A method and device for measuring light

Abstract

The present invention discloses a method and device for light measurement, relating to the technical field of optical systems; the method includes step S1: obtaining a preset measurement 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 rotating wheel hole of the variable optical attenuator according to the relation table; step S22: controlling the attenuation value of the variable optical attenuator according to the serial number of the rotating wheel hole; detection step: working in the counter mode when obtaining the optical power, and working in the timer mode when obtaining the energy; determination step: when not in the linear detection range of the single-photon detector, correspondingly adjusting the attenuation value and then executing step S22 until in the linear detection range; step S6: obtaining the measurement result of the light to be measured; the device includes a variable optical attenuator, a single-photon detector, a data acquisition unit, a controller and a computer, and correspondingly adjusting the attenuation value of the variable optical attenuator as needed, improving the measurement work efficiency.

Description

Technical Field

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

[0002] Optical power meters and optical energy meters are instruments for measuring light intensity. Among them, an optical power meter measures the average power of light, while an energy meter measures 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:

[0004] Since the optical attenuation value of the attenuator used in the current measurement cannot be adjusted and changed, the applicability is poor; replacing the attenuator with different optical attenuation values results in low measurement work efficiency.

[0005] Since the optical path structure of the wide-spectrum achromatic fiber coupling is relatively complex, the cost performance is poor. Summary of the Invention

[0006] The present invention provides a method and device for measuring light, which solves the technical problem of low measurement work efficiency.

[0007] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0008] A method for measuring light includes the following steps:

[0009] Step S1: Obtain a preset measurement time length T meas and the wavelength λ of the light to be measured, and obtain the predicted optical power of the continuous light to be measured or the predicted energy of the light pulse to be measured;

[0010] 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 rotating wheel hole according to the relationship table of the predicted optical power, predicted energy, initial attenuation value and serial number of the rotating wheel hole;

[0011] Step S22: Control the stepping motor to rotate according to the serial number of the rotating wheel hole until the corresponding rotating wheel hole is on the optical path, so that the variable attenuator works with a set attenuation value, and obtain the total transmittance of the variable attenuator according to the relationship table of the serial number of the rotating wheel hole, attenuation value and transmittance;

[0012] Detection step: When obtaining the optical power, control the data acquisition unit to work in the counter mode to obtain continuous light parameters. When obtaining the energy, control the data acquisition unit to work in the timer mode. When the light to be measured is a pulsed light, obtain pulsed light parameters. When the light to be measured is a mixed light of pulsed and continuous light, obtain continuous light parameters and pulsed light parameters;

[0013] Determination step: Check if it is within the linear detection range of the single-photon detector. When it is not within the linear detection range of the single-photon detector, adjust the attenuation value accordingly and then detect again. Execute step S22 until it is within the linear detection range of the single-photon detector;

[0014] Step S6: Obtain the measurement result of the light to be measured.

[0015] 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 the optical power, execute step S31, step S41, and step S51; when obtaining the energy, execute step S32, step S4201, step S4202, and step S52;

[0016] Step S31: Control the data acquisition unit to work in counter mode, accumulate all the signals output by the single-photon detector within the measurement time, and obtain the total measured value N; Step S41: Calculate the photon number rate n of the continuous light to be measured according to Equation (1) cw , and calculate the optical power P according to Equation (2) cw , and execute step S51;

[0017] ;

[0018] In Equation (1), n cw is the photon number rate of the light to be measured, with the unit s -1 ; T meas is the measurement time length, with the unit s, P dark is the dark count rate of the single-photon detector, with the unit 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; ;

[0019] In Equation (2), P cw is the optical power, with the unit W; h is Planck's constant, h = 6.6260693×10 -34 J·s; c is the speed of light, c = 299792458 m / s; λ is the wavelength of the light to be measured, with the unit m;

[0020] Step S51: When 1 kcps ≤ N / T meas ≤ 10 Mcps and β ≤ 1.2, it is known that it is within the linear detection range of the single-photon detector, and execute step S6; when N / T meas > 10 Mcps, it is known that it exceeds the linear detection range of the single-photon detector, and increment the serial number of the wheel hole; when N / Tmeas When the count rate is too close to the noise floor of the single-photon detector at 1 kcps, decrement the serial number of the wheel hole by one; obtain the updated serial number of the wheel hole, and execute step S22;

[0021] Step S32: Control the data acquisition unit to work in timer mode, record the occurrence times of all output signals of the single-photon detector during the measurement time, and obtain the time data of the output signals of the single-photon detector; Step S4201: Use the PIC analysis method to calculate the total number of optical pulses and the time interval T' between adjacent output signals during the measurement time based on the time data of the output signals of the single-photon detector, take the time interval T' between adjacent output signals as the period T of the optical pulse to be measured, and construct the synchronization signal sync of the optical pulse to be measured based on the time data of the output signals of the single-photon detector and the time interval T' between adjacent output signals i , where i is the serial number of the optical pulse;

