A novel Y branch waveguide structure is presented, in which a transitional guide is embedded between an incident channel and an output branch. The transitional guide is used to improve the mode field matching between both the waves supported by the incident and output waveguides. A numerical simulation shows that this geometry can minimize the branching loss to about 0.041 dB at 1.31 μm and 0.052 dB at 1.55 μm wavelength respectively. The samples of this type SiO 2 branch waveguide are fabricated by the chemical vapor deposition technology. The measurement on the samples gives the good results of about 0.08 dB and 0.09 dB branching loss at 1.31 μm and 1.55 μm wavelengths respectively.