A wavelength division multiplexing fiber optic ballistocardiogram sensor and its anti-interference method

Abstract

The present invention provides a wavelength division multiplexing fiber optic ballistocardiogram sensor and its anti-interference method, including an MCU microprocessor circuit, a first light source generator, a second light source generator, a first photodetector, a second photodetector, a first wavelength division multiplexer, a second wavelength division multiplexer, a dual-port mode interference fiber optic component and a terminal; the dual-port mode interference fiber optic component includes a first port and a second port; the MCU microprocessor circuit is connected to the terminal. Applying this technical solution can effectively reduce the interference and false alarms caused by various noises during the measurement process.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber optic sensing, in particular to a wavelength division multiplexing fiber optic ballistocardiogram sensor and an anti-interference method thereof. Background Art

[0002] Fiber optic ballistocardiogram sensors can non-invasively monitor the vital sign parameters of humans or animals (such as respiratory rate, heart rate, and body movement, etc.), and can be measured without direct contact with the body skin. The fiber optic ballistocardiogram sensors mainly include micro-bent fiber optic ballistocardiogram sensors, fiber Bragg grating ballistocardiogram sensors, traditional fiber optic interferometer ballistocardiogram sensors, fiber optic mode interference ballistocardiogram sensors, etc. The main problems faced by these sensors currently are the problems of ballistocardiogram signal disappearance and external interference. Recently published papers (Noninvasive Measurement of Heart Rate and Respiratory Rate for Perioperative Infants, J. Lightwave Technol. 37, 2807-2814, 2019; Assessment of Heart Rate and Respiratory Rate for Perioperative Infants Based on ELC Model, IEEE Sensors Journal, vol. 21, no. 12, pp. 13685-13694, June 15, 2021; Deeplearning-based ballistocardiography

[0003] reconstruction algorithm on the optical fiber sensor, Optics Express Vol. 30, No. 8, pp13121, 11 Apr 2022.) use deep learning models to solve the problems of ballistocardiogram signal disappearance and external interference. Although the deep learning method is good, the established model requires a large amount of data training. For different populations and different applications, the model needs to be retrained with data from different populations or applications. Chinese Patent Application 202010741628.2 uses a fiber optic ballistocardiogram sensor with a concave-convex noise reduction component and attempts to use a dual-channel hardware method to solve the problems of ballistocardiogram signal disappearance and external interference. This invention requires a dual-fiber loop.

[0004] U.S. Patent US 6,498,652 B1 proposes to monitor the human respiratory rate and heart rate using a fiber optic interferometer. The disadvantage is that the proposed fiber optic interferometer system is not compact enough, and the reference arm and the sensing arm need to be separated and isolated. The ballistocardiogram sensor based on fiber optic mode interference (CN210144637U, CN107854119A, "Xu W, et al., Long modal interference in multimode fiber and its application in vital signs monitoring, Optics Communications, 2020, 474: 126100") has a simple structure, and the reference arm and the sensing arm do not need to be separated and isolated. However, from the perspective of the hardware principle, these patents and methods cannot solve the problem of the disappearance of the ballistocardiogram signal without using complex hardware phase compensation methods and the like. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a wavelength division multiplexing fiber optic ballistocardiogram sensor and its anti-interference method to effectively reduce the interference and false alarms caused by various noises during the measurement process.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A wavelength division multiplexing fiber optic ballistocardiogram sensor includes an MCU microprocessor circuit, a first light source generator, a second light source generator, a first photodetector, a second photodetector, a first wavelength division multiplexer, a second wavelength division multiplexer, a dual-port mode interference fiber optic component, and a terminal; the dual-port mode interference fiber optic component includes a first port and a second port; the MCU microprocessor is connected to the terminal.

