generator 102 outputs a time synchronization signal to the detection module 3. The second output channel of the arbitrary waveform generator 102 can output a synchronization signal with a repetition frequency of 100K as a time synchronization signal.

[0060] This application employs two-stage modulation when generating weakly coherent optical pulses. The first-stage modulation uses internal modulation to generate coarse pulses and randomizes the phase, while the second-stage modulation achieves fine pulse width trimming. This decouples pulse generation from phase randomization and pulse width shaping, reducing the complexity of generating weakly coherent optical pulses and lowering the hardware requirements, thereby reducing implementation costs.

[0061] In one embodiment, the laser 101 is a distributed feedback (DFB) laser with a center wavelength of 1560 nm, which achieves stable output through temperature control and current drive.

[0062] Figure 4 This is a schematic diagram of the structure of an optical path module provided in an embodiment of the present invention, as shown below. Figure 4As shown, based on the above embodiments, the optical path module 2 further includes an optical fiber beam splitter 201, a first optical path adjustment unit 202, and a second optical path adjustment unit 203, wherein: The input end of the fiber optic beam splitter 201 is connected to the output end of the light source module 1, and is used to output a first optical signal to the first optical path adjustment unit 202 and output a second optical signal to the second optical path adjustment unit 203 based on the weak coherent optical pulse. The first optical path adjustment unit 202 is used to adjust the polarization state of the first optical signal, and the second optical path adjustment unit 203 is used to adjust the optical path of the second optical signal, so that the first optical path adjustment unit 202 and the second optical path adjustment unit output two weakly coherent optical pulses that satisfy the two-photon interference condition.

[0063] Specifically, the fiber optic beam splitter 201 outputs a first optical signal and a second optical signal based on the input weakly coherent optical pulses. The first optical path adjustment unit 202 adjusts the polarization state of the first optical signal, and the second optical path adjustment unit 203 adjusts the optical path length of the first optical signal, so that the two weakly coherent optical pulses output by the first and second optical path adjustment units satisfy the two-photon interference condition and can interfere within the detection module 3.

[0064] Figure 5 This is a schematic diagram of the optical path module provided in another embodiment of the present invention, as shown below. Figure 5 As shown, based on the above embodiments, the first optical path adjustment unit 202 further includes a first polarization controller 2021, a first collimator 2022, a first polarization beam splitter 2023 and a first plano-convex lens 2024, and the first optical signal passes through the first polarization controller 2021, the first collimator 2022, the first polarization beam splitter 2023 and the first plano-convex lens 2024 in sequence.

[0065] Specifically, the first optical signal passes through the first polarization controller 2021 for polarization state compensation and correction, outputting linearly polarized light. The first collimator 2022 collimates the linearly polarized light, outputting parallel light to the first polarization beam splitter 2023. The first polarization beam splitter 2023 purifies the polarization of the parallel light, outputting collimated parallel light with a single polarization state. The first plano-convex lens 2024 focuses the collimated parallel light with a single polarization state output by the first polarization beam splitter 2023 into a light spot of the target size. The target size is set according to actual needs, and this embodiment of the invention does not impose a limitation.

[0066] In one embodiment, the first collimator 2022 adopts a cage structure of an 11mm focal length aspherical lens.

[0067] In one embodiment, the focal length of the first plano-convex lens 2024 is 50 mm.

[0068] In one embodiment, the light spot has a waist radius of [missing information]. The light spot, Greater than 20um and less than 50um.

[0069] like Figure 5 As shown, the second optical path adjustment unit 203 includes an optical fiber 2031 of a preset length, an optical delay unit 2032, a second polarization controller 2033, a second collimator 2034, a displacement stage 2035, a second polarization beam splitter 2036, and a second plano-convex lens 2037. The second optical signal passes sequentially through the optical fiber 2031 of the preset length, the optical delay unit 2032, the second polarization controller 2033, the second collimator 2034, the second polarization beam splitter 2036, and the second plano-convex lens 2037. The second collimator 2034 is disposed on the displacement stage 2035.

[0070] Specifically, the second optical signal passes through an optical fiber 2031 of a preset length to increase the optical path, then through an optical delay unit 2032 for a preset delay, and is incident on the second polarization controller 2033 for polarization state compensation and correction, outputting linearly polarized light. The second collimator 2034 is used to collimate the linearly polarized light, outputting parallel light to the second polarization beam splitter 2036. The second polarization beam splitter 2036 purifies the polarization of the parallel light, outputting collimated parallel light with a single polarization state. The second plano-convex lens 2037 focuses the collimated parallel light with a single polarization state output by the second polarization beam splitter 2036 into a light spot of the target size. The displacement stage 2035 is used to adjust the positions of the second collimator 2034, the second polarization beam splitter 2036, and the second plano-convex lens 2037 to ensure that the translation of the second output in the spatial optical path does not affect the shape of the spatial light spot, so that the final output light spot interferes with the light spot output by the first optical path adjustment unit.

