Taking advantages of the principle of optic absorption varied with methane concentration at its characteristic absorbent wavelength and differential absorption measurement

combining space division multiple access technology(SDMAT) and long optical path absorbent pool technology

and considering the circumstance characteristic of the coal mine

this paper proposes to adopt multiple gas absorption optic-fiber sensors to monitor methane concentration.After introducing the principle of optic-fiber sensor system for monitoring methane concentration in coal mine by differential infrared

this paper has presented the block diagram of the monitoring system.It is shown that the minimal detect limit of the sensor reaches 4.274 mg/m

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and that the precision and stability satisfy practical application.The instrument can be used for on-line measurement with multiple points on different spots.