Fabrication and Characterization of Side-Hole Single-Mode Optical Fibers

The fabrication and characterization of side-hole single-mode optical fibers have been studied. Controlling the internal pressure of side holes in a preform made possible the fabrication of side-hole fibers with various core ellipticities and with a circular core. The relationship between theVcand the core ellipticity for side-hole fibers showed good agreement with that calculated for elliptical core fibers without side holes. The best transmission loss of the side-hole fibers with a circular core was 0.9 dB/km. A large birefringence of 2.3 × 10−4was also obtained in side-hole fibers with elliptical cores.