All-fiber extended-range frequency domain interference ranging method and device based on optical microwave mapping

Abstract

The invention discloses an all-fiber extended-range frequency domain interference ranging method and device based on optical microwave mapping, the method is used for measuring the distance information of a to-be-measured target, and the method comprises the steps: S1, transmitting a broadband spectrum to a ranging probe, and enabling the ranging probe to divide the broadband spectrum into a reference light beam and a signal light beam; s2, the distance measuring probe sends a signal light beam to a to-be-measured target, receives the reflected signal light beam, and couples the reflected signal light beam with the reference light beam to form an interference signal; s3, analyzing the interference signal to obtain distance information with the to-be-measured target; the device is used for measuring the distance of a to-be-measured target. The invention has the advantages of simple structure, long measuring range and micron-order precision.

Description

Technical Field

[0001] The present invention relates to the field of optical ranging technology, and in particular to an all-fiber extended-range frequency domain interferometry ranging method and device based on optical microwave mapping. Background Art

[0002] Optical interferometry technology is widely used in fields such as spatial distance measurement, thin film thickness measurement, workpiece precision machining, and displacement machinery precision control due to its advantages such as high precision, strong anti-interference ability, and applicability to complex environments.

[0003] Currently, many ranging technologies based on optical interferometry have been proposed, such as laser heterodyne interferometry, frequency-modulated continuous wave (FMCW) ranging, and broadband optical interferometry. Laser heterodyne interferometry measures the frequency or phase changes of Doppler-shifted signals caused by displacement changes. In recent years, the use of nonlinear phase compensation, improved signal processing circuits, and electronic subdivision has enabled displacement measurement with a resolution of tens to hundreds of picometers over a range of several hundred millimeters. However, laser heterodyne interferometry cannot interrupt fringe counting during the measurement process, making absolute distance measurement impossible. FMCW ranging, by measuring the frequency difference between the emitted and reflected frequency-modulated laser light, can achieve precise distance measurement down to the micrometer level within a meter-scale range. When high-precision ranging is required, the wide bandwidth and high linearity of the light source lead to high cost and complex structure. Furthermore, key technologies such as frequency-sweep nonlinearity correction and spectrum analysis also affect the ranging range and accuracy, increasing the complexity of system design. For optical frequency-domain interferometry ranging methods based on spectrometers, the superposition of light waves with different optical paths forms interference fringes that can be used to analyze distance information. Currently, the engineering measurement range can reach 17 cm, and ranging accuracy can reach the micron level. Because the period of the interference fringes is inversely proportional to the measured distance, and the resolution bandwidth of a spectrometer is generally 0.02 nm, this limits the theoretical measurement range to 24 cm. For longer distances, the spectrometer cannot recognize and record a complete period. Improving the resolution bandwidth of optical instruments is a high requirement, limiting the range expansion in engineering applications. To date, optical absolute distance measurement technologies with simple structures, long ranges, and micron-level accuracy remain one of the most pressing frontiers in this field. Summary of the Invention

[0004] The purpose of the present invention is to provide an all-fiber extended-range frequency domain interferometry ranging method and device based on optical microwave mapping, which has the advantages of simple structure, long range and micron-level accuracy.

[0005] To achieve the above objectives, the present invention provides an all-fiber extended-range frequency-domain interferometry ranging method based on optical microwave mapping, which is used to measure the distance information of a target to be measured. The method comprises: step S1, transmitting a broadband spectrum to a ranging probe, which separates the broadband spectrum into a reference beam and a signal beam; step S2, the ranging probe transmitting a signal beam to the target to be measured, receiving the reflected signal beam, and coupling it with the reference beam to form an interference signal; and step S3, analyzing the interference signal to obtain distance information to the target to be measured.

[0006] Preferably, the step S1 includes: step S11, sending a broadband spectrum to the ranging probe to obtain the reference beam intensity at time t and the signal beam intensity at time t ;

[0007]

[0008]

[0009] in, is the total intensity of the broadband spectrum at time t; A is the percentage of the reference beam to the total intensity of the broadband spectrum; B is the percentage of the signal beam to the total intensity of the broadband spectrum; For time delay.