[0071] The preset length can be set according to actual needs, such as 1km, but this embodiment of the invention does not impose a limitation. The preset duration can also be set according to actual needs, such as a preset duration greater than 10ns and less than 20ns, but this embodiment of the invention does not impose a limitation.

[0072] Figure 6 This is a schematic diagram of the structure of a detection module provided in an embodiment of the present invention, as shown below. Figure 6 As shown, based on the above embodiments, the detection module 3 further includes a first beam splitter 301, a second beam splitter 302, a first optical fiber 303, a second optical fiber 304, a linear multi-channel fiber array 305, a first single-photon detector 306, a second single-photon detector 307, a third single-photon detector 308, and a time-to-digital converter 309, wherein: The input end of the first beam splitter 301 receives the interference input light. The first optical signal output from the first output end of the first beam splitter 301 is incident on the input end of the first optical fiber 303. The second optical signal output from the second output end of the first beam splitter 301 is incident on the input end of the second beam splitter 302. The output end of the first optical fiber 303 is connected to the input end of the first single-photon detector 306. The third optical signal output from the first output end of the second beam splitter 302 is incident on the input end of the second optical fiber 304. The fourth optical signal output from the second output end of the second beam splitter 302 is incident on the input end of the linear multi-channel fiber array 305. The output end of the second optical fiber 304 is connected to the input end of the second single-photon detector 307. The output end of the linear multi-channel fiber array 305 is connected to the input end of the third single-photon detector 308. The time-to-digital converter 309 is connected to the output terminals of the first single-photon detector 306, the second single-photon detector 307, the third single-photon detector 308, and the light source module, respectively. The time-to-digital converter 309 receives the time synchronization signal from the light source module 1. The first optical fiber 303 and the first single-photon detector 306 form a first detection channel, the second optical fiber 304 and the second single-photon detector 307 form a second detection channel, and the linear multi-channel fiber array 305 and the third single-photon detector 308 form a third detection channel.

[0073] Specifically, two coherent beams satisfying the two-photon interference condition interfere at the input of the first beam splitter 301, forming an interference input beam. The first beam splitter 301 splits the interference input beam into two output beams. The first optical signal output from the first output of the first beam splitter 301 is incident on the input of the first optical fiber 303. After passing through the first optical fiber 303, it is detected by the first single-photon detector 306. After detecting a photon, the first single-photon detector 306 outputs a first pulse signal to the time-to-digital converter 309. The time-to-digital converter 309 records the time when the first single-photon detector 306 detects the photon, which serves as the timestamp of the photon event corresponding to the first detection channel.

[0074] The second optical signal output from the second output terminal of the first beam splitter 301 is incident on the input terminal of the second beam splitter 302. The second beam splitter 302 splits the received second optical signal into two optical outputs. The third optical signal output from the first output terminal of the second beam splitter 302 is incident on the input terminal of the second optical fiber 304. After passing through the second optical fiber 304, it is detected by the second single-photon detector 307. After detecting a photon, the second single-photon detector 307 outputs a second pulse signal to the time-to-digital converter 309. The time-to-digital converter 309 records the time when the second single-photon detector 307 detects the photon as a timestamp of the photon event corresponding to the second detection channel.

[0075] The fourth optical signal output from the second output terminal of the second beam splitter 302 is incident on the input terminal of the linear multi-channel fiber array 305. After passing through the linear multi-channel fiber array 305, it is detected by the third single-photon detector 308. After detecting a photon, the third single-photon detector 308 outputs a third pulse signal to the time-to-digital converter 309. The time-to-digital converter 309 records the time when the third single-photon detector 308 detects the photon, which serves as the timestamp of the photon event corresponding to the third detection channel. The linear multi-channel fiber array 305 is used to collect photons from different lateral positions.

[0076] The time-to-digital converter 309 receives a time synchronization signal from the light source module 1 as a time reference, which ensures that the timestamps of photon events corresponding to each detection channel have a unified reference standard.

[0077] In this configuration, the optical transmission distance between the input end of the first optical fiber 303 and the interference position is d1, the optical transmission distance between the input end of the second optical fiber 304 and the interference position is d2, and the optical transmission distance between the input end of the linear multi-channel fiber array 305 and the interference position is d3, where d1, d2, and d3 are equal.

[0078] The first single-photon detector 306 and the second single-photon detector 307 can be superconducting nanowire single-photon detectors (SNSPDs). The third single-photon detector 308 can be a room-temperature semiconductor single-photon detector. The first beam splitter 301 and the second beam splitter 302 can be 50:50 beam splitters.

[0079] The first, second, and third detection channels perform photon detection in parallel, which improves photon detection efficiency compared to the non-time-multiplexed serial scanning in existing technologies.

