CH 4 , C 2 H 4 , and C 2 H 6 Sensing by Fiber‐Enhanced Raman Spectroscopy

ABSTRACT This study investigates a fiber‐enhanced Raman gas sensor operating under pressurized conditions, which employs a 5‐m‐long nodeless hollow‐core anti‐resonant fiber (HC‐ARF). The system utilizes a 25‐μm core‐diameter optical fiber coupled with a charge‐coupled device (CCD) for spatial filtering. Under normal atmospheric pressure conditions and with an exposure time of 300 s, the system successfully detects atmospheric CH 4 and 13 C 16 O 2 . By increasing the gas pressure inside the HC‐ARF, it was observed that the Raman signal intensity was enhanced while the background noise remained unchanged. Under the conditions of an output power of 1.6 W, an integration time of 300 s, and an atmospheric pressure of 10 bar, the detection limits based on a 5‐m‐long HC‐ARF were determined to be 60 ppb for CH 4 , 130 ppb for C 2 H 6 , and 92 ppb for C 2 H 4 , respectively. Simultaneously, as the pressure increased, the gas filling rate of the gas sensor was also enhanced. At an atmospheric pressure of 10 bar, CH 4 filled the entire 5‐m‐long HC‐ARF within 4 s. These achievements have paved the way for developing portable gas sensors with low detection limits and rapid response times, thereby making the monitoring of trace gases feasible.