[0010] Step S12, obtaining the reference beam electric field signal and the electric field signal of the signal beam ;

[0011]

[0012]

[0013] in, is the electric field signal of the broadband spectrum at time t;

[0014] Preferably, the step S2 includes: step S21, the ranging probe sends a signal beam to the target to be measured, and receives the reflected signal beam, couples it with the reference beam to form an interference signal, and obtains a time domain interference signal ;

[0015]

[0016] Step S22: Time domain interference signal Perform Fourier transform to obtain frequency domain interference signal ;

[0017]

[0018] in, is the frequency of light.

[0019] Preferably, the step S3 includes: step S31, performing photoelectric detector analysis on the time domain interference signal, and the current expression for:

[0020]

[0021] in, represents the DC term of the photocurrent at time t; represents the interference signal term of the photocurrent at time t; Represents the responsivity of the photodetector;

[0022] Step S32, obtaining spectral density ;

[0023]

[0024] in, is the spectrum intensity of the broadband spectrum;

[0025] Step S33, obtaining current spectrum density ;

[0026]

[0027] ,

[0028] in, is the effective bandwidth of the photodetector; Represents the phase shift of the sinusoidal interference signal;

[0029] Step S34, verifying the current spectrum density and spectral density Does the self-convolution satisfy: ; If satisfied, proceed to step S35; if not satisfied, return to step S1;

[0030] Step S35, according to , get the distance to be measured ;

[0031] in, The speed of light.

[0032] An all-fiber extended-range frequency domain interferometry ranging device based on optical microwave mapping, the device is used to implement the aforementioned all-fiber extended-range frequency domain interferometry ranging method based on optical microwave mapping; the device is used to measure the distance of a target to be measured, the device comprising: a light source transmitter for emitting a broadband spectrum; a fiber optic circulator, connected to the light source transmitter, receiving and transmitting the broadband spectrum from the light source transmitter; a ranging probe, connected to the fiber optic circulator, receiving the broadband spectrum from the fiber optic circulator; a first broadband spectrum forms a reference beam inside the ranging probe, a second broadband spectrum is emitted toward the target to be measured, and a signal beam reflected from the target to be measured is received; the reference beam and the signal beam are coupled inside the ranging probe to form an interference signal, which is transmitted to the fiber optic circulator; an analysis module, connected to the fiber optic circulator, receiving and analyzing the interference signal from the fiber optic circulator to obtain the distance to be measured.

[0033] Preferably, the ranging probe consists of a single-mode optical fiber, a focusing lens and a metal casing; when the broadband spectrum enters the single-mode optical fiber of the ranging probe through a fiber circulator, due to the Fresnel effect, the broadband spectrum is reflected at the end face of the single-mode optical fiber and serves as a reference beam.

[0034] Preferably, the analysis module includes: a photodetector connected to the optical fiber circulator, receiving the interference signal from the optical fiber circulator, performing photodetector analysis on the interference signal to obtain a converted interference signal; a spectrum analyzer connected to the photodetector, receiving the converted interference signal and performing spectral density analysis and current spectral density analysis on it; a computer connected to the spectrum analyzer, receiving the spectral density analysis results and the current spectral density analysis results, and then calculating the distance information.

[0035] Preferably, the optical fiber circulator includes: a first port, connected to the light source transmitter, receiving a broadband spectrum; a second port, connected to the first port, connected to the ranging probe, transmitting the broadband spectrum to the ranging probe, and receiving an interference signal; a third port, connected to the first port and the second port, connected to the photodetector, receiving the interference signal and transmitting it to the photodetector.

[0036] In summary, compared with the prior art, the all-fiber extended-range frequency domain interferometry ranging method and device based on optical microwave mapping provided by the present invention has the following beneficial effects:

[0037] First, the present invention overcomes in principle the limitations on the measurement range caused by factors such as the resolution bandwidth of the spectrometer in traditional optical ranging technology.

[0038] Second, the technology described in this patent enables high-precision absolute distance measurement over a wide range without the need for additional precision optical components. Compared to distance measurement methods such as femtosecond lasers or optical frequency combs, the system is simpler, less expensive, and easier to build.

