Design and modeling of a photonic crystal fiber gas sensor
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Citations
High sensitivity evanescent-field gas sensor based on modified photonic crystal fiber for gas condensate and air pollution monitoring
Exposed-core microstructured optical fibers for real-time fluorescence sensing
Opening up optical fibres
Fast Response Microstructured Optical Fiber Methane Sensor With Multiple Side-Openings
Strain and Temperature Characteristics of a Long-Period Grating Written in a Photonic Crystal Fiber and Its Application as a Temperature-Insensitive Strain Sensor
References
The mathematics of diffusion
Diffusion: Mass Transfer in Fluid Systems
The Finite Element Method in Electromagnetics
Optical properties of high-delta air silica microstructure optical fibers.
Diffusion in Gases and Porous Media
Related Papers (5)
All-silica single-mode optical fiber with photonic crystal cladding
Frequently Asked Questions (18)
Q2. What is the effect of the wall on the PCF?
Because the size of the holes in the PCF is small, the wall effect between the molecules and the wall of the hole column may also need to be taken into account.
Q3. How much blow rate was used to blow the acetylene gas into the chamber?
Acetylene gas with a concentration approaching C0 100% was blown into the chamber along a direction orthogonal to the PCF with a blow rate of 100 cm3 s.
Q4. What is the knudsen number for the wall effect?
The Knudsen number Kn m d is usually used to represent the wall effect of a capillary diffusion system,11 where m is the mean free path of the gas molecules and d is the diameter of the capillary tube the hole diameter here .
Q5. What is the spatial coordinate of the acetylene distribution along the length of the air?
At time t the distribution of acetylene concentration along the length of the air hole columns may be written as9C x, t C0(1 4 j 1,3,5 1 j sin j x l exp j l 2Dt ), (4)where D is the binary diffusion coefficient between the air and acetylene and can be found in the reference book10 and x is the spatial coordinate along the longitudinal direction of the PCF.
Q6. What is the effect of the openings in the PCF?
The openings in the PCF modify the waveguide structure and thus change the transversal field distribution in the fiber cross section.
Q7. What is the cross-sectional area of the outlet valve?
The cross-sectional area of the outlet valve is 2 cm2 and is 4 times bigger than that of inlet in order to prevent additional pressure that may affect the diffusion process when the C2H2 was loaded into the chamber.
Q8. How long should the sensing fiber be?
For a gassensing application that requires a response time of 1 min the length of the sensing PCF should be limited to less than 7 cm.
Q9. How many ppm of acetylene can be detected?
Preliminary experiments and simulation show that an acetylene sensor system with a response time of 1 min and sensitivity of better than 6 ppm can be realized.
Q10. How long does it take for the CA to reach 90% C0?
If the authors take the time for CA t to reach 90% C0 as the response time of the fiber, the response times for 3-, 5-, and 7-cm lengths of fiber with both ends open for diffusion are found to be 11.7, 32.5, and 62.7 s, respectively.
Q11. What is the evanescent field of power in the air holes?
4 and 5 where most of the guided light power is confined within the solid-core region with a fraction evanescent field of power extended into the holey region.
Q12. How many ppm of acetylene is detected?
Consider that the detection resolution of 3.75 parts per million for an equivalent of 1 m ppm m of acetylene has been achieved with wavelength modulation spectroscopy and digital signal processing.
Q13. What is the diffusion coefficient of B acetylene in the continuum state?
The corrected binary diffusion coefficient DABC of B acetylene in A air may be shown as12DAB C DABDBB K DAB DABK , (7)where DAB is the diffusion coefficient of air and acetylene in the continuum state, DABK is the combined Knudsen diffusion coefficient and can be written as12DAB K DAAKXB DBBKXA, (8)where XA and XB are the molar fractions of species A and B and DAA K and DBB K are the Knudsen diffusion coefficients of species A and B, which may be written as12D K 1 3 dV , (9)where V is the average molecular speed of species A or B .
Q14. What is the way to achieve a higher sensitivity with a reasonable response time?
To achieve a higher sensitivity with a reasonable response time, the authors propose introducing periodic openings along the sensing fiber.
Q15. What is the diffusion coefficient of acetylene in the continuum state?
The diffusion coefficient of acetylene in air in the continuum state is 0.17774 cm2 s 1,10 and the corrected diffusion coefficient in the innermost air-hole column Fig. 1b is 0.163 cm2 s 1 8.3% decreasing .
Q16. What is the effect of the openings on the response time of the PCF?
From the analysis in Section 4 the authors conclude that the response time of PCF is limited by the time taken for acetylene gas to diffuse into the holes.
Q17. What is the sensitivity of a sensing PCF?
Figure 9a shows an example of a sensor design based on Crystal Fiber’s 1.7- mdiameter silica core PCF where the sensing PCF with periodic openings is connected to single-mode transmission fibers at the two ends.
Q18. What is the relative sensitivity of the Lucent PCF?
The relative sensitivity of Lucent’s PCF with 1.4- m-diameter d air holes and 1.55- m holes of separation as a function of wavelength is shown in Fig.