Fused fiber couplers wavelength-flattened by arc discharge

A novel method is proposed to provide wavelength-flattened coupling for fused fiber couplers. The coupling regions of fused fiber couplers are heated unequally by arc discharge, and then are cooled rapidly. The unequal heating generates the unbalance index changes in two identical fibers constituting the fused fiber couplers, and brings about the phase mismatch between the fibers. The phase mismatch results in the wavelength-flattened response.