JP2005143906A - Optical fiber for expiration sensor, optical fiber expiration sensor and expiration detecting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber expiration sensor and an expiration detecting system capable of detecting an expiration without affected by humidity conditions of outside air. <P>SOLUTION: This optical fiber expiration sensor and the expiration detecting system can greatly change the transmitted light intensity to the change in humidity under high humidity conditions by having an optical fiber core and a humidity response layer which covers the surface of the optical fiber core and includes a hydrophobic material and a hydrophilic material, and at least, forming the hydrophobic material into a meshed matrix layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical fiber for an exhalation sensor, an optical fiber exhalation sensor and an exhalation detection system, and more particularly to an optical fiber exhalation sensor and an exhalation detection system using a plastic optical fiber.

As a conventional humidity sensor using a plastic optical fiber, for example, in Patent Document 1, a moisture-sensitive layer containing mainly potassium alcohol, potassium acetate, magnesium chloride, and sodium sulfate is formed on a part of a clad covering an optical fiber. A humidity sensor is shown which is formed to detect changes in transmitted light intensity.
JP-A-5-60689

  However, in the above conventional humidity sensor, the change in transmitted light intensity with an increase in humidity shows an S-shaped curve, that is, the sensitivity and response speed of the change in transmitted light intensity with respect to the humidity change under high humidity are poor. It was sufficient and susceptible to changes in the humidity of the outside air.

  In view of the above problems, an object of the present invention is to provide an optical fiber expiration sensor and an expiration detection system that can detect expiration without being affected by humidity conditions of outside air.

  An optical fiber for breath sensor according to the present invention includes an optical fiber core, a humidity response layer that covers a surface of the optical fiber core and includes a hydrophobic substance and a hydrophilic substance, and at least the hydrophobic substance is A network-like matrix layer is formed, and the humidity response layer changes the amount of light incident from one end of the optical fiber core to the other end in accordance with the amount of moisture in the gas.

  In the breath sensor optical fiber according to the present invention, the hydrophilic substance may be a hydrophilic polymer, and the hydrophobic substance may be a water-insoluble material.

  In the breath sensor optical fiber according to the present invention, the humidity response layer uses a solution having a weight mixing ratio of the hydrophilic polymer and the water-insoluble material of 1: 1.5 to 1: 5. It may be formed.

  In the breath sensor optical fiber according to the present invention, the humidity response layer may be formed using a solution containing the hydrophilic polymer at a concentration of 0.4 wt% or more.

  An optical fiber breath sensor according to the present invention detects breath using the breath sensor optical fiber.

  The breath detection system according to the present invention uses the optical fiber breath sensor.

  ADVANTAGE OF THE INVENTION According to this invention, the sensitivity and response speed of the transmitted light intensity change under high humidity can improve, and the optical fiber exhalation sensor and the exhalation detection system which can detect exhalation without being influenced by the humidity conditions of external air can be provided.

  An optical fiber for breath sensor according to the present invention is configured by covering a core material with a clad material. That is, the breath sensor optical fiber has an optical fiber core and a humidity response layer (cladding layer) that covers the surface of the optical fiber core, and the humidity response layer includes a hydrophobic substance and a hydrophilic substance. At least the hydrophobic substance forms a network matrix layer.

  For example, a hydrophilic polymer is used as the hydrophilic substance, and a water-insoluble material is used as the hydrophobic substance. In this case, the moisture-responsive layer is formed by dissolving the hydrophilic polymer and the water-insoluble material in an appropriate solvent, applying this solution to the surface of the optical fiber core, and drying. Here, the solvent for dissolving the hydrophilic polymer and the water-insoluble material is not particularly limited as long as a uniform solution thereof can be obtained, but preferably, dimethyl sulfoxide, ethanol, or a mixed solvent of these and water is used. .