[0007] One end of the first light source generator is respectively connected to the MCU microprocessor and the first wavelength division multiplexer, and both ends of the first photodetector are respectively connected to the MCU microprocessor circuit and the first wavelength division multiplexer; one end of the second light source generator is respectively connected to the MCU microprocessor circuit and the second wavelength division multiplexer, and both ends of the second photodetector are respectively connected to the MCU microprocessor and the second wavelength division multiplexer; the other end of the first wavelength division multiplexer is connected to the first port through a first fiber optic connector, and the other end of the second wavelength division multiplexer is connected to the second port through a second fiber optic connector.

[0008] In a preferred embodiment, the dual-port mode interference fiber optic component includes a first sensing loop, a second sensing loop, and a third sensing loop.

[0009] In a preferred embodiment, the first light source is emitted from the first light source generator, passes through the first wavelength division multiplexer and the first fiber optic connector, and is incident on the first port of the dual-port mode interference fiber optic component. The first light source passes through the first sensing loop, the second sensing loop, and the third sensing loop, and then is output through the second port to the second fiber optic connector and the second wavelength division multiplexer to reach the second photodetector.

[0010] In a preferred embodiment, the second light source is emitted from the second light source generator, passes through the second wavelength division multiplexer and the second fiber optic connector, and is incident on the second port of the dual-port mode interference fiber optic component. The second light source passes through the third sensing loop, the second sensing loop, and the first sensing loop, and then is output through the first port to the first fiber optic connector and the first wavelength division multiplexer to reach the first photodetector.

[0011] In a preferred embodiment, the wavelength of the first light source is λ1, and the first light source is located in the linear working region; the wavelength of the second light source is λ2, and the second light source is located in the non-linear working region.

[0012] In a preferred embodiment, after the first light source reaches the second photodetector and the second light source reaches the first photodetector, a photocurrent is formed and output to the MCU microprocessor circuit, and the MCU microprocessor circuit processes the received photocurrent signal and then outputs it to the terminal.

[0013] In a preferred embodiment, the first light source generator and the second light source generator are specifically laser light sources or light emitting diodes.

[0014] In a preferred embodiment, the second sensing loop is specifically a sensitive unit.

[0015] In a preferred embodiment, at one working point, the first light source operates in the linear working region, and at the other working point, the second light source operates in the non-linear working region. When the vital sign vibration signal acts on the sensitive unit, the working characteristic curve of the sensor changes with the vibration of the vital sign signal; the light emitted from the first light source generator is detected by the second photodetector, and the ballistocardiogram signal is correctly demodulated; while the light emitted from the second light source generator is detected by the first photodetector, the ballistocardiogram signal disappears; if the working characteristic curve of the sensor drifts and changes due to the non-vital sign vibration interference signal, the working point drifts from the linear working region to the non-linear working region, and the other working point drifts from the original non-linear working region to the linear working region.

[0016] The present invention also provides an anti-interference method for a wavelength division multiplexing fiber cardiogram sensor, which adopts the above-mentioned wavelength division multiplexing fiber cardiogram sensor; it includes a first light source sensing loop formed by a first light source generator, a first photodetector, a first wavelength division multiplexer and a dual-port mode interference fiber component, and a second light source sensing loop formed by a second light source generator, a second photodetector, a second wavelength division multiplexer and a dual-port mode interference fiber component;

[0017] One channel operates in the linear working region, while the other channel operates in the non-linear working region; in terms of the output signal amplitude, for the first light source sensing loop, the average amplitude without interference is F1; for the second light source sensing loop, the average amplitude without interference is F2; after the sensing loop is interfered, if the average amplitude F1 of the first light source sensing loop exceeds a certain value range compared with the original, such as + / - 15%, or the average amplitude F2 of the second light source sensing loop exceeds a certain value range compared with the original, such as + / - 15%, then the data quality in this period is not good and cannot be used to construct the cardiogram signal; in terms of the output signal spectrum, for the first light source sensing loop, the average amplitude of the main peak spectrum before interference is FP1, and for the second light source sensing loop, the average amplitude of the main peak spectrum before interference is FP2; after the sensing loop is interfered, if the change in the average amplitude FP1 of the main peak spectrum of the first light source sensing loop exceeds a certain value range, such as + / - 30%, or the change in the average amplitude FP2 of the main peak spectrum of the second light source sensing loop exceeds + / - 30%, then the data quality in this period is not good and cannot be used to construct the cardiogram signal.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The hardware device structure has a simple single-fiber two-channel structure, which is simple and easy to assemble, and has a low cost.

