Weak light power detection method and detection circuit

Abstract

This invention provides a method and circuit for detecting weak optical power. The method includes: acquiring multiple digital voltage values ​​of the optical signal under test and digital temperature values ​​corresponding to the current ambient temperature; calculating the measured optical power value based on the average value of the multiple digital voltage values ​​and the digital temperature value using an optical power-voltage-temperature mapping function; obtaining the equivalent optical power value deviation by combining the independent components of each noise in the optical signal under test; and correcting the measured optical power value based on the equivalent optical power value deviation to obtain the optical power value under test. By employing a multi-point calibration and curve fitting algorithm to construct a nonlinear mapping model of optical power-voltage-temperature, the nonlinearity and temperature drift of the device are effectively compensated, improving the accuracy and environmental adaptability of weak light detection. Simultaneously, by combining the independent components of each noise in the optical signal under test to obtain the equivalent optical power value deviation, the method achieves the separate identification and real-time compensation of multiple noise components, improving the accuracy of weak light signal detection.

Description

Technical Field

[0001] This invention relates to the field of optical power measurement technology, and in particular to a method and detection circuit for detecting weak optical power. Background Technology

[0002] In existing methods for detecting weak light power, the calibration process commonly employs two-point linear calibration or fixed gain adjustment. This involves collecting calibration data at both ends of the detection range and establishing a mapping relationship between light power and voltage through linear interpolation. However, the photoelectric conversion characteristics of photodiodes exhibit a significant nonlinear response in the weak light region. The two-point linear calibration method cannot accurately describe this nonlinear relationship, leading to substantial measurement errors, especially in the middle region of the detection range and in the weak light region.

[0003] Furthermore, existing detection methods have significant shortcomings in noise handling. Photodiode amplifier circuits simultaneously contain multiple noise sources, including electronic noise, shot noise, and temperature drift noise. These noises have different physical mechanisms and statistical characteristics: electronic noise originates from the thermal motion of circuit components and is independent of the measured optical power; shot noise originates from quantum fluctuations in the photocurrent and is proportional to the square root of the measured optical power; temperature drift noise originates from the change in device responsivity with temperature and is related to ambient temperature. Existing methods typically treat all noise as a whole and perform simple filtering or averaging, failing to independently identify and specifically compensate for each noise component, making it difficult to effectively reduce measurement uncertainty in weak light regions. Summary of the Invention

[0004] This invention provides a method and circuit for detecting weak light power, thereby improving the accuracy of weak light signal detection.

[0005] This invention provides a method for detecting weak light power, the method comprising:

[0006] Acquire multiple digital voltage values ​​corresponding to the optical signal under test and digital temperature values ​​corresponding to the current ambient temperature;

[0007] Based on the optical power-voltage-temperature mapping function, the measured optical power value is calculated according to the average value of multiple voltage digital quantities and the temperature digital quantity;

[0008] By combining the independent components of each noise in the optical signal under test, the deviation of the equivalent optical power value is obtained;

[0009] The measured optical power value is corrected based on the deviation of the equivalent optical power value to obtain the optical power value to be measured.

[0010] Furthermore, acquiring the digital voltage values ​​corresponding to the optical signal under test and the digital temperature values ​​corresponding to the current ambient temperature includes:

[0011] Receive the optical signal to be tested and convert it into a photocurrent signal;

[0012] The photocurrent signal is converted from current to voltage to obtain an analog voltage signal;

[0013] Collect the current ambient temperature to obtain a simulated temperature signal;

[0014] The temperature analog signal is converted into a temperature analog voltage signal;

[0015] The analog voltage signal was collected at multiple preset standard light intensity points and at different preset ambient temperatures to obtain multiple digital voltage values.

[0016] The temperature analog voltage signal is digitally acquired to obtain the digital temperature value.

[0017] Furthermore, the analog voltage signal is acquired at multiple preset standard light intensity points and different preset ambient temperatures, including:

[0018] The system records the number of standard light intensity points collected in real time and compares the number of standard light intensity points with a set threshold. If the number of standard light intensity points does not reach the preset threshold, the system switches to the next standard light intensity point to continue collecting data. If the number reaches or exceeds the preset threshold, the system performs subsequent operations.