[0039] Third, the present invention only uses a simple FFT (Fast Fourier Transform) to process the frequency domain signal, and the signal-to-noise ratio of the interference pattern is low, which is suitable for complex engineering environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is an all-fiber extended-range frequency domain interferometry ranging device based on optical microwave mapping proposed by the present invention.

[0041] Figure 2 These are the interference fringes stored by two instruments in an embodiment of the present invention.

[0042] Figure 3 These are the frequency domain interference fringes obtained in the 5.08 m range in an embodiment of the present invention.

[0043] Figure 4 The data shown in FIG1 are the results of 100 measurements of the target object in an embodiment of the present invention.

[0044] Figure 5 This is a flow chart of the all-fiber extended-range frequency domain interferometry ranging method based on optical microwave mapping proposed in the present invention.

[0045] Reference numerals:

[0046] 101 - light source transmitter, 102 - fiber optic circulator, 103 - ranging probe, 104 - photoelectric detector, 105 - spectrum analyzer, 106 - computer, 107 - target to be measured, 1 - first port, 2 - second port, 3 - third port. DETAILED DESCRIPTION

[0047] The following will be combined with the appended Figure 1 ~Attached Figure 5 , the technical solutions, structural features, objectives achieved and effects in the embodiments of the present invention are described in detail.

[0048] It should be noted that the drawings are in a very simplified form and use non-precise proportions. They are only used to conveniently and clearly assist in explaining the embodiments of the present invention, and are not used to limit the conditions for the implementation of the present invention. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0049] It should be noted that, in the present invention, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only the elements explicitly listed, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0050] The present invention proposes an all-fiber extended-range frequency domain interferometry ranging method and device based on optical microwave mapping. Figure 5 As shown, the method is used to measure the distance information of the target to be measured, and the method includes:

[0051] Step S1, sending a broadband spectrum to a ranging probe, wherein the ranging probe divides the broadband spectrum into a reference beam and a signal beam;

[0052] The reference beam is the beam generated by the reflection of the broadband spectrum into the ranging probe due to the Fresnel effect. The signal beam is the beam sent toward the target after the broadband spectrum enters.

[0053] Step S2: The ranging probe sends a signal beam to the target to be measured, receives the reflected signal beam, and couples it with the reference beam to form an interference signal;

[0054] Step S3: Analyze the interference signal to obtain the distance information to the target to be measured.

[0055] Specifically, step S1 includes:

[0056] Step S11: Send a broadband spectrum to the ranging probe to obtain the reference beam intensity at time t and the signal beam intensity at time t ;

[0057]

[0058]

[0059] in, is the total intensity of the broadband spectrum at time t; A is the percentage of the reference beam in the total intensity of the broadband spectrum; B is the percentage of the signal beam in the total intensity of the broadband spectrum; the signal beam will have a time delay because its optical path is one more distance to be measured than the reference beam. .

[0060] Step S12, obtaining the reference beam electric field signal and the electric field signal of the signal beam ;

[0061]

[0062]

[0063] in, is the electric field signal of the broadband spectrum at time t.

[0064] Specifically, step S2 includes:

[0065] Step S21: The ranging probe sends a signal beam to the target to be measured, receives the reflected signal beam, couples it with the reference beam to form an interference signal, and obtains a time domain interference signal. ;

[0066]

[0067] Step S22: Time domain interference signal Perform Fourier transform to obtain frequency domain interference signal ;

[0068]

[0069] in, is the frequency of light.

[0070] Specifically, step S3 includes:

[0071] Step S31, perform photodetector analysis on the time domain interference signal, and the current expression is for:

[0072]

[0073] in, represents the DC term of the photocurrent at time t; represents the interference signal term of the photocurrent at time t; Represents the responsivity of the photodetector;

[0074] Step S32, obtaining spectral density ;

[0075]

[0076] in, is the spectrum intensity of the broadband spectrum;

[0077] Step S33, obtaining current spectrum density ;

[0078]

[0079] ,

[0080] in, is the effective bandwidth of the photodetector; Represents the phase shift of the sinusoidal interference signal.

