Diaphragm-based Extrinsic Fabry-Perot Interferometric optical fiber pressure sensor

A new structure of diaphragm-based extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor is presented. A double holes silica ferrule with 1.8mm outside diameter is used to align the fiber. The Fabry-Perot (F-P) cavity is formed between the fiber end facet and inner surface of the diaphragm. The diaphragm is attached to the top of ferrule by carbon dioxide (CO2) laser thermal fusion bonding system. One hole of ferrule is used to align the fiber to the diaphragm and the other is used to balance the pressure inside and outside of F-P cavity. The diameter of the sensor head is only 1.8mm. In the pressure measurement, the pressure sensitivity of this sensor is about 25.89nm/KPa and the temperature dependence is approximately 6nm/degrees C. The sensor has a linear response in the range from 0 to 3KPa. This structure of sensor can eliminate the thermally induced inner pressure changes of F-P cavity. Furthermore, the sensor with the temperature compensate can be used to detect the liquid level. The fabrication of this kind sensor is simple and low cost. And the advantages of this sensor are high sensitivity, immune to electromagnetic interference (EMI) and high temperature resistance.