[0019] Furthermore, the method for obtaining the optical power-voltage-temperature mapping function includes:

[0020] The least squares method was used to fit the optical power, the average value of the digital voltage, and the digital temperature to obtain a third-order bivariate polynomial model.

[0021] Calculate the fitting coefficients in the third-order bivariate polynomial model, and construct the optical power-voltage-temperature mapping function based on the fitting coefficients.

[0022] Furthermore, the optical power-voltage-temperature mapping function uses the first to third order terms of the voltage digital quantity, the first to third order terms of the temperature digital quantity, and the cross-coupling term of the voltage digital quantity and the temperature digital quantity to express the nonlinear mapping relationship between optical power, the voltage of the optical signal under test, and the current ambient temperature.

[0023] Furthermore, the independent components of each noise include: electronic noise component, shot noise component, and temperature drift noise component.

[0024] Furthermore, the electronic noise component is: ;

[0025] in, Let K be the electronic noise component, K be the Boltzmann constant, and t be the absolute temperature. For measuring bandwidth, R is the equivalent noise resistance;

[0026] The mean square value of the shot noise component is: ;

[0027] Where q is the electron charge. Photocurrent, Dark current, Let be the mean square value of the shot noise component. For measuring bandwidth;

[0028] The temperature drift noise component is ;

[0029] in, denoted as the temperature drift noise component, k as the slope of the temperature drift coefficient, T as the ambient temperature, and b as the intercept of the temperature drift coefficient.

[0030] Furthermore, the measured optical power value is:

[0031]

[0032] in, The measured optical power value is... The equivalent power coefficient for the electronic noise component. ; This represents the equivalent power coefficient of the shot noise component. ; This is the equivalent power coefficient of the temperature drift noise component. ; To measure the optical power value, For real-time ambient temperature, This refers to the detector sensitivity.

[0033] On the other hand, the present invention discloses a weak optical power detection circuit, the circuit comprising:

[0034] The first signal conversion circuit is used to acquire the digital voltage quantity corresponding to the optical signal under test.

[0035] The second signal conversion circuit is used to obtain the digital value of the current ambient temperature.

[0036] The main control chip is used to calculate the measured optical power value based on the average value of multiple digital voltage quantities and the digital temperature quantity according to the optical power-voltage-temperature mapping function; to obtain the equivalent optical power value deviation by combining the independent components of each noise in the optical signal under test; and to correct the measured optical power value based on the equivalent optical power value deviation to obtain the optical power value under test.

[0037] Furthermore, the first signal conversion circuit includes:

[0038] A photodiode is used to receive the optical signal to be measured and convert it into a photocurrent signal.

[0039] An operational amplifier module is used to perform current-to-voltage conversion on the photocurrent signal to obtain a voltage signal;

[0040] An analog-to-digital converter is used to digitally acquire the voltage signal and obtain the digital voltage value of the optical signal under test.

[0041] Compared with the prior art, the present invention has at least the following technical effects:

[0042] In this embodiment, a nonlinear mapping model of optical power-voltage-temperature is constructed by using multi-point calibration and curve fitting algorithms, which effectively compensates for device nonlinearity and temperature drift, and improves the detection accuracy and environmental adaptability of weak light. At the same time, by combining the independent components of each noise in the optical signal under test, the equivalent optical power value deviation is obtained, and the identification and real-time compensation of multiple noise components are realized, which solves the problem of large measurement error caused by imperfect noise compensation in the prior art. Attached Figure Description

[0043] Figure 1 This is a simplified flowchart illustrating the weak light power detection method in Embodiment 1 of the present invention.

[0044] Figure 2 This is a simplified schematic diagram of the calibration process for the weak light power detection method in Embodiment 1 of the present invention;

[0045] Figure 3 This is a simplified schematic diagram of the weak light power detection circuit in Embodiment 2 of the present invention;

[0046] Figure 4 This is a schematic diagram of the first signal conversion circuit in the weak light power detection circuit of Embodiment 2 of the present invention;

[0047] Figure 5 This is a schematic diagram of the second signal conversion circuit in the weak light power detection circuit of Embodiment 2 of the present invention. Detailed Implementation

[0048] The following description, with reference to schematic diagrams, illustrates a method and circuit for detecting weak optical power according to the present invention, which represents a preferred embodiment of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0049] The invention is described more specifically by way of example in the following paragraphs with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0050] Example 1

[0051] Please refer to Figure 1 This embodiment discloses a method for detecting weak optical power, the method comprising:

[0052] S1. Acquire multiple digital voltage values ​​corresponding to the optical signal under test and digital temperature values ​​corresponding to the current ambient temperature;

[0053] S2. Based on the optical power-voltage-temperature mapping function, the measured optical power value is calculated according to the average value of multiple digital voltage quantities and the digital temperature quantity;

[0054] S3. Combine the independent components of each noise in the optical signal under test to obtain the equivalent optical power value deviation;

[0055] S4. Correct the measured optical power value based on the equivalent optical power value deviation to obtain the optical power value to be measured.

