Based on the fabrication of 2×2 fused tapered couplers,the effects of the speed of drawing the biconical taper,the coupling length and the location of flame on the insertion loss(IL) and additional loss(AL) are analyzed in detail.It is shown that both IL and AL reach the lowest point when the pulling speed is 150 μm/s.In the range with a shorter drawn length,there is a linear relationship between IL and drawn length.When the flame height is 5.75 mm,the low-loss coupler can be fabricated. 更多还原