A Novel Fabrication Method for All-Fiber, Weakly Fused, Polarization Beamsplitters

A simple method for fabricating single-mode fused couplers for polarization beamsplitting is presented. The coupler is extremely weakly fused such that the first polarization modulation waist in its power transfer characteristic is clearly extended. Due to such a feature, the coupler drawing process may accurately be stopped at the waist point by simply monitoring the power variations of the output ports. We have achieved an average extinction ratio of - 23.7 dB at the throughput port and - 23.8 dB at the coupled port at the designated wavelength. The polarization bandwidth obtained is 38 nm.