Signal Scaling Synthesis Method for Dual Interference Channel Push-Pull Structure

Abstract

The present invention provides a signal scaling synthesis method for a dual interference channel push-pull structure, aiming to solve the problem of sensor signal synthesis using a dual interference channel push-pull structure. The present invention adopts a phase time domain signal scaling synthesis method with independent demodulation of dual interference channels, utilizes the signal phase inversion characteristics of the dual interference channels, and achieves doubling of the signal response amplitude by reasonably setting the scaling coefficient, while controlling the lifting level of the dual interference channel noise after mixing, and suppressing common mode noise. The present invention can overcome the imbalance problem of "push" and "pull" sensitivity of the dual interference channel, effectively increase the response sensitivity after synthesis, minimize the lifting effect of dual channel signal synthesis on the background noise, improve the sensing dynamic range, and eliminate the influence of common mode interference signals.

Description

Technical Field

[0001] The invention relates to the field of optical fiber sensing technology, in particular to a signal scaling synthesis method for a dual interference channel push-pull structure. Background Art

[0002] In systems where fiber interferometers are used as sensing units, push-pull is a commonly used sensing structure design and packaging method. In this sensing structure, external signals will cause the fiber interferometer to change in the phase difference between the two arms. When using a push-pull structure, the phase of one arm's transmission can increase under the action of external signals, while the other arm decreases synchronously, thus doubling the phase difference between the two arms and increasing the sensitivity by 1 times (6dB).

[0003] The push-pull fiber interferometer structure design has a wide range of applications in many sensing fields such as pressure, acceleration, seismic waves, and hydroacoustics. The patent application with publication number CN118169770A discloses a push-pull fiber optic geomagnetic measurement probe, device, and method. The patent application with publication number CN214310906U discloses a push-pull fiber optic hydrophone. The patent application with publication number CN112946729A discloses a cross-wound push-pull downhole three-component fiber optic seismometer. The patent application with publication number CN108663158A discloses a push-pull fiber optic differential pressure sensor. The document "Three-dimensional push-pull compliant cylinder interference acceleration sensing system (Optoelectronic Engineering, 2006, 33 (6))" discloses a three-dimensional push-pull compliant cylinder interference acceleration sensing system. The document "Experimental Research of an All-Polarization MaintainingOptical Fiber Vector Hydrophone (DOI: 10.1109 / JLT.2011.2170959)" discloses a method for manufacturing a push-pull optical fiber vector hydrophone and its performance indicators. The interferometer used in the push-pull structure usually includes two optical fiber arms, namely the signal arm and the reference arm. The two arms are respectively wound on the structural components corresponding to the "push" and "pull". The effect of doubling the sensitivity is directly reflected in the output of an interferometer, which is called a single interference channel push-pull structure.

[0004] In sensing, structures such as FP cavity and fiber laser resonant cavity are also often used. The characteristic of this structure is that it contains only one fiber arm, usually a signal arm. If the signal arm is directly wound around the structural components corresponding to the "push" and "pull", the sensing signal will be reduced or even completely offset due to the offset effect of push-pull. For this sensing application, the patent application with publication number CN103134581A discloses a method of winding the fiber laser resonant cavity around the "push" and "pull" structural components respectively. The patent application with publication number CN114910136A discloses a push-pull fiber Bragg grating seawater tide sensor. The currently disclosed patents and literature guides mainly design and study how to solidify the dual interference channel on the push-pull structure, and do not involve the signal processing method of the dual channel. Compared with the push-pull structure of the fiber interferometer containing two fiber arms, this push-pull structure contains two independent fiber interferometers, which is called a dual interference channel push-pull structure. In a dual-interference channel push-pull structure, the effect of doubling the sensitivity will not be directly reflected in the output of any interferometer, and the two interference channels need to be synthesized. In particular, since the dual interferometers independently but synchronously sense the push-pull signal, due to factors such as process errors, the responses of the two interference channels will be unbalanced, which further increases the difficulty of signal synthesis. Summary of the invention

[0005] In view of the sensor signal synthesis problem of the dual interference channel push-pull structure in the prior art, the present invention provides a signal scaling synthesis method for the dual interference channel push-pull structure, aiming to overcome the imbalance problem of "push" and "pull" in the sensitivity of the dual interference channels, effectively increase the response sensitivity after synthesis, minimize the lifting effect of the dual channel signal synthesis on the background noise, improve the sensing dynamic range, and eliminate the influence of common-mode interference signals.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] In one aspect, the present invention provides a signal scaling synthesis method for a dual interference channel push-pull structure, comprising the following steps:

[0008] S1. applying a single-frequency cosine signal within the sensing operating frequency band to a dual interference channel push-pull structure, wherein dual interference channels are provided on both sides of the dual interference channel push-pull structure;