[0022] Step S4202: Based on the synchronization signal sync of the optical pulse to be measured i Use the TCSPC analysis method to calculate the time interval ∆t between each detection signal and the corresponding synchronization signal sync i ; based on the distribution of all time intervals ∆t i obtain a histogram, the pulse width of the pulse envelope of the count peak in the histogram is the optical pulse width of the optical pulse to be measured, obtain the photon count N within the pulse envelope of the count peak based on the histogram i and the total count outside the pulse envelope of the count peak, take the total count outside the pulse envelope of the count peak as the calculated total count N, calculate the average number of photons per single pulse μ in the optical pulse to be measured according to formula (3), and calculate the single-pulse energy E according to formula (4) pulse ; p ;

[0023] The average number of photons per single pulse μ and the single-pulse energy E p are calculated by the following formulas:

[0024] ;

[0025] In formula (3), μ is the average number of photons per single pulse, and N pulse is the photon count within the pulse envelope of the count peak;

[0026] ;

[0027] In formula (4), E p is the single-pulse energy;

[0028] Step S52: When 0.0001 ≤ T'·N pulse / T measWhen it is ≤ 0.1, it is known that it is within 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 it exceeds the linear detection range of the single-photon detector, and the serial number of the runner hole is incremented by one; when T’·N pulse / T meas < 0.0001, it is known that the counting rate is too close to the noise background of the single-photon detector, and the serial number of the runner hole is decremented by one; the updated serial number of the runner hole is obtained, and step S22 is executed.

[0029] A further technical solution lies in: in step S1, the basic characteristics of the to-be-detected light selected are obtained. When the basic characteristics of the to-be-detected light are continuous light, the predicted optical power of the to-be-detected continuous light is obtained; when the basic characteristics of the to-be-detected light are pulsed light or unknown, the predicted energy of the to-be-detected light pulse is obtained; the measurement time length T meas , with a range of 1 ms to 100 s; select from the following options to obtain the predicted optical power of the to-be-detected continuous light:

[0030] P1: ≤ 100 fw;

[0031] P2: 100 fw to 10 pw;

[0032] P3: 10 pw to 1 nW;

[0033] P4: 1 nW to 100 nW;

[0034] P5: 100 nW to 10 μW;

[0035] P6: 10 μW to 10 mW;

[0036] P7: Unknown;

[0037] Select from the following options to obtain the predicted energy of the to-be-detected light pulse:

[0038] E1: ≤ 10 -4 fJ;

[0039] E2: 10 -4 fJ to 10 -2 fJ;

[0040] E3: 10 -2 fJ to 1 fJ;

[0041] E4: 1 fJ to 100 fJ;

[0042] E5: 100 fJ to 10 pJ;

[0043] E6: 100 fJ to 1 nJ;

[0044] E7: Unknown.

[0045] A further technical solution lies in that: in the step S4202, the envelope peak value in the histogram is the time interval T' between adjacent output signals; in the 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 , and the optical power P is calculated according to formula (2). cw .

[0046] A further technical solution lies in that: the detection step further includes a step S4203 after the step S4202. Step S4203: Obtain a preset search range ∆T and a step size. Within the range of the time interval T' ± ∆T of adjacent output signals, traverse and search based on the step size to obtain the time interval T′ of the corresponding adjacent output signal with the minimum pulse width, and correspondingly obtain the most matching optical pulse period, and then calculate the optical pulse repetition frequency, optical pulse width, average number of photons μ per single pulse, and single pulse energy E. p .

[0047] A further technical solution lies in that: in the step S4203, set the search range ∆T = 100 ns and the step size to 1 ps; 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 .

[0048] A further technical solution lies in that: in the step S6, when it is continuous light, the obtained continuous light parameters include the optical power P cw and the photon number rate n cw ; when it is pulsed light, the obtained pulsed light parameters include the single pulse energy E p , the average number of photons μ per single pulse, the optical pulse repetition frequency, and the optical pulse width; when it is a mixture of pulsed and continuous light, obtain the continuous light parameters and the pulsed light parameters; when the step S51 or step S52 determines that it exceeds the linear detection range and the attenuation value of the variable attenuator has been adjusted to the maximum, a saturation warning is obtained.

[0049] An optical measurement device for the optical measurement method described in any one of the above, including 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 measurement 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. The controller is electrically connected to the control port of the variable attenuator.

[0050] A further technical solution lies in that: the variable optical attenuator includes a box body, a motor-side control port fixed on the box body, an input optical fiber interface and an output optical fiber interface, a variable optical attenuator driving unit fixed inside the box body, a stepping motor, a concave mirror, a mirror fixing bracket, an optical fiber fixing bracket, an input optical fiber and an output optical fiber, and a light attenuation sheet runner located inside the box body. The variable optical attenuator driving unit, the stepping motor, the mirror fixing bracket and the optical fiber fixing bracket are all fixedly connected to the box body. The concave mirror is fixedly connected to the mirror fixing bracket. The input optical fiber and the output optical fiber are both fixedly connected to the optical fiber fixing bracket. The light attenuation sheet runner is fixedly connected to the rotating shaft of the stepping motor. A plurality of light attenuation sheets are arranged on the light attenuation sheet runner. 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 the light output port. 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 the light input port. The light output port of the input optical fiber and the light input port of the output optical fiber are on the same side of the light attenuation sheets of the light attenuation sheet runner. The concave mirror is on the other side of the light attenuation sheets of the light attenuation sheet runner. The light output port of the input optical fiber is on one side of the normal line of the concave mirror, and the light input port of the output optical fiber is on the other side of the normal line of the concave mirror. The input optical fiber is used to connect the optical signal to be measured. The output optical fiber interface of the variable optical 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 optical attenuator. The motor-side control port is electrically connected to the control end of the variable optical attenuator driving unit. The output end of the variable optical attenuator driving unit is electrically connected to the stepping motor.