[0080] Figure 7 This is a schematic diagram of the structure of a linear multi-channel fiber optic array provided in an embodiment of the present invention, as shown below. Figure 7 As shown, based on the above embodiments, the linear multi-channel fiber array 305 further includes a set number of single-mode fibers 3051 and fiber couplers 3052. The receiving ends of each single-mode fiber 3051 are arranged at a fixed spacing a in the fiber array probe 3053 to cover the size of the light spot generated at the input end of the linear multi-channel fiber array 305 by the fourth optical signal output from the second output end of the second beam splitter 302. The physical lengths of the set number of single-mode fibers 3051 are in an increasing arithmetic sequence. The output ends of the set number of single-mode fibers 3051 are connected to the input end of the fiber coupler 3052. The output end of the fiber coupler 3052 is connected to the input end of the third single-photon detector 308.

[0081] Specifically, the fourth optical signal output from the second output end of the second beam splitter 302 is used for far-field imaging at the input end of the linear multi-channel fiber array 305, whose input end is arranged laterally in the far-field plane. The linear multi-channel fiber array 305 includes a predetermined number of single-mode fibers 3051. The receiving ends of these fibers are arranged at a fixed spacing 'a' in the fiber array probe 3053. The physical lengths of the fibers form an increasing arithmetic sequence, and their lateral width is 'b', which completely covers the spot size of the fourth optical signal at the input end of the linear multi-channel fiber array 305, thus enabling the collection of photons from different lateral positions. The output end of the fiber coupler 3052 can be connected to the input end of the third single-photon detector 308 via an optical fiber.

[0082] Since the physical lengths of a set number of single-mode optical fibers 3051 form an increasing arithmetic sequence, photon event timestamps obtained from photons passing through different single-mode fibers are different. The difference between the photon event timestamp corresponding to each single-mode fiber and the reference time base is calculated as the detection delay time for each single-mode fiber. Since the detection delay times for each single-mode fiber are different, a correspondence between single-mode fibers and detection delay times can be obtained. As the spatial channel for photon transmission, the correspondence between single-mode fibers and detection delay times can serve as a correspondence between detection delay times and the spatial channel.

[0083] Since the cores of each single-mode fiber 3051 are arranged at a fixed spacing 'a' in the transverse direction, when the single-mode fiber corresponding to the photon event is determined, the transverse detection position difference can be determined based on the single-mode fiber corresponding to the photon event. The transverse detection position difference is equal to the difference between the transverse position of the single-mode fiber and the transverse position of the light spot center (i.e., the transverse coordinate difference). The transverse position of the light spot center can be used to mark the transverse position centers of n single-mode fibers. When i=i c hour, i c The corresponding experimentally calibrated central single-film fiber. Then, the difference between the lateral position of the i-th single-film fiber and the lateral position of the light spot center is:

[0084] Since each single-mode fiber corresponds to a different lateral coordinate difference, a correspondence between the single-mode fiber and the lateral position difference can be established. As a spatial channel for photon transmission, the correspondence between the single-mode fiber and the lateral position difference can be used as a correspondence between the spatial channel and the lateral position difference.

[0085] Each single-mode fiber 3051 has an independent optical path difference channel, which allows photons from different spatial locations to have different time delays during propagation, thereby completing the physical mapping of spatial information to temporal information.

[0086] In one embodiment, the fourth optical signal output from the second output end of the second beam splitter 302 performs far-field imaging at a propagation distance of 220 mm, and a linear multi-channel fiber array 305 is set in the corresponding far-field plane along the lateral direction. Since the 25 μm spot at the interference position expands to about 8 mm after propagation over 220 mm, the linear multi-channel fiber array 305 includes 64 single-mode fibers 3051. The cores of each single-mode fiber 3051 are arranged in the lateral direction at a fixed spacing of 127 μm and a width of 8.128 mm, which can completely cover the spot size, thus enabling the collection of photons from different lateral positions.

[0087] To encode spatial information into temporal information, the physical lengths of the 64 single-mode optical fibers 3051 are set as an increasing arithmetic sequence. The length of the first single-mode fiber is L1 = L0 = 0.5m, the length of the second single-mode fiber is L1 = L0 + ΔL, the length of the third single-mode fiber is L2 = L0 + 2ΔL, the length of the fourth single-mode fiber is L3 = L0 + 2ΔL, the length of the fifth single-mode fiber is L4 = L0 + 3ΔL, and so on, with the length of the nth single-mode fiber being Ln = L0 + nΔL. This results in an increasing time delay of 3ns for photons transmitted through the first to 64th single-mode fibers. The outputs of each single-mode fiber are combined and connected to the corresponding channel of the third single-photon detector 308. The 2ns pulse width and 3ns delay generated by the 64 single-mode fibers ensure that different channels of the same optical pulse do not interfere with each other. Furthermore, the time required for all 64 channels to receive the same optical pulse is 192ns. The optical pulse repetition frequency of 5MHz is equal to 200ns per optical pulse, which also avoids aliasing between different optical pulse periods.

