A new system on transient temperature measurement with a Mach-Zehnder interferometer employing Polarization Maintaining Fibers (PMF) has been successfully developed. Two PMF fibers, one as the reference arm that avoids externally added disturbances and another as the sensor arm that monitors temperature change, are employed. When temperature changes, the length and phase constant of the sensor arm changes, resulting in a phase difference at the mixing point of two optical waves after passing through both arms, forming interference fringes of concentric circles that move quickly in a radial direction. This system enables us to measure the transient state of temperature change with a resolution of (6/1000)°C and time resolution of 0.1 s.