[0051] A further technical solution lies in that: six runner holes, namely the first to the sixth runner holes, are opened on the light attenuation sheet runner. The six runner holes are evenly distributed on the light attenuation sheet runner. No light attenuation sheet is fixed in the first runner hole. A first light attenuation sheet is clamped and fixed in the second runner 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 in the third runner 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 in the fourth runner 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 in the fifth runner hole to form a fourth group of light attenuation sheets. Two first light attenuation sheets and a fourth light attenuation sheet are clamped and fixed in the sixth runner hole to form a fifth group of light attenuation sheets.

[0052] The beneficial effects produced by adopting the above technical solutions are as follows:

[0053] First, a method for measuring light includes the following steps: Step S1: Obtain 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 optical attenuator and the serial number of the rotating wheel hole according to the relationship table of the predicted optical power, predicted energy, initial attenuation value, and rotating wheel hole serial number; Step S22: Control the stepper motor to rotate until the corresponding rotating wheel hole is on the optical path according to the serial number of the rotating wheel hole, so that the variable optical attenuator works with a set attenuation value, and obtain the total transmittance of the variable optical attenuator based on the serial number of the rotating wheel hole according to the relationship table of the rotating wheel hole serial number, attenuation value, and transmittance; Detection step: When obtaining the optical power, control the data acquisition unit to work in the counter mode to obtain continuous light parameters. When obtaining the energy, control the data acquisition unit to work in the timer mode. When the light to be measured is a pulsed light, obtain pulsed light parameters. When the light to be measured is a mixed light of pulse and continuous, obtain continuous light parameters and pulsed light parameters; Judgment step: Whether it is within the linear detection range of the single-photon detector. When it is not within 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 within the linear detection range of the single-photon detector; Step S6: Obtain the measurement result of the light to be measured. Adjust the attenuation value of the variable optical attenuator as needed, which improves the measurement work efficiency.

[0054] Second, an optical measurement device for the optical measurement method according to any one of the above, including a variable optical attenuator, a single-photon detector, a data acquisition unit, a controller, and a computer. The variable optical attenuator, the single-photon detector, the data acquisition unit, and the controller form a measurement unit. The variable optical attenuator is used to connect to the light to be measured. The variable optical 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 optical attenuator. Adjust the attenuation value of the variable optical attenuator as needed, which improves the measurement work efficiency.

[0055] Third, during measurement, there is always a rotating wheel hole on the optical path. When the attenuation value needs to be adjusted, the optical attenuation film rotating wheel is driven by a stepper motor to rotate, and it can be switched to any set attenuation value, thereby realizing a large-range optical attenuation adjustment. Since the optical attenuation film of each rotating wheel hole is fixed, each adjustment is only a switch between these fixed attenuation films, and extremely high repeatability can be obtained.

[0056] Fourth, compared with the traditional transmissive lens, the concave mirror can achieve achromatic fiber coupling in a wide spectrum with only one device, and has a good cost performance.

[0057] See the description in the specific implementation part for details. Brief Description of the Drawings

[0058] Figure 1 is the principle block diagram of the present invention;

[0059] Figure 2-1 It is the structural diagram of a variable optical attenuator;

[0060] Figure 2-2 is Figure 2-1 the structural diagram of the optical attenuation film rotating wheel in

[0061] Figure 2-3 It is the optical path distribution diagram of the variable optical attenuator;

[0062] Figure 3 It is the timing diagram of the data acquisition unit;

[0063] Figure 4 It is the structural diagram of the present invention;

[0064] Figure 5 It is the flowchart of Embodiment 3 of the present invention;

[0065] Figure 6 It is the screenshot of the timing data in the PIC analysis method;

[0066] Figure 7 It is the screenshot of the timing data in the TCSPC analysis method.

