A key parameter testing system for a fiber type single photon avalanche diode and a method of using the same

Abstract

This application provides a key parameter testing system and method for fiber-optic single-photon avalanche diodes (SPADs). The system uses a testing module to drive multiple SPADs under test, generates laser trigger signals based on parameter testing requests, and acquires pulse parameters for each SPAD under test under different testing modes with and without light source illumination. A laser generation module generates an initial pulse signal based on the laser trigger signal; a laser adjustment and transmission module adjusts the light attenuation value of the initial pulse laser and separates it into multiple test light sources with equal laser power; a control module monitors the laser power of the laser generation module and configures the laser adjustment parameters of the laser adjustment and transmission module; and the system determines the key parameters of each SPAD under test based on the pulse parameters. The system provided in this application can quickly detect the key parameters of multiple SPADs while ensuring detection accuracy, and the parameter testing process is simple and intuitive.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, specifically to a key parameter testing system for fiber optic single-photon avalanche diodes and its usage method. Background Technology

[0002] Single-photon detectors possess ultrafast response speeds, ultra-low time jitter, ultra-high sensitivity, and ultra-low noise, enabling precise time-of-flight measurements and the detection of energies as low as a single photon. Therefore, they are widely used in many emerging applications requiring precise time-of-arrival in laser ranging and where achievable signal strengths are only a few photon energy levels.

[0003] Currently, the most widely used and technologically mature semiconductor single-photon detectors include silicon single-photon avalanche diodes (Si-SPAD), indium gallium arsenide single-photon avalanche diodes (InGaAs-SPAD), and semiconductor quantum dot detectors (QDOGFET). Depending on the application requirements, parameters such as dark count rate, single-photon detection efficiency, afterpulse probability, dead time, and timing jitter become key performance indicators for single-photon detectors. Silicon single-photon avalanche diodes (Si-SPAD) offer advantages such as low dark count rate, low afterpulse probability, low timing jitter, and short dead time, making them particularly suitable for single-photon detection applications where the photon arrival time at the detector is unknown and operation in free-running mode is required.

[0004] In related technologies, because the key parameters of single-photon detectors are greatly affected by temperature, temperature control circuits are required during testing, resulting in complex system designs and high power consumption. For single-photon detectors without temperature control elements, direct temperature control is not possible. When testing key parameters, improving the test resolution of time jitter requires compressing the analysis time window to reduce data transmission pressure and time; however, compressing the analysis time window cannot meet the testing requirements of parameters such as dark count rate, single-photon detection efficiency, and afterpulse probability, which require longer statistical durations.

[0005] Therefore, how to provide a key parameter testing system that can improve the efficiency of parameter testing while ensuring the accuracy of parameter testing is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the present invention provides a technical solution for a key parameter testing system for fiber optic single-photon avalanche diodes, so as to solve at least one of the above-mentioned technical problems.

[0007] To achieve the above-mentioned objectives and other related objectives, the technical solution provided in this application is as follows.

[0008] According to a first aspect of the embodiments of this application, a key parameter testing system for an optical fiber-type single-photon avalanche diode is provided, comprising:

[0009] The test module provides reset signals for resetting multiple single-photon avalanche diodes under test, generates laser trigger signals according to parameter test requests, and acquires multiple pulse parameters of each single-photon avalanche diode under test under different test modes when the test light source is irradiated and when the test light source is not irradiated.

[0010] The laser generation module is connected to the test module and generates an initial pulse laser according to the laser trigger signal and transmits the laser.

[0011] A laser adjustment and transmission module, connected to the laser generation module, separates the initial pulse laser into multiple test light sources and adjusts the light attenuation value during the transmission process of the initial pulse laser to make the laser power of the multiple test light sources equal.

[0012] The control module is connected to the test module, the laser generation module and the laser modulation and transmission module. It monitors the laser power of the laser generation module and configures the laser modulation parameters of the laser modulation and transmission module, as well as the key parameters of the single-photon avalanche diode under test according to the multiple pulse parameters.

[0013] The laser modulation and transmission module is in a light-shielding environment, and the test module and multiple single-photon avalanche diodes under test are in a light-shielding environment with a preset temperature. The different test modes include normal mode, optical coincidence gate mode, and delayed coincidence gate mode. The key parameters include single-photon detection efficiency, afterpulse probability, dark count rate, and dead time.

[0014] In one embodiment of this application, the test module includes: a signal generation unit for providing the reset signal and the laser trigger signal; a delay control unit for generating different coincidence gate signals according to different test modes; a counting unit for acquiring multiple pulse parameters of each of the single-photon avalanche diodes under test receiving and not receiving irradiation from the test light source based on multiple coincidence gate signals; and a data transmission unit for transmitting the multiple pulse parameters.