[0088] This application designs a single-mode fiber array with an increasing physical length in an arithmetic sequence to map the spatial information of photons from different lateral positions into temporal information with a fixed delay difference. This enables photons that originally required spatial parallel detection to be collected in parallel in the time domain through optical path difference, avoiding the need for large-scale detection arrays and mechanical scanning, improving photon detection efficiency and reducing photon detection costs.

[0089] Based on the above embodiments, the displacement estimation model further includes:

[0090] in, This represents the probability of a two-photon interference event. This indicates the lateral detection position difference on the detection plane. Indicates the beam radius on the detection plane. Indicates displacement parameters, This represents an effective parameter that comprehensively characterizes the interference quality of a real system. , Indicates wavelength. This represents the wavefront curvature radius at the probe plane. , Indicates the transmission distance. Indicates Rayleigh length, , Indicates the waist radius, , , The standard deviation represents the transverse spatial distribution of photons on the beam waist surface; the two-photon interference event type is a beam-gathering event. The two-photon interference event type is an anti-beaming event. , [] represents the natural exponential function, and cosh[] represents the hyperbolic cosine function. The average photon number constant, , .

[0091] Specifically, the displacement estimation model described above can be solved based on Sequential Monte Carlo-Sampling Importance Resampling (SMC-SIR) to estimate the displacement parameters. The value of .

[0092] The principle of SMC-SIR is to use a set of weighted random samples to approximate the posterior probability distribution of the system state. As new observation data arrives, the random samples and their weights are recursively updated through three steps: "propagate", "update weight", and "resample", thereby approximating the true Bayesian posterior distribution.

[0093] In this application, given that the array-type single-photon detection system is already determined, the displacement parameters... The value of is fixed, based on the displacement parameter. The values ​​of are taken as random samples, and two-photon interference events are taken as observed events.

[0094] Can be set The range of values ​​for , The actual value is in Within the range of values. Sampling within the range of values indivual The value of, and The value cannot be repeated. Initialization indivual The weight corresponding to the value is 1 / Understandably, the larger the value of M, the larger the final displacement parameter obtained. The more precise the value of M, the better. The value of M is set based on practical experience, and this embodiment of the invention does not impose any limitations.

[0095] In obtaining the first After a two-photon interference event, the momentum-related parameters corresponding to the event are determined based on the detection results of the array-type single-photon detection system. And obtain the lateral detection position difference Record this event as:

[0096] The lateral displacement parameters to be estimated are: Its prior value range is a preset interval. Generate within this interval Each particle, that is Candidate displacement values:

[0097] And assign initial weights to each particle.

[0098] For the Two-photon interference events Each candidate displacement value Momentum-related parameters and the difference in detection position Substituting the candidate displacement value into the pre-established displacement estimation model, calculate the probability of the two-photon interference event occurring.

[0099] Subsequently, the weights of each particle are updated based on the likelihood probability of the event. Specifically, the particle weights from the previous two-photon interference event are updated. and the corresponding event probability Multiplying them together yields the unnormalized weights:

[0100] Then normalize the unnormalized weights of all particles:

[0101] Normalized weights Used to characterize the Candidate displacement values Before obtaining The posterior probability after a two-photon interference event.

[0102] After completing the first After updating the weights of the events, the estimated values ​​of the lateral displacement parameters can be calculated based on the current particle set. If posterior mean estimation is used, then the th event... The displacement estimation results after the next update are as follows:

[0103] Simultaneously, the posterior variance can be calculated to characterize the estimation uncertainty:

[0104] To avoid particle degeneration, the number of effective particles is calculated after each weight update:

[0105] When the number of effective particles Less than the preset threshold At this point, particles are resampled according to the current weight distribution, so that high-weight particles are retained or copied, and low-weight particles are discarded. After resampling, the value of M is updated according to the number of effective particles, and the particle weights are reset to:

[0106] To enhance particle diversity and prevent all particles from clustering around a few discrete values, a coarsening perturbation is added to the particle positions after resampling. :

[0107] in This is the coarsening parameter.

[0108] Repeat the above process to process them sequentially. Two-photon interference events. As the number of two-photon interference events increases, the particle weights gradually concentrate near the true displacement value, thereby achieving control over the lateral displacement parameter. The sequential Bayesian estimation. Finally, the posterior mean obtained from the last update can be:

[0109] As displacement parameter The estimated value; or the value corresponding to the largest weighted particle:

[0110] As the maximum a posteriori estimate.

[0111] In one embodiment, the array-type single-photon detection system has determined the displacement parameters to be estimated. The prior value range is a preset interval. For example, The range of values ​​can be set to Uniformly generated within this range One candidate sample value:

[0112] The interval between adjacent candidate sample values ​​is approximately:

[0113] The initial weight for each candidate sample value is set as follows:

[0114] When the array-type single-photon detection system obtains the first two-photon interference event, it determines the corresponding event. and and each candidate displacement value Substituting into the two-photon interference probability model, calculate the corresponding two-photon interference event probability:

[0115] Then, the probability of the two-photon interference event is multiplied by the current weight of the candidate sample value, and the product result corresponding to all candidate sample values ​​is normalized to update the weight of each candidate sample value.

