A D-shaped open-ring microgroove photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR) is proposed for the simultaneous measurement of methane gas concentration and temperature. The sensitive coatings are polysiloxane-doped cryptane E and polydimethylsiloxane (PDMS), and the designed microgroove structure with out-of-hole coating is expected to improve the sensitivity. The finite element method (FEM) is employed to analyze the data numerically, and the results demonstrated that the average sensitivities could reach − 96.57 nm/% for methane concentration in the range of 0.5 ~ 3.0% and − 6.86 nm/°C for methane temperature in the range of 0 ~ 50℃. Both measurement channels exhibited excellent linearity, making them highly valuable for environmental monitoring and other applications.
Research Article
A high sensitivity D-shaped microgroove photonic crystal fiber gas sensor based on surface plasmon resonance
https://doi.org/10.21203/rs.3.rs-4964624/v1
This work is licensed under a CC BY 4.0 License
Journal Publication
published 12 Oct, 2024
You are reading this latest preprint version
SPR
Temperature detection
Gas sensing
D-shape PCF
Methane is a kind of colorless and odorless clean energy, which is widely present in natural gas, biogas and other energy sources used by human beings, when the concentration of methane gas in a confined area reaches more than 5%, it is very easy to produce an explosion under the action of a certain temperature, to realize the advanced warning and prevent the danger, it is necessary to use sensors to detect its concentration and temperature in real-time [1, 2]. With the development of science and technology, on the one hand, fiber optic sensing technology is proposed. Among these, compared with other types of optical fibers, PCF has the advantages of flexible structure, can maintain single-mode transmission in a wide range of wavelengths, strong nonlinear characteristics, and anti-electromagnetic interference [3]. On the other hand, there are numerous sensing techniques based on optical fiber, such as Fiber Fabry-Perot Cavity which uses the principle of photothermal spectroscopy to sense gases, where a laser beam is focused into a gas sample and absorbed and converted into heat resulting in an increase in the temperature of the gas, which causes a change in the refractive index, from which the concentration of the gas is measured [4]. PBG based laser emission sensing technology generates a laser beam through the repeated oscillation and amplification of photons produced during stimulated radiation in the optical fiber resonator. Due to the presence of a photonic bandgap, light waves satisfying a specific wavelength can be stably propagated and amplified, thus achieving wavelength selectivity of laser emission [5]. LMR is also a commonly used sensing principle by researchers. In optical fibers, when light propagates, a portion of the energy is absorbed or scattered to form loss modes, and the characteristics of these loss modes are related to the physical and chemical properties of the medium surrounding the fiber. By measuring the characteristics of the loss modes, information about the medium can be obtained [6, 7]. SPR is a fiber optic sensing technique that has been widely used in recent years. When light is incident on a metal film at a certain angle, it excites the free electrons in the metal to form collective oscillations, i.e., surface plasmon waves (SPW). When the fading wave matches the frequency and wavelength of the SPW, resonance occurs, resulting in a significant reduction in the intensity of the reflected light. By detecting the change in reflected light intensity, the analyte under test is analyzed as it interacts with the metal surface. It has the advantages of high sensitivity, nanoscale optical manipulation, no labeling requirement, and real-time monitoring [8]. PCF-SPR sensors have received extensive attention from researchers in recent years, and they have potential research value in many fields such as biomedicine, environmental monitoring, and food safety [9, 10, 11].