[0056] In this embodiment, a nonlinear mapping model of optical power-voltage-temperature is constructed by using multi-point calibration and curve fitting algorithms, which effectively compensates for device nonlinearity and temperature drift, and improves the detection accuracy and environmental adaptability of weak light. At the same time, by combining the independent components of each noise in the optical signal under test, the equivalent optical power value deviation is obtained, and the identification and real-time compensation of multiple noise components are realized, which solves the problem of large measurement error caused by imperfect noise compensation in the prior art.

[0057] In this embodiment, the optical power-voltage-temperature nonlinear mapping model refers to a multivariate polynomial function model with digital voltage and digital temperature as input variables and optical power as the output variable.

[0058] In this embodiment, step S1 involves acquiring multiple digital voltage values ​​corresponding to the optical signal under test and digital temperature values ​​corresponding to the current ambient temperature, including:

[0059] S11. Receive the optical signal to be tested and convert the optical signal to be tested into a photocurrent signal;

[0060] S12. Perform current-to-voltage conversion on the photocurrent signal to obtain an analog voltage signal;

[0061] S13. Collect the current ambient temperature to obtain a temperature simulation signal;

[0062] S14. Convert the temperature analog signal into a temperature analog voltage signal;

[0063] S15. At multiple preset standard light intensity points and different preset ambient temperatures, the analog voltage signal is collected to obtain multiple digital voltage quantities;

[0064] S16. The temperature analog voltage signal is digitally acquired to obtain the digital temperature value.

[0065] When performing step S15, it is necessary to record the number of standard light intensity points that have been collected in real time and compare the number of standard light intensity points with a set threshold. If the number of standard light intensity points does not reach the preset threshold, the process switches to the next standard light intensity point to continue collecting the voltage digital value. If the preset threshold is reached or exceeded, the subsequent operation is performed.

[0066] Specifically, if the number of completed calibration points has not reached the set threshold, the external standard light source will be automatically or manually adjusted to the next preset standard light intensity point. The known optical power value corresponding to the light intensity point will be input, and the corresponding analog-to-digital conversion value will be collected again to complete a new round of calibration point data collection. If the number of completed calibration points reaches or exceeds the set threshold, the system will terminate the loop acquisition process and enter the subsequent mapping relationship fitting stage, using all the collected "optical power-analog-to-digital conversion value" data sets to build the model.

[0067] In a specific example, the specific implementation method for acquiring the voltage digital quantity corresponding to the photocurrent signal at different standard light intensity points and different preset ambient temperatures, obtaining multiple voltage digital quantities, and calculating the average value of multiple voltage digital quantities can be as follows: adopting a grid method calibration process, obtaining a two-dimensional calibration grid composed of multiple preset standard light intensity points and multiple ambient temperature points, and acquiring the corresponding voltage digital quantity multiple times under each combination of standard light intensity point and each ambient temperature point, so as to calculate the average value of all voltage digital quantities under that combination condition.

[0068] Understandably, the threshold values ​​can be set according to the target detection range and accuracy requirements. More values ​​result in higher fitting accuracy, but also increase calibration time. Typically, at least five thresholds are set to improve the accuracy of the fitting model in describing the nonlinear relationship between optical power and voltage / temperature. The intensity of the standard light intensity points should cover the entire target detection range, and sampling points should be appropriately densified in the weak light regions of interest to improve the fitting accuracy in those regions. For example, when the target detection range is -70dBm to -30dBm, five equally spaced standard light intensity points (e.g., -70dBm, -60dBm, -50dBm, -40dBm, -30dBm) can be selected to ensure uniform fitting accuracy across the entire range. If further optimization of the measurement performance in weak light regions (e.g., -70dBm to -60dBm) is needed, additional standard light intensity points can be added within this range to improve local fitting accuracy.

