A method and device for measuring light

Abstract

The present invention discloses a method and device for measuring light, which relates to the technical field of optical systems. The method comprises step S1: obtaining a preset measuring time length T meas and wavelength λ, the predicted optical power of the continuous light to be measured or the predicted energy of the optical pulse to be measured; step S21: obtaining the serial number of the rotary hole of the variable attenuator according to the relationship table; step S22: controlling the attenuation value of the variable attenuator according to the serial number of the rotary hole; detection step: working in counter mode when obtaining optical power, and working in timer mode when obtaining energy; judgment step: when it is not in the linear detection range of the single-photon detector, adjusting the attenuation value accordingly and then executing step S22 until it is in the linear detection range; step S6: obtaining the measurement result of the light to be measured; the device includes a variable attenuator, a single-photon detector, a data acquisition unit, a controller and a computer, and the attenuation value of the variable attenuator is adjusted accordingly according to needs, thereby improving the measurement work efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of optical systems, and in particular to a method and device for measuring light. Background Art

[0002] Optical power meters and optical energy meters are instruments for measuring light intensity. Optical power meters measure the average power of light, while energy meters measure the energy of light pulses. Many instruments can measure both optical power and energy, and are called optical power and energy meters.

[0003] The current optical power meters and optical energy meters have the following technical problems: Since the optical attenuation value of the attenuator currently used in the measurement cannot be adjusted, the applicability is poor; replacing the attenuator with different optical attenuation values ​​leads to low measurement efficiency.

[0004] Since the optical path structure of wide-spectrum achromatic fiber coupling is relatively complex, the cost performance is poor. Summary of the invention

[0005] The invention provides a method and device for measuring light, which solve the technical problem of low measuring efficiency.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows: A method for measuring light, comprising the following steps: Step S1: Obtaining a preset measurement time length T meas and the wavelength λ of the light to be measured, to obtain the predicted optical power of the continuous light to be measured or the predicted energy of the optical pulse to be measured; Step S21: Based on the obtained predicted optical power or predicted energy, the initial attenuation value of the variable attenuator and the serial number of the rotary hole are obtained according to a relationship table of the predicted optical power, the predicted energy, the initial attenuation value and the serial number of the rotary hole; Step S22: controlling the stepper motor to rotate according to the sequence number of the wheel hole until the corresponding wheel hole is located on the optical path, so that the variable attenuator works at the set attenuation value, and obtaining the total transmittance of the variable attenuator according to the relationship table of the wheel hole sequence number, attenuation value and transmittance based on the sequence number of the wheel hole; Detection steps: when obtaining optical power, controlling the data acquisition unit to work in a counter mode to obtain continuous light parameters; when obtaining energy, controlling the data acquisition unit to work in a timer mode to obtain pulse light parameters when the light to be measured is pulse light; and obtaining continuous light parameters and pulse light parameters when the light to be measured is a mixture of pulse and continuous light; Determining step: whether it is in the linear detection range of the single photon detector. If it is not in the linear detection range of the single photon detector, adjust the attenuation value accordingly and then detect again, and execute step S22 until it is in the linear detection range of the single photon detector; Step S6: Obtain the measurement result of the light to be measured.

[0007] A further technical solution is that: the detection step is specifically divided into step S31, step S41, step S32, step S4201 and step S4202, the determination step is specifically divided into step S51 and step S52, in step S22, when obtaining optical power, step S31, step S41 and step S51 are executed, and when obtaining energy, step S32, step S4201, step S4202 and step S52 are executed; Step S31: Control the data acquisition unit to work in counter mode, accumulate all signals output by the single-photon detector within the measurement time, and obtain the total value N of the measurement; Step S41: Calculate the photon number rate n of the continuous light to be measured according to formula (1): cw , according to formula (2), the optical power P is calculated cw , execute step S51; ; In formula (1), n cw is the photon rate of the light to be measured, unit s -1 ; T meas To measure the length of time, in seconds, P dark is the dark count rate of the single-photon detector, in cps; η is the detection efficiency of the single-photon detector, α is the total transmittance of the variable attenuator, and β is the linear fitting coefficient of the current count value of the single-photon detector; ; In formula (2), P cw is the optical power, in W; h is Planck's constant, h=6.6260693×10 -34 J·s; c is the speed of light, c=299792458m / s; λ is the wavelength of the light to be measured, unit: m; Step S51: When 1kcps≤N / T meas ≤10Mcps, β≤1.2, it is known that it is in the linear detection range of the single-photon detector, and step S6 is executed; when N / T meas When >10Mcps, it is known that the linear detection range of the single-photon detector is exceeded, and the number of the wheel hole is increased by one; when N / T meas When the count rate is <1 kcps, it is known that the count rate is too close to the noise floor of the single-photon detector, and the sequence number of the wheel hole is reduced by one; the updated sequence number of the wheel hole is obtained, and step S22 is executed; Step S32: Control the data acquisition unit to work in the timer mode, record the occurrence time of all single-photon detector output signals within the measurement time, and obtain the time data of the single-photon detector output signals; Step S4201: Based on the time data of the single-photon detector output signals, use the PIC analysis method to calculate the total number of light pulses within the measurement time and the time interval T' between adjacent output signals, use the time interval T' between adjacent output signals as the period T of the light pulse to be measured, and construct the synchronization signal sync of the light pulse to be measured based on the time data of the single-photon detector output signals and the time interval T' between adjacent output signals i , i is the serial number of the light pulse; Step S4202: Synchronization signal sync based on the optical pulse to be measured i The TCSPC analysis method is used to calculate each detection signal and the corresponding synchronization signal sync i The time interval ∆t i , based on all time intervals ∆t i The distribution of the count peak envelope in the histogram is obtained, and the pulse width of the count peak envelope in the histogram is the light pulse width of the light to be measured. Based on the histogram, the photon count N in the count peak envelope is obtained. pulse The total count outside the counting peak envelope is taken as the total count N. The average photon number μ of a single pulse in the light to be measured is calculated according to formula (3). The energy of a single pulse E is calculated according to formula (4). p ; The average number of photons per pulse μ and the energy of a single pulse E p The calculation formula is: ; In formula (3), μ is the average number of photons in a single pulse, N pulse is the photon count within the counting peak envelope; ; In formula (4), E p is the single pulse energy; Step S52: When 0.0001≤T'·N pulse / T meas ≤0.1, it is known that it is in the linear detection range of the single-photon detector, and step S6 is executed; when T'·N pulse / T meas >0.1, it is known that the linear detection range of the single-photon detector is exceeded, and the number of the wheel hole is increased by one; when T'·N pulse / T meas <0.0001, it is known that the counting rate is too close to the noise floor of the single-photon detector, and the serial number of the wheel hole is reduced by one; the updated serial number of the wheel hole is obtained, and step S22 is executed.