[0020] 2. The dual working point scheme can effectively reduce the interference and false alarms caused by various noises during the measurement process.

[0021] 3. The optical communication components used have low costs and are easy to manufacture, apply and promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the working point of the sensor working characteristic curve;

[0023] Figure 2 It is a schematic diagram of the right drift of the working point of the sensor working characteristic curve;

[0024] Figure 3 It is a schematic diagram of the left drift of the working point of the sensor working characteristic curve;

[0025] Figure 4Schematic diagram of the double working points of the sensor working characteristic curve in the device embodiment of the present invention;

[0026] Figure 5 Schematic diagram of the right drift of the double working points of the sensor working characteristic curve in the device embodiment of the present invention;

[0027] Figure 6 Schematic diagram of the left drift of the double working points of the sensor working characteristic curve in the device embodiment of the present invention;

[0028] Figure 7 Schematic diagram of the structure of the sensor device in the device embodiment of the present invention;

[0029] Figure 8 Schematic diagram of the sensor working characteristic curve in the device embodiment of the present invention;

[0030] Figure 9 Schematic diagram of the heart impact diagram demodulated in the linear working area in the device embodiment of the present invention;

[0031] Figure 10 Schematic diagram of the heart impact diagram demodulated in the non - linear working area in the device embodiment of the present invention;

[0032] Figure 11 Schematic diagram of the 6 - second heart impact diagram demodulated in the linear working area in the device embodiment of the present invention;

[0033] Figure 12 Schematic diagram of the 6 - second heart impact diagram demodulated in the non - linear working area in the device embodiment of the present invention. Detailed implementation manners

[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0035] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0036] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] A wavelength - division multiplexing fiber optic heart impact diagram sensor and its anti - interference method, refer to Figures 1 to 12, including an MCU microprocessor, a first light source generator LD1, a second light source generator LD2, a first photodetector PD1, a second photodetector PD2, a first wavelength division multiplexer WDM1, a second wavelength division multiplexer WDM2, a dual-port mode interference fiber optic component 5, and a terminal; the dual-port mode interference fiber optic component includes a first port 1 and a second port 2; the MCU microprocessor circuit is wirelessly connected to the terminal via wifi or Bluetooth; the first light source generator LD1, the second light source generator LD2, the first photodetector PD1, the second photodetector PD2, the first wavelength division multiplexer WDM1, the second wavelength division multiplexer WDM2, and the dual-port mode interference fiber optic component 5 form an optical transceiver module 6.

[0038] Both ends of the first light source generator LD1 are respectively connected to the MCU microprocessor circuit and the first wavelength division multiplexer WDM1, and both ends of the first photodetector PD1 are respectively connected to the MCU microprocessor circuit and the first wavelength division multiplexer WDM1; both ends of the second light source generator LD2 are respectively connected to the MCU microprocessor circuit and the second wavelength division multiplexer WDM2, and both ends of the second photodetector PD2 are respectively connected to the MCU microprocessor circuit and the second wavelength division multiplexer WDM2; the other end of the first wavelength division multiplexer WDM1 is connected to the first port 1 through a first fiber optic connector 11, and the other end of the second wavelength division multiplexer WDM2 is connected to the second port 2 through a second fiber optic connector 22.

[0039] The dual-port mode interference fiber optic component 5 includes a first sensing loop 13, a second sensing loop 34, and a third sensing loop 24.

[0040] The first light source is emitted from the first light source generator LD1, passes through the first wavelength division multiplexer WDM1 and the first fiber optic connector 11, and is incident on the first port 1 of the dual-port mode interference fiber optic component 5. The first light source passes through the first sensing loop 13, the second sensing loop 34, and the third sensing loop 24, and then is output from the second port 2 to the second fiber optic connector 22 and the second wavelength division multiplexer WDM2 to reach the second photodetector PD2.