[0069] Furthermore, the selection of temperature points should cover the target operating temperature range and consider the characteristics of device responsivity changing with temperature. The number of temperature points can be consistent with the number of standard light intensity points or adjusted according to actual needs. For example, when the target operating temperature range is -40℃ to 85℃, five temperature points can be selected: -40℃, -20℃, 25℃, 50℃, and 85℃, where 25℃ is the room temperature reference point, and the other temperature points cover extreme high and low temperature conditions.

[0070] Please refer to Figure 2 In step S2, the method for obtaining the optical power-voltage-temperature mapping function includes:

[0071] S21. The least squares method is used to fit the optical power, the average value of the digital voltage, and the digital temperature to obtain a third-order bivariate polynomial model;

[0072] S22. Calculate the fitting coefficients in the third-order bivariate polynomial model, and construct the optical power-voltage-temperature mapping function based on the fitting coefficients.

[0073] In a specific example of step S21, the specific implementation of fitting the optical power, the average value of the digital voltage, and the digital temperature using the least squares method, in conjunction with the average value of the digital voltage, is as follows:

[0074] The data from all calibration points are organized into a dataset, where each data point contains a standard optical power value, the corresponding average voltage value, and a temperature value. A third-order bivariate polynomial model is constructed with voltage and temperature as independent variables and optical power as the dependent variable. The fitting coefficients that minimize the error between the model's predicted value and the actual standard optical power value are solved with the goal of minimizing the sum of squared residuals. The optimal solutions for each fitting coefficient are obtained by solving the normal equations through matrix operations.

[0075] Preferably, after step S21, the calculated fitting coefficients are converted into a fixed-point number format (such as Q15) and stored. In this way, when the system is powered off and then powered on again, there is no need to repeat the calibration process, and the stored fitting coefficients can be directly called to calculate the optical power.

[0076] Specifically, the optical power-voltage-temperature mapping function characterizes the nonlinear mapping relationship between optical power, the voltage of the optical signal under test, and the current ambient temperature through the first to third order terms of the voltage digital quantity, the first to third order terms of the temperature digital quantity, and the cross-coupling terms of the voltage digital quantity and the temperature digital quantity.

[0077] In a specific example, the optical power-voltage-temperature mapping function is:

[0078] ;

[0079] Wherein, V is the average value of the multiple voltage digital quantities; T is the temperature digital quantity corresponding to the current ambient temperature; a, b, c, d, e, f, g, h, i, j are fitting coefficients, obtained by fitting the calibration data using the least squares method; and P is the calculated measured optical power value.

[0080] In this embodiment, based on a third-order polynomial fitting model with more than five calibrations, by introducing cross-coupling terms for digital voltage and digital temperature, the complex nonlinear relationship between optical power and voltage and temperature can be accurately described, effectively improving the measurement accuracy across the entire detection range, especially significantly improving the measurement accuracy in the weak light region.

[0081] After completing step S21, substitute the digital voltage and the digital temperature into the optical power-voltage-temperature mapping function to obtain the optical power value to be measured.

[0082] In step S3, the independent components of each noise include: electronic noise component, shot noise component, and temperature drift noise component. Those skilled in the art can select the noise components that need to be compensated according to the actual application scenario and accuracy requirements. For example, in application scenarios with small temperature changes, compensation for temperature drift noise component can be omitted, and in application scenarios with high optical power, compensation for shot noise component can be omitted. No specific restrictions are imposed here.

[0083] In a specific example, the method for identifying and quantizing electronic noise components is as follows:

[0084] With the light input turned off and the photodiode completely blocked, the root mean square (RMS) value at the calibration point is measured, and the mean square value of the circuit's thermal noise is calculated. The electronic noise component is: .

[0085] in, Let K be the electronic noise component, K be the Boltzmann constant, and t be the absolute temperature. The bandwidth is determined by the bandwidth of the amplifier circuit and the sampling rate of the analog-to-digital converter. R is the equivalent noise resistance.

[0086] In a specific example, the measurement bandwidth is determined by the signal processing link characteristics of the system, including but not limited to the frequency response characteristics of the signal conditioning circuit and the sampling frequency of the sampling system. Those skilled in the art can determine the specific measurement bandwidth value according to the actual system configuration.

