Highly sensitive fiber Bragg grating based gas sensor integrating polyaniline nanofiber for remote monitoring

Abstract

Optical fiber-based ammonia (NH3) sensors, such as fiber Bragg gratings (FBGs), have attracted significant attention owing to their involvement in different areas. Etched–tapered FBGs were fabricated and studied to detect NH3 leaks at room temperature for real-time remote monitoring over 3 km by using an erbium-doped fiber amplifier (EDFA). First, the two FBGs were chemically etched to obtain a thickness of 50 µm. Etched areas were then tapered to waist diameters of 15 and 30 µm by using the Vytran glass processing system workstation (GPX3000, USA). The use of etched–tapered FBG sensors for the real-time monitoring of NH3 is yet to be considered. A thin layer of polyaniline nanofibers (PANI) was deposited on FBGs to enhance their sensing characteristics when exposed to different concentrations of NH3 by using the drop-cast method. The sensing process was based on a shift in the Bragg wavelength due to NH3 exposure because of the PANI refractive index modification upon exposure to NH3. The developed FBGs were stable, sensitive, and repeatable and exhibited a linear response. The sensor with the smallest waist diameter (i.e., 15 µm) exhibited superior reaction with the highest sensitivity towards NH3. The developed setup was easily incorporated with well-established optical fiber networks, such as Fiber To The Home (FTTH). The setup can be utilized to fill double roles, i.e., transmission of data and sensing the variations in gas concentrations.