[0008] A further technical solution is that: in the step S1, the basic characteristics of the selected light to be measured are obtained, when the basic characteristics of the light to be measured are continuous light, the predicted optical power of the continuous light to be measured is obtained; when the basic characteristics of the light to be measured are pulsed light or unknown, the predicted energy of the light pulse to be measured is obtained; the measurement time length T meas , the range is 1ms~100s; select from the following options to obtain the predicted optical power of the continuous light to be measured: P1: ≤100fw; P2: 100fw~10pw; P3: 10pw~1nW; P4: 1nW~100nW; P5: 100nW~10μW; P6: 10μW~10mW; P7: unknown; Select from the following options to obtain the predicted energy of the optical pulse to be measured: E1: ≤ 10 -4 fJ; E2: 10 -4 fJ~10 -2 fJ; E3: 10 -2 fJ~1 fJ; E4: 1 fJ~100 fJ; E5: 100 fJ~10 pJ; E6: 100 fJ~1 nJ; E7: Unknown.

[0009] A further technical solution is that: in step S4202, the envelope peak value in the histogram is the time interval T' between adjacent output signals; in step S4202, the photon number rate n of the continuous light part in the light to be measured is calculated according to formula (1) cw , according to formula (2), the optical power P is calculated cw .

[0010] A further technical solution is that: the detection step further includes a step S4203 after the step S4202, in which the step S4203: obtaining a preset search range ∆T and a step length, and obtaining the time interval T′ of the corresponding adjacent output signals with the smallest pulse width based on the step length traversal search within the range of the time interval T′±∆T of the adjacent output signals, and correspondingly obtaining the most matching optical pulse period, and then calculating and obtaining the optical pulse repetition frequency, optical pulse width, single pulse average photon number μ and single pulse energy E p .

[0011] A further technical solution is: in step S4203, the search range ∆T is set to 100ns and the step length is 1ps; if the light to be measured contains a continuous light part, the power P of the continuous light is calculated. cw and the photon number rate n cw .

[0012] A further technical solution is that: in step S6, when the light is continuous, the continuous light parameters include the light power P cw and the photon number rate n cw When it is pulse light, the pulse light parameters include single pulse energy E p , the average number of photons per pulse μ, the light pulse repetition frequency and the light pulse width; when it is a mixture of pulsed and continuous light, the continuous light parameters and the pulsed light parameters are obtained; when the step S51 or the step S52 is judged to exceed the linear detection range and the attenuation value of the variable attenuator has been adjusted to the maximum, a saturation warning is obtained.

[0013] A device for measuring light, used in any one of the above-mentioned methods for measuring light, comprising a variable attenuator, a single-photon detector, a data acquisition unit, a controller and a computer, wherein the variable attenuator, the single-photon detector, the data acquisition unit and the controller form a measuring unit, the variable attenuator is used to connect to the light to be measured, the variable attenuator is connected to the single-photon detector, the single-photon detector is electrically connected to the data acquisition unit, the data acquisition unit is electrically connected to the controller, the controller is electrically connected to the computer, and the controller is electrically connected to the control port of the variable attenuator.

[0014] A further technical solution is that the variable attenuator includes a box, a motor-side control port fixed on the box, an input optical fiber interface and an output optical fiber interface, a variable attenuator drive unit fixed in the box, a stepper motor, a concave reflector, a reflector fixing frame, an optical fiber fixing frame, an input optical fiber and an output optical fiber, and an optical attenuation plate rotating wheel located in the box; the variable attenuator drive unit, the stepper motor, the reflector fixing frame and the optical fiber fixing frame are all fixedly connected to the box, the concave reflector is fixedly connected to the reflector fixing frame, the input optical fiber and the output optical fiber are fixedly connected to the optical fiber fixing frame, and the optical attenuation plate rotating wheel is fixedly connected to the rotating shaft of the stepper motor; a plurality of optical attenuation plates are arranged on the optical attenuation plate rotating wheel; one end of the input optical fiber is connected to the input optical fiber interface, and the other end of the input optical fiber is connected to the input optical fiber fixing frame. The optical fiber is a light outlet, one end of the output optical fiber is connected to the output optical fiber interface, and the other end of the output optical fiber is a light inlet; the light outlet of the input optical fiber and the light inlet of the output optical fiber are located on the same side of the light attenuation plate of the light attenuation plate rotating wheel, the concave reflector is located on the other side of the light attenuation plate of the light attenuation plate rotating wheel, the light outlet of the input optical fiber is located on one side of the normal line of the concave reflector, and the light inlet of the output optical fiber is located on the other side of the normal line of the concave reflector; the input optical fiber is used to connect the light to be measured, the output optical fiber interface of the variable attenuator is connected to the input end of the single-photon detector through the output optical fiber, the control end of the controller is connected to the motor side control port of the variable attenuator, the motor side control port is electrically connected to the control end of the variable attenuator driving unit, and the output end of the variable attenuator driving unit is electrically connected to the stepping motor.

[0015] A further technical solution is that: a total of six wheel holes, from the first to the sixth wheel holes, are opened on the light attenuation sheet wheel, and the six wheel holes are evenly distributed on the light attenuation sheet wheel, no light attenuation sheet is fixed on the first wheel hole, a first light attenuation sheet is clamped and fixed on the second wheel hole to form a first group of light attenuation sheets, a first light attenuation sheet and a second light attenuation sheet are clamped and fixed on the third wheel hole to form a second group of light attenuation sheets, a first light attenuation sheet and a third light attenuation sheet are clamped and fixed on the fourth wheel hole to form a third group of light attenuation sheets, a first light attenuation sheet and a fourth light attenuation sheet are clamped and fixed on the fifth wheel hole to form a fourth group of light attenuation sheets, and two first light attenuation sheets and a fourth light attenuation sheet are clamped and fixed on the sixth wheel hole to form a fifth group of light attenuation sheets.

[0016] The beneficial effects of adopting the above technical solution are: First, a method for measuring light, comprising the following steps: Step S1: obtaining a preset measurement time length T meas, obtain the predicted optical power of the continuous light to be measured or the predicted energy of the optical pulse to be measured; step S21: based on the obtained predicted optical power or predicted energy, obtain the initial attenuation value of the variable attenuator and the serial number of the wheel hole according to the relationship table of the predicted optical power, predicted energy, initial attenuation value and the serial number of the wheel hole; step S22: control the stepper motor to rotate according to the serial number of the wheel hole until the corresponding wheel hole is located on the optical path, so that the variable attenuator works at the set attenuation value, and obtain the total transmittance of the variable attenuator based on the serial number of the wheel hole according to the relationship table of the wheel hole number, attenuation value and transmittance; detection step : When obtaining optical power, the data acquisition unit is controlled to work in counter mode to obtain continuous light parameters; when obtaining energy, the data acquisition unit is controlled to work in timer mode, and pulse light parameters are obtained when the light to be measured is pulse light; continuous light parameters and pulse light parameters are obtained when the light to be measured is a mixture of pulse and continuous light; judgment step: whether it is in the linear detection range of the single photon detector, when it is not in the linear detection range of the single photon detector, the attenuation value is adjusted accordingly and then detected again, and step S22 is executed until it is in the linear detection range of the single photon detector; step S6: obtain the measurement result of the light to be measured. The attenuation value of the variable attenuator is adjusted accordingly as needed to improve the measurement efficiency.

