Adhesive-free bonding homogenous fused-silica Fabry–Perot optical fiber low pressure sensor in harsh environments by CO2 laser welding

Abstract

Abstract In this paper, we present a high-sensitivity homogenous fused-silica low pressure sensor. It was constructed from the commercially available standard silica fiber, fused-silica diaphragm and ferrule through CO2 laser all-welding. A Fabry–Perot (FP) cavity was fully sealed between the ultra-thin fused-silica diaphragm and the ferrule end face, and the ultra-thin diaphragm acts as a pressure transducer. We proposed the laser heat conduction welding for the fused-silica diaphragm, and the laser deep penetration point welding for the fiber and the ferrule. So the monolithic structure fused-silica FP interference optical fiber sensor was achieved. The sensor has a vent hole between the fiber and the ferrule forming during the laser deep penetration point welding, which can effectively reduce temperature dependence. The sensor exhibits excellent stability and repeatability, extreme low temperature dependence with 0.025nm/ o C that is 1/76 of the theoretical value, a sensitivity of 5.15nm/kPa, and a resolution of 4.7Pa. With a monolithic fused-silica configuration, the adhesive-free bonding high-sensitivity fused-silica sensor is expected to be suitable for low pressure measurements in extreme harsh environments.