[0081] Step S34, verifying the current spectrum density and spectral density Does the self-convolution satisfy: ; If satisfied, proceed to step S35; if not satisfied, return to step S1;

[0082] The principle here is that if the current spectrum density and spectral density The current spectrum density function after photoelectric conversion is proportional to the self-convolution of The effective response range of the photodetector is related to the spectral density function Having the same periodicity, it illustrates the feasibility of converting light interference fringes into microwave interference fringes.

[0083] Step S35, according to , get the distance to be measured ;

[0084] in, The speed of light.

[0085] The above analysis demonstrates that frequency-domain interferometry absolute distance measurement based on optical-microwave mapping requires only a broadband frequency-domain interference spectrum. After photoelectric conversion, the inverse Fourier transform is used to determine the propagation time difference, allowing calculation of the absolute distance to the target. This demonstrates the feasibility of mapping the optical interference signal to the microwave frequency band for signal processing, provided that the current spectral density function (CSDF) carrying the distance information and the sinusoidal AC component of the CSDF have the same period.

[0086] In addition, the present invention also proposes an all-fiber extended-range frequency domain interferometry ranging device based on optical microwave mapping; the device is used to measure the distance of the target 107 to be measured, and the device includes:

[0087] A light source transmitter 101 is configured to emit a broadband spectrum;

[0088] The optical fiber circulator 102 is connected to the light source transmitter 101, receives the broadband spectrum from the light source transmitter 101, and transmits it;

[0089] The ranging probe 103 is connected to the fiber circulator 102 and receives a broadband spectrum from the fiber circulator 102. The first broadband spectrum forms a reference beam within the ranging probe 103. The second broadband spectrum is emitted toward the target 107 to be measured and receives a signal beam reflected from the target 107. The reference beam and the signal beam are coupled within the ranging probe 103 to form an interference signal, which is then transmitted to the fiber circulator 102.

[0090] The analysis module is connected to the optical fiber circulator 102 , receives the interference signal from the optical fiber circulator 102 , and analyzes the interference signal to obtain the distance to be measured.

[0091] In a specific embodiment, the ranging probe 103 is composed of a single-mode optical fiber, a focusing lens, and a metal housing. When the broadband spectrum enters the single-mode optical fiber of the ranging probe 103 through the fiber circulator 102, it is reflected at the end face of the single-mode optical fiber due to the Fresnel effect and serves as a reference beam. The specific structure of the ranging probe 103 is conventional, and is sufficient to achieve the aforementioned technical effects, so it will not be described in detail here.

[0092] Specifically, the analysis module includes:

[0093] The photodetector 104 is connected to the optical fiber circulator 102, receives the interference signal from the optical fiber circulator 102, and analyzes the interference signal through the photodetector 104 to obtain a converted interference signal;

[0094] The spectrum analyzer 105 is connected to the photodetector 104, receives the converted interference signal and performs spectrum density analysis and current spectrum density analysis on it;

[0095] The computer 106 is connected to the spectrum analyzer 105 , receives the spectrum density analysis results and the current spectrum density analysis results, and then calculates and obtains the distance information.

[0096] At the same distance, after multiple verifications, the transmission time difference can be directly obtained by performing inverse Fourier transform on the interference signal in the photodetector 104 (equivalent to skipping the verification of the spectral density analysis results and the current spectral density analysis results), and then the distance information can be calculated.

[0097] Specifically, in a preferred embodiment, the optical fiber circulator 102 includes:

[0098] The first port 1 is connected to the light source transmitter 101 and receives a broadband spectrum;

[0099] The second port 2 is communicated with the first port 1 and connected to the ranging probe 103, transmits a broadband spectrum to the ranging probe 103, and receives an interference signal;

[0100] The third port 3 is communicated with the first port 1 and the second port 2 , is connected to the photodetector 104 , receives the interference signal and transmits it to the photodetector 104 .

[0101] By distributing three ports in the optical fiber circulator 102 , independent operation of the ports and components is achieved, thereby reducing the impact of optical transmission between them.

[0102] The following are specific examples.