[0017] Second, a light measuring device, used in any one of the above-mentioned methods for measuring light, comprises a variable attenuator, a single photon detector, a data acquisition unit, a controller and a computer, wherein the variable attenuator, the single photon detector, the data acquisition unit and the controller form a measuring unit, the variable attenuator is used to connect with the light to be measured, the variable attenuator is connected with the single photon detector, the single photon detector is electrically connected with the data acquisition unit, the data acquisition unit is electrically connected with the controller, the controller is electrically connected with the computer, and the controller is electrically connected with the control port of the variable attenuator. The attenuation value of the variable attenuator is adjusted accordingly as needed, thereby improving the efficiency of the measurement work.

[0018] Third, during measurement, there is always a wheel hole in the optical path. When the attenuation value needs to be adjusted, the light attenuation plate wheel is driven by a stepper motor to rotate, and can be switched to any set attenuation value, thereby achieving a wider range of light attenuation adjustment. Since the light attenuation plate of each wheel hole is fixed, each adjustment only switches between these fixed attenuation plates, which can achieve extremely high repeatability.

[0019] Fourth, compared with traditional transmissive lenses, concave reflectors only require one device to achieve wide-spectrum achromatic fiber coupling, which has a better cost-effectiveness.

[0020] Please refer to the detailed description of the specific implementation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a principle block diagram of the present invention; Figure 2-1 It is the block diagram of the variable attenuator; Figure 2-2 yes Figure 2-1 The structural diagram of the medium light attenuation plate wheel; Figure 2-3 is the optical path distribution diagram of the variable attenuator; Figure 3 It is the timing diagram of the data acquisition unit; Figure 4 It is a structural diagram of the present invention; Figure 5 is a flow chart of Embodiment 3 of the present invention; Figure 6 This is a screenshot of the time series data in the PIC analysis method; Figure 7 is a screenshot of the timing data in the TCSPC analysis method.

[0022] Wherein: 1 optical attenuation plate wheel, 2-1 first wheel hole, 2-2 second wheel hole, 2-3 third wheel hole, 2-4 fourth wheel hole, 2-5 fifth wheel hole, 2-6 sixth wheel hole, 3 closed-loop control stepper motor, 4 concave reflector, 5 reflector fixing frame, 6 input optical fiber interface, 7 output optical fiber interface, 8 input optical fiber, 9 output optical fiber, 10 optical fiber fixing frame, 11 box, 12 optical attenuation plate, 13 wheel type variable attenuator, 14 silicon avalanche photodiode single photon detector, 15 FPGA board, 16 laptop computer, 17 cable line, 18 data line, 19 wheel motor control line, 20 light to be measured. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0024] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0025] Embodiment 1: like Figure 1As shown, the present invention discloses a measuring device for light, including a variable attenuator, a single photon detector, a data acquisition unit, a controller, a USB3.0 interface, a controller-side control port, a computer and a program module. The variable attenuator, the single photon detector, the data acquisition unit and the controller form a measuring unit.

[0026] like Figure 2-1 As shown, the variable attenuator includes a box body 11, a motor side control port fixed on the box body 11, an input optical fiber interface 6 and an output optical fiber interface 7, a variable attenuator driving unit fixed in the box body 11, a closed-loop control stepping motor 3, a concave reflector 4, a reflector fixing frame 5, an optical fiber fixing frame 10, an input optical fiber 8 and an output optical fiber 9, and an optical attenuation sheet rotating wheel 1 located in the box body 11, the variable attenuator driving unit, the closed-loop control stepping motor 3, the reflector fixing frame 5 and the optical fiber fixing frame 10 are all fixedly connected to the box body 11, the concave reflector 4 is fixedly connected to the reflector fixing frame 5, the input optical fiber 8 and the output optical fiber 9 are both fixedly connected to the optical fiber fixing frame 10, and the optical attenuation sheet rotating wheel 1 is fixedly connected to the rotating shaft of the closed-loop control stepping motor 3.

[0027] like Figure 2-2 As shown, a total of six wheel holes from the first to the sixth wheel holes are provided on the light attenuation sheet wheel 1, and the six wheel holes are evenly distributed on the light attenuation sheet wheel 1. No light attenuation sheet is fixed on the first wheel hole 2-1, a first light attenuation sheet is snap-fixed on the second wheel hole 2-2 to form a first group of light attenuation sheets, a first light attenuation sheet and a second light attenuation sheet are snap-fixed on the third wheel hole 2-3 to form a second group of light attenuation sheets, a first light attenuation sheet and a third light attenuation sheet are snap-fixed on the fourth wheel hole 2-4 to form a third group of light attenuation sheets, a first light attenuation sheet and a fourth light attenuation sheet are snap-fixed on the fifth wheel hole 2-5 to form a fourth group of light attenuation sheets, and two first light attenuation sheets and a fourth light attenuation sheet are snap-fixed on the sixth wheel hole 2-6 to form a fifth group of light attenuation sheets.

[0028] The light attenuation sheets are mounted in the six mounting holes in the wheel assembly.

[0029] As shown in Table 1, this application selects four types of light attenuation sheets.

[0030] Table 1: Attenuation sheet parameters Attenuator serial number type Working wavelengthnm Diameter (mm) Attenuation dB ① Absorption 300-1100 25 10 ② Reflective 350-1100 25 10 ③ Reflective 350-1100 25 20 ④ Reflective 350-1100 25 30 As shown in Table 2, 0 to 3 light attenuation sheets are selected for each hole to form six levels of attenuation values.

[0031] Table 2: Relationship between wheel hole number, attenuation value and transmittance Rotor hole number Combination Total round trip attenuation dB Total round trip transmittance 1 null 0 1.0 2 ① 20 <![CDATA[1.0×10 -2 ]]> 3 ①+② 40 <![CDATA[1.0×10 -4 ]]> 4 ①+③ 60 <![CDATA[1.0×10 -6 ]]> 5 ①+④ 80 <![CDATA[1.0×10 -8 ]]> 6 ①+④+① 100 <![CDATA[1.0×10 -10 ]]> During measurement, there is always a wheel hole in the optical path to achieve the corresponding light attenuation. When the attenuation value needs to be adjusted, the light attenuation plate wheel 1 is driven by the stepper motor to rotate. Every 60 degrees of rotation, it can switch to a nearby hole. According to the current attenuation value, that is, the current stepper motor rotation angle position, by adjusting the rotation angle, it can switch to any set attenuation value. A wide range of light attenuation adjustment can be achieved, and since the light attenuation plate of each hole is fixed, each adjustment is just switching between these fixed attenuation plates, which can achieve extremely high repeatability.

