A multi-parameter respiratory sensing monitoring system based on surface functionalized optical fiber

Abstract

The present invention discloses a multi-parameter respiratory sensing monitoring system based on surface functionalized optical fiber. The system has stable output, high sensitivity, short response time of the sensing unit, low price and easy manufacture. The technical scheme adopted by the present invention is that the system mainly includes a respiratory nasal mask sensing device and an optical fiber laser system. The sensing device has a simple structure. The sensing unit is formed by welding a section of pure quartz optical fiber between two sections of single-mode optical fiber, and a water vapor sensitive material is coated on the surface of the pure quartz optical fiber. The inner cavity structure of the optical fiber laser is pumped by a semiconductor laser with a central wavelength of 976nm, amplified by a 3m long erbium-doped optical fiber after a 980 / 1550nm wavelength division multiplexer, and then successively passes through an optical isolator, an adjustable attenuator and a sensing device, and outputs to a photoelectric detector through a 10:90 coupler. The present invention is mainly used in the field of biomedicine.

Description

Technical Field

[0001] The present invention uses a multi-parameter respiratory sensing monitoring device based on surface functionalized optical fiber to realize multi-parameter sensing monitoring of respiratory frequency, humidity and intensity, and belongs to an application of optical fiber sensing in the biomedical field. Technical Background

[0002] In modern society, people are increasingly aware of the importance of health, and respiratory monitoring is one of the main means of reflecting physical health, so respiratory sensors have received more and more attention. Respiratory sensors can be used to monitor the blood oxygen content of athletes, to monitor the basic physiological state of postoperative patients, and to monitor the quality of sleep at night at home. Good respiratory monitoring can also help with the timely diagnosis and treatment of some diseases.

[0003] The current mainstream respiratory monitoring system mainly focuses on single parameter sensing of respiratory frequency. The implementation form is to tie an elastic abdominal belt to the chest or abdomen, embed a pressure sensor in the abdominal belt, and measure the pressure of the chest or abdomen on the sensor during breathing to monitor the respiratory frequency. Due to the pressure of the binding, the sensor may make people feel that their breathing is blocked and cause discomfort. There are also literature reports that a more sensitive grating displacement sensor is used instead of a pressure sensor to be placed in the abdominal belt. When the grating bars on the abdominal belt are displaced with the scale grating as the abdomen rises and falls during human breathing, the grating photoelectric sensor will output two digital pulse signals A and B with a phase difference of 90 degrees respectively. When the grating bars move forward, phase A leads phase B by 90 degrees. At the falling edge of the phase A pulse, phase B is at a high level; when the grating bars move in the reverse direction, phase A lags phase B by 90 degrees. At the falling edge of the phase A pulse, phase B outputs a low level. Therefore, when the grating bar moves, its direction of movement can be determined by judging the level of the B phase (that is, the direction of movement of the grating bar can be determined by using this phase-frequency feature), so as to accurately determine the user's exhalation and inhalation process. The number of pulses output is proportional to the displacement of the grating bar. Therefore, by counting the output pulses, the displacement of the corresponding grating bar can be calculated, thereby obtaining the change in the abdomen when the human body breathes. This method requires that the parameters of the grating bars on the belly belt are completely consistent with those of the grating scale, and a circuit with a photoresistor is required to realize photoelectric conversion, which increases the complexity and production cost of the sensor. Since the grating displacement sensor senses the change in the circumference of the belly belt, actions such as turning over during measurement will also affect the measurement. In addition, some patients in the postoperative recovery period cannot use belly belts, which limits the use of the above sensors.

[0004] In the present invention, optical fiber is used to directly sense nasal airflow to monitor breathing, avoiding the above disadvantages. In addition, the sensing unit uses a special SNCS structure optical fiber, and a water vapor sensitive material is coated on the surface of the pure quartz optical fiber to form multi-mode interference in the optical fiber. Through the drift and intensity change of its transmission spectrum during breathing, multi-parameter monitoring of breathing frequency, humidity and intensity is achieved. Summary of the invention

[0005] The purpose of the present invention is to propose for the first time a multi-parameter respiratory sensing monitoring system based on surface functionalized optical fiber. A special optical fiber SNCS structure is used to form multi-mode interference inside the optical fiber. A water vapor sensitive material is coated on the surface of the pure quartz optical fiber, and the drift of its transmission spectrum and the change of intensity during breathing are used to monitor the respiratory frequency, humidity and intensity. The present invention is completely based on another idea, avoiding the pressure on breathing caused by the use of a belly belt-type structure, and also effectively reducing the impact of actions such as turning over during sleep on monitoring. Moreover, some patients in the postoperative recovery period cannot use a belly belt due to surgical wounds. The nasal mask type optical fiber respiratory sensor avoids the problem of limitations in the use of belly belts. The system adopts a fiber laser cavity structure, which reduces the signal pulse width, increases the peak intensity, and enhances the signal-to-noise ratio, so that the system does not require complex equipment such as signal amplification and noise reduction to achieve high resolution, reducing the complexity of the system.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The system mainly includes a respiratory nasal mask sensor device and a fiber laser system.

