In-situ calibration device and method for absolute frequency reference of ultra-narrow band optical filter

Abstract

The invention discloses an ultra-narrow band optical filter absolute frequency reference in-situ calibration device which comprises a hollow cathode lamp, the output end of the hollow cathode lamp is connected with one input end of a one-to-two optical fiber through a light beam coupling device, and the output end of a variable diaphragm is connected with the other input end of the one-to-two optical fiber through an optical fiber; light beams output by the one-to-two optical fiber are split, the first split beam is input to the second photoelectric detector, and the second split beam transmits the ultra-narrow band light filter and is detected by the first photoelectric detector; the invention further discloses an in-situ calibration method for the absolute frequency reference of the ultra-narrow band light filter, the center transmission wavelength of the etalon is calibrated through the absolute wavelength of the hollow cathode lamp, the etalon is accurately controlled at constant temperature and constant voltage, the center transmission wavelength of the etalon is calibrated, and the calibration of the center wavelength of the etalon is integrated with an external optical signal detection function; and through the automatic calibration process, the calibration efficiency is greatly improved, manual operation errors are avoided, and a high-precision calibration task can be completed in a short time.

Description

Technical Field

[0001] This invention relates to the field of optical precision measurement technology, specifically to an in-situ calibration device for an absolute frequency reference of an ultra-narrowband filter, and also to an in-situ calibration method for an absolute frequency reference of an ultra-narrowband filter. It is applicable to scenarios in fields such as optical communication, laser frequency stabilization, spectral analysis, environmental monitoring, and lidar where the accuracy of the center transmission wavelength of the ultra-narrowband filter is required. It can realize automated and high-precision calibration of the filter in its working position. Background Technology

[0002] Ultra-narrowband (UNB) filters, as key optical devices, typically have a transmission bandwidth of only a few picometers to tens of picometers. They can accurately filter specific narrow-band optical signals from complex spectra and are one of the core components ensuring the performance of optical systems. In optical communication systems, UNB filters are used for the separation and extraction of wavelength division multiplexed signals; in the field of laser technology, they are used for the purification and stabilization of laser frequencies; in environmental monitoring scenarios, they can achieve the accurate detection of trace gas characteristic spectral lines. All of these applications place extremely high demands on the accuracy of the center transmission wavelength of UNB filters. Even a small drift in the center wavelength (such as ±0.001 nm or more) can lead to problems such as increased system bit error rate and measurement errors exceeding the standard.

[0003] However, in existing technologies, the center transmission wavelength of optical ultra-narrowband filters is easily affected by external environmental factors: temperature changes cause thermal expansion and contraction of the filter substrate material, altering the optical thickness and thus inducing wavelength drift (typically, a 1°C temperature change can cause a wavelength drift of 0.01-0.05 nm); air pressure fluctuations affect the refractive index of the medium inside or around the filter, especially for ultra-narrowband filters based on air gap structures, where a 0.01 atm change in air pressure results in a wavelength drift of approximately 0.002 nm; environmental vibrations can cause changes in the adhesion of the filter's reflective film, disrupting multi-beam interference conditions and further exacerbating wavelength instability.

[0004] Existing calibration methods have significant shortcomings in addressing the aforementioned issues:

[0005] Manual offline calibration is inefficient and prone to errors: Traditional methods require removing the ultra-narrowband filter from the working optical path and transferring it to dedicated calibration equipment (such as a high-precision spectrometer). The center transmission wavelength is then determined by manually adjusting the light source wavelength and observing the instrument readings. This process takes at least 2-4 hours, and mechanical stress is easily introduced during disassembly / reassembly, causing wavelength shift after the filter is reset. The randomness of manual readings and operations can reach ±0.005nm, which cannot meet the requirements of high-precision scenarios.

[0006] Insufficient stability of calibration light source: Some calibration schemes use ordinary lasers as calibration light sources, whose frequency stability is greatly affected by temperature and current (long-term stability is about ±0.003nm / h), and cannot provide an absolute frequency reference, resulting in a "reference drift" problem in the calibration results, which cannot guarantee the long-term working accuracy of the filter.

[0007] Incomplete environmental disturbance compensation: Existing constant temperature and pressure control devices can only stabilize the temperature to ±0.01℃ and the pressure to ±0.001atm, and there are still residual environmental disturbances; moreover, no correlation model between environmental parameters and wavelength drift has been established, so it is impossible to dynamically compensate for the wavelength shift caused by residual disturbances, resulting in wavelength drift still occurring in the calibrated filter during operation.

[0008] Poor optical path switching and operational coordination: Although some solutions attempt to switch between the calibration optical path and the working optical path, the switching process relies on manual operation, and the switching delay can reach the second level. Furthermore, the fluctuation of light intensity and the change of optical path collimation after switching will introduce additional errors (approximately ±0.002nm), making it impossible to achieve "calibration without interruption of operation" and affecting the continuous operation of the optical system.

[0009] To address the shortcomings of the existing technologies, this invention proposes an in-situ calibration method and apparatus for the absolute frequency reference of ultra-narrowband filters. By employing technologies such as atomic absolute frequency reference calibration, environmental parameter-wavelength drift dynamic mapping, and intelligent optical path switching, the method achieves in-situ, automatic, and high-precision calibration of the filters, thus solving problems such as low calibration efficiency, large errors, and weak environmental interference resistance. Summary of the Invention

[0010] This invention proposes an in-situ calibration device for the absolute frequency reference of ultra-narrowband filters, and also provides an in-situ calibration method for the absolute frequency reference of ultra-narrowband filters. It aims to solve the problem that the drift of optical ultra-narrowband filters caused by changes in environmental factors such as temperature and pressure affects their long-term stable operation, and provides a precise, fast and automated calibration scheme.

[0011] The above-mentioned technical problems of the present invention are mainly solved by the following technical solutions:

[0012] An in-situ calibration device for an absolute frequency reference of an ultra-narrowband filter includes a hollow cathode lamp. The output end of the hollow cathode lamp is connected to one input end of a 1-to-2 optical fiber via a beam coupling device. The output end of a variable aperture is connected to the other input end of the 1-to-2 optical fiber via an optical fiber. The beam output from the 1-to-2 optical fiber is split into a first beam and a second beam. The first beam is input to a second photodetector, converted into a corresponding electrical signal, and then transmitted to a control and display unit. The second beam passes sequentially through a beam collimator and a narrowband filter, and then sequentially transmits through a first etalon and a second etalon in the ultra-narrowband filter. The first photodetector converts the signal into a corresponding electrical signal, which is then transmitted to the control and display unit.

[0013] The first standard fixture is disposed inside a first standard fixture pressure tank. A first strain sensor and a first piezoelectric ceramic support are disposed on the first standard fixture. A fifth pressure sensor and a first temperature control device are also disposed in the first standard fixture pressure tank. The first strain sensor, the first piezoelectric ceramic support, the fifth pressure sensor and the first temperature control device are all connected to the control and display unit.

[0014] The second standard fixture is installed inside the second standard fixture pressure tank. The second standard fixture is equipped with a second strain sensor and a second piezoelectric ceramic support. The second standard fixture pressure tank is also equipped with a second temperature control device and a sixth pressure sensor. The second strain sensor, the second piezoelectric ceramic support, the second temperature control device and the sixth pressure sensor are all connected to the control and display unit.

