| 摘要 |
PURPOSE:A glass rod composed of a round core and an oval clad is inserted into a specific quartz tube and they are melted integrally, then drawn into a filament to enable inexpensive production of a constantly polarized fiber of good wave- polarization properties and low loss. CONSTITUTION:A glass rod having core 11 and clad 12 is prepared by a known method. At this time, the refractive index of the core 11 is kept higher than that of the clad 12. The resultant glass rod is abraded into an oval cross section of minor axis a and major axis b where the ellipticity is represented by the equation. A quartz tube 15 is coated on its inside by accumulation with a stress developer 14 and the above glass rod is inserted thereinto. They are integrated by heat melting and drawn into a filament. Since the thermal stress anisotropy which decide birefringence is controlled by the ellipticity of the abrased outside rod inserted into the quartz tube, constantly polarized fibers of good polarizability and low loss are produced with high reproducibility. |