[0008] The sensing device has a simple structure. The sensing unit is mainly a SNCS (single-mode-no-core-single-mode) optical fiber. This part is composed of a section of pure quartz optical fiber welded between two sections of single-mode optical fiber. We pass this sensing unit horizontally through the nasal mask tube and as close to the nose as possible. The nasal airflow can cause the pure quartz optical fiber to bend and deform. After the light is transmitted through the single-mode optical fiber, it is coupled into the pure quartz optical fiber, and the high-order mode is excited. Multiple modes are transmitted in the pure quartz optical fiber at the same time, and are coupled at the other end of the pure quartz optical fiber to enter the single-mode optical fiber again. Multi-mode interference occurs inside the optical fiber to form a specific transmission spectrum. When the pure quartz optical fiber is bent horizontally, its refractive index distribution will change, resulting in the drift of the transmission spectrum of the pure quartz optical fiber. Water vapor sensitive material is coated on the surface of the pure quartz optical fiber. When the pure quartz optical fiber is bent, the high-order mode is absorbed by the material in the evanescent zone, resulting in a change in the intensity of the transmission spectrum. By monitoring the drift and intensity change of the transmission spectrum, we can achieve multi-parameter sensing of the humidity, intensity and frequency of breathing.

[0009] The fiber laser cavity structure is pumped by a semiconductor laser with a central wavelength of 976nm, amplified by a 3m long erbium-doped fiber after passing through a 980 / 1550nm wavelength division multiplexer, and then successively passes through an optical isolator, an adjustable attenuator and a sensor device, and outputs to a photodetector through a 10:90 coupler. The fiber laser cavity structure compresses the pulse width of the output signal, and the 3-dB bandwidth is about 0.08nm, which increases the peak intensity and enhances the signal-to-noise ratio to about 60dB, which improves the resolution of the system and greatly improves the sensitivity of the entire system.

[0010] The main feature of the fiber laser cavity system structure in the present invention is that an adjustable attenuator is added to the traditional structure to adjust the threshold of the entire cavity, so as to achieve the effect of laser output when the patient exhales and no laser output when the patient inhales. This design is to achieve the same effect for the visual condition of the breathing sensor for patients with different breath strengths.

[0011] The sensing unit uses pure quartz optical fiber with a length of 125 mm, so that the peak of the transmission spectrum of the SNCS optical fiber overlaps with the peak of the gain spectrum of the optical fiber laser, while also suppressing mode competition, so that the output of the sensor is more stable.

[0012] Compared with the prior art, the technical features and effects of the present invention are as follows:

[0013] The advantage of the patent of the present invention is that it uses the fiber laser cavity structure, reduces the pulse width of the output signal, increases the peak intensity of the signal, and improves the signal-to-noise ratio, making the signal easier to identify, and the system does not require signal amplification and noise reduction equipment, as well as a spectrometer, saving costs. The addition of an adjustable attenuator allows patients with different breath strengths to achieve the same visual effect. The sensor probe is placed directly near the nose to sense the nasal airflow. Compared with the previously reported abdominal belt-type structure, there are fewer influencing factors, fewer uncontrollable factors during monitoring, and it is easier to obtain real results. The SNCS fiber optic sensing unit is very sensitive to strain, the sensor has a short response time, and the sensing unit is inexpensive and easy to make. During clinical use, it can be directly connected to the fiber laser cavity system through an optical circulator, which can be used once, which is beneficial to the hygiene of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the fiber laser system used in the present invention.

[0015] Figure 2 Schematic diagram of the adjustable attenuator in the system of the present invention.

[0016] Figure 3 Schematic diagram of the sensor nose mask device in the system of the present invention.

[0017] The components represented by the reference numerals in the accompanying drawings are as follows:

[0018] 1-Laser pump source (semiconductor laser with pigtail output, fixed output wavelength of 978nm, current-controlled output power, maximum output power of 100W); 2-980 / 1550nm wavelength division multiplexer; 3-3m erbium-doped optical fiber; 4-optical isolator; 5-1*2 coupler (the power ratio between the input photodetector and the loop is 10:90); 6-TEC (semiconductor refrigeration chip); 7-PMF (polarization-maintaining fiber); 8-3-dB coupler; 9-universal nose mask; 10-shock-absorbing ring; 111-shock-absorbing gasket 1; 112-shock-absorbing gasket 2; 113-shock-absorbing gasket 3; 12-elastic film material; 131-ultraviolet glue 1; 132-ultraviolet glue 2; 14-sensing optical fiber (SNCS structure, composed of single-mode optical fibers welded at both ends of pure quartz optical fiber, the pure quartz optical fiber has a usable length of 125mm, and the surface is coated with water vapor sensitive material). DETAILED DESCRIPTION