In recent years, some researchers have investigated fiber-optic gas sensors and achieved considerable results. Liu et al [12] designed a photonic quasi-crystalline fiber optic sensor using a double-sided polished hexagonal quasi-crystalline fiber and coated with metallic Ag to excite the SPP modes, and a cryptophane-E doped polysiloxane nanofilm was used as a sensitive coating for methane gas molecules, the maximum sensitivity was obtained to be 8 nm/% in the range of methane concentration from 0 to 3.5%. Liu et al [13] proposed a dual-core PCF sensor with a methane-sensitive film coated on oversized air holes on both sides of the optical fiber, and using rectangularly arranged air holes to form a dual core to enhance the sensitivity of the sensor, which has a simple structure and can achieve methane concentration measurements from 0 to 3% with an average sensitivity of 4.60 nm/%. Wang et al [14] proposed a PCF Mach Zende interference reflective sensor based on a biconvex conical structure, using an Ag film at the reflective end, and measuring the methane concentration with a sensing probe covered with cryptophane molecule A sensitive film and cryptophane molecule E, respectively, the experimental results showed that both had a measurement range of 0 ~ 5%, with a sensitivity of 1.069 nm/% and 1.272 nm/%, respectively. Since the sensitive coating used in this sensor has high selectivity for methane, it is not affected by other gases. Aryan et al [15] designed a new triangular PCF for gas detection with a sensitivity of 75.14% for methane gas concentration at 1.33 µm wavelength, in addition to the high birefringence and effective area of this sensor, which is capable of multiple gas single detection, but its fabrication process is complicated and the sensitivity to structural parameters is high. Li et al [1] investigated the SPR-based HC-ARF sensor, and the reasonable selection of metal Au and methane gas sensitive film enables it to accurately measure the methane concentration by tracking the movement of loss peaks, and its detection range can be up to 0 ~ 3.5% with a sensitivity of 5.54 nm/%, and this sensor also provides a new fiber optic sensing solution for the advance warning of methane gas leakage. Li et al [16] used a PCF with a D-shaped structure to increase the contact area with methane molecules, excited the SPR effect by coating metal Au on the polishing groove of the fiber, and captured methane gas molecules using a UVCFS film to change the refractive index of the membrane. The results show that the sensor can realize the measurement of methane concentration in the range of 0 ~ 3.5%, and its sensitivity is as high as 9.88 nm/% with good linearity. Liu [17] et al. studied a hydrogen-methane gas sensor based on four-wave mixing and SPR technology, using a D-shaped structure of PCF, by adjusting the structural parameters to achieve the simultaneous measurement of hydrogen and methane, the detection range of 0 ~ 3.0%, the sensitivity of 4.03 nm/% and − 14.19 nm/%, respectively, and there is no interference between the two gases, which can achieve the dual-physical quantity measurement. Zhang [18] et al. proposed a fiber-optic ring mirror sensor based on PCF and interference, which detects the concentration and temperature of hydrogen by coating Pd/WO3 on PCF, and then decouples the measured object using the dual-wavelength matrix method, whose sensitivities are − 1.12 nm/% and − 1.84 nm/°C, respectively. Although this sensor can realize dual-physics measurement, its sensitivity and detection range are not satisfactory. Xiao et al [19] designed a PCF with an anchor structure based on SPR, using its porous structure to enhance the interaction with the gas. A gas-sensitive film containing Cryptophane-A molecules was coated on the surface of metallic Au to achieve the measurement of methane concentration. The air holes were filled with an ethanol liquid as a temperature-sensitive material to achieve temperature measurement. The sensitivity of methane concentration in the range of 0.5-3% was analyzed by FEM to be -4.84 nm/%, and the sensitivity of temperature in the range of 10–30°C was 0.58 nm/°C. Although this sensor can realize the simultaneous measurement of methane concentration and temperature, its structure is complicated, especially the method of filling the holes with temperature-sensitive materials makes the manufacturing process difficult, and it is difficult to apply in real scenarios.
This paper proposes and designs an SPR-based photonic crystal fiber optic sensor for the concentration and temperature sensing of methane gas. The sensor employs a D-shaped microgroove configuration with an Ag metal coating on the outer surface of the optical fiber and within the microgroove apertures. The sensor exhibits sensitivity to methane molecules and temperature, respectively, by utilizing polysiloxane-doped cryptane E and PDMS. It not only achieves high sensitivity and sensing performance through a distinctive structural design but also greatly simplifies the fabrication process. The comprehensive results show that the sensor can be effectively used in a variety of fields, including industrial production, environmental monitoring, and gas explosion, to facilitate real-time detection and warning of methane gas concentration and temperature.