[0015] In one embodiment of this application, the laser generation module includes: a laser generation unit for generating the initial pulse laser according to the laser trigger signal; a first optical splitting unit for splitting the initial pulse laser into two optical paths to obtain two first pulse lasers; and an optical monitoring unit connected to the first output terminal of the first optical splitting unit for detecting the laser power of the first pulse laser.

[0016] In one embodiment of this application, the laser modulation and transmission module includes: a first adjustable optical attenuation unit connected to the second output terminal of the first optical splitter unit, used to adjust the optical attenuation value of the first pulsed laser; a second optical splitter unit connected to the first adjustable optical attenuation unit, used to split the second pulsed laser adjusted by the first adjustable optical attenuation unit into multiple paths to obtain multiple third pulsed lasers; multiple second adjustable optical attenuation units connected one-to-one with the multiple output terminals of the second optical splitter unit, used to adjust the optical attenuation value of the third pulsed lasers; and multiple fiber optic flanges, each fiber optic flange having its input terminal connected one-to-one with a corresponding second adjustable optical attenuation unit, and each fiber optic flange having its output terminal connected one-to-one with multiple single-photon avalanche diodes under test via optical fibers; wherein the second optical splitter unit, the multiple second adjustable optical attenuation units, and the multiple fiber optic flanges are disposed on the same substrate.

[0017] In one embodiment of this application, the system further includes: a timing module connected to the laser generation module and the test module, which determines a single event timing based on the generation time of the initial pulse laser and the response time of a certain single-photon avalanche diode under test receiving the corresponding test light source, so as to determine the time jitter parameter of the single-photon avalanche diode under test based on multiple single event timings; and a power supply module connected to the control module and the test module, which supplies power to the test module according to the power supply configuration signal set by the control module.

[0018] According to a second aspect of the embodiments of this application, a method for using the key parameter testing system for a fiber-optic single-photon avalanche diode as described above is provided, comprising:

[0019] Get parameter test request;

[0020] An initial pulse laser is generated according to the parameter test request. The optical attenuation value of the initial pulse laser is adjusted and the optical path is separated to obtain multiple test light sources with equal laser power.

[0021] The key parameters of each single-photon avalanche diode under test are determined based on multiple pulse parameters of each single-photon avalanche diode under test when illuminated by the test light source and when not illuminated by the test light source under different test modes.

[0022] In one embodiment of this application, before obtaining the parameter test request, the method further includes: adjusting the optical attenuation value of each transmission path during the optical path separation process so that the laser power received by each of the single-photon avalanche diodes under test is equal; and determining the pre-adjusted optical attenuation value based on the laser power of the first pulse laser of the initial pulse laser optical path separation and the preset optical power threshold of the single-photon avalanche diode under test.

[0023] In one embodiment of this application, adjusting the optical attenuation value of each transmission path during optical path separation includes: fixing the output power of the initial pulse laser and the optical attenuation value of the initial pulse laser; and adjusting the optical attenuation value of each transmission path to make the optical attenuation values ​​of each transmission path equal.

[0024] In one embodiment of this application, determining a pre-adjusted optical attenuation value based on the laser power of the initial pulsed laser and a preset optical power threshold of the single-photon avalanche diode under test includes setting the optical attenuation value corresponding to the first pulsed laser as a preset attenuation threshold; determining laser transmission loss based on the output power of the first pulsed laser and the laser power of a certain test light source; adjusting the output power of the first pulsed laser to the laser test power; and determining the pre-adjusted optical attenuation value based on the laser test power, the optical transmission loss, and the target laser power of the test light source.

[0025] In one embodiment of this application, key parameters of each single-photon avalanche diode under test are determined based on multiple pulse parameters of each single-photon avalanche diode under test when the test light source is illuminating and when the test light source is not illuminating under different test modes. This includes: obtaining pulse parameters of each single-photon avalanche diode under test when receiving the test light source and when not receiving the test light source under different test modes; and determining the key parameters based on the multiple pulse parameters, the frequency of the initial pulse laser, and the average number of photons per pulse received from the test light source.

[0026] This application provides a key parameter testing system for fiber-optic single-photon avalanche diodes (SPADs) and its usage method. The system uses a testing module to drive the operation of multiple SPADs under test, generates a laser trigger signal based on parameter testing requests, and acquires multiple pulse parameters for each SPAD under test under different testing modes with and without light source illumination. A laser generation module generates an initial pulse signal based on the laser trigger signal; a laser adjustment and transmission module adjusts the optical attenuation value of the initial pulse laser and separates the initial pulse laser into multiple test light sources with equal laser power; a control module monitors the laser power of the laser generation module and configures the laser adjustment parameters of the laser adjustment and transmission module, and determines the key parameters of each SPAD under test based on the multiple pulse parameters. The testing system provided in this application offers high testing accuracy and can simultaneously detect the key parameters of multiple SPADs. The overall system design is not complex, and the parameter testing implementation process is simple and intuitive, providing valuable reference for guiding the design of production testing systems for fiber-optic SPADs.