[0087] In another specific example, the method for identifying and quantifying the shot noise component is as follows: A small signal perturbation (±10%) is applied in a weak light region (e.g., at a power point of -70 dBm), the square root relationship between the photocurrent and the noise is measured, and the mean square value of the shot noise component is calculated.

[0088] The mean square value of the shot noise component is: ;

[0089] Where q is the electron charge. Photocurrent, Dark current, Let be the mean square value of the shot noise component. For measuring bandwidth.

[0090] In another specific example, the method for identifying and quantizing the temperature drift noise component is as follows:

[0091] The system responsivity is measured at each temperature point, and the curve of responsivity changing with temperature is recorded. The temperature drift noise figure is then fitted. The temperature drift noise component is: ;

[0092] in, denoted as the temperature drift noise component, k as the slope of the temperature drift coefficient, T as the ambient temperature, and b as the intercept of the temperature drift coefficient.

[0093] In this embodiment, by incorporating temperature as an independent variable into the noise model, the problem of decreased accuracy over a wide temperature range caused by neglecting temperature factors in existing technologies is solved, enabling the system to maintain stable detection accuracy over a wider operating temperature range. Simultaneously, by separately identifying and independently quantifying electronic noise, shot noise, and temperature drift noise, targeted compensation can be performed based on the different physical characteristics of each noise component, achieving a more accurate noise compensation effect.

[0094] In this embodiment, the optical power value to be measured is:

[0095] ;

[0096] in, The measured optical power value is... The equivalent power coefficient for the electronic noise component. ; This represents the equivalent power coefficient of the shot noise component. ; This is the equivalent power coefficient of the temperature drift noise component. ; To measure the optical power value, For real-time ambient temperature, This refers to the detector sensitivity.

[0097] In this embodiment, by independently identifying and accurately quantifying each noise component, and subtracting it from the measurement result as equivalent to optical power deviation, the systematic influence of noise on the measurement result can be effectively eliminated, making the final output measured optical power value closer to the true incident optical power, thereby significantly improving the detection accuracy and measurement reliability of weak light areas.

[0098] Example 2

[0099] Please refer to Figures 3-5 Based on the same inventive concept, this embodiment discloses a weak light power detection circuit, the circuit comprising:

[0100] The first signal conversion circuit is used to acquire the digital voltage quantity corresponding to the optical signal under test.

[0101] The second signal conversion circuit is used to obtain the digital value of the current ambient temperature.

[0102] The main control chip calculates the measured optical power value based on the optical power-voltage-temperature mapping function, according to the average value of multiple digital voltage quantities and the digital temperature quantity; it obtains the equivalent optical power value deviation by combining the independent components of each noise in the optical signal under test; and it corrects the measured optical power value based on the equivalent optical power value deviation to obtain the optical power value under test.

[0103] Please refer to Figure 4 In this embodiment, the first signal conversion circuit includes:

[0104] A photodiode is used to receive the optical signal to be measured and convert it into a photocurrent signal.

[0105] An operational amplifier module is used to perform current-to-voltage conversion on the photocurrent signal to obtain a voltage signal.

[0106] An analog-to-digital converter is used to digitally acquire the voltage signal and obtain the digital voltage value of the optical signal under test.

[0107] In this embodiment, a combination of operational amplifier module and main control chip is used to replace discrete transistor amplification scheme and high-cost precision transimpedance amplifier scheme. Without reducing measurement accuracy, the number of external components is effectively reduced, the circuit board area is reduced, and hardware costs and assembly complexity are reduced. At the same time, the rapid settling characteristics of operational amplifier module are used to improve the response speed of signal acquisition and meet the requirements of high-frequency dynamic optical signal detection.

[0108] In this embodiment, the digital voltage output from the analog-to-digital converter is directly input to the main control chip for calculation and processing, eliminating the need for additional signal conditioning and improving system simplicity and anti-interference capability. Furthermore, the photodiode, as a photoelectric conversion device, has a large photosensitive area and high responsivity, with a theoretical minimum detectable optical power on the order of -80dBm, or 10pW, which can meet the sensitivity requirements for detecting weak light signals.

[0109] In another specific example, the operational amplifier module includes a first operational amplifier and a second operational amplifier.