Figure 1 illustrates the proposed cross-sectional view of the sensor. The PCF is composed of two layers of hexagonally arranged air holes. To enhance the coupling between the fiber core and the SPP modes, as well as to improve the sensitivity, an aperture with a diameter slightly larger than the other apertures in the layer is placed at the top of the air holes in the inner layer. Additionally, an aperture with a diameter slightly smaller than the other air holes in the layer is placed at the bottom of the air holes in the outer layer. Furthermore, a D-shaped structure was created by polishing the entire fiber and forming an open ring structure with an air hole at the top of the outermost layer. The three air hole diameters are denoted by d1, d2, and d3, respectively. The selection of the appropriate metal film is a critical determinant of the excitation of SPP modes. Commonly used metals include gold, silver, and copper. Although gold is chemically stable, it is an expensive material, exhibits high optical loss, and the resonance peaks are not sufficiently sharp. While copper is a cost-effective material with excellent electrical conductivity, it is prone to oxidation and corrosion, and its SPR performance is not as optimal as that of gold and silver. Silver, on the other hand, exhibits excellent SPR performance, sharper resonance peaks, and lower losses. However, it is susceptible to corrosion, which can be mitigated through the application of a protective coating over a sensitive layer [20]. Accordingly, silver is selected as the excitation material for the two SPP channels in this sensor, and its thicknesses are designated as t1 and t2, respectively. In order to achieve the measurement of methane gas concentration and temperature, the sensitive films polysiloxane-doped cryptane E and PDMS were coated on the surface of the metal film of the two measurement channels, the thicknesses of which are denoted by t3 and t4, respectively. The outer portion of the optical fiber was filled with methane gas to simulate a methane environment, and the outermost layer was set with a perfect match layer to absorb radiant energy and reduce boundary effects.
The proposed sensors can be fabricated by the stacked drawing method or beam stacking method [21]. Capillary tubes of varying diameters are stacked according to the designed air-hole structure arrangement to form a prefabricated rod. This rod is then positioned within the jacketed tube and subjected to a tensile force in a high-temperature environment through a drawing tower. Throughout this process, the temperature and speed of drawing are strictly regulated to guarantee the structural integrity of the optical fiber. The D-shaped structure is formed by repeated polishing using the side polishing technique, and then the optical fiber is cleaned to ensure a smooth surface, which facilitates the attachment of the metal film and improves the excitation of SPP modes. Subsequently, the metal film is uniformly coated onto the PCF through the application of chemical vapor deposition (CVD) or magnetron sputtering techniques [22, 23]. It is essential to conduct the coating process in a high vacuum or a clean environment to minimize the impact of impurities and contamination on the quality of the metal film. The temperature-sensitive materials are composed of liquid silicone oil and a curing agent in a specific ratio, which is cured by heating at 60°C for two hours, and then they are uniformly coated on the surface of the metal film using dip coating or spraying techniques[24]. Gas-sensitive materials are made by curing a mixed solution of polysiloxane and cryptane E organic molecules, which are also coated on the surface of the metal film by the above-mentioned techniques [25]. Thus, these existing techniques make the proposed PCF sensor feasible.
Figure 2 depicts the schematic diagram of the experimental setup of the proposed sensor. The sensor is placed in a closed gas chamber where a gas mixture of methane and nitrogen is introduced to simulate a methane environment. Additionally, a thermoregulation device is employed to simulate the ambient temperature. A broadband light source (BBS) emits an optical signal within the wavelength range of 2000–3000 nm. This signal is initially conditioned and controlled by a coupler to obtain a polarized optical signal. Subsequently, the signal is conveyed through a single-mode fiber (SMF) and a variable optical attenuator (VOA) for meticulous intensity conditioning, and ultimately transmitted to the designed sensor. After that, the optical signal is transmitted from the sensor to the Spectrum Analyzer (OSA) via a single-mode fiber. The spectrum analyzer is employed to display and record spectral information. This device layout ensures precise conditioning and transmission of the optical signal and helps to achieve highly sensitive measurements of methane concentration and temperature.
The PCF proposed uses silica as the base material and its refractive index versus wavelength can be determined by the Sellmeier equation:
$${n^2}(\lambda )=1+\frac{{{A_1}{\lambda ^2}}}{{{\lambda ^2} - {B_1}^{2}}}+\frac{{{A_2}{\lambda ^2}}}{{{\lambda ^2} - {B_2}^{2}}}+\frac{{{A_3}{\lambda ^2}}}{{{\lambda ^2} - {B_3}^{2}}}$$
1
Where A1 = 0.6961663, A2 = 0.4079426, A3 = 0.8974794, B1 = 0.0684043 µm2, B2 = 0.1162414 µm2, B3 = 9.896161 µm2 and λ stands for the wavelength of the incident light in micrometers [26].
The Drude model was used to describe the motion of the electrons inside the metal and the complex permittivity of silver was calculated to be:
$${\varepsilon _{Ag}}(\omega )={\varepsilon _\infty } - \frac{{{\omega _p}^{2}}}{{\omega (\omega - i{\omega _\tau })}}$$
2
Where ε∞ = 2.48, ωp = 1.35×1016 rad/s, and ωτ = 7.62×1013 rad/s [27].