[0032] like Figure 2-1 As shown, one end of the input optical fiber 8 is connected to the input optical fiber interface 6, and the other end of the input optical fiber 8 is the light outlet; one end of the output optical fiber 9 is connected to the output optical fiber interface 7, and the other end of the output optical fiber 9 is the light entrance.

[0033] like Figure 2-3 As shown, the light outlet of the input optical fiber 8 and the light inlet of the output optical fiber 9 are located on the same side of the light attenuation plate 12 of the light attenuation plate rotating wheel 1, the concave reflector 4 is located on the other side of the light attenuation plate 12 of the light attenuation plate rotating wheel 1, the light outlet of the input optical fiber 8 is located on one side of the normal of the concave reflector 4, and the light inlet of the output optical fiber 9 is located on the other side of the normal of the concave reflector 4.

[0034] like Figure 1 As shown, the light to be measured is connected to the input fiber interface of the variable attenuator through the input fiber, the output fiber interface of the variable attenuator is connected to the input end of the single photon detector through the output fiber, the output end of the single photon detector is electrically connected to the input end of the data acquisition unit through the cable, the output end of the data acquisition unit is electrically connected to the input end of the controller, the controller is electrically connected to the USB3.0 interface, the USB3.0 interface is connected to the computer through the data line, the control end of the controller is electrically connected to the control port on the controller side, and the control port on the controller side is electrically connected to the control port on the motor side of the variable attenuator through the control line. The control port on the motor side is electrically connected to the control end of the variable attenuator drive unit, and the output end of the variable attenuator drive unit is electrically connected to the stepping motor.

[0035] The variable attenuator is described in detail below.

[0036] like Figure 2-1 As shown, the optical path structure principle, the input optical fiber interface 6 and the input optical fiber 8 guide the light to be measured into the variable attenuator.

[0037] like Figure 2-3As shown, the numerical aperture of the optical fiber determines the divergence angle of the light emitted from the end face of the optical fiber. The output light at the light outlet of the input optical fiber 8 propagates in a gradually divergent state, passes through the light attenuation plate 12 and irradiates the concave reflector 4. After reflection, this beam of light begins to propagate in a gradually converging state, then passes through the light attenuation plate again, and finally converges to the light inlet of the output optical fiber 9. The light outlet of the input optical fiber 8 and the light inlet of the output optical fiber 9 are on both sides of the optical axis of the concave reflector 4, and the distance from the optical axis, i.e., the normal line, is 1 mm. The input optical fiber 8 uses a multimode optical fiber with a core diameter of 105 μm and a numerical aperture NA=0.22; the output optical fiber 9 uses a multimode optical fiber with a core diameter of 200 μm and a numerical aperture NA=0.22; the concave reflector 4 uses a silver-plated film with a focal length f=38.1 mm; the distance between the light outlet of the input optical fiber 8 and the light inlet of the output optical fiber 9 and the central front surface of the concave reflector 4 is 76.2 mm. The optical fiber-concave reflector-optical fiber composition has an imaging structure with both object distance and image distance of 2f. Compared with the traditional transmission lens, the concave reflector 4 only needs one device to achieve wide-spectrum achromatic optical fiber coupling.

[0038] The single photon detector is a silicon avalanche photodiode single photon detector Si-SPAD, which is described in detail as follows.

[0039] A single photon detector is a photoelectric detector that can detect a single photon. Photons are the basic energy unit of light. When a single photon detector detects a photon, it will output it in the form of an electrical pulse. Si-SPAD works in continuous detection mode, with a wavelength response range of 400nm to 1100nm, a peak wavelength detection efficiency of ~65%, a dark count rate of ~200cps, i.e. counts / second, and a saturation count rate of ~15Mcps. When the maximum count rate of linear detection is ≤10Mcps, the nonlinear fitting coefficient β is ≤1.2.

[0040] The data acquisition unit and controller based on the FPGA board 15 are described in detail as follows.

[0041] The controller is xc7A-75T chip, and the data acquisition unit supports two working modes: counter mode and timer mode.

[0042] like Figure 3 As shown in the figure, in the counter mode, all the electrical pulse signals output by the single-photon detector SPAD are accumulated within the measurement time, and finally a total value N of the measurement is obtained. In the timer mode, within the measurement time, starting from the measurement start time, the time of all the single-photon detector SPAD output signals is recorded, and finally these time information T1, T2, …, T n .

[0043] like Figure 1As shown, the controller is responsible for communicating with the computer, uploading the collected data to the computer, and receiving control instructions from the computer to adjust the working parameters of the counter or timer, or control the attenuation value of the variable attenuator.

[0044] The computer program module is described in detail as follows. The computer program provides a human-machine interface, through which the user can control the operation of an ultra-high sensitivity optical power and energy meter USOM, process data and output measurement results. The measurement results of continuous light include optical power and photon number rate; the measurement results of pulsed light include single pulse energy, average number of photons per pulse, optical pulse width and optical pulse repetition frequency. When the light to be measured is a mixture of pulsed light and continuous light, the measurement results of the two lights are output simultaneously.

[0045] like Figure 4 As shown, the variable attenuator is a rotary variable attenuator 13, the single photon detector is a silicon avalanche photodiode single photon detector 14, abbreviated as Si-SPAD; the data acquisition unit, the controller, the USB3.0 interface and the controller side control port form an FPGA board 15; the computer is a laptop computer 16; the optical signal: the light to be measured 20 is connected to the rotary variable attenuator 13 through the input optical fiber 8, and the attenuated light to be measured is guided by the output optical fiber 9 into the silicon avalanche photodiode single photon detector 14 for detection. Electrical signal: the output signal of the silicon avalanche photodiode single photon detector 14 is connected to the FPGA board 15 by the cable 17, and the data collected by the FPGA board 15 is uploaded to the laptop computer 16 by the USB data line 18. Control signal: the computer control instruction is downloaded to the FPGA board 15 through the USB data line 18, and then the FPGA board 15 interprets the computer control instruction and transmits the control signal to control the motor through the rotary motor control line 19.

[0046] The present application proposes a light measurement device, which is an ultra-high sensitivity optical power and energy meter USOM, and its features include: (1) High sensitivity. Compared with the optical power and energy meter of the traditional photodiode sensor, the sensitivity of this application is improved by about five orders of magnitude.

[0047] (2) It has the function of measuring the width of optical pulses.