  There is no limitation on the hydrophilic polymer used as the hydrophilic substance. For example, an acrylic or cellulose polymer, particularly a cellulose polymer is preferable. The cellulose polymer is not limited, but preferably includes hydroxyethyl cellulose, carboxymethyl cellulose, carboxymethyl cellulose sodium, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl ethyl cellulose, and particularly preferably hydroxyethyl cellulose. It is done.

  The water-insoluble material used as the hydrophobic substance is not limited as long as it is a polymer that can be uniformly dissolved in the solvent to be used. For example, it is preferable to use a hydrophobic polymer, particularly a fluorine-based polymer. Although there is no restriction | limiting in a fluorine-type polymer, Preferably a polyvinylidene fluoride, a polychloro trifluoroethylene, a polyvinyl fluoride etc. are mentioned, Especially preferably, a polyvinylidene fluoride is mentioned.

  The humidity response layer changes the amount of light incident from one end of the optical fiber core to the other end (hereinafter referred to as transmitted light intensity) according to the amount of moisture in the gas (for example, humidity).

  For example, in a low-humidity environment, the transmitted light intensity of the breath sensor optical fiber is low. This is because the refractive index of the humidity response layer is higher than the refractive index of the optical fiber core under low humidity, and the optical fiber core cannot function as an optical waveguide. That is, in this case, light entering from one end of the optical fiber and passing through it leaks out of the optical fiber core from the vicinity of the humidity response layer, and the amount of light reaching the other end is reduced compared to the amount of incident light.

  Further, it is considered that the matrix layer containing at least a hydrophobic substance is formed in a mesh shape, so that it has an effect of scattering light, and promotes the reduction of the transmitted light intensity under the low humidity described above.

  On the other hand, under high humidity, the hydrophilic substance in the humidity response layer absorbs moisture in the gas and swells, and its refractive index is lower than the refractive index of the optical fiber core. It will function as a waveguide. That is, under high humidity, light that enters from one end of the optical fiber core and passes through it is totally reflected at the boundary between the optical fiber core and the humidity response layer, and reaches the other end without significant loss. Therefore, the transmitted light intensity increases as compared with the case of low humidity.

  In this way, it is possible to detect a change in the amount of moisture in the gas as a change in the transmitted light intensity by utilizing the change in the refractive index of the humidity response layer, particularly a hydrophilic substance, at low and high humidity. become. For example, when exhaled air exhaled when a human or animal breathes is blown to the humidity response layer, the transmitted light intensity of the optical fiber for the exhalation sensor increases, so that respiration can be detected.

  In particular, the humidity response layer is formed so as to have a hydrophobic matrix layer formed in a mesh shape and a dispersion layer containing a hydrophilic substance dispersed between the meshes of the matrix layer, which will be described later. Thus, even under high humidity, the transmitted light intensity can be greatly changed with respect to the change in humidity, and the response speed (change speed) of the transmitted light intensity with respect to the change in humidity can be improved.

  The humidity response layer is preferably formed using a solution of hydrophilic polymer: water-insoluble material (weight mixing ratio) = 1: 1.5 to 1: 5, more preferably 1: 2 to 1: 4. As a result, the responsiveness of the breath sensor optical fiber to changes in humidity is improved, and a large change in transmitted light intensity can be obtained even under high humidity.

  That is, if the weight mixing ratio of the water-insoluble material to the hydrophilic polymer is 1.5 or less, the water-insoluble material is not a sufficient amount. It is not preferable because it is dispersed in the form of islands, and the sensitivity of the change in transmitted light intensity with respect to the change in humidity becomes low (the amount of change in transmitted light intensity becomes small) under high humidity.

  In addition, if the weight mixing ratio of the water-insoluble material to the hydrophilic polymer is 5 or more, the hydrophilic polymer is too small and the change in transmitted light intensity with respect to the change in humidity cannot be obtained sufficiently.