[0067] Wherein: 1 optical attenuation film rotating wheel, 2-1 first rotating wheel hole, 2-2 second rotating wheel hole, 2-3 third rotating wheel hole, 2-4 fourth rotating wheel hole, 2-5 fifth rotating wheel hole, 2-6 sixth rotating wheel hole, 3 closed-loop control stepping motor, 4 concave mirror, 5 mirror fixing bracket, 6 input optical fiber interface, 7 output optical fiber interface, 8 input optical fiber, 9 output optical fiber, 10 optical fiber fixing bracket, 11 box body, 12 optical attenuation film, 13 rotary variable optical attenuator, 14 silicon avalanche photodiode single photon detector, 15 FPGA board, 16 laptop computer, 17 cable, 18 data line, 19 rotating wheel motor control line, 20 optical to be measured. Specific embodiments

[0068] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0069] In the following description, numerous specific details are set forth to provide a thorough understanding of the present application. However, the present application may be practiced in other ways different from those described herein. Persons skilled in the art can make similar extensions without departing from the spirit of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0070] Embodiment 1:

[0071] As Figure 1 shown, the present invention discloses a measuring device for light, including a variable optical attenuator, a single-photon detector, a data acquisition unit, a controller, a USB3.0 interface, a control port on the controller side, a computer, and a program module. The variable optical attenuator, the single-photon detector, the data acquisition unit, and the controller form a measuring unit.

[0072] As Figure 2-1 shown, the variable optical attenuator includes a box body 11, a control port on the motor side fixed to the box body 11, an input optical fiber interface 6 and an output optical fiber interface 7, a variable optical attenuator driving unit fixed inside the box body 11, a closed-loop controlled stepper motor 3, a concave mirror 4, a mirror fixing bracket 5, an optical fiber fixing bracket 10, an input optical fiber 8 and an output optical fiber 9, and a light attenuation sheet rotating wheel 1 located inside the box body 11. The variable optical attenuator driving unit, the closed-loop controlled stepper motor 3, the mirror fixing bracket 5, and the optical fiber fixing bracket 10 are all fixedly connected to the box body 11. The concave mirror 4 is fixedly connected to the mirror fixing bracket 5. The input optical fiber 8 and the output optical fiber 9 are both fixedly connected to the optical fiber fixing bracket 10. The light attenuation sheet rotating wheel 1 is fixedly connected to the rotating shaft of the closed-loop controlled stepper motor 3.

[0073] As Figure 2-2 shown, six rotating wheel holes, namely the first to the sixth rotating wheel holes, are formed on the light attenuation sheet rotating wheel 1. The six rotating wheel holes are evenly distributed on the light attenuation sheet rotating wheel 1. No light attenuation sheet is fixed in the first rotating wheel hole 2-1. A first light attenuation sheet is clamped and fixed in 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 clamped and fixed in 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 clamped and fixed in 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 clamped and fixed in the fifth rotating wheel hole 2-5 to form a fourth group of light attenuation sheets. Two first light attenuation sheets and a fourth light attenuation sheet are clamped and fixed in the sixth rotating wheel hole 2-6 to form a fifth group of light attenuation sheets.

[0074] The light attenuation sheets are installed in six installation holes in the rotating wheel device.

[0075] As shown in Table 1, four kinds of light attenuation sheets are selected in the present application.

[0076] Table 1: Parameter Table of Attenuation Plates

[0077] Attenuator Sheet Serial Number Type Operating Wavelength nm Diameter mm Attenuation dB ① Absorptive Type 300-1100 25 10 ② Reflective Type 350-1100 25 10 ③ Reflective Type 350-1100 25 20 ④ Reflective Type 350-1100 25 30

[0078] As shown in Table 2, 0 to 3 optical attenuation plates are selected for each hole to form six attenuation values.

[0079] Table 2: Relationship Table of Rotor Hole Serial Number, Attenuation Value and Transmittance

[0080] Rotary Hole Serial Number Combination Total Round-Trip Attenuation Value dB Total Round-Trip Transmittance 1 Empty 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 >

[0081] During measurement, there is always one rotor hole in the optical path to achieve the corresponding optical attenuation. When the attenuation value needs to be adjusted, the optical attenuation plate rotor 1 is driven by a stepper motor to rotate. Every time it rotates 60 degrees, it can switch to a nearby hole. According to the current attenuation value, that is, the current rotational angle position of the stepper motor, by adjusting the rotational angle, it can switch to any set attenuation value. It can achieve a wide range of optical attenuation adjustment, and since the optical attenuation plates for each hole are fixed, each adjustment is just a switch between these fixed attenuation plates, and extremely high repeatability can be obtained.

[0082] As Figure 2-1 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 output port. 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 input port.

[0083] As Figure 2-3 shown, the light output port of the input optical fiber 8 and the light input port of the output optical fiber 9 are on the same side of the optical attenuation plate 12 of the optical attenuation plate rotor 1. The concave mirror 4 is on the other side of the optical attenuation plate 12 of the optical attenuation plate rotor 1. The light output port of the input optical fiber 8 is on one side of the normal line of the concave mirror 4, and the light input port of the output optical fiber 9 is on the other side of the normal line of the concave mirror 4.

[0084] As Figure 1 shown, the light to be measured is connected to the input optical fiber interface of the variable optical attenuator through the input optical fiber. The output optical fiber interface of the variable optical attenuator is connected to the input end of the single-photon detector through the output optical fiber. The output end of the single-photon detector is electrically connected to the input end of the data acquisition unit through a 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 a data cable. The control end of the controller is electrically connected to the control port on the controller side. The control port on the controller side is electrically connected to the control port on the motor side of the variable optical attenuator through a control line. The control port on the motor side is electrically connected to the control end of the variable optical attenuator drive unit. The output end of the variable optical attenuator drive unit is electrically connected to the stepper motor.

