Single-Ended Single-Fiber Michelson Fiber Optic Interferometer-Based Vital Sign Device and Method

Abstract

The present invention relates to a vital sign device based on a single-ended single-fiber Michelson fiber interferometer, which includes a light source, a photodetector, an optical fiber coupler, a single-ended single-fiber Michelson fiber interferometer, a microcontroller unit (MCU) and a terminal; the optical fiber coupler is respectively connected to the light source, the photodetector and the single-ended single-fiber Michelson fiber interferometer; the photodetector is also connected to the terminal through the MCU. In the present invention, the reference arm and the interference arm are combined without being separately arranged, effectively avoiding the influence of the environment on the reference arm, and having a minimalist structure of single-ended single-fiber; not only coherent light sources can be used, but also incoherent light sources can be used.

Description

Technical Field

[0001] The present invention relates to the technical field of vital sign parameter monitoring, and particularly to a vital sign device and method based on a single-ended single-fiber Michelson fiber interferometer. Background Art

[0002] Vital signs, including heart rate, respiratory rate, etc., are important indicator parameters for maintaining normal body activities and are also important indicators for doctors to judge the severity of a disease. In health care, measuring a patient's heart rate and respiratory rate is an essential step, especially in health care that requires continuous monitoring of heart rate and respiratory rate. However, currently, the monitors used for patient care need to be in direct contact with the patient's skin when measuring respiratory rate and heart rate. Generally, electrodes need to be pasted on the body, and tapes with sensors need to be tied on. This not only causes pain or discomfort to the patient, leading to uneasiness and poor compliance of the patient, but more importantly, it cannot perform long-term measurement of vital sign parameters of the patient, thus limiting many new applications. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a vital sign device and method based on a single-ended single-fiber Michelson fiber interferometer, which does not require isolation of the sensing arm and the reference arm, has low cost and high sensitivity.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A vital sign device based on a single-ended single-fiber Michelson fiber interferometer includes a light source, a photodetector, an optical fiber coupler, a single-ended single-fiber Michelson fiber interferometer, a microcontroller unit MCU, and a terminal; the optical fiber coupler is respectively connected to the light source, the photodetector, and the single-ended single-fiber Michelson fiber interferometer; the photodetector is also connected to the terminal through the MCU.

[0006] Further, the light source adopts an FP, DFB, VECEL light source or an incoherent broadband light source.

[0007] Further, the optical fiber coupler adopts a 1×2 optical fiber coupler. The 2 end of the 1×2 optical fiber coupler is connected to the output end of the light source, the 1 end is connected to the input end of the single-ended single-fiber Michelson fiber interferometer, and the 3 end is connected to the photodetector.

[0008] Further, the single-ended single-fiber Michelson fiber interferometer includes a single-mode optical fiber and an optical fiber reflection lens; the single-mode optical fiber is connected to the optical fiber lens; the single-ended single-fiber Michelson fiber interferometer is installed in a bending member.

[0009] Further, the upper and lower surfaces of the bending member have concave and convex structures.

[0010] Furthermore, the bending member is a mesh member.

[0011] A method for manufacturing a vital sign device based on a single-ended single-fiber Michelson fiber interferometer includes the following steps:

[0012] Intercept a common single-mode optical fiber with a length of 2 - 50 cm and an inner and outer core diameter of 9 / 125 μm, which consists of a core and a cladding;

[0013] Use a carbon dioxide laser or other optical fiber fusion equipment to melt and draw an integrated Michelson sensing optical fiber with a waist cone diameter of 10 - 50 μm and an optical fiber reflection lens with a diameter of 300 - 1000 μm.

[0014] The present invention has the following beneficial effects compared with the prior art:

[0015] 1. In the single-ended single-fiber Michelson fiber interferometer sensor adopted by the present invention, the core and the cladding serve as both the reference arm and the sensing arm, without the need to isolate the sensing arm and the reference arm, with low cost and high sensitivity;

[0016] 2. The present invention effectively avoids the influence of the environment on the reference arm and has a minimalist single-ended single-fiber structure; not only coherent light sources can be used, but also incoherent light sources can be used. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of the present invention;

[0018] Figure 2 is a schematic structural diagram of a single-ended single-fiber Michelson fiber interferometer sensor in an embodiment of the present invention;

[0019] Figure 3 is a schematic packaging diagram of a single-ended single-fiber Michelson fiber interferometer sensor in an embodiment of the present invention;

[0020] Figure 4 is the original test data in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be further described below with reference to the drawings and embodiments.

