1530-437X (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/JSEN.2017.2686864, IEEE Sensors Journal > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract— This paper describes a novel coaxial cable Fabry- Perot resonator for sensing applications. The sensor is fabricated by creating two highly reflective mirrors in a coaxial cable. The device physics was discussed. The temperature response of the sensor was tested. The temperature measurement is achieved by monitoring the frequency shift of the reflection and transmission spectra as the temperature is increased linearly in steps of 5 °C from 35 °C to 80 °C. This sensor exhibited high temperature sensitivity and measurement resolution. The high quality factor of this sensor leads to high measurement resolution. Highest Q factor of 133 was recorded. It has been derived that the Q factor decreases as the frequency increases. Index Terms—Coaxial cable sensor, Fabry-Perot Resonator, Quality factor, Temperature measurement. I. INTRODUCTION PTICAL fiber sensing has been attracting many research interests for their broadband applications in the fields of chemistry, biology, biochemistry, petroleum industry, environment and medical care [1]. Optical fiber sensors have many advantages over the traditional electrical sensors such as compactness, high resolution, remote monitoring capability and most significantly their immunity to electromagnetic interference [2]. Waveguide mode sensing [3-5], surface plasmon resonance sensing [6,7], fiber Bragg grating (FBG) sensing [8,9], long period grating sensing [10] and Fabry-Perot Interferometric (FPI) sensing [11,12] are some optical sensing concepts. The most commonly used concept is FBG due to its versatile advantages like miniature size, great durability, long term stability and easy multiplexing [13]. FBG consists of many reflection points that reflect a particular wavelength of incident light and transmit all others. When subjected to strain or temperature the grating period changes and so a different wavelength is reflected which enables us to determine the Bragg wavelength variation [14]. Recently, there has been an Manuscript received XX XX, XXXX revised on XX XX, XXXX. This work was supported by the Missouri Research Foundation. Mohammed Farhan Ahmed and Jie Huang (jieh@mst.edu) are with the Department of Electrical and Computer Engineering, Missouri University of Science and Technology, Rolla, MO 65401 USA Ting Xue (xueting@tju.edu.cn) and Bin Wu are with College of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China. Bin Wu is with the State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China. increase of interest in using FBG’s in Structural Health Monitoring (SHM) [15]. Although with such high merits, optical fiber sensors have some limitations. They have small dynamic range due to the limited deformability of silica glass. Even with rigorous packing, fiber sensors can easily break down when subjected to large strains (about 0.4 mɛ or 0.4%) or a shear force, causing serious challenges for sensor installation and operation [16]. Consequently, the applications of optical fiber sensors are limited in heavy duty or large strain measurements which makes it difficult to be used in SHM. In recent years, people have been migrating ideas of the optical fiber to coaxial cable as they share the same electromagnetic theory. In comparison with optical fibers, the main merit of using coaxial cable is its ability to survive large strains (more than 2%) due to its large dimension. Likewise, coaxial cables are also insensitive to lateral force or bending. The FBG concept has been successfully implemented on coaxial cables. Coaxial cable Bragg grating (CCBG) was fabricated by drilling open holes at periodic distance along the coaxial cable. The periodic impedance discontinuities produce resonant peaks in both transmission and reflection spectra at discrete frequencies. This spectrum shifts whenever the CCBG is subjected to any physical change or have change in their material properties. To demonstrate the ability to use CCBG as a sensor, they also conducted strain measurements [17]. The large dynamic range, robustness and high resolution of CCBG sensor provides a very promising solution for the SHM [18, 19]. however, due to the long wavelength of the radio frequency, the CCBGs usually have a long grating length (~1 m) in comparison with FBGs (~1 cm), thus, the spatial resolution of CCBG is limited. A promising solution for the high spatial resolution problem of coaxial cable sensors is inspired by the optical Fabry-Perot resonator. FPRs typically have comparable sensitivity when compared to FBGs but for a much shorter length. FPR consists of two reflectors with a separation of hundreds of micrometers. Light waves reflected at the two reflectors have a different time delay, resulting in interference signal. When subjected to strain or temperature the physical length or material properties changes which lead to shifting in interference pattern [20-23]. This shift can then be used to determine the change in High Quality Factor Coaxial Cable Fabry-Perot Resonator for Sensing Applications Mohammed Farhan Ahmed, Ting Xue*, Bin Wu and Jie Huang* O