  In addition, the humidity response layer is preferably made of at least a hydrophobic substance if it is formed using a uniform solution containing a hydrophilic polymer at a concentration of 0.4% by weight or more, more preferably 1.0% by weight or more. As a result, a reticulated matrix layer is formed, and the response speed to transmitted light intensity change and humidity change under high humidity can be improved.

  Further, if an optical fiber for breath sensor is used and a light source is connected to one end and a light receiver is connected to the other end, an optical fiber breath sensor that detects breath during breathing can be provided.

  Further, by using this optical fiber breath sensor and further providing a data processing function by a microcomputer, a display function on a liquid crystal display and a personal computer monitor, it is possible to easily detect a change in humidity associated with breathing of a subject (human or animal). Possible breath detection systems can be built. This exhalation detection system has a function to display apnea (a state in which breathing is not performed for a predetermined time or more) count data on a liquid crystal display or the like, so that the state of breathing can be visually grasped and breathing can be performed more clearly. The condition can be monitored. Further, as another aspect of the breath detection system, the transmitted light intensity due to actual breathing is converted into a voltage using a photoelectric conversion element or the like, and the voltage change is displayed as a waveform on a display such as a personal computer monitor. By doing so, it is possible to visually grasp the state of breathing and to monitor the breathing state more clearly.

  Furthermore, if the optical fiber breath sensor is connected to a routing POF (plastic optical fiber) and fixed to both ears, the possibility of coming off the face even when used for a long time can be minimized. Further, if a U-shaped optical fiber breath sensor having two sensor parts (parts where the humidity response layer is formed) is held, the two sensor parts are respectively held in accordance with the positions of the nose and mouth, It can handle breathing through either the nose or mouth.

  Hereinafter, an example of an embodiment of the present invention will be described. In addition, this invention is not limited by these.

[Production of optical fiber for breath sensor]
A commercially available plastic optical fiber (POF) Super Esca (registered trademark, the same shall apply hereinafter) (0.5 mm diameter, manufactured by Mitsubishi Rayon Co., Ltd.) is cut into a length of 25 cm. The sensor part was peeled off over 2.5 cm. Furthermore, the clad of the part which becomes these sensor parts was removed by immersing in an organic solvent (dioxane or the like), and only an optical fiber core of polymethyl methacrylate (PMMA) was obtained. Next, 0.48 g of hydroxyethyl cellulose (HEC) and 1.44 g of polyvinylidene fluoride (polyvinylidene fluoride, PVDF) were dissolved in 40 g of dimethyl sulfoxide (DMSO) with stirring, and the HEC for the solvent (DMSO) was A solution having a weight% concentration of 1.2% and HEC: PVDF (weight mixing ratio) = 1: 3 was prepared (first embodiment). Similarly, 0.24 g of HEC, 0.48 g, or 0.72 g of PVDF was dissolved in 40 g of DMSO with stirring, and the weight percent concentration of HEC relative to the solvent was 0.6%. HEC: PVDF (weight Solutions of mixing ratio = 1: 2 (second embodiment) or 1: 3 (third embodiment) were prepared, respectively. The optical fiber core from which the above-mentioned clad has been peeled is immersed in each of these three types of solutions, and the optical fiber core is further dried in a vacuum dryer at 50 ° C. for 12 hours to evaporate the solvent. An optical fiber was prepared. Thereafter, both end faces of the breath sensor optical fiber were polished into mirror surfaces, and a part was folded back with a curvature radius of 1 cm.

[Evaluation of humidity response and breath response of optical fiber breath sensor]
One end of the optical fiber for the breath sensor manufactured as described above is connected to a light source device having a light source such as a light emitting diode (LED), and the other end is connected to a light receiving device having a photodiode (PD) or the like. A sensor (hereinafter simply referred to as an exhalation sensor) was produced. The humidity in the air in contact with the breath sensor was changed, and the change in transmitted light intensity was measured with an optical power meter.