[0116] When the system receives a second two-photon interference event, it re-determines the corresponding event. and The probability of a two-photon interference event corresponding to each candidate displacement value is calculated in the same way, and the weights of each candidate sample value are updated.

[0117] Similarly, as the system sequentially acquires multiple two-photon interference events, the weight distribution of the candidate sample values ​​will gradually concentrate near the true displacement value. After sequential updates of each two-photon interference event, the displacement parameters are obtained based on the final weight distribution. The estimated value.

[0118] If the posterior mean is used as the final estimate, then:

[0119] Figure 8 This is a flowchart illustrating a displacement measurement method based on single-photon detection according to an embodiment of the present invention, as shown below. Figure 8As shown, the displacement measurement method based on single-photon detection provided in this embodiment of the invention employs the array-type single-photon detection system described in any of the above embodiments, including: S801, the light source module outputs weak coherent light pulses and synchronization time signals; Specifically, the light source module attenuates the coherent light emitted by the laser to obtain a weakly coherent light pulse, then outputs the weakly coherent light pulse to the optical path module and outputs the synchronization time signal to the detection module. In this application, a weakly coherent light pulse is used instead of a single photon source.

[0120] S802, the optical path module generates two weakly coherent optical pulses that satisfy the two-photon interference condition based on the weakly coherent optical pulses, and the two weakly coherent optical pulses interfere and are detected in the detection module; Specifically, after receiving a weakly coherent optical pulse, the optical path module splits it into a first optical signal and a second optical signal. Then, it adjusts the polarization state of the first optical signal and the optical path length of the second optical signal, outputting two weakly coherent optical pulses that satisfy the two-photon interference condition. These two weakly coherent optical pulses will interfere within the detection module and be detected.

[0121] S803, the detection module performs photon detection on each path of light generated based on the interference input light in parallel through multiple detection channels to obtain the electrical signal corresponding to each detection channel, and obtains the photon event timestamp corresponding to each detection channel based on the electrical signal and time synchronization signal corresponding to each detection channel; Specifically, two weakly coherent optical pulses interfere within the detection module, producing interference input light. The detection module then splits this interference input light into multiple paths, each input to a detection channel for photon detection. These detection channels operate in parallel to improve detection efficiency. After each detection channel detects a photon event, a corresponding photon event timestamp is obtained. A time synchronization signal ensures that the timestamps for photon events across all detection channels have a unified reference standard.

[0122] S804, the displacement calculation module determines the two-photon interference event type based on the photon event timestamps corresponding to each detection channel, and obtains the displacement value according to the two-photon interference event type, the lateral detection position difference, and the displacement estimation model; wherein, the lateral detection position difference is obtained based on the photon event timestamps corresponding to the detection channels used to detect photons from different lateral positions in each detection channel.

[0123] Specifically, the displacement calculation module determines the two-photon interference event type based on the photon event timestamps corresponding to each detection channel. Each detection channel includes a third detection channel for detecting photons from different lateral positions. Based on the photon event timestamps corresponding to the third detection channel, the lateral detection position difference corresponding to the photons detected by the third detection channel can be determined. The displacement calculation module 4 calculates the displacement value based on the two-photon interference event type, the lateral detection position difference, and the displacement estimation model.

[0124] This invention provides a displacement measurement method based on single-photon detection. A light source module outputs a weakly coherent light pulse and a time synchronization signal. An optical path module generates two weakly coherent light pulses that satisfy the two-photon interference condition based on the weakly coherent light pulses. These two weakly coherent light pulses interfere and are detected within a detection module. The detection module performs parallel photon detection on each light source generated based on the interference input light through multiple detection channels to obtain the electrical signal corresponding to each detection channel. It then obtains the photon event timestamp corresponding to each detection channel based on the electrical signal and the time synchronization signal. A displacement calculation module determines the two-photon interference event type based on the photon event timestamps corresponding to each detection channel and obtains the displacement value based on the two-photon interference event type, the lateral detection position difference, and a displacement estimation model. The lateral detection position difference is obtained based on the photon event timestamps corresponding to the detection channels used to detect photons from different lateral positions, thus improving displacement measurement efficiency and reducing displacement measurement costs.

[0125] Based on the above embodiments, each detection channel further includes a first detection channel, a second detection channel, and a third detection channel; correspondingly, determining the two-photon interference event type based on the photon event timestamps corresponding to each detection channel includes: If the photon event timestamp corresponding to the first detection channel matches the photon event timestamp corresponding to the third detection channel, then the two-photon interference event type is determined to be a beam-gathering event; If the photon event timestamp corresponding to the second detection channel matches the photon event timestamp corresponding to the third detection channel, then the two-photon interference event type is determined to be an anti-beaming event.