[0015] As described above, the first standard pressure vessel is equipped with a seventh pressure flow control valve for controlling the outlet air and an eighth pressure flow control valve for controlling the inlet air. The eighth pressure flow control valve is connected to the outlet of the third cylinder. The third cylinder is equipped with a fourth pressure sensor and a sixth pressure flow control valve. The seventh, eighth, fourth, and sixth pressure flow control valves are all connected to the control display unit. The third cylinder is equipped with a fourth temperature control device, and the control port of the fourth temperature control device is connected to the control display unit.

[0016] The second standard pressure vessel is equipped with a ninth pressure flow control valve for controlling the outlet air and a tenth pressure flow control valve for controlling the inlet air. The tenth pressure flow control valve is connected to the outlet of the second cylinder. The second cylinder is equipped with a third pressure sensor and a fourth pressure flow control valve. The ninth pressure flow control valve, the tenth pressure flow control valve, the third pressure sensor, and the fourth pressure flow control valve are connected to the control display unit. The second cylinder is equipped with a third temperature control device, and the control port of the third temperature control device is connected to the control display unit.

[0017] As described above, the air inlet of the second cylinder is connected to the first cylinder via a third air pressure and flow control valve;

[0018] The air intake of the third cylinder is connected to the first cylinder via a fifth air pressure and flow control valve; the first cylinder is equipped with a second air pressure sensor and a second air pressure and flow control valve.

[0019] The air inlet of the first cylinder is connected to the air pump via the first air pressure and flow control valve, and the first air pressure sensor is installed on the air pump.

[0020] The first air pressure sensor, the first air pressure flow control valve, the second air pressure sensor and the second air pressure flow control valve, the third air pressure flow control valve, and the fifth air pressure flow control valve are all connected to the control and display unit.

[0021] An in-situ calibration method for an absolute frequency reference of an ultra-narrowband filter, utilizing the in-situ calibration device for an absolute frequency reference of an ultra-narrowband filter as described above, specifically includes the following steps:

[0022] Step 1: Build an in-situ calibration device for an absolute frequency reference of an ultra-narrow band filter. The calibration light emitted by the hollow cathode lamp passes through the first standard and the second standard and is detected and received by the first photodetector. The control and display unit adjusts the air pressure in the first standard pressure tank and the second standard pressure tank respectively so that the transmittance of the first standard and the second standard reaches the maximum at the working wavelength of the standard.

[0023] Step 2: Turn off the hollow cathode lamp, turn on the variable aperture to allow the beam of external signal light to enter the variable aperture, and perform constant temperature and pressure control on the ultra-narrow band filter.

[0024] Step 3: After the ultra-narrow band filter enters the working stage, record the acquisition parameters of the sensors installed in the first and second standard etalon pressure tanks and the detection values ​​of the photodetector as reference parameters.

[0025] Step 4: Monitor the changes in air pressure and temperature of the first and second standard etalon pressure tanks, read the values ​​of the first and second strain sensors, and establish a mapping model between the changes in air pressure and temperature of the standard etalon pressure tanks, the strain sensor detection values, and the relative transmittance of the ultra-narrow band filter based on the reference parameters; adjust the angles of the first and second piezoelectric ceramic supports according to the mapping model to keep the ultra-narrow band filter working stably.

[0026] As described above, step 1 includes the following steps:

[0027] Step 1.1: Determine the working wavelengths of the first and second etalons, and select the corresponding hollow cathode lamps based on the working wavelengths of the etalons; build the in-situ calibration device for the absolute frequency reference of the ultra-narrow band filter.

[0028] Step 1.2: Set the temperature inside the first standard pressure vessel via the control display unit. Temperature inside the second standard pressure vessel , Indicates the maximum temperature deviation. The operating temperature at the center of the first standard fixture. The center operating temperature of the second standard fixture;

[0029] Step 1.3: Gradually optimize the air pressure in the first and second standard etalon pressure tanks to maximize the strength of the test electrical signal output by the first photodetector; and record the air pressure in the first and second standard etalon pressure tanks when the strength of the test electrical signal output by the first photodetector is maximized.

[0030] As mentioned above, the data acquisition parameters of the sensors installed on the first and second standard pressure vessels and the detection values ​​of the photoelectric detectors in step 3 specifically include:

[0031] The first etalon reference pressure was collected by the fifth barometer. The first standard reference temperature collected by the first temperature control device The initial strain value of the first strain sensor is denoted as the reference value of the first strain sensor. ;

[0032] The second etalon reference pressure was collected by the sixth barometer. The second etalon reference temperature collected by the sixth barometric pressure sensor The initial strain value of the second strain sensor is denoted as the reference value of the second strain sensor. ;

[0033] The intensity of the test light signal detected by the first photodetector is recorded as the reference value of the first photodetector. ,

[0034] The intensity of the reference light signal detected by the second photodetector is denoted as the reference value of the second photodetector. .

[0035] The mapping model described above is:

[0036] For the first standard vessel:

[0037] ;

[0038] For the second standard vessel:

[0039] ;

[0040] in:

[0041] and This is the angle adjustment value;

[0042] and This represents the change in air pressure. , ;

[0043] and The change in temperature , ;

[0044] and The change in strain , ;

[0045] , , Monitoring values ​​belonging to the first standard figure during continuous operation:

[0046] As the first standard for monitoring air pressure,

[0047] The first standard is used to monitor temperature.

[0048] As the first standard for monitoring strain,

[0049] , , Monitoring values ​​during the continuous operation of the second standard etalon:

[0050] The second standard instrument is used to monitor air pressure.

[0051] The second standard is used to monitor temperature.

[0052] As a second standard for monitoring strain,

[0053] , , , Belongs to the The parameter correlation coefficient of a standard etalon is denoted as the parameter correlation coefficient. , , , :

[0054] Parameter correlation coefficient Characterizing the first Angle adjustment coefficient corresponding to unit air pressure deviation of the standard tassel;

[0055] Parameter correlation coefficient Characterizing the first Angle adjustment factor corresponding to unit temperature deviation of standard etalon;

[0056] Parameter correlation coefficient Characterizing the first Angle adjustment factor corresponding to unit strain deviation of standard etalon;

[0057] Parameter correlation coefficient Representation for the first Etameter, causing the change in relative transmittance When returning to the threshold range of relative transmittance change, the angle compensation correction value corresponding to the unit relative transmittance change;

[0058] The target relative transmittance deviation value represents the current change in relative transmittance. The deviation value within the relative transmittance change threshold range;

[0059] Relative transmittance change ;

[0060] This is the value monitored by the first detector.

[0061] This is the value monitored by the second detector.

[0062] As mentioned above, the parameter correlation coefficients in the mapping model in step 4 are determined through the following steps:

[0063] The first standard instrument monitors air pressure. The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain Classified into the control parameter group;

[0064] After the ultra-narrowband filter enters the normal operation phase, each parameter in the control parameter group is adjusted one by one, and the corresponding monitoring value of the first detector is collected. Second detector monitoring value ;

[0065] Corresponding to the current parameter set, adjust the angles of the first piezoelectric ceramic support and the second piezoelectric ceramic support so that the first photodetector detects the monitored value of the first detector. When the strength reaches its maximum, record the corresponding angle adjustment value of the first piezoelectric ceramic support. The angle adjustment value of the second piezoelectric ceramic support ;

[0066] Each set of control parameters and the corresponding first detector monitoring value I 1t The second detector's monitored value I 2t Angle adjustment value , Substituting the mapping model established in step 4.1, the parameter correlation coefficients in the mapping model are obtained by fitting using the least squares method. , , , .

