Simultaneous Measurement of Strain and Temperature Using Optical Fiber Sensors: Two Novel Configuration

This paper presents two configurations of optical fiber sensors, that can simultaneously measure both the axial strain and temperature. The first configuration is composed of a 50µm In-Line Fiber Etalon (ILFE) cascaded with a 75µm Intrinsic Fabry-Perot (IFP) sensor to form a lead in-sensitive, localized, 125µm gage-length dual parameter sensor. The sensor response from this configurations is interrogated using coherence division multiplexing based on white light interferometry, and using psuedo-heterodyning demodulation. The second configuration is composed of an ILFE cavity and an in-fiber Bragg grating. This sensor is interrogated using two low-coherence sources, white light interferometry, psuedo-heterodying demodulation and spectral methods. The results obtained in a simultaneously varying temperature and strain field by the fiber sensor are compared with a semiconductor temperature gage and a resistive foil gage, and show excellent correlation.