[0126] Specifically, after the first detection channel detects a photon, a timestamp of the photon event corresponding to the first detection channel can be obtained. After the third detection channel detects a photon, a timestamp of the photon event corresponding to the third detection channel can be obtained. If the timestamps of the photon events corresponding to the first and third detection channels are within a preset time window, then the timestamps of the photon events corresponding to the first and third detection channels match, and the two-photon interference event type can be determined to be a beam-gathering event. The preset time window is set based on practical experience, for example, 1.5 ns; this embodiment of the invention does not impose a limitation.

[0127] After the second detection channel detects a photon, the photon event timestamp corresponding to the second detection channel can be obtained. After the third detection channel detects a photon, the photon event timestamp corresponding to the third detection channel can be obtained. If the photon event timestamps corresponding to the second and third detection channels are within a preset time window, then the photon event timestamps corresponding to the second and third detection channels match, and the two-photon interference event type can be determined to be an anti-snagging event.

[0128] Figure 9 This is a flowchart illustrating a displacement measurement method based on single-photon detection according to an embodiment of the present invention, as shown below. Figure 9 As shown, based on the above embodiments, further, the photon event timestamps corresponding to the detection channels used to detect photons from different lateral positions in each detection channel are used to obtain the following: S901. Obtain the detection delay time based on the photon event timestamps corresponding to the detection channels used to detect photons from different lateral positions and the reference time base; Specifically, a third detection channel is used to detect photons from different lateral positions. The displacement calculation module calculates the difference between the photon event timestamp corresponding to the third detection channel and the reference time base to obtain the detection delay time. The reference time base is obtained through a time synchronization signal.

[0129] S902. Based on the detection delay time and the correspondence between the detection delay time and the spatial channel, obtain the spatial channel corresponding to the detection delay time; wherein, the correspondence between the detection delay time and the spatial channel is pre-established; Specifically, the displacement calculation module queries the correspondence between the detection delay time and the spatial channel based on the detection delay time, and can obtain the spatial channel corresponding to the detection delay time.

[0130] S903. Based on the spatial channel corresponding to the detection delay time and the correspondence between the spatial channel and the lateral position difference, the lateral detection position difference is obtained; wherein, the detection channel used to detect photons from different lateral positions includes multiple spatial channels; the correspondence between the spatial channel and the lateral position difference is established in advance.

[0131] Specifically, the displacement calculation module queries the correspondence between the spatial channel and the lateral position difference based on the spatial channel corresponding to the detection delay time, thereby obtaining the lateral detection position difference corresponding to the spatial channel for the detection delay time. The detection channel used to detect photons from different lateral positions includes multiple spatial channels, each spatial channel detects photons from different lateral positions, and the lateral detection position difference corresponding to each spatial channel is different.

[0132] The array-type single-photon detection system and method provided in this invention have the following beneficial effects: (1) This invention introduces optical path delays that differentiate between different spatial channels at the optical level using a linear multi-channel fiber array. This allows photons from multiple spatial locations to be encoded in parallel into events with different arrival times within the same measurement period, and then uniformly read by a single-point single-photon detector. This structural design avoids the limitations of traditional schemes that rely on mechanical scanning or multi-pixel detection arrays to acquire spatial distribution information. Without significantly increasing the system hardware scale and cost, it can achieve equivalent parallel acquisition of information from multiple spatial channels, significantly improving data acquisition efficiency and providing the possibility for real-time measurement of high-dimensional space or momentum information.

[0133] (2) Effectively improve the accuracy of spatial or displacement measurement and make full use of the information resources contained in quantum interference.

[0134] This invention does not infer displacement parameters by directly imaging the real-space position of photons. Instead, it utilizes the statistical distribution characteristics formed by two-photon interference in the conjugate variable domain for parameter estimation. Through statistical analysis of momentum-space related events and combined with the optimal parameter estimation algorithm, more effective information can be extracted from the measurement data than from traditional intensity-based measurements.

[0135] This measurement method can significantly reduce the uncertainty of displacement estimation under given photon resource conditions, enabling the measurement accuracy to approach the theoretical limit allowed by quantum statistical laws in practical applications, thereby breaking through the inherent limitations of traditional imaging and measurement methods in terms of resolution and sensitivity.

[0136] (3) Significantly reduces the dependence on photon spatial overlap and optical path precision alignment, improving system robustness.

[0137] Existing HOM interferometry-based measurement schemes typically require photons participating in the interference to be highly coincident in the spatial mode field. This condition is difficult to maintain stably in practical applications, especially in the presence of unknown displacement, mechanical disturbance, or environmental drift, which can easily lead to a decrease in interference visibility and affect the measurement results.

[0138] This invention avoids dependence on strict spatial overlap of photon wave packets by resolving and statistically analyzing photon transverse momentum information. Even under conditions of partial separation or imperfections in the photon spatial mode field, the system can still extract effective interference features from momentum-space related information, thereby maintaining stable measurement performance.

[0139] This feature significantly reduces the system's requirements for precise optical path adjustment and long-term stability, and improves its tolerance to environmental disturbances such as mechanical vibration and thermal drift, which is beneficial for the system's deployment in complex experimental environments and even industrial application scenarios.