[0067] As described above, step 4 involves adjusting the angles of the first and second piezoelectric ceramic supports according to the mapping model. This process specifically includes the following steps:

[0068] Step 4.4.1: Continuously collect air pressure data from the first standard instrument. The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain First detector monitoring value The second detector's monitoring value It also calculates the current relative transmittance change of the ultra-narrowband filter in real time. ;

[0069] When the relative transmittance changes When the relative transmittance change exceeds the threshold range:

[0070] If the number of consecutive compensation operations is less than the preset number, proceed to step 4.4.2;

[0071] If the number of times the compensation has been performed consecutively is equal to the preset number, then return to step 1;

[0072] Step 4.4.2: Set the current real-time monitoring of the first standard datum pressure. The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain First detector monitoring value The second detector's monitoring value Input the established mapping model and solve for the angle adjustment value in reverse. , ;

[0073] Step 4.4.3: Adjust the angle according to the calculated value by controlling the display unit. , The angles of the first and second piezoelectric ceramic supports are adjusted.

[0074] Compared with the prior art, the present invention has the following significant advantages:

[0075] Using atomic absolute frequency references to calibrate optical ultra-narrowband filters greatly improves the accuracy of the center transmission wavelength of ultra-narrowband filters.

[0076] Based on existing constant temperature and pressure control, a real-time mapping model between environmental parameters (temperature, pressure) and the center wavelength drift of the ultra-narrowband filter is added. During calibration, not only is wavelength calibration performed, but the correspondence between current environmental parameters and wavelength drift is also recorded simultaneously, establishing a dynamic compensation database. This enables in-situ rapid calibration of optical ultra-narrowband filters, significantly improving the efficiency of etalon calibration and avoiding errors from human operation. Attached Figure Description

[0077] Figure 1 Rapid automatic calibration device for center transmission wavelength of standard etalon.

[0078] Among them, 1-air pump, 2-first air pressure sensor, 3-first air pressure flow control valve, 4-first cylinder, 5-second air pressure sensor, 6-second air pressure flow control valve, 7-third air pressure flow control valve, 8-second cylinder, 9-third air pressure sensor, 10-fourth air pressure flow control valve, 11-fifth air pressure flow control valve, 12-third cylinder, 13-fourth air pressure sensor, 14-sixth air pressure flow control valve, 15-controller, 16-computer, 17-hollow cathode lamp, 18-beam coupling device, 19-one-to-two fiber optic cable, 20-beam collimator, 21-seventh air pressure flow control valve, 22-eighth air pressure flow control valve 23-Control valve, 24-First photodetector, 25-Fifth pressure sensor, 26-First temperature control device, 27-First etalon pressure tank, 28-Narrow band filter, 29-Second etalon, 30-Ninth pressure flow control valve, 31-Tenth pressure flow control valve, 32-Second etalon pressure tank, 33-Second temperature control device, 34-Sixth pressure sensor, 35-Variable aperture, 36-Third temperature control device, 37-Fourth temperature control device, 38-Second photodetector, 39-First strain sensor, 40-Second strain sensor, 41-First piezoelectric ceramic support, 42-Second piezoelectric ceramic support. Detailed Implementation

[0079] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to embodiments. It should be understood that the embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0080] This invention proposes an in-situ calibration device for an absolute frequency reference of an ultra-narrowband filter, such as... Figure 1 As shown, it includes an absolute frequency reference module, a constant temperature and pressure-stress co-execution module, and a control and display unit:

[0081] 1. Absolute frequency reference module

[0082] A hollow cathode lamp 17 is used, along with a beam coupling device 18. The atomic emission spectrum of the hollow cathode lamp 17 is used as calibration light and coupled into a split-beam fiber 19. 10% of the light is coupled into a second photodetector 38, and 90% of the beam is converted into parallel light after passing through a beam collimator 20, with a parallelism error ≤0.1mrad. After being filtered by a narrow-band filter 28, the parallel light enters an ultra-narrow-band filter composed of a first etalon 27 and a second etalon 29. The specific structure is as follows:

[0083] The output end of the hollow cathode lamp 17 is connected to one input end of the split-to-two fiber optic cable 19 through the beam coupling device 18, and the output end of the variable aperture 35 is connected to the other input end of the split-to-two fiber optic cable 19 through the fiber optic cable. The beam output from the split-to-two fiber optic cable 19 is split into a first beam and a second beam. The first beam is input to the second photodetector 38 and converted into a corresponding electrical signal, which is then transmitted to the control and display unit. The second beam passes through the beam collimator 20 and the narrowband filter 28 in sequence, and then passes through the first etalon 27 and the second etalon 29 in the ultra-narrowband filter in sequence. It is then converted into a corresponding electrical signal by the first photodetector 23 and transmitted to the control and display unit. When the calibration light output from the hollow cathode lamp 17 is incident on the split-beam fiber 19, the first beam of the calibration light is the reference light, and the corresponding second beam is the test light. The reference light is input to the second photodetector 38 and converted into a reference electrical signal, which is then transmitted to the control and display unit. The test light passes through the beam collimator 20 and the narrowband filter 28 in sequence, and then passes through the first etalon 27 and the second etalon 29 in the ultra-narrowband filter in sequence. It is then converted into a test electrical signal by the first photodetector 23 and transmitted to the control and display unit.

[0084] 2. Constant Temperature and Pressure-Stress Co-execution Module

[0085] A sealed, insulated cavity and multi-stage air pressure control are employed to maintain constant temperature and pressure in the environment surrounding the etalons. Furthermore, to achieve stress compensation, three sets of high-precision piezoelectric ceramic adjustment supports (i.e., first piezoelectric ceramic support 41 and second piezoelectric ceramic support 42, used to monitor horizontal, pitch, and rotational positions) and strain sensors (first strain sensor 39 and second strain sensor 40) are used for each etalon (i.e., first etalon 27 and second etalon 29). These sensors can detect stress deformation of the filter caused by temperature / pressure changes in real time and compensate for wavelength drift caused by stress by outputting micro-displacements through the piezoelectric ceramics. The specific structure is as follows:

[0086] To place the first standard fixture 27 and the second standard fixture 29 in a constant temperature and pressure environment, the first standard fixture 27 is disposed inside the first standard fixture pressure tank 26. The first standard fixture 27 is provided with a first strain sensor 39 and a first piezoelectric ceramic support 41. The first standard fixture pressure tank 26 is also provided with a fifth pressure sensor 24 and a first temperature control device 25. The first strain sensor 39, the first piezoelectric ceramic support 41, the fifth pressure sensor 24 and the first temperature control device 25 are all connected to the control and display unit.

[0087] The second standard fixture 29 is disposed inside the second standard fixture pressure tank 32. The second standard fixture 29 is provided with a second strain sensor 40 and a second piezoelectric ceramic support 42. The second standard fixture pressure tank 32 is also provided with a second temperature control device 33 and a sixth pressure sensor 34. The second strain sensor 40, the second piezoelectric ceramic support 42, the second temperature control device 33 and the sixth pressure sensor 34 are all connected to the control and display unit.

[0088] To control the air pressure inside the first standard pressure vessel 26, a seventh air pressure flow control valve 21 for controlling the outlet air and an eighth air pressure flow control valve 22 for controlling the inlet air are installed on the first standard pressure vessel 26. The eighth air pressure flow control valve 22 is connected to the outlet of the third cylinder 12. A fourth air pressure sensor 13 and a sixth air pressure flow control valve 14 are installed on the third cylinder 12 for real-time monitoring and control of the air pressure inside the third cylinder 12. The seventh air pressure flow control valve 21, the eighth air pressure flow control valve 22, the fourth air pressure sensor 13, and the sixth air pressure flow control valve 14 are all connected to the control display unit. A fourth temperature control device 37 is installed inside the third cylinder 12, and the control port of the fourth temperature control device 37 is connected to the control display unit.