[0110] Please continue to refer to this. Figure 4 The connection relationship of this weak optical power detection circuit is as follows: the output terminal of photodiode PIN5 is connected to the inverting input terminal of the first operational amplifier YF6C, the non-inverting input terminal of the first operational amplifier YF6C is grounded, and the feedback network is composed of resistor R168 and capacitor C76 connected in parallel, which is used to convert the photocurrent signal into a voltage signal and realize low-pass filtering; the output terminal of the first operational amplifier YF6C is connected to the non-inverting input terminal of the second operational amplifier YF6D through resistor R146, and its inverting input terminal is grounded through resistor R148. The feedback resistor R153 is connected in parallel between the inverting input terminal and the output terminal, which is used to perform secondary amplification and level adjustment of the output voltage of the previous stage; the output terminal of the second operational amplifier YF6D is connected to the input pin Pin_ADC of the analog-to-digital converter of the main control chip. At the same time, the current ambient temperature data collected by the temperature sensor is also input to the main control chip. The main control chip obtains the optical power value to be measured based on the optical power-voltage-temperature mapping function and noise correction algorithm.

[0111] Furthermore, in this embodiment, the operational amplifier is provided with a feedback network, the resistance of which depends on the size of the target detection range.

[0112] In a specific example, the feedback network is connected in parallel between the inverting input and output of the operational amplifier.

[0113] In another specific example, the feedback network consists of a high-precision metal film resistor connected in parallel with a compensation capacitor exhibiting excellent temperature stability. Preferably, the feedback resistor is a high-precision metal film resistor with a resistance of 10MΩ or higher to obtain sufficient transimpedance gain; the compensation capacitor is preferably a low-temperature drift capacitor of approximately 10pF to suppress high-frequency oscillations in the circuit and maintain system stability.

[0114] In this embodiment, the detection range of the system can be adjusted by changing the feedback resistor with different resistance values. A larger resistance value corresponds to a higher transimpedance gain, which is suitable for detecting weaker light signals; a smaller resistance value corresponds to a lower transimpedance gain, which is suitable for detecting stronger light signals.

[0115] In one specific example, the temperature sensor is preferably an NTC thermistor, which has the advantages of high sensitivity, fast response speed, and low cost. The temperature sensor is positioned close to the photodiode to accurately reflect the operating temperature of the photodiode and improve the accuracy of temperature drift compensation.

[0116] In this embodiment, the current ambient temperature is acquired by the temperature sensor to obtain a temperature analog signal. The temperature analog signal is converted into a temperature analog voltage signal by a thermistor, and finally converted into a digital temperature value by a second signal conversion circuit.

[0117] Please refer to Figure 5 In a specific example, the temperature analog voltage signal is fed into a voltage follower composed of an operational amplifier YF3D through the TEMP port. The high input impedance and low output impedance of the operational amplifier are used to achieve impedance isolation and signal buffering, avoiding the influence of the downstream load on the sensor signal. The buffered signal is output from the output pin 14 of the operational amplifier as the input of the analog-to-digital converter. Finally, the analog-to-digital converter converts the analog voltage into a digital quantity for the system to perform temperature calculation and processing.

[0118] In a specific example, the photocurrent signal and the temperature analog voltage signal are acquired by a 12-bit analog-to-digital converter with a reference voltage of 3.3V and a corresponding voltage resolution of approximately 0.8mV.

[0119] In another specific example, the analog-to-digital converter communicates with the main control chip via an SPI interface, sending the acquired digital sampled values ​​to the main control chip in real time for subsequent calculation and processing.

[0120] In another specific example, the main control chip preferably employs a microcontroller unit (MCU) with an on-chip analog-to-digital converter and non-volatile memory to execute calibration, noise component identification and compensation algorithms, and to store calibration parameters and fitting coefficients. The main control chip may also integrate a communication interface for data interaction with a host computer, enabling the configuration of calibration data and the output of measurement results.

[0121] Those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A weak optical power detection method, characterized by, The method includes: Acquire multiple digital voltage values ​​corresponding to the optical signal under test and digital temperature values ​​corresponding to the current ambient temperature; Based on the optical power-voltage-temperature mapping function, the measured optical power value is calculated according to the average value of multiple voltage digital quantities and the temperature digital quantity; By combining the independent components of each noise in the optical signal under test, the deviation of the equivalent optical power value is obtained; The measured optical power value is corrected based on the equivalent optical power value deviation to obtain the optical power value to be measured; The method for obtaining the optical power-voltage-temperature mapping function includes: The least squares method was used to fit the optical power, the average value of the digital voltage, and the digital temperature to obtain a third-order bivariate polynomial model. Calculate the fitting coefficients in the third-order bivariate polynomial model, and construct the optical power-voltage-temperature mapping function based on the fitting coefficients.