[0027] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0029] Figure 1 This is a block diagram illustrating a key parameter testing system for an optical fiber single-photon avalanche diode, as shown in an exemplary embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram illustrating a test module according to an exemplary embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of a key parameter testing system for an optical fiber single-photon avalanche diode, as illustrated in an exemplary embodiment of the present invention.

[0032] Figure 4 This is a schematic diagram of a time jitter test shown in an exemplary embodiment of the present invention;

[0033] Figure 5 This is a flowchart illustrating the usage method of a key parameter testing system for an optical fiber single-photon avalanche diode, as shown in an exemplary embodiment of the present invention.

[0034] Figure 6 This is a schematic diagram illustrating the counting statistics of an optical fiber type single-photon avalanche diode under illumination conditions, as shown in an exemplary embodiment of the present invention.

[0035] Figure 7 This is a schematic diagram illustrating the counting statistics of an optical fiber type single-photon avalanche diode under no-light conditions, as shown in an exemplary embodiment of the present invention. Detailed Implementation

[0036] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0037] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0038] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0039] An FPGA (Field-Programmable Gate Array) is a semi-custom circuit whose internal logic and connections can be defined by the user through programming.

[0040] GPIB (General-Purpose Interface Bus) is a digital 24-pin parallel bus consisting of 16 signal lines and 8 ground lines. It is mainly used to connect test instruments and computers to achieve automated testing.

[0041] USB (Universal Serial Bus) is a fast and flexible serial bus interface used to connect various external devices to a computer.

[0042] A network port is the physical connection between a network interface card (NIC) and a network cable, and is typically used to enable network connections between computers and between a computer and network devices.

[0043] Camera Link is a digital image transmission standard designed specifically for industrial cameras.

[0044] Single-photon detectors possess ultrafast response speeds, ultra-low time jitter, ultra-high sensitivity, and ultra-low noise, enabling precise time-of-flight measurements and the detection of energies as low as a single photon. Therefore, they are widely used in many emerging applications requiring precise time-of-arrival in laser ranging and where achievable signal strengths are only a few photon energy levels.

[0045] Currently, the most widely used and technologically mature semiconductor single-photon detectors include silicon single-photon avalanche diodes (Si-SPAD), indium gallium arsenide single-photon avalanche diodes (InGaAs-SPAD), and semiconductor quantum dot detectors (QDOGFET). Depending on the application requirements, parameters such as dark count rate, single-photon detection efficiency, afterpulse probability, dead time, and timing jitter become key performance indicators for single-photon detectors. Silicon single-photon avalanche diodes (Si-SPAD) offer advantages such as low dark count rate, low afterpulse probability, low timing jitter, and short dead time, making them particularly suitable for single-photon detection applications where the photon arrival time at the detector is unknown and operation in free-running mode is required.

[0046] Since single-photon detectors are temperature-sensitive devices, changes in ambient temperature will affect the test parameters when the operating voltage is constant. During testing, each single-photon detector is equipped with a temperature control circuit, which not only makes the system design complex but also results in high overall power consumption. For some single-photon detectors that do not have temperature measurement and control elements, temperature control cannot be achieved through temperature control circuits.

[0047] To improve the test resolution of time jitter for key parameters, it is necessary to compress the analysis time window to reduce data transmission pressure and transmission time. However, the compressed analysis time window cannot meet the testing requirements of parameters such as dark count rate, single photon detection efficiency, and afterpulse probability, which require a longer statistical duration.

[0048] Secondly, silicon has a response wavelength range of 400nm to 1100nm and is relatively sensitive to visible light. Therefore, avoiding interference from external ambient light is also extremely important during the construction of the test system.

[0049] To solve the above problems, such as Figure 1 As shown, this application provides a key parameter testing system for fiber optic single-photon avalanche diodes, comprising:

[0050] The test module provides reset signals for multiple single-photon avalanche diodes under test to perform reset operations, generates a laser trigger signal P1 according to the parameter test request, and acquires multiple pulse parameters of each single-photon avalanche diode under test under different test modes when the test light source is irradiated and when the test light source is not irradiated.

[0051] The laser generation module is connected to the test module. It generates an initial pulse laser based on the laser trigger signal P1 and transmits the signal laser.

[0052] The laser adjustment and transmission module, connected to the laser generation module, separates the initial pulse laser into multiple test light sources and adjusts the light attenuation value during the transmission of the initial pulse laser to ensure that the laser power of the multiple test light sources is equal.