[0089] To control the air pressure inside the second standard pressure vessel 32, a ninth air pressure flow control valve 30 for controlling the outlet air and a tenth air pressure flow control valve 31 for controlling the inlet air are installed on the second standard pressure vessel 32. The tenth air pressure flow control valve 31 is connected to the outlet of the second cylinder 8. A third air pressure sensor 9 and a fourth air pressure flow control valve 10 are installed on the second cylinder 8 for real-time monitoring and control of the air pressure inside the second cylinder 8. The ninth air pressure flow control valve 30, the tenth air pressure flow control valve 31, the third air pressure sensor 9, and the fourth air pressure flow control valve 10 are all connected to the control display unit. A third temperature control device 36 is installed inside the second cylinder 8, and the control port of the third temperature control device 36 is connected to the control display unit.

[0090] In this embodiment, to ensure stable air pressure in the second cylinder 8, the air inlet of the second cylinder 8 is connected to the first cylinder 4 via a third air pressure and flow control valve 7.

[0091] To ensure stable air pressure in the third cylinder 12, the air inlet of the third cylinder 12 is connected to the first cylinder 4 via the fifth air pressure and flow control valve 11; the first cylinder 4 is equipped with a second air pressure sensor 5 and a second air pressure and flow control valve 6.

[0092] The air inlet of the first cylinder 4 is connected to the air pump 1 through the first air pressure and flow control valve 3, and the first air pressure sensor 2 is installed on the air pump 1.

[0093] The first air pressure sensor 2, the first air pressure flow control valve 3, the second air pressure sensor 5, the second air pressure flow control valve 6, the third air pressure flow control valve 7, and the fifth air pressure flow control valve 11 are all connected to the control and display unit.

[0094] The control and display unit includes a controller 15 and a computer 16, which monitors and controls the air pressure in the first cylinder 4, the second cylinder 8, the third cylinder 12, the first standard instrument pressure tank 26, and the second standard instrument pressure tank 32. At the same time, the control and display unit also monitors and controls the temperature of the second cylinder 8, the third cylinder 12, the first standard instrument pressure tank 26, and the second standard instrument pressure tank 32 in real time, as well as the angles of the first piezoelectric ceramic support 41 and the second piezoelectric ceramic support 42.

[0095] The hollow cathode lamp 17 is capable of emitting the operating wavelength required by the first etalon 27 and the second etalon 29.

[0096] The first photodetector 23 is used to monitor the light signals transmitted through the first etalon 27 and the second etalon 29 to optimize the working air pressure and temperature of the first etalon 27 and the second etalon 29, as well as the angles of the first piezoelectric ceramic support 41 and the second piezoelectric ceramic support 42, so as to ensure the maximum transmittance of the first etalon 27 and the second etalon 29 for a specific wavelength. During the optimization of the maximum transmittance of the first etalon 27 and the second etalon 29, the variable aperture 35 is in the closed state. In the prior art, calibration is generally performed offline. In this invention, calibration is performed in situ. During calibration, the external signal light needs to be disconnected. When the ultra-narrow band filter is optimized to the maximum transmittance, the variable aperture 35 is opened to receive the external signal. At this time, the hollow cathode lamp 17 is turned off to eliminate the interference of the hollow cathode lamp 17 on the external signal. Since this invention establishes the correlation between the detection light intensity and the compensation angle, the ultra-narrow band filter can be directly adjusted in real time without calibration light, without separating the testing and calibration as in the prior art. See Example 2 for the specific process.

[0097] The first etalon 27 and the second etalon 29 in the ultra-narrow band filter are generally combined. For example, one etalon has a transmission bandwidth of pm and the other has 4pm. Cascading these two together can achieve high background suppression, which is a common method.

[0098] Example 2:

[0099] An in-situ calibration method for an absolute frequency reference of an ultra-narrowband filter, utilizing the in-situ calibration device for an absolute frequency reference of an ultra-narrowband filter described in Example 1, mainly includes: absolute wavelength calibration of the hollow cathode lamp for the center transmission wavelength of the ultra-narrowband filter; precise temperature and pressure control of the ultra-narrowband filter; switching between the calibration optical path and the working optical path of the ultra-narrowband filter; a real-time mapping model for the center wavelength drift of the ultra-narrowband filter; and a time-division calibration method for the center transmission wavelength of the ultra-narrowband filter. The specific steps are as follows:

[0100] Step 1: Hollow cathode lamp absolute wavelength calibration standard center transmission wavelength:

[0101] An in-situ calibration device for an absolute frequency reference of an ultra-narrowband filter is constructed. The calibration light emitted by the hollow cathode lamp 17 passes through the first etalon 27 and the second etalon 29 and is detected and received by the first photodetector 23. The control and display unit adjusts the air pressure (i.e., the working air pressure of the first etalon 27 and the second etalon 29) in the first etalon pressure tank 26 and the second etalon pressure tank 32 respectively, so that the transmittance of the first etalon 27 and the second etalon 29 reaches its maximum at the working wavelength of the etalon. The specific process is as follows:

[0102] Step 1.1: Determine the working wavelengths of the first etalon 27 and the second etalon 29, and select the corresponding hollow cathode lamp 17 based on the working wavelengths of the etalons; build an in-situ calibration device for the absolute frequency reference of the ultra-narrow band filter; use the atomic or ion spectral lines emitted by the hollow cathode lamp 17 as calibration light, and after the calibration light is collimated by the beam collimator 20, filter it with a corresponding narrow band filter 28 with a bandwidth of 1nm;

[0103] Step 1.2: Set the working temperature of the first standard fixture 27 (i.e., the temperature inside the first standard fixture pressure tank 26) through the control display unit. The operating temperature of the second standard fixture 29 (i.e., the temperature inside the second standard fixture pressure tank 32). , Indicates the maximum temperature deviation. The operating temperature at the center of the first standard fixture. The center operating temperature of the second standard etalon, in this embodiment , ;

[0104] Step 1.3: Gradually optimize the air pressure in the first standard pressure vessel 26 and the second standard pressure vessel 32 to maximize the strength of the test electrical signal output by the first photodetector 23; and record the working air pressure values ​​of the first standard vessel 27 and the second standard vessel 29 (i.e., the air pressure in the first standard pressure vessel 26 and the second standard pressure vessel 32) when the strength of the test electrical signal output by the first photodetector 23 is maximized. The specific steps are as follows:

[0105] Step 1.3.1: Remove the second standard etalon 29 from the optical path, turn on the air pump 1 to gradually adjust the air pressure of the first standard etalon pressure tank 26, observe the intensity change of the test electrical signal output by the first photodetector 23, find the air pressure inside the first standard etalon pressure tank 26 corresponding to the maximum intensity of the test electrical signal output by the first photodetector 23 after the internal thermal equilibrium is reached, and record it as the optimal air pressure value of the first standard etalon pressure tank. At this point, the test light passes only through the first etalon 27 in the ultra-narrowband filter;

[0106] Step 1.3.2: Keeping the pressure value of the first standard pressure vessel 26 unchanged, move the second standard 29 into the optical path, and gradually adjust the pressure of the second standard pressure vessel 32. Find the pressure inside the second standard pressure vessel 32 corresponding to the maximum intensity of the test electrical signal output by the first photodetector 23 after the second standard pressure vessel 32 reaches thermal equilibrium. Record this as the optimal pressure value of the second standard pressure vessel. At this point, the test light passes sequentially through the first etalon 27 and the second etalon 29.

