Polarization extinction ratio in polarization maintaining fiber sealed with glass solder

The paper considers the effect of sealing with glass solder a pair of optical polarization maintaining fibers with an elliptical stress cladding on the value of the polarization extinction ratio. A variant with the placement of non-working fibers in the sealing area to create the symmetry of induced mechanical stresses is proposed. An experimental study of the contribution of the induced mechanical stresses on the value of the polarization extinction ratio has been performed. The assessment of temperature effect on the coefficient of polarization extinction in the place of sealing of optical polarization maintaining fibers has been made. Sealing of fibers in a metal tube was performed using a glass solder preform and an induction heater. Evaluation of the polarization extinction ratio was obtained by white-light interferometry using the scanning Michelson interferometer. The value of the polarization extinction ratio was measured on 4 samples with a length of working fibers of 4 meters. This experiment shows that creation of isometry structure in the area of sealing by addition of non-working fibers allows decreasing the polarization extinction ratio from 0.082 dB/K to 0.035 dB/K in the temperature range from –15 °C to +70 °C. This method allows the sealing of several fibers in one tube to reduce the size of the devices. The performed research can be useful in the development of optoelectronic devices where it is required to introduce optical birefringent fibers in a sealed housing.