Performance of Hollow-Core Photonic Crystal Fiber-Based Trace C2H2 Detection System

In this article, we propose an optical sensor system utilizing the capabilities of hollow-core photonic crystal fiber (HC-PCF) to transmit excitation light and hold sample gas. The direct absorption response is examined for different modulation waveforms, pressures, frequencies, and concentrations. The experimental results show that the response signal has an obvious overshoot and spike. The overshoot and spike are more obvious under the sine modulation than the rectangular modulation. In the 1-500-Hz range, the system demonstrated optimum response characteristics at 5 Hz, corresponding to the maximum attenuation percentage. Furthermore, a positive correlation was observed between the attenuation percentage of light intensity (A(t)) and optical power (A(p)) with the pressure in the gas chamber within the range of 0.1-0.3 MPa. When the gas chamber is filled with 10000-ppm C2H2/N-2 to 0.3 MPa, At and Ap are 47.98% and 22.73%, respectively. A good linear relationship exists between the attenuation value of photodetector (PD) output and target gas concentration with a correlation coefficient above 0.99 after 140 s. The theoretical minimum detection limit of C2H2 without the erbium-doped fiber amplifier (EDFA) is 49.28 ppm and the relative synthetic standard uncertainty is 3.35%. This article provides an idea for applying the HC-PCF-based gas sensing system.