[0048] (3) It has the function of measuring unknown light that is a mixture of continuous light and pulsed light.

[0049] Embodiment 2: like Figure 5 As shown, the present invention discloses a method for measuring light, based on a device for measuring light described in Example 1, comprising the following steps: Step S1: Obtain input initial parameters.

[0050] The operator opens the computer software and enters the initial parameters in the software interface, as follows.

[0051] Step S11: The computer obtains the measurement time length T set by the operator meas The computer obtains the wavelength λ of the light to be measured set by the operator, which ranges from 1ms to 100s. -7 ~1.1Î10 -6 m.

[0052] Step S12: The operator selects one from the two options of continuous light, pulsed light or unknown, and the computer obtains the basic characteristics of the light to be measured. When the user selects continuous light, step S1301 is executed; when the user selects pulsed light or unknown, step S1302 is executed.

[0053] Step S1301: When the user selects continuous light, the computer prompts the operator to select the predicted optical power of the continuous light to be measured, obtains the predicted optical power of the continuous light to be measured and executes step S2101, selecting from the following options: P1: ≤100fw; P2: 100fw~10pw; P3: 10pw~1nW; P4: 1nW~100nW; P5: 100nW~10μW; P6: 10μW~10mW; P7: Unknown.

[0054] Step S1302: When the user selects "Containing Pulsed Light" or "Unknown", the computer prompts the operator to select the predicted energy of the light pulse to be measured, obtains the predicted energy of the light pulse to be measured and executes step S2102, selecting from the following options: E1: ≤ 10 -4 fJ; E2: 10 -4 fJ~10 -2 fJ; E3: 10 -2 fJ~1 fJ; E4: 1 fJ~100 fJ; E5: 100 fJ~10 pJ; E6: 100 fJ~1 nJ; E7: Unknown.

[0055] Step S2: Obtain the attenuation value of the variable attenuator.

[0056] Step S2 includes step S21 and step S22.

[0057] Step S21: The computer obtains the initial attenuation value of the variable attenuator and the serial number of the wheel hole based on the obtained predicted optical power or predicted energy and according to the relationship table of the predicted optical power, predicted energy, initial attenuation value and the serial number of the wheel hole, takes the initial attenuation value as the attenuation value set by the variable attenuator, and sends the attenuation value of the variable attenuator and the serial number of the wheel hole to the controller. The controller obtains the attenuation value of the variable attenuator and the serial number of the wheel hole, and executes steps S2101, S2201 and S31 when the predicted optical power is obtained, and executes steps S2102, S2202 and S32 when the predicted energy is obtained. Step S21 includes steps S2101 and S2102, which are described in detail as follows.

[0058] Step S2101: The computer obtains the initial attenuation value of the variable attenuator and the serial number of the wheel hole based on the obtained predicted optical power and according to the relationship table of the predicted optical power, predicted energy, initial attenuation value and the serial number of the wheel hole, takes the initial attenuation value as the attenuation value set for the variable attenuator, and sends the attenuation value of the variable attenuator and the serial number of the wheel hole to the controller. The controller obtains the attenuation value of the variable attenuator and the serial number of the wheel hole, and executes step S2201.

[0059] Step S2102: The computer obtains the initial attenuation value of the variable attenuator and the serial number of the wheel hole based on the obtained predicted energy and according to the relationship table of predicted optical power, predicted energy, initial attenuation value and wheel hole number, takes the initial attenuation value as the attenuation value set for the variable attenuator, and sends the attenuation value of the variable attenuator and the serial number of the wheel hole to the controller. The controller obtains the attenuation value of the variable attenuator and the serial number of the wheel hole, and executes step S2202.

[0060] Details are as follows.

[0061] During the initial setting, according to the parameters selected in step S1301 or step S1302, a suitable initial attenuation value is calculated and set. The specific parameters are shown in Table 3.

[0062] Table 3: Relationship between predicted optical power, predicted energy, initial attenuation value and wheel hole number Step S1301 Step S1302 Initial attenuation value dB Rotor hole number P1: ≤100 <![CDATA[E1: ≤10 -4 f ]]> 0 1 P2: 100～10 <![CDATA[E2: 10 -4 f ~10 -2 f ]]> 20 2 P3: 10～1 <![CDATA[E3: 10 -2 f ~1 f ]]> 40 3 P4: 1～100 E4: 1～100 60 4 P5: 100～10 E5: 100～10 80 5 P6: 10～10 E6: 10～1 100 6 P7: Unknown E7: Unknown 100 6 Step S22: The controller obtains the updated attenuation value of the variable attenuator and the serial number of the wheel hole. The controller controls the rotation of the stepper motor according to the serial number of the wheel hole so that the corresponding wheel hole is located on the optical path, so that the variable attenuator works at the set attenuation value. Based on the serial number of the wheel hole, the total transmittance of the variable attenuator is obtained according to the relationship table of the wheel hole number, attenuation value and transmittance. Step S31 is executed when the optical power is obtained, and step S32 is executed when the energy is obtained.

[0063] Step S22 includes step S2201 and step S2202, which are described in detail as follows.

[0064] Step S2201: The controller obtains the updated attenuation value of the variable attenuator and the serial number of the wheel hole. The controller controls the rotation of the stepper motor according to the serial number of the wheel hole so that the corresponding wheel hole is located on the optical path, so that the variable attenuator works at the set attenuation value. Based on the serial number of the wheel hole, the total transmittance of the variable attenuator is obtained according to the relationship table of the wheel hole number, attenuation value and transmittance, and step S31 is executed.

[0065] Step S2202: The controller obtains the updated attenuation value of the variable attenuator and the serial number of the wheel hole. The controller controls the rotation of the stepper motor according to the serial number of the wheel hole so that the corresponding wheel hole is located on the optical path, so that the variable attenuator works at the set attenuation value. Based on the serial number of the wheel hole, the total transmittance of the variable attenuator is obtained according to the relationship table of the wheel hole number, attenuation value and transmittance, and step S32 is executed.

[0066] Step S3: Collect detection signals in counter mode or timer mode.

[0067] The single photon detector Si-SPAD detects the light to be measured and collects data.

[0068] Step S3 includes step S31 and step S32.

[0069] Step S31: When continuous light is selected in step S1, the controller controls the data acquisition unit to work in counter mode, accumulates all signals output by the single-photon detector Si-SPAD within the measurement time, and obtains a measured total value N, and executes step S41.

[0070] Step S32: When pulse light or unknown is selected in step S1, the controller controls the data acquisition unit to work in timer mode, records the occurrence time of all single-photon detector Si-SPAD output signals within the measurement time, obtains the time data of the single-photon detector Si-SPAD output signals, and executes step S42.

[0071] Step S4: Calculate light parameters in counter mode or timer mode.

[0072] Step S4 includes step S41 and step S42.

