CN111829984A - A Fabry-Perot high humidity sensor and its measurement method - Google Patents

Abstract

The invention provides a Fabry-Perot high humidity sensor and a measurement method thereof, and relates to the technical field of optical fiber biological sensing. It is led out and fixed on the slide rail through the optical fiber fixing piece. The optical fiber fixing piece is connected with the two ends of the spider pulling wire respectively on one side of the moving reflective surface, and the other side of the moving reflective surface is connected with the spring fixing piece fixed on the sliding rail through a micro spring. . The invention utilizes the super-shrinkage characteristics of spider pulling silk after absorbing moisture, and builds a Fabry-Perot cavity with variable cavity length, so that the interference spectrum of the reflected light from the end face of the optical fiber probe and the reflected light from the moving reflecting surface has different effects under different humidity. free spectral long range. The super-shrinkage characteristics of spider pulling silk are used for humidity measurement, so that the humidity sensor has the characteristics of good natural degradability, biocompatibility, high sensitivity and high response speed under high humidity conditions.

Description

A Fabry-Perot high humidity sensor and its measurement method

technical field

The invention relates to a Fabry-Perot high humidity sensor and a measurement method thereof, belonging to the technical field of optical fiber biological sensing.

Background technique

With the rapid development of science and technology, humidity monitoring is widely used in instrumentation, automation systems, agriculture, meteorology, geographic information and other fields. People pay more and more attention to the monitoring of environmental humidity. Among various humidity detection technologies, optical fiber humidity sensing technology has developed rapidly due to its characteristics of anti-electromagnetic interference, corrosion resistance, excellent light guiding performance and high sensitivity. Today, under the call of green economy and green technology, the sensor field pays more and more attention to the impact of products on human health and the environment, that is, the biocompatibility and environmental friendliness of sensors are required. The optical fiber biosensor designed by combining biological materials with optical fiber sensing technology is a device that uses natural cells, tissues and other biological materials in nature for sensing, so it has good biocompatibility and degradability, and is conducive to Environmental protection.

Spider silk is a biological protein produced from spider silk glands. It can not only be degraded naturally, has good biocompatibility, but also has high strength, good elasticity, and excellent optical and mechanical properties. A spider can produce seven kinds of spider silk with different characteristics, among which spider pulling silk is also called "spider's life fiber", which attracts the interest of researchers. Spider traction silk is a very special biological protein polymer, which has super-shrinking properties under the influence of humidity. When the relative humidity is greater than 70% RH, the pull wire shrinks axially and can reach up to 50% of its length (Journal of Experimental Biology, 2009, 212 (13:1981-1989). In 2019, Novais et al. As a humidity sensitive medium, glue can achieve humidity detection from 20%RH to 98.5%, but the total spectral drift in the entire humidity detection range is only 2.5nm, and the humidity sensitivity in the high humidity range from 60%RH to 98.5%RH is only 44.2 pm/%RH (Humidity sensor based on optical fiber coated with agarose gel, Optical Sensors, 2019). However, spider traction silk can respond extremely sensitively to high humidity areas greater than 70% RH, and the length shrinkage can be as high as approx. 50% (Nature, 2002, 416 (6876: 37-37), the length change of spider silk directly determines its sensing sensitivity, so it can be used as humidity sensing in high humidity range.