[0009] S2. collecting interference signals of the dual interference channels, and independently demodulating the interference signals of the dual interference channels to obtain corresponding time domain response signals;

[0010] S3. Determine the scaling factor based on the amplitude value of the time domain response signal corresponding to the dual interference channel;

[0011] S4. Change the frequency of the single-frequency cosine signal applied to the dual interference channel push-pull structure and return to S1 until the result is n Scaling factor for different single-frequency cosine signal frequencies, , and judge n whether the fluctuation values ​​of the scaling coefficients under the different single-frequency cosine signal frequencies meet the preset scaling coefficient fluctuation requirements, if so, go to S5, if not, it means that the push-pull structure of the dual interference channel needs to be improved;

[0012] S5. According to the currently determined scaling factor, signal scaling synthesis is performed on the time domain response signal corresponding to the currently obtained dual interference channels.

[0013] Preferably, in S2, the interference signals of the dual interference channels are demodulated independently by a phase generated carrier method, a heterodyne method or a 3×3 method.

[0014] The present invention utilizes the signal phase reversal characteristic of the dual interference channel. Specifically, it is determined that when the initial phase of the time domain response signal corresponding to the dual interference channel is always reversed, the amplitude value of the time domain response signal corresponding to the dual interference channel in S3 is recorded as and ,like , then the scaling factor ;on the contrary .

[0015] Preferably, in S4, the preset scaling factor fluctuation requirement is: n The fluctuation of the scaling factors at different single-frequency cosine signal frequencies is less than 0.1%.

[0016] Preferably, in S5, if , synthetic signal ;on the contrary, .

[0017] Preferably, the dual interference channels are formed by a FP interferometer or a fiber laser resonant cavity.

[0018] The beneficial technical effects that the present invention can produce are:

[0019] The present invention utilizes the opposite phase characteristics of the signals formed by the push-pull structure on the dual interference channels, and adopts a scaling and then subtraction synthesis method to overcome the imbalance problem of the "push" and "pull" responses of the dual interference channel sensitivity and improve the sensing sensitivity of the push-pull structure.

[0020] Furthermore, the present invention uses the difference between the non-correlation of noise and the correlation of signals in the dual interference channels through scaling subtraction to minimize the effect of dual interference channel signal synthesis on the background noise, obtain the best equivalent noise signal, and improve the dynamic range of system response.

[0021] The present invention utilizes the correlation characteristics of the common-mode interference signals in the dual interference channels and adopts a subtraction method to reduce the response amplitude of the common-mode interference signals, thereby improving the anti-interference capability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0023] Figure 1 It is a flow chart of a signal scaling synthesis method for a dual interference channel push-pull structure provided in one embodiment;

[0024] Figure 2 Schematic diagram of a dual interference channel push-pull structure applicable to an embodiment;

[0025] Figure 3 It is a schematic diagram of the structure of a FP fiber interferometer applicable to an embodiment;

[0026] Figure 4 A schematic diagram of a dual interference channel modulation and demodulation structure applicable to an embodiment;

[0027] Numbers in the figure:

[0028] 101 is a push-pull structural component, 102 is a sensitivity enhancement component, 103 is a fiber interferometer, 104A is a first Bragg fiber grating, 104B is a second Bragg fiber grating, and 104C is a sensing fiber;

[0029] 201 is a light source optical modulation module, 202 is a photoelectric conversion and acquisition module, 203 is a fiber circulator, 204 is a transmission optical fiber, and 205 is a host computer.

[0030] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Reference Figure 1In one embodiment, a signal scaling synthesis method for a dual interference channel push-pull structure is provided, comprising the following steps:

[0033] S1. Apply a single-frequency cosine signal within the sensing operating frequency band to a dual interference channel push-pull structure, wherein dual interference channels are arranged on both sides of the dual interference channel push-pull structure. Without loss of generality, Figure 1 In the method, two sensing fiber interferometers are solidified on both sides of the push-pull structure to form a dual interference channel push-pull structure, and a single-frequency cosine signal within the push-pull structure response frequency band is applied to the push-pull structure.

[0034] S2. Collect the interference signals of the dual interference channels, denoted as and The interference signal of the dual interference channel and Demodulate them independently to obtain the corresponding time domain response signal, which is recorded as and , due to the reverse effect of the push-pull structure of the dual interference channels, and satisfy:

[0035] (Formula 1)

[0036] in, and is the response signal amplitude of the two interference channels; is the signal frequency of the applied single-frequency cosine signal; is the noise in the signal term; and are the background phase noise of the dual interference channels respectively.