[0073] Step S41: Divide the total value N by the measurement time length T meas Get N / T meas , obtain the linear fitting coefficient β of the current count value of the single-photon detector Si-SPAD, and calculate the photon number rate n of the continuous light to be measured based on the measured total value N and the attenuation value of the variable attenuator according to formula (1):cw , according to formula (2), the optical power P is calculated cw , execute step S51.

[0074] When continuous light is selected in step S1, the photon rate n of the light to be measured is calculated according to the total value N, the performance parameters of the single photon detector Si-SPAD and the attenuation value of the variable attenuator. cw。

[0075] ; In formula (1), n cw is the photon rate of the light to be measured, unit s -1 ; T meas To measure the length of time, in seconds, P dark is the dark count rate of the single-photon detector Si-SPAD, in cps; η is the detection efficiency of the single-photon detector Si-SPAD, α is the total round-trip transmittance of the variable attenuator, α includes the fixed attenuation of other optical paths in the system, and β is the linear fitting coefficient of the current count value of the single-photon detector Si-SPAD.

[0076] According to the photon number rate n cw , calculate the optical power P cw .

[0077] ; In formula (2), P cw is the optical power, in W; h is Planck's constant, h=6.6260693×10 -34 J·s; c is the speed of light, c=299792458m / s; λ is the wavelength of the light to be measured, unit: m.

[0078] Step S42: Calculate and obtain pulse light parameters based on the obtained time data of the single photon detector Si-SPAD output signal and the attenuation value of the variable attenuator. If the pulse light contains a continuous light part, calculate its light parameters at the same time. Execute step S52.

[0079] Step S42 includes step S4201, step S4202 and step S4203.

[0080] When step S1 selects pulse light or unknown, the various parameters of the pulse light are calculated based on the collected time data, the performance parameters of the single-photon detector Si-SPAD and the attenuation value of the variable attenuator. If the pulse light contains a continuous light part, its light parameters are calculated at the same time. The specific steps are as follows: Step S4201: Based on the time data of the single-photon detector Si-SPAD output signal, the total number of light pulses within the measurement time and the time interval T' between adjacent output signals are calculated using the PIC analysis method, and the time interval T' between adjacent output signals is used as the period T of the light pulse to be measured. Based on the time data of the single-photon detector Si-SPAD output signal and the time interval T' between adjacent output signals, a synchronization signal sync of the light pulse to be measured is constructed. i , i is the serial number of the light pulse.

[0081] The PIC analysis method is used to calculate the approximate period value T' of the unknown optical pulse.

[0082] like Figure 6 As shown in the figure, during the measurement time, the timer collects the absolute time of the output signal of the single-photon detector Si-SPAD, such as T1~T5 in the figure, and then calculates the time interval between adjacent output signals, such as ∆T in the figure. 12 ~∆T 45 , the distribution of these time intervals is counted, and the time interval value T' corresponding to the peak value is approximately equal to the period T of the light pulse to be measured. The computer program identifies the moment belonging to T', such as Figure 6 Then, take T1 as the starting time and T' as the period to construct the synchronization signal sync of the optical pulse. i .

[0083] Step S4202: Synchronization signal sync based on the optical pulse to be measured i The TCSPC analysis method is used to calculate each detection signal and the corresponding synchronization signal sync i The time interval ∆t i , based on all time intervals ∆t i The distribution of the count peak envelope in the histogram is obtained, the pulse width of the count peak envelope in the histogram is the light pulse width of the light to be measured, and the envelope peak value in the histogram is the time interval T' between adjacent output signals. Based on the histogram, the photon count N in the count peak envelope is obtained. pulse The total count outside the counting peak envelope is taken as the total count N. Based on the total count N, the photon number rate n of the continuous light part in the light to be measured is calculated according to formula (1): cw , according to formula (2), the optical power P is calculated cw , based on the time interval T' of adjacent output signals and the photon count N within the count peak envelope pulse According to formula (3), the average number of photons in the single pulse of the measured light is calculated, and according to formula (4), the energy of the single pulse is calculated. p .

[0084] The TCSPC analysis method is used to calculate the light information to be measured.

[0085] like Figure 7 As shown, the synchronization signal sync based on the light pulse to be measured i , calculate the time interval ∆t between each detection signal and the synchronization signal i , as shown in the figure ∆t1~∆t4, and then the distribution of these time intervals is counted to obtain a histogram. The pulse width of the count peak envelope in the histogram is the width of the light pulse, and the total number of light pulses in the measurement time = T meas / T', the photon count within the counting peak envelope is N pulse The background of the histogram, that is, the total counts outside the count peak envelope, is N.

[0086] According to formula (1) and formula (2), the optical power P of the continuous light part of the light to be measured is calculated: cw and the photon number rate n cw。

[0087] The average number of photons per pulse μ and the energy of a single pulse E p The calculation formula is: ; In formula (3), μ is the average number of photons in a single pulse, N pulse is the photon count within the peak envelope.

[0088] ; In formula (4), E p is the single pulse energy.

[0089] Step S4203: Obtain a preset search range ∆T and step size, and within the range of the time interval T'±∆T of adjacent output signals, traverse the search based on the step size to obtain the time interval T' of the corresponding adjacent output signals with the smallest pulse width, and correspondingly obtain the most matching optical pulse period, and then calculate and obtain the optical pulse repetition frequency, optical pulse width, single pulse average photon number μ and single pulse energy E p If the light to be measured contains a continuous light part, calculate the power P of the continuous light cw and the photon number rate n cw . Execute step S52.

[0090] Due to the measurement error, there is an error between the time interval T' of adjacent output signals and the true optical pulse period T. Therefore, the value closest to the true value T is searched within the range of T'±∆T. In the embodiment, the timer resolution is 16ps, and the search range ∆T=100ns is set, with a step size of 1ps. By replacing the time interval T' values ​​of different adjacent output signals and substituting them into step S4202, the optical pulse width is calculated, and the time interval T' of the corresponding adjacent output signals that minimizes the pulse width is found, thereby determining the true pulse period. Finally, the optical pulse repetition frequency 1 / T', optical pulse width, average number of photons per pulse μ, and single pulse energy E are calculated using the time interval T' value of the adjacent output signal that best matches. p If the light to be measured contains a continuous light part, calculate the power P of the continuous light cw and the photon number rate n cw。

[0091] Step S5: Determine whether it is in the linear detection range of the single photon detector Si-SPAD.

[0092] Step S5 includes step S51 and step S52.