Polysiloxane doped cryptane E is used as a methane gas sensitive film due to its rapid interaction with methane molecules and its high selectivity as well as good chemical inertness, and its refractive index variation with methane gas concentration (C_CH4) can be obtained from the following equation [16]:
$$n=1.448 - 0.0046{C_ - }C{H_4}$$
3
PDMS is used for temperature sensing because of its good thermal conductivity and flexibility, and it can be used for a long time in the range of -50 to 200°C. Since its thermo-optic coefficient is much larger than that of silicon dioxide, the refractive index of silicon dioxide is negligibly affected by temperature. The variation of its refractive index with temperature (T) can be obtained from the following equations [28, 29]:
$${n_{PDMS}}= - 4.5 \times {10^{ - 4}} \cdot T+1.4176$$
4
In this paper, the confinement loss is employed to analyze the performance of the sensor, which is intimately associated with the imaginary component of the refractive index of the fiber core. Its calculation can be obtained from the following equation [30]:
$$\alpha =8.686 \times \frac{{2\pi }}{\lambda }\operatorname{Im} ({n_{eff}}) \times {10^4}(dB/cm)$$
5
where Im denotes the real part of the effective refractive index of the fiber core and λ denotes the wavelength of the incident light in microns.
Figure 3 illustrates the dispersion relation between the y-polarized fundamental mode and the SPP mode, as well as its loss profile for wavelengths in the range of 2.0–3.0 micrometers. The black line represents the real part of the effective refractive index of the fiber core, the green and red lines represent the real part of the effective refractive index of the gas (channel Ⅰ) and temperature (channel Ⅱ) SPP modes, respectively, while the blue line represents the loss. According to the mode coupling theory, when the effective refractive indices of the fiber core and SPP modes are not equal, the energy is confined to their respective regions. It is only when the effective refractive indices of the fiber core and the SPP modes are equal, that the SPR is excited. This can be demonstrated by the inset in Fig. 3. At this point, a significant amount of energy in the fiber core will be transferred to the SPP mode, resulting in the appearance of a peak in the corresponding loss spectrum, which is referred to as the resonance peak, the wavelength is the resonance wavelength. When the methane gas concentration or temperature changes, the position of the resonance wavelength will also change, thus realizing the measurement of concentration and temperature. This characteristic enables the sensor to sensitively detect changes in environmental parameters.
The loss spectra of the sensor at different methane gas concentrations and temperatures are illustrated in Figs. 4(a) and 4(b). From the figures, it can be observed that the resonance wavelengths undergo a blueshift when either the methane gas concentration or temperature increases. This phenomenon can be attributed to a reduction in the refractive index of the sensitive film, which results in a decline in the effective refractive index of the SPP mode and a comparatively minor impact on the refractive index of the core mode. Consequently, the phase matching point is shifted towards shorter wavelengths. Furthermore, it can be observed that the resonance peak of the other measurement channel remains unaltered when the methane gas concentration or temperature is modified. This demonstrates that the sensor is capable of accurately reflecting the independence and responsiveness of the two channels when detecting changes in methane concentration and temperature simultaneously. This also indicates that the sensor exhibits excellent measurement performance and anti-interference capability. The resonance wavelength sensitivity is a crucial parameter for assessing the sensing performance of the sensor. It can be determined through the wavelength interrogation method.
For methane concentrations, the sensitivity is given by the following equation:
$${S_\lambda }(nm/\% )=\frac{{\Delta {\lambda _{C{H_4}}}}}{{\Delta {C_ - }C{H_4}}}$$
6
where \(\Delta {\lambda _{C{H_4}}}\)denotes the amount of change in resonance wavelength due to methane concentration and \(\Delta {C_ - }C{H_4}\) denotes the amount of change in methane concentration [31].
For temperature, the sensitivity is given by the following equation:
where \(\Delta {\lambda _T}\) denotes the amount of resonance wavelength change due to temperature and \(\Delta T\) denotes the amount of temperature change [31].
As illustrated in Figs. 5(a) and (b), the sensitivity fitting curves for methane concentration and temperature, respectively. This demonstrates that the correlation coefficients of the fits for methane concentration in the range of 0.5-3.0% and for temperature in the range of 0–50°C are high, indicating good linearity. Furthermore, the slopes, which indicate the sensitivities, are − 96.57 nm/% and − 6.86 nm/°C, respectively.
