Piezoelectric Resonance Temperature Sensor for Active Fibers
A novel method for temperature measurement of active fibers under conditions of
lasing and radiation amplification is introduced. This method allows determination of the longitudinal temperature distribution of active fibers at different optical pump powers. A piezoelectric resonator made of the quartz crystal in the form of a hollow cylinder is used as a temperature sensor. Investigated segment of the active fiber is put thorough the hole of the resonator. Heating temperature of the resonator is determined by measuring a frequency shift of the piezoelectric resonance, which is preliminary calibrated under uniform heating conditions. In order to evaluate the heating temperature of the investigated fiber segment, the last one was substituted with a copper wire coated with polymer. A copper wire was heated by transmitting an electric current and its temperature was determined by measuring the resistance change. Numerical simulations revealed that the heating temperatures of the active and copper fibers differ by less than 9% at 11 W/m thermal load level. Heat transfer coefficient was evaluated using cooling kinetics and stationary state temperature of the ”copper” fiber. Heating temperature of the active fiber of the ytterbium fiber laser was measured at different pump levels (up to 150W).
Keywords: optical fiber, active fiber heating, fiber laser, temperature sensor, piezoelectric resonance
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