Investigations of processing parameters of thermal poling optical fibers using an in situ testing system

In order to investigate the effects of processing parameters in thermal poling, an in situ testing system used for thermal poling optical fibers was constructed with an all polarization maintaining fiber Mach-Zehnder interferometer. The in situ monitoring of the thermal poling process was done to investigate the effects of processing parameters in thermal poling, such as poling ambient temperature, applied poling voltage and poling duration, on the linear electrooptic coefficient induced in the optical fiber. Experiments of the in situ monitoring showed that the stronger the electric field in the fiber core was, the higher linear electrooptic coefficient induced in the fiber core could be. But the electrical breakdown of dielectric medium between electrodes limits the maximum applied poling voltage. Considering the limit of electrical breakdown of the structure of side polished fiber, the voltage of 3000 volts could be applied during thermal poling. When a voltage of 3000 volts applied on the device with side polished fiber, the optimum poling duration is about 16 minutes and the optimum ambient temperature for thermal poling is about 190°C. The in situ testing system could also be used for the in situ monitoring of manufacture of thermal poling optical fiber so as to improve the efficiency of manufacture.