The structural parameters of the sensor have an impact on the detection performance of methane gas concentration and temperature. To optimize the sensing characteristics of the sensor, this paper discusses the main structural parameters of the sensor, including the diameters of the air holes d1, d2, and d3, the lattice spacing P, the thicknesses of the metal coated by the two measurement channels t1 and t2, and the thicknesses of the sensitive film t3 and t4.
Figure 6 illustrates the impact of varying the diameter of the air holes (d1) on the loss peaks and resonance wavelengths of the two channels. When d1 is varied from 1.1 to 1.3 µm, the resonance wavelengths of both channels undergo a red shift. Additionally, the loss peaks initially increase and then decrease. However, the effect on channel Ⅰ is more significant than that on channel Ⅱ. This is because an increase in the diameter of the air hole reduces the refractive index of the fiber core, which alters the phase-matching conditions. This results in the core mode and the SPP mode needing to reach a phase match at longer wavelengths. Furthermore, the enhancement of the swift wave and the SPW interaction causes more energy transfer from the fiber core to the SPP mode. Nevertheless, as the diameter of the d1 continues to increase, a greater proportion of light is leaked from the fiber core and distributed around the air hole, rather than near the metal layer. This results in a weakening of the strength of the SPR and a reduction in the loss peak. The diameter of d1 was optimized to 1.2 µm in consideration of the requisite sensitivity and detection accuracy.
Figure 7 illustrates the impact of varying the air pore diameter (d2) on the system. For channel Ⅱ, as d2 is varied from 1.4 to 1.6 µm, the resonance wavelength undergoes a redshift, accompanied by an initial increase and subsequent decrease in the loss peak. This phenomenon can be attributed to the same underlying mechanism as observed in the variation of d1. For channel Ⅰ, the resonance wavelength is blue-shifted, and the loss peak decreases. This is since the air holes are primarily aligned in proximity to the channel Ⅰ. An increase in d2 impedes the penetration of the swift wave, resulting in a reduction in fiber core energy transferred to the SPP mode. Consequently, the resonance strength is diminished. Here, the optimal diameter for d2 is determined to be 1.5 µm.
The diameter of the outermost air hole of the PCF, designated as d3, exerts a profound influence on the sensor performance. As illustrated in Fig. 8, the resonance wavelengths of both channels exhibit a blueshift when the diameter is varied from 1.7 to 1.9 µm. Additionally, the resonance peak is observed to disappear at d3 = 1.9 µm for channel Ⅰ. This is because d3 is located in the outermost layer, close to the metal layer. Consequently, its alteration has a smaller impact on the core mode's effective refractive index and a more significant effect on the SPP mode. This results in a shift in the phase-matching condition between the core mode and the SPP mode, enabling resonance at a shorter wavelength. Conversely, when d3 becomes excessively large, it diminishes the interaction between the SPP mode and the swift wave, leading to a reduction in the resonance peak. In consideration of these factors, the optimal value for d3 was determined to be 1.7 µm.
The gap between two adjacent air holes is also optimized, and Fig. 9 shows the loss characteristics of the proposed sensor P in the range of 2.9 variation to 3.1 µm. It can be seen that the P has no effect on the resonance wavelength of channel Ⅰ, and there is only a change in the loss peak, which indicates that the variation of P does not change the phase-matching condition of its core mode with the SPP mode. For channel Ⅱ, its resonance wavelength is red-shifted, and the loss first increases and then decreases, which is mainly because the P becomes larger to make the effective refractive index of the fiber larger, and the propagation constant of the SPW decreases, which makes the resonance wavelength move to the direction of longer wavelengths. For the loss value, the increase of lattice spacing makes more swift wave generated to interact with the SPP mode, but as the P continues to increase, the energy of optical leakage increases, and most of the energy has been scattered out before reaching the SPP mode. The comprehensive consideration selects P = 3.0 µm as its optimum value.
The thickness of the metal, as a necessary material for SPP excitation, also deeply affects the characteristics of the sensor. As shown in Fig. 10(a) and (b), the loss characteristics of the two channels with the thickness of the metal film, respectively. t1 mainly affects channel Ⅰ, and either too large or too small a thickness leads to the disappearance of the SPR phenomenon. The SPW generated by the too-thin metal film is not strong enough to excite and support the SPR. Too thick metal film increases the damping effect, resulting in increased energy dissipation, and most of the incident light is reflected or absorbed, which cannot reach the interface between the metal and the medium, resulting in insufficient SPW excitation. t2 mainly affects channel Ⅱ, whose SPR is the strongest at a thickness of 40 nm, and the loss peak decreases when t2 = 30 or 50 nm, for the same reason as the concentration channel. Considering the above reasons, t1 = 30nm and t2 = 40nm are chosen as the optimal values for the two channels, respectively.