  The result is shown in FIG. In FIG. 1, the horizontal axis represents relative humidity (%), and the vertical axis represents the relative value of transmitted light intensity. The relative value of transmitted light intensity is the transmitted light intensity under each relative humidity when the transmitted light intensity (μW) detected by the optical power meter is 1 at 35% relative humidity, that is, at each relative humidity. The ratio of the transmitted light intensity to the transmitted light intensity at a relative humidity of 35% is calculated. FIG. 1 shows that the HEC weight percent concentration is 1.2% and HEC: PVDF = 1: 3 (black square mark), the HEC weight percent concentration is 0.6%, and HEC: PVDF = 1: 3 (outlined circle). The measurement results of the above-described three types of breath sensors having humidity response layers formed using solutions each having a HEC weight% concentration of 0.6% and HEC: PVDF = 1: 2 (black triangle mark) are shown below. It is shown. As is clear from FIG. 1, the transmitted light intensity of the breath sensor increased with an increase in relative humidity, and particularly increased under high humidity of 80% or more. In other words, the transmitted light intensity of the breath sensor changes more rapidly with changes in humidity at a high humidity corresponding to the humidity during expiration (generally 80% or more) than under the humidity corresponding to normal outside air. It showed excellent humidity responsiveness as an exhalation sensor that responds to exhalation with high sensitivity without being affected by outside air.

  Further, FIG. 2 shows the result of measuring the temporal change in transmitted light intensity when human breath is blown on the above-described breath sensor, using an optical power meter in the same manner as described above. In FIG. 2, the horizontal axis indicates the measurement time (seconds, s), and the vertical axis indicates the transmitted light intensity change rate (%). The rate of change in transmitted light intensity is 0% for the transmitted light intensity in a state where no breathing is normal, and 100% for the maximum value of the transmitted light intensity that is changed when exhalation is blown. The ratio of light intensity is calculated. When the response time is evaluated as the response time when the rate of change in transmitted light intensity decreases from 100% to 50%, as shown in FIG. 2, the transmitted light intensity of the breath sensor increases rapidly as the breath is blown. The response time was within a few seconds. That is, it was shown that the transmitted light intensity can be quickly changed in accordance with the breathing timing.

  1 and 2, the breath sensor according to the present invention changes the transmitted light intensity with high sensitivity and high response speed (short response time) according to the amount of moisture in the gas, and in particular, has a higher humidity than in the outside air. It was shown that it has excellent breath sensor characteristics below.

[Surface observation of optical fiber breath sensor]
FIGS. 3 and 4 were formed using solutions each having a HEC weight percent concentration of 1.2% and HEC: PVDF = 1: 3, a HEC weight percent concentration of 0.6% and HEC: PVDF = 1: 3. The result of having observed the surface of the humidity response layer with the scanning electron microscope S-3000N (made by Hitachi, Ltd.) is shown. In the elemental analysis using an energy dispersive X-ray analyzer (EMAX ENERGY, manufactured by HORIBA, Ltd.), the surface of the optical fiber breath sensor observed by a scanning electron microscope is used to confirm the distribution of fluorine. The existence of That is, in FIGS. 3 and 4, the matrix layer containing at least PVDF is shown as a two-dimensional or three-dimensional white mesh (arrow A), and the dispersion layer containing HEC is located between the matrix meshes. Are dispersed in islands and shown in black (arrow B).

[Fixing optical fiber breath sensor to face]
Next, a method of using the above-described exhalation sensor fixed to a human face will be described. FIG. 5 is an explanatory diagram showing an example thereof. The breath sensor 10 has a nasal sensor part 12 and a mouth sensor part 14 covered with a humidity response layer, and a curved part 16 that connects these parts, and a part of the curved part 16 is bent with a radius of curvature of 1 cm. ing.