[0093] Step S51: When step S1 selects continuous light, when 1kcps≤N / T meas ≤10Mcps, β≤1.2, it is known that it is in the linear detection range of the single-photon detector Si-SPAD, and step S6 is executed; when N / T meas When >10Mcps, it is known that the linear detection range of the single-photon detector Si-SPAD is exceeded, and the number of the wheel hole is increased by one to further increase the attenuation value; when N / T meas When <1kcps, it is known that the counting rate is too close to the noise floor of the single-photon detector Si-SPAD, and the serial number of the wheel hole is reduced by one to further reduce the attenuation value; the updated serial number of the wheel hole and the attenuation value of the variable attenuator are obtained and sent to the controller, and step S2201 is executed.

[0094] Step S52: When step S1 selects pulse light or unknown, when 0.0001≤T'·N pulse / T meas ≤0.1, it is known that it is in the linear detection range of the single-photon detector Si-SPAD, and step S6 is executed; when T'·N pulse / T meas >0.1, it is known that the linear detection range of the single-photon detector Si-SPAD is exceeded, and the number of the wheel hole is increased by one to further increase the attenuation; when T'·N pulse / T meas<0.0001, it is known that the counting rate is too close to the noise floor of the single-photon detector Si-SPAD, and the serial number of the wheel hole is reduced by one to further reduce the attenuation value; the updated serial number of the wheel hole and the attenuation value of the variable attenuator are obtained and sent to the controller, and step S2202 is executed.

[0095] According to the measurement results, adjust the attenuation value of the variable attenuator. If the measurement result shows that it exceeds the linear detection range of the single-photon detector Si-SPAD, and the current attenuation value is not the maximum value, increase the attenuation by one level and perform the next measurement; if the measurement result is close to the noise floor of the single-photon detector Si-SPAD, and the current attenuation value is not the minimum value, reduce the attenuation by one level and perform the next measurement.

[0096] Step S6: When step S5 determines that the light is in the linear detection range, output the measurement result of the light to be measured.

[0097] For continuous light, the output optical power P cw and the photon number rate n cw ; For pulsed light, output single pulse energy E p , the average number of photons per pulse μ, the optical pulse repetition frequency, and the optical pulse width; for a mixture of pulsed and continuous light, the above parameters of the continuous light and the pulsed light are obtained at the same time. When step S5 determines that the linear detection range is exceeded and the attenuation value of the variable attenuator has been adjusted to the maximum, a saturation warning is output.

Claims

1. A method for measuring light, characterized in that: The following steps are included: Step S1: Obtaining a preset measurement time length T meas and the wavelength λ of the light to be measured, to obtain the predicted optical power of the continuous light to be measured or the predicted energy of the optical pulse to be measured; Step S21: Based on the obtained predicted optical power or predicted energy, the initial attenuation value of the variable attenuator and the serial number of the rotary hole are obtained according to a relationship table of the predicted optical power, the predicted energy, the initial attenuation value and the serial number of the rotary hole; Step S22: controlling the stepper motor to rotate according to the sequence number of the wheel hole until the corresponding wheel hole is located on the optical path, so that the variable attenuator works at the set attenuation value, and obtaining the total transmittance of the variable attenuator according to the relationship table of the wheel hole sequence number, attenuation value and transmittance based on the sequence number of the wheel hole; Detection steps: when obtaining optical power, controlling the data acquisition unit to work in a counter mode to obtain continuous light parameters; when obtaining energy, controlling the data acquisition unit to work in a timer mode to obtain pulse light parameters when the light to be measured is pulse light; and obtaining continuous light parameters and pulse light parameters when the light to be measured is a mixture of pulse and continuous light; Determining step: whether it is in the linear detection range of the single photon detector. If it is not in the linear detection range of the single photon detector, adjust the attenuation value accordingly and then detect again, and execute step S22 until it is in the linear detection range of the single photon detector; Step S6: Obtain the measurement result of the light to be measured.

2. A method for measuring light according to claim 1, characterized in that: The detection step is specifically divided into step S31, step S41, step S32, step S4201 and step S4202, and the determination step is specifically divided into step S51 and step S52. In step S22, when obtaining optical power, step S31, step S41 and step S51 are executed, and when obtaining energy, step S32, step S4201, step S4202 and step S52 are executed; step S31: control the data acquisition unit to work in counter mode, accumulate all signals output by the single-photon detector within the measurement time, and obtain a total value N of the measurement; Step S41: Calculate the photon rate n of the continuous light to be measured according to formula (1): cw , according to formula (2), the optical power P is calculated cw , execute step S51; ； In formula (1), n cw is the photon rate of the light to be measured, unit s -1 ; T meas To measure the length of time, in seconds, P dark is the dark count rate of the single-photon detector, in cps; η is the detection efficiency of the single-photon detector, α is the total transmittance of the variable attenuator, and β is the linear fitting coefficient of the current count value of the single-photon detector; ； In formula (2), P cw is the optical power, in W; h is Planck's constant, h=6.6260693×10 -34 J·s; c is the speed of light, c=299792458m / s; λ is the wavelength of the light to be measured, in m; Step S51: When 1kcps≤N / T meas ≤10Mcps and β≤1.2, it is known that it is in the linear detection range of the single-photon detector, and step S6 is executed; when N / T meas When >10Mcps, it is known that the linear detection range of the single-photon detector is exceeded, and the number of the wheel hole is increased by one; when N / T meas When the count rate is <1 kcps, it is known that the count rate is too close to the noise floor of the single-photon detector, and the sequence number of the wheel hole is reduced by one; the updated sequence number of the wheel hole is obtained, and step S22 is executed; Step S32: Control the data acquisition unit to work in a timer mode, record the occurrence time of all single-photon detector output signals within the measurement time, and obtain the time data of the single-photon detector output signals; Step S4201: Based on the time data of the single-photon detector output signal, the total number of light pulses within the measurement time and the time interval T' between adjacent output signals are calculated using the PIC analysis method, and the time interval T' between adjacent output signals is used as the period T of the light pulse to be measured. Based on the time data of the single-photon detector output signal and the time interval T' between adjacent output signals, a synchronization signal sync of the light pulse to be measured is constructed. i , i is the serial number of the light pulse; Step S4202: Synchronization signal sync based on the optical pulse to be measured i The TCSPC analysis method is used to calculate each detection signal and the corresponding synchronization signal sync i The time interval ∆t i , based on all time intervals ∆t i The distribution of the count peak envelope in the histogram is obtained, and the pulse width of the count peak envelope in the histogram is the light pulse width of the light to be measured. Based on the histogram, the photon count N in the count peak envelope is obtained. pulse The total count outside the counting peak envelope is taken as the total count N. The average photon number μ of a single pulse in the light to be measured is calculated according to formula (3). The energy of a single pulse E is calculated according to formula (4). p ; Single pulse average photon number μ and single pulse energy E p The calculation formula is: ； In formula (3), μ is the average number of photons in a single pulse, N pulse is the photon count within the counting peak envelope; ； In formula (4), E p is the single pulse energy; Step S52: when 0.0001≤T'·N pulse / T meas ≤0.1, it is known that it is in the linear detection range of the single-photon detector, and step S6 is executed; when T'·N pulse / T meas When >0.1, it is known that the linear detection range of the single-photon detector is exceeded, and the serial number of the wheel hole is increased by one; When T'·N pulse / T meas <0.0001, it is known that the counting rate is too close to the noise floor of the single-photon detector, and the serial number of the wheel hole is reduced by one; the updated serial number of the wheel hole is obtained, and step S22 is executed.