[0041] The second light source is emitted from the second light source generator LD2, passes through the second wavelength division multiplexer WDM2 and the second fiber optic connector 22, and is incident on the second port 2 of the dual-port mode interference fiber optic component 5. The second light source passes through the third sensing loop 13, the second sensing loop 34, and the first sensing loop 24, and then is output from the first port 1 to the first fiber optic connector 11 and the first wavelength division multiplexer WDM1 to reach the first photodetector PD1.

[0042] The wavelength of the first light source is λ1, and the first light source is located in the linear working region; the wavelength of the second light source is λ2, and the second light source is located in the nonlinear working region.

[0043] After the first light source reaches the second photodetector PD2 and the second light source reaches the first photodetector PD1, a photocurrent is formed and output to the MCU microprocessor circuit, and the MCU microprocessor receives the photocurrent signal and processes it and outputs it to the terminal. The first light source generator LD1 and the second light source generator LD2 are specifically laser light sources or light emitting diodes. The second sensing circuit 34 is specifically a sensitive unit.

[0044] Figure 1 This is a typical fiber optic mode interferometer ballistocardiogram sensor operating characteristic curve, where the operating point A is located in the linear operating area. In the linear operating area, the ballistocardiogram sensor ballistocardiogram signal does not have a signal fading problem. When interference signals such as non-vital sign vibrations cause slight changes in the structural parameters of the mode interferometer sensor, the sensor operating characteristic curve will drift, so that the original operating point A drifts from the linear operating area to the nonlinear operating area, such as Figures 2 - 3 As shown. When the sensor works in the nonlinear working area, the ballistocardiogram signal will be distorted and disappear. In order to solve the problem of ballistocardiogram signal disappearance of the fiber mode interferometer ballistocardiogram sensor, we propose a new sensor device and a method to resist the disappearance of the ballistocardiogram signal, namely the dual working point method, one working point works in the linear working area A, and the other working point works in the nonlinear working area B, ensuring that there is a working point working in the linear working area, such as Figure 4 If interference signals such as non-vital vibrations cause the sensor operating characteristic curve to drift, the position of the working point A drifts from the linear working area to the nonlinear working area, and the position of the other working point B drifts from the original nonlinear working area to the linear working area, as shown in Figure 1. Figure 5 (left drift), Figure 6 (right drift). In this way, even if the interference signal such as non-vital vibration causes the sensor working characteristic curve to drift, there is still a working point working in the linear working area. Therefore, the method and the device can solve the problem of the disappearance of the ballistocardiogram signal of the ballistocardiogram sensor. It should be noted that Figure 1 It is both a typical fiber mode interferometer ballistocardiogram sensor working characteristic curve and a typical bent fiber ballistocardiogram sensor working characteristic curve. Therefore, the above method is also applicable to other fiber ballistocardiogram sensors with similar working characteristic curves. In addition, the sensor of the present invention has a single-fiber dual-channel structure. By using sensor fusion technology, the sensor can also eliminate the interference of other external noises.

[0045] The principle of the fiber optic ballistocardiogram sensor of the present invention to fundamentally eliminate the disappearance of the ballistocardiogram signal is as follows.

[0046] We propose a new sensor device and a method for eliminating the ballistocardiogram signal, namely the dual operating point method. One operating point λ1 operates in the linear operating region A, and the other operating point λ2 operates in the non-linear operating region B, ensuring that one operating point operates in the linear operating region, as Figure 4 shown. When the vital sign vibration signal acts on the sensitive unit 34 in the dual-port mode interference optical fiber component 5, the sensor operating characteristic curve changes with the vibration of the vital sign signal. The light from the first light source sensing loop is detected by the second photodetector PD2, and the ballistocardiogram signal can be correctly demodulated, as Figure 9 shown. In Figure 9 , there are obvious IJK peaks in the ballistocardiogram. The light from the second light source sensing loop is detected by the photodetector PD1, and the ballistocardiogram signal disappears, without obvious IJK peaks, as Figure 10 shown. If the sensor operating characteristic curve drifts due to interference signals such as non-vital sign vibrations, the position A of the operating point drifts from the linear operating region to the non-linear operating region, and the position B of the other operating point drifts from the original non-linear operating region to the linear operating region, as Figure 5 (left drift), Figure 6 (right drift) shown. In this way, even if the sensor operating characteristic curve drifts, there is still one operating point operating in the linear operating region. In this way, we can ensure that one light source sensing loop can demodulate the ballistocardiogram signal. Therefore, this method and its device can solve the problem of the disappearance of the ballistocardiogram signal in the ballistocardiogram sensor.