[0053] The control module connects to the test module, laser generation module, and laser modulation and transmission module. It monitors the laser power of the laser generation module, configures the laser modulation parameters of the laser modulation and transmission module, and determines the key parameters of each single-photon avalanche diode under test based on multiple pulse parameters.

[0054] The laser modulation and transmission module is in a light-shielded environment, and the test module and multiple single-photon avalanche diodes under test are in a light-shielded environment with a preset temperature. Different test modes include normal mode, optical coincidence gate mode, and delayed coincidence gate mode. Key parameters include single-photon detection efficiency, afterpulse probability, dark count rate, and dead time.

[0055] It should be noted that, as Figure 1 As shown, the laser modulation transmission module, the test module, and multiple single-photon avalanche diodes under test are in a strictly light-shielded environment. The test module and multiple single-photon avalanche diodes under test are also in a temperature-controlled environment. Among the multiple single-photon avalanche diodes under test, one diode is a calibration single-photon avalanche diode, which is always present during each test to detect whether the system is abnormal.

[0056] In detail, the test module includes: a signal generation unit for providing reset and laser trigger signals; a delay control unit for generating different coincidence gate signals according to different test modes; a counting unit for acquiring multiple pulse parameters of each single-photon avalanche diode under test under test with and without test light source illumination, based on multiple coincidence gate signals; and a data transmission unit for transmitting multiple pulse parameters. Specifically, such as... Figure 2 As shown, the test module is based on an FPGA, and the functions of the test circuit are as follows: The signal generation unit outputs a laser trigger signal P1 according to the parameter test request and sends it to the laser generation module, causing the laser generation module to generate an initial pulse laser. It also provides the quenching / recovery signal required for the calibration of the single-photon avalanche diode and the single-photon avalanche diode under test, i.e., it provides a reset signal for the single-photon avalanche diode to perform a reset operation. The delay control unit generates corresponding coincidence gate signals according to the normal mode, optical coincidence gate mode, and delayed coincidence gate module. The counting unit collects avalanche signals generated by the single-photon avalanche diode under test light illumination and non-illumination based on multiple coincidence gate signals. Each avalanche generates a counting pulse, which is processed by the counting unit to obtain pulse parameters. The counting unit in the FPGA controls the addition of coincidence gates to the generated counting pulses through the delay control unit based on the delay signal, realizing counting statistics under different test modes. Multiple pulse parameters are then uploaded to the control module by the data transmission unit and data interface.

[0057] Specifically, the laser generation module includes: a laser generation unit that generates an initial pulse laser based on a laser trigger signal; a first optical splitting unit that performs a one-to-two optical splitting process on the initial pulse laser to obtain two first pulse lasers; and an optical monitoring unit connected to the first output terminal of the first optical splitting unit to detect the laser power of the first pulse laser. Specifically, as shown... Figure 3 As shown, the laser generating unit generates an initial pulse laser according to the laser trigger signal P1. The laser generating unit can be a picosecond pulse laser. The laser generating unit is connected to the first optical splitting unit through an optical fiber. The first optical splitting unit splits the initial pulse laser into two optical paths to obtain two first pulse lasers. The first pulse laser is input to the optical monitoring unit, which is used to detect the laser power of the first pulse laser. The second pulse laser is input to the laser adjustment and transmission module.

[0058] More specifically, the laser modulation and transmission module includes: a first adjustable optical attenuation unit connected to the second output terminal of the first optical splitter unit, used to adjust the optical attenuation value of the first pulse laser; a second optical splitter unit connected to the first adjustable optical attenuation unit, which splits the second pulse laser adjusted by the first adjustable optical attenuation unit into multiple equal paths to obtain multiple third pulse lasers; multiple second adjustable optical attenuation units, each corresponding to one of the multiple output terminals of the second optical splitter unit, used to adjust the optical attenuation value of the third pulse laser; and multiple fiber optic flanges, each fiber optic flange having its input terminal connected to a corresponding second adjustable optical attenuation unit, and its output terminal connected to multiple single-photon avalanche diodes under test via optical fibers; wherein the second optical splitter unit, the multiple second adjustable optical attenuation units, and the multiple fiber optic flanges are disposed on the same substrate. Specifically, as shown... Figure 3 As shown, the input of the first adjustable optical attenuation unit is connected to the second output of the first optical splitter unit. The output of the first adjustable optical attenuation unit is connected to the input of the second optical splitter unit through an optical fiber. The output laser of the first adjustable optical attenuation unit is divided into multiple paths by the second optical splitter unit to obtain multiple third pulse lasers. Each optical output of the second optical splitter unit is connected to the optical input of the corresponding second adjustable optical attenuation unit through an optical fiber. The optical output of the second adjustable optical attenuation unit is connected to the calibration optical fiber, the single-photon avalanche diode, and each single-photon avalanche diode under test through an optical fiber flange, providing a test light source with equal laser power for each single-photon avalanche diode under test.