[0085] The variable optical attenuator is described in detail as follows.

[0086] As Figure 2-1 shown, for 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.

[0087] As Figure 2-3 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 light output from the light output port of the input optical fiber 8 propagates in a gradually diverging state, passes through the optical attenuation sheet 12 and irradiates the concave mirror 4. After reflection, this beam of light starts to propagate in a gradually converging state, then passes through the optical attenuation sheet again, and finally converges to the light input port of the output optical fiber 9. The light output port of the input optical fiber 8 and the light input port of the output optical fiber 9 are on both sides of the optical axis of the concave mirror 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 mirror 4 is coated with a silver film and has a focal length f = 38.1 mm; the distances from the light output port of the input optical fiber 8 and the light input port of the output optical fiber 9 to the front surface of the center of the concave mirror 4 are both 76.2 mm. The fiber-concave mirror-fiber forms an imaging structure with object distance and image distance both being 2f. Compared with the traditional transmissive lens, the concave mirror 4 can achieve wide-spectrum achromatic aberration fiber coupling with only one device.

[0088] The single-photon detector is a silicon avalanche photodiode single-photon detector Si-SPAD, which is described in detail as follows.

[0089] A single-photon detector is a photodetector that can detect single photons. Photons are the basic energy units of light. When a single-photon detector detects a photon, it will output in the form of an electrical pulse. The Si-SPAD operates in the continuous detection mode, with a wavelength response range of 400 nm to 1100 nm, a peak wavelength detection efficiency of ~65%, a dark count rate of ~200 cps (i.e., counts per second), a saturation count rate of ~15 Mcps, and when the maximum linear detection count rate ≤ 10 Mcps, the non-linear fitting coefficient β ≤ 1.2.

[0090] The data acquisition unit and controller based on the FPGA board 15 are described in detail as follows.

[0091] The controller is an xc7A-75T chip, and the data acquisition unit supports two working modes: counter mode and timer mode.

[0092] As Figure 3 shown, 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 measured total value N is obtained. The timer mode is to record the moments of all the signals output by the single-photon detector SPAD starting from the measurement start moment within the measurement time, and finally output these moment information T 1, T 2 , …,T n 。

[0093] As Figure 1 shown, the controller is responsible for communicating with the computer, uploading the collected data to the computer, and at the same time receiving the control instructions from the computer to adjust the working parameters of the counter or timer, or control the attenuation value of the variable attenuator.

[0094] The program module of the computer 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 mixed light of pulsed light and continuous light, the measurement results of both lights are output simultaneously.

[0095] As Figure 4 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 16; 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 by a cable 17 into the FPGA board 15, and the data collected by the FPGA board 15 is uploaded to the laptop 16 through a USB data cable 18. Control signal: The computer control instruction is downloaded to the FPGA board 15 through the USB data cable 18, and then the FPGA board 15 interprets the computer control instruction and transmits the control signal through the rotary motor control line 19 to control the motor.

[0096] A measuring device for light proposed in this application is an ultra-high-sensitivity optical power and energy meter USOM, and its features include:

[0097] (1) High sensitivity. Compared with the traditional optical power and energy meter with a photodiode probe, the sensitivity of this application is increased by about five orders of magnitude.

[0098] (2) It has the function of measuring the optical pulse width.

[0099] (3) It has the function of measuring unknown light that is a mixture of continuous light and pulsed light.

[0100] Embodiment 2:

[0101] AsFigure 5 As shown in Figure 5 , the present invention discloses a method for measuring light. Based on the light measuring device described in Embodiment 1, it includes the following steps:

[0102] Step S1: Obtain the input initial parameters.

[0103] The operator turns on the computer software and enters the initial parameters in the software interface, specifically as follows.

[0104] Step S11: The computer obtains the measurement time length T set by the operator meas , with a range of 1 ms to 100 s. The computer obtains the wavelength λ of the light to be measured set by the operator, with a range of 4×10 -7 to 1.1×10 -6 m.

[0105] Step S12: The operator selects one from the three options of continuous light, pulsed light, or unknown. 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.

[0106] 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, and selects from the following options:

[0107] P1: ≤100 fW;

[0108] P2: 100 fW to 10 pW;

[0109] P3: 10 pW to 1 nW;

[0110] P4: 1 nW to 100 nW;

[0111] P5: 100 nW to 10 μW;

[0112] P6: 10 μW to 10 mW;

[0113] P7: Unknown.

[0114] Step S1302: When the user selects 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, and selects from the following options:

[0115] E1: ≤ 10 -4 fJ;

[0116] E2: 10 -4 fJ to 10 -2 fJ;

[0117] E3: 10 -2 fJ to 1 fJ;

[0118] E4: 1 fJ to 100 fJ;

[0119] E5: 100 fJ to 10 pJ;

[0120] E6: 100 fJ to 1 nJ;

[0121] E7: Unknown.

