To obtain excellent performance optical fiber couplers, the structural difference of SiO2 in couplers with differ-ent manufacturing techniques was investigated. With 7402FT2IR infrared spectrometric analyzer, the infrared absorption spectrum of SiO2 in couplers at different drawing velocities was measured, and two characteristic peaks in the wavenumber range of 650 2000 cm-1 were observed. One characteristic peak is at about 943 cm-1, which is attributed to Si-O-Si bond asymmetric stretching vibration, the other is at about 773 cm-1, which is attributed to Si-O-Si bond symmetric stretching vibration. From the infrared spectrum, it is found that the intensity and wavenumber of the characteristic peaks are related to the manufacturing technique of couplers. The characteristic peak at about 943 cm-1 becomes steeper when increasing the drawing velocity. At the drawing velocity of 150μm/s, the distance between the two characteristic peaks is maximum, and then the optical fiber coupler has excellent performance, indicating that the performance of the optical fiber coupler has a close relationship with the wavenumber of the two characteristic peaks.