[0059] To ensure temperature control during testing of the single-photon avalanche diode under test, the test module and the single-photon avalanche diode under test are sealed in a temperature control chamber. To avoid the influence of ambient light on the test, the substrate for installing the second optical splitter unit, multiple second adjustable optical attenuation units, and multiple fiber optic flanges, except for the necessary adjustment knobs which are exposed, must be shielded by adding a light shield. Black sealant is applied to the joint between the substrate and the temperature control chamber to achieve light shielding and sealing.

[0060] To prevent the temperature control box with good light-shielding effect from affecting the second optical splitter unit and multiple second adjustable optical attenuation units due to different test temperature settings, the optical fiber connection between the optical fiber flange and the second adjustable optical attenuation unit needs to be sealed with thermal insulation and sealing material.

[0061] When selecting a laser generating unit, in addition to considering the test wavelength, a narrow laser output pulse width, stable output power, external laser triggering, and synchronous laser output are also important considerations. Minimal timing jitter between the laser output and the synchronous output is also a key factor. If the laser does not have a synchronous output, the output laser can be split into a single path and received by a detector with a fast response speed and low timing jitter to achieve synchronous output.

[0062] like Figure 3 As shown, the system also includes: a timing module, which is connected to the laser generation module and the test module, which determines the timing of a single event based on the generation time of the initial pulse laser and the response time of a single-photon avalanche diode under test to the corresponding test light source, and determines the timing jitter parameters of the corresponding single-photon avalanche diode under test based on multiple single-event timings; and a power supply module, which is connected to the control module and the test module, and supplies power to the test module according to the power supply configuration signal set by the control module. Specifically, the first input terminal of the timing module is connected to the second output terminal of the laser generation unit, and the second output terminal of the laser generation unit outputs a laser synchronization signal t1, combined with... Figure 2 and Figure 3 The second input terminal of the timing module is connected to the single-channel device output signal t2 from the test module. The laser synchronization signal t1 output from the laser generation unit is used as the start time of a single event. The test module selects the output signal t2 of one of the single-photon avalanche diodes under test as the stop signal of a single event. The start time of a single event is subtracted from the stop time of the single event to obtain the timing of the single event. The control module performs half-width and half-height statistics of the timing signals based on the timing of multiple single events to obtain the timing jitter parameters of the corresponding single-photon avalanche diode under test, such as... Figure 4 As shown; the input terminal of the power supply module is connected to the control module, and the output terminal of the power supply module is connected to the power interface of the test module. The control module sets the power supply configuration signal to supply power to the test module, and the control module also monitors the output voltage of the power supply module.

[0063] It should be noted that the control module is connected to the power supply module, test module, optical monitoring unit, first optical attenuation unit, and timing module via serial port, GPIB, USB, Ethernet port, cameralink and other control and data bus methods. The control module sets and reads the working status and working parameters of these modules.

[0064] like Figure 5As shown, this application also provides a method for using a key parameter testing system for fiber optic single-photon avalanche diodes, the method including at least steps S510 to S530, including:

[0065] S510, Obtain parameter test request;

[0066] S520. Generate an initial pulse laser according to the parameter test request, adjust the optical attenuation value and separate the optical path of the initial pulse laser to obtain multiple test light sources with equal laser power;

[0067] S530. Determine the key parameters of each single-photon avalanche diode under test based on multiple pulse parameters of each single-photon avalanche diode under test when the test light source is illuminating and when the test light source is not illuminating under different test modes.

[0068] Specifically, before obtaining the parameter test request, the process also includes: adjusting the optical attenuation value of each transmission path during optical path separation to ensure that the laser power received by each single-photon avalanche diode under test is equal; and determining the pre-adjusted optical attenuation value based on the laser power of the first pulse laser after initial pulse laser optical path separation and the preset optical power threshold of the single-photon avalanche diode under test. Specifically, combined with... Figure 3 During laser transmission, the laser is not perfectly evenly distributed by the optical splitting unit; there will be some differences between the various splits. If the optical attenuation value of the optical transmission path is not adjusted, the laser power received by each fiber flange will not be completely equal. Therefore, it is necessary to first adjust the transmission path composed of the output end of the second optical splitting unit and each second adjustable optical attenuation unit and fiber flange to ensure that the laser power received by the corresponding single-photon avalanche diode under test from each fiber flange is equal. Furthermore, it is necessary to calculate the pre-adjusted optical attenuation value of the first adjustable optical attenuation unit based on the laser power output of the first optical splitting unit and the preset optical power threshold of a certain single-photon avalanche diode under test.