[0022] Please refer to Figure 1, the present invention provides a vital sign device based on a single-ended single-fiber Michelson fiber interferometer, which includes a light source, a photodetector, a 1×2 coupler, a single-ended single-fiber Michelson fiber interferometer, a microcontroller unit MCU, and a terminal: The light source is connected to the 2-port of the 1×2 coupler through a transmission fiber, and then the 1-port of the coupler is connected to the single-ended single-fiber Michelson fiber interferometer through a transmission fiber; the 3-port of the 1×2 coupler 12 is connected to the photodetector 14; the MCU15 is connected to the photodetector 14, and the host computer / smartphone 16 is connected to the MCU15 through Bluetooth to transmit data. The host computer is generally a PC or a smartphone, and carries a vital sign parameter extraction and analysis algorithm module. The vital sign parameter extraction and analysis algorithm can also be performed in the MCU15.

[0023] Preferably, the light source adopts an FP, DFB, VECEL light source or an incoherent broadband light source. All the optical fibers are single-mode optical fibers.

[0024] Preferably, the optical fiber coupler adopts a 1×2 optical fiber coupler. The 2-end of the 1×2 optical fiber coupler is connected to the output end of the light source, the 1-end is connected to the input end of the single-ended single-fiber Michelson fiber interferometer, and the 3-end is connected to the photodetector.

[0025] Reference Figure 2 , in this embodiment, the single-ended single-fiber Michelson fiber interferometer is integrally connected into a single continuous shape, with a core and a cladding. One end is connected to the 1-port of the 1×2 optical fiber coupler, and the optical fiber with the Michelson fiber interferometer structure at the other end is installed in the upper and lower bending components. Preferably, the upper and lower bending components can be mesh components or other concave and convex components, and their function is to increase the micro-perturbation of the optical fiber by the outside world. The single-ended single-fiber Michelson fiber interferometer is made by tapering and fusing a single-mode optical fiber with an inner and outer core diameter of 9 / 125um or an optical fiber of other sizes; the diameter of the waist of the double-tapered optical fiber is 50 microns; the optical fiber reflection lens in the Michelson fiber interferometer has a diameter of 300 microns, and the length of the sensor is less than 15 cm. The optical fiber reflection lens can be coated with a metal film to improve the reflectivity.

[0026] In this embodiment, the manufacturing method of the vital sign device based on the single-ended single-fiber Michelson fiber interferometer includes the following steps:

[0027] Intercept a common single-mode optical fiber with a length of 2-50 cm and an inner and outer core diameter of 9 / 125um, which is composed of a core and a cladding;

[0028] Use a carbon dioxide laser or other optical fiber fusion equipment to melt and draw an integrated Michelson sensing optical fiber with a waist diameter of 10-50 microns and an optical fiber reflection lens with a diameter of 300-1000 microns.

[0029] In this embodiment, the MCU can be connected to the host computer or mobile phone through wireless transmission means such as Bluetooth to ensure the portability of the overall device. The vital sign parameter extraction and analysis algorithm module in the host computer or mobile phone is used to process the original signal output by the photodetector, and then obtain the vital sign parameter information.

[0030] Embodiment 1:

[0031] In this embodiment, a Michelson fiber interferometer based on a single-mode fiber adopts a dual-taper fiber-fiber reflection lens structure, and its structure is as Figure 2 shown.

[0032] The single-mode fiber selected is the Single-mode Optical Fiber ITU-T G.652.D model of CORNING Company, with a core diameter of 9 microns and a cladding diameter of 125 microns. The distance from the dual-taper fiber to the fiber reflection lens is denoted as L. According to the principle of total internal reflection of light, generally, light is confined to the core for propagation. In the Michelson fiber interferometer with this structure, when the incident light has not reached the dual-taper fiber, it only propagates in the core. When it reaches the dual-taper fiber, due to the mismatch of the mode field diameter, the cladding mode is excited. The light that was originally only transmitted in the core is divided into two beams of light and transmitted forward. One part still propagates along the core, while the other part enters the cladding. When the light reaches the fiber reflection lens, the cladding mode and the core mode are reflected and transmitted along the core and cladding. When the core mode and the cladding mode returning along the original path encounter the waist of the dual-taper fiber again, the light in the cladding and the light in the core are coupled again to form interference.

