CN204086135U - A kind of volatile organic matter Fibre Optical Sensor of interfering based on fiber end face F-P - Google Patents

Abstract

The utility model is bright discloses a kind of volatile organic matter Fibre Optical Sensor of interfering based on fiber end face F-P, one section of hollow-core fiber is connected at single-mode fiber end, the end of hollow-core fiber is closed with certain polymeric material, between polymeric material and single-mode fiber end face, form F-P interference cavity, form volatile organic matter sensing head thus; Light beam enters the F-P interference cavity in the middle of hollow-core fiber by single-mode fiber, and when fibre-optical probe contact volatile organic matter, the thickness of polymeric material will change, thus change the length of interference cavity; The frequency spectrum of interference light is subject to the modulation of interference cavity length, by spectrometer, interference light is analyzed to the measurement that just can realize volatile organic matter.The utility model comprises wideband light source, three-dB coupler, sensor fibre, sensing probe and spectrometer.This sensor construction is simple, and compact, signal to noise ratio (S/N ratio) is high, can realize monitoring the real-time continuous of escaping gas in the system such as production run, disaster monitoring.

Description

A Fiber Optic Sensor for Volatile Organic Compounds Based on F-P Interference of Fiber End Face

technical field

The utility model belongs to the field of optical fiber sensing, in particular to a volatile organic compound optical fiber sensor based on the F-P interference of the optical fiber end face. The sensor has simple structure, small size and high signal-to-noise ratio, and can realize real-time continuous monitoring of volatile organic compounds in production process, disaster monitoring and other systems. the

Background technique

Volatile organic compounds (volatile organic compounds, VOCs) are the most common type of air pollutants, usually referring to organic compounds with a boiling point of 50-250 °C that can form steam at normal temperature and pressure, mainly including benzene series, organic chlorides , Freon series, organic ketones, alcohols, amines, ethers and lipids, etc. VOCs are toxic, irritating and carcinogenic, and will seriously damage the environment and human health. Therefore, it is necessary to develop a method for sensitive, rapid and accurate determination of VOCs content in air. the

Among the existing detection methods, due to the unique advantages of optical fiber, such as small size, low loss, suitable for remote detection, etc., the detection of volatile organic compounds based on optical fiber has attracted more and more attention. There are many kinds of volatile organic compound detection methods based on optical fiber, and the most common method is based on spectral analysis, which detects and analyzes the characteristic absorption lines of the gas to be measured to obtain the concentration of the gas to be measured. This detection method has high sensitivity and fast response, but often requires a special light source to match the absorption spectrum range of different types of gases to be measured, so the high cost limits its application range. The detection of volatile organic compounds based on fiber Bragg grating has also been reported. The gas to be measured acts on the outside of the fiber Bragg grating and causes the shift of the resonance wavelength by affecting the effective refractive index of the fiber core and cladding of the fiber Bragg grating. However, the writing of the grating will cause damage to the optical fiber, making it difficult to use for a long time. the

Aiming at the above problems, we propose a fiber optic sensor for volatile organic compounds based on F-P interference at the fiber end face. This kind of sensor has a compact structure, can be repeated for a long time, is convenient for trace monitoring, has high sensitivity, and has the characteristics of optical fiber anti-temperature interference, which can well realize the detection of different types of volatile organic compounds. the

Utility model content

The purpose of the utility model is to provide a gas pressure optical fiber sensor based on the F-P interference of the optical fiber end face which is more flexible, simple, high in accuracy and good in reliability. the

The technical solution of the utility model is as follows:

A fiber optic sensor for volatile organic compounds based on F-P interference at the end face of an optical fiber, comprising a broadband light source (1), a 3dB coupler (2), a transmission fiber (3), a sensing probe (4) and a spectrometer (5); the above-mentioned 3dB coupling The filter contains four ports, the broadband light source (1) and the input of the spectrometer (5) are respectively connected to two ports on one side of the 3dB coupler, one end of the transmission fiber (3) is connected to a port on the other side of the 3dB coupler, and the transmission The other end of the optical fiber (3) is connected with the sensing probe (4);

The above-mentioned sensing probe (4) is characterized in that a section of hollow-core optical fiber and a single-mode optical fiber are fused to form an F-P interference cavity, the length of the hollow-core optical fiber is between 1-3cm, and the outer end surface of the hollow-core optical fiber is closed by a polymer material; Said polymer material has the effect of volume expansion after absorbing volatile matter. the

The beneficial effects of the utility model are:

A volatile organic compound optical fiber sensor based on F-P interference at the end face of the optical fiber. One end of the single-mode sensing optical fiber cable is connected to an optical fiber volatile organic compound sensing probe, and the other end is connected to a broadband light source and a spectrometer through a 3dB coupler. the

After the broadband light source emits a beam, it is coupled into the sensing fiber through a 3dB coupler, and the beam enters the sensing probe through the sensing fiber. The light beam enters the F-P interference cavity in the hollow core fiber from the single-mode fiber, and the two reflection surfaces of the interference cavity are composed of polymer material and the end face of the single-mode fiber. The interference light formed in the interference cavity is transmitted back through the single-mode fiber, and coupled into the spectrometer through the 3dB coupler. the