[0069] In detail, adjusting the optical attenuation value of each transmission path during optical path separation includes: fixing the output power and optical attenuation value of the initial pulse laser; and adjusting the optical attenuation value of each transmission path separately to make the optical attenuation values ​​of each transmission path equal. Specifically, there are two adjustment methods. The first method is to adjust the optical attenuation of the first adjustable optical attenuation unit to the lowest level, so that the power of the initial pulse laser output by the laser generating unit can be accurately detected by the optical monitoring unit after being split in two by the first optical splitting unit. Using the output power at the fiber flange of a certain transmission path as the reference power, the attenuation values ​​of the second adjustable optical attenuation units of other paths are adjusted sequentially to make the power of multiple fiber flanges equal to the reference power. The second method is to fix the first adjustable optical attenuation unit at a certain optical attenuation value, fix the output power and output frequency of the laser generating unit at a certain output value, connect the calibration single-photon avalanche diodes sequentially to each fiber flange, and adjust the second adjustable optical attenuation units of each path sequentially to make the measured optical counts of each path consistent.

[0070] In detail, determining the pre-adjusted optical attenuation value based on the laser power of the initial pulsed laser and the preset optical power threshold of the single-photon avalanche diode under test includes: setting the optical attenuation value of the first adjustable optical attenuation unit to a preset attenuation threshold (e.g., 0); determining the laser transmission loss based on the output power of the first pulsed laser and the laser power of a certain fiber flange; adjusting the output power of the first pulsed laser to the laser test power; and determining the pre-adjusted optical attenuation value based on the laser test power, optical transmission loss, and the target laser power of the test light source. Specifically, by increasing the output frequency and output laser power of the laser generating unit, the laser power is brought within the accurate monitoring range of the optical monitoring unit. After the output of the laser generating unit stabilizes, the optical monitoring unit is connected to a fiber optic flange via optical fiber. The laser power output from the fiber optic flange is recorded, and the attenuation ratio between the laser power output from the first optical splitter unit and the optical power output from the fiber optic flange is calculated to obtain the laser transmission loss. The initial pulse laser output from the laser generating unit is adjusted according to the required output frequency to adjust the laser power so that the laser power reaching the optical monitoring unit through the first optical splitter unit is the laser test power. The pre-adjusted optical attenuation value is determined by the laser test power and the optical transmission loss. That is, if the laser test power is 100nW, the target laser power required by the test light source is 1pW, and the laser transmission loss is 20dB, then after calculation, it is necessary to attenuate by 50dB from 100nW to 1pW. Therefore, the preset attenuation threshold is 30dB, which means that the first adjustable optical attenuation unit needs to be increased by 30dB.

[0071] In detail, the key parameters of each single-photon avalanche diode under test are determined based on multiple pulse parameters of each single-photon avalanche diode under test under different test modes, when the test light source is illuminating and when the test light source is not illuminating. This includes: obtaining the pulse parameters of each single-photon avalanche diode under test when receiving the test light source and when not receiving the test light source under different test modes; and determining the key parameters based on multiple pulse parameters, the frequency of the initial pulse laser, and the average number of photons per pulse when receiving the test light source.

[0072] In one embodiment of this application, the optical path is opened by an optical switch of the first adjustable optical attenuation unit, allowing the calibration single-photon avalanche diode and the single-photon avalanche diode under test to receive photons. The test modes include normal mode, optical coincidence gate mode, and delayed coincidence gate mode. The signal frequencies of the optical coincidence gate mode and the delayed coincidence gate mode are set to the same frequency as the laser, f. In optical coincidence gate mode, enabling the delay of the optical coincidence gate ensures that only the counting pulse signal generated by the light reaching the single-photon avalanche diode under test falls into the coincidence gate. The delay of the delayed coincidence gate mode relative to the optical coincidence gate can be adjusted and set to a certain delay value, such as setting a delay time (e.g., 100ns). Figure 6 As shown, the control module obtains the number of pulses in the output signal of the i-th device receiving photons within a statistical time period in normal mode, optical coincidence gate mode, and delayed coincidence gate mode within a normalized 1-second period. That is, the number of pulses under no coincidence gate, optical coincidence gate, and delayed coincidence gate modes, denoted as LightCountAi, LightCountBi, and LightCountCi, where 1≤i≤N and N is the number of single-photon avalanche diodes to be tested.