Taking advantage of the significant shrinkage of the spider pulling silk length under high humidity, a Fabry-Perot interference cavity with variable cavity length can be constructed, and the environment can be characterized by the change of the free spectral range of the output interference spectrum caused by the change of the cavity length. humidity. Compared with common humidity sensors, the super-contraction property of spider pulling silk makes the humidity sensor based on it have extremely high sensitivity in the high humidity range greater than 70%RH. Traditional humidity sensors based on the Fabry-Perot interference principle usually monitor the red-shift or blue-shift change of the output spectrum caused by humidity. In 2018, Peng J et al. used the Fabry-Perot cavity interference structure to achieve humidity measurement in the range of 30% RH to 90% RH, and the total drift of the interference spectral line was about 10 nm (Applied Optics, 2018, 57 (12:2967). -2972). In the same year, Li C et al. used the Fabry-Perot interference structure to achieve humidity measurement in the range of 10% RH to 90% RH, and the total drift of the interference spectrum was about 15 nm (Optics Letters, 2018, 43 (19: 4719-4722). At present, there is no Fabry-Perot humidity sensor made by using the super-contraction property of spider silk, and the super-contraction property of spider pulling silk makes the length of spider silk shrink by more than 50% under high humidity conditions, which can drive The designed Fabry-Perot interference cavity length achieves a shrinkage change of nearly 50%, which is larger and more obvious than the cavity length change of the traditional Fabry-Perot humidity sensor. Therefore, the monitored quantity is not interference The amount of redshift or blueshift of the spectrum, but the change of the free spectral range of the interference spectrum. The change of the free spectral range is more obvious than the redshift or blueshift of the spectral line, which is easier to monitor and more accurate to analyze.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a low-cost, high-sensitivity, non-polluting and biocompatible optical fiber bio-humidity sensor based on the super-contraction characteristic of spider pulling silk and its measurement method.

The purpose of the present invention is achieved as follows: including incident light source 1, incident light waveguide 2, optical fiber circulator 3, optical fiber probe 4, optical fiber fixing member 4-1, spider pulling wire 5, moving reflection surface 6, slide rail 6-1 , a miniature spring 7, a spring holder 8, an outgoing optical waveguide 9 and a photodetector 10, the incident light source 1 and the ① port of the optical fiber circulator 3 are connected through the incident optical waveguide 2, and the optical fiber probe 4 is led out from the ② port of the optical fiber circulator 3 And fixed on the slide rail 6-1 by the optical fiber fixing member 4-1, the spider pulling wire 5 is arranged between the optical fiber fixing member 4-1 and one side of the moving reflection surface 6, and the other side of the moving reflection surface 6 is connected with the micro spring 7 through the micro spring 7. The spring fixing member 8 fixed on the slide rail 6-1 is connected; the optical detector 10 is connected with the ③ port of the optical fiber circulator through the outgoing optical waveguide 9 .

The present invention also includes such structural features:

1. The end face of the fiber probe 4 and the moving reflection surface 6 form a Fabry-Perot interference cavity, a part of the outgoing light is reflected on the end face of the fiber probe 4, and the other part of the outgoing light is reflected on the moving reflecting surface 5 after being emitted by the fiber probe 4 and returns. The two beams of reflected light interfere with each other when they are emitted into the fiber probe 4, and the optical detector 10 monitors and obtains the interference spectrum.

2. The spider pulling silk 5 has super-contraction characteristics, and starts to shrink when the humidity is greater than 70%, overcomes the pulling force of the miniature spring 7 and pulls the moving reflection surface 6 to move close to the fiber probe 4; when the humidity decreases, the spider pulling wire 5 The super-contraction is weakened, the pulling force is reduced, and the pulling force of the miniature spring 7 cannot be overcome, and the moving reflection surface 6 moves away from the optical fiber probe 4 under the pulling force of the miniature spring 7; The shrinkage of 50% of its axial length leads to a significant change in the length of the Fabry-Perot cavity.

3. The Fabry-Perot high humidity sensor is placed in the humidity test environment. The length of the Fabry-Perot cavity changes with the humidity driven by the super-contraction of the spider pulling silk. The length of the Fabry-Perot cavity is related to the spectrometer. The free spectral range of the measured double-beam interference spectrum is negatively correlated; by detecting the change of the free spectral range of the interference spectrum, the change of the humidity of the environment is measured.

Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention utilizes the natural super-contraction characteristics of spider pulling silk to construct a Fabry-Perot interference structure with variable cavity length, and the output interference spectrum can be used when the humidity exceeds the super-contraction characteristic. When shrinking the threshold, a large change in the free spectral range is generated, which plays a sensing role; 2. The present invention does not use any artificial synthetic materials for humidity detection. Compared with materials, it also has the advantage of low cost and can be taken from spiders at any time; 3. Products made by combining spider pulling silk and optical fiber devices are compatible with other optical and electrical devices, and can be connected to various transmission applications. In the system, it is beneficial to be compatible with the existing fiber line integration.

