Development of a Methane-Detection System Using a Distributed Feedback Laser Diode and Hollow-Core Photonic Crystal Fiber.

A highly integrated methane-detection system was experimentally established by using a distributed feedback laser diode and hollow-core photonic crystal fiber. The self-developed circuits with a laser diode and essential optical devices were integrated into an instrument that generated a modulated optical signal in a fiber-coupled gas cell that contained the hollow-core photonic crystal fiber. The instrument could also process the return optical signal that contained the gas concentration information. The experiments demonstrated the good performance of the developed system. In the spectrum tests, the center wavelength of the laser diode could be tuned linearly by controlling the laser's working temperature and driving current. The second harmonic signal could be extracted in order to reflect the gas concentration. According to the Allan deviation method, the low limit of detection of the system was determined to be 29.52 ppm. In addition, a long-term stability test demonstrated that the system has a good stable performance. The proposed system can be further optimized in order to be applied in paddy fields to detect and monitor the methane concentration in a large area by using the optical fibers. [ABSTRACT FROM AUTHOR]