[0037] S3. Determine the scaling factor based on the amplitude value of the time domain response signal corresponding to the dual interference channel;

[0038] Specifically, compared and The amplitude and initial phase of the signal. When the initial phases of the two independent demodulated signals are always in the opposite direction, the amplitude value of the time domain response signal corresponding to the dual interference channel is recorded as and ,like , then the scaling factor ;on the contrary .

[0039] S4. Change the frequency of the single-frequency cosine signal applied to the dual interference channel push-pull structure and return to S1 until the result is n Scaling factor for different single-frequency cosine signal frequencies, , and judge nWhether the fluctuation values ​​of the scaling coefficients under different single-frequency cosine signal frequencies meet the preset scaling coefficient fluctuation requirements, if so, go to S5, if not, it means that the push-pull structure of the dual interference channel needs to be improved, including further fixing the bonding method of the optical fiber.

[0040] S5. Perform signal scaling synthesis on the time domain response signal corresponding to the dual interference channels currently obtained according to the currently determined scaling factor. Specifically, if , synthetic signal ;on the contrary, .

[0041] The time domain response of the signal after signal scaling and synthesis is:

[0042] (Formula 2)

[0043] in

[0044] ;

[0045] (Formula 3)

[0046] In a preferred embodiment, in S2, the interference signals of the dual interference channels are demodulated independently by a phase generated carrier method, a heterodyne method or a 3×3 method.

[0047] In a preferred embodiment, the dual interference channels are composed of an FP interferometer or a fiber laser resonant cavity.

[0048] The present invention adopts a time domain signal scaling synthesis method, utilizes the signal inversion characteristics of the dual interference channel, and achieves signal response amplitude doubling by reasonably setting the scaling factor, while controlling the improvement level of the dual interference channel noise after mixing, and suppressing common mode noise. The scheme of the present invention can greatly improve the sensing sensitivity, dynamic range and anti-interference level of the dual interference channel push-pull structure.

[0049] In practical applications, the interference results of the dual interference channels are collected and demodulated independently. After the time domain response results of the signals are obtained, the signals are scaled and synthesized according to the method and scaling coefficient determined in S5, and then further Fourier transformed to obtain the frequency domain response results of the dual interference channel push-pull structure.

[0050] Comparing Formula 1 and Formula 2, it can be seen that the amplitude value of the signal response becomes ,because yes , The smaller value, the signal response amplitude obtained according to formula 2 at this time is 6dB higher than the interference channel with the smaller response. Since the channel background noise of the two independent fiber interferometers is not correlated, the noise calculation result obtained by formula 3 will not be directly reduced to zero, but the intensity is directly added, which can be increased to the original 3dB at most. However, since the increase in sensitivity is greater than the increase in background noise, the minimum measurable signal of the system can still be reduced by the scaling synthesis method to improve the dynamic range.

[0051] In special cases, if the two interference channels contain common-mode noise, that is, the noise contains a correlated part, as shown in the following formula 4:

[0052] (Formula 4)

[0053] in is the Fourier series expansion term of common mode noise, and The response coefficients of the two interference channels are the corresponding order terms. Keeping it consistent under all frequency signals, theoretically this part of noise can be completely eliminated by subtracting it according to formula 4.

[0054] It is not difficult to see that by adopting the scheme of the present invention, the problem of "push" and "pull" imbalance in the sensitivity of the dual interference channels can be overcome, the equivalent sensitivity after synthesis can be increased, the lifting effect of the dual-channel signal synthesis on the background noise can be minimized, the best equivalent noise signal can be obtained, and the influence of common-mode interference signals can be eliminated.

[0055] Reference Figure 2 , is a schematic diagram of a dual interference channel push-pull structure applicable to an embodiment, including two push-pull structural components 101 respectively wound with dual interferometers, a common sensitivity enhancement component 102 arranged between the two push-pull structural components 101, and two optical fiber interferometers 103 respectively solidified on the two push-pull structural components. The two push-pull structural components 101 are hard-connected to both sides of the sensitivity enhancement component 102 using metal or special glue. The two optical fiber interferometers 103 are completely identical in structure and are connected by optical fiber.

[0056] The dual interference channel push-pull structure itself is a receiving design for sensing. The signal can be applied to the fiber interferometers on both sides at the same time through the middle sensitivity enhancement component 102. For example, if the dual interference channel push-pull structure is placed on a vibration table, the acceleration of the vibration signal generated by the vibration table will cause the sensitivity enhancement component 102 (usually a metal mass block) shared between the two push-pull structure components to act on the fiber interferometers on both sides at the same time, and when one side stretches, the other side must contract, so the signal is reversed. This is the basic mechanism of the dual interference channel push-pull structure.