Description of drawings

Figure 1 is an overall structural diagram of a Fabry-Perot high humidity sensor based on the super-shrinkage characteristics of spider silk;

FIG. 2 is a schematic diagram of the principle of the Fabry-Perot high humidity sensor based on the super-shrinkage characteristic of spider silk according to the present invention.

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

As shown in Figure 1, a Fabry-Perot high humidity sensor based on the super-shrinkage characteristics of spider silk includes an incident light source 1, an incident optical waveguide 2, an optical fiber circulator 3, an optical fiber probe 4, an optical fiber fixing member 4-1, and a spider pulling Wire 5, movable reflection surface 6, slide rail 6-1, miniature spring 7, spring fixing member 8, outgoing optical waveguide 9 and photodetector 10; wherein, the ① port of the incident light source 1 and the optical fiber circulator 3 passes through the incident optical waveguide 2 connection, the fiber probe 4 is led out from the ② port of the fiber optic circulator 3 and fixed on the slide rail 6-1 by the fiber fixing piece 4-1, and the fiber fixing piece 4-1 and the side of the moving reflection surface 6 are drawn by the spider 5 The two ends are respectively connected, and the other side of the movable reflection surface 6 is connected with the spring fixing member 8 fixed on the slide rail 6-1 through the micro spring 7. The reflective end face of the fiber probe and the moving reflective face are parallel and on the same line to form a Fabry-Perot cavity.

The Fabry-Perot interference cavity is composed of the end face of the fiber probe 4 and the moving reflection surface 6. A part of the outgoing light is reflected on the end face of the fiber probe 4, and the other part of the light is reflected on the moving reflection surface 5 after being emitted by the fiber probe 4 and is retroreflected to the optical fiber probe 4. In the fiber probe 4, the two beams of reflected light interfere, and the optical detector 10 monitors and obtains the interference spectrum.

The spider pulling silk 5 has super-contraction characteristics, and starts to shrink when the humidity is greater than 70%, overcomes the pulling force of the micro-spring 7 and pulls the moving reflecting surface 6 to move close to the fiber probe 4; when the humidity decreases, the spider pulling wire 5 super-contracts weakened, the pulling force is reduced, and the pulling force of the miniature spring 7 cannot be overcome, and the moving reflecting surface 6 moves away from the optical fiber probe 4 under the pulling force of the miniature spring 7; The shrinkage of the % axial length leads to a significant change in the length of the Fabry-Perot cavity.

Test method of the present invention is:

The Fabry-Perot cavity interferometric structure sensor itself is placed in the humidity test environment. The length of the Fabry-Perot cavity changes with the humidity driven by the super-contraction of the spider pulling silk. The length of the Fabry-Perot cavity is related to the spectrometer. The measured free spectral range of the double-beam interference spectrum has a negative correlation; by detecting the change in the free spectral range of the interference spectrum, the change in the humidity of the environment can be measured.

The working principle of the present invention:

The incident light 11 enters the optical fiber circulator through the incident light wave guide and exits from the optical fiber probe. Since the end face of the optical fiber probe and the moving reflecting surface form a Fabry-Perot cavity structure, the reflected light 12 from the end face of the optical fiber probe and the reflected light 13 from the moving reflecting surface interfere. And the interference light 14 is transmitted from the outgoing optical waveguide to the photodetector through the optical fiber circulator; the optical fiber probe and the moving reflecting surface are connected by the spider pulling silk, when the humidity rises to the point where the pulling wire super-contracts, the pulling force generated by the spider silk will overcome the miniature spring. The pulling force makes the moving reflective surface close to the fiber probe, the Fabry-Perot cavity length decreases, and the free spectral range of the interference spectrum increases, which is shown as the increase in the peak spacing of the interference spectral lines; when the humidity decreases, the spider silk produces When the pulling force is reduced to the point where it cannot overcome the pulling force of the miniature spring, the reflective surface is moved away from the fiber probe, the length of the interference cavity increases, and the free spectral range of the interference spectrum decreases.