[0073] like Figure 7 As shown, the optical path is cut off by the optical switch in the first adjustable optical attenuation unit, so that the calibration single-photon avalanche diode and the single-photon avalanche diode under test cannot receive photons. Maintaining the above test conditions unchanged, after the device operating temperature stabilizes, the number of pulses of the output signal of the i-th device in normal mode, optical coincidence gate mode, and delayed coincidence gate mode within the time period is counted; that is, the number of pulses without using a coincidence gate, with an optical coincidence gate, and with a delayed coincidence gate, denoted as DarkCountAi, DarkCountBi, and DarkCountCi.

[0074] Meanwhile, the timing module uses the laser synchronization signal output by the laser generating unit as the timing start signal and the output signal of the i-th device as the timing stop signal. end The signal completes a single event timing. By statistically analyzing multiple timings within a statistical time period, the time distribution is plotted. According to the definition of time jitter, the half-width of the time distribution is the time jitter of the device.

[0075] According to the definition of Dark Count Rate (DCR), DarkCountAi is the dark count rate of the i-th device.

[0076] According to the definition of single-photon detection efficiency, the single-photon detection efficiency (SPDE) of the i-th device is obtained by formula (1):

[0077] (1)

[0078] In formula (1), SPDE is the single-photon detection efficiency, u is the number of photons from the test light source, and f is the frequency of the test light source. These are the pulse parameters when the optical path is opened in optical coincidence gate mode. These are the pulse parameters when the optical path is closed in optical coincidence gate mode.

[0079] According to the definition of afterpulse probability (APP), the afterpulse probability of the i-th device after a delay following optical triggering is obtained by formula (2). By changing the delay, when the afterpulse probability drops to a specified value, the delay is the dead time of the i-th device.

[0080] ×100%(2)

[0081] In formula (2), The probability of the subsequent pulse. To delay the pulse parameters when the optical path opens in gate mode, To delay the pulse parameters when the optical path is closed in gate mode, These are the pulse parameters when the optical path is opened in optical coincidence gate mode. These are the pulse parameters when the optical path is closed in optical coincidence gate mode.

[0082] The total post-pulse probability of the i-th device is obtained by formula (3).

[0083] ×100%(3)

[0084] In formula (3), The total probability of the subsequent pulse. These are the pulse parameters when the optical path is open in normal mode. These are the pulse parameters when the optical path is closed in normal mode. These are the pulse parameters when the optical path is opened in optical coincidence gate mode. These are the pulse parameters when the optical path is closed in optical coincidence gate mode.

[0085] This application provides a key parameter testing system for fiber-optic single-photon avalanche diodes (SPADs) and its usage method. The system provides drive for multiple SPADs under test through a test module, generates laser trigger signals based on parameter test requests, and acquires pulse parameters of each SPAD under test under different test modes with and without light source illumination. The test module and multiple SPADs are placed in a preset temperature and light-protected environment. The laser generation module generates an initial pulse signal based on the laser trigger signal and transmits the signal. The laser adjustment and transmission module adjusts the light attenuation value of the initial pulse laser and separates it into multiple test light sources with equal laser power. The laser power of the laser generation module is monitored, and the laser adjustment parameters of the laser adjustment and transmission module are configured. The key parameters of each SPAD under test are determined based on the pulse parameters. The system provided in this application ensures accurate parameter testing while rapidly detecting the key parameters of multiple SPADs. It achieves testing with and without temperature control devices through a temperature-controlled chamber, providing valuable reference for designing production and testing systems for fiber-optic SPADs.

[0086] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A key parameter testing system for an optical fiber-type single-photon avalanche diode, characterized in that, include: The test module provides reset signals for resetting multiple single-photon avalanche diodes under test, generates laser trigger signals according to parameter test requests, and acquires multiple pulse parameters of each single-photon avalanche diode under test under different test modes when the test light source is irradiated and when the test light source is not irradiated. The laser generation module is connected to the test module and generates an initial pulse laser according to the laser trigger signal and transmits the laser. The laser adjustment and transmission module, connected to the laser generation module, separates the initial pulse laser into multiple test light sources and adjusts the light attenuation value during the transmission process of the initial pulse laser to make the laser power of the multiple test light sources equal. The control module is connected to the test module, the laser generation module and the laser modulation and transmission module. It monitors the laser power of the laser generation module and configures the laser modulation parameters of the laser modulation and transmission module. It also determines the key parameters of each of the single-photon avalanche diodes under test based on multiple pulse parameters. The laser modulation and transmission module is in a light-shielding environment, and the test module and multiple single-photon avalanche diodes under test are in a light-shielding environment with a preset temperature. The different test modes include normal mode, light coincidence gate mode, and delayed coincidence gate mode. The key parameters include single-photon detection efficiency, afterpulse probability, dark count rate, and dead time. The laser modulation and transmission module includes: The first adjustable optical attenuation unit is connected to the second output terminal of the first optical splitter unit and is used to adjust the optical attenuation value of the first pulse laser. The second optical splitting unit is connected to the first adjustable optical attenuation unit, and the second pulse laser after being adjusted by the first adjustable optical attenuation unit is split into multiple equal paths to obtain multiple third pulse lasers. Multiple second adjustable optical attenuation units are connected one-to-one with the multiple output terminals of the second optical splitter unit to adjust the optical attenuation value of the third pulse laser. Multiple fiber optic flanges, each fiber optic flange having its input end connected to a corresponding second adjustable optical attenuation unit, and each fiber optic flange having its output end connected to multiple single-photon avalanche diodes under test via optical fibers. The second optical splitter unit, multiple second adjustable optical attenuation units, and multiple optical fiber flanges are disposed on the same substrate.