[0107] Close the eighth pressure flow control valve 22 and the tenth pressure flow control valve 31;

[0108] Step 2: Turn off the hollow cathode lamp 17, turn on the variable aperture 35 to allow the external signal light beam to enter the variable aperture 35, and perform constant temperature and pressure control on the ultra-narrow band filter. This mainly includes the following steps:

[0109] Step 2.1: Adjust air pump 1 through a feedback adjustment mechanism so that the pressure of air pump 1 and the first cylinder 4 is higher than the optimal air pressure value of the first standard pressure tank. The optimal pressure value of the second standard pressure vessel The maximum value is 50 kPa higher;

[0110] The controller 15 sets the temperatures of the second cylinder 8 and the third cylinder 12 to [specific values]. and ;

[0111] The controller 15 controls the air pressure and flow control valves (i.e., the first air pressure and flow control valve 3, the third air pressure and flow control valve 7, and the fifth air pressure and flow control valve 11) to make the pressures of the second cylinder 8 and the third cylinder 12 respectively. and In this embodiment, the pressure of the second cylinder 8 and the third cylinder 12 is controlled as follows: and ;

[0112] After the first cylinder 4, the second cylinder 8, the third cylinder 12, the first standard fixture 27, and the second standard fixture 29 have reached thermal equilibrium, the eighth air pressure and flow control valve 22 and the tenth air pressure and flow control valve 31 are opened respectively to slowly add air to the first standard fixture 27 and the second standard fixture 29. The opening time of each air pressure is 1ms. If the air pressure value exceeds the set value, the seventh air pressure and flow control valve 21 and the ninth air pressure and flow control valve 30 are controlled to release air. The opening time of each air pressure is 0.1ms.

[0113] Step 2.2: After the air pressure in the first standard pressure vessel 26 and the second standard pressure vessel 32 becomes constant, the eighth air pressure flow control valve 22, the tenth air pressure flow control valve 31, the seventh air pressure flow control valve 21, and the ninth air pressure flow control valve 30 are closed. Through the feedback adjustment mechanism of the controller 15, the pressure of the second cylinder 8 and the third cylinder 12 is continuously maintained at [specific values ​​to be filled in]. and :

[0114] When a decrease in air pressure is detected in the first standard pressure vessel 26 and the second standard pressure vessel 32 (e.g., air leakage in the sealed pressure environment), the controller 15 opens the eighth air pressure flow control valve 22 and the tenth air pressure flow control valve 31 until the pressures of the second cylinder 8 and the third cylinder 12 are respectively... and .

[0115] When the pressure values ​​of the first standard pressure vessel 26 and the second standard pressure vessel 32 are monitored to be lower than... or Then, the eighth air pressure and flow control valve 22, the tenth air pressure and flow control valve 31, the third air pressure and flow control valve 7 and the fifth air pressure and flow control valve 11 are opened, and air is added at intervals of 0.1ms until the required air pressure is reached.

[0116] Step 3: After the ultra-narrow band filter enters the working stage, record the parameters of the sensors (including the fifth pressure sensor 24, the first temperature control device 25, the first strain sensor 39, the second temperature control device 33, the sixth pressure sensor 34, and the second strain sensor 40) installed in the first standard pressure tank 26 and the second standard pressure tank 32, as well as the values ​​of the photodetectors (including the first photodetector 23 and the second photodetector 38) as reference parameters:

[0117] Recording of reference environmental parameters: Under the stable operating conditions in step 2, collect and record the reference parameters of the environment in which the first etalon 27 and the second etalon 29 are located:

[0118] Corresponding to the first standard fixture 27 (i.e., corresponding to the first standard fixture pressure vessel 26):

[0119] The first etalon reference pressure was collected by the fifth barometer sensor 24. The first temperature control device 25 collects the first standard reference temperature. ;

[0120] Corresponding to the second standard fixture 29 (i.e., corresponding to the second standard fixture pressure vessel 32):

[0121] The second etalon reference pressure collected by the sixth barometer 34 The second etalon reference temperature collected by the sixth barometer 34 ;

[0122] Reference strain state record:

[0123] The initial strain values ​​of the first strain sensor 39 and the second strain sensor 40 are collected and recorded as the reference values ​​of the first strain sensor, respectively. Second strain sensor reference value .

[0124] Reference relative transmitted light intensity record:

[0125] The intensity of the test light signal detected by the first photodetector 23 and the second photodetector 38 is collected respectively: denoted as the reference value of the first photodetector. Second photodetector reference value .

[0126] Step 4: Calibrate the center transmission wavelength of the etalon.

[0127] Although controlling temperature and pressure plays a role in maintaining the stable operation of the first etalon 27 and the second etalon 29, it is impossible to calibrate the working wavelength drift of the ultra-narrowband filter caused by the strain changes of the first etalon 27 and the second etalon 29 themselves in real time. On the other hand, temperature and pressure control inevitably has errors. This invention achieves the goal of maximizing the final transmittance without disconnecting the external signal light by dynamically mapping and compensating for environmental parameters and drift amount.

[0128] The main method involves monitoring the changes in air pressure and temperature of the first standard etalon pressure tank 26 and the second standard etalon pressure tank 32, reading the values ​​of the first strain sensor 39 and the second strain sensor 40, and establishing a mapping model between the changes in air pressure and temperature values ​​of the standard etalon pressure tanks, the strain sensor detection values, and the relative transmittance of the ultra-narrow band filter. Based on this mapping model, the angles of the first piezoelectric ceramic support 41 and the second piezoelectric ceramic support 42 are adjusted to ensure stable operation of the ultra-narrow band filter. The main steps are as follows:

[0129] Step 4.1 Mapping Model Establishment:

[0130] A mapping model for "environmental parameters - strain parameters - transmittance" is established as follows:

[0131] For the first standard etalon 27:

[0132] ;

[0133] For the second standard etalon 29:

[0134] ;

[0135] in:

[0136] and This is the angle adjustment value;

[0137] and This represents the change in air pressure. , ;

[0138] and The change in temperature , ;

[0139] and The change in strain , ;

[0140] , , Monitoring values ​​belonging to the first standard datum 27 during continuous operation:

[0141] As the first standard for monitoring air pressure,

[0142] The first standard is used to monitor temperature.

[0143] As the first standard for monitoring strain,

[0144] , , Monitoring values ​​belonging to the second standard datum 29 during continuous operation:

[0145] The second standard instrument is used to monitor air pressure.

[0146] The second standard is used to monitor temperature.

[0147] As a second standard for monitoring strain,

[0148] , , , Belongs to the The parameter correlation coefficient of a standard etalon is denoted as the parameter correlation coefficient. , , , :

[0149] Parameter correlation coefficient Characterizing the first The angle adjustment coefficient (unit: ° / Pa) corresponding to the unit air pressure deviation of the standard etalon (the unit of air pressure deviation is Pa).

[0150] Parameter correlation coefficient Characterizing the first Angle adjustment factor (unit: ° / ℃) corresponding to the unit temperature deviation of the standard etalon (the unit of temperature deviation is: °C).

[0151] Parameter correlation coefficient Characterizing the first The angle adjustment factor (unit: ° / με) corresponding to the unit strain deviation of the standard etalon (the unit of strain deviation is: με).