The spider pulling silk 5 has super-shrinking characteristics, it starts to shrink when the humidity is greater than 70%, and can produce a maximum shrinkage of 50% of the axial length, which drives the length of the Fabry-Perot cavity to change significantly; the generated tension can overcome the micro-spring 7 and pull the moving reflecting surface 6 to move closer to the fiber probe 4, the length of the Fabry-Perot cavity is shortened, resulting in an increase in the free spectral range of the interference spectrum; when the humidity decreases, the spider pulling silk 5 is super-shrinked and the pulling force is reduced. It is too small to overcome the pulling force of the miniature spring 7, so the moving reflecting surface 6 moves away from the fiber probe 4 under the pulling force of the miniature spring 7, the length of the Fabry-Perot cavity increases, and the free spectral range of the interference spectrum decreases, which can be passed through the optical fiber. The detector 10 realizes humidity detection.

Embodiments of the present invention are provided below in conjunction with specific numerical values:

(1) In order to cover the free spectral range of the interference spectrum as long as possible, and at the same time conform to the common communication light source band, select a broad-spectrum light source of 1525nm ~ 1610nm;

(2) According to the signal light, the optical fiber circulator with the center wavelength of 1550nm, and the common single-mode optical fiber for 1550nm communication are used as the optical fiber probe, the incident optical waveguide and the outgoing optical waveguide;

(3) Take a glass slide rail, take the ceramic core of the optical fiber connector as the optical fiber fixing piece, and fix the optical fiber fixing piece horizontally on one side of the slide rail with UV curing glue;

(4) Take a section of single-mode optical fiber, process the flat fiber end face with an optical fiber cutter, insert the processed single-mode optical fiber into the optical fiber fixing piece, and fix the optical fiber and the fixing piece together with UV curing glue;

(5) Use the solid block made of PDMS as the spring fixture, and take a miniature spring, rotate one end of it and insert it into the spring fixture. ; Then fix the spring fastener on the other end of the slide rail with UV curing glue;

(6) Take a small piece of glass and coat it with a reflective film on its surface to enhance the light reflectivity, and fix the uncoated surface of the glass with the miniature spring with UV curing adhesive or hot melt adhesive;

(7) Use tweezers to extract a certain length of spider pulling silk from the spinneret of the new spider, use UV curing glue to connect one end of the pulling wire to the optical fiber fixture, and use UV curing glue to connect the other end of the pulling wire to the moving reflective surface fixed;

(8) Use an optical fiber welding machine to splicing the incident optical waveguide with the fiber at the ① port of the fiber circulator, splicing the single-mode fiber used as the fiber probe with the fiber at the ② port of the fiber circulator, and splicing the outgoing optical waveguide with the fiber circulator. The ③ port optical fiber is spliced;

(9) Connect the incident light source to the incident light waveguide, and the outgoing light waveguide to the photodetector; during operation, the output light from the light source reaches the fiber probe to generate a beam of reflected light on the end face of the probe, and the outgoing light from the probe reaches the reflection surface to generate a second beam of reflected light. A beam of reflected light, the two beams of reflected light have an optical path difference related to the distance between the two reflecting surfaces, and the double-beam interference spectrum can be seen in the photodetector; when the relative humidity exceeds 70% RH, the spider silk is super-contracted, and the two reflections The interplanar spacing decreases with the increase of humidity so that the free spectral range of the interference spectrum increases; when the humidity decreases, the pulling force of the spider silk is not enough to offset the pulling force of the miniature spring, and the length of the interference cavity increases under the pulling force of the miniature spring, so that the interference The free spectral range of the spectrum is reduced, thereby enabling humidity sensing in the high humidity range.