3. A method for measuring light according to claim 1, characterized in that: In the step S1, the basic characteristics of the selected light to be measured are obtained. When the basic characteristics of the light to be measured are continuous light, the predicted optical power of the continuous light to be measured is obtained; when the basic characteristics of the light to be measured are pulsed light or unknown, the predicted energy of the light pulse to be measured is obtained; the measurement time length T meas , the range is 1ms~100s; select from the following options to obtain the predicted optical power of the continuous light to be measured: P1: ≤100fw; P2: 100fw~10pw; P3: 10pw~1nW; P4: 1nW~100nW; P5: 100nW~10μW; P6: 10μW~10mW; P7: unknown; Select from the following options to obtain the predicted energy of the optical pulse to be measured: E1: ≤ 10 -4 fJ; E2: 10 -4 fJ~10 -2 fJ; E3: 10 -2 fJ~1 fJ; E4: 1 fJ~100 fJ; E5: 100 fJ~10 pJ; E6: 100 fJ~1 nJ; E7: Unknown.

4. A method for measuring light according to claim 2, characterized in that: In step S4202, the envelope peak value in the histogram is the time interval T' between adjacent output signals; in step S4202, the photon number rate n of the continuous light part in the light to be measured is calculated according to formula (1): cw , according to formula (2), the optical power P is calculated cw。 5. A method for measuring light according to claim 2, characterized in that: The detection step further includes a step S4203 after the step S4202, wherein the step S4203: obtaining a preset search range ∆T and a step length, and obtaining a corresponding time interval T′ of adjacent output signals with a minimum pulse width based on a step length traversal search within the range of the time interval T′±∆T of adjacent output signals, and correspondingly obtaining the most matching optical pulse period, and then calculating and obtaining the optical pulse repetition frequency, optical pulse width, single pulse average photon number μ and single pulse energy E p .

6. A method for measuring light according to claim 5, characterized in that: In step S4203, the search range ∆T is set to 100ns and the step length is 1ps; if the light to be measured contains a continuous light part, the power P of the continuous light is calculated. cw and the photon number rate n cw。 7. A method for measuring light according to claim 2, characterized in that: In step S6, when the light is continuous, the continuous light parameters include the optical power P cw and the photon number rate n cw When it is pulse light, the pulse light parameters include single pulse energy E p , the average number of photons per pulse μ, the light pulse repetition frequency and the light pulse width; when it is a mixture of pulsed and continuous light, the continuous light parameters and the pulsed light parameters are obtained; when the step S51 or the step S52 is judged to exceed the linear detection range and the attenuation value of the variable attenuator has been adjusted to the maximum, a saturation warning is obtained.

8. A light measuring device, used in a light measuring method according to any one of claims 1 to 7, characterized in that: The invention comprises a variable attenuator, a single photon detector, a data acquisition unit, a controller and a computer. The variable attenuator, the single photon detector, the data acquisition unit and the controller form a measuring unit. The variable attenuator is used to be connected to the light to be measured. The variable attenuator is connected to the single photon detector. The single photon detector is electrically connected to the data acquisition unit. The data acquisition unit is electrically connected to the controller. The controller is electrically connected to the computer. The controller is electrically connected to the control port of the variable attenuator.

9. A light measuring device according to claim 8, characterized in that: The variable attenuator comprises a housing (11), a motor-side control port fixed on the housing (11), an input optical fiber interface (6) and an output optical fiber interface (7), a variable attenuator drive unit fixed in the housing (11), a stepper motor, a concave reflector (4), a reflector fixing frame (5), an optical fiber fixing frame (10), an input optical fiber (8) and an output optical fiber (9), and an optical attenuation plate rotating wheel (1) located in the housing (11); the variable attenuator drive unit, the stepper motor, the reflector fixing frame (5) and the optical fiber fixing frame (10) are all fixedly connected to the housing (11); the concave reflector (4) is fixedly connected to the reflector fixing frame (5); the input optical fiber (8) and the output optical fiber (9) are both fixedly connected to the optical fiber fixing frame (10); the optical attenuation plate rotating wheel (1) is fixedly connected to the rotating shaft of the stepper motor; a plurality of optical attenuation plates are arranged on the optical attenuation plate rotating wheel (1); one end of the input optical fiber (8) is connected to the input optical fiber interface (6); The optical fiber (8) is connected to the output optical fiber interface (7), and the other end of the output optical fiber (9) is the light entrance; the light exit of the input optical fiber (8) and the light entrance of the output optical fiber (9) are located on the same side of the light attenuation plate of the light attenuation plate rotating wheel (1), the concave reflector (4) is located on the other side of the light attenuation plate of the light attenuation plate rotating wheel (1), the light exit of the input optical fiber (8) is located on one side of the normal line of the concave reflector (4), and the light entrance of the output optical fiber (9) is located on the other side of the normal line of the concave reflector (4); the input optical fiber (8) is used to connect the light to be measured, the output optical fiber interface (7) of the variable attenuator is connected to the input end of the single photon detector through the output optical fiber (9), the control end of the controller is connected to the motor side control port of the variable attenuator, the motor side control port is electrically connected to the control end of the variable attenuator driving unit, and the output end of the variable attenuator driving unit is electrically connected to the stepping motor.

10. A light measuring device according to claim 9, characterized in that: The light attenuation sheet rotating wheel (1) is provided with a total of six rotating wheel holes, namely the first to sixth rotating wheel holes, which are evenly distributed on the light attenuation sheet rotating wheel (1); no light attenuation sheet is fixed on the first rotating wheel hole (2-1); a first light attenuation sheet is snap-fastened and fixed on the second rotating wheel hole (2-2) to form a first group of light attenuation sheets; a first light attenuation sheet and a second light attenuation sheet are snap-fastened and fixed on the third rotating wheel hole (2-3) to form a second group of light attenuation sheets; a first light attenuation sheet and a third light attenuation sheet are snap-fastened and fixed on the fourth rotating wheel hole (2-4) to form a third group of light attenuation sheets; a first light attenuation sheet and a fourth light attenuation sheet are snap-fastened and fixed on the fifth rotating wheel hole (2-5) to form a fourth group of light attenuation sheets; and two first light attenuation sheets and a fourth light attenuation sheet are snap-fastened and fixed on the sixth rotating wheel hole (2-6) to form a fifth group of light attenuation sheets.

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