[0047] In addition, the sensor has a dual-channel structure. By using sensor fusion technology, the sensor can also eliminate the interference of other external noises (not the interference at the working point). The noise interference comes from the system itself and external interference, including interference from non-respiratory and non-heartbeat vibrations, such as slight speech, slight movement of hands and feet, and muscle tremors. According to the characteristics of our single-fiber dual-channel sensor structure device, there are two channels in the same sensing loop, and the same noise source has the same interference on the two-channel sensing loops. However, the interference effects may be different. mainly because one channel works in the linear working region, while the other works in the non-linear working region. In terms of the output signal amplitude, for the λ1 light source sensing loop, the average amplitude without interference is F1; for the λ2 light source sensing loop, the average amplitude without interference is F2. After the sensing loop is interfered, if the average amplitude F1 of the λ1 light source sensing loop exceeds a certain value range compared with the original, such as + / - 15%, or the average amplitude F2 of the λ2 light source sensing loop exceeds a certain value range compared with the original, such as + / - 15%, then the data quality in this period is not good and cannot be used to construct the ballistocardiogram signal. In terms of the output signal spectrum, for the λ1 light source sensing loop, the average amplitude of the main peak spectrum before interference is FP1, and for the λ2 light source sensing loop, the average amplitude of the main peak spectrum before interference is FP2. After the sensing loop is interfered, if the change in the average amplitude FP1 of the main peak spectrum of the λ1 light source sensing loop exceeds a certain value range, such as + / - 30%, or the change in the average amplitude FP2 of the main peak spectrum of the λ2 light source sensing loop exceeds + / - 30%, then the data quality in this period is not good and cannot be used to construct the ballistocardiogram signal. Coupled with ensuring that one light source sensing loop works in the linear working area, this fundamentally eliminates the possible false alarms.

[0048] The above-mentioned MCU processor circuit is used to perform a series of processes such as amplification, filtering, analog-to-digital conversion, and calculation on the photodetectors PD1 and PD2, and wirelessly transmit them to the terminal.

[0049] The terminal reports the ballistocardiogram, heart rate, respiratory rate, sleep quality, and alarms, etc.

[0050] The working wavelength band of the photodetector matches that of the light source.

Claims

1. A wavelength division multiplexing fiber optic ballistocardiogram sensor, characterized in that, It includes an MCU microprocessor, a first light source generator, a second light source generator, a first photodetector, a second photodetector, a first wavelength division multiplexer, a second wavelength division multiplexer, a dual-port mode interference optical fiber component and a terminal; the dual-port mode interference optical fiber component includes a first port and a second port; the MCU microprocessor is connected to the terminal; Both ends of the first light source generator are respectively connected to the MCU microprocessor circuit and the first wavelength division multiplexer, and both ends of the first photodetector are respectively connected to the MCU microprocessor circuit and the first wavelength division multiplexer; both ends of the second light source generator are respectively connected to the MCU microprocessor circuit and the second wavelength division multiplexer, and both ends of the second photodetector are respectively connected to the MCU microprocessor circuit and the second wavelength division multiplexer; the other end of the first wavelength division multiplexer is connected to the first port through a first fiber optic connector, and the other end of the second wavelength division multiplexer is connected to the second port through a second fiber optic connector; One working point, the first light source works in the linear working region, and the other working point, the second light source works in the non-linear working region. When the vital sign vibration signal acts on the sensitive unit, the working characteristic curve of the sensor changes with the vibration of the vital sign signal; the second photodetector detects the light emitted from the first light source generator and correctly demodulates the ballistocardiogram signal; while the first photodetector detects the light emitted from the second light source generator and the ballistocardiogram signal disappears; if the working characteristic curve of the sensor drifts and changes due to the non-vital sign vibration interference signal, the working point drifts from the linear working region to the non-linear working region, and the other working point drifts from the original non-linear working region to the linear working region.