[0140] (4) Improve system flexibility and application adaptability to promote the practical application of quantum measurement technology.

[0141] Because the detection architecture of this invention does not rely on high-density detector arrays or complex mechanical scanning structures, its system size, complexity, and maintenance costs are significantly lower than existing solutions. Furthermore, this solution has good compatibility with different light source types, and can be used with single-photon sources or weakly coherent light sources, providing greater flexibility for system design in various application scenarios.

[0142] The aforementioned characteristics make the technical solution proposed in this invention not only applicable to high-precision quantum measurement research under laboratory conditions, but also lay the technical foundation for its promotion in application fields that are sensitive to stability and cost, such as biomedical imaging and semiconductor precision detection.

[0143] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0144] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0145] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0146] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0147] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0148] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A linear multi-channel fiber optic array, characterized in that, Includes fiber arrays and fiber combiners, wherein: The receiving end of the fiber array is disposed in the fiber array probe, and the output end of the fiber array is connected to the input end of the fiber combiner; the fiber array includes a set number of fiber channels, the physical lengths of the set number of fiber channels are in an increasing arithmetic sequence, and the receiving ends of the set number of fiber channels are arranged sequentially at a fixed interval.

2. The linear multi-channel fiber array according to claim 1, characterized in that, The effective coverage width of the linear multi-channel fiber array is W=(N-1)p, where W represents the effective coverage width, N represents the set number, and p represents the center distance between adjacent fiber channels.

3. The linear multi-channel fiber array according to claim 1, characterized in that, The set quantity satisfies the following constraints: Where N represents the set quantity. This indicates the repetition frequency of the laser pulse. This indicates that a safety margin has been reserved. This indicates the time delay between adjacent fiber optic channels. , Represents the group refractive index of the optical fiber. Represents the speed of light. This represents the length difference between adjacent fiber optic channels. , This indicates the pulse width of a single laser pulse.

4. An array-type single-photon detection system, characterized in that, It includes a light source module, an optical path module, a detection module, and a displacement calculation module, wherein the detection module includes the linear multi-channel fiber array according to any one of claims 1 to 3, wherein: The light source module is used to output weak coherent light pulses and time synchronization signals; The optical path module is used to generate two weakly coherent optical pulses that satisfy the two-photon interference condition based on the weakly coherent optical pulses. The detection module is used to perform photon detection on each light source generated based on the interference input light in parallel through multiple detection channels to obtain the electrical signal corresponding to each detection channel, and to obtain the photon event timestamp corresponding to each detection channel based on the electrical signal and time synchronization signal corresponding to each detection channel; wherein, the interference input light is generated after the two weakly coherent light pulses interfere; one of the detection channels includes a linear multi-channel fiber array; The displacement calculation module is used to determine the two-photon interference event type based on the photon event timestamps corresponding to each detection channel, and to obtain the displacement value according to the two-photon interference event type, the lateral detection position difference, and the displacement estimation model; wherein, the lateral detection position difference is obtained based on the photon event timestamps corresponding to the detection channels including linear multi-channel fiber arrays in each detection channel; the displacement estimation model is preset.

5. The array-type single-photon detection system according to claim 4, characterized in that, The light source module includes a laser, an arbitrary waveform generator, and an intensity modulator, wherein: The output terminal of the laser is connected to the input terminal of the intensity modulator; The first output channel of the arbitrary waveform generator outputs an electrical pulse signal to the laser, causing the laser to output a phase-randomized pulsed light signal; the second output channel of the arbitrary waveform generator outputs a chopping signal to the intensity modulator, causing the intensity modulator to compress the pulse width of the pulsed light signal and output the weakly coherent light pulse; the third output channel of the arbitrary waveform generator outputs a time synchronization signal.

6. The array-type single-photon detection system according to claim 4, characterized in that, The optical path module includes an optical fiber beam splitter, a first optical path adjustment unit, and a second optical path adjustment unit, wherein: The input end of the fiber optic beam splitter is connected to the output end of the light source module, and is used to output a first optical signal to the first optical path adjustment unit and output a second optical signal to the second optical path adjustment unit based on the weak coherent optical pulse. The first optical path adjustment unit is used to adjust the polarization state of the first optical signal, and the second optical path adjustment unit is used to adjust the optical path of the second optical signal, so that the first optical path adjustment unit and the second optical path adjustment unit output two weakly coherent optical pulses that satisfy the two-photon interference condition.

7. The array-type single-photon detection system according to claim 6, characterized in that, The first optical path adjustment unit includes a first polarization controller, a first collimator, a first polarization beam splitter, and a first plano-convex lens. The propagation optical path of the first optical signal passes through the first polarization controller, the first collimator, the first polarization beam splitter, and the first plano-convex lens in sequence.