[0122] Step S2: Obtain the attenuation value of the variable attenuator.

[0123] Step S2 includes Step S21 and Step S22.

[0124] Step S21: Based on the obtained predicted optical power or predicted energy, the computer obtains the initial attenuation value of the variable attenuator and the serial number of the rotary wheel hole according to the relationship table of predicted optical power, predicted energy, initial attenuation value and serial number of the rotary wheel hole, takes the initial attenuation value as the set attenuation value of the variable attenuator, sends the attenuation value and the serial number of the rotary wheel hole of the variable attenuator to the controller. When the controller obtains the attenuation value and the serial number of the rotary wheel hole of the variable attenuator, it executes Step S2101, Step S2201 and Step S31 when obtaining the predicted optical power, and executes Step S2102, Step S2202 and Step S32 when obtaining the predicted energy. Step S21 includes Step S2101 and Step S2102, which are described in detail as follows.

[0125] Step S2101: Based on the obtained predicted optical power, the computer obtains the initial attenuation value of the variable attenuator and the serial number of the rotary wheel hole according to the relationship table of predicted optical power, predicted energy, initial attenuation value and serial number of the rotary wheel hole, takes the initial attenuation value as the set attenuation value of the variable attenuator, sends the attenuation value and the serial number of the rotary wheel hole of the variable attenuator to the controller. When the controller obtains the attenuation value and the serial number of the rotary wheel hole of the variable attenuator, it executes Step S2201.

[0126] Step S2102: Based on the obtained predicted energy, the computer obtains the initial attenuation value of the variable attenuator and the serial number of the rotary wheel hole according to the relationship table of predicted optical power, predicted energy, initial attenuation value and serial number of the rotary wheel hole, takes the initial attenuation value as the set attenuation value of the variable attenuator, sends the attenuation value and the serial number of the rotary wheel hole of the variable attenuator to the controller. When the controller obtains the attenuation value and the serial number of the rotary wheel hole of the variable attenuator, it executes Step S2202.

[0127] Described in detail as follows.

[0128] At the initial setting, according to the parameters selected in step S1301 or step S1302, calculate and set an appropriate initial attenuation value. The specific parameters are shown in Table 3.

[0129] Table 3: Relationship table of predicted optical power, predicted energy, initial attenuation value, and wheel hole number

[0130] Step S1301 Step S1302 Initial Attenuation Value dB Rotary Hole Serial Number P1: ≤100 <![CDATA[E1: ≤10 -4 fJ > 0 1 P2: 100～10 <![CDATA[E2: 10 -4 fJ ~10 -2 fJ > 20 2 P3: 10～1 <![CDATA[E3: 10 -2 fJ ~1 fJ > 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

[0131] Step S22: The controller obtains the attenuation value of the updated variable optical attenuator and the number of the wheel hole. The controller controls the stepping motor to rotate according to the number of the wheel hole, so that the corresponding wheel hole is located on the optical path, so that the variable optical attenuator works at the set attenuation value. Based on the number of the wheel hole, obtain the total transmittance of the variable optical attenuator according to the relationship table of the number of the wheel hole, attenuation value, and transmittance. When obtaining the optical power, execute step S31; when obtaining the energy, execute step S32.

[0132] Step S22 includes step S2201 and step S2202, which are described in detail as follows.

[0133] Step S2201: The controller obtains the attenuation value of the updated variable optical attenuator and the number of the wheel hole. The controller controls the stepping motor to rotate according to the number of the wheel hole, so that the corresponding wheel hole is located on the optical path, so that the variable optical attenuator works at the set attenuation value. Based on the number of the wheel hole, obtain the total transmittance of the variable optical attenuator according to the relationship table of the number of the wheel hole, attenuation value, and transmittance, and execute step S31.

[0134] Step S2202: The controller obtains the attenuation value of the updated variable optical attenuator and the number of the wheel hole. The controller controls the stepping motor to rotate according to the number of the wheel hole, so that the corresponding wheel hole is located on the optical path, so that the variable optical attenuator works at the set attenuation value. Based on the number of the wheel hole, obtain the total transmittance of the variable optical attenuator according to the relationship table of the number of the wheel hole, attenuation value, and transmittance, and execute step S32.

[0135] Step S3: Collect the detection signal in the counter mode or the timer mode.

[0136] The single-photon detector Si-SPAD detects the light to be measured and collects data.

[0137] Step S3 includes step S31 and step S32.

[0138] Step S31: When continuous light is selected in step S1, the controller controls the data acquisition unit to work in the counter mode, accumulates all the signals output by the single-photon detector Si-SPAD within the measurement time, and obtains a measured total count value N, and then execute step S41.

[0139] Step S32: When "pulsed light" or "unknown" is selected in Step S1, the controller controls the data acquisition unit to work in the timer mode, records the occurrence times of all output signals of the single-photon detector Si-SPAD during the measurement time, obtains the time data of the output signals of the single-photon detector Si-SPAD, and executes Step S42.