  As shown in FIG. 5, the nose sensor part 12 and the mouth sensor part 14 of the breath sensor 10 are arranged so as to be located in front of the subject's nose N and mouth M, respectively, and the bent part of the bending part 16 Are connected to the drawing string 18, and both ends (one end of the nose sensor unit 12 or the mouth sensor unit 14) are respectively connected to the drawing POF 20, and these drawing parts (the drawing string 18 and the drawing POF 20). ) Over both ears E and fixed under the jaw C. The two routing POFs 20 are respectively connected to the above-described light emitting device or light receiving device (not shown). Furthermore, it is possible to fix the breath sensor 10 on both cheeks with a tape or the like so that the breath sensor 10 can be more firmly fixed. Moreover, the part to bundle is movable up and down, and the size can be adjusted.

[Production of exhalation detection system]
Next, an example of the breath detection system according to the present invention will be described. The schematic configuration is shown in FIG. The exhalation detection system shown in FIG. 6 includes, for example, an exhalation sensor unit 30 including an exhalation sensor 10 as shown in FIG. 5, a light emitting unit 40, a light receiving unit circuit 50, a microcomputer circuit 60, a liquid crystal display unit 70, an A / D (analog) / Digital) conversion unit 80 and display unit 90. For example, an LED is used for the light emitting unit 40 and a PD is used for the light receiving unit circuit 50, for example, and the breath sensor unit 30 is connected therebetween. The light that enters the breath sensor unit 30 from the light emitting unit 40 and passes through it is converted into a current in the light receiving unit circuit 50 to generate a voltage. This voltage is increased or decreased by changing the transmitted light intensity by blowing exhalation according to the property of the above-described exhalation sensor. The generated voltage is amplified by an amplifying circuit, and a digital signal is generated through an A / D conversion unit 80 including an A / D conversion element, thereby displaying a voltage increase / decrease due to respiration as a waveform on a display unit 90 such as a personal computer monitor. it can.

  FIG. 7 shows an example of the result of displaying the voltage change accompanying the exhalation on the display unit 90 as a waveform in the above-described exhalation detection system. In FIG. 7, the horizontal axis represents the measurement time (s), and the vertical axis represents the voltage (V) generated by blowing exhalation to the exhalation sensor unit 30. In FIG. 7, it is shown that the above-described breath detection system can detect respiration as a change in voltage with high sensitivity and high response speed, and can further clearly display this change in voltage visually.

  Further, by the data processing by the microcomputer of the microcomputer circuit 60 with respect to the output from the light receiving unit circuit 50, for example, the apnea count number, apnea time (unit: second), current voltage (unit: V) 3 The two states can be displayed on the liquid crystal display unit 70 such as a liquid crystal display, and the apnea detection system can be diagnosed by the breath detection system.

  The data processing program by the microcomputer in the microcomputer circuit 60 is, for example, as follows. That is, when the amount of change or rate of change in voltage due to respiration falls below a certain threshold value that has been set, it is determined that the patient is in an apnea state, and the time is measured. When the state continues for 10 seconds or more, the apnea count is set to +1. If the voltage exceeds a certain threshold due to breathing during an apneic state, the apneic state is immediately reset.

  As described above, according to the present invention, the surface of the optical fiber core is coated with a humidity response layer that includes a hydrophobic substance and a hydrophilic substance, and at least the hydrophobic substance forms a network-like matrix layer. The humidity response layer is an optical fiber breath sensor that changes the amount of light incident from one end of the optical fiber core to the other end according to the amount of moisture in the gas. The expiration can be detected without being influenced by the humidity condition of the outside air.

  In addition, the breathing state is visually monitored by providing an expiration detection system with a plastic optical fiber breath sensor and a microcomputer data processing function, an apnea count display on a liquid crystal display, and a waveform display function on a personal computer monitor. It is possible to apply to various diagnosis by storing data.

  In addition, the sensor unit has two sensor parts, the sensor connecting the two parts is a U-shaped sensor, the sensor is connected to the routing POF, and the sensor is attached to both ears. It can cover the breathing of the nose and can provide stability that does not come off even when used for a long time.