8. The array-type single-photon detection system according to claim 6, characterized in that, The second optical path adjustment unit includes an optical fiber of a preset length, an optical delay unit, a second polarization controller, a second collimator, a displacement stage, a second polarization beam splitter, and a second plano-convex lens. The propagation optical path of the second optical signal passes sequentially through the optical fiber of the preset length, the optical delay unit, the second polarization controller, the second collimator, the second polarization beam splitter, and the second plano-convex lens. The second collimator is disposed on the displacement stage.

9. The array-type single-photon detection system according to claim 4, characterized in that, The detection module includes a first beam splitter, a second beam splitter, a first optical fiber, a second optical fiber, a linear multi-channel fiber array, a first single-photon detector, a second single-photon detector, a third single-photon detector, and a time-to-digital converter, wherein: The input of the first beam splitter receives two weakly coherent optical pulses. The first optical signal output from the first output of the first beam splitter is incident on the input of the first optical fiber. The second optical signal output from the second output of the first beam splitter is incident on the input of the second beam splitter. The output of the first optical fiber is connected to the input of the first single-photon detector. The third optical signal output from the first output of the second beam splitter is incident on the input of the second optical fiber. The fourth optical signal output from the second output of the second beam splitter is incident on the input of the linear multi-channel fiber array. The output of the second optical fiber is connected to the input of the second single-photon detector. The output of the linear multi-channel fiber array is connected to the input of the third single-photon detector. The time-to-digital converter is connected to the output terminals of the first single-photon detector, the second single-photon detector, the third single-photon detector, and the light source module, respectively. The time-to-digital converter receives the time synchronization signal from the light source module. The first optical fiber and the first single-photon detector constitute a first detection channel, the second optical fiber and the second single-photon detector constitute a second detection channel, and the linear multi-channel fiber array and the third single-photon detector constitute a third detection channel. The third detection channel is used to detect photons from different lateral positions.

10. The array-type single-photon detection system according to any one of claims 4 to 7, characterized in that, The displacement estimation model includes: in, This represents the probability of a two-photon interference event. This indicates the lateral detection position difference on the detection plane. Indicates the beam radius on the detection plane. Indicates displacement parameters, This represents an effective parameter that comprehensively characterizes the interference quality of a real system. , Indicates wavelength. This represents the wavefront curvature radius at the probe plane. , Indicates the transmission distance. Indicates Rayleigh length, , Indicates the waist radius, , , The standard deviation represents the transverse spatial distribution of photons on the beam waist surface; the two-photon interference event type is a beam-gathering event. The two-photon interference event type is an anti-beaming event. , [] denotes the natural exponential function, and cosh[] denotes the hyperbolic cosine function. The average photon number constant, , .

11. A displacement measurement method, characterized in that, The array-type single-photon detection system according to any one of claims 4 to 10 includes: The light source module outputs weakly coherent light pulses and a time synchronization signal; The optical path module generates two weakly coherent optical pulses that satisfy the two-photon interference condition based on the weakly coherent optical pulses. The two weakly coherent optical pulses interfere with each other in the detection module and are then detected. The detection module performs photon detection on each path of light generated based on the interference input light in parallel through multiple detection channels to obtain the electrical signal corresponding to each detection channel, and obtains the photon event timestamp corresponding to each detection channel based on the electrical signal and time synchronization signal corresponding to each detection channel. The displacement calculation module is used to determine the two-photon interference event type based on the photon event timestamps corresponding to each detection channel, and to obtain the displacement value according to the two-photon interference event type, the lateral detection position difference, and the displacement estimation model; wherein, the lateral detection position difference is obtained based on the photon event timestamps corresponding to the detection channels used to detect photons from different lateral positions in each detection channel.

12. The displacement measurement method according to claim 11, characterized in that, Each detection channel includes a first detection channel, a second detection channel, and a third detection channel; correspondingly, determining the two-photon interference event type based on the photon event timestamps corresponding to each detection channel includes: If the photon event timestamp corresponding to the first detection channel matches the photon event timestamp corresponding to the third detection channel, then the two-photon interference event type is determined to be a beam-gathering event; If the photon event timestamp corresponding to the second detection channel matches the photon event timestamp corresponding to the third detection channel, then the two-photon interference event type is determined to be an anti-beaming event.

13. The displacement measurement method according to claim 11, characterized in that, Based on the photon event timestamps corresponding to the detection channels used to detect photons from different lateral positions in each detection channel, the following are obtained: The detection delay time is obtained based on the photon event timestamps corresponding to the detection channels used to detect photons from different lateral positions and the reference time base. Based on the detection delay time and the correspondence between the detection delay time and the spatial channel, the spatial channel corresponding to the detection delay time is obtained; wherein, the correspondence between the detection delay time and the spatial channel is pre-established; The lateral detection position difference is obtained based on the spatial channel corresponding to the detection delay time and the correspondence between the spatial channel and the lateral position difference; wherein, the detection channel for detecting photons from different lateral positions includes multiple spatial channels; the correspondence between the spatial channel and the lateral position difference is established in advance.

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