[0152] Parameter correlation coefficient Representation for the first Etameter, causing the change in relative transmittance When returning to the threshold range of relative transmittance change, the angle compensation correction value corresponding to the unit relative transmittance change;

[0153] The target relative transmittance deviation value (the relative transmittance change threshold range is -0.5% to +0.5%), i.e., the current change in relative transmittance. Deviation from the relative transmittance change threshold range (e.g., the current relative transmittance change) In this embodiment, the minimum transmittance deviation value is selected, so the target relative transmittance deviation value is... This indicates that the angle needs to be adjusted to make (reduced by 0.7%)

[0154] Relative transmittance change ;

[0155] This is the value monitored by the first detector.

[0156] This is the value monitored by the second detector.

[0157] The present invention splits the calibration light emitted from the hollow cathode lamp 17 and calculates the ratio of the light intensities of the two detectors in order to avoid the influence of fluctuations in the intensity of the calibration light itself on the experimental results.

[0158] Step 4.2: Monitoring and data collection of dynamic parameters related to the mapping model:

[0159] Under the isothermal and pressure control conditions in step 2, different pressure changes were simulated. , Changes at different temperatures , Different strain changes , In the case of relative transmittance change The angle adjustment required to return to ±0.5% is:

[0160] The first standard instrument monitors air pressure. The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain Classified into the control parameter group;

[0161] After the ultra-narrowband filter enters the normal operation phase, each parameter in the control parameter group is adjusted one by one, and the corresponding monitoring value of the first detector is collected. Second detector monitoring value ;

[0162] Corresponding to the current parameter group, adjust the angles of the first piezoelectric ceramic support 41 and the second piezoelectric ceramic support 42 so that the first detector monitoring value detected by the first photodetector 23 is... When the strength reaches its maximum, record the corresponding angle adjustment value of the first piezoelectric ceramic support 41. The angle adjustment value of the second piezoelectric ceramic support 42 .

[0163] Abnormal data filtering and preprocessing: The collected real-time data is preprocessed, including: outlier removal: The 3σ criterion (standard deviation multiple method) is used to filter out abnormal data caused by sensor interference and instantaneous electromagnetic noise (such as isolated data with single air pressure fluctuations exceeding ±5 Pa or temperature fluctuations exceeding ±1℃).

[0164] Data smoothing: smoothing the parameters in the preprocessed control parameter group and the monitored values ​​of the first detector. Angle adjustment value Angle adjustment value and the monitoring values ​​of the second detector A moving average method (with a window size of 5 data sets) was used for smoothing to reduce the impact of high-frequency noise on subsequent modeling; the monitoring values ​​of the first detector... The second detector's monitoring value Exponential smoothing (with a smoothing coefficient of 0.3) is used to preserve trend changes while suppressing instantaneous fluctuations.

[0165] In this embodiment, during the first 72 hours of continuous operation of the ultra-narrowband filter, the aforementioned real-time monitoring control parameter set and the monitoring values ​​of the first detector are continuously collected. The second detector's monitoring value Angle adjustment value Angle adjustment value Establish a sample database with a sample size that meets the following requirements: the range of environmental parameter variations must cover the extreme values ​​of actual working scenarios, and the range of strain value variations must cover the normal deformation range of the first piezoelectric ceramic support 41 and the second piezoelectric ceramic support 42 (e.g., strain monitoring of the first etalon). Second standard for strain monitoring Fluctuation ±20με), first detector monitoring value The variation covers a range of 1.5 times the allowable fluctuation threshold (e.g., the value monitored by the first detector). The sampling frequency is set to 1 time per second, with fluctuations of ±0.75%. This ensures the representativeness and coverage of the sample.

[0166] Step 4.3: Determine the parameter correlation coefficients in the mapping model:

[0167] In this embodiment, each set of control parameters and the corresponding monitoring values ​​of the first detector are... The second detector's monitoring value Angle adjustment value , Substituting the mapping model established in step 4.1, the parameter correlation coefficients in the mapping model are obtained by fitting using the least squares method. , , , Ensure that the calibration error is ≤0.0002 °.

[0168] In this embodiment, the angle adjustment value , It needs to be compared with the control parameter group and the corresponding monitoring value of the first detector. The second detector's monitoring value Frequency synchronization (≥10Hz recommended) is necessary to avoid changes in relative transmittance due to calculation delays. Out of tolerance;

[0169] Furthermore, during the subsequent operation of the ultra-narrowband filter, steps 4.2 to 4.3 are executed every 24 hours (data integrity must be ≥95%) to transmit the newly acquired valid data (control parameter group and corresponding first detector monitoring value). The second detector's monitoring value Angle adjustment value , Using this as sample data, we continue to iteratively train and update the parameters of the mapping model to avoid the impact of factors such as sensor aging and structural deformation caused by long-term use on the model's accuracy and ensure the model's dynamic adaptability.

[0170] Step 4.4: Dynamically compensate and control the angles of the first piezoelectric ceramic support 41 and the second piezoelectric ceramic support 42 based on the mapping model:

[0171] Step 4.4.1: Continuously collect air pressure data from the first standard instrument. The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain First detector monitoring value The second detector's monitoring value ;

[0172] Based on the collected data, the first standard etalon was used to monitor air pressure. The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain First detector monitoring value The second detector's monitoring value Real-time calculation of the current relative transmittance change of the ultra-narrowband filter ;

[0173] When the relative transmittance changes Within the relative transmittance change threshold range, the current angles of the first piezoelectric ceramic support 41 and the second piezoelectric ceramic support 42 are maintained, and step 4.4.1 is repeated to continue monitoring parameters.

[0174] When the relative transmittance changes Exceeding the relative transmittance change threshold range (i.e.) )hour:

[0175] If the number of consecutive compensations performed is less than the preset number (e.g., the preset number is 3 times in this embodiment), the compensation control process is triggered, and step 4.4.2 is executed.

[0176] If the number of times the compensation has been performed consecutively is equal to the preset number, return to step 1 to recalibrate;

[0177] Step 4.4.2, Compensation Calculation: Calculate the current real-time monitoring pressure of the first standard etalon. The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain First detector monitoring value The second detector's monitoring value Input the established mapping model and solve for the angle adjustment value in reverse. , Even the change in relative transmittance The angle adjustment value required to return to the transmittance change threshold range (angle accuracy must be controlled within ±0.001°).

[0178] A) Regarding the angle adjustment value The specific calculation steps are as follows:

[0179] In this embodiment, "current air pressure change" is used. Temperature change strain change Current relative transmittance change (Relative transmittance change) It needs to be adjusted to ≤0.5%, which is the target light intensity deviation value. Taking ")" as an example, assuming the parameter correlation coefficients have been calibrated Parameter correlation coefficient Parameter correlation coefficient Parameter correlation coefficient The calculation process is as follows:

[0180] Step a1: Calculate the angular contribution of each item.

[0181] The angular amount of contribution from air pressure deviation: ,

[0182] The angular amount of contribution from temperature deviation: ,

[0183] Angular quantity of strain deviation contribution: ,

[0184] Light intensity correction angle: ,

[0185] (The negative sign indicates that the direction of angle adjustment is opposite to the "direction of angle offset caused by parameter deviation", and is used to cancel the deviation).