2. The key parameter testing system for fiber-optic single-photon avalanche diode according to claim 1, characterized in that, The testing module includes: A signal generation unit is used to provide the reset signal and the laser trigger signal; The delay control unit is used to generate different coincidence gate signals according to different test modes; The counting unit acquires multiple pulse parameters of each of the single-photon avalanche diodes under test, based on multiple coincidence gate signals, indicating whether or not the diode receives illumination from the test light source. A data transmission unit is used to transmit multiple pulse parameters.

3. The key parameter testing system for fiber-optic single-photon avalanche diode according to claim 1, characterized in that, The laser generation module includes: A laser generating unit generates the initial pulse laser according to the laser trigger signal; The first optical splitting unit performs a one-to-two optical splitting process on the initial pulse laser to obtain two first pulse lasers; The optical monitoring unit is connected to the first output terminal of the first optical splitter unit to detect the laser power of the first pulsed laser.

4. The key parameter testing system for fiber-optic single-photon avalanche diode according to claim 1, characterized in that, The system also includes: The timing module, which is connected to the laser generation module and the test module, determines the timing of a single event based on the generation time of the initial pulse laser and the response time of a certain single-photon avalanche diode under test to the corresponding test light source, so as to determine the timing jitter parameter of the single-photon avalanche diode under test based on multiple single-event timings. The power supply module is connected to the control module and the test module, and supplies power to the test module according to the power supply configuration signal set by the control module.

5. A method of using a key parameter testing system for a fiber-optic single-photon avalanche diode as described in any one of claims 1-4, characterized in that, include: Get parameter test request; An initial pulse laser is generated according to the parameter test request. The optical attenuation value of the initial pulse laser is adjusted and the optical path is separated to obtain multiple test light sources with equal laser power. The key parameters of each single-photon avalanche diode under test are determined based on multiple pulse parameters of each single-photon avalanche diode under test when illuminated by the test light source and when not illuminated by the test light source under different test modes.

6. The method of using the key parameter testing system for fiber-optic single-photon avalanche diodes according to claim 5, characterized in that, Before obtaining the parameter test request, it also includes: Adjust the optical attenuation value of each transmission path during the optical path separation process to make the laser power received by each of the single-photon avalanche diodes under test equal; The pre-adjusted optical attenuation value is determined based on the laser power of the first pulse laser after the initial pulse laser optical path separation and the preset optical power threshold of the single-photon avalanche diode under test.

7. The method of using the key parameter testing system for fiber-optic single-photon avalanche diodes according to claim 6, characterized in that, Adjusting the optical attenuation value of each transmission path during optical path separation includes: The output power and optical attenuation value of the initial pulse laser are fixed. Adjust the optical attenuation value of each transmission path to make the optical attenuation value of each transmission path equal.

8. The method of using the key parameter testing system for fiber-optic single-photon avalanche diodes according to claim 6, characterized in that, The pre-adjusted optical attenuation value is determined based on the laser power of the initial pulse laser and the preset optical power threshold of the single-photon avalanche diode under test, including: Set the optical attenuation value corresponding to the first pulse laser to a preset attenuation threshold; The laser transmission loss is determined based on the output power of the first pulsed laser and the laser power of a certain test light source. The output power of the first pulsed laser is adjusted to the laser test power, and the pre-adjusted optical attenuation value is determined based on the laser test power, the optical transmission loss, and the target laser power of the test light source.

9. The method of using the key parameter testing system for fiber-optic single-photon avalanche diodes according to claim 5, characterized in that, The key parameters of each single-photon avalanche diode under test are determined based on multiple pulse parameters obtained under different test modes, including when the test light source is illuminating and when the test light source is not illuminating. Acquire pulse parameters for each of the single-photon avalanche diodes under test when receiving the test light source and when not receiving the test light source under the different test modes; The key parameters are determined based on multiple pulse parameters, the frequency of the initial pulse laser, and the average number of photons per pulse received from the test light source.

Images