v
Figure 10 (a) Variation of channel Ⅰ with Ag thickness loss characteristics (b) Variation of channel Ⅱ with Ag thickness loss characteristics
In order to achieve specific measurements of methane concentration and temperature, a sensitive film was used, the thickness of which is also discussed in this paper, as shown in Fig. 11(a) and (b). The t3 variation does not affect channel Ⅱ, which also indicates its insensitivity to temperature. It has less effect on channel Ⅰ, and its loss value increases and then decreases, but the change between the thicknesses of the adjacent films is not large, which indicates that when producing the sensors, their thicknesses are more tolerant and more achievable to produce, and t3 = 100nm is chosen as its optimum value. The t4 change has no effect on channel 1, while the temperature-induced loss peak first increases and then decreases with its thickness, and to produce a more pronounced resonance peak, we chose t4 = 1.0 µm as its optimum value.
After analyzing and optimizing the structure of the sensor, the main structural parameters of the sensor are finally determined as follows: d1 = 1.2 µm, d2 = 1.5 µm, d3 = 1.8 µm, t1 = 30 nm, t2 = 40 nm, t3 = 100 nm, t4 = 1.0 µm, and P = 3.0 µm. Under this structure, the proposed sensor demonstrates better sensing performance.
This paper compares and analyzes the sensing performance of the methane concentration temperature sensor proposed with that of existing sensors of the same type, as shown in Table 1. The initial two sensors employ the SPR sensing principle. Despite their concentration detection range being marginally broader than that of the sensor proposed in this paper, their sensitivity is inferior to that of the proposed sensor. The sensing principle employed by Ref. 16 is that of interference, which is less effective than the SPR type of sensor. Fiber optic sensors that are capable of measuring both methane concentration and temperature are scarce. While Ref. 22 can fulfill the requisite criteria, its average sensitivity is inferior to that of the proposed sensor. Consequently, the proposed sensor exhibits a notable advantage.
| Ref. | Sensing Method | Concentration Range (%) | WS(nm/%) | Temperature Range(℃) | WS(nm/℃) |
|---|---|---|---|---|---|
| [1] [12] | SPR SPR | 0 ~ 3.5 0 ~ 3.5 | 5.54 Ave. 8 Max. | \ \ | \ \ |
| [13] | Sagnac Interference | 0 ~ 3.0 | 4.6 Ave. | \ | \ |
| [16] [17] [19] Proposed | SPR SPR SPR SPR | 0 ~ 3.5 0 ~ 3.0 0.5 ~ 3.0 0.5 ~ 3.0 | 9.88 Ave. 14.19 Ave. 4.84 Ave. 96.57 Ave. | \ \ 10 ~ 30 0 ~ 50 | \ \ 0.58 6.86 |
In this study, we investigated a PCF optical methane concentration temperature sensor based on SPR. A silver film is coated on two channels to facilitate the excitation of the SPR effect. Polysiloxane-doped cryptane E and PDMS are used for methane gas concentration and temperature sensing, respectively. The sensing performance is enhanced by rational structure design and parameter optimization. The sensitivity is as high as 96.57 nm/% in the gas concentration range of 0.5 ~ 3.0% and 6.86 nm/°C in the temperature range of 0 ~ 50°C, and both exhibit good linearity, which facilitates the calibration of the sensor. Furthermore, the sensor is capable of measuring methane gas concentration and temperature without cross-interference, which is a distinct advantage over the majority of existing fiber optic gas sensors. Potential applications include methane leak monitoring, coal mine safety, and environmental monitoring.
Authors’ contributions. Xiaoyong Gan: participated in most of the work of the experiment, including literature review, experiment implementation, data collection, and in-depth analysis. In addition, he was responsible for and wrote the draft of the introduction. Hongzhi Xu: He created and maintained the experimental model, optimized the experimental data collection system, and participated in the analysis of the experimental data. He was responsible for the modeling and interpretation of the phenomena, provided important feedback during the writing process, and helped to revise and improve the paper. Shubo Jiang: The main sponsor and project leader of this research project. She was responsible for the overall project design, the development of the experimental program, and the writing of the final report. She was also responsible for the preliminary analysis and interpretation of the experimental data.
Funding Currently, there is no funding for the work.
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No competing interests reported.