In summary, the present invention relates to the technical field of optical fiber biosensing, and in particular to a Fabry-Perot high humidity sensor based on the super-contraction characteristics of spider pulling silk and a measurement method thereof. Including incident light source, incident optical waveguide, optical fiber circulator, optical fiber fixture, fiber probe, spider pulling wire, moving reflective surface, slide rail, miniature spring, spring fixture, outgoing optical waveguide and photodetector; The input port of the fiber optic circulator is connected by the incident light waveguide, and the fiber probe is led out from the output port of the fiber optic circulator and fixed on the slide rail by the fiber fixing piece. , the other side of the moving reflecting surface is connected with the spring fixing member fixed on the slide rail through the micro spring. The invention provides a Fabry-Perot humidity sensor based on the super-shrinkage characteristics of spider silk and a measurement method thereof. The super-shrinkage characteristics of spider pulling silk after absorbing moisture are utilized to build a Fabry-Perot humidity sensor with variable cavity length. The cavity is adopted, so that the interference spectrum of the reflected light from the end face of the fiber probe and the reflected light from the moving reflecting surface has different free spectral long ranges under different humidity. Using the super-shrinkage characteristics of spider pulling silk for humidity measurement, the humidity sensor has the characteristics of good natural degradability, biocompatibility, high sensitivity and high response speed under high humidity conditions.

Claims (5)

1. A Fabry-Perot high humidity sensor, characterized by: comprises an incident light source (1), an incident light waveguide (2), an optical fiber circulator (3), an optical fiber probe (4), an optical fiber fixing piece (4-1), a spider traction wire (5), a movable reflection surface (6), a slide rail (6-1), a micro spring (7), a spring fixing piece (8), an emergent light waveguide (9) and an optical detector (10), an incident light source (1) is connected with a port of an optical fiber circulator (3) through an incident optical waveguide (2), an optical fiber probe (4) is led out from the port of the optical fiber circulator (3) and is fixed on a slide rail (6-1) through an optical fiber fixing piece (4-1), a spider pull wire (5) is arranged between the optical fiber fixing piece (4-1) and one side of a movable reflecting surface (6), and the other side of the movable reflecting surface (6) is connected with a spring fixing piece (8) fixed on the slide rail (6-1) through a miniature spring (7); the optical detector (10) is connected with the port III of the optical fiber circulator through an emergent light waveguide (9).

2. A fabry-perot high humidity sensor according to claim 1, characterized in that: the end face of the optical fiber probe (4) and the movable reflecting face (6) form a Fabry-Perot interference cavity, one part of emergent light is reflected on the end face of the optical fiber probe (4), the other part of emergent light is emitted by the optical fiber probe (4), then reflected on the movable reflecting face (5) and reflected back to the optical fiber probe (4), two beams of reflected light are interfered, and the optical detector (10) monitors and obtains an interference spectrum.

3. A fabry-perot high humidity sensor according to claim 1 or 2, characterized in that: the spider dragline wire (5) has the super-shrinkage characteristic, starts to shrink when the humidity is higher than 70%, overcomes the pulling force of the micro spring (7) and pulls the movable reflection surface (6) to move close to the optical fiber probe (4); when the humidity is reduced, the super shrinkage of the spider traction wire (5) is weakened, the tension is reduced, the tension of the micro spring (7) cannot be overcome, and the movable reflection surface (6) moves away from the optical fiber probe (4) under the action of the tension of the micro spring (7); and the spider dragline wire can shrink 50% of the axial length of the spider dragline wire at most under the high humidity condition, so that the length of the Fabry-Perot cavity is driven to change remarkably.

4. Method for measuring a fabry-perot high humidity sensor according to claim 1 or 2, characterized in that: the method comprises the following steps that a Fabry-Perot high-humidity sensor is placed in a humidity testing environment, the length of a Fabry-Perot cavity is driven by the super-shrinkage of a spider traction wire to change along with humidity, and the length of the Fabry-Perot cavity is in a negative correlation relation with the free spectral range of a double-beam interference spectrum measured by a spectrometer; and measuring the change of the humidity of the environment by detecting the change of the free spectral range of the interference spectrum.

5. A method of measuring a fabry-perot high humidity sensor according to claim 3, characterized in that: the method comprises the following steps that a Fabry-Perot high-humidity sensor is placed in a humidity testing environment, the length of a Fabry-Perot cavity is driven by the super-shrinkage of a spider traction wire to change along with humidity, and the length of the Fabry-Perot cavity is in a negative correlation relation with the free spectral range of a double-beam interference spectrum measured by a spectrometer; and measuring the change of the humidity of the environment by detecting the change of the free spectral range of the interference spectrum.

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