[0140] Step S4: Calculate the optical parameters in the counter mode or the timer mode.

[0141] Step S4 includes Step S41 and Step S42.

[0142] Step S41: Divide the total measured value N by the measurement time length T meas to obtain 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 count rate n of the continuous light to be measured based on the total measured value N and the attenuation value of the variable attenuator according to Equation (1) cw , calculate the optical power P according to Equation (2) cw , and execute Step S51.

[0143] When continuous light is selected in Step S1, calculate the photon count rate n of the light to be measured 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。

[0144] ;

[0145] In Equation (1), n cw is the photon count rate of the light to be measured, with the unit s -1 ; T meas is the measurement time length, with the unit s, P dark is the dark count rate of the single-photon detector Si-SPAD, with the unit 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.

[0146] According to the photon count rate n cw , calculate the optical power P cw .

[0147] ;

[0148] In Equation (2), P cw is the optical power, with the unit W; h is the Planck constant, h = 6.6260693×10 -34 J·s; c is the speed of light, c = 299792458 m / s; λ is the wavelength of the light to be measured, with the unit m.

[0149] Step S42: Calculate the pulsed light parameters based on the time data of the output signals of the single-photon detector Si-SPAD and the attenuation value of the variable optical attenuator. If the pulsed light contains a continuous light part, calculate its optical parameters simultaneously. Then execute Step S52.

[0150] Step S42 includes Step S4201, Step S4202, and Step S4203.

[0151] When Step S1 selects pulsed light or unknown, calculate the parameters of the pulsed light according to the collected time data, the performance parameters of the single-photon detector Si-SPAD, and the attenuation value of the variable optical attenuator. If the pulsed light contains a continuous light part, calculate its optical parameters simultaneously. The specific steps are as follows:

[0152] Step S4201: Use the PIC analysis method based on the time data of the output signals of the single-photon detector Si-SPAD to calculate the total number of optical pulses within the measurement time and the time interval T' between adjacent output signals. Take the time interval T' between adjacent output signals as the period T of the optical pulse to be measured. Based on the time data of the output signals of the single-photon detector Si-SPAD and the time interval T' between adjacent output signals, construct the synchronization signal sync of the optical pulse to be measured. i , where i is the serial number of the optical pulse.

[0153] Use the PIC analysis method to calculate the approximate period value T' of the unknown optical pulse.

[0154] As Figure 6 shown, within the measurement time, the timer collects the absolute time of the output signals of the single-photon detector Si-SPAD, such as T 1 ~T 5 , and then calculates the time interval between adjacent output signals, such as ∆T 12 ~∆T 45 . Statistically analyze the distribution of these time intervals. The time interval value T' corresponding to the peak is approximately equal to the period T of the optical pulse to be measured. The computer program identifies the times belonging to T', such as Figure 6 T 1 , T 2 , T 4 , T 5 . Then, taking T 1 as the starting time and T' as the period, construct the synchronization signal sync of the optical pulse i .

[0155] Step S4202: Use the TCSPC analysis method based on the synchronization signal sync of the optical pulse to be measured i to calculate the time difference between each detection signal and the corresponding synchronization signal synci The time interval ∆t i , based on all the time intervals ∆t i a histogram is obtained from the distribution. The pulse width of the peak envelope of the counts in the histogram is the optical pulse width of the light to be measured. The peak value of the envelope in the histogram is the time interval T’ between adjacent output signals. Based on the histogram, the photon count N within the peak envelope of the counts is obtained pulse and the total count outside the peak envelope of the counts. The total count outside the peak envelope of the counts is taken as the calculated 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 , and the optical power P is calculated according to formula (2) cw , based on the time interval T’ between adjacent output signals and the photon count N within the peak envelope of the counts pulse the average number of photons per single pulse μ in the light to be measured is calculated according to formula (3), and the single pulse energy E is calculated according to formula (4) p .

[0156] The information of the light to be measured is calculated by using the TCSPC analysis method

[0157] As Figure 7 shown, based on the synchronization signal sync of the light pulse to be measured i , the time interval ∆t between each detection signal and the synchronization signal is calculated i , such as ∆t 1 ~∆t 4 in the figure, and then the distribution of these time intervals is statistically analyzed to obtain a histogram. The pulse width of the peak envelope of the counts in the histogram is the width of the optical pulse, and the total number of optical pulses within the measurement time = T meas / T’, and the photon count within the peak envelope of the counts is N pulse , and the background of the histogram, i.e., the total count outside the peak envelope of the counts, is N

[0158] The optical power P and the photon number rate n of the continuous light part in the light to be measured are calculated according to formula (1) and formula (2) cw and cw。

[0159] The formulas for the average number of photons per single pulse μ and the single pulse energy E p are as follows

[0160] ;

[0161] In formula (3), μ is the average number of photons per single pulse, and N pulse is the photon count within the peak envelope of the counts

[0162] ;

[0163] In formula (4), Ep is the single - pulse energy.