[0186] Step a2: Overlay calculation of angle adjustment value And calibrate the accuracy:

[0187] ,

[0188] Calibration accuracy: It is necessary to confirm whether the calculation result meets the accuracy requirement of ±0.001° (0.0006° in this example meets the requirement; if the result is out of tolerance, the calibration accuracy of the parameter correlation coefficient needs to be re-verified).

[0189] B) Regarding the angle adjustment value Detailed calculation steps:

[0190] Angle adjustment value Calculation logic and angle adjustment value Consistency requires additional consideration of "with". "Synergy", the steps are as follows:

[0191] In this embodiment, step 4.3 has calibrated the parameter correlation coefficients. Parameter correlation coefficient Parameter correlation coefficient Parameter correlation coefficient Current air pressure change Temperature change strain change Target light intensity deviation value (with angle adjustment value) (To ensure alignment of goals and collaboration).

[0192] Step b1: Calculate the angular contribution of each item.

[0193] Contribution of air pressure deviation: ,

[0194] Temperature deviation contribution: ,

[0195] Strain deviation contribution: ,

[0196] Light intensity correction contribution: ,

[0197] Step b2: Calculate the angle adjustment value And verify the synergy:

[0198] ;

[0199] Coordination verification: Confirm angle adjustment value (0.0006°) and angle adjustment value The adjustment direction (0.0004°) is consistent. In this embodiment, the compensation direction (i.e., the angle adjustment value) is... , Both the positive and negative signs indicate a positive direction, which meets the requirement of "jointly restoring the filter's transmittance". If the directions are opposite, the relative transmittance deviation of the target needs to be checked. (The sign or the direction of the parameter correlation coefficient).

[0200] Outlier handling: If the calculated angle adjustment value If the angle exceeds ±0.005° (beyond the effective adjustment range of the piezoelectric ceramic support), an alarm should be triggered. Prioritize checking whether the sensor is faulty or whether the mapping model coefficients are drifting.

[0201] Step 4.4.3, Compensation Execution:

[0202] Compensation Execution: Adjust the angle value according to the calculated value by controlling the display unit. , The angles of the first piezoelectric ceramic support 41 and the second piezoelectric ceramic support 42 are adjusted in steps (e.g., each step is adjusted by 0.0001° with an interval of 0.5 seconds) to avoid transmittance oscillations caused by excessive instantaneous adjustment.

[0203] Furthermore, in step 4.4.3, compensation records and status traceability are performed during the compensation execution process.

[0204] Compensation process log: After each execution of step 4.4.3, the following information is automatically recorded in the device log:

[0205] Compensation trigger time, first detector monitoring value at the time of triggering The second detector's monitoring value Real-time parameters before compensation (monitored air pressure of the first standard etalon) The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain ); Calculated angle adjustment value , and adjustment steps; the amount of relative transmittance change after compensation. The results of step 4.4.4 are used to determine the transmittance recovery time (the average time from trigger compensation to stable recovery should be ≤10 seconds). The parameters of the mapping model or the monitoring position of the sensor are optimized by analyzing the results to further improve long-term stability.

[0206] Furthermore, periodically check whether the first etalon 27 and the second etalon 29 are at the maximum transmission spectrum peak of the working wavelength, and perform a time-division calibration method for the center transmission wavelength of the etalons. The main methods and steps are as follows:

[0207] At each preset inspection cycle, the variable aperture 35 is closed and the hollow cathode lamp 17 is turned on.

[0208] The environmental parameter-drift dynamic mapping and compensation method described in step 4.4 is used to compensate for the transmittance of the ultra-narrowband filter in order to maintain the transmittance of the ultra-narrowband filter constant.

[0209] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. An in-situ calibration device for an absolute frequency reference of an ultra-narrowband filter, characterized in that, The system includes a hollow cathode lamp (17), the output of which is connected to one input of a split-to-two fiber (19) via a beam coupling device (18), and the output of a variable aperture (35) is connected to the other input of the split-to-two fiber (19) via an optical fiber. The beam output from the split-to-two fiber (19) is split into a first beam and a second beam. The first beam is input to a second photodetector (38) and converted into a corresponding electrical signal, which is then transmitted to the control and display unit. The second beam passes through a beam collimator (20) and a narrowband filter (28) in sequence, and then passes through the first etalon (27) and the second etalon (29) in the ultra-narrowband filter in sequence. The first photodetector (23) converts the beam into a corresponding electrical signal, which is then transmitted to the control and display unit. The first standard fixture (27) is installed inside the first standard fixture pressure tank (26). The first standard fixture (27) is equipped with a first strain sensor (39) and a first piezoelectric ceramic support (41). The first standard fixture pressure tank (26) is also equipped with a fifth pressure sensor (24) and a first temperature control device (25). The first strain sensor (39), the first piezoelectric ceramic support (41), the fifth pressure sensor (24) and the first temperature control device (25) are all connected to the control and display unit. The second standard fixture (29) is installed inside the second standard fixture pressure tank (32). The second standard fixture (29) is equipped with a second strain sensor (40) and a second piezoelectric ceramic support (42). The second standard fixture pressure tank (32) is also equipped with a second temperature control device (33) and a sixth pressure sensor (34). The second strain sensor (40), the second piezoelectric ceramic support (42), the second temperature control device (33) and the sixth pressure sensor (34) are all connected to the control and display unit.

2. The in-situ calibration device for an absolute frequency reference of an ultra-narrowband filter according to claim 1, characterized in that, The first standard pressure vessel (26) is equipped with a seventh pressure flow control valve (21) for controlling the outlet air and an eighth pressure flow control valve (22) for controlling the inlet air. The eighth pressure flow control valve (22) is connected to the outlet of the third cylinder (12). The third cylinder (12) is equipped with a fourth pressure sensor (13) and a sixth pressure flow control valve (14). The seventh pressure flow control valve (21), the eighth pressure flow control valve (22), the fourth pressure sensor (13), and the sixth pressure flow control valve (14) are all connected to the control display unit. The third cylinder (12) is equipped with a fourth temperature control device (37). The control port of the fourth temperature control device (37) is connected to the control display unit. The second standard pressure tank (32) is equipped with a ninth pressure flow control valve (30) for controlling the outlet air and a tenth pressure flow control valve (31) for controlling the inlet air. The tenth pressure flow control valve (31) is connected to the outlet of the second cylinder (8). The second cylinder (8) is equipped with a third pressure sensor (9) and a fourth pressure flow control valve (10). The ninth pressure flow control valve (30), the tenth pressure flow control valve (31), the third pressure sensor (9) and the fourth pressure flow control valve (10) are connected to the control display unit. The second cylinder (8) is equipped with a third temperature control device (36). The control port of the third temperature control device (36) is connected to the control display unit.

3. The in-situ calibration device for an absolute frequency reference of an ultra-narrowband filter according to claim 2, characterized in that, The air inlet of the second cylinder (8) is connected to the first cylinder (4) through the third air pressure and flow control valve (7); The air inlet of the third cylinder (12) is connected to the first cylinder (4) through the fifth air pressure flow control valve (11); the first cylinder (4) is equipped with a second air pressure sensor (5) and a second air pressure flow control valve (6). The air inlet of the first cylinder (4) is connected to the air pump (1) through the first air pressure flow control valve (3), and the first air pressure sensor (2) is installed on the air pump (1). The first air pressure sensor (2), the first air pressure flow control valve (3), the second air pressure sensor (5), the second air pressure flow control valve (6), the third air pressure flow control valve (7), and the fifth air pressure flow control valve (11) are all connected to the control and display unit.