[0057] A single-frequency cosine signal within the sensing working frequency band is applied to the dual-interference channel push-pull structure, and the applied single-frequency cosine signal is simultaneously transmitted to the push-pull structural components on both sides of the sensitivity enhancement component 102 through the sensitivity enhancement component 102 shared between the two push-pull structural components 101, further causing the optical fiber interferometer 103 fixed on the two push-pull structural components 101 to generate a signal. Since the force exerted by the sensitivity enhancement component 102 on the push-pull structural components 101 and the optical fiber interferometer 103 on both sides is opposite, the phase of the signal generated by the optical fiber interferometer on both sides is also opposite.

[0058] Figure 3 It is a schematic diagram of a fiber interferometer applicable to an embodiment, including a first fiber Bragg grating 104A, a second fiber Bragg grating 104B, and a sensing fiber 104C. The first fiber Bragg grating 104A, the second fiber Bragg grating 104B, and the sensing fiber 104C are connected in sequence.

[0059] Figure 4 The schematic diagram of the dual interference channel modulation and demodulation structure applicable to an embodiment includes a light source light modulation module 201, a photoelectric conversion and acquisition module 202, a fiber circulator 203, a transmission optical fiber 204, and a host computer 205. The light source light modulation module 201 is connected to the fiber circulator 203 through an optical fiber. The fiber circulator 203 is connected to two fiber interferometers fixed on the dual interference channel push-pull structure through the transmission optical fiber 204. The fiber circulator 203 is connected to the photoelectric conversion and acquisition module 202 through an optical fiber. The photoelectric conversion and acquisition module 202 is connected to the host computer 205 through Ethernet.

[0060] Matters not covered by the present invention are known technologies.

[0061] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A signal scaling synthesis method for a dual interference channel push-pull structure, characterized in that: include: S1. applying a single-frequency cosine signal within the sensing operating frequency band to a dual interference channel push-pull structure, wherein dual interference channels are provided on both sides of the dual interference channel push-pull structure; S2. collecting interference signals of the dual interference channels, and independently demodulating the interference signals of the dual interference channels to obtain corresponding time domain response signals; S3. Determine the scaling factor based on the amplitude value of the time domain response signal corresponding to the dual interference channel; S4. Change the frequency of the single-frequency cosine signal applied to the dual interference channel push-pull structure and return to S1 until the result is n Scaling factor for different single-frequency cosine signal frequencies, , and judge n whether the fluctuation values ​​of the scaling coefficients under the different single-frequency cosine signal frequencies meet the preset scaling coefficient fluctuation requirements, if so, go to S5, if not, it means that the push-pull structure of the dual interference channel needs to be improved; S5. According to the currently determined scaling factor, signal scaling synthesis is performed on the time domain response signal corresponding to the currently obtained dual interference channels.

2. The signal scaling synthesis method for a dual interference channel push-pull structure according to claim 1, characterized in that: The initial phases of the time domain response signals corresponding to the dual interference channels are always opposite.

3. The signal scaling synthesis method for a dual interference channel push-pull structure according to claim 2, characterized in that: In S3, the amplitude value of the time domain response signal corresponding to the dual interference channel is recorded as and ,like , then the scaling factor ;on the contrary .

4. The signal scaling synthesis method for a dual interference channel push-pull structure according to claim 3, characterized in that: In S4, the preset scaling factor fluctuation requirement is: n The fluctuation of the scaling factors at different single-frequency cosine signal frequencies is less than 0.1%.

5. The signal scaling synthesis method for a dual interference channel push-pull structure according to claim 3, characterized in that: In S5, if , synthetic signal ;on the contrary, .

6. The signal scaling synthesis method for a dual interference channel push-pull structure according to any one of claims 1 to 5, characterized in that: The dual interference channels are composed of an FP interferometer or a fiber laser resonant cavity.

7. The signal scaling synthesis method for a dual interference channel push-pull structure according to claim 6, characterized in that: In S2, the interference signals of the dual interference channels are demodulated independently by a phase generation carrier method or a heterodyne method.

8. The signal scaling synthesis method for a dual interference channel push-pull structure according to any one of claims 1 to 5, characterized in that: The dual interference channel push-pull structure comprises two push-pull structural components respectively wrapped with dual interferometers, a common sensitivity enhancement component arranged between the two push-pull structural components, and two optical fiber interferometers respectively solidified on the two push-pull structural components.

9. The signal scaling synthesis method for a dual interference channel push-pull structure according to claim 8, characterized in that: The two push-pull structural components are rigidly connected to the two sides of the sensitizing component by using metal or special adhesive.

10. The signal scaling synthesis method for a dual interference channel push-pull structure according to claim 8, characterized in that: The two fiber optic interferometers are completely identical in structure and are connected via optical fiber.

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