CN203894159U - Relative humidity monitoring system based on long-period fiber grating - Google Patents

Abstract

The utility model relates to a relative humidity monitoring system based on a long-period optical fiber grating. The light emitted by a broadband light source is divided into two paths by a Y-shaped coupler, and is respectively incident on the surface through a single-mode optical fiber to the long-period of humidity-sensitive materials wrapped on the surface. Optical fiber reference grating and long-period optical fiber sensing grating, the long-period optical fiber reference grating is placed inside the moisturizing tube, and the transmission intensity remains unchanged, while the long-period optical fiber sensing grating is exposed, and the transmission intensity will change due to the humidity change of the external environment, and then After passing through the outgoing single-mode optical fiber, photoelectric detector, electrical signal amplifier, and signal processing device in turn, it is input to the voltage divider, and the output analog voltage is calculated by the algorithm to display the measured relative humidity by the single-chip computer system. The utility model senses the humidity of the surrounding environment through the long-period optical fiber sensing grating coated with humidity-sensitive materials to generate transmitted light of different intensities, and real-time monitors the relative humidity of the environment by demodulating the light intensity. It has powerful functions, high precision, and simple operation. High security advantages.

Description

A Relative Humidity Monitoring System Based on Long Period Fiber Bragg Grating

technical field

The utility model relates to optical fiber sensing technology, photoelectric detection technology and a single-chip microcomputer system. The relative humidity threshold can also be realized by artificially setting in the single-chip microcomputer system. It belongs to the technical field of optoelectronic integration. the

Background technique

Relative humidity has always been one of the parameters that must be strictly controlled in terms of life, production, storage of materials, and fire prevention. For example, in winter, the relative humidity at home should be kept at 65%. For example, the common optical glass used for making optical lenses, because the film material coated on its surface provides rich nutrients for the growth of mold, when the relative humidity is greater than 40%. When storing flammable and explosive items, the relative humidity must be kept below 55% to effectively prevent fires. Therefore, a system that can monitor humidity in real time with adjustable relative humidity threshold alarm function came into being. the

Optical fiber sensors have the characteristics of anti-electromagnetic interference, high sensitivity, small size, corrosion resistance, and low cost. The humidity sensor based on the long-period fiber grating has good stability, and is simple to manufacture, low in cost and high in sensitivity. The utility model utilizes the surface of the long-period grating to coat a layer of uniform humidity-sensitive material to realize humidity sensing. the

Utility model content

The utility model utilizes optical fiber sensing technology, photoelectric detection technology and single-chip microcomputer technology. It has the function of monitoring the relative humidity of the surrounding environment and at the same time performing a buzzer alarm function when the relative humidity of the environment exceeds a preset threshold, and the preset relative humidity threshold It can be realized by setting artificially in the single-chip microcomputer system. the

The utility model is characterized in that the broadband light source, Y-type coupler, incident single-mode optical fiber, long-period optical fiber reference grating, long-period optical fiber sensing grating, humidity sensitive material, moisturizing tube, outgoing single-mode optical fiber, photoelectric Detector, electric signal amplifier, signal processing device, voltage divider, single-chip microcomputer system. (claim 1)

The phase matching condition that the long-period fiber grating described in the utility model needs to satisfy is: λ _res ^m =(n _eff ^co -n _eff ^{cl, m} ) ^Λ , where λ _res ^m represents the resonant wavelength, n _eff ^co and n _eff ^{cl, m} represent the effective refractive index of the core fundamental mode and the first-order m cladding mode, and Λ is the grating period.

The humidity sensitive material described in the utility model is a hydrogel, and its refractive index will change with the change of the external relative humidity, thereby affecting the transmission spectrum of the long-period grating, which is specifically manifested in the increase of the relative humidity. , the refractive index of the hydrogel will increase, so that the effective refractive index of the first-order m cladding mode will increase, so that the resonance wavelength will shift to the short wavelength direction. When the wavelength detected by the silicon photodiode is greater than the original resonance wavelength of the long-period fiber grating When the light intensity at the detection wavelength increases, the corresponding electrical signal will also increase. According to investigations, the best relative humidity for most materials is about 40%. Therefore, in the utility model, a The long-period fiber grating is placed in the moisturizing tube to ensure that the relative humidity around it is 40%, and it is used as the long-period fiber grating reference. the