2. The wavelength division multiplexing fiber optic ballistocardiogram sensor according to claim 1, wherein The dual-port mode interference optical fiber component includes a first sensing loop, a second sensing loop and a third sensing loop.

3. The wavelength division multiplexing fiber optic ballistocardiogram sensor according to claim 2, wherein The first light source is emitted from the first light source generator, passes through the first wavelength division multiplexer and the first fiber optic connector, and is incident on the first port of the dual-port mode interference optical fiber component. The first light source passes through the first sensing loop, the second sensing loop and the third sensing loop, and then is output to the second fiber optic connector and the second wavelength division multiplexer through the second port and reaches the second photodetector.

4. The wavelength division multiplexing fiber optic ballistocardiogram sensor according to claim 3, wherein, The second light source is emitted from the second light source generator, passes through the second wavelength division multiplexer and the second fiber optic connector, and is incident on the second port of the dual-port mode interference optical fiber component. The second light source passes through the third sensing loop, the second sensing loop and the first sensing loop, and then is output to the first fiber optic connector and the first wavelength division multiplexer through the first port and reaches the first photodetector.

5. The wavelength division multiplexing fiber optic ballistocardiogram sensor according to claim 4, characterized in that, The wavelength of the first light source is λ1, and the first light source is located in the linear working region; the wavelength of the second light source is λ2, and the second light source is located in the non-linear working region.

6. The wavelength division multiplexing fiber optic ballistocardiogram sensor according to claim 5, wherein, After the first light source reaches the second photodetector and the second light source reaches the first photodetector, a photocurrent is formed and output to the MCU microprocessor circuit, and the MCU microprocessor circuit processes the received photocurrent signal and outputs it to the terminal.

7. The wavelength division multiplexing fiber optic ballistocardiogram sensor according to claim 6, characterized in that The first light source generator and the second light source generator are specifically a laser light source or a light emitting diode.

8. The wavelength division multiplexing fiber optic ballistocardiogram sensor according to claim 7, wherein The second sensing loop is specifically a sensitive unit.

9. An anti-interference method for a wavelength division multiplexing fiber cardiogram sensor, characterized in that A wavelength division multiplexing fiber cardiogram sensor according to any one of the above claims 1 to 8; comprising a first light source sensing loop formed by a first light source generator, a first photodetector, a first wavelength division multiplexer and a dual-port mode interference fiber component, and a second light source sensing loop formed by a second light source generator, a second photodetector, a second wavelength division multiplexer and a dual-port mode interference fiber component; One channel operates in the linear operating region, while the other channel operates in the non-linear operating region; in terms of the output signal amplitude, for the first light source sensing loop, the average amplitude without interference is F1; for the second light source sensing loop, the average amplitude without interference is F2; after the sensing loop is interfered, if the average amplitude F1 of the first light source sensing loop exceeds the range of ±15% compared with the original, or the average amplitude F2 of the second light source sensing loop exceeds the range of ±15% compared with the original, then the data quality in this period is not good and cannot be used to construct the cardiogram signal; in terms of the output signal spectrum, for the first light source sensing loop, the average amplitude of the main peak spectrum before interference is FP1, and for the second light source sensing loop, the average amplitude of the main peak spectrum before interference is FP2; after the sensing loop is interfered, if the change in the average amplitude FP1 of the main peak spectrum of the first light source sensing loop exceeds the range of ±30%, or the change in the average amplitude FP2 of the main peak spectrum of the second light source sensing loop exceeds ±30%, then the data quality in this period is not good and cannot be used to construct the cardiogram signal.

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