  In addition, since the breath sensor according to the present invention is highly sensitive and highly responsive, it can also be used as a non-contact breath sensor that can detect respiration without directly contacting the subject. It is also possible to target a subject with a wound at the contact location, a newborn infant, an infant, or a small animal that is difficult to keep consciously in contact with. It is also possible to detect these slight changes in breathing.

[Comparative experiment example]
Next, the result of a comparative experiment performed on the present invention will be shown.

[Production of optical fiber for breath sensor]
A commercially available plastic optical fiber Super Esca (0.5 mm diameter, manufactured by Mitsubishi Rayon) is cut to a length of 25 cm, the sensor part for the nose is 3 cm, and the sensor part for the mouth is 2.5 cm. The coating was removed. Then, the clad of the part which becomes a sensor part was removed by immersing in dioxane, and only the core of PMMA was obtained.

  Next, as a first comparative example (Comparative Example 1), 0.48 g of HEC and 0.32 g of PVDF were dissolved in 40 g of DMSO while stirring, and the concentration of HEC relative to the solvent was 1.2% by weight, A solution of HEC: PVDF (weight mixing ratio) = 3: 2 was prepared. After immersing the above core while stirring the prepared solution, it was dried in a vacuum oven at 50 ° C. for 15 hours to produce an optical fiber for a breath sensor in which a humidity response layer was formed on the PMMA core.

  Further, as a second comparative example (Comparative Example 2), 0.48 g of HEC and 0.32 g of PVDF were mixed in 40 g of a mixed solvent of water: ethanol (weight mixing ratio) = 1: 1, and HEC for the solvent was mixed. A solution having a concentration of 1.2% by weight and HEC: PVDF (weight mixing ratio) = 3: 2 was prepared. After immersing the above-mentioned core while stirring the prepared solution, it was dried at 22 ° C. for 15 hours to produce an optical fiber for a breath sensor in which a humidity response layer was formed on the core of PMMA.

  As a third comparative example (Comparative Example 3), 0.12 g of HEC and 0.28 g of PVDF were dissolved in 40 g of DMSO while stirring, and the concentration of HEC relative to the solvent was 0.3% by weight, A solution of HEC: PVDF (weight mixing ratio) = 1: 2.33 was prepared. After immersing the above core while stirring the prepared solution, it was dried in a vacuum oven at 50 ° C. for 15 hours to produce an optical fiber for a breath sensor in which a humidity response layer was formed on the PMMA core.

[Humidity response evaluation of optical fiber breath sensor]
Both ends of the breathable sensor optical fiber manufactured as described above are polished to be mirror surfaces, and both ends are connected to the light source device Photo370HS (made by Hacrotonics) and the light receiving device Photo228 (made by Hacrotonics), respectively. The change in transmitted light intensity in the range of 35% to 95% humidity was measured with an optical power meter. At this time, the optical fiber breath sensor was measured in a linear state.

  For Comparative Examples 1 and 2, the correlation between humidity and transmitted light intensity change is shown in FIG. The horizontal and vertical axes in FIG. 8 are the same as those in FIG. FIG. 8 shows that both the optical fiber breath sensors of Comparative Example 1 (outlined circle mark) and Comparative Example 2 (black triangle mark) show humidity-dependent transmitted light intensity, but in the vicinity of high humidity. The change in transmitted light intensity is extremely small as compared with the result of FIG. 1, and it is shown that the sensor characteristics for detecting exhalation under high humidity are insufficient.

  For Comparative Example 3, the correlation between the humidity and the change in transmitted light intensity is shown in FIG. In FIG. 9, the degree of change in transmitted light intensity with respect to humidity change (transmitted light intensity change rate) is much smaller than the result shown in FIG. 1, and a solution having an HEC concentration of 0.3% or less is used. An optical fiber breath sensor with a humidity response layer formed using it has been shown to be insufficient for detection of breath.

