Fiber ring laser sensor based on hollow-core photonic crystal fiber

•Hollow-core photonic crystal fiber is applied to an intra-cavity fiber laser sensor.•Wavelength sweep technique is introduced into the sensing system for high precision.•Important parameters of the system are theoretically and experimentally investigated.•A minimum detectable acetylene concentration of 5.4 ppm has been measured.

We report an erbium-doped fiber ring laser intra-cavity sensor. Hollow-core photonic crystal fiber (HC-PCF) used as the gas absorption chamber is introduced into the laser cavity. When the HC-PCF is filled with gas, its absorption attenuation changes the cavity loss and the laser output. We use a modular NI PXI platform equipped with a programmable voltage and current source and a LabVIEW program to generate driving voltage for the tunable optical filter (TOF) to ensure high precision. The relationship between the concentrations of acetylene, coupling ratios, pump power and output power is theoretically and experimentally investigated. Different output spectra are measured by the optical spectral analyzer (OSA). A minimum detectable acetylene concentration (MDAC) of 5.4 ppm has been experimentally achieved.