Low-cost miniature fiber optic extrinsic fabry-perot interferometric sensor for cardiovascular pressure measurement

Summary form only given. The measurement of cardiovascular blood pressure through a catheter has a big impact for monitoring physical parameters of critical patients. Fiber optics provides a valuable alternative to traditional sensing technologies, whereas small size, high performance and MRI compatibility are key advantages . Size plays a fundamental role in the choice of sensing probe; by reducing probe dimensions it is possible to reduce the invasiveness or improve the form factor of the probe, extending sensing capability. In this paper, we present a fiber optic extrinsic Fabry-Perot interferometer (EFPI) sensing system, based on a fully biocompatible design, with miniature 0.22 mm diameter and white-light interrogation. The sensing probe is built on a whole glass structure on the tip of the transmission fiber, making the design epoxy-free and compatible with biomedical application. The Fabry-Perot cavity is obtained by splicing the single-mode transmission fiber to a capillary that seals the structure, and then to a multimode fiber serving as diaphragm. After λ/20 polishing, the diaphragm is conveniently optimized by etching the fiber tip with 48% hydrofluoric acid, with an etching rate of 1.4 μm/min, achieving a typical sensitivity of 5-10 nm/kPa. In order to minimize probe cost, the EFPI sensor is designed for 1550 nm window operation, using 10/125 and 62.5/200 μm fibers sealed in a 200/220 μm capillary; the structure can be rescaled to further reduce probe si%e, also changing the operative wavelength window.