Polarization-maintaining optical fiber for coupler fabrication

Abstract From the Canadian patent

Polarization-maintaining coupler is made by a biconically-tapered-fused process from two short lengths of an optical fiber, each having a small, oval stress-applying region that substantially contacts the core. The area of the stress-applying region of the optical fiber is less than 10 percent, preferably less than 2 percent that of the optical, fiber and preferably is contiguous with the core. Couplers of highest quality are made from quartz glass fibers having a birefringence between 1 and 3 x 10-4. It is believed that the principal axes of the oval stress-applying regions of those couplers of highest quality have been collinear or parallel. To permit a coupler to be handled, it can be …