Fused Fiber Couplers Made Wavelength Insensitive by the Glass Structure Change

In this paper, a method based on the glass structure change is proposed to make fused fiber couplers wavelength insensitive. After fused fiber couplers are fabricated, the coupling regions are heated unequally by arc discharge. The glass structure change induced by arc discharge generates unbalance index changes in the two identical fibers constituting the fused fiber couplers, and brings about the phase mismatch between the fibers. The phase mismatch results in the wavelength-insensitive response. The proposed method was applied to wavelength-flattening fused fiber couplers with different cross-sectional shapes, and it has become clear that the method is effective for the reduction of the wavelength dependence.