[Surface observation of breath sensor optical fiber]
Next, the result of having observed the humidity response layer surface of the optical fiber for breath sensors mentioned above with the scanning electron microscope S-3000N (made by Hitachi, Ltd.) is shown in FIG.10 and FIG.11. 10 and 11 that PVDF, which is a hydrophobic substance, is dispersed in the form of particles on the PMMA core, that is, the hydrophobic substance is not formed in a mesh shape, but is formed in a particle shape on the surface of the humidity response layer. (Arrow A). The particle size of the hydrophobic material was approximately 1 μm to 10 μm.

  As described above, an exhalation sensor in which at least a hydrophobic substance does not form a mesh-like matrix layer in the humidity response layer has a small response to transmitted light intensity under high humidity and is easily affected by the outside air.

It is a figure which shows the result of having measured the transmitted light intensity change with respect to relative humidity about the optical fiber breath sensor which concerns on the 1st thru | or 3rd embodiment of this invention. It is a figure which shows the result of having measured the time change of the transmitted-light intensity | strength accompanying blowing of expiration | expiration about the optical fiber breath sensor which concerns on the 1st thru | or 3rd embodiment of this invention. It is a figure which shows the result of having observed the humidity response layer of the optical fiber breath sensor which concerns on 1st embodiment of this invention with the scanning microscope. It is a figure which shows the result of having observed the humidity response layer of the optical fiber breath sensor which concerns on 3rd embodiment of this invention with the scanning microscope. It is a figure which shows the attachment method to the face of the optical fiber breath sensor which concerns on one Embodiment of this invention. 1 is a block diagram showing a schematic configuration of an exhalation detection system according to an embodiment of the present invention. It is a figure which shows the result of having displayed the time change of the voltage accompanying respiration as a waveform about the breath detection system which concerns on one Embodiment of this invention. It is a figure which shows the result of having measured the transmitted light intensity change with respect to relative humidity about the optical fiber breath sensor which concerns on the 1st and 2nd comparative example with respect to this invention. It is a figure which shows the result of having measured the transmitted light intensity change with respect to relative humidity about the optical fiber breath sensor which concerns on the 3rd comparative example with respect to this invention. It is a figure which shows the result of having observed the humidity response layer of the optical fiber breath sensor which concerns on the 1st comparative example with respect to this invention with the scanning microscope. It is a figure which shows the result of having observed the humidity response layer of the optical fiber breath sensor which concerns on the 2nd comparative example with respect to this invention with the scanning microscope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Exhalation sensor, 12 Nasal sensor part, 14 mouth sensor part, 16 Curved part, 18 Routing string, 20 Routing POF, 30 Exhalation sensor part, 40 Light emitting part, 50 Light receiving part circuit, 60 Microcomputer circuit, 70 Liquid crystal Display unit, 80 A / D conversion unit, 90 display unit.

Claims (6)

An optical fiber core, and a humidity response layer that covers a surface of the optical fiber core and includes a hydrophobic substance and a hydrophilic substance;
At least the hydrophobic substance forms a network-like matrix layer;
The breathing sensor optical fiber, wherein the humidity response layer changes the amount of light incident from one end of the optical fiber core to the other end in accordance with the amount of moisture in the gas. The hydrophilic substance is a hydrophilic polymer;
The breathable sensor optical fiber according to claim 1, wherein the hydrophobic substance is a water-insoluble material.   The breath according to claim 2, wherein the humidity response layer is formed using a solution having a weight mixing ratio of the hydrophilic polymer and the water-insoluble material of 1: 1.5 to 1: 5. Optical fiber for sensors.   The breathable sensor optical fiber according to claim 2 or 3, wherein the humidity response layer is formed using a solution containing the hydrophilic polymer at a concentration of 0.4 wt% or more.   An optical fiber breath sensor that detects breath using the breath sensor optical fiber according to any one of claims 1 to 4. An expiration detection system using the optical fiber expiration sensor according to claim 5.