The signal processing device has a filtering and voltage stabilizing circuit, which can reduce the noise of the voltage signal passing through the electric signal amplifier, and can output stably and send it to the voltage divider. the

The voltage divider has a strong ability to resist the noise of the sensor output by factors other than humidity, and it can further realize the voltage stabilization function when it is placed behind the signal processing device for calculation. the

The single-chip microcomputer system described in the utility model is composed of an A/D acquisition module, an artificial button module, a buzzer alarm module and a liquid crystal display module. The buzzer works to realize the alarm, and the relative humidity threshold of the alarm can be set artificially. the

The utility model has the following characteristics and advantages: 1. Powerful function, can realize three functions of monitoring, alarm and alarm threshold adjustment; The grating is compared with the long-period optical fiber sensor grating signal to reduce the occurrence of false alarms; 3. The operation is simple, and only the artificial button module in the single-chip system needs to be adjusted manually; 4. High safety, no harm to the human body. the

Description of drawings

Fig. 1 is a system frame diagram of the present utility model

Figure 2 is a schematic diagram of the working principle of the utility model

Fig. 3 is the working frame diagram of the single-chip microcomputer system of the present utility model

Detailed ways

The utility model is suitable for real-time monitoring, and can generate an alarm when the relative humidity exceeds 40%. the

Below in conjunction with accompanying drawing, the implementation steps of the present utility model are described:

As shown in Figure 1, this is the system frame diagram of the present utility model, the broadband light source 1 sends out the light signal that the spectral range is 1400nm-1600nm, through the Y-type coupler 2, the light is distributed to the long-period optical fiber in a ratio of 1:1 The reference grating 4 and the long-period optical fiber sensing grating 5, both of which have a resonance wavelength of 1450nm, have been coated with the same uniform humidity-sensitive material 6, i.e. hydrogel, and the long-period optical fiber reference grating 4 is sealed at a relative humidity of In the 40% moisturizing tube 7, the long-period optical fiber sensing grating 5 is used to sense the relative humidity of the surrounding environment to generate transmitted light of different intensities, and then the transmitted light passing through the two gratings passes through the same photodetector 9, namely silicon photoelectric Diode, it has a high detection sensitivity to wavelengths around 1550nm, so that the optical signal will be converted into an electrical signal. Since the electrical signal is relatively weak, a larger voltage signal is generated by the same electrical signal amplifier 10 respectively, and then passed through the same electrical signal amplifier 10. The same signal processing device 11, which is composed of filtering and voltage stabilizing circuits, can remove the noise from the amplified voltage signal and stably transmit it to the voltage divider 12, and the voltage signal from the long-period fiber reference grating 4 line is connected to The input negative terminal of the voltage divider 12, and the voltage signal that the long-period optical fiber sensing grating 5 lines come out is connected to the input positive terminal of the voltage divider 12, and the output terminal is connected to the single-chip microcomputer system 13, and the alarm function can be realized through its internal processing. the

As shown in Figure 2, this is a schematic diagram of the working principle of the present utility model. When adding humidity to the long-period fiber grating coated with hydrogel, the refractive index of the hydrogel will increase, making the first-order m cladding mode The effective refractive index will increase, so that the resonance wavelength will move to the short-wave direction. For example, when the humidity is constant, the resonance wavelength is 1450nm, and when the relative humidity increases, the resonance wavelength will move to a wavelength shorter than 1450nm. When the silicon photoelectric When the wavelength detected by the diode is greater than 1450nm, such as around 1550nm, the transmitted light intensity at that place will be greater than the intensity when the original humidity remains unchanged, so the added relative humidity can be characterized by detecting the increased light intensity. the

