Metal-based asymmetric plastic optical fiber couplers based on hollow waveguide and Y-Branch structures have been developed. Non-symmetrical coupling ratios were obtained by controlling the tap line width of the metal hollow waveguide whereas a simple attenuation technique based on lateral displacement of two fibers is used for the Y-branch. The asymmetric hollow waveguide coupler fabricated on metallic block shows a tap-off ratio or TOFR variation of 10.7% to 89.3%, for a tap width of 500 um to 1 mm. The asymmetric Y-branch design provide a range of coupling ratios from 14.23% to 85.77% for an output fiber lateral displacement of 0.1 mm to 4.4 mm. The excess loss of these devices varies from 9.49 dB to 11.51 dB for the asymmetric hollow coupler and 6.3 dB to 8.3 dB for the Y-branch coupler.
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