Frequency response of a polarization-maintaining optical fiber interferometer for simultaneous measurement of strain and temperature

摘要

Two different demodulation schemes, heterodyne and passive homodyne, were used to determine the frequency response of a polarization-maintaining (PM) optical fiber Mach-Zehnder interferometer for simultaneous measurement of axial strain and temperature. A symmetric 3 by 3 coupler was used to construct the passive homodyne configuration. The heterodyne setup consisted of two acousto-optically modulated lightwaves combined in a 2 by 1 PM fiber coupler. The intensity output of the coupler was demodulated using a digital lock- in amplifier. For a sensing fiber length of 0.54 meters, the frequency response to an axial load was flat up to 2 kHz. A simple rigid rod model of the fiber was developed to estimate the dynamic response.