As shown in Figure 3, this is the working frame diagram of the single-chip microcomputer system used in the utility model, wherein A/D sampling module, artificial button module, buzzer alarm module and liquid crystal display module are housed, A/D sampling module is composed of Single-chip microcomputer control, the analog voltage output by the voltage divider 12 is converted into a digital voltage and sent to the single-chip microcomputer, and the digital voltage is converted into the corresponding relative humidity through the single-chip microcomputer program, and the relative humidity threshold of the alarm is set to 40% by the artificial key module at the same time, the single-chip microcomputer Firstly, the detected relative humidity and the relative humidity alarm threshold preset by human buttons are displayed on the LCD screen, and secondly, the detected relative humidity is compared with the threshold humidity preset by human buttons to control the work of the buzzer , when the detected relative humidity is greater than or equal to the threshold humidity, the buzzer works to realize the alarm function, and changing the preset alarm humidity can realize the alarm function for different relative humidity thresholds. the

Those skilled in the art clearly know that according to the method of the present invention, the wavelength of the broadband light source and the structure of the long-period fiber grating can be optimized, and the combination of the photodetector and the single-chip microcomputer system can also be optimized. The protection scope of the present invention does not Not limited to the above examples. the

Claims (10)

1. A relative humidity monitoring system based on long-period fiber gratings, characterized in that: the light sent by the broadband light source (1) is divided into two paths by the Y-type coupler (2), and is separated through the incident single-mode optical fiber (3). A long-period optical fiber reference grating (4) and a long-period optical fiber sensing grating (5) that are incident on the surface and are wrapped with humidity-sensitive materials (6). The long-period optical fiber reference grating (4) is placed inside the moisture tube (7) The intensity remains unchanged, while the long-period optical fiber sensing grating (5) is exposed, and the transmitted light intensity changes due to the humidity change of the external environment, and then passes through the outgoing single-mode optical fiber (8), photodetector (9), and After the electric signal amplifier (10), the signal processing device (11), the input voltage divider (12) displays the relative humidity of the current environment after the output voltage signal is processed by the single-chip microcomputer system (13), and when the relative humidity of the environment exceeds the preset During threshold value, be controlled to report to the police by single-chip microcomputer system (13). the 2. A relative humidity monitoring system based on long-period fiber gratings according to claim 1, characterized in that: the broadband light source (1) has a spectral range in the infrared band and is used as a transmission light source. the 3. a kind of relative humidity monitoring system based on long-period fiber grating according to claim 1, it is characterized in that: described Y-type coupler (2) is fusion draw-taper type single-mode fiber coupler, splitting ratio is 1 : 1. the 4. a kind of relative humidity monitoring system based on long-period fiber grating according to claim 1, is characterized in that: the structural parameter of described long-period fiber-optic reference grating (4) and long-period fiber-optic grating (5), The manufacturing process is completely the same, and the resonant wavelength must be within the spectral range of the broadband light source (1). the 5. a kind of relative humidity monitoring system based on long-period fiber grating according to claim 1, is characterized in that: described humidity sensitive material (6) is made up of hydrogel, and the structure of this material and refractive index can change with Changes with changes in external humidity. the 6. A relative humidity monitoring system based on long-period fiber Bragg gratings according to claim 1, characterized in that: said moisturizing tube (7) can ensure that the relative humidity inside it is a fixed value according to usage requirements. the 7. A kind of relative humidity monitoring system based on long-period fiber grating according to claim 1, is characterized in that: described photodetector (9) is a silicon photodiode, is greater than the long-period fiber reference grating (4) and the wavelength of the resonant wavelength of the long-period fiber sensing grating (5) is detected. the 8. A relative humidity monitoring system based on long-period fiber gratings according to claim 1, characterized in that: the signal processing device (11) is composed of filtering and voltage stabilizing circuits. the 9. A kind of relative humidity monitoring system based on long-period fiber grating according to claim 1, it is characterized in that: the input negative end of described voltage divider (12) connects long-period fiber reference grating (4) this line , the input positive end is connected to the line of long-period optical fiber sensing grating (5). the 10. a kind of relative humidity monitoring system based on long-period fiber grating according to claim 1, is characterized in that: described single-chip microcomputer system (15) is by A/D acquisition module, artificial button module, buzzer alarm module Composed of a liquid crystal display module, the relative humidity of the environment is displayed on the liquid crystal display. When the preset relative humidity threshold is exceeded, the buzzer will work to realize the alarm and the relative humidity threshold of the alarm can be artificially set. the