A novel fibre-optic system for methane detection

A Method for the Measurement of Methane Gas Based on Multi-beam Interferometry

“…On the other hand, in order to enhance the minimal detectable gas concentration, the most straight forward way is to use a gas cell with a long interactive cavity length. However, there is a tradeoff between the real implementation and the measurement accuracy for the gas sensor system [10].…”

“…Assuming the absorption coefficient of the methane at wavelength of 1655 nm is 15 m -1 [10], the simulation of the normalized transition light is shown in Fig. 2.…”

“…Fiber-optic gas sensors for the air pollution and noxious and explosive gases are mostly based on monitoring the optical power attenuation induced by the gas molecule's absorption. The Beer-Lambert Law can be expressed as [10] Where 0 ( ) I λ is the output optical power when the methane gas concentration is zero, ( ) I λ is the optical power of the light passing through the gas, L is the length of the gas cell, C is the gas concentration, Z is the length of the optical path, and ( ) a λ is the absorption coefficient of the gas.…”

“…The guide light is absorbed with the increase of the concentration of the methane. The spectroscopic absorption technique is beneficial due to its ability to eliminate the influences of dispersion, perturbation of gas, and the transmission loss caused by dust, water vapor, and connectors, etc [10]. However, some of methods suffered from low system sensitivity and poor mechanical stability, some other methods are too expensive because they use some special devices such as laser diodes with a typical spectral width less than 1 MHz.…”