[0103] Since the resolution bandwidth of spectrum analyzer 105 in this system is 1 MHz within a 20 GHz passband, significantly higher than the 0.62 GHz resolution bandwidth of fiber spectrometers used in previous studies, spectrum analyzer 105 has a minimum resolution bandwidth of 1 Hz, theoretically increasing the ranging range to over hundreds of thousands of kilometers. Furthermore, measurement accuracy depends on the interference spectrum signal-to-noise ratio and the accuracy of the inverse Fourier transform. The optimal signal-to-noise ratio is achieved when the power ratio of the reference beam to the signal beam is equal. When the inverse Fourier transform calculation length reaches 226, micron-level measurement accuracy can be achieved. This achieves an expansion of the measurement range by several orders of magnitude while maintaining micron-level ranging accuracy.

[0104] Based on the device, Figure 1 The structure shown is used as an example to illustrate the preferred embodiment. The broadband spectrum used in the figure utilizes an EDFA (Erbium-Doped Fiber Amplifier) ​​fiber amplifier. The ASE light source (Amplified Spontaneous Emission Source) passes through the first and second ports 1 and 2 of a fiber circulator 102, followed by a ranging probe 103. Through the Fresnel effect and optical frequency-domain interferometry, a broadband sinusoidal interference signal with a frequency of 192-196 THz is generated. This signal is then injected through the third port 3 of the fiber circulator 102 into a photodetector 104 with an effective bandwidth of 20 GHz. The fiber circulator 102 has a central wavelength of 1550 nm, a passband of 30 nm, an insertion loss of 1 dB, and an isolation of 52 dB. The ranging probe 103 is connected to a single-mode fiber with a numerical aperture of 0.14, a probe diameter of 12 mm, and an imaging focal length of 5 m. The target 107 to be measured is a 30 mm diameter silver-coated mirror. The microwave signal after photoelectric conversion is collected and recorded by a spectrum analyzer 105 with a frequency range of 10 Hz-30 GHz and a resolution bandwidth of 1 MHz. The measured distance is about 5 m.

[0105] In addition, at the same distance, after multiple verifications, after completing the conversion of optical frequency domain to microwave frequency domain distance measurement multiple times, the optical frequency domain interference fringes (spectral density) are recorded within the effective measurement range of the photodetector 104, and then the microwave frequency domain interference fringes (current spectrum density) are observed using the spectrum analyzer 105 while the distance to be measured remains unchanged. Figure 2 By comparing the interference fringes saved by the two instruments, it can be found that although the carrier frequencies of the fringes are different, the periods of the two cosine signals are exactly the same. This shows that within the effective working range of the photodetector, it is feasible to convert the interference signal from the optical frequency domain to the microwave frequency domain for fringe analysis.

[0106] The frequency domain interference fringes (current spectrum density) in the range of 5.08 m obtained in the experiment are as follows: Figure 3 The target object was measured 100 times, and the measurement results are shown as follows. Figure 4 As shown in Figure 2, the distance measurement accuracy at 5.08 m is calculated to be 6.4 µm.

[0107] In summary, it can be seen that the present invention, based on the principle of frequency domain interferometry, has built a simple and compact extended-range optical-microwave mapping absolute distance measurement device, which expands the measured range of the distance to be measured by 29.9 times while ensuring micron-level measurement accuracy.

[0108] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. An all-fiber extended-range frequency domain interferometry ranging method based on optical microwave mapping, characterized in that: The method is used to measure distance information of a target to be measured, and the method includes: Step S1, sending a broadband spectrum to a ranging probe, wherein the ranging probe divides the broadband spectrum into a reference beam and a signal beam; Step S2: The ranging probe sends a signal beam to the target to be measured, receives the reflected signal beam, and couples it with the reference beam to form an interference signal; Step S3: Analyze the interference signal to obtain the distance information to the target to be measured.

2. The all-fiber extended-range frequency domain interferometry ranging method based on optical microwave mapping according to claim 1 is characterized in that: The step S1 comprises: Step S11: Send a broadband spectrum to the ranging probe to obtain the reference beam intensity at time t and the signal beam intensity at time t ; in, is the total intensity of the broadband spectrum at time t; A is the percentage of the reference beam to the total intensity of the broadband spectrum; B is the percentage of the signal beam to the total intensity of the broadband spectrum; For time delay; Step S12, obtaining the reference beam electric field signal and the electric field signal of the signal beam ; in, is the electric field signal of the broadband spectrum at time t.

