A numerical simulation of a near-infrared three-channel trace ammonia detection system using hollow core photonic crystal fiber

A simulation model of the fiber-structure trace ammonia detection system based on near-infrared laser absorption spectroscopy is proposed. The distributed feed-back (DFB) diode laser modulation, photodetector, and signal processing are simulated by programming using matlab code while the noise amplitude selected to the sampling accuracy of commercial 12-bit ADC. The wavelength 1512 nm was selected to calculate the absorption coefficient of mixture containing ammonia, carbon dioxide, and water vapor. When the length of fiber-structure gas chamber was set to 10 cm, 1 m, and 10 m, respectively, ammonia with concentration from 0.2 ppm to 10,060 ppm can be detected. The dynamic range of this simulation have covered 5 orders of magnitude which never achieves in traditional detection system. Our work provides a potentially valuable option to establish the ammonia detection system of more portable, high sensitivity, and large detection range.