2. The weak optical power detection method of claim 1, wherein, The acquisition of multiple digital voltage values ​​corresponding to the optical signal under test and the digital temperature value corresponding to the current ambient temperature includes: Receive the optical signal to be tested and convert it into a photocurrent signal; The photocurrent signal is converted from current to voltage to obtain an analog voltage signal; Collect the current ambient temperature to obtain a simulated temperature signal; The temperature analog signal is converted into a temperature analog voltage signal; The analog voltage signal was collected at multiple preset standard light intensity points and at different preset ambient temperatures to obtain multiple digital voltage values. The temperature analog voltage signal is digitally acquired to obtain the digital temperature value.

3. The weak optical power detection method of claim 2, wherein, The analog voltage signal was acquired at multiple preset standard light intensity points and at different preset ambient temperatures, including: The system records the number of standard light intensity points collected in real time and compares the number of standard light intensity points with a set threshold. If the number of standard light intensity points does not reach the preset threshold, the system switches to the next standard light intensity point to continue collecting data. If the number reaches or exceeds the preset threshold, the system performs subsequent operations.

4. The weak optical power detection method as described in claim 3, characterized in that, The optical power-voltage-temperature mapping function characterizes the nonlinear mapping relationship between optical power, the voltage of the optical signal under test, and the current ambient temperature through the first to third order terms of the voltage digital quantity, the first to third order terms of the temperature digital quantity, and the cross-coupling terms of the voltage digital quantity and the temperature digital quantity.

5. The weak optical power detection method of claim 1, wherein, The independent components of each noise include: electronic noise component, shot noise component, and temperature drift noise component.

6. The weak optical power detection method as described in claim 5, characterized in that, The electronic noise component is: ; wherein is the electronic noise component, K is the Boltzmann constant, t is the absolute temperature, is the measurement bandwidth, R is the equivalent noise resistance; The mean square value of the shot noise component is: ; Where q is the electron charge. Photocurrent, Dark current, Let be the mean square value of the shot noise component. For measuring bandwidth; The temperature drift noise component is ; wherein, is the temperature drift noise component, k is the temperature drift coefficient slope, T is the ambient temperature, and b is the temperature drift coefficient intercept.

7. The weak optical power detection method of claim 1, wherein, The measured optical power value is: ； in, The measured optical power value is... The equivalent power coefficient for the electronic noise component. This represents the equivalent power coefficient of the shot noise component. This is the equivalent power coefficient of the temperature drift noise component. To measure the optical power value, For real-time ambient temperature, This represents the detector sensitivity.

8. A weak optical power detection circuit, characterized by comprising: The circuit includes: The first signal conversion circuit is used to acquire the digital voltage quantity corresponding to the optical signal under test. The second signal conversion circuit is used to obtain the digital value of the current ambient temperature. The main control chip is used to calculate the measured optical power value based on the optical power-voltage-temperature mapping function, according to the average value of multiple digital voltage quantities and the digital temperature quantity; to obtain the equivalent optical power value deviation by combining the independent components of each noise in the optical signal under test; and to correct the measured optical power value based on the equivalent optical power value deviation to obtain the optical power value under test. The method for obtaining the optical power-voltage-temperature mapping function includes: The least squares method was used to fit the optical power, the average value of the digital voltage, and the digital temperature to obtain a third-order bivariate polynomial model. Calculate the fitting coefficients in the third-order bivariate polynomial model, and construct the optical power-voltage-temperature mapping function based on the fitting coefficients.

9. The weak optical power detection circuit of claim 8, wherein, The first signal conversion circuit includes: A photodiode is used to receive the optical signal to be measured and convert it into a photocurrent signal. An operational amplifier module is used to perform current-to-voltage conversion on the photocurrent signal to obtain a voltage signal; An analog-to-digital converter is used to digitally acquire the voltage signal and obtain the digital voltage value of the optical signal under test.

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