Optical Fiber Gas Sensor Source Lasers
NDIR Laser Diode Modules
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.