[0164] Step S4203: Obtain a preset search range ∆T and step size. Within the time interval T’±∆T of adjacent output signals, traverse and search based on the step size to obtain the time interval T′ of the adjacent output signal with the minimum pulse width, thereby obtaining the most - matched optical pulse period, and then calculate the optical pulse repetition frequency, optical pulse width, average number of photons per single pulse μ, and single - pulse energy E. p If the measured light contains a continuous - light part, calculate the power P of the continuous light. cw and photon number rate n. cw Execute step S52.

[0165] Due to measurement errors, there is an error between the time interval T’ of adjacent output signals and the true optical pulse period T. Therefore, traverse and search within the range of T’±∆T to find the value closest to the true value T. In the embodiment, the timer resolution is 16 ps, the search range ∆T = 100 ns is set, and the step size is 1 ps. By substituting different values of the time interval T′ of adjacent output signals and substituting them into step S4202, calculate the optical pulse width, find the time interval T′ of the adjacent output signal corresponding to the minimum pulse width, thereby determining the true pulse period. Finally, use the value of the time interval T′ of the most - matched adjacent output signal to calculate the optical pulse repetition frequency 1 / T′, optical pulse width, average number of photons per single pulse μ, and single - pulse energy E. p If the measured light contains a continuous - light part, calculate the power P of the continuous light. cw and photon number rate n. cw。

[0166] Step S5: Determine whether it is within the linear detection range of the single - photon detector Si - SPAD.

[0167] Step S5 includes step S51 and step S52.

[0168] Step S51: When step S1 selects continuous light, when 1 kcps ≤ N / T meas ≤ 10 Mcps and β ≤ 1.2, it is known that it is within the linear detection range of the single - photon detector Si - SPAD, and execute step S6; when N / T meas > 10 Mcps, it is known that it exceeds the linear detection range of the single - photon detector Si - SPAD, increment the serial number of the wheel hole by one, and further increase the attenuation value; when N / T meas < 1 kcps, it is known that the counting rate is too close to the noise floor of the single - photon detector Si - SPAD, decrement the serial number of the wheel hole by one, and further decrease the attenuation value; obtain the updated serial number of the wheel hole and the attenuation value of the variable attenuator and send them to the controller, and execute step S2201.

[0169] Step S52: When it is selected in Step S1 that the light contains pulsed light or is unknown, and 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 it exceeds the linear detection range of the single-photon detector Si-SPAD, the serial number of the wheel hole is incremented by one, and the attenuation is further increased; when T’·N pulse / T meas < 0.0001, it is known that the count rate is too close to the noise background of the single-photon detector Si-SPAD, the serial number of the wheel hole is decremented by one, and the attenuation value is further decreased; the updated serial number of the wheel hole and the attenuation value of the variable optical attenuator are obtained and sent to the controller, and Step S2202 is executed.

[0170] Adjust the attenuation value of the variable optical attenuator according to the measurement result. 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 step and then perform the next measurement; if the measurement result is close to the noise background of the single-photon detector Si-SPAD and the current attenuation value is not the minimum value, decrease the attenuation by one step and then perform the next measurement.

[0171] Step S6: When it is judged in Step S5 that it is in the linear detection range, output the measurement result of the light to be measured.

[0172] For continuous light, output the optical power P cw and the photon number rate n cw ; for pulsed light-containing light, output the single-pulse energy E p , the average number of photons per single pulse μ, the optical pulse repetition frequency, the optical pulse width; for light that is a mixture of pulsed and continuous light, simultaneously obtain the above parameters of the continuous light and pulsed light therein. When it is judged in Step S5 that it exceeds the linear detection range and the attenuation value of the variable optical attenuator has been adjusted to the maximum, output a saturation warning.

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 step: when obtaining optical power, control the data acquisition unit to work in counter mode to obtain continuous light parameters; when obtaining energy, control the data acquisition unit to work in timer mode to obtain pulse light parameters when the light to be measured is pulse light; when the light to be measured is a mixture of pulse and continuous light, obtain continuous light parameters and pulse light parameters; the steps of working in the timer mode include step S32, step S4201 and step S4202, Step S32: Record the occurrence time of all single-photon detector output signals within the measurement time to 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: using TCSPC analysis method to calculate and obtain the light information to be measured; 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, step S31, step S41 and step S51 are executed when obtaining optical power, and step S32, step S4201, step S4202 and step S52 are executed when obtaining energy; 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 rate of the continuous light to be measured according to formula (1): , according to formula (2) to calculate the optical power , execute step S51; （1） In formula (1), 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; （2） In formula (2), 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; In step S4202, the step of using the TCSPC analysis method to calculate and obtain the light information to be measured specifically includes the following steps: based on the synchronization signal sync of the light 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 E of a single pulse 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: （3） 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; （4） In formula (4), E p is the single pulse energy; Step S52: When 0.0001≤ ≤0.1, it is known that it is in the linear detection range of the single-photon detector, and step S6 is executed; when >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; <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 of the continuous light is calculated. and photon rate .

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 light power and photon rate 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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