3. The all-fiber extended-range frequency domain interferometry ranging method based on optical microwave mapping according to claim 2 is characterized in that: The step S2 comprises: Step S21: The ranging probe sends a signal beam to the target to be measured, receives the reflected signal beam, couples it with the reference beam to form an interference signal, and obtains a time domain interference signal. ; Step S22: Time domain interference signal Perform Fourier transform to obtain frequency domain interference signal ; in, is the frequency of light.

4. The all-fiber extended-range frequency domain interferometry ranging method based on optical microwave mapping according to claim 3 is characterized in that: The step S3 comprises: Step S31, perform photoelectric detector analysis on the time domain interference signal, and the current expression is for: in, represents the DC term of the photocurrent at time t; represents the interference signal term of the photocurrent at time t; Represents the responsivity of the photodetector; Step S32, obtaining spectral density ; in, is the spectrum intensity of the broadband spectrum; Step S33, obtaining current spectrum density ; , in, is the effective bandwidth of the photodetector; Represents the phase shift of the sinusoidal interference signal; Step S34, verifying the current spectrum density and spectral density Does the self-convolution satisfy: ; If satisfied, proceed to step S35; if not satisfied, return to step S1; Step S35, according to , get the distance to be measured ; in, The speed of light.

5. An all-fiber extended-range frequency domain interferometry ranging device based on optical microwave mapping, characterized in that: The device is used to implement the all-fiber extended-range frequency domain interferometry ranging method based on optical microwave mapping as described in any one of claims 1 to 4 above; the device is used to measure the distance of a target (107) to be measured, and the device comprises: A light source emitter (101) for emitting a broadband spectrum; The optical fiber circulator (102) is connected to the light source transmitter (101), receives the broadband spectrum from the light source transmitter (101), and transmits it; A ranging probe (103) is connected to the optical fiber circulator (102) and receives a broadband spectrum from the optical fiber circulator (102); a first broadband spectrum forms a reference beam inside the ranging probe (103); a second broadband spectrum is emitted toward a target to be measured (107) and receives a signal beam reflected by the target to be measured (107); the reference beam and the signal beam are coupled inside the ranging probe (103) to form an interference signal, which is then transmitted to the optical fiber circulator (102); The analysis module is connected to the optical fiber circulator (102), receives the interference signal from the optical fiber circulator (102), and analyzes the interference signal to obtain the distance to be measured.

6. The all-fiber extended-range frequency domain interferometry ranging device based on optical microwave mapping according to claim 5 is characterized in that: The distance measuring probe (103) is composed of a single-mode optical fiber, a focusing lens, and a metal shell; when the broadband spectrum enters the single-mode optical fiber of the distance measuring probe (103) through the optical fiber circulator (102), the broadband spectrum is reflected at the end face of the single-mode optical fiber due to the Fresnel effect and serves as a reference beam.

7. The all-fiber extended-range frequency domain interferometry ranging device based on optical microwave mapping according to claim 6 is characterized in that: The analysis module includes: A photoelectric detector (104) is connected to the optical fiber circulator (102), receives an interference signal from the optical fiber circulator (102), and analyzes the interference signal using the photoelectric detector (104) to obtain a converted interference signal; A spectrum analyzer (105) is connected to the photodetector (104), receives the converted interference signal and performs spectrum density analysis and current spectrum density analysis on the interference signal; The computer (106) is connected to the spectrum analyzer (105), receives the spectrum density analysis result and the current spectrum density analysis result, and then calculates and obtains the distance information.

8. The all-fiber extended-range frequency domain interferometry ranging device based on optical microwave mapping according to claim 7 is characterized in that: The optical fiber circulator (102) comprises: The first port (1) is connected to the light source transmitter (101) and receives a broadband spectrum; The second port (2) is in communication with the first port (1), is connected to the ranging probe (103), transmits a broadband spectrum to the ranging probe (103), and receives an interference signal; The third port (3) is in communication with the first port (1) and the second port (2), is connected to the photoelectric detector (104), receives the interference signal and transmits it to the photoelectric detector (104).

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