A new all-fiber fused taper polarization couplers

All-fiber fused-taper polarization couplers with a package size of only 30 mm (length)×3 mm (diameter) have been fabricated with the conventional single-mode fiber. With unpolarized light exciting the input port of the device, the polarizing extinction ratios that are measured directly at both output ports are better than 20 dB. It is shown that this device can actually split two orthogonally polarized modes; in other words, this device performs as an all-fiber polarization beamsplitter. With the x- or y-polarized light exciting the input port of the device, the spectral response of the polarization splitting of both output ports was measured. The results show that this device performs as both a polarization coupler with a series of 3-dB splitting ratios and as a polarization wavelength division multiplexer