4. An in-situ calibration method for an absolute frequency reference of an ultra-narrowband filter, utilizing the in-situ calibration device for an absolute frequency reference of an ultra-narrowband filter as described in claim 3, characterized in that... Specifically, the steps include the following: Step 1: Build an in-situ calibration device for an absolute frequency reference of an ultra-narrow band filter. The calibration light emitted by the hollow cathode lamp (17) is detected and received by the first photodetector (23) after passing through the first etalon (27) and the second etalon (29). The control display unit adjusts the air pressure in the first etalon pressure tank (26) and the second etalon pressure tank (32) respectively, so that the transmittance of the first etalon (27) and the second etalon (29) reaches the maximum at the working wavelength of the etalon. Step 2: Turn off the hollow cathode lamp (17), turn on the variable aperture (35) so that the beam of external signal light enters the variable aperture (35), and perform constant temperature and pressure control on the ultra-narrow band filter. Step 3: After the ultra-narrow band filter enters the working stage, record the acquisition parameters of the sensors installed in the first standard etalon pressure tank (26) and the second standard etalon pressure tank (32) as the reference parameters. Step 4: Monitor the changes in air pressure and temperature of the first standard etalon pressure tank (26) and the second standard etalon pressure tank (32), read the values ​​of the first strain sensor (39) and the second strain sensor (40), and establish a mapping model between the changes in air pressure and temperature of the standard etalon pressure tank, the detection values ​​of the strain sensors and the relative transmittance of the ultra-narrow band filter based on the reference parameters; according to the mapping model, adjust the angles of the first piezoelectric ceramic support (41) and the second piezoelectric ceramic support (42) to keep the ultra-narrow band filter working stably.

5. The in-situ calibration method for an absolute frequency reference of an ultra-narrowband filter according to claim 4, characterized in that, Step 1 includes the following steps: Step 1.1: Determine the working wavelengths of the first etalon (27) and the second etalon (29), and select the corresponding hollow cathode lamp (17) based on the working wavelengths of the etalon; build the in-situ calibration device for the absolute frequency reference of the ultra-narrow band filter. Step 1.2: Set the temperature inside the first standard pressure vessel (26) via the control display unit. Temperature inside the second standard pressure vessel (32) , Indicates the maximum temperature deviation. The operating temperature at the center of the first standard fixture. The center operating temperature of the second standard fixture; Step 1.3: Gradually optimize the air pressure in the first standard etalon pressure tank (26) and the second standard etalon pressure tank (32) so that the strength of the test electrical signal output by the first photodetector (23) is maximized; and record the air pressure in the first standard etalon pressure tank (26) and the second standard etalon pressure tank (32) when the strength of the test electrical signal output by the first photodetector (23) is maximized.

6. The in-situ calibration method for an absolute frequency reference of an ultra-narrowband filter according to claim 5, characterized in that, The data acquisition parameters of the sensors installed in the first standard pressure vessel (26) and the second standard pressure vessel (32) in step 3, as well as the detection values ​​of the photoelectric detector, specifically include: The first etalon reference pressure is collected by the fifth bar sensor (24). The first temperature control device (25) collects the first standard reference temperature. The initial strain value of the first strain sensor (39) is recorded as the reference value of the first strain sensor. ; The second etalon reference pressure is collected by the sixth barometer (34). The second etalon reference temperature collected by the sixth barometer (34) The initial strain value of the second strain sensor (40) is recorded as the reference value of the second strain sensor. ; The intensity of the test light signal detected by the first photodetector (23) is recorded as the reference value of the first photodetector. , The intensity of the reference light signal detected by the second photodetector (38) is denoted as the reference value of the second photodetector. .

7. The in-situ calibration method for an absolute frequency reference of an ultra-narrowband filter according to claim 6, characterized in that, The mapping model is as follows: For the first standard etalon (27): ； For the second standard etalon (29): ； in: and This is the angle adjustment value; and This represents the change in air pressure. , ; and The change in temperature , ; and The change in strain , ; , , Monitoring values ​​belonging to the first standard fixture (27) during continuous operation: As the first standard for monitoring air pressure, The first standard is used to monitor temperature. As the first standard for monitoring strain, , , Monitoring values ​​belonging to the second standard fixture (29) during continuous operation: The second standard instrument is used to monitor air pressure. The second standard is used to monitor temperature. As a second standard for monitoring strain, , , , Belongs to the The parameter correlation coefficient of a standard etalon is denoted as the parameter correlation coefficient. , , , : Parameter correlation coefficient Characterizing the first Angle adjustment coefficient corresponding to unit air pressure deviation of the standard tassel; Parameter correlation coefficient Characterizing the first Angle adjustment factor corresponding to unit temperature deviation of standard etalon; Parameter correlation coefficient Characterizing the first Angle adjustment factor corresponding to unit strain deviation of standard etalon; Parameter correlation coefficient Representation for the first Etameter, causing the change in relative transmittance When returning to the threshold range of relative transmittance change, the angle compensation correction value corresponding to the unit relative transmittance change; The target relative transmittance deviation value represents the current change in relative transmittance. The deviation value within the relative transmittance change threshold range; Relative transmittance change ; This is the value monitored by the first detector. This is the value monitored by the second detector.

8. The in-situ calibration method for an absolute frequency reference of an ultra-narrowband filter according to claim 7, characterized in that, The parameter correlation coefficients in the mapping model in step 4 are determined through the following steps: The first standard instrument monitors air pressure. The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain Classified into the control parameter group; After the ultra-narrowband filter enters the normal operation phase, each parameter in the control parameter group is adjusted one by one, and the corresponding monitoring value of the first detector is collected. Second detector monitoring value ; Corresponding to the current parameter group, adjust the angles of the first piezoelectric ceramic support (41) and the second piezoelectric ceramic support (42) so that the first detector monitoring value detected by the first photodetector (23) is... When the strength reaches its maximum, record the angle adjustment value corresponding to the first piezoelectric ceramic support (41). The angle adjustment value of the second piezoelectric ceramic support (42) ; Each set of control parameters and the corresponding first detector monitoring value I 1t The second detector's monitored value I 2t Angle adjustment value , Substituting the mapping model established in step 4.1, the parameter correlation coefficients in the mapping model are obtained by fitting using the least squares method. , , , .

9. The in-situ calibration method for an absolute frequency reference of an ultra-narrowband filter according to claim 7, characterized in that, In step 4, the angles of the first piezoelectric ceramic support (41) and the second piezoelectric ceramic support (42) are adjusted according to the mapping model, specifically including the following process: Step 4.4.1: Continuously collect air pressure data from the first standard instrument. The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain First detector monitoring value The second detector's monitoring value ; It also calculates the current relative transmittance change of the ultra-narrowband filter in real time. ; When the relative transmittance changes When the relative transmittance change exceeds the threshold range: If the number of consecutive compensation operations is less than the preset number, proceed to step 4.4.2; If the number of times the compensation has been performed consecutively is equal to the preset number, then return to step 1; Step 4.4.2: Set the current real-time monitoring of the first standard datum pressure. The first standard instrument for monitoring temperature The first standard instrument for monitoring strain Second standard instrument for monitoring air pressure The second standard instrument monitors the temperature. Second standard instrument for monitoring strain First detector monitoring value The second detector's monitoring value Input the established mapping model and solve for the angle adjustment value in reverse. , ; Step 4.4.3: Adjust the angle according to the calculated value by controlling the display unit. , The angles of the first piezoelectric ceramic support (41) and the second piezoelectric ceramic support (42) are adjusted.

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