Design of TR-EFPI fiber-optic pressure sensor for the medical application

Abstract

The conventional reflection-type extrinsic Fabry-Perot interferometric (EFPI) fiber optic sensor has good sensitivity and resolution compared with other types of fiber optic sensors. However, it has the disadvantage that the EFPI fiber optic sensor is difficult to know the direction of physical properties, because of the measurement method by only fringe counting. So, it is hard to use the practical measurement. But the total reflected extrinsic Fabry-Perot interferometric (TR-EFPI) fiber optic sensor can measure the direction of the physical properties without adding other mechanisms and complex signal process equipments. This paper presents the newly designed fiber optic pressure sensor using the TR-EFPI fiber optic sensor with a single mode fiber (SMF), and a micro fabricated diaphragm. The output signal of this type of fiber optic pressure sensor can be easily analyzed based on the spliced based model proposed by D. Marcuse and large deflection theory. Then, we can design the optimal length between the thin film of diaphragm and the end of single mode fiber. Therefore, we can know the relation between the deflection of thin film and applied pressure using the large deflection theory. From these analyses, the relation between the applied pressure and the output signal of TR-EFPI fiber optic sensor can be simulated. It means that we can design the TR-EFPI fiber optic pressure sensor measuring various conditions by changing the size of thin film. As the newly designed TR-EFPI fiber optic pressure sensor can be fabricated in small size and has good sensitivity, it can be applied to medical instrument like pressure sensor and force sensor for catheter and minimumally invasive surgery robot for safer surgery