[0019] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0020] Figure 1 The figure shows a schematic diagram of the fiber laser system used in the respiratory sensor. Compared with the existing fiber laser system cavity structure, the present invention adds an adjustable attenuator to adjust the threshold of the entire fiber laser system, so that when the exhaled gas and the fiber bends outward, the gain of the laser system is greater than the loss, and there is laser output. When the fiber is not bent or the inhaled gas and the fiber bends inward, the loss of the laser system is greater than the gain, and there is no laser output. This design is to achieve the same effect for the visual conditions of the respiratory sensor for patients with different breath strengths.

[0021] Figure 2 The diagram is a schematic diagram of the adjustable attenuator structure. The Sagnac loop is composed of a 3-dB coupler 8 and a polarization-maintaining fiber 7, and the polarization-maintaining fiber 7 is placed on a semiconductor refrigerator 6. The temperature of the polarization-maintaining fiber is regulated and controlled by the semiconductor refrigerator, thereby achieving adjustable insertion loss of the Sagnac loop.

[0022] Figure 3The figure is a schematic diagram of a breathing sensor device. The shock-absorbing ring 10 is fixed in the universal nose mask 9 with three shock-absorbing gaskets (respectively 111, 112 and 113) to prevent the friction vibration between the ring and the nose mask from affecting the measurement. A layer of elastic film material is laid inside the ring, and the SNCS optical fiber is fixed on the elastic film with ultraviolet glue (131 and 132 in the figure), and the pure quartz optical fiber is in the center of the film. The shock-absorbing ring and the film support and protect the sensing optical fiber, while increasing the contact area between the sensor element and the nasal airflow, thereby improving the sensitivity of the sensing optical fiber to the airflow. The water vapor sensitive material is coated on the surface of the pure quartz optical fiber, which makes the sensing optical fiber sensitive to the airflow and enhances its sensitivity to water vapor, thereby realizing the multi-parameter sensing of the sensor element to the humidity, intensity and frequency of the breath.

Claims

1. A multi-parameter respiratory sensing monitoring system based on surface functionalized optical fiber, characterized in that: The system mainly includes a respiratory mask sensor device and a fiber laser system. The respiratory mask sensor device includes a sensor unit. The sensor unit is mainly a SNCS optical fiber. The optical fiber is formed by welding a section of pure quartz optical fiber between two sections of single-mode optical fiber, and a water vapor sensitive material is coated on the surface of the pure quartz optical fiber. The length of the pure quartz optical fiber is 125 mm. The fiber laser cavity structure is pumped by a semiconductor laser with a central wavelength of 976 nm, amplified by a 3-m long erbium-doped optical fiber after a 980 / 1550 nm wavelength division multiplexer, and then successively passes through an optical isolator, an adjustable attenuator and a respiratory mask sensor device, and is output to a photodetector through a 10:90 coupler. An adjustable attenuation structure is added to the fiber laser system, and a 3-dB coupler and a polarization-maintaining optical fiber are connected to form a Sagnac ring, and the polarization-maintaining optical fiber is placed on a semiconductor refrigeration chip. The semiconductor refrigeration chip adjusts and controls the temperature of the polarization-maintaining optical fiber, thereby realizing the threshold adjustment of the entire inner cavity, so as to achieve the effect of laser output when the patient exhales and no laser output when the patient inhales.

2. The multi-parameter respiratory sensing monitoring system based on surface functionalized optical fiber as claimed in claim 1, characterized in that In the respiratory nasal mask sensor device, a section of pure quartz optical fiber is welded between two sections of single-mode optical fiber to form a sensing unit. The nasal airflow can cause the pure quartz optical fiber to bend and deform.

3. The multi-parameter respiratory sensing monitoring system based on surface functionalized optical fiber as claimed in claim 1, characterized in that In the respiratory nasal mask sensor device, a shock-absorbing ring is fixed in a universal nasal mask with three shock-absorbing gaskets, a layer of elastic film material is laid in the ring, and the SNCS optical fiber is fixed on the elastic film with ultraviolet glue, and the pure quartz optical fiber is located in the center of the film.

4. The multi-parameter respiratory sensing monitoring system based on surface functionalized optical fiber as claimed in claim 1, characterized in that: The surface of the pure quartz optical fiber in the SNCS structure is coated with water vapor sensitive material to form multi-mode interference in the optical fiber, thus realizing multi-parameter sensing of respiratory humidity, intensity and frequency by the respiratory nasal mask sensor device.

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