[0033] Its theoretical formula is as follows:

[0034]

[0035] In the formula, I out and I in are the light intensity of the outgoing light and the light intensity of the incident light respectively, is the coupling coefficient, is the phase difference between the sensing arm and the reference arm. The coupling coefficient , the phase difference between the sensing arm and the reference arm change with the change of the external environmental variables. Therefore, by detecting I out , the change of the external measured quantity can be known. The present invention mainly uses the external environmental variables (vibration amplitude and frequency) to disturb the fiber reflection lens to cause changes in the coupling coefficient and phase, thereby causing I out to change. By demodulating the I out signal, the external environmental variables (such as the amplitude and frequency of vibration) can be obtained.

[0036] The upper computer or mobile phone can obtain the vital sign parameter information by analyzing the signals collected by the photodetector.

[0037] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A vital sign device based on a single-ended single-fiber Michelson fiber interferometer, characterized in that, It includes a light source, a photodetector, an optical fiber coupler, a single-ended single-fiber Michelson fiber interferometer, a microcontroller unit (MCU) and a terminal; the optical fiber coupler is respectively connected to the light source, the photodetector and the single-ended single-fiber Michelson fiber interferometer; the photodetector is also connected to the terminal through the MCU; The single-ended single-fiber Michelson fiber interferometer includes a single-mode biconical fiber and a fiber reflection lens; Before the incident light reaches the biconical fiber, it only propagates in the core. When it reaches the single-mode biconical fiber, the light that originally only transmitted in the core is divided into two beams and transmitted forward. One part is transmitted along the core, and the other part enters the cladding; When the light is transmitted to the fiber reflection lens, the cladding mode and the core mode are reflected and transmitted along the core and the cladding; when the core mode and the cladding mode that return along the original path encounter the waist of the single-mode biconical fiber again, the light in the cladding and the light in the core are coupled again to form interference. The theoretical formula is as follows: Where, I out and I in are the light intensities of the outgoing light and the incident light respectively, α is the coupling coefficient, is the phase difference between the sensing arm and the reference arm; by detecting I out the change of the external measured quantity is obtained.

2. The vital sign device based on a single-ended single-fiber Michelson fiber interferometer according to claim 1, characterized in that, The light source adopts an FP, DFB, VECSEL light source or an incoherent broadband light source.

3. The vital sign device based on a single-ended single-fiber Michelson fiber interferometer according to claim 1, wherein The optical fiber coupler adopts a 1×2 optical fiber coupler. The 2 end of the 1×2 optical fiber coupler is connected to the output end of the light source, the 1 end is connected to the input end of the single-ended single-fiber Michelson fiber interferometer, and the 3 end is connected to the photodetector.

4. The vital sign device based on a single-ended single-fiber Michelson fiber interferometer according to claim 1, characterized in that, The single-ended single-fiber Michelson fiber interferometer is installed in a bending component.

5. The vital sign device based on a single-ended single-fiber Michelson fiber interferometer according to claim 4, wherein The bending component has a concave-convex structure.

6. The vital sign device based on a single-ended single-fiber Michelson fiber interferometer according to claim 4, wherein The bending component adopts a mesh component.

7. The vital sign device based on a single-ended single-fiber Michelson fiber interferometer according to claim 4, wherein The fiber reflection lens adopts a fiber reflection lens with a mirror function coated with a metal or a dielectric film.

8. The vital sign device based on a single-ended single-fiber Michelson fiber interferometer according to claim 4, wherein The fiber reflection lens has a reflectivity of 10%-100%.

9. The manufacturing method of the vital sign device based on a single-ended single-fiber Michelson fiber interferometer according to any one of claims 1-8, characterized in that, It includes the following steps: Intercept a common single-mode fiber with a length of 2-50 cm and an inner and outer core diameter of 9 / 125 um, which is composed of a core and a cladding; Adopt an optical fiber fusion splicing device to melt and draw to form an integrated Michelson sensing optical fiber with a biconical fiber having a lumbar diameter of 10-50 microns and a fiber reflection lens having a diameter of 300 microns.

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