When volatile organic compounds come into contact with the polymer material, the polymer material will expand, thereby changing the cavity length of the F-P interference cavity. Since the spectrum of the interference light is modulated by the length of the interference cavity, the measurement of volatile organic compounds can be realized by analyzing the interference light with a spectrometer. the

By analyzing the interference light wave with a spectrometer, the change of the content of volatile organic compounds can be obtained. The invention is flexible and simple, has high precision and good reliability, and is suitable for various occasions requiring real-time monitoring and measurement of volatile organic compounds. the

Description of drawings

Fig. 1 is a schematic structural diagram of a VOC optical fiber sensor based on F-P interference at the end face of the optical fiber. the

Fig. 2 is a schematic structural diagram of a sensing probe of a VOC optical fiber sensor based on F-P interference at the end face of the optical fiber. the

In the figure: single mode fiber 1 hollow core fiber 2 polymer material 3

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing and specific embodiment:

As shown in Figure 1, a fiber optic sensor for volatile organic compounds based on F-P interference at the fiber end face, including a broadband light source (1), a 3dB coupler (2), a transmission fiber (3), a sensing probe (4) and a spectrometer (5) ; Above-mentioned 3dB coupler comprises four ports, broadband light source (1) and spectrometer (5) input are respectively connected with two ports on one side of 3dB coupler, and one end of transmission fiber (3) is connected with the other side of 3dB coupler One port is connected, and the other end of the transmission fiber (3) is connected with the sensing probe (4). the

As shown in Figure 2, the above-mentioned sensing probe (4) is characterized in that a section of hollow-core optical fiber and a single-mode optical fiber are fused together to form an F-P interference cavity, the length of the hollow-core optical fiber is between 1-3cm, and the outer end surface of the hollow-core optical fiber Closed by a polymer material; said polymer material has the effect of volume expansion after absorbing volatile matter. the

The utility model is based on the following principles:

The broadband light source emits a light beam with energy I ₀ , which is coupled into the sensing fiber by a 3dB coupler, and then transmitted into the FP interference cavity composed of a hollow fiber by the sensing fiber. The interfering beam enters the spectrometer via a single-mode fiber through a 3dB coupler. The interference light received by the spectrometer can be expressed as:

in is the phase angle, λ is the wavelength of light, n _eff is the effective refractive index, and ΔL is the length variation of the interference cavity. The length L of the cavity can be solved by phase demodulation. at the center wavelength for Perform Taylor expansion:

when have

$\mathrm{<span\; class="notranslate">\; \&Delta;\&lambda;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; eff</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Thus, the relationship between the length change ΔL of the interference cavity and the interference wavelength change Δλ is obtained. the

By measuring the change Δλ of the interference wavelength with a spectrometer, the length change ΔL of the F-P interference cavity inside the hollow-core fiber caused by the change of the content of volatile organic compounds can be obtained. the

The way this implementation works is:

The light emitted by the broadband light source is incident into the 3dB coupler, and the light passes through the coupler and reaches the sensing probe through the transmission fiber; due to the absorption of volatile organic compounds from the outside, the polymer material at the end of the sensing probe expands, causing the sensor probe to The F-P cavity length changes; the interference light wavelength in the F-P cavity is modulated by the cavity length; the interference light wave enters the spectrometer from the transmission fiber through the 3dB coupler; the interference wavelength shift caused by volatile organic compounds can be observed by the spectrometer; thus The sensor can realize the sensing of volatile organic compounds. the

The shut-in technology that can realize the sensing of volatile organic compounds in this device is:

1. The end face of the sensing probe is coated with a polymer material. When the polymer material contacts with volatile organic compounds, the polymer material will expand and its length in the hollow-core optical fiber will increase. As the concentration of volatile organic compounds increases, the volume of the polymer will also increase continuously. the

2. In the hollow-core fiber, there are polymer materials and single-mode fiber end faces to form an F-P interference cavity. As the length of the polymer material changes, the length of the F-P interference cavity in the hollow-core fiber will change. Since the spectrum of the interference light is modulated by the length of the interference cavity, the measurement of volatile organic compounds can be realized by analyzing the interference light with a spectrometer. the

Claims (1)

1., based on the volatile organic matter Fibre Optical Sensor that fiber end face F-P interferes, comprise wideband light source (1), three-dB coupler (2), Transmission Fibers (3), sensing probe (4) and spectrometer (5); Above-mentioned three-dB coupler comprises four ports, wideband light source (1) and spectrometer (5) input and are connected with two ports of three-dB coupler side respectively, the port in one end of Transmission Fibers (3) and the opposite side of three-dB coupler is connected, and the other end of Transmission Fibers (3) is connected with sensing probe (4);

Above-mentioned sensing probe (4), it is characterized in that forming F-P interference cavity by one section of hollow-core fiber and the welding of single-mode fiber phase, hollow-core fiber length is between 1-3cm, and the outer face of hollow-core fiber is closed by polymeric material; Described polymeric material has the effect absorbing volumetric expansion after volatile matter.