High Temperature-Pressure Metalized Optical Fiber Dual FP Sensor With Welding Encapsulation

Optic fiber measurement technology has been widely used to obtain multiparameters in severe environments, such as high-temperature and high-pressure steam pipelines. This study develops a novel optic fiber sensor with dual Fabry-Perot (FP) cavities to improve the efficiency of simultaneously measuring temperature and pressure. The sensor incorporates fiber metallization and laser welding to enhance the package capability. The dual FP fiber in the sensor is fused from single-mode fiber (SMF) and hollow core fiber (HCF). The end of SMF connects the head of HCF and forms the dual FP cavities, which exhibit distinct temperature and pressure responses through a temperature self-decoupling process and realizing simultaneous temperature and pressure measurements. Furthermore, the sensor package methods are experimentally investigated: laser welding provides excellent stability at high temperatures compared with glue adhesive and soldering fixation. Finally, the sensor measurement experiments show the temperature sensitivities of the two FP cavities were 22.28 pm/°C and 59.56 pm/°C in the range of
$20~^{\circ }$
C
$\sim 400~^{\circ }$
C, respectively. The pressure sensitivities were −273.12 and −3730.26 pm/MPa in the range of
$0\sim 10$
MPa, respectively. The maximum error of the dynamic experiments for the designed sensors was 6.86%, and the trend was the same as that of the commercial sensors. These results are of great significance in providing feasibility and accuracy sensors for equipment simultaneous multiparameter measurements.