Ppb-level methane detection sensitivity based on a homemade Raman fiber amplifier and differential photoacoustic technology

A high-power near-infrared wavelength-modulated differential photoacoustic spectroscopy sensor for parts-per-billion (ppb) level methane detection is reported by using a homemade Raman fiber optical amplifier. A commercial 1653.7 nm continuous wave distributed feedback laser is employed as a seed source to excite a high light power of ∼550mW, which greatly improves sensor performance. Wavelength modulation spectroscopy and differential techniques are applied to further improve the signal-to-noise ratio of the photoacoustic signal. A 1 σ minimum detection limit of ∼10ppb for methane detection is achieved with an integration time of 10 s.