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Lasers for NDIR Gas Detection

Optical Fiber Gas Sensor Source Lasers

Using the NDIR Gas Detection technique, lasers with wavelengths at the absorption bands of the gases can be used to monitor the presence and concentration of gases.

Gas sensing lasers (using NDIR) can measure low concentrations very accurately because their bandwidth is narrow (because they are lasers) and they measure only at the center of the absorption band.

If you are having difficulty accurately measuring the gases listed below, then this could be the solution for you. An InGaAs detector is used for measuring the changes in the laser signal (lower signal means more, higher signal means less of the gas you are measuring).

Wavelengths Available for Gas Sensing

Below is the list of the gases and the laser wavelengths used to detect them:

Gas Description Absorption Line Chip Structure Package Option
HF Hydrogen Fluoride 1268.7nm, 1278nm, 1273nm DFB TO-39/BF 14
H2O Water 1368nm, 1392nm, 1800nm DFB TO-39/BF 14
NH3 Ammonia 1512.2nm DFB TO-39/BF 14
C2H2 Acetylene 1532.68nm DFB TO-39/BF 14
CO Carbon Monoxide 1567nm, 2332nm (Under development) DFB TO-39/BF 14
H2S Hydrogen Sulfide 1576nm, 1578nm, 1590nm DFB TO-39/BF 14
CO2 Carbon Dioxide 1580nm, 1998nm, 2004nm DFB TO-39/BF 14
C2H4 Ethylene 1620nm, 1627nm DFB TO-39/BF 14
CH4 Methane 1647nm, 1650.9nm, 1653.7nm, 1660nm DFB  TO-39/BF 14
C2H6 Ethane 1683nm, 1685nm DFB TO-39/BF 14

DFB - A distributed feedback laser (DFB) is a type of laser diode, quantum cascade laser or optical fiber laser where the active region of the device is periodically structured as a diffraction grating. The structure builds a one-dimensional interference grating (Bragg scattering) and the grating provides optical feedback for the laser. DFB